Academic literature on the topic 'Nozzle radius'

The irrigation requires an efficient and effective method of water application to realize maximum return and conserve water resources. The low pressure sprinkler irrigation system is the most commonly used due to: its low energy cost, but the irrigation uniformity of this system is not constantly good because it is affecting by the design factors such as: nozzle type, nozzle diameter, operating pressure and spacing layout. But the most important factors are the operating pressure and nozzle diameter. In this study the effect of low pressure on the irrigation uniformity of the solid set sprinkler irrigation system was studied. Different low operating pressures (62, 82, 102 and122 kPa) were selected and different nozzle diameters (4, 5 and 7 mm) were used. The solid set layout was square (12 m between the sprinklers along the line and 12 m among the line). The catch-cans test was used to determine the uniformity coefficients such as: Christiansen’s coefficient of uniformity (CU), coefficient of variation (CV), distribution uniformity of low quarter (DUlq) and distribution uniformity of low half (DUlh). The distribution characteristics such as: throw radius and rotation speed were monitored. A comparison was made between the results obtained from different combination of operating pressures and nozzle diameters. The results of this study showed that, CU, DUlqand DUlhwere increased when the pressure increased for all the nozzles. The greater values of CU, DUlqand DUlhwere found with the combination of 7 mm nozzle diameter and 122 kPa. The coefficient of variation was increased when the pressure decreased for all the nozzles. The throw radius and rotation speed were increased gradually when the pressure increased. The throw radius was not significantly affected by the nozzle diameter while the rotation speed was more affected by the nozzle diameter.

AbstractSeveral flow phenomena, such as recirculating wake flows or noise generation, occur in aerodynamic configurations with backward facing steps. In this context, subsonic nozzles with constant-radius centerbodies exist, which enable fundamental research of these phenomena for $$M < 1$$M<1. For the supersonic regime, however, the existing database and knowledge are limited. Therefore, this work presents a design approach for a converging-diverging nozzle with constant-radius centerbody. For the nozzle throat, Sauer’s method is modified to include a centerbody. The method of characteristics is used for the subsequent supersonic portion. Comparing the analytical calculations to numerical simulations results in very good agreement and therefore underlines the feasibility of the chosen approach. Viscosity reduced the Mach number on the exit plane by 1.0–1.2% and therefore had little influence.

Limit pressures have been calculated for the case of two identical flush neighbouring radial nozzles in a spherical pressure vessel. The nozzle and vessel radius and thickness have been kept fixed, but the separation angle 2α has been varied. Four cases have been analysed, including that where the nozzles touch, and the results compared to the value for a single nozzle. For these nozzles very little decrease occurred for any of the α. The effect of displacement on pressure carrying capacity was also investigated and shown to be beneficial, so that limit pressure results may be used with confidence.

A row of jets discharging normally into a confined cylindrical crossflow is numerically investigated using the control-volume-based finite difference method. Interest is focused on determining the relationship between the temperature trajectory and the upstream flow and geometric variables. Parameter variations studied include nozzle diameter, number of nozzles, duct radius, jet and mainstream volume-flow, temperature ratio, and dynamic pressure ratio. The dynamic pressure ratio, the number of nozzles, and nozzle spacing are found to be significant variables. A logarithmic function describing the relationship between penetration depth and dynamic pressure divided by the square of the number of nozzles is derived by fitting the data of the computation results. The values for penetration depth and nozzle spacing are described for optimum mixing. A suggested design procedure is presented, which can be used as a first approach in configuration design.

This article presents the parametric study of pull-out radius of steam generator shell nozzle junction for fast breeder reactor. An efficient finite element modeling for shell nozzle junction has been presented in which shell elements are employed to idealize the whole region. In shell nozzle junction, pull-out region is an important part, so that region is taken and studied with different radius of curvature. The pull-out radius varies from 40 to 80 mm. Five models are taken into consideration and each with different radius of curvature. The optimized stress values for all the models are presented here.

