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1
Tishchenko, K. O., N. A. Brykov, and A. S. Belyaeva. "Parametric study of the influence of location and extension height of the rod interceptor on jet engine nozzle characteristics." VESTNIK of Samara University. Aerospace and Mechanical Engineering 20, no. 4 (January 19, 2022): 52–58. http://dx.doi.org/10.18287/2541-7533-2021-20-4-52-58.
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Modern aircraft need increased maneuverability to maintain a competitive position. One way to improve this characteristic is to use methods to adjust the thrust vectors of a jet engine nozzle. One method of controlling nozzle thrust is the use of nozzle interceptors devices of various shapes that extend into the nozzle channel and cause an uneven distribution of pressure along the walls of the channel. The extension of the rod interceptor near the critical section of the nozzle creates a greater lateral force than the extension of the rod near the exit section. The dependence of the lateral force on the extension height is nonlinear. The article presents a description of a nozzle interceptor of a cylindrical shape extended from the channel wall. Numerical simulation of gas flow in the nozzle with a cylindrical interceptor was carried out. The patterns of gas flow in the channel and in the environment outside the nozzle are presented. The plots of the lateral and axial components of the thrust force against the interceptor rod length are also presented for both cases of the rod location. Rod interceptors can be used in combination with other correcting devices.
2
Denisikhin, Sergey, Vladislav Emelyanov, and Konstantin Volkov. "Fluid Dynamics of Thrust Vectorable Submerged Nozzle." Fluids 6, no. 8 (August 10, 2021): 278. http://dx.doi.org/10.3390/fluids6080278.
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A numerical simulation of the gas-dynamic processes in the thrust vectorable nozzle of the solid rocket motor is considered. Construction of a geometric model and a generation of computational mesh, and reconstruction of model and mesh at each time step are discussed. Calculations of the flowfield of combustion products in the pre-nozzle chamber and nozzle block are carried out for various angles of nozzle rotation. The distributions of the gas dynamic quantities in the pre-nozzle volume corresponding to the outflow of the combustion products from the cylindrical channel and star-shaped channel are compared, as well as the solutions of the problem obtained with quasi-stationary and unsteady formulations. The effects of the channel shape on the distribution of flow quantities and formation of a vortical flow structure in the nozzle block are discussed.
3
Wang, Yang-Sheng, Jing-Lei Xu, Shuai Huang, Yong-Chen Lin, and Jing-Jing Jiang. "Experimental and numerical investigation of an axisymmetric divergent dual throat nozzle." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 234, no. 3 (August 27, 2019): 563–72. http://dx.doi.org/10.1177/0954410019872089.
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The dual throat nozzle achieves higher thrust vectoring efficiencies and lesser thrust loss than other fluidic thrust-vectoring nozzles. Separation always occurs at the bottom of the cavity with complex three-dimensional characteristics for the dual throat nozzle. In this paper, by comparing the flow structure, nozzle surface static pressure distributions and skin friction lines, which are obtained by numerical simulations and wind tunnel experiments, an axisymmetric divergent dual throat nozzle is investigated in detail. The main results show the following findings. (1) The experimental schlieren photographs confirm again that the divergent nozzle configuration has the starting problem from an intuitive perspective. Meanwhile, the flow structure and nozzle surface static pressure distributions obtained by numerical simulations are consistent with the experimental results, except for the low nozzle pressure ratios. (2) The circumferential pressure difference is negligible upstream of the separation line but obvious downstream of the separation line. The skin friction lines and nozzle surface static pressure distributions of different circumferential angles obtained by experiments both prove that the actual flow in the axisymmetric divergent dual throat nozzle indeed possesses three-dimensional characteristics. Therefore, it is necessary to utilize the full three-dimensional computational domain to study the complex three-dimensional characteristics of the flow for the axisymmetric divergent dual throat nozzle thoroughly.
4
DHAMA, Sanjeev Kumar, T. K. JINDAL, and S. K. MANGAL. "Influence of Nozzle Type, Divergence Angle and Area Ratio on Impulse of Pulse Detonation Engine." INCAS BULLETIN 12, no. 2 (June 5, 2020): 35–45. http://dx.doi.org/10.13111/2066-8201.2020.12.2.4.
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The influence of nozzle geometry on the impulse produced by the single cycle Pulse detonation engine (PDE) was experimentally investigated. For each experiment the nozzles were attached at the end of the engine. The impulse produced by the pulse detonation engine was calculated from the measured thrust. The thrust measurement was done by sliding the engine on the central bar of the thrust stand. The main structure of the basic PDE has a detonation tube with one terminal closed, a Schelkin spiral used as deflagration to detonation device, and a thrust stand to support the structure. Stoichiometric acetylene and oxygen mixture were used as detonation mixture. Various nozzles with a range of divergent angle and area ratios were tested. The calculations of the impulse were made from the thrust pulse for the duration it lasted. The effect of the type of nozzle, divergent angle and area ratio were observed. The bell shaped nozzle with large angle of divergence produced maximum specific impulse of 80 Sec with 20° divergence angle and area ratio of 6.942; maximum impulse was produced by the bell shaped nozzle with a small area ratio of 2.969 and 10° divergence angle. The maximum total impulse obtained was 1200 N-sec.
5
Xue, Fei, Gu Yunsong, Yuchao Wang, and Han Qin. "Research on control effectiveness of fluidic thrust vectoring." Science Progress 104, no. 1 (January 2021): 003685042199813. http://dx.doi.org/10.1177/0036850421998137.
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In view of the control effects of fluidic thrust vector technology for low-speed aircraft at high altitude/low density and low altitude/high density are studied. The S-A model of FLUENT software is used to simulate the flow field inside and outside the nozzle with variable control surface parameters, and the relationship between the area of control surface and the deflection effect of main flow at different altitudes is obtained. It is found that the fluidic thrust vectoring nozzle can effectively control the internal flow in the ground state and the high altitude/low density state. and the mainstream deflection angle can be continuously adjusted. The maximum deflection angle of the flow in the ground state is 21.86°, and the maximum deviation angle of the 20 km high altitude/low density state is 18.80°. The deflecting of the inner flow of the nozzle is beneficial to provide more lateral force and lateral torque for the aircraft. The high altitude/low density state is taken as an example. When the internal flow deflects 18.80°, the lateral force is 0.32 times the main thrust. For aircraft with high altitude and low density, sufficient lateral and lateral torque can make the flying aircraft more flexible, which can make up the shortcomings of the conventional rudder failure and even replace the conventional rudder surface.
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Islam, Md Shafiqul, Md Arafat Hasan, and A. B. M. Toufique Hasan. "Numerical Analysis of Bypass Mass Injection on Thrust Vectoring of Supersonic Nozzle." MATEC Web of Conferences 179 (2018): 03014. http://dx.doi.org/10.1051/matecconf/201817903014.
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High speed aerospace applications require rapid control of thrust (i.e. thrust vectoring) in order to achieve better manoeuvrability. Among the existing technologies, shock vector control is one of the efficient ways to achieve thrust vectoring. In the present study, bypass mass injection (passive control) was used to generate shock vectoring in a planar supersonic Converging-Diverging (CD) nozzle. Two diffenrent bypass lines were used to inject mass in the diverging section varying their dimension in the span wise direction (10 mm ×10 mm2 square channel and 2.68 mm×38 mm2 rectangular channel) in such a way that, the mass flow ratio in both the case remain the same (4.9%) in order to compare the effect of bypass channel dimension in the resulting thrust vector angle and thrust performance. Reynolds-averaged Navier-Stokes (RANS) equations with k-omega SST turbulence model have been implemented through numerical computations to capture the three-dimensional steady characterstics of the flow field. Results showed a significant change in the shock structure with the fromation of recirculation zone near the bypass injection port in both the case with a variation of shock structure and thrust performance for different geometry bypass lines. It was found that, thrust vector angle increases as injection length increases in the span wise direction.
