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1
Нгуен, Ван Зионг, e Александр Витальевич Белогуб. "ОПРЕДЕЛЕНИЕ ГРАНИЧНЫХ УСЛОВИЙ ДЛЯ РАСЧЁТА ТЕРМОНАПРЯЖЕННОГО СОСТОЯНИЯ ПОРШНЯ". Aerospace technic and technology, n. 1 (7 marzo 2019): 39–47. http://dx.doi.org/10.32620/aktt.2019.1.04.
Testo completoAbstract (sommario):
The paper deals with the study of the influence of the working process parameters of the two-stroke opposed piston engine like D100 (20.7/2×25.4), especially the heat exchange between the working substance and the wall of the combustion chamber (CC) – cylinder and pistons on temperature and stress-strain state of the piston. To make an estimation of the effect of a working process on the boundary condition we considered the internal heat balance and specific features of gas dynamic loading of main parts of the cylinder-piston group. To calculate the temperature fields, the actual boundary conditions of non-stationary thermal loading were replaced with the equivalent steady-state ones, obtained from the condition that the amount of heat perceived by the piston surface in real and conditionally equivalent processes are equal. Equivalent parameters of heat transfer are calculated by the condition of conservation of the amount of heat passing through the walls of the CS. It was performed the validation of the calculation of equivalent heat exchange parameters. It is shown that in case of an error in specifying the initial conditions, for example, temperature per 100K, the temperature of the piston CC surface may change by 5K in the first 5 operating cycles. It is shown that the developed model of the workflow can be adjusted according to the available experimental data and used to model the boundary conditions. The authors made corrections to the dependence obtained by prof. Rosenblit, to determine the current heat transfer coefficient from the working fluid to the walls of the CC by the total heat removal for the cycle, equal to 20%. It was obtained the average coefficient of heat transfers from the working fluid to the piston and the temperature of the cycle for the nominal mode, which are 3500 W/(m2•K) and 835 K respectively. It was carried out the simulation of the thermal properties of the gap between the piston ring and the groove filled with combustion products. It is shown that the conditions of heat transfer through annular grooves and rings require clarification in modeling, which is associated with the conditions of heat transfer in the gaps, and the gap can be replaced by a gasket with appropriate thermal properties.
2
Xu, Zhao Ping, e Si Qin Chang. "Simulation of an Opposed-Piston Four-Stroke Free-Piston Generator". Applied Mechanics and Materials 336-338 (luglio 2013): 585–89. http://dx.doi.org/10.4028/www.scientific.net/amm.336-338.585.
Testo completoAbstract (sommario):
In order to achieve efficient conversion of the chemical energy of fuel into the electrical energy, a novel opposed-piston four-stroke free-piston generator is developed in this paper by equipping one free-piston engine with two linear generators. Mathematical models of the opposed-piston four-stroke free-piston generator are created based on the kinetic equation of the free-piston motion, the state equation of the ideal gas, and an equivalent heat release function of the combustion process. Dynamical properties of the system are simulated and analyzed by using the created model, and results from the simulation are presented. According to the simulation, the new four-stroke free-piston generator can realize running without vibrations.
3
Quan, Lingxiao, Haihai Gao, Changhong Guo e Shichao Che. "Assessment of the Dynamics Flow Field of Port Plate Pair of an Axial Piston Pump". Processes 8, n. 1 (8 gennaio 2020): 86. http://dx.doi.org/10.3390/pr8010086.
Testo completoAbstract (sommario):
This paper aims at studying the dynamic fluid evolution process of port plate pair of an axial piston pump. First of all, The Renormalization Group k-ε model (RNG k-ε model) is implemented to simulate the dynamic flow distribution and forecast the evolution of the internal vortex structure inside the valve plate chamber with different speeds of pistons and velocities of inlet fluid by using computational fluid dynamics software. Then, an equivalent amplification test model of a piston-valve plate is built up based on Reynolds similarity theory; the flow state of the piston-valve plate flow field is observed applied the particle image velocimetry (PIV) measuring technique. The resulting uniformity of numerical simulation and PIV measurement verifies that the RNG k-ε model can achieve high-precision prediction for the vortex structure inside the valve plate chamber. Through analysis of velocity contours and streamlines of the flow field, it can be found that vortices with different scales, strengths and positions will occur during the process of fluid distribution, and the scale and strength of the vortex inside the valve plate chamber will be reduced with the increase of the piston’s moving speed, so the energy loss is also reduced and the efficiency is improved.
4
Guan, Dong, Li Jing, Harry H. Hilton e Junjie Gong. "Dynamic lubrication analysis for a spherical pump". Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 233, n. 1 (28 febbraio 2018): 18–29. http://dx.doi.org/10.1177/1350650118762603.
Testo completoAbstract (sommario):
Dynamic lubrication analyses for a spherical pump, consisting of a piston and cylinder, are presented. Contact forces between piston and cylinder are modeled first using an equivalent ball-on-plane model. Both the effects of external loads and operating conditions are considered in a dynamic elastohydrodynamic lubrication model, which is derived from Reynolds equation. Two assumed time-dependent sine-wave and square-wave loads are applied to the model. Fluid film thicknesses are estimated using the model and assumed loads, effects of different structural, and operational parameters, such as piston diameter, radial clearance, applied load, piston speed, lubricant viscosity, and surface roughness, on fluid film thickness are investigated. Fluid film thickness reactions of more realistic smooth and continuous sine wave loads are compared to discontinuous ones in order to verify whether or not assumed ideal loads are acceptable and reliable. Results indicate that piston diameter, speed, lubricant viscosity have positive relations on the dynamic lubrication performance, and increasing these values can improve the dynamic lubrication regime. While the parameters such as radial clearance, applied load, and surface roughness have the verse effects. Furthermore, the impacts of all the above parameters on fluid film are different either. These obtained results can be used to effectively optimize spherical pump lubrication performance.
5
Ding, Fa Jun. "Piston Engine Connecting Rod Transient Dynamic Finite Element Analysis and Maintenance Strategy". Applied Mechanics and Materials 484-485 (gennaio 2014): 272–76. http://dx.doi.org/10.4028/www.scientific.net/amm.484-485.272.
Testo completoAbstract (sommario):
Connecting rod is the very important connection and force bearing parts of piston engine crank mechanism; work in the role of various kinds of alternating stress. Taking a general rod from Lycoming IO-360-A1B6 aero-piston engine as the analysis object, first, a 3-D finite element model of the rod is established in ANSYS Workbench. And then, considering the influence of gas pressure in cylinder after ignition acting on the connecting rod under engines rated speed conditions, through the transient dynamic analysis, find in all load steps, the maximum equivalent stress occurred at the transition zone between the shaft and little head, and received the maximum equivalent stress versus time curve, to provide numerical basis for improving high-cycle fatigue reliability of the rod. Finally, according to equivalent stress contours of the rod when gas in cylinder peak pressure occurs, initially identified rods hazardous areas,to provide foundation for the development of standard repair process.
6
Zhang, Ziwei, Huihua Feng e Zhengxing Zuo. "Numerical Investigation of a Free-Piston Hydrogen-Gasoline Engine Linear Generator". Energies 13, n. 18 (9 settembre 2020): 4685. http://dx.doi.org/10.3390/en13184685.
Testo completoAbstract (sommario):
The free-piston engine linear generator (FPELG) is being investigated by many researchers because of its high thermal efficiency and its variable compression ratio. However, all researchers focused on the FPELG characteristics with mono-fuel. Therefore, in this paper, the performance of the FPELG that has adopted gasoline with hydrogen as fuel is investigated. The method of coupling the zero-dimensional dynamics model with the multi-dimensional CFD (Computational Fluid Dynamics) combustion model was applied during the simulation process. According to the results, the piston TDC (Top Dead Center), the piston peak piston velocity, and the system operation frequency show a negative correlation with the increase of hydrogen fractions. However, the peak in-cylinder pressure was increased with the hydrogen volume fraction increase, due to the fast flame speed and short combustion duration characteristics of hydrogen. Meanwhile, the indicated efficiency of the free-piston engine was increased from 32.3% to 35.3% with the hydrogen volume fraction change from 0% to 4.5%, when the free-piston engine operates at stoichiometric conditions with fixed ignition timing. In addition, with the ignition timing advance increase, the piston TDC was decreased. The peak piston velocity and the peak in-cylinder pressure were in negative correlation with the ignition timing advance. While the engine indicated that the efficiency was increased with the equivalent degree of ignition timing from 20° to 16°. Therefore, the ignition timing of the FPELG under the spark-ignition combustion mode is supposed to be an effective and practical control variable.
7
Nakai, H., N. Ino e H. Hashimoto. "Effects of Film Temperature on Piston-Ring Lubrication for Refrigeration Compressors Considering Surface Roughness". Journal of Tribology 120, n. 2 (1 aprile 1998): 252–58. http://dx.doi.org/10.1115/1.2834419.