From the theory of aerohydrodynamics it is known that the design of hydraulic nozzles and the modes of their operation determine the nature of the distribution of droplets in space and the efficiency of the process. The subject of the research is the characteristics of the distribution quality of the liquid reagent, namely, the speed of dropping of droplets from the disk and the radius of the treatment zone formed by flying droplets on the coating. The question of the dispersion of the spray torch of a low-viscosity liquid, its role in the formation of the basic kinematic characteristics of moving drops, is considered. The article provides a numerical calculation and analysis of the effect of the dispersion of droplets of a distributed liquid (reagent) on the rate of dropping of droplets from a rotating disk and on the radius of the coating treatment zone. For research, two values of nozzle nozzle openings and a wide range of variation in the diameters of reagent droplets were selected. Based on the mathematical models previously developed by the authors of the process of dropping droplets from the nozzle and the movement of droplets in the air, implemented as part of a software product, the velocity of dropping of droplets from the nozzle nozzle and the rate of dropping of droplets from the disk at a given pressure were calculated. A cycle of calculations of the radius of the coating treatment zone was carried out with varying work and geometric characteristics of hydraulic equipment, providing high-quality and cost-effective implementation of the anti-icing reagent distribution process.

From the theory of aerohydrodynamics it is known that the design of hydraulic nozzles and the modes of their operation determine the nature of the distribution of droplets in space and the efficiency of the process. The subject of the research is the characteristics of the distribution quality of the liquid reagent, namely, the speed of dropping of droplets from the disk and the radius of the treatment zone formed by flying droplets on the coating. The question of the dispersion of the spray torch of a low-viscosity liquid, its role in the formation of the basic kinematic characteristics of moving drops, is considered. The article provides a numerical calculation and analysis of the effect of the dispersion of droplets of a distributed liquid (reagent) on the rate of dropping of droplets from a rotating disk and on the radius of the coating treatment zone. For research, two values of nozzle nozzle openings and a wide range of variation in the diameters of reagent droplets were selected. Based on the mathematical models previously developed by the authors of the process of dropping droplets from the nozzle and the movement of droplets in the air, implemented as part of a software product, the velocity of dropping of droplets from the nozzle nozzle and the rate of dropping of droplets from the disk at a given pressure were calculated. A cycle of calculations of the radius of the coating treatment zone was carried out with varying work and geometric characteristics of hydraulic equipment, providing high-quality and cost-effective implementation of the anti-icing reagent distribution process.

The changing of injector nozzle structure will influence the combustion and emission properties in diesel engine. Three-dimensional numerical simulation of multiphase flow of mini-sac nozzles of high pressure common rail were calculated by using the computational fluid dynamics ( CFD ) method in this paper. The results shown that this method can be more accurately obtained a lot of useful information on the flow field inside the nozzle in a relatively short period of time, and it is convenient for analysis and research the influence of geometry parameters on the flow characteristics inside the nozzle. The paper also studied the influence of nozzle inlet pressure, the angle between the axis of the hole and the axis of the injector and nozzle entrance radius to the flow characteristics inside the nozzle. It also studied the distribution of internal pressure, velocity of flow, gas-phase volume fraction and turbulent kinetic energy. These studies provided a favorable basis for the design and improvement of the nozzle structure and optimize combustion system matches.

The purpose of this investigation is to understand flow characteristics in mini/micro sonic nozzles, in order to precisely measure and control miniscule flowrates. Experimental and numerical simulation methods have been used to study critical flow Venturi nozzles. The results show that the nozzle?s size and shape influence gas flow characteristics which leading the boundary layer thickness to change, and then impact on the discharge coefficient. With the diameter of sonic nozzle throat decreasing, the discharge coefficient reduces. The maximum discharge coefficient exits in the condition of the inlet surface radius being double the throat diameter. The longer the diffuser section, the smaller the discharge coefficient becomes. Diffuser angle affects the discharge coefficient slightly.

It is hard to accurately predict the shape and the characteristic of jet because of the dynamic characteristic of water jet in the atmosphere. The Eulerian model was used to calculate the water jet numerical simulation of two-phase flow. The distribution of the velocity, pressure and the component of the nozzle flow field were obtained under the condition of the initial pressure of nozzle is 100 MPa and the outlet diameter of nozzle is 0.2 mm. The results show that fluid velocity increases rapidly in the nozzle contraction section and appears the isokinetic core area after leaving the nozzle; the fluid dynamic pressure rapid rises in the nozzle contraction section and keeps invariant at the isokinetic core area; the ratio of the contraction flow radius and the nozzle radius is 7:10.