7
Liu, Zhao Miao, Ying Li Xu, and Feng Shen. "Collar Length on the Performance of a Nozzle Using Fluidic Counterflow for Thrust Vectoring." Applied Mechanics and Materials 341-342 (July 2013): 524–27. http://dx.doi.org/10.4028/www.scientific.net/amm.341-342.524.
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Numerical simulation is applied to study internal flow structure and performance of counterflow thrust vectoring nozzle with collar length in zero attack angle and subsonic conditions. The changes of thrust vectoring angle, resultant thrust ratio and secondary mass flow ratios are obtained. Results indicate that the thrust vectoring angle firstly increases and then decreases with increasing suction collar length, the max of which is 5.5o; but resultant thrust ratio decreases, and its range is 0.76-0.78;During the procedure of increasing suction collar length, suction flow shifts from counterflow to coflow, and mass flow ratio decreases.
8
Lu, Yonghua, Jing Li, Xiang Zhang, and Yang Li. "The thrust measurement system research for combined nozzle in small space." Transactions of the Institute of Measurement and Control 41, no. 4 (September 19, 2018): 1149–59. http://dx.doi.org/10.1177/0142331218793485.
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For measuring the thrust of combined nozzles in satellite thruster with a small space, the test method that the nozzle directly sprays on the load baffle is employed in this paper. The key problem is how to design the positions of 10 load baffles and how to construct the measurement system. A set of complete and automatic nozzle thrust measurement system is designed and built, and the influence of the load baffle applied on the flow field of nozzles is analyzed using the software FLUENT. Furthermore, the load surface locations of the sensors for the different types of nozzles are analyzed. We draw the conclusion that the load baffle position should range from 4–8 mm for the I-type nozzle and range in 6–12 mm for II-type and III-type nozzle. The correction coefficients of the thrust forces for all channels of the measurement system are determined in the calibration experiment. The uncertainty of measurement system is estimated and the error source of the measurement system is traced. We found that the systematic uncertainty is mainly contributed by the A-type uncertainty which is related with the nozzle dimension and its inner structure. The B-type uncertainty of system is contributed by the force sensor.
9
Kordík, Jozef, and Zdeněk Trávníček. "Novel Nozzle Shapes for Synthetic Jet Actuators Intended to Enhance Jet Momentum Flux." Actuators 7, no. 3 (August 28, 2018): 53. http://dx.doi.org/10.3390/act7030053.
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An axisymmetric synthetic jet actuator based on a loudspeaker and five types of flanged nozzles were experimentally tested and compared. The first (reference) type of nozzle was a common sharp-edged circular hole. The second type had a rounded lip on the inside. The third nozzle type was assembled from these two types of nozzles—it had a rounded lip on the inside and straight section on the outside. The fourth nozzle was assembled using orifice plates such that the rounded lips were at both inner and outer nozzle ends. The last nozzle was equipped with an auxiliary nozzle plate placed at a small distance downstream of the main nozzle. The actuators with particular nozzles were tested by direct measurement of the synthetic jet (SJ) time-mean thrust using precision scales. Velocity profiles at the actuator nozzle exit were measured by a hot-wire anemometer. Experiments were performed at eight power levels and at the actuator resonance frequency. The highest momentum flux was achieved by the nozzle equipped with an auxiliary nozzle plate. Namely, an enhancement was approximately 31% in comparison with an effect of the reference nozzle at the same input power. Furthermore, based on the cavity pressure and the experimental velocity profiles, parameters for a lumped element model (mass of moving fluid and pressure loss coefficient) were evaluated. These values were studied as functions of the dimensionless stroke length.
10
Zhang, Binglong, He Liu, and Jinzhong Dong. "Research on Nozzle Jet Vector Control with Synthetic Jet Technology." International Journal of Turbo & Jet-Engines 37, no. 1 (March 26, 2020): 79–83. http://dx.doi.org/10.1515/tjj-2019-9017.
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AbstractThe synthetic jet actuator was applied to the nozzle jet vector control by experimental and numerical simulation methods to study fluid thrust vector control in this paper. The nozzle jet produced a steady and continuous deflection under the action of synthetic jet actuators. Through the analysis of the flow structure and control mechanism of the interaction between the synthetic jet and the nozzle jet, it was found that the force formed by the pressure gradient in the nozzle duct, the entrainment and ejection of the synthetic jet to the mainstream, and the momentum synthesis of the vertical synthetic jet were able to cause the deflection of the nozzle jet. The actuator excitation voltage can adjust synthetic jet velocity, which in turn affects the nozzle jet deflection angle.
11
Ling, Xuan, and Xu Dong Wang. "Application of Genetic Algorithm for Nozzle Parameters Optimization of Waterjet Propulsion System." Applied Mechanics and Materials 157-158 (February 2012): 604–7. http://dx.doi.org/10.4028/www.scientific.net/amm.157-158.604.
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Waterjet propulsion system have been increasingly used in the world due to its advantage of good maneuverability, operability, less vibration etc. The full understanding of waterjet reaction thrust is the preliminary step for the design of waterjet system. A recent research in this area is optimizing the nozzle structure of waterjet propulsion system to increase the waterjet reaction thrust as much as possible. In order to obtain the optimal parameters of nozzle, a new integrated method combining genetic algorithm with CFD simulation analysis is put forward in this paper. The integrated method will not only shorten the system design cycle, it will also develop optimization technique to realize the potential of computer based design automation. Finally, the optimal results are presented and discuss.
12
Chi, Shaoqing, Yunsong Gu, Yuhang Zhou, and Long Zhou. "Investigation of active flow control of jet deflection rate in passive secondary flow thrust vectoring nozzle." AIP Advances 12, no. 4 (April 1, 2022): 045324. http://dx.doi.org/10.1063/5.0077291.
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Jet deflection rate is an essential index in the research of thrust vector control technology. The vectoring deflection of the jet is an unsteady flow. In this study, a pulse jet actuator with adjustable frequency was used to control the flow field of the thrust vectoring nozzle. The experimental results show that the unsteady pulse jet with the same characteristic frequency as the separated bubble structure can effectively deflect and adhere to the wall. The deflection rate of the main jet is susceptible to the pulse frequency of the pulse jet, and the flow field can reach the optimal deflection rate only under the unsteady excitation of a specific frequency. The transient flow field results show that the vortex shedding frequency of the flow field can be effectively destroyed by the unsteady excitation of a specific frequency and can evenly distribute the Coanda wall pressure of the vectoring nozzle. This flow phenomenon can increase the pressure difference of the passive secondary flow, accelerate the deflection rate of the main jet, and reduce the deflection hysteresis caused by the separation bubble structure. In this study, the wall deflection rate of the thrust vectoring jet was studied by the active flow control of the unsteady pulsed jet.
13
Chi, Shaoqing, Yunsong Gu, Yuhang Zhou, and Long Zhou. "Investigation of active flow control of jet deflection rate in passive secondary flow thrust vectoring nozzle." AIP Advances 12, no. 4 (April 1, 2022): 045324. http://dx.doi.org/10.1063/5.0077291.
Full textAbstract:
Jet deflection rate is an essential index in the research of thrust vector control technology. The vectoring deflection of the jet is an unsteady flow. In this study, a pulse jet actuator with adjustable frequency was used to control the flow field of the thrust vectoring nozzle. The experimental results show that the unsteady pulse jet with the same characteristic frequency as the separated bubble structure can effectively deflect and adhere to the wall. The deflection rate of the main jet is susceptible to the pulse frequency of the pulse jet, and the flow field can reach the optimal deflection rate only under the unsteady excitation of a specific frequency. The transient flow field results show that the vortex shedding frequency of the flow field can be effectively destroyed by the unsteady excitation of a specific frequency and can evenly distribute the Coanda wall pressure of the vectoring nozzle. This flow phenomenon can increase the pressure difference of the passive secondary flow, accelerate the deflection rate of the main jet, and reduce the deflection hysteresis caused by the separation bubble structure. In this study, the wall deflection rate of the thrust vectoring jet was studied by the active flow control of the unsteady pulsed jet.