Testo completoAbstract (sommario):
This paper describes a theoretical model for piston-ring lubrication considering the combined effects of surface roughness and oil film temperature variation for refrigeration compressors. In the model, the piston-ring is treated as a one-dimensional dynamically loaded bearing with combined sliding and squeezing motion. The one-dimensional modified Reynolds equation, based on the average flow model by Patir and Cheng, is used to determine the pressure distribution, and the one-dimensional energy equation, considering the heat generated due to contact of asperities, is applied to calculate the oil film temperature distribution. In the analysis of the modified Reynolds equation, the flooded condition and Reynolds condition are employed at the leading edge and trailing edge of piston-ring, respectively. On the other hand, in the analysis of the modified energy equation, a constant temperature equivalent to the cylinder wall temperature is assumed at the leading edge. From numerical results of the minimum film thickness, pressure and temperature distributions and friction force, the combined effects of surface roughness and oil film temperature variation on these lubrication characteristics are clarified.
8
Yuan, Chenheng, Jing Xu e Huihua Feng. "In-cylinder heat transfer and gas motion of a free-piston diesel engine generator". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 231, n. 8 (28 giugno 2017): 739–52. http://dx.doi.org/10.1177/0957650917717627.
Testo completoAbstract (sommario):
The free-piston engine generator is an attractive alternative to the conventional reciprocating engine due to the feature that it moves without crankshaft system. This paper presented a simulation for the investigation on the characteristic of in-cylinder gas motion and heat transfer in a compression ignited free-piston engine generator. An operation experiment was performed to obtain the precise piston motion for the modeling of heat transfer and gas flow. The development of the multi-dimensional model was described, and simulation results were presented and showed good similarity with the experimental data. Then, the heat transfer and gas motion in the free-piston engine generator were discussed, on which the influences of piston motion were also investigated compared with a corresponding conventional reciprocating engine. The results indicated that compared with the conventional reciprocating engine, a higher level of squish and reverse squish effect was found for the free-piston engine generator due to its faster motion around top dead center, while its slower piston motion led to weaker gas turbulence in the compression process. Moreover, the free-piston engine generator and conventional reciprocating engine did not show a significant difference in heat transfer during the compression process, however, an obvious advantage of heat transfer was indicated for the free-piston engine generator in combustion and expansion processes due to its lower combustion temperature and the reduced time that is available for heat transfer caused by its faster expansion. The mechanism for such differences is that the free-piston engine generator moves with uneven equivalent speed.
9
Li, Zekui, Shunhai Xu, Guofang Gong, Yankun Bi, Liping Xu, Liang Zhang e Zhen Ren. "Study on Friction Characteristics of Slipper Pair of Large Displacement High-Pressure Piston Pump". Lubricants 10, n. 12 (15 dicembre 2022): 363. http://dx.doi.org/10.3390/lubricants10120363.
Testo completoAbstract (sommario):
The reference value of the oil film thickness and friction coefficient of the slipper pair is critical to the development of the piston pump, especially for 750 mL/r displacement piston pumps. To explore the computing method and range of the reference value mentioned applicable to 750 mL/r displacement piston pumps, this study aims to propose the modified calculation model of the oil film thickness based on the real clearance flowrate and obtain the value range of the friction coefficient of the slipper pair. Through the friction test of the slipper pair, the mean deviation ratio of the oil film thickness between the modified value, theoretical value, and the measured value was calculated and compared, respectively. The variation law of the friction under the influence of different speeds and working pressures was analyzed. Finally, the range of the equivalent friction coefficient with the upper and lower limit surfaces was obtained. The results show that the mean deviation ratio between the modified oil film thickness value and the measured value is mainly within 6%, while that of the theoretical method is mainly from 6% to 8%, and the mean of the difference between the two deviation ratios is about 3%, verifying the feasibility of the modified model used for the calculation of the reference value. Meanwhile, the value of the equivalent friction coefficient fluctuates in the range of 0.006–0.018, which is affected more significantly by the working pressure than the speed, suggesting that the working pressure can be given priority as the design basis of the friction coefficient for 750 mL/r displacement piston pumps.
10
Guan, Dong, Harry H. Hilton, Zhengwei Yang, Li Jing e Kuan Lu. "Lubrication regime analysis for spherical pump". Industrial Lubrication and Tribology 70, n. 8 (12 novembre 2018): 1437–46. http://dx.doi.org/10.1108/ilt-07-2017-0207.
Testo completoAbstract (sommario):
Purpose This paper aims to investigate the lubrication regime in spherical pump, especially under different structural parameters and operational conditions. Design/methodology/approach A ball-on-plane configuration is adopted to represent the contact model between spherical piston and cylinder cover. The governing equations, which include the Reynolds and elasticity equations, are solved and validated by Jin–Dowson model. Both minimum film thickness and lambda ratio (ratio of minimum fluid film thickness to combined surface roughness of the piston and cylinder cover) of the equivalent model are obtained using an established model. Findings The results indicate that piston diameter and radial clearance are the two main factors affecting the pump lubrication regime. Other related parameters such as rotation speed of the piston, load, viscosity of working medium, material matching and surface roughness of piston and cylinder cover also have different impacts on the lubrication regime of the spherical pump. Originality/value These results emphasize the importance of the design and manufacturing parameters on the tribological performance of spherical pumps and these are also helpful in improving the spherical pump lubrication regime and enlarging its life cycle. This is to certify that to the best of the authors’ knowledge, the content of this manuscript is their own work. This manuscript has only been submitted to this journal and never been published elsewhere. The authors certify that the intellectual content of this manuscript is the product of their own work and that all the assistance received in preparing this manuscript and sources has been acknowledged.
11
Zheng, Da Yuan, Yi Peng Cao e Wen Ping Zhang. "Study of Side Thrust of Diesel Piston Based on Time-Domain Finite Element Method". Applied Mechanics and Materials 229-231 (novembre 2012): 461–64. http://dx.doi.org/10.4028/www.scientific.net/amm.229-231.461.
Testo completoAbstract (sommario):
Grasping the transmission of side thrust of piston is one of the effective methods to control engine vibration and noise. The paper uses time-domain FEM to study engine vibration. Firstly the finite element model is established after simplifications and modal analysis is conducted. Then the side thrust of piston is calculated and applied to cylinder liner using equivalent nodal load. The surface vibration is gained, from which it can be concluded that the displacements of upper block and top cylinder head reflect changes in cylinder pressure, while the vibration of observation window is complex. Finally, the vibration in a variety of engine working conditions is analyzed. Under load characteristics, the amplitude of engine surface vibration changes with loading; under propulsion characteristics, the surface vibration is essentially the same.
12
SHUSSER, MICHAEL, e MORTEZA GHARIB. "A model for vortex ring formation in a starting buoyant plume". Journal of Fluid Mechanics 416 (10 agosto 2000): 173–85. http://dx.doi.org/10.1017/s0022112000008727.
Testo completoAbstract (sommario):
Vortex ring formation in a starting axisymmetric buoyant plume is considered. A model describing the process is proposed and a physical explanation based on the Kelvin–Benjamin variational principle for steady vortex rings is provided. It is shown that Lundgren et al.'s (1992) time scale, the ratio of the velocity of a buoyant plume after it has travelled one diameter to its diameter, is equivalent to the time scale (formation time) proposed by Gharib et al. (1998) for uniform-density vortex rings generated with a piston/cylinder arrangement. It is also shown that, similarly to piston-generated vortex rings (Gharib et al. 1998), the buoyant vortex ring pinches off from the plume when the latter can no longer provide the energy required for steady vortex ring existence. The dimensionless time of the pinch-off (the formation number) can be reasonably well predicted by assuming that at pinch-of the vortex ring propagation velocity exceeds the plume velocity. The predictions of the model are compared with available experimental results.
13
Wang, L.-R., J.-C. Wang, Z.-H. Lu e I. Hagiwara. "Finite element-based parameter estimations for a characteristic simulation model of a hydraulically damped rubber mount for vehicle engines". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 221, n. 10 (1 ottobre 2007): 1273–86. http://dx.doi.org/10.1243/09544070jauto153.
Testo completoAbstract (sommario):
The hydraulically damped rubber mount (HDM) is widely used for vibration isolation in automotive powertrains and other dynamic systems. In predictions of its dynamic characteristics, some key parameters or parametric characteristics in the lumped-parameter dynamic analysis model of an HDM, such as the volumetric elastic characteristics of fluid chambers and the equivalent piston cross-sectional area of the upper chamber, must be especially determined, because they are difficult to measure by experiment owing to fluid-structure interactions (FSIs). In this paper, a numerical simulation approach of volumetric elastic characteristics is developed on the basis of finite element analysis methods relating to rubber material hyperelasticity and hydrostatic FSI using ABAQUS software. Volumetric elastic characteristics of the upper fluid chamber, including the main rubber spring and/or uncoupling rubber membrane, and that of the lower fluid chamber are identified; volumetric stiffness and equivalent piston cross-sectional area are also calculated for further dynamic characteristic simulations of HDM. The contributions of different rubber parts to the volumetric elastic characteristics of the upper chamber are revealed. Predications of dynamic characteristics and frequency response analysis of a typical HDM with fixed decoupler verify the effectiveness of the proposed parameter identification method. The proposed simulation methods of volumetric elastic characteristics can be applied to other FSI systems.