This thesis focuses on identifying acoustic noise generating components in piezoelectric blowers through transverse velocity measurements and the development of a numerical fluid model. Piezoelectric ceramics have proven useful for many industries and areas of research involving: high precision actuators, noise control, ultrasonic devices, and many other areas. As of late, a unique adaptation of piezoelectric ceramics is surfacing in the area of pumping and cooling. Air pumps that use these ceramics replace the traditional electric motor, resulting in lower power consumption, less moving parts, constant pressure gradients, lower overall weight, and a low profile. The current drawback of this application is the acoustic radiation produced by the blowers. Since these blowers are new to market, little research or development has been done to characterize the noise emissions. This thesis studies the acoustic emissions from the front face of a Murata piezoelectric blower. Jet noise and structural vibrations are two acoustic sources of interest that are studied in this research. A Direct Numerical Simulation (DNS) of the fluid flow through a Murata blower is developed to better identify noise generating mechanisms. The model solutions predict trends in sound pressure levels (SPL) of the jet noise and volumetric flow rates. Both the SPL and flow rate are shown to be functions of critical geometrical dimensions within the flow path of a Murata blower. Important dimensional components are identified as well as non-influential ones. Design guidelines are given to reduce noise emission from the front side of a blower and increase the volumetric flow rate. The results of this research have a direct impact on the piezoelectric blower industry and future blower designs.

A medição de vazão de escoamentos multifásicos é uma necessidade constante em diversas atividades industriais como exploração de óleo e gás, controle de linhas de transporte de vapor e monitoramento de sistemas de resfriamento de usinas nucleares. Dentre os meios disponíveis para a realização da medição de vazão mássica, os dispositivos de medição de pressão diferencial constituem um dos métodos mais simples, sendo sua construção, aplicação e operação em escoamentos monofásicos bem conhecidas e definidas por normas técnicas. No entanto, sua aplicação tem sido estendida a escoamentos multifásicos, geralmente estando aliada a uma técnica adicional de medição de fração de vazio ou fração volumétrica das fases. Este trabalho descreve o estudo numérico de escoamentos multifásicos através de medidores de vazão baseados em pressão diferencial como placas de orifício e bocais de vazão de raio longo. Para tal, primeiramente foram conduzidas simulações de escoamentos monofásicos através de placas de orifício e bocais de vazão de raio longo na faixa de número de Reynolds 15.000 500.000. Os resultados de coeficiente de descarga obtidos foram quantitativamente comparados com os valores preditos por norma ISO, apresentando desvio máximo de aproximadamente 4, 9% para as placas e de 1,0% para os bocais. Em uma segunda etapa, escoamentos do tipo gás úmido (wet gas) através de placas de orifício foram simulados através de três abordagens diferentes. Os resultados de vazão mássica total obtidos foram comparados com dados experimentais fornecidos pela PETROBRAS. As abordagens que consideram o escorregamento entre as fases apresentaram previsões mais próximas dos experimentos, com desvio relativo médio de 3,9%, enquanto a modelagem homogênea apresentou um desvio médio de 6, 6%. Nestes estudos, foram também avaliadas as estruturas desenvolvidas no escoamento através de visualizações da distribuição de fases. São também apresentadas duas sugestões para complementação da caracterização de um escoamento multifásico: (1) a introdução da informação de fração de vazio na formulação apresentada por Paz (2011) e (2) a análise estatística do sinal de pressão diferencial em placas de orifício. Com relação ao primeiro item, comparações quantitativas com dados experimentais sugeriram que a alternativa apresentada é viável para operações de monitoramento da produção. Já o último estudo mostrou qualitativamente a influência da quantidade de líquido na flutuação da pressão diferencial
The flowrate measurement of multiphase flows is a constant need at many industrial activities such as oil and gas exploration, steam transport lines control and monitoring of nuclear plants cooling systems. Within the available means for performing flowrate measurement, the differential pressure devices constitute one of the simplest methods, with their construction, application and operation in single phase flows being well known and defined by technical standards. However, their application has been extended to multiphase flows, usually being allied to a void fraction or phase volume fraction measurement technique. This work describes a numerical study of multiphase flows through differential pressure-based flowrate meters such as orifice plates and long radius nozzles. Firstly simulations of single phase flows through orifice plates and long radius nozzles were conducted in the Reynolds number range 15.000500.000. The obtained results of discharge coefficients were quantitatively compared to ISO Standard predicted values, showing a maximum deviation of approximately 4,9% for the orifice plates and of 1,0% for the nozzles. In a second stage, wet gas flows through orifice plates were simulated by means of three approaches. The calculated results of total mass flowrate were compared to experimental data provided by PETROBRAS. The approaches that considered the slip between phases provided the closest results to the experiments, with a mean relative error of 3, 9%, while the homogeneous modeling presented an error of 6, 6%. In these studies, the structures developed within the domain were also evaluated through the visualization of the phases distribution. Two suggestions for complementing the characterization of a multiphase flow are presented: (1) the introduction of void fraction information into the formulation presented by Paz (2011) and (2) the statistical analysis of the orifice plate pressure drop signal. Regarding the first item, quantitative comparison with experimental data suggested that the presented alternative is viable for production monitoring operations. The last study qualitatively revealed the influence of the liquid loading in the pressure drop fluctuation.