14
SHIMSHI, E., G. BEN-DOR, and A. LEVY. "Viscous simulation of shock-reflection hysteresis in overexpanded planar nozzles." Journal of Fluid Mechanics 635 (September 10, 2009): 189–206. http://dx.doi.org/10.1017/s002211200900771x.
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A computational fluid dynamics simulation of the flow in an overexpanded planar nozzle shows the existence of Mach-reflection hysteresis inside the nozzle. Previous simulations have dealt only with the flow outside the nozzle and thus concluded that the hysteresis phenomenon takes place outside the nozzle even when viscous effects are introduced. When including the geometry of the nozzle in the simulation it becomes evident that flow separation will occur before the transition from regular to Mach reflection for all relevant Mach numbers. The simulation reveals complex changes in the flow structure as the pressure ratio between the ambient and the jet is increased and decreased. The pressure along the nozzle wall downstream of the separation point is found to be less than the ambient pressure, and a modification of the Schilling curve fit is suggested for cases of extensive flow separation.
15
Yin, Yongqi, Wei Zhou, Peiyang Ma, Qingzhuang Ma, and Xueqian Shi. "Research on the Scheme of Variable Thrust Solid Rocket Motor." Journal of Physics: Conference Series 2228, no. 1 (March 1, 2022): 012041. http://dx.doi.org/10.1088/1742-6596/2228/1/012041.
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Abstract The solid rocket motor is extremely widely used due to its many advantages, but the solid rocket motor also has the disadvantage that the thrust cannot be changed. To solve this problem, there are generally two solutions to this problem. One is to use a mechanical pintle structure to change the effective cross-sectional area of the nozzle, and then to change the size of the thrust. The other is to change the effective cross-sectional area through the secondary jet method. These two methods all can change the size of the thrust, but they also have their drawbacks. The domestic team proposed a plan that combines the two methods to make up for each other’s shortcomings.
16
Shi, Wei Dong, Liang Zhang, Hai Yan He, Jiang Hai Liu, and Liang Chen. "Numerical Simulation of Two-Phase Flow inside and outside a Swirl Nozzle for Dispersing Superfine Powder." Advanced Materials Research 505 (April 2012): 170–74. http://dx.doi.org/10.4028/www.scientific.net/amr.505.170.
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In this paper, a swirl nozzle is established to disperse superfine powder aerodynamically. And Reynolds stress model (RSM) is adopted to simulate the strongly swirling, compressible and transonic gas flow in the nozzle and its rear. Combined with discrete phase model (DPM), the concentration distribution of particle group in size of 2.5μm is studied. The simulated results show that, the distribution of swirl strength is determined basically by the nozzle structure, while the total pressure has little effect on it; compared with an irrotational nozzle, the swirl nozzle could achieve a better dispersing effect for superfine powder.
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Shi, Yalin, Lingling Chen, Pengfei Chen, Qingzhen Yang, Yongqiang Shi, and Hua Yang. "Numerical Study On Aerodynamic Characteristics Of Supersonic Nozzle In Presence Of Ground Effect." Journal of Physics: Conference Series 2252, no. 1 (April 1, 2022): 012013. http://dx.doi.org/10.1088/1742-6596/2252/1/012013.
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Abstract The aeroengine mobile test bench is well applied as it is convenient for outfield transportation and installation, and also it is suitable for different environments. When utilizing a mobile test bench, the distance between the center of the engine and the ground is normally within a range so that it can be manually operated. However, this limited distance will lead to the ground effect, which affects the test performance of the aeroengine. This paper numerically studies the aerodynamic characteristics of a supersonic nozzle in the presence of the ground effect. The work is conducted with the software package ANSYS Fluent 21, employing the unsteady large eddy simulation. The nozzle works in a supersonic condition, and the distance between the nozzle and the ground is 2Dj. Dj is the diameter of the nozzle outlet. The models with and without ground effect are investigated. The analysis of the flow field confirms that the ground effect enhances the mixing of the jet and the air, and enriches the coherent structure. With the ground effect, the Reynolds stress on the vertical centerline on each section plane is increased, and the shear layer on each section plane is expanded radially. The results show that the ground effect increases the ground temperature after x/Dj=9, shortens the length of the core area by about 12.5%, decreases the mean axial velocity on the centerline of the jet after x/Dj=10, and increases the dimensionless velocity on the near ground side of the vertical plane. Here, x is the distance between the inlet plane and the discussed cross section. The analysis of the thrust characteristics confirms that the ground effect has no influence on the thrust. Therefore, the mobile test bench can accurately evaluate the thrust performance of an aeroengine.
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Shi, Yalin, Lingling Chen, Pengfei Chen, Qingzhen Yang, Yongqiang Shi, and Hua Yang. "Numerical Study On Aerodynamic Characteristics Of Supersonic Nozzle In Presence Of Ground Effect." Journal of Physics: Conference Series 2252, no. 1 (April 1, 2022): 012013. http://dx.doi.org/10.1088/1742-6596/2252/1/012013.
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Abstract The aeroengine mobile test bench is well applied as it is convenient for outfield transportation and installation, and also it is suitable for different environments. When utilizing a mobile test bench, the distance between the center of the engine and the ground is normally within a range so that it can be manually operated. However, this limited distance will lead to the ground effect, which affects the test performance of the aeroengine. This paper numerically studies the aerodynamic characteristics of a supersonic nozzle in the presence of the ground effect. The work is conducted with the software package ANSYS Fluent 21, employing the unsteady large eddy simulation. The nozzle works in a supersonic condition, and the distance between the nozzle and the ground is 2Dj. Dj is the diameter of the nozzle outlet. The models with and without ground effect are investigated. The analysis of the flow field confirms that the ground effect enhances the mixing of the jet and the air, and enriches the coherent structure. With the ground effect, the Reynolds stress on the vertical centerline on each section plane is increased, and the shear layer on each section plane is expanded radially. The results show that the ground effect increases the ground temperature after x/Dj=9, shortens the length of the core area by about 12.5%, decreases the mean axial velocity on the centerline of the jet after x/Dj=10, and increases the dimensionless velocity on the near ground side of the vertical plane. Here, x is the distance between the inlet plane and the discussed cross section. The analysis of the thrust characteristics confirms that the ground effect has no influence on the thrust. Therefore, the mobile test bench can accurately evaluate the thrust performance of an aeroengine.
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Semlitsch, Bernhard, and Mihai Mihăescu. "Evaluation of Injection Strategies in Supersonic Nozzle Flow." Aerospace 8, no. 12 (November 29, 2021): 369. http://dx.doi.org/10.3390/aerospace8120369.
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The ability to manipulate shock patterns in a supersonic nozzle flow with fluidic injection is investigated numerically using Large Eddy Simulations. Various injector configurations in the proximity of the nozzle throat are screened for numerous injection pressures. We demonstrate that fluidic injection can split the original, single shock pattern into two weaker shock patterns. For intermediate injection pressures, a permanent shock structure in the exhaust can be avoided. The nozzle flow can be manipulated beneficially to increase thrust or match the static pressure at the discharge. The shock pattern evolution of injected stream is described over various pressure ratios. We find that the penetration depth into the supersonic crossflow is deeper with subsonic injection. The tight arrangement of the injectors can provoke additional counter-rotating vortex pairs in between the injection.
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Bi, Xiaobo, and Qiang Zhu. "Role of internal flow in squid-inspired jet propulsion." Physics of Fluids 34, no. 3 (March 2022): 031906. http://dx.doi.org/10.1063/5.0085679.