14
Hu, Guoliang, Hao Liu, Jinfu Duan e Lifan Yu. "Damping performance analysis of magnetorheological damper with serial-type flow channels". Advances in Mechanical Engineering 11, n. 1 (gennaio 2019): 168781401881684. http://dx.doi.org/10.1177/1687814018816842.
Testo completoAbstract (sommario):
In order to obtain a larger damping force with the limited axial size of the vehicle suspension system, a new magnetorheological damper with serial-type flow channels was developed. The piston head was equipped with two piston end covers, three piston non-magnetic sleeves, and four piston magnetic sleeves, which were sequentially combined into three serial-type flow channels to form three groups of effective damping gaps. The structure and principle of the proposed magnetorheological damper were described in detail, and the model for calculating damping force was deduced too. Simulation and analysis for the proposed magnetorheological damper was implemented using electromagnetic field simulation software. The damping performance was tested and analyzed on the test rig under different applied current, amplitude, and frequency excitation. The experimental results show that the damping force is 6838 N under the load excitation with frequency of 1 Hz, amplitude of 7.5 mm, and current of 1.5 A, which is 1.6 times than the expected damping force. The equivalent damping coefficient is attained to 290 kN/s m−1, which shows that the developed magnetorheological damper has high vibration control ability and good mechanical properties.
15
Guo, Y., DS Liu, LP Huang, M. Jiang e YP Jin. "Dynamics of disc storing mechanism with joint clearance driven by hydraulic cylinder". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, n. 18 (2 febbraio 2015): 3484–98. http://dx.doi.org/10.1177/0954406215570699.
Testo completoAbstract (sommario):
Disc storing mechanism driven by hydraulic cylinder is the key component to ensure the deep sea coring. However, clearance is inevitable for assembly in joint of mechanism lead to poor operational characteristics. To ensure design and working reliability, disc storing mechanism driven by hydraulic cylinder for benthic drill with clearance is analyzed from a dynamic view. With piston rod be equivalent to slider, engaging lugs at end of cylinder to revolute joint and contact impact model deal with clearance, the dynamic model of disc storing mechanism driving by piston rod is present. The simulation model for the mechanism with clearance driven by cylinder using Simulink is established and analysis of dynamics is investigated. The simulation results for the case with and without clearance are evaluated under different driving conditions for motion characteristics and driving force. The effect of clearance to disc storing mechanism driven by hydraulic cylinder is found. These supply a lead for moving parameters choosing and a theory basis for key parts designing of the mechanism.
16
Lebrun, Tristan, e Thomas Hélie. "Correction of the Doppler distortion generated by a vibrating baffled piston". Acta Acustica 4, n. 1 (2020): 2. http://dx.doi.org/10.1051/aacus/2020002.
Testo completoAbstract (sommario):
The Doppler effect is a phenomenon inherent to source motion, which introduces a variable propagation time between the source and a listening point. In the case of a vibrating piston, this is responsible for distortion of the radiated sound pressure. This moving-boundary phenomenon is part of the nonlinear effects involved in loudspeaker radiation. The present paper investigates the significance of this distortion, usually considered as neglectible, and addresses its correction. First, the direct problem is solved by: (a) converting the (Lagrangian) position of the moving source into its equivalent (Eulerian) velocity field at a fixed position; (b) deriving the acoustic pressure radiated from this velocity field. A series solution of (a) is derived and time-domain simulations of (b) are built from the truncated series combined with a baffled piston radiation model. Simulations show that Doppler distortion can be significant for realistic loudspeaker diaphragm motion with a wide spectral content. Second, the inverse (anti-Doppler) problem is examined, that is, the derivation of a piston displacement that generates a targeted Eulerian velocity field. The corrected piston velocity solution proves to be an uncentered signal, leading to a diverging displacement. In order to remove this practical problem, a centered approximation is preferred, based on modified inverse Volterra kernels. The anti-Doppler algorithm is reliable in the audio range.
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ALLEN, J. J., e M. S. CHONG. "Vortex formation in front of a piston moving through a cylinder". Journal of Fluid Mechanics 416 (10 agosto 2000): 1–28. http://dx.doi.org/10.1017/s002211200000865x.
Testo completoAbstract (sommario):
This paper contains the details of an experimental study of the vortex formed in front of a piston as it moves through a cylinder. The mechanism for the formation of this vortex is the removal of the boundary layer forming on the cylinder wall in front of the advancing piston. The trajectory of the vortex core and the vorticity distribution on the developing vortex have been measured for a range of piston velocities. Velocity field measurements indicate that the vortex is essentially an inviscid structure at the Reynolds numbers considered, with viscous effects limited to the immediate corner region. Inviscid flow is defined in this paper as being a region of the flow where inertial forces are significantly larger than viscous forces. Flow visualization and vorticity measurements show that the vortex is composed mainly of material from the boundary layer forming over the cylinder wall. The characteristic dimension of the vortex appears to scale in a self-similar fashion, while it is small in relation to the apparatus length scale. This scaling rate of t0.85+0.7m, where the piston speed is described as a power law Atm, is somewhat faster than the t3/4 scaling predicted by Tabaczynski et al. (1970) and considerably faster than a viscous scaling rate of t1/2. The reason for the structure scaling more rapidly than predicted is the self-induced effect of the secondary vorticity that is generated on the piston face. The vorticity distribution shows a distinct spiral structure that is smoothed by the action of viscosity. The strength of the separated vortex also appears to scale in a self-similar fashion as t2m+1. This rate is the same as suggested from a simple model of the flow that approximates the vorticity being ejected from the corner as being equivalent to the flux of vorticity over a flat plate started from rest. However, the strength of the vorticity on the separated structure is 25% of that suggested by this model, sometimes referred to as the ‘slug’ model. Results show that significant secondary vorticity is generated on the piston face, forming in response to the separating primary vortex. This secondary vorticity grows at the same rate as the primary vorticity and is wrapped around the outside of the primary structure and causes it to advect away from the piston surface.
18
Faіtar, Catalіn, Liviu-Constantin Stan e Nicolae Buzbuchi. "Performance and reliability of exhaust gas recovery units for marine engines". Technium: Romanian Journal of Applied Sciences and Technology 4, n. 8 (25 agosto 2022): 23–32. http://dx.doi.org/10.47577/technium.v4i8.7262.
Testo completoAbstract (sommario):
Although the marine diesel engine market is dominated by slow-coupled two-stroke engines with a direct coupling system and a crossover system or four-stroke engines with medium or high speeds, equipped with a reversing system, there is a hybrid variant that has always been used by the market in Japan and East Asia, especially by coastal or fishing operators. These are four-stroke slow engines. These types of engines are a specialty specific to the Japanese profile industry, being characterized by a simple and robust construction and fairly long piston strokes. The rated speeds of these motors do not exceed 200 rpm, which allows direct coupling to the propeller, eliminating the need for a reduction system. Compared to equivalent engines on the US or EU market, where medium or high speed four-stroke engines are preferred, the Japanese model has 6-cylinder in-line configurations, and the piston diameters of these engines may vary depending on the need for on market. For example, Akasaka Diesel built engines of the same type using piston diameters ranging from 220 mm to 510 mm, all with in-line 6-cylinder configuration.
19
Zhao, Qiang, e Fang Gao. "Bond graph modelling of hydraulic six-degree-of-freedom motion simulator". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 226, n. 12 (28 febbraio 2012): 2887–901. http://dx.doi.org/10.1177/0954406212440067.
Testo completoAbstract (sommario):
Stewart-type six-degree-of-freedom motion simulator is a multidisciplinary system containing multiple mechanical, hydraulic and electric components. This article proposed a unified bond graph representation for the simulator. First, dynamics equations of the upper platform are developed using Newton–Euler method and its bond graph model is established. Each hydraulic actuator is then modelled according to the three basic equations of valve-controlled cylinder. An equivalent approach is further employed to treat the inertial effects of each cylinder. This approach projects the forces caused by the cylinder inertia equivalently onto the joint point of the upper platform, which relatively simplifies the modelling of the piston and the tube. The whole simulator takes independent close-loop position feedback control on each valve-controlled cylinder actuator. A proportional controller with dynamic pressure feedback and feed-forward compensation is proposed. The bond graph model of the overall simulator is finally completed with 20-Sim software, and further simulations and experiments are carried out to verify the model. The model provides another reference for motion simulator modelling besides the multibond graph approach.
20
Li, Yong Feng, e Zhi Quan Xiao. "Modeling and Simulating Long-Stroke Valve-Controlled Asymmetrical Cylinder Based on MATLAB/Simulink". Advanced Materials Research 337 (settembre 2011): 695–700. http://dx.doi.org/10.4028/www.scientific.net/amr.337.695.
Testo completoAbstract (sommario):
Abstract. Based on the redefined flow rate and flow pressure, the forward and backward state equations of long-stroke valve-controlled asymmetrical cylinder system are set up, in which the general mistakes in building up the flow rate equation are avoided. Then the simulation model in MATLAB/Simulink is established. Adopting the conditional-executive subsystem blocks, joint simulation with different models at two directions is realized by taking into account the continuity problems in positioning reversal. The subsystem of introduced equivalent volume function helps to show the effects of piston working position to valve-controlled cylinder system. Furthermore, with this simulation model, dynamic performance analysis of long-stroke valve-controlled asymmetrical cylinder system including some nonlinear factors becomes convenient.