Turbochargers are becoming an essential device in internal combustion engines as they boost the intake air with more pressure in order to increase the power output. These devices are normally designed for a single steady design point but the pulsating flow delivered from the internal combustion engine is everything but steady. The efficiency drop experienced in the off-design points by the fixed geometry turbochargers have made some research groups to look into new variable geometry solutions for turbocharging. A nozzle ring is a device which normally achieves a higher performance under design conditions, but the efficiency rapidly drops at off-design conditions. In this paper, a variable angle nozzle ring is designed and implemented in the model of a radial turbine of a turbocharger in order to study its potential when working under real internal combustion engine cycles. To understand the profit margin the turbine performance is compared with two turbines with the same impeller geometry: one without nozzle ring and one with a nozzle ring with a fixed angle. The results show that the maximum efficiency angle function calculated for the variable angle nozzle ring achieves an improvement in the total efficiency of 5 % when comparing with a turbine with a fixed angle and 18 % when comparing with a vaneless turbine. The improved guidance achieved due to the variable blade angle leads to less turbine losses and therefore more mechanical energy can be extracted from the exhaust mass flow throughout all the combustion cycle but a further study should be made in order to match all the engine operations points. Notably, taking the pulsating boundary conditions into consideration, a remarkable improvement is achieved already for the fixed angle nozzle ring.

The design of a radial turbine working at peak efficiency over a wide range of operating conditions is nowadays an active topic of research, as this constitutes a target feature for applications on turbochargers. To this purpose many solutions have been suggested, including the use of devices for better flow guidance, namely the nozzle ring, which are reported to boost the performance of a radial turbine at both design and off-design points. However the majority of performance evaluations available in literature are based on one-dimensional meanline analysis, hence loss terms related to the three-dimensional nature of real flows inside a radial turbine are either approximated through empirical relations or simply neglected.In this thesis a three-dimensional approach to the design of a radial turbine is implemented, and two configurations, with and without fixed nozzle ring, are generated. The turbine is designed for a turbocharging system of a typical six-cylinder diesel truck engine, of which exhaust gas thermodynamic properties are known. The models are studied by means of a CFD commercial software, and their performance at steady design and off-design conditions are compared.Results show that, at design point, the addition of a static nozzle ring leads to non negligible increments, with respect to the vaneless case, of both efficiency and power output: such increments are estimated in +1.5% and +3.5% respectively, despite these data should be compared with the uncertainty of the numerical model. On the other hand both turbine configurations are found to be very sensitive to variations of pressure and temperature of the incoming fluid, hence off-design performances are dependent on the particular off-design point considered and a “best” configuration within all the combustion cycle does not exist.