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We numerically investigate the dynamics of a self-propelled system that swims by using intermittent jet propulsion through cyclic body deformations. Unlike existing studies, the focus of the current work is on characteristics of internal flow field and its effect on the thrust generation and energetics of the system. Our results indicate that the inertia of the internal flow plays a minor role in thrust generation in comparison with the momentum flux and the normal stress at the nozzle. By examining the energy pathways in both inflation (recovery) and deflation (power) phases, we illustrate that the energy dissipation inside the pressure chamber occurs mostly in the inflation phase, during which the energy transferred from the solid structure to the fluid is mostly damped out and wasted. Based on this analysis, we propose a novel performance enhancement method by using a variable nozzle to reduce the energy waste in the inflation phase. In a sample case, this strategy not only increases the propulsive efficiency by 118% but also increases the forward speed by 25%. Furthermore, we have studied the effect of solid structures inside the pressure chamber. Our results suggest these structures cause a decline in the efficiency, especially if they are close to the nozzle.
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He, Shanshan, Yi Qian, Wenliang Xue, and Longdi Cheng. "Numerical Simulation of Flow Field in Air-Jet Loom Main Nozzle." Autex Research Journal 19, no. 2 (June 1, 2019): 181–90. http://dx.doi.org/10.1515/aut-2018-0053.
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Abstract To improve airflow injection capacity of the main nozzle and decrease backflow phenomenon, a new main nozzle structure with two throats is designed. Negative pressure value and negative pressure zone length are first proposed evaluating the strength of backflow phenomenon. Commercial computational fluid dynamic (CFD) code “Fluent” is performed to simulate the flow field inside and outside the main nozzle. Exit velocity increases about 10 m/s in new main nozzle. Airflow core length of the new main nozzle is 35% higher than that of commonly used main nozzle. Smaller negative pressure value and shorter negative pressure zone length mean a weaker backflow phenomenon in the new main nozzle. Bigger air drag force indicates stronger weft insertion ability in the new main nozzle.
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Noaman, H. R., Hai Bin Tang, and Elsayed Khalil. "Numerical Simulation on the Influence of Injection Location, Injection Angle, and Divergence Half Angle on SITVC Nozzle Flow Field." International Journal of Aerospace Engineering 2019 (March 14, 2019): 1–16. http://dx.doi.org/10.1155/2019/7392497.
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A numerical study has been performed to characterize the nozzle flow field of secondary injection thrust vector control (SITVC) and to estimate the performance parameters of SITVC. After validating the CFD turbulence models with an experimental data, a numerical simulation has been conducted in order to investigate the influence of changing the injection location, the injection angle, and the primary nozzle divergence half angle on the SITVC nozzle flow field structure and on the SITVC performance parameters. The secondary mass flow rate was kept constant for all cases during the simulation. The results showed that downstream injection near the nozzle exit Mp=2.75 increases the high-pressure zone upstream the injection leading to an increase in the side force; also, the higher divergence half angle 15° slightly increases the side force and it provides a wide range of deflection without shock impingement on the opposite wall becoming more effective for SITVC. The injection angle in the upstream direction 135° increases the side force, and by decreasing the injection angle to downstream direction 45°, the side force decreases. However, the SITVC performance parameters and the flow field structure are more influenced by the injection location and the primary nozzle divergence half angle while being less influenced by the injection angle.
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Moon, Heejang, Seongjoo Han, Youngjun You, and Minchan Kwon. "Hybrid Rocket Underwater Propulsion: A Preliminary Assessment." Aerospace 6, no. 3 (March 6, 2019): 28. http://dx.doi.org/10.3390/aerospace6030028.
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This paper presents an attempt to use the hybrid rocket for marine applications with a 500 N class hybrid motor. A 5-port high density polyethylene (HDPE) fuel grain was used as a test-bed for the preliminary assessment of the underwater boosting device. A rupture disc preset to burst at a given pressure was attached to the nozzle exit to prevent water intrusion where a careful hot-firing sequence was unconditionally required to avoid the wet environment within the chamber. The average thrust level around 450 N was delivered by both a ground test and an underwater test using a water-proof load cell. However, it was found that instantaneous underwater thrusts were prone to vibration, which was due in part to the wake structure downstream of the nozzle exit. Distinctive ignition curves depending on the rupture disc bursting pressure and oxidizer mass flow rate were also investigated. To assess the soft-start capability of the hybrid motor, the minimum power thrust, viewed as the idle test case, was evaluated by modulating the flow controlling valve. It was found that an optimum valve angle, delivering 16.3% of the full throttle test case, sustained the minimum thrust level. This preliminary study suggests that the throttable hybrid propulsion system can be a justifiable candidate for a short-duration, high-speed marine boosting system as an alternative to the solid underwater propulsion system.
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Cao, Li Ping, Shi Liu, Yao Song Huang, Qian Liu, and Zhi Hong Li. "Study of High-Pressure Waterjet Characteristics Based on CFD Simulation." Applied Mechanics and Materials 224 (November 2012): 307–11. http://dx.doi.org/10.4028/www.scientific.net/amm.224.307.
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Nozzle spacing is an important factor influencing the effect of high-pressure water jet cleaning. When the nozzle incidence angle, the deflection angle and the target distance are determined, the size of the nozzle spacing determines the overlap of the water jet, the overlap is too large or too small will reduce the cleaning effect. In this paper ,using CFD software to simulate the flow field inside and outside of the high-pressure water jet nozzle, analysis the jet axial velocity, pressure distribution, and discussed this changes in the case of different spacing between the nozzles when the nozzle structure are same, and choose an reasonable spacing to ensure the cleaning effect.
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Volkov, K. N., V. N. Emelyanov, and M. S. Yakovchuk. "Flow Structure and Thrust Change at Gas Jet Injection into the Supersonic Part of a Nozzle." Technical Physics 64, no. 3 (March 2019): 317–23. http://dx.doi.org/10.1134/s1063784219030265.
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Bae, Dae Seok, Hyun Ah Choi, Ho Dong Kam, and Jeong Soo Kim. "A Computational Study on the Shock Structure and Thrust Performance of a Supersonic Nozzle with Overexpanded Flow." Journal of the Korean Society of Propulsion Engineers 18, no. 4 (August 1, 2014): 1–8. http://dx.doi.org/10.6108/kspe.2014.18.4.001.
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Qiao, Xu, Liu, and Wang. "Study on the Horizontal Axis Deviation of a Small Radius TBM Tunnel Based on Winkler Foundation Model." Applied Sciences 10, no. 3 (January 22, 2020): 784. http://dx.doi.org/10.3390/app10030784.
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During the construction stage of the small radius TBM (tunnel boring machine) interval, the improper control of the boring parameters and the boring posture can cause the horizontal axis deviation of the shield tunnel. In order to address this issue, the TBM segments lining structure of the small radius interval is simplified as the continuous circular curved beam based on the longitudinal equivalent continuous model and Winkler elastic foundation beam theory. The theoretical model is solved through the transfer matrix method, and its applicability is verified by comparing it with the field monitoring data. It is found that the horizontal axis deviation of the completed tunnel increases with the total jack thrust, and the lateral displacement tends to be stable when the distance between the ring and the tail is far. The horizontal axis deviation has a negative relationship with the thrust difference or path difference when the jack thrust in the outside of the shield curve is larger than that of inside the shield curve. The horizontal axis deviation has a positive relationship with the thrust difference or path difference when the jack thrust in the outside of the shield curve is smaller than that of inside the shield curve.
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Fani Saberi, Farhad, Mansour Kabganian, Hamed Kouhi, and Morteza Shahravi. "Gimbaled-thruster based nonlinear attitude control of a small spacecraft during thrusting manoeuvre." Aeronautical Journal 121, no. 1241 (June 13, 2017): 983–1004. http://dx.doi.org/10.1017/aer.2017.51.