21
Li, Hai Ning, Dan Li e Xin Xin. "The Finite Element Analysis of Lei-Ring Applied to Upright Column for Hydraulic Support". Applied Mechanics and Materials 635-637 (settembre 2014): 541–44. http://dx.doi.org/10.4028/www.scientific.net/amm.635-637.541.
Testo completoAbstract (sommario):
Abstract:In this paper ,the finite element model of the lei-ring was established in ANSYS software,the sealing performance of hydraulic support column piston was analyzed.Also,the numerical simulation analysis was made of the impact of column working pressure on the sealing performance,and a series of the integrated equivalent stress and contact pressure images of sealing ring when working were got. From those images,the location most prone to failure can be concluded.All of work can provide a theoretical reference for the design and use of drum sealing ring used on hydraulic support upright column.
22
Özdemir, Ömer, Felix Fischer, Adrian Rienäcker e Katharina Schmitz. "Thermo-elastohydrodynamic simulation of the piston-cylinder contact in high-pressure pumps at 3000 bar". Industrial Lubrication and Tribology 71, n. 5 (8 luglio 2019): 702–5. http://dx.doi.org/10.1108/ilt-05-2018-0169.
Testo completoAbstract (sommario):
Purpose The purpose of this paper is to show these effects in an abstracted micro gap test bench. Because of stronger emission laws, the ambition to raise the rail pressure in common-rail systems from the current 2500 bar to 3000 bar is a given. The pressure increase will allow fine atomization of fuel and therefore more efficient combustion. But within the technical system of the high-pressure pump, stronger thermal stresses of the piston–cylinder contact are expected. A pressure drop from such a high level causes high temperature gradients due to energy dissipation. Design/methodology/approach For a detailed examination, the critical piston–cylinder contact has been investigated in an abstracted test bench with a flat parallel gap and an equivalent thermo-elastohydrodynamic simulation model. Findings The simulation results show good accordance to the measurements of pressures, temperatures and leakages for pressures up to 3000 bar. Comparison with elastohydrodynamic lubrication results outlines the need to consider temperature and pressure effects viscosity and solid deformation for the simulation and design of tribological contacts at high pressures. Originality/value This paper describes a simulation method with high accuracy to investigate tribological contacts considering temperature effects on solid structures and the fluid film. The thermo-elastohydrodynamic lubrication simulation method is valid not only for piston–cylinder contacts in high-pressure pumps but also for journal bearings in combustion engines.
23
Zhang, Jian, Jianyao Wang, Qingshan Yang e Qiusheng Li. "Simulation of Piston Effects on Platform Screen Doors Considering Air Leakage". Atmosphere 13, n. 12 (25 novembre 2022): 1967. http://dx.doi.org/10.3390/atmos13121967.
Testo completoAbstract (sommario):
The complex wind effects around platform screen doors (PSDs) caused by train-induced piston wind effect and positive micropressure waves in subway station platforms are investigated. Numerical modeling of the wind field around full-scale PSDs with real gaps under different inflow conditions is developed to analyze the pressure distributions on and around the PSDs and the corresponding recirculation regions in the frontal and rear PSD areas with computational fluid dynamics (CFD) method. An equivalent porous media model is developed to obtain the relationship between the pressure difference and wind velocity based on Darcy–Forchheimer’s Law. It includes a viscosity loss term and an inertial loss term in the simulation of the air leakage flow generated from the PSD gap. The coefficients of these two terms are estimated from the CFD results from the full-scale models. The complicated flow field originated from the gaps is the main cause of the large wind pressure on the PSD, and the flow velocity on the platform may significantly affect the comfort of pedestrians and of the safety design of the PSD system.
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Wang, Xinxin, e Xiaoqiang Yan. "Dynamic Model of the Hot Strip Rolling Mill Vibration Resulting from Entry Thickness Deviation and Its Dynamic Characteristics". Mathematical Problems in Engineering 2019 (25 febbraio 2019): 1–11. http://dx.doi.org/10.1155/2019/5868740.
Testo completoAbstract (sommario):
The vibration demolding of the crystallizer leads to slab thickness deviation in continuous casting processes. Therefore, in this paper, the dynamic model of the hot strip rolling mill vibration resulting from entry thickness deviation is proposed and its dynamic characteristics are studied. First, the dynamic model of vertical vibration in the hot strip rolling mill is established based on Sims’ rolling force model. Then, the model validity is certified by comparing the simulation with field test data from a 1580 hot strip rolling mill. Finally, we investigate the influence of model parameters on the dynamic characteristics of hot strip rolling mill vibration resulting from entry thickness deviation. The result indicates that hot strip rolling mill vibration resulting from entry thickness deviation can be reduced by increasing the area of the hydraulic cylinder piston side and the entry thickness as well as by decreasing the deformation resistance, rolling speed, and equivalent stiffness.
25
Zha, Wenjing, Chihua Lu, Zhi’en Liu, Guohong Li e Jinliang Luo. "Simulation of dynamic characteristics of suspension hydraulic bushing". Journal of Physics: Conference Series 2528, n. 1 (1 luglio 2023): 012020. http://dx.doi.org/10.1088/1742-6596/2528/1/012020.
Testo completoAbstract (sommario):
Abstract The hydraulic bushing is a common vibration isolator, and its dynamic characteristics influence the ride comfort of the vehicle. Aiming at a suspension hydraulic bushing with inertia components, a one-dimensional model of the hydraulic bushing is established based on Amesim. Secondly, a parameter identification method is proposed, and the equivalent piston area of the hydraulic bushing and the diaphragm strain stiffness are identified by this method. Finally, the identified parameters are input into the Amesim model, and the data results are compared with the experimental results after processing with MatLab. The results show that the dynamic characteristic curve of the hydraulic bushing calculated by this method is consistent with the test curve and can well predict the dynamic characteristics of the hydraulic bushing with inertia elements.
26
Meyer, Colin R., Kaitlin M. Keegan, Ian Baker e Robert L. Hawley. "A model for French-press experiments of dry snow compaction". Cryosphere 14, n. 5 (5 maggio 2020): 1449–58. http://dx.doi.org/10.5194/tc-14-1449-2020.
Testo completoAbstract (sommario):
Abstract. Snow densification stores water in alpine regions and transforms snow into ice on the surface of glaciers. Despite its importance in determining snow-water equivalent and glacier-induced sea level rise, we still lack a complete understanding of the physical mechanisms underlying snow compaction. In essence, compaction is a rheological process, where the rheology evolves with depth due to variation in temperature, pressure, humidity, and meltwater. The rheology of snow compaction can be determined in a few ways, for example, through empirical investigations (e.g., Herron and Langway, 1980), by microstructural considerations (e.g., Alley, 1987), or by measuring the rheology directly, which is the approach we take here. Using a French-press or cafetière-à-piston compression stage, Wang and Baker (2013) compressed numerous snow samples of different densities. Here we derive a mixture theory for compaction and airflow through the porous snow to compare against these experimental data. We find that a plastic compaction law explains experimental results. Taking standard forms for the permeability and effective pressure as functions of the porosity, we show that this compaction mode persists for a range of densities and overburden loads. These findings suggest that measuring compaction in the lab is a promising direction for determining the rheology of snow through its many stages of densification.
27
Liu, Wei, Jie Huang, Yong Shen e Jiazheng Cheng. "Theoretical Modeling of Piezoelectric Cantilever MEMS Loudspeakers". Applied Sciences 11, n. 14 (8 luglio 2021): 6323. http://dx.doi.org/10.3390/app11146323.
Testo completoAbstract (sommario):
Piezoelectric microelectromechanical system (MEMS) loudspeakers have received extensive attention in recent years. In particular, the piezoelectric cantilever MEMS loudspeaker, which uses multilayer piezoelectric cantilever actuators (MPCAs), has attracted attention because of its small size, low cost, ease of manufacture, and desirable piston movement. However, owing to the complex driving principles of MPCAs, no adequately efficient and appropriate method currently exists that can be used to analyze and predict the performance of piezoelectric cantilever MEMS loudspeakers. In this study, the equivalent circuit method (ECM) is adopted to theoretically model piezoelectric cantilever MEMS loudspeakers, and an ECM model with a special MPCA transformer for electromechanical conversion is proposed. With the proposed ECM model, the performance characteristics of piezoelectric cantilever MEMS loudspeakers, such as the displacement and sound pressure response, can be calculated efficiently and conveniently. To verify the accuracy of the ECM model, the finite element method is adopted for simulation, and the simulated results are compared with those of the ECM models. A satisfactory agreement was found, which verifies the accuracy of the proposed ECM model.
28
Griffin, Steve, Steven A. Lane e Steve Huybrechts. "Coupled Helmholtz Resonators for Acoustic Attenuation". Journal of Vibration and Acoustics 123, n. 1 (1 agosto 2000): 11–17. http://dx.doi.org/10.1115/1.1320812.