The importance of weak interactions between molecules to life and all parts of science and engineering is unquestionable and there have been an enormous interest in such interactions. Among all the weak interactions, hydrogen bonding is the most popular and it has enjoyed the most attention of the scientific community. Halogen bonding is gaining more popularity in the recent time, as its importance to biological molecules and crystal engineering has been recognized. In this work, a Pulsed Nozzle Fourier Transform Microwave spectrometer has been used to study the rotational spectra of molecules and hydrogen bonded complexes. Structural information is obtained from the rotational spectra. Ab initio electronic structure, Natural Bond Orbital (NBO) and Atoms in Molecules (AIM) theoretical methods have been used to characterize the weak intermolecular interactions, including hydrogen bonding, halogen bonding and lithium bonding. In Chapter I, introduction to weak interaction is discussed. A brief introduction of different experimental and theoretical methods is presented. Chapter II discusses in detail about the different methods used to investigate weak interaction, both experimentally and theoretically, in this work. In our lab, we use Pulsed Nozzle Fourier Transform Microwave spectrometer to determine the complexes spectra and structures. We generate MW radiation with the help of electronic devices and use Balle-Flygare cavity where molecular interaction takes place. We inject the sample inside the cavity in form of supersonic molecular beam through a pulsed nozzle, parallel to MW radiation. The detailed instrumental discussion about MW spectrometer has been done in this Chapter. We extensively use theoretical methods to probe weak bonding and characterize them. Ab initio and DFT calculations are used to optimize the structure of the complexes and predict their rotational spectra. Atoms in Molecules theory and Natural Bond Orbital theory are then used with the ab initio wave functions to understand the weak interactions in depth. Discussion about these methods and software used for the analysis will also be discussed. In Chapter III, rotational spectrum of Hexafluoroisopropanol (HFIP) monomer is presented. HFIP is an interesting molecule as it offers many possibilities as hydrogen bond donor and acceptor. It has the OH group which can both accept/donate a hydrogen bond and in addition it has a very acidic CH group. It is the only solvent that can dissolve polyethylene terephthalate, a normally difficult-to-dissolve polymer, and clearly it has unique interactions with this difficult to solve polymer. We have recorded and fitted rotational spectra of five different isotopologues of HFIP which helped us in determining its accurate structure. Though, it can exist in synclinical and antiperiplanar conformers, only the later has been detected in our molecular beam spectrometer. This happens to be the global minimum structure of HFIP. Combination of experimental observations and ab initio calculations provided many evidences which confirmed the presence of antiperiplanar conformer, experimentally. Since, the rotational constants for both conformers were very close, it was always challenging to pick up one conformer as experimentally observed structure. A prototype molecule, hexafluoroisobutene (HFIB) shows doubling of rotational transitions due to tunnelling/counter rotation of the two CF3 groups through a small barrier. Interestingly, such motion has no barrier in HFIP and hence no splitting in transitions was observed. Potential energy surface calculated for counter-rotation of the two CF3 groups is consistent with this observation. This barrier is different from eclipsed-staggered exchange barrier, observed by 60 counter rotation of both terminal CF3 groups, for which the barrier height is very large and tunnelling cannot occur. The origin/lack of the small barrier in HFIB/HFIP has been explored using Natural Bond Orbital (NBO) method which helped in understanding intramolecular bonding in these molecules. Along with HFIB, other prototype molecules were also considered for the analysis e.g. hexafluoroacetone, hexafluoroacetone imine, hexafluoroisobutane, hexafluoroisopropylamine. In the last section of this Chapter, we have discussed the generalized behaviour of molecules which have CF3-C-CF3 groups. In Chapter IV, rotational spectrum of HFIP•••H2O complex is presented. Aqueous solution of HFIP stabilizes α-helical structure of protein, a unique property of this solvent. The main objective of this Chapter is understanding the interaction between HFIP and H2O. Microwave spectrum of HFIP•••H2O was predicted and recorded. Three isotopologues were investigated. Though, this complex could in principle have several structural conformers, detailed ab initio calculations predicted two conformers and only one was observed. Though, the rotational constants for both structures were somewhat similar, lack of a dipole transitions, larger intensity of b-dipole transitions over c-dipole transitions and isotopic substitution analysis positively confirm the structure in which HFIP acts as the hydrogen bond donor. The linear