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ABSTRACTIn this paper, a novel thrusting manoeuvre control scheme is proposed for a small spacecraft which is based only on the gimbaled thrust vector control (TVC) system. The spacecraft structure is composed of a body and a gimbaled thruster where common attitude control systems such as reaction control system (RCS) and spin stabilisation are not employed. A nonlinear two-body model is considered for the characterisation of the gimbaled-nozzle spacecraft where the gimbal actuator provides the only active control input. The spacecraft attitude is affected by a large exogenous disturbance torque which is generated by a thrust vector misalignment from the centre of mass (CM). To achieve some performance goals in the both transient and steady-state modes, a new control scheme is derived based on the combination of two linear and nonlinear controllers. The proposed method ensures the attitude and thrust vector stability during an impulsive orbital manoeuvre while eliminating and rejecting an exogenous disturbance torque. The numerical simulations illustrate the applicability of this method for using in a small spacecraft and its efficiency in sustained operation.
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Xie, Yonghui, Kun Lu, Di Zhang, and Gongnan Xie. "Computational Analysis of Propulsion Performance of Modified Pitching Motion Airfoils in Laminar Flow." Mathematical Problems in Engineering 2014 (2014): 1–13. http://dx.doi.org/10.1155/2014/420436.
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The thrust generation performance of airfoils with modified pitching motion was investigated by computational fluid dynamics (CFD) modeling two-dimensional laminar flow at Reynolds number of 104. The effect of shift distance of the pitch axis outside the chord line(R), reduced frequency(k), pitching amplitude(θ), pitching profile, and airfoil shape (airfoil thickness and camber) on the thrust generated and efficiency were studied. The results reveal that the increase inRandkleads to an enhancement in thrust generation and a decrease in propulsive efficiency. Besides, there exists an optimal range ofθfor the maximum thrust and the increasingθinduces a rapid decrease in propulsive efficiency. Six adjustable parameters(K)were employed to realize various nonsinusoidal pitching profiles. An increase inKresults in more thrust generated at the cost of decreased propulsive efficiency. The investigation of the airfoil shape effect reveals that there exists an optimal range of airfoil thickness for the best propulsion performance and that the vortex structure is strongly influenced by the airfoil thickness, while varying the camber or camber location of airfoil sections offers no benefit in thrust generation over symmetric airfoil sections.
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Deng, Yicheng, Xianyin Leng, Wei Guan, Zhixia He, Wuqiang Long, Shengli Wei, and Jie Hu. "A numerical study on the in-nozzle cavitating flow and near-field atomization of cylindrical, V-type, and Y-type intersecting hole nozzles using the LES-VOF method." Green Processing and Synthesis 11, no. 1 (January 1, 2022): 129–42. http://dx.doi.org/10.1515/gps-2022-0015.
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Abstract In order to improve the performance of engines fueled with diesel fuel or diesel-like e-fuels so as to realize greener transportation, the V-type and Y-type intersecting hole nozzles, in which each hole is formed by the coalescence of two or three subholes, have been designed. In this article, the multiphase flow inside and outside the nozzle was numerically investigated using a volume-of-fluid large eddy simulation (VOF-LES) method to clarify the effects of the nozzle structure on the cavitating flow and primary atomization characteristics. The calculation was carried out at an injection pressure of 150 MPa and a back pressure of 0.1 MPa. Numerical results showed that unlike the L-shape pressure distribution along a cylindrical hole, for intersecting type hole nozzles, the pressure showed a stepped shape drop along the holes due to the overall convergent hole structure, which restrained the inception of cavitation. Consequently, the global loss of the flow over an intersecting type hole nozzle was lower by 24–37% than those of a cylindrical hole nozzle. Additionally, the jets emerging from the intersecting hole nozzles showed 50% wider spreading angles and 27% smaller droplet sizes than those of the cylindrical hole nozzle. Furthermore, the jets emerging from a Y-type intersecting hole nozzle showed enhanced atomization, which was found to be due to the unstable air suction near the outlets of this type of nozzle hole.
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Wang, Zhi Jian, and Xiao Feng Shang. "Gas-Solid Two-Phase Flow Simulation of Coaxial Powder Delivery Nozzle in Rapid Prototyping." Applied Mechanics and Materials 29-32 (August 2010): 1663–67. http://dx.doi.org/10.4028/www.scientific.net/amm.29-32.1663.
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Coaxial powder delivery nozzle plays an important role in metal part direct and rapid prototyping technology and the reasonable structure can ensure uniform and stable flow of metal powder. Gas-solid two-phase flow theory is considered to simulate outside flow field of carrying gas-type coaxial powder delivery nozzle. The physical and mathematical models are erected. FLUENT software is used to simulate the velocity distribution of gas and solid particle, the volume fraction distribution of particle and the focusing properties. The simulative results indicate that both the structure of coaxial powder delivery nozzle and inlet velocity affect the convergence of powder. When the metal powder is only driven by the carrying gas without the shield gas flow, the powder appears focusing and the focus is 8mm far from the nozzle exit, but the volume fraction at the focus is only 2.6 percent, which shows the convergence of powder is not good and the usage rate is not high. In the optimized structure the simulative results show that the powder flow is affected by the flow of shield gas. When the velocity of shield gas is 6m/s, the powder shows good convergence and the volume fraction of powder at the focus reaches 3.3 percent. The higher the velocity of shield gas is, the more uniformly the powder flows, but the volume fraction at the focus is slightly lower. It is obvious that the numerical simulation will benefit for coaxial nozzle designing and performance improving.
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Hui, Wei Hua, Fu Ting Bao, Hai Feng Hu, and Yang Liu. "Research on the Thermal Buckling Analysis of the Attitude Liquid Rocket Engine with Film Cooling." Applied Mechanics and Materials 390 (August 2013): 714–19. http://dx.doi.org/10.4028/www.scientific.net/amm.390.714.
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A method which couples thermal and structure analysis has been efficiently implemented to investigate the buckling characteristics of the attitude liquid rocket engine with film cooling. It employs a model which is based on heat transfer of film cooling and introduces an integrated analysis methodology. The results indicate that the maximum wall temperature takes place at the throat of the nozzle, and the maximum wall stress appears at the place having the greatest temperature gradient. Moreover instability of the thrust chamber with big expanding ratio and thin thickness will happen under certain external pressure and the critical buckling loads is higher than the results without thermal load. These conclusions are reliable and should benefit rocket design.
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Yang, Xiao Dong, Jun Peng Shao, Xiao Qiu Xu, Yun Fei Wang, Chao Yin, and Hui Jiang. "Research on Velocity Influence on Thermal Deformation Field of Heavy Hydrostatic Thrust Bearing." Advanced Materials Research 129-131 (August 2010): 968–72. http://dx.doi.org/10.4028/www.scientific.net/amr.129-131.968.
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According to the structure of workbench and base of heavy hydrostatic bearing which is applied in heavy equipment, thermal deformation equations of the structure are deduced and boundary conditions for numerical simulation are established based on thermal elasticity theory. Then thermal deformation of hydrostatic bearing without load is calculated at different velocity. The results indicate that: temperature and velocity impacts a significant influence on thermal deformation of hydrostatic bearing. Thermal deformation increases as the velocity increases; workbench up-warps severely, oil-pad inclines towards outside to a certain extent, which results in the lubrication clearance emerges as wedge-shape deformation. The conclusions from thermal deformation calculation could provide theoretical basis for structure design of hydrostatic bearing and ravel out the thermal deformation problem.
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Liu, Zong Zheng, Bo Zhao, Zhen Hua Chen, and Cheng Guo Yu. "Research on Thermal Protection of One Gas Generator." Advanced Materials Research 945-949 (June 2014): 1050–53. http://dx.doi.org/10.4028/www.scientific.net/amr.945-949.1050.
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The thermal protection is a key factor to keep the gas generator work longtime under high temperature condition steadily. The main heat transfer paths are analyzed. A numeral simulation of the combustor and its nozzle shows the pipe outside temperature distribution with the change of time, position and thickness. According to the numeral simulation results, two thermal protection measures are bring forward, reduce the temperature, choosing proper thickness and heat resisting material. At last, an experiment results validate that the numeral simulation is credibility; the improvement of the structure is effective. With a longtime run, the outside wall temperature is 870K, which satisfies the operation needs.