Testo completoAbstract (sommario):
Helmholtz resonators are used in a variety of applications to reduce the transmission of unwanted sound. This work demonstrates that mechanically coupled resonators can be used to design a particular transmission loss response, provide a wider bandwidth of attenuation, and adapt the transmission loss characteristics of a structure to attenuate disturbances of varying frequency. An analytical model is developed for a single, coupled resonator system mounted on a one-dimensional duct. Experiments are conducted on a similar system that uses a thin membrane to couple the resonator volumes. A simplistic model of the membrane is presented to estimate equivalent “piston” properties from measured physical properties. Experiments confirm that the coupled resonator system behaves as predicted by the model simulations, and that the transmission loss can be shaped by adjusting the mass or stiffness of the coupling member. The experimental results also illustrate the structural-acoustic coupling effects between the resonators and the membrane, and indicate that a more inclusive model of the membrane and acoustic dynamics is required in order to accurately predict the resonator transmission loss.
29
Rezaeealam, Behrooz. "Losses Computation in Reciprocating Tubular Permanent Magnet Generator with SMC Core". International Journal of Power Electronics and Drive Systems (IJPEDS) 9, n. 4 (1 dicembre 2018): 1545. http://dx.doi.org/10.11591/ijpeds.v9.i4.pp1545-1551.
Testo completoAbstract (sommario):
Generally, the Permanent Magnet Tubular Generators (PMTG) are employed in the free-piston generator systems. In this paper, the PMTG with the core made of Soft Magnetic Composite (SMC) is employed, and then, the PMTG with the solid SMC core has cylindrical symmetry and also the outer diameter of the machine reduces in comparison to the ones with multipart laminated steel cores in which each part is radially placed along the air-gap and there is unexploited space between them. Here, a Finite Element Method (FEM) is developed in which the reciprocating motion of the translator is considered by moving mesh techniques and moreover, the Jiles-Atherton (JA) scalar hysteresis model is incorporated in the FE model to take into account the hysteresis losses. Then, the copper and core losses are computed and the equivalent circuit of the generator is derived. The calculated losses are compared with the ones obtained from the analytical methods.
30
Kim, Gi-Heon, Allan Kirkpatrick e Charles Mitchell. "Supersonic Virtual Valve Design for Numerical Simulation of a Large-Bore Natural Gas Engine". Journal of Engineering for Gas Turbines and Power 129, n. 4 (20 febbraio 2007): 1065–71. http://dx.doi.org/10.1115/1.2747251.
Testo completoAbstract (sommario):
In many applications of supersonic injection devices, three-dimensional computation that can model a complex supersonic jet has become critical. However, in spite of its increasing necessity, it is computationally costly to capture the details of supersonic structures in intricate three-dimensional geometries with moving boundaries. In large-bore stationary natural gas fueled engine research, one of the most promising mixing enhancement technologies currently used for natural gas engines is high-pressure fuel injection. Consequently, this creates considerable interest in three-dimensional computational simulations that can examine the entire injection and mixing process in engines using high-pressure injection and can determine the impact of injector design on engine performance. However, the cost of three-dimensional engine simulations—including a moving piston and the kinetics of combustion and pollutant production—quickly becomes considerable in terms of simulation time requirements. One limiting factor is the modeling of the small length scales of the poppet valve flow. Such length scales can be three orders of magnitude smaller than cylinder length scales. The objective of this paper is to describe the development of a methodology for the design of a simple geometry supersonic virtual valve that can be substituted in three-dimensional numerical models for the complex shrouded poppet valve injection system actually installed in the engine to be simulated. Downstream flow characteristics of the jets from an actual valve and various virtual valves are compared. Relevant mixing parameters, such as local equivalent ratio and turbulence kinetic energy, are evaluated in full-scale moving piston simulations that include the effect of the jet-piston interaction. A comparison of the results has indicated that it is possible to design a simple converging-diverging fuel nozzle that will produce the same jet and, subsequently, the same large-scale and turbulent-scale mixing patterns in the engine cylinder as a real poppet valve.
31
He, Tao, Zhipeng Li, Haishun Deng, Qiangman Chen, Chuanli Wang e Kaiping Zhao. "Flow characteristics analysis of a balanced valve distribution double-row axial piston pump". Mechanical Sciences 13, n. 1 (14 marzo 2022): 207–23. http://dx.doi.org/10.5194/ms-13-207-2022.
Testo completoAbstract (sommario):
Abstract. To study the flow characteristics of a new swashplate rotary valve distribution double-row axial piston pump, an instantaneous flow model was developed for the pump, the influences of structural parameters on the flow pulsation and uneven coefficient of flow were determined, and the ideal plunger distribution parameters were derived. On this basis, a valve distribution model was developed for the pump, the flow superposition process in the plunger cavity was analyzed, and the high-speed switching valve's control strategy was optimized. Additionally, the effects of parameters such as the plunger motion frequency, the plunger cavity's dead zone volume, the spool valve's preloading force, and the spool's equivalent mass on the flow characteristics were studied. The results show that the new pump had a small flow pulsation when there were five plungers in both the inner and outer rows and the dislocation angle was 18∘. The plunger's reverse-suction effect at the moment when the discharge valve opened and the suction valve closed and the plunger cavity's dead zone volume size were the primary factors affecting the size of the pump's flow spike. The discharge valve's opening was delayed by 3 ms to be consistent with the suction valve's closing time; for this case, the flow peak was small and the volumetric efficiency was the highest. The discharge valve began to close 2 ms early and closed completely at the critical point when the plunger transferred from the discharge stroke to the suction stroke, which helped the suction valve to open on time and improved the pump's oil absorption capacity. The active opening and closing control of the discharge valve improved the coordination of the flow distribution to a large extent, reduced the hysteresis of the suction valve, and ultimately improved the pump's volumetric efficiency and flow stability. The results of this study can provide theoretical guidance for the flow control of balanced double-row axial piston pumps with valve distribution.
32
Olczyk, A. "Identification of dynamic phenomena in pipes supplied with a pulsating flow of gas". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 223, n. 8 (2 aprile 2009): 1851–67. http://dx.doi.org/10.1243/09544062jmes1386.
Testo completoAbstract (sommario):
Pulsating flow is typical of displacement machines such as piston engines, compressors, or other displacement devices. The cyclic movement of the working element (piston, valve, membrane, etc.) generates pulsations, which, from a dynamic point of view, can be considered as excitation in the system composed of a flowing gas and pipes in which the flow takes place. This study shows that under certain conditions, a significant increase of pulse amplitudes occurs and transient values of main flow parameters are up to a few times higher than that for the equivalent steady flow conditions. This unsteadiness can be harmful or even damaging; however, in some cases it can be profitable (e.g. induction ramming of combustion engines). In order to investigate which conditions are favourable to obtain such effects in pipes, four different systems, distinguished by a different level of choking at the pipe outlet section, were tested. The experimental tests performed in the range of excitation frequencies of 0—200 Hz have shown that systems with low choking at the pipe outlet are more prone to strong dynamic effects, characterized by considerable growth of pulse amplitudes and an intensive reverse flow occurring in the proximity of resonance frequencies. In systems with high choking at the pipe outlet section, those effects were very weak. Characteristic frequencies, for which the resonance takes place, depend on the pipe length and can be determined theoretically with a simple acoustic model or a one-dimensional model ‘ x— t’ describing a pulsating flow in the pipe. The experimental verification of those resonance frequencies can be conducted with the use of transient flow parameters recorded by appropriate fast response sensors.
33
Zhang, Junhua, Zhaochen Yan e Lili Xia. "Vibration and Flutter of a Honeycomb Sandwich Plate with Zero Poisson’s Ratio". Mathematics 9, n. 19 (8 ottobre 2021): 2528. http://dx.doi.org/10.3390/math9192528.
Testo completoAbstract (sommario):
A honeycomb is a kind of excellent lightweight structure and a honeycomb sandwich plate with zero Poisson’s ratio (ZPR) core is used widely in morphing structures. In this paper, a sandwich plate composed of a honeycomb core with zero Poisson’s ratio is analyzed for free vibrations and flutter under supersonic airflows. The equivalent elastic parametric formulas of the honeycomb core for zero Poisson’s ratio are proposed. The models are compared for their natural frequencies by theoretical and finite element methods respectively, which verifies the validity of the equivalent elastic parametric formulas and the model for the honeycomb sandwich plate with zero Poisson’s ratio. The influence of the geometric parameters of the honeycomb plate on the vibration frequencies is obtained. Three kinds of honeycomb cores, namely, regular hexagon, auxetic and hybrid with zero Poisson’s ratio, are compared through natural frequencies of the sandwich plate. It is found that the frequency of the zero Poisson’s ratio honeycomb sandwich plate is the second one when the other parameters are the same. The flutter of the honeycomb plate is analyzed by using the first order piston theory under supersonic flows. The critical flutter velocity of the plate is obtained, and the influence of geometric parameters of the honeycomb plate on the critical flutter velocities is obtained.