O-H•••O hydrogen bond in HFIP-H2O complex is significantly stronger than that in water dimer with the H•••O distance of 1.8 Å. The other structure for this complex, not found in experiment is cyclic with both C-H•••O and O-H•••O hydrogen bonds, both of which are bent with H•••O distances in the range 2.2-2.3 Å. Both AIM and NBO calculations have been used to characterize the hydrogen bond in this complex. In Chapter V, a comprehensive study on hydrogen bonding, chlorine bonding and lithium bonding have been done. A typical hydrogen bonded complex can be represented as A•••H-D, where A is the acceptor unit and H-D is the hydrogen bond donor unit. Many examples are known in literature, both experimentally and theoretically, in which the A-H-D bond angles are not linear. Deviation from linearity also results in the increase in A•••H bond lengths, as noted above for the two structures of HFIP•••H2O complex. Though this has been known for long, the distance between A and D being less than the sum of their van der Waals ‘radii’ is still used as a criterion for hydrogen bonding by many. Our group has recently shown the inappropriateness of van der Waals ‘radii’ and defined hydrogen bond ‘radii’ for various donors, DH and A. A strong correlation of DH hydrogen bond ‘radii’ with the dipole moment was noted. In this Chapter, we explored in detail the angular dependence of hydrogen bond ‘radii’. Electron density topology around DH (D = F, Cl and OH) has been analyzed in detail and shown to be elliptical. For these molecules, the two constants for H atom treated as an ellipse have been determined. It is hoped that these two constants will be used widely in analyzing and interpreting H•••A distances, as a function of D-H•••A angles, rather than one ‘radius’ for H and acceptor atoms. In Chapter VI, Detailed analysis and comparisons among hydrogen bond, chlorine bond and lithium bond, have been done. Hydrogen can be placed in group 1 as well as group 17 of the periodic table. Naturally, lithium bonding and halogen bonding have been proposed and investigated. There have been numerous investigations on the nature of hydrogen bonding and the physical forces contributing to it. In this Chapter, a total of one hundred complexes having H/Cl/Li bonding have been investigated using ab initio, AIM and NBO theoretical methods. Various criteria proposed in the literature have been examined. A new criterion has been proposed for the characterization of closed shell (ionic/electrostatic) and open shell (covalent) interactions. It has been well known that the D-H bond weakens on the D-H•••A hydrogen bond formation and H•••A bond acquires a fractional covalency. This Chapter shows that for D-Li•••A complexes, the ionicity in D-Li is reduced as the Li•••A bond is formed This comprehensive investigation of H/Cl/Li bonding has led us to propose a conservation of bond order, considering both ionic and covalent contributions to both D-X and X•••A bonds, where DX is the X-bond donor and A is the acceptor with X = H/Cl/Li. Hydrogen bond is well understood and its definition has been recently revised [Arunan et al. Pure Appl. Chem., Vol. 83, pp. 1619–1636, 2011]. It states “The X–H•••Y hydrogen bond angle tends toward 180° and should preferably be above 110°”. Using AIM theory and other methods, this fact is examined and presented in Appendix A. In second part of appendix A, a discussion about calling H3¯ complex as trihydrogen bond and its comparison with FHF¯ complex, is presented. In Appendix B, there is tentative prediction and discussion about the HFIP dimer. Condense phase studies show that HFIP have strong aggregation power to form dimer, trimer etc. During, HFIP monomer study, we have unassigned lines which are suspected to be from HFIP dimer. These are tabulated in the Appendix B as well.

碩士
中原大學
化學工程研究所
90
The purpose of the present work is to study radial gas mixing in a multi-horizontal nozzle distributor fluidized bed. The experiments were studied using response surface methodology (RSM), which is a collection of mathematical and statistical techniques that are useful for the modeling and analysis of experiments. The experiments were carried out in a circular fluidized bed of 0.29 m inside diameter. The distributor is placed by 22 horizontal nozzles which are arranged in three concentric circles with all discharge exists directed clockwise. The carbon dioxide is discharged into the bed as the tracer. It was sampled by sampling tube in the downstream of the fluidized bed. The analysis is made by the Gas Chromatograph (MTI M200). In order to compare the internal circulation, the tracer can be discharged in the center area or annular area of the bed. At the same time, static bed height, superficial velocity and open area ratio of the distributor are chosen as the research variable. This can be used as the reference of the design of the fluidized bed reactor. The results of experiment show that the experiment design by RSM, the experiment can be performed more efficiently. We also can tell the most significant influence variable. The tracer gas injected to the center position have a better dispersion; the operation condition