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Deng, W., C. Zhao, L. Chen, and R. Zhang. "Simulation and Experiment of a Designed Anti-Drift Spray Nozzle." Advances in Animal Biosciences 8, no. 2 (June 1, 2017): 837–41. http://dx.doi.org/10.1017/s2040470017001340.
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This paper reports an investigation of the relationship between spray characteristics and a nozzles’ internal structure to reveal the working mechanism of anti-drift spray nozzles. Three important structural factors were taken into account, the diameter of the inner chamber, the angle of V-shaped slot and the relative kerf depth. Three-dimensional models of the fan nozzles were set up using Solidworks software and the corresponding real nozzles were produced using high-precision 3-D printer. The flow fields inside the nozzles were simulated using the software FLUENT. By comparing the flow fields inside and outside the nozzles under the conditions of the same inner structural parameter, the relationships between spraying flow characteristics and different structural parameters was made clear, and provides a reference for optimal design of anti-drift spray nozzles.
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Benderradji, Razik. "Effect of the fluidic injection on the flow of a converging-diverging conical nozzle." International Journal of Energetica 5, no. 1 (July 6, 2020): 07. http://dx.doi.org/10.47238/ijeca.v5i1.114.
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The flow in an Over-Expanded Nozzle is subjected to shock waves leading to the unsteady separation of the boundary layer. Free detachment may be followed by a restricted detachment. During the expansion regime in propellant nozzles, several physical phenomena are encountered: supersonic jet, jet separation, adverse pressure gradient, shock wave, turbulent boundary layer, highly compressible mixture layer, return flow, large scale turbulence. These very complex phenomena can considerably affect the performance of the nozzle.The numerical investigation was performed by the CFD-FASTRAN search code, using the k-w SST model as the turbulence model. The calculation is performed by solving the Navier-Stokes equations of two-dimensional compressible turbulent flow. It is based on the study of the fluidic vectorization phenomenon of the thrust of a double-injection convergent-divergent supersonic conical nozzle. The study is based on the effect of the ratio of NPR pressures with SPR = 1 on the overall structure of shock waves. The calculation is highlighting the behavior of a flow that has not neglected. In particular, the appearance of the separation zone formed by the fluid jet and the deflection of the main jet cause separation shocks.
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Gan, Hui, Kun Yu Yang, and Xiao Liang Yang. "Analysis of Structure Characteristics and Improvement of Turbo-Supercharger Bearing." Applied Mechanics and Materials 496-500 (January 2014): 707–10. http://dx.doi.org/10.4028/www.scientific.net/amm.496-500.707.
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The reliability of the gas turbo-supercharger can be affected by the faults such as the cauterization of the floating bearing of the supercharger, the carbonization of the rotor and getting stuck, the deformation of the blade and heat cracking of the nozzle ring. The design scheme is proposed by using friction bearing taking the place of the floating bearing, because the main reason of the cauterization of the bearing is the increase of the inside clearance of the floating sleeve, which is testified by the actual rpm measurement of the floating sleeve on the floating bearing and the adjustment test of the inside and outside clearances of the bearing. The experimental study on the structural characteristics of turbocharger bearing effectively prevents turbo-supercharger floating bearing from being cauterized, solves the problem of thermal fatigue damage, and improves turbocharger reliability.
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Xie, Y., C. Zhong, D. F. Ruan, K. Liu, and B. Zheng. "Effect of Core Flow Inlet Swirl Angle on Performance of Lobed Mixing Exhaust System." Journal of Mechanics 32, no. 3 (March 16, 2016): 325–37. http://dx.doi.org/10.1017/jmech.2016.1.
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AbstractGeometric model of a lobed mixing exhaust system is created and its flow field is simulated by using the steady Reynolds Averaged Navier-Stokes (RANS) equations under the condition of different core flow inlet swirl angles. According to the numerical simulation results, due to the guidance effect of the lobe parallel side wall, the structure and vorticity of streamwise vortices change little near the lobe exit with inlet swirl angle, and it is the same with the thermal mixing efficiency. As the flow develops, although the inlet swirl angle has limited influence on the streamwise vorticity, it greatly affects the structure of streamwise vortices. It causes the thermal mixing efficiency to increase with the swirl angle. As for the total pressure recovery coefficient, it falls slightly when the inlet swirl strengthens. At the nozzle exit, the total pressure recovery coefficient of CFISA = 30° model is 0.5% lower than CFISA = 0° model. Moreover, as the inlet swirl strengthens, the thrust fall of lobed mixing exhaust system gradually accelerates, especially when the inlet swirl angle is over 15°.
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Turki, Yosra, Malek Habak, Raphael Velasco, Jean Noel Laurent, and Pascal Vantomme. "An Experimental Study of Drilling Parameters Effect on Composite Carbon/Epoxy Damage." Key Engineering Materials 554-557 (June 2013): 2038–46. http://dx.doi.org/10.4028/www.scientific.net/kem.554-557.2038.
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The main purpose of composite materials drilling is the need to put together different parts of a structure, in aeronautics for example. The objective of this study is to experimentally analyze the influence of drilling on a carbon/epoxy composite. Three geometries of drill, a range of cutting speed and feed have been tested. Thrust forces and moments have been recorded during machining and macroscopic analyses have been conducted to examine outside and inside surfaces of the holes. Damages have been also quantified using delamination factor Fd. Experimental results have shown significant influences of feed and drill geometry on delamination and the best results have been obtained using a spur drill.
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Schwicker, Maurice, and Nikolay Nikolov. "Development of Tensile Test Specimens for Fused Deposition Modeling." Materials Science Forum 1058 (April 5, 2022): 175–82. http://dx.doi.org/10.4028/p-24e2wo.
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Standard test specimens are usually used to determine the tensile strengths of plastics. Their shape assumes that the material is homogeneous and only normal stress occur inside their nominal length. Unlike injection molding, which is a common technology to produce plastic parts, the structure of additively manufactured parts is not homogeneous. In areas with variable geometry, an additional internal stress concentration occurs, which often leads to failure of the test specimens outside their nominal length, which in turn compromises the tensile test. The stress concentration increases with the nozzle diameter used. This requires improvement of the test specimens shape. In the present work a new form of the test specimens is proposed, in accordance with the peculiarities of the Fused Deposition Modeling (FDM) process. A series of test specimens have been produced, using a 1mm and 2mm nozzle as well as one wall, no walls and milled specimens with newly developed geometry. All specimens were tensile tested and the results were shown and compared. It has been found that the proposed new shape ensures failure within the parallel length for successful testing, provided infill strands are correctly positioned.
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Wicker, Ryan B., and John K. Eaton. "Effect of Injected Longitudinal Vorticity on Particle Dispersion in a Swirling, Coaxial Jet." Journal of Fluids Engineering 121, no. 4 (December 1, 1999): 766–72. http://dx.doi.org/10.1115/1.2823535.
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A Passive particle dispersion control technique was investigated in which longitudinal vortices were injected into a developing coaxial swirling jet with sufficient annular swirl for flow recirculation to occur. Four vortex generators, separated by 90 degrees and placed along the outside of the annular nozzle, injected vorticity opposite in sign to the mean swirl, significantly altering the structure of the swirling jet. The injected vorticity competed with the mean swirl to reduce azimuthal particle flinging and to disrupt the development of the vortex rings in the outer shear layer. Axial flow visualization showed the formation of axial structures at the forcing frequency but considerable azimuthal asymmetry. Horizontal cross sections showed a four-lobed structure which persisted in the natural jet for at least eight inner jet diameters. The particle concentration field was measured using digital processing of pulsed laser sheet images. Outward radial particle dispersion reduced while inward dispersion toward the jet centerline increased indicating that the injected vorticity sufficiently reduced particle flinging by large-scale vortices.