34
Budinsky, Tomas, Peter Brooks e David Barton. "A New Analytical Model of the Brake Pad for Improved Calculation of the Centre of Pressure and Friction Coefficient in A Multi-Piston Disc Brake". International Journal of Engineering & Technology 7, n. 3.17 (1 agosto 2018): 54. http://dx.doi.org/10.14419/ijet.v7i3.17.16623.
Testo completoAbstract (sommario):
In recent experimental work it has been observed that the position of the centre of pressure (CoP) at the brake pad/disc interface has an influence on the onset of brake squeal. To determine the CoP during a braking event, a simple two-dimensional analytical model of the brake pad or more complex numerical finite element model of a disc brake are commonly used. This paper presents a new three-dimensional analytical model of a brake pad that determines the CoP position in both circumferential and radial directions. Due to higher complexity, this model provides more realistic clamp and friction force values, which can be used together with the more accurate radial position of the CoP for evaluation of the brake torque. The CoP position calculated using the new model was compared with the CoP evaluated by a finite-element model of an equivalent 8-piston opposed disc brake. The CoP results across the whole pad/disc interface showed a close correlation between these two approaches, giving the new analytical model a potential use in applications where an instantaneous value of the CoP with good accuracy is required. Finally, the new model was used to demonstrate possible improvement of the traditional method of the friction coefficient calculation. Due to greater accuracy the new model gives an approximately 8% larger value of the friction coefficient than the traditional approach.
35
Li, Xiao Peng, Guang Hui Zhao, Ya Min Liang, Xing Ju, Quan Bin Wang e Li Li Xin. "Compaction Effect of Granular System with Parameters Changed". Materials Science Forum 773-774 (novembre 2013): 626–31. http://dx.doi.org/10.4028/www.scientific.net/msf.773-774.626.
Testo completoAbstract (sommario):
In this work, the numerical equation has been established to simulate the vibratory compaction system based on the hysteresis loop of Davidenkov and with the gap ignored between the piston and the materials, and the dynamical characteristics and influence of parameters on the vibration compaction effect were analyzed with different stiffness, damping, amplitude and mass. Two types of experiments were carried out to study the dynamical characteristics and validate the numerical analysis and simulation. The first type of experiments was done with the different exciting vibration amplitude. The second type of experiments was done with the different water saturation instead of the stiffness and damping. The numerical and experimental results show that the equivalent natural frequency and vibration amplitude of the system increased with the stiffness, exciting amplitude increased and damping decreased. The experimental results agree well with results from a theoretical model in general. The research results will be used in intelligent granular compaction in the future.
36
Li, Xiao Peng, Yun Nan Teng, Li Li Xin e Bang Chun Wen. "Experimental Investigation of Characteristics of Vibratory Compaction System with Different Water Saturation". Applied Mechanics and Materials 29-32 (agosto 2010): 1488–93. http://dx.doi.org/10.4028/www.scientific.net/amm.29-32.1488.
Testo completoAbstract (sommario):
In this work, the numerical equation has been established to simulate the vibratory compaction system based on the hysteresis loop of Davidenkov and with the gap ignored between the piston and the materials, and the dynamical characteristics and influence of parameters on the vibration compaction effect were analyzed with different stiffness, damping, amplitude and mass with different water saturation. The two types of experiments were carried out to study the dynamical characteristics and validate the numerical analysis and simulation. The first type of experiments was done with the different exciting vibration amplitude. A second type of experiments was done with the different water saturation (3%, 8% and 17%) instead of the stiffness and damping. The numerical and experimental results show that the equivalent natural frequency and vibration amplitude of the system increased with the stiffness, exciting amplitude increased and damping decreased. The experimental results agree well with results from a theoretical model in general. The research results will be used in intelligent soil compaction in the future.
37
Yuan, Wenhua, Xueliang Huang, Jun Fu, Yi Ma, Guangming Li e Qike Huang. "Water Vapor Blending Ratio Effects on Combustion Thermal Performance and Emission of Hydrogen Homogeneous Charge Compression Ignition". Energies 15, n. 23 (29 novembre 2022): 9055. http://dx.doi.org/10.3390/en15239055.
Testo completoAbstract (sommario):
A numerical model of the micro-free-piston engine was developed and its correctness was verified by the comparison between the simulation and referential experiment results under the same work conditions. Based on this numerical model, the effects of the water vapor blending ratio (α) on combustion thermal performance and emission characteristics of hydrogen (H2) homogeneous charge compressing ignition (HCCI) were investigated numerically. The water vapor impact on combustion temperature was analyzed as well. The simulation results reveal that when the initial equivalent ratio is 0.5, blending H2 with water vapor can delay the ignition time and prolong the whole process. At the same time, the addition of water vapor to H2 decreases the peak combustion temperature and pressure, which will alleviate the detonation phenomenon of the combustion chamber. Moreover, the power output capacity and NOx emissions decrease with the increase in α. When α increases to 0.8, the mixture gas cannot be compressed to ignite. Finally, the dilution effect, thermal effect, and chemical effect of water vapor all have the potential to lower the combustion temperature and the dilution effect plays the leading role.
38
Kottapalli, Shravan, Remco van de Meerendonk, Nicholas Waterson, Gunes Nakiboglu, Avraham Hirschberg e David M. J. Smeulders. "Analytical modelling and experimental validation of compliance-based low-frequency resonators for water circuits". Acta Acustica 6 (2022): 56. http://dx.doi.org/10.1051/aacus/2022050.
Testo completoAbstract (sommario):
Transmission losses of compact compliance-based resonators in water circuits are investigated. Experiments are performed to measure the anechoic transmission losses (TLan) of flexible-plate resonators and a gas resonator designed for frequencies between 10 and 100 Hz. The measurements are compared to theoretical results based on a lumped-element model and a finite-element model. The TLan is measured using a robust form of the multi-microphone method, which gave identical results for open and closed pipe acoustic terminations at the transmission side of the setup. When an estimate of the reflection coefficient at the termination is known, good results are obtained with only one transmission-side microphone. When TLan is high, a single microphone is sufficient on each side. For the flexible-plate resonators the TLan measurements are in agreement with theory except close to resonance, where the transmission signals are below the detection limit. Due to assumptions of a rigid cavity wall and a clamped top-plate, the theoretical resonance frequencies are too high except for the thinnest plate which displays static deformation stiffening. This deformation stiffening limits the possibility to lower the resonance frequency by using a thin flexible plate in a circuit with high static pressure. Low resonance frequencies are easier to reach with a gas resonator, in which a piston separates the water from a volume filled with air. For the gas-resonator, the measurements agree with the theoretical predictions when assuming a significant damping. The friction between the air-water-separation piston and cavity wall is suspected to cause this damping. Theory predicts that the TLan of both resonators designed for same resonance frequencies in absence of losses are equivalent. They therefore have quite similar performances except close to the resonance frequency. The flexible-plate resonator has a higher quality factor and higher (TLan) around the resonance frequency. The gas resonator is more complex and needs more maintenance but allows fine tuning of the resonance frequency by varying the gas volume.
39
Menzhinski, A. B., A. N. Malashin e Yu V. Sukhodolov. "Experimental Verification of the Adequacy of Mathematical Model of the Reciprocating Electric Electromagnetically Excited Generator". ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 62, n. 2 (4 aprile 2019): 168–76. http://dx.doi.org/10.21122/1029-7448-2019-62-2-168-176.
Testo completoAbstract (sommario):
The article presents a mathematical simulation of the electromagnetically excited generator of reciprocating type, which resulted in an equivalent circuit diagram, a magnetic circuit design of the generator and some expressions describing the electromagnetic processes in the electromagnetically excited generator of reciprocating type. The nonlinear mathematical model of the electromagnetically excited generator of reciprocating type has been developed. In order of the experimental verification of the adequacy of the mathematical model of the reciprocating electric generator, as well as of the validity of the assumptions made, a breadboard sample of the reciprocating electric generator has been made consisting of a fixed part in the form of two U-shaped magnetic cores and a moving part representing an H-shaped magnetic cores. There is focused operating winding on both the U-shaped magnetic cores. The N-shaped magnetic core is coiled with excitation winding which is connected to a DC power source. In a breadboard sample of the reciprocating electric generator a drive motor of 100 W with an amplitude of reciprocating oscillations of the moving part equal to 16 mm, and a frequency of oscillations adjustable in the range from 5 to 50 Hz is used in order to simulate a free-piston engine. The main characteristics of the generator (viz., idle speed and external characteristics) have been experimentally obtained. Comparison of experimental and calculated results demonstrated their discrepancy of no more than 4 %; therefore, the nonlinear mathematical model reflects the characteristics of the generator of longitudinal type with a high degree of adequacy.
40
Sivadas, Sumeet. "Static Structural Analysis of Different Materials for Connecting Rod". International Journal for Research in Applied Science and Engineering Technology 9, n. 12 (31 dicembre 2021): 1083–89. http://dx.doi.org/10.22214/ijraset.2021.39380.
Testo completoAbstract (sommario):
Abstract: Connecting Rods are an important and irreplaceable part of IC Engines. It is responsible for converting the reciprocating motion of the piston into the rotary motion of the crankshaft. During this process, the connecting rod is subjected to various loads. Therefore, the materials used for connecting rod are also very important. In this paper, a static structural analysis of a connecting rod made of 5 different materials: Forged Steel, Carbon Steel, Stainless Steel, Grey Cast Iron and Titanium Alloy are compared. The connecting rod is analyzed only for the axial compressive load and not the axial tensile load because the tensile load is very much lesser than the compressive load. The connecting rod’s model is developed in FUSION 360 software and then imported to and analyzed using Finite Element Method in the ANSYS 2021 WORKBENCH software. The equivalent stress, total deformation along with the factor of safety for all the materials is found and compared in the analysis and all the results are shown with the help of images and graphs. Keywords: Connecting Rod, FEA, ANSYS WORKBENCH, Structural Analysis, Forged Steel, Carbon Steel, Stainless Steel, Grey Cast Iron, Titanium Alloy.
41
Guo, Rong, Xiao-kang Wei, Sheng-qi Zhou e Jun Gao. "Parametric identification study of an active engine mount: Combination of finite element analysis and experiment". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 233, n. 2 (22 dicembre 2017): 427–39. http://dx.doi.org/10.1177/0954407017745748.
Testo completoAbstract (sommario):
An active engine mount (AEM) is an effective technology to improve a vehicle’s noise, vibration, and harshness performance. This paper mainly focuses on the combination experiment and finite element analysis (FEA) for parameter identification of AEMs. Notably, a novel test rig is designed to identify all specific parameters involved in the AEM. Firstly, the static and dynamic stiffness of the main rubber spring are calculated based on structure FEA method. The equivalent piston area and upper chamber volumetric stiffness are also estimated through fluid–structure interaction analysis. Inertia track parameters, involving inertia and linear and nonlinear resistance of the fluid, are identified by a simplified fluid model. These common hydraulic engine mount parameters are all experimentally validated through the original test rig. Besides, the particular components of the electromagnetic AEM, namely actuator parameters, are further estimated by experimental identification utilizing the experimental apparatus. The novel test bench, which exhibited high accuracy, good tightness, and strong versatility, not only simplifies the structure and process of identification plant for passive engine mount parameters, but accommodates the particular AEM ones. The combination method assimilates both the efficiency of FEA and the accuracy of experiment, facilitating the structure design and renovation of AEMs.
42
Vo, Ngoc Yen Phuong, e Thanh Danh Le. "Dynamic Analysis of Quasi-Zero Stiffness Pneumatic Vibration Isolator". Applied Sciences 12, n. 5 (24 febbraio 2022): 2378. http://dx.doi.org/10.3390/app12052378.
Testo completoAbstract (sommario):
This paper focuses on analyzing the dynamic response of an innovated quasi-zero stiffness pneumatic vibration isolator (QZSPVI) using two mechanisms, including wedge and semicircle cam. Different from other studies relating quasi-zero stiffness isolation system, the pneumatic cylinder in this paper works as an air spring in order to easily adjust the dynamic stiffness of the proposed system according to the change of the isolated load through regulating the pressure. Firstly, the dynamic stiffness of the QZSPVI will be analyzed. Then, the condition for which the minimum dynamic stiffness is quasi-zero around the equilibrium position is also determined. The fundamental resonance response of the QZSPVI subjected to the externally harmonic force is analyzed through multi-scale method and the numerical simulations are verified. Secondly, due to exiting relative sliding frictional phenomenon between the cylinder and piston, instead of an experiment, another key content of this work is to identify the friction force model of the cylinder through virtual prototyping model. From this identified result, the complex dynamic response of the QZSPVI and coexistence of multiple solutions will be discovered by realizing the direct integration of the original dynamic equation through using the 5th-order Runge–Kutta algorithm. The analysis and simulation results clearly show the advantages of the proposed model against the equivalent pneumatic vibration isolator (EPVI), which only employs the wedge mechanism. This research will offer a useful insight into design and QZSPVI in practice.
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CATER, JOHN E., e JULIO SORIA. "The evolution of round zero-net-mass-flux jets". Journal of Fluid Mechanics 472 (30 novembre 2002): 167–200. http://dx.doi.org/10.1017/s0022112002002264.
Testo completoAbstract (sommario):
This paper reports on an experimental investigation to determine the structure and mean flow quantities of round zero-net-mass-flux (ZNMF) jets. These jets are generated by a piston oscillating in a cavity behind a circular orifice. Several different flow patterns were observed with dye flow visualization and a parameter map of these was generated. Cross-correlation digital particle image velocimetry was used to measure instantaneous two-dimensional in-plane velocity fields in a plane containing the orifice axis. These velocity fields are used to investigate the existence of a self-preserving velocity profile in the far field of the ZNMF jet. The mean flow quantities and turbulent statistics of the ZNMF jets were compared with measurements for ‘equivalent’ continuous jets in the same apparatus. Phase-averaged velocity measurements were obtained in the near field of the ZNMF jets and were used to determine the radial entrainment. The out-of-plane vorticity fields were also investigated to gain an understanding of the mechanisms responsible for the difference in spreading rate of ZNMF jets compared to conventional continuous jets. A conceptual model of the ZNMF jet structure in the near field for Strouhal numbers much less than one is proposed that explains the observed behaviour of these ZNMF jets.
44
Potenza, R., J. F. Dunne, S. Vulli e D. Richardson. "A model for simulating the instantaneous crank kinematics and total mechanical losses in a multicylinder in-line engine". International Journal of Engine Research 8, n. 4 (1 agosto 2007): 379–97. http://dx.doi.org/10.1243/14680874jer00507.
Testo completoAbstract (sommario):
A two-degree-of-freedom dynamic model is constructed to simulate the instantaneous crank kinematics and total mechanical losses arising in a multicylinder gasoline engine coupled to a dynamometer. The simulation model is driven using specified cylinder gas pressures, and loaded by nominal brake torque and total friction losses. Existing semi-empirical torque loss models (based on calibrated single-cylinder diesel engine data) are used to account for the instantaneous friction losses in the piston-ring assembly, in bearings, and in auxiliaries. The model is specialized to the simulation of crank kinematics and matched brake torque for a three-cylinder in-line direct injection spark ignition (DISI) engine, without a gearbox. This allows the total friction loss to be separated from the brake torque for an engine not fitted with the very large number of sensors otherwise needed to calibrate analytical friction models. An equivalent simulation model is also constructed using GT-Crank, which excludes explicit reference to friction. In using both models to simulate steady state operation at a specified mean engine speed, the output torque is matched by iteration. The GT-Crank model necessarily compensates for internal losses by exaggerating the total output torque. Both simulation models are compared with measured crank kinematics and brake torque obtained from a dynamometer-loaded I3 DISI engine. The paper shows that by comparing the matched output torque from simulation with the measured output torque from the engine, the proposed model gives a very good high-speed prediction of the total mechanical losses. At low speed, the instantaneous model is still not accurate. It is also shown, however, that apart from the no-load condition, use of an average torque to compensate for friction (as in GT-Crank) is wholly acceptable for simulating instantaneous crank kinematics. This is the first reported instance of a simulation model (which includes the particular form of semi-empirical friction loading) being comprehensively compared and verified using multicylinder DISI engine data.
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Borushchak, L. O., e B. B. Vynnychuk. "IMPROVEMENT OF THE CONSTRUCTION AND COMPUTER DEVICE INVESTIGATION FOR THE PROCESSING OF BLOWOUT-PREVENTION HARDWARE EQUIPMENT". Scientific Bulletin of Ivano-Frankivsk National Technical University of Oil and Gas, n. 1(46) (26 giugno 2019): 16–24. http://dx.doi.org/10.31471/1993-9965-2019-1(46)-16-24.
Testo completoAbstract (sommario):
The research deals with the problem of blowout equipment test for tightness before implementation. The indicated equipment includes a stem, a system of pipelines with valves and a control system. The classic test procedure requires a mobile pumping installation that provides a pressure of 35 MPa.The cost of such tests is rather high. For testing without a pump unit, a design of a device for increased tightness has been developed, including a sealing unit of the mouth from the main column and a piston unit for creating high pressure in the test volume. Generation of a high pressure occurs by lifting the piston with a winch, mounted on the well. Disadvantages of the previously proposed design of the device are as follows. There is a considerable friction between the steel moving parts of the sealing unit. Mostly these are the pairs of a plug and a cup, and a chuck and a cone. Tightness is provided by rubber ring sleeves. Exceedence of axial load on cones causes destruction of sealing rings. The authors of the article improved the design of the sealing unit in the following way: a ball thrust bearing was seated between the ends of the pressure plug and the bottom cup and as a result the sliding friction was replaced with sliding friction. On the outer surfaces of the opening cones in contact with clamping blades, it is proposed to paste a tissue antifriction material of type Nafthlene or equivalent. The friction coefficient in such pairs is next lower order than in steel to steel pairs. The computer model of the device has been created in the Solid Works environment. The computer researches of the loading process of components of the sealing unit in the simulation program based on the finite element method were performed. As a result of the research, recommended values of the axial force, required to create a screw pair of a stem and a plug for sufficient radial axial deformation of elastic cuffs with the simultaneous non-admission of their destruction were identified. Also, the design dimensions of the pressure cups of the device were optimized, namely, the mutual axial placement of the end face, which presses on the cone, and the tapered belt, compressing the sealing ring. The determination of these parameters by an experiment is a long and expensive process.