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ANDRIOTIS, A., M. GAVAISES, and C. ARCOUMANIS. "Vortex flow and cavitation in diesel injector nozzles." Journal of Fluid Mechanics 610 (August 8, 2008): 195–215. http://dx.doi.org/10.1017/s0022112008002668.
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Flow visualization as well as three-dimensional cavitating flow simulations have been employed for characterizing the formation of cavitation inside transparent replicas of fuel injector valves used in low-speed two-stroke diesel engines. The designs tested have incorporated five-hole nozzles with cylindrical as well as tapered holes operating at different fixed needle lift positions. High-speed images have revealed the formation of an unsteady vapour structure upstream of the injection holes inside the nozzle volume, which is referred to as ‘string-cavitation’. Computation of the flow distribution and combination with three-dimensional reconstruction of the location of the strings inside the nozzle volume has revealed that strings are found at the core of recirculation zones; they originate either from pre-existing cavitation sites forming at sharp corners inside the nozzle where the pressure falls below the vapour pressure of the flowing liquid, or even from suction of outside air downstream of the hole exit. Processing of the acquired images has allowed estimation of the mean location and probability of appearance of the cavitating strings in the three-dimensional space as a function of needle lift, cavitation and Reynolds number. The frequency of appearance of the strings has been correlated with the Strouhal number of the vortices developing inside the sac volume; the latter has been found to be a function of needle lift and hole shape. The presence of strings has significantly affected the flow conditions at the nozzle exit, influencing the injected spray. The cavitation structures formed inside the injection holes are significantly altered by the presence of cavitation strings and are jointly responsible for up to 10% variation in the instantaneous fuel injection quantity. Extrapolation using model predictions for real-size injectors operating at realistic injection pressures indicates that cavitation strings are expected to appear within the time scales of typical injection events, implying significant hole-to-hole and cycle-to-cycle variations during the corresponding spray development.
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Rajesh, T. N., T. J. S. Jothi, and T. Jayachandran. "Preliminary Studies on Non-Reactive Flow Vortex Cooling." Recent Patents on Mechanical Engineering 12, no. 3 (September 26, 2019): 262–71. http://dx.doi.org/10.2174/2212797612666190510115403.
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Background: The impulse for the propulsion of a rocket engine is obtained from the combustion of propellant mixture inside the combustion chamber and as the plume exhausts through a convergent- divergent nozzle. At stoichiometric ratio, the temperature inside the combustion chamber can be as high as 3500K. Thus, effective cooling of the thrust chamber becomes an essential criterion while designing a rocket engine. Objective: A new cooling method of thrust chambers was introduced by Chiaverni, which is termed as Vortex Combustion Cold-Wall Chamber (VCCW). The patent works on cyclone separators and confined vortex flow mechanism for providing high propellant mixing with improved degree of turbulence inside the combustion chamber, providing the required notion for studies on VCCW. The flow inside a VCCW has a complex structure characterised by axial pressure losses, swirl velocities, centrifugal force, flow reversal and strong turbulence. In order to study the flow phenomenon, both the experimental and numerical investigations are carried out. Methods: In this study, non-reactive flow analysis was conducted with real propellants like gaseous oxygen and hydrogen. The test was conducted to analyse the influence of mixture ratio and injection pressure of the propellants on the chamber pressure in a vortex combustion chamber. A vortex combustor was designed in which the oxidiser injected tangentially at the aft end near the nozzle spiraled up to the top plate and formed an inner core inside the chamber. The fuel was injected radially from injectors provided near the top plate and the propellants were mixed in the inner core. This resulted in enhanced mixing and increased residence time for the fuel. More information on the flow behaviour has been obtained by numerical analysis in Fluent. The test also investigated the sensitivity of the tangential injection pressure on the chamber pressure development. Results: All the test cases showed an increase in chamber pressure with the mixture ratio and injection pressure of the propellants. The maximum chamber pressure was found to be 3.8 bar at PC1 and 2.7 bar at PC2 when oxidiser to fuel ratio was 6.87. There was a reduction in chamber pressure of 1.1 bar and 0.7 bar at PC1 and PC2, respectively, in both the cases when hydrogen was injected. A small variation in the pressure of the propellant injected tangentially made a pronounced effect on the chamber pressure and hence vortex combustion chamber was found to be very sensitive to the tangential injection pressure. Conclusion: VCCW mechanism has been to be found to be very effective for keeping the chamber surface within the permissible limit and also reducing the payload of the space vehicle.
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Jeon, Seok Hyeon, Kwang-Il Cho, Jungwon Huh, and Jin-Hee Ahn. "The Performance Assessment of a Precast, Panel-Segmented Arch Bridge with Outriggers." Applied Sciences 9, no. 21 (November 1, 2019): 4646. http://dx.doi.org/10.3390/app9214646.
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Stone arch bridges, which are globally implemented, are advantageous with respect to material strength and durability. To minimize environmental damage from arch bridges, a structurally stable scheme that can resist variable external loads is required. This paper proposes a segmented precast arch bridge with outriggers to resist both the tensile force applied on the precast panels and the compressive force during construction and use. To assess the structural behavior and safety of the proposed arch bridge, a three-dimensional (3D) nonlinear structural analysis was conducted, considering the construction step and rise ratio of the arch bridge. The structural analysis of the proposed arch bridge revealed that its maximum horizontal and vertical displacements occurred at the support of the precast panel and the arch crown in a self-weight state. However, because of the compressive resistance characteristics of the outriggers connected to the precast panels, the structure demonstrated an effective performance in the self-weight state. With an increase in the construction steps, and the final completion of proposed arch bridge via installation of the precast arch segments and earthwork for the precast arch bridge with outriggers, the deformation of the arch members was mitigated, and the relative difference between the stress distributions of the members reduced. Hence, the arch bridge achieved structural stability. Based on the thrust line analysis results of the arch bridge with respect to the construction step using 3D structural analysis results, the thrust line was formed outside the precast panel at the arch crown and support, so was attributed to the behavior of the arch bridge in a self-weight state. The thrust line was found to act within the precast panel depending on the construction step. Analysis results confirmed that the behavior of the precast panel arch bridge with the proposed outrigger was stable and structurally effective.
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Kujawiak, Sebastian, Małgorzata Makowska, and Jakub Mazurkiewicz. "The Effect of Hydraulic Conditions in Barbotage Reactors on Aeration Efficiency." Water 12, no. 3 (March 6, 2020): 724. http://dx.doi.org/10.3390/w12030724.
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Barbotage reactors such as airlift reactors (ALR) and bubble column reactors (BCR), due to their two-phase flow systems, were investigated in many research papers. In their basic design variants, they are typically used to lift, mix, and aerate liquids, while, when equipped with additional elements in hybrid variants, their individual properties, i.e., lifting, mixing, and aeration of liquids, can significantly change with the same reactor geometry. The object of this study was to develop a hybrid barbotage reactor in various structural design variants. The structure consisted of a barbotage column of 50 mm in diameter, used to transport a water–air mixture outside the reactor (so-called external loop). The installation was additionally equipped with a nozzle in order to improve mixture aeration and circulation efficiency. The nozzle was mounted at various heights of the column pump segment. Additionally, the reactor was equipped with s moving bed in two variants (20% and 40% reactor capacity) in order to determine its effect on the mixture aeration and circulation conditions. Based on the measurement results, aeration curves were prepared for various structural design and column packing variants of the reactor. Properties of the two-phase mixture were determined for both parts—ALR and BCR. Technological and energy parameters of the aeration process were calculated, and the results obtained for the individual structural design variants were compared. It was found that, for the most advantageous design, in terms of aeration efficiency, the aeration nozzle should be placed in the mid-length of the pump segment of the barbotage column, irrespective of the hybrid reactor packing rate with the moving bed. The reactor packing with the moving bed resulted in a decreased mean water velocity in the reactor. For most analyzed structural design variants, the respective packing with the moving bed had no significant effect on aeration efficiency. Only for one structural design variant did the lack of packing significantly improve oxygen levels by as much as approximately 41%.