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Harshavardhan, B., e J. M. Mallikarjuna. "Effect of Combustion Chamber Geometry on In-Cylinder Flows and Equivalence Ratio Spread in a Direct Injection Engine - A CFD Analysis". Applied Mechanics and Materials 330 (giugno 2013): 815–20. http://dx.doi.org/10.4028/www.scientific.net/amm.330.815.
Testo completoAbstract (sommario):
In this study, a CFD analysis to evaluate effect of combustion chamber geometry on in-cylinder fluid flows and equivalence ratio spread in a Direct Injection Spark Ignition Engine (DISI) during intake and compression stroke has been carried out. The analysis has been carried out using “STAR-CD es-ice” software for four piston top profiles viz., flat piston, flat piston with a centre bowl, dome piston with a central bowl and pentroof type piston with an offset bowl at an engine speed of 1000rpm. For meshing the geometric model, polyhedral trimmed cell are adopted. The solution is obtained by solving conservation of mass, momentum and energy equations using SIMPLE algorithm. From the results, it is found that for DISI engine, flat piston is best suitable.
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Zhang, Dahai, Haocai Huang, Ying Chen, Haitao Zhao e Wei Li. "State-Dependent Model of a Hydraulic Power Takeoff for an Inverse Pendulum Wave Energy Converter". Marine Technology Society Journal 49, n. 5 (1 settembre 2015): 38–48. http://dx.doi.org/10.4031/mtsj.49.5.2.
Testo completoAbstract (sommario):
AbstractThis article reports on a state-dependent model of a hydraulic power takeoff (PTO) for an inverse pendulum wave energy converter. The PTO influences the energy conversion performance by its efficiency and by the damping force exerted, which affects the motion of the body. The state-dependent model presented gives a description of the damping force and the internal dynamics of the hydraulic PTO system. Different values of the parameters of the accumulator and the motor torque are analyzed in order to improve the dynamic performance of the converter. The simulation results prove that it is possible to achieve a great enhancement of the power output with the implementation of optimization parameters of the hydraulic PTO and that a possible combination of some of them might be beneficial for improved efficiency of the system. <def-list>Nomenclature<def-item><term>A :</term><def>pipe cross-section area</def></def-item><def-item><term>B :</term><def>rotational friction coefficient</def></def-item><def-item><term>Dh :</term><def>pipe hydraulic diameter</def></def-item><def-item><term>Fy :</term><def>damping force</def></def-item><def-item><term>L :</term><def>angular momentum of the motor</def></def-item><def-item><term>Leq :</term><def>equivalent length of local resistances</def></def-item><def-item><term>Lg :</term><def>pipe geometrical length</def></def-item><def-item><term>J :</term><def>inertia momentum</def></def-item><def-item><term>kl :</term><def>motor leakage coefficient</def></def-item><def-item><term>kS :</term><def>pipe cross-section shape factor</def></def-item><def-item><term>pa :</term><def>accumulator pressure</def></def-item><def-item><term>pd :</term><def>pressure drop along the pipe</def></def-item><def-item><term>pp :</term><def>oil pressure</def></def-item><def-item><term>ppr :</term><def>precharged pressure of accumulator</def></def-item><def-item><term>qa :</term><def>accumulator flow</def></def-item><def-item><term>qleak :</term><def>leakage flow from motor</def></def-item><def-item><term>qm :</term><def>motor flow</def></def-item><def-item><term>qp :</term><def>oil flow</def></def-item><def-item><term>Re :</term><def>Reynolds number</def></def-item><def-item><term>R :</term><def>set point for damping force</def></def-item><def-item><term>S :</term><def>piston cylinder cross-section area</def></def-item><def-item><term>Tf :</term><def>losses due to rotational friction</def></def-item><def-item><term>TG :</term><def>generator torque</def></def-item><def-item><term>Tm :</term><def>motor torque</def></def-item><def-item><term>Ts :</term><def>losses due to rotational momentum</def></def-item><def-item><term>V :</term><def>oil volume</def></def-item><def-item><term>VA :</term><def>accumulator volume</def></def-item><def-item><term>V :</term><def>piston velocity</def></def-item><def-item><term>ηm :</term><def>mechanical efficiency of the motor</def></def-item><def-item><term>ωm :</term><def>angular velocity of the motor</def></def-item><def-item><term>ρ :</term><def>oil density</def></def-item></def-list>
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Qin, Zhaoju, Chenheng Yuan, Yanpeng Yuan e Yuanyuan Huang. "Tribological characteristics of piston rings in a single-piston hydraulic free-piston engine". Industrial Lubrication and Tribology 69, n. 2 (13 marzo 2017): 131–41. http://dx.doi.org/10.1108/ilt-01-2015-0011.
Testo completoAbstract (sommario):
Purpose A free-piston engine (FPE) is an unconventional engine that abandons the crank system. This paper aims to focus on a numerical simulation for the lubricating characteristics of piston rings in a single-piston hydraulic free-piston engine (HFPE). Design/methodology/approach A time-based numerical simulation program was built using Matlab to define the piston motion of the new engine. And a lubrication mode of piston rings was built which is based on the gas flow equation, hydrodynamic lubrication equation and the asperity contact equation. The piston motion and the lubrication model are coupled, and then the finite difference method is used to obtain the piston rings lubrication performances of the FPE. Meanwhile, the lubrication characteristics of the new engine were compared with those of a corresponding conventional crankshaft-driven engine. Findings The study results indicate that compared with the traditional engine, the expansion stroke of the HFPE is longer, and the compression stroke is shorter. Lubrication oil film of the new engine is thicker than the traditional engine during the initial stage of compression stroke and the final stage of the power stroke. The average friction force and power of the hydraulic free piston engine are slightly lower than those of the traditional engine, but the peak friction power of the FPE is significantly greater than that of the traditional engine. With an increase in load, the friction loss power and friction loss efficiency decrease, and with a decrease in equivalence ratio, the friction power loss reduces, but the friction loss efficiency decreases first and then increases. Research limitations/implications In this paper, only qualitative analysis was performed on the tribological difference between conventional crankshaft engine and HFPE, instead of a quantitative one. Practical implications This paper contributes to the tribological design method of HFPE. Social implications No social implications are available now, as the HFPE is under the development phase. However, the authors are positive that their work will be commercialized in the near future. Originality/value The main originality of the paper can be introduced as follows: the lubrication and friction characteristics of the new engine (HFPE) were investigated and revealed, which have not been studied before; the effect of the HFPE’s special piston motion on the tribological characteristics was considered in the lubrication simulation. The results show that compared with the traditional crankshaft engine, the new engine shows a different lubrication performance because of its free piston motion.
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Li, Xiao Long, Yang Wang, Tao Xu, Fei Yu Song, Ya Jun He e Bin Hong. "The Simulation of Hydraulic Free Piston Engine Fueled with DME in HCCI Mode". Advanced Materials Research 602-604 (dicembre 2012): 1090–94. http://dx.doi.org/10.4028/www.scientific.net/amr.602-604.1090.
Testo completoAbstract (sommario):
In order to investigate the performance of hydraulic free piston engine (HFPE) fueled with dimethyl-ether (DME) under homogeneous charge compression ignition (HCCI) combustion, one-dimensional and three-dimensional simulation models are established by AMESIM and FIRE respectively. The simulation results show that the piston’s velocity and the displacement are dissymmetric about top dead center (TDC). The residence time of piston around TDC is quite short. DME chemical reaction kinetic mechanism is applied to three-dimensional computational fluid dynamics (CFD) model. Under equivalence ratio of 0.4, boost ratio of 1.33 and EGR ratio of 0.4, three heat release peaks appears. Oxidation of CO which contributes 38% of total energy is considered as the main reason of the third heat release peak.
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Liu, Chunhui, Shaojie Wu e Shuo Pang. "Effects of five different parameters on biodiesel HCCI combustion in free-piston engine generator". Thermal Science 25, n. 6 Part A (2021): 4197–207. http://dx.doi.org/10.2298/tsci2106197l.
Testo completoAbstract (sommario):
A coupled 3-D CFD and detailed chemical kinetics model of free-piston engine generator (FPEG) was adopted to investigate the effects of initial parameters on homogeneous charge compression ignition (HCCI) combustion and emission. Biodiesel with 115 species skeletal mechanism was selected as fuel. Five different parameters, namely the initial pressure, the initial temperature, the working frequency, the compression ratio and the fuel equivalence ratio, were selected to analyze their influences in the HCCI combustion simulation of FPEG. The simulation results showed that the change of the five parameters had visible impact on the heat release rate of HCCI combustion, which caused the in-cylinder temperature and pressure to change, and also caused the emission content of NOx and SOOT to change obviously.