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Qu, Huajie, Chendong Liu, Lei Zhang, Jianjun Qu, and Baoyu Song. "A Longitudinal-Bending Hybrid Linear Ultrasonic Motor and Its Driving Characteristic." Shock and Vibration 2022 (January 6, 2022): 1–14. http://dx.doi.org/10.1155/2022/5701014.
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As a new type of driver, linear ultrasonic motor (LUSM) is widely used in the high-tech field because of its low speed, high thrust, low noise, and no electromagnetic interference. However, as an actuator used in microdevices, most of the existing LUSMs are large in size and not compact in structure. In order to overcome these limitations, a new structure of linear ultrasonic motor’s stator is developed in this paper. The stator is similar to a tuning fork structure, which is divided into three parts: two driving feet, two driving legs, and the driving body. By using the first-order longitudinal vibration mode of the whole stator and the unique partial second-order bending vibration mode of the driving legs to achieve vibration mode degeneracy, a mode hybrid linear ultrasonic motor that is easy to miniaturize is proposed. Its working principle is analyzed. The dynamic analysis of the stator is carried out by using finite element software. The structure dimension of the stator and the driving frequency under the working mode are determined. At the same time, the feasibility of driving feet synthesizing elliptical motion is verified theoretically and experimentally. In addition, the LUSM test setup is built. The effects of driving frequency and Vpp on stator stall force and average velocity are studied. The results show that the maximum stall force can reach 99 mN, and the average velocity of the motor is 88.67 mm/s with Vpp = 320 V and driving frequency 80.2 kHz. The proposed LUSM is appropriate for use in occasions with quick return characteristics, like the controlling valve or nozzle of the printer. The research results provide guidance for the stator design of the linear ultrasonic motor.
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ABILKHASIMOV, Kh B. "TYPE DESIGNS OF THE PALEOZOIC COMPLEX SECTIONS OF THE EAST EDGE OF THE PERI-CASPIAN DEPRESSION." Neft i gaz 1, no. 121 (April 15, 2020): 6–24. http://dx.doi.org/10.37878/2708-0080/2021-1.01.
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The present article highlights the features of the geological structure, sedimentation conditions and the influence tectonic evolution factors on the petroleum potential within the eastern edge of the Precaspian basin. According to the features of the geological structure and lithological characteristics of the sedimentary formations of the eastern edge of the Precaspian basin, different facies zones can be distinguished, corresponding to the distinguished structural-formational zones with several types of Paleozoic sections. НЕФТЬ И ГАЗ 2021 1 (121) 7 ГЕОЛОГИЯ Based on the comparison of the Paleozoic sections for the eastern edge of the Precaspian basin it is concluded that collision tectonics was the major factor for sedimentation. Vertical facies succession influenced by tectonics and sea level fluctuations. Carbonate platforms played an important role in the distribution of sedimentary material and controlled the depth of the sea, which influenced on the composition and texture of the rocks. The presence of carbonate platforms was also reflected in the reduced thickness of the Lower Permian sediments, which are less presented within the carbonate platforms stratigraphic section comparing to the adjacent relatively deep-water areas located to the west outside the carbonate platforms. The structure of carbonate platforms was to the largest extent defined by the thrust tectonics and that controlled the distribution of oil and gas fields and potential traps.
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Chu, Xiangcheng, Mengfan Zhang, Songmei Yuan, and Xueyang Zheng. "An Eight-Zonal Piezoelectric Tube-Type Threaded Ultrasonic Motor Based on Second-Order Bending Mode." Applied Sciences 9, no. 10 (May 16, 2019): 2018. http://dx.doi.org/10.3390/app9102018.
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In order to reduce the driving voltage and gain better output characteristics of piezoelectric actuators, an eight-zonal piezoelectric tube-type threaded ultrasonic motor based on two second-order bending modes was analyzed using the method of finite element analysis (FEA), and a prototype was fabricated and experimentally studied in this research. This piezoelectric motor was designed to be excited by four electrical sources applied simultaneously to four groups of electrodes on the customized lead zirconate titanate (PZT) tubular stator (inside diameter 5.35 mm, outside diameter 6.35 mm, length 30 mm), with ±90° phase shifts between adjacent electrodes. Experimental results show that the threaded motor could output a stall force (stall force means the output pull or thrust force when the linear speed is set to be zero) of about 5.0 N and a linear velocity of 4.9 mm/s with no load at the driving voltage of 40 Vpp (Vpp means the peak-to-peak value of the voltage volts). This piezoelectric motor with a compact structure and screw drive mechanism shows relatively fine velocity controllability and has huge superiority in micro-positioning systems.
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Tripathi, Tulika, and Nripendra Kishore Mishra. "Precarious Self-Employment in India: A Case of Home-Based Own Account Enterprises." Journal of Labor and Society 24, no. 1 (April 19, 2021): 133–62. http://dx.doi.org/10.1163/24714607-20212005.
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Abstract A new thrust towards self-employment is seen in India where more than half of the labor class is fending for itself outside the ambit of any kind of employment. Global production networks (gpn s) have changed the structure of the labor market and extended precarity to almost every part of work and world. This has created a labor class that is neither proletariat nor bourgeois but a petty producer integrated in gpn s through mediators called ‘contractors.’ These producers are basically laborers who have been pushed out of the factory system and forced into self-employment. The paper has studied the trajectory of non-agricultural home-based Own Account Enterprises (oae s); a classic case of petty producers across gender and caste lines in various sectors of industry using state-organized enterprise surveys conducted in 2010–2011 and 2015–2016. It has found a vast majority of oae s earning less than half the proposed minimum wage (pmv)—a threshold similar to the idea of living wages rates. The most distressed oae s are in manufacturing, especially, textile, garment, leather, and chemical industries. The over emphasis on self-employment is shrinking the space for labor movement particularly in the global South.
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CITRINITI, J. H., and W. K. GEORGE. "Reconstruction of the global velocity field in the axisymmetric mixing layer utilizing the proper orthogonal decomposition." Journal of Fluid Mechanics 418 (September 10, 2000): 137–66. http://dx.doi.org/10.1017/s0022112000001087.
Full textAbstract:
Experimental data are presented from 138 synchronized channels of hot-wire anemometry in an investigation of the large-scale, or coherent, structures in a high Reynolds number fully developed, turbulent axisymmetric shear layer. The dynamics of the structures are obtained from instantaneous realizations of the streamwise velocity field in a single plane, x/D = 3, downstream of a round jet nozzle. The Proper Orthogonal Decomposition (POD) technique is applied to an ensemble of these realizations to determine optimal representations of the velocity field, in a mean-square sense, in terms of an orthogonal basis. The coefficients of the orthogonal functions, which describe the temporal evolution of the POD eigenfunctions, are determined by projecting instantaneous realizations of the velocity field onto the basis.Evidence is presented to show that with a partial reconstruction of the velocity field, using only the first radial POD mode, the large-scale structure is objectively educed from the turbulent field. Further, it is shown that only five azimuthal Fourier modes (0,3,4,5,6) are necessary to represent the evolution of the large-scale structure. The results of the velocity reconstruction using the POD provide evidence for azimuthally coherent structures that exist near the potential core. In addition to the azimuthal structures near the potential core, evidence is also found for the presence of counter-rotating, streamwise vortex pairs (or ribs) in the region between successive azimuthally coherent structures as well as coexisting for short periods with them. The large-scale structure cycle, which includes the appearance of the ring structure, the advection of fluid by the ribs in the braid region and their advection toward the outside of the layer by a following ring structure, repeats approximately every one integral time scale. One surprising result was that the most spatially correlated structure in the flow, the coherent ring near the potential core which ejects fluid in the streamwise direction in a volcano-like eruption, is also the one with the shortest time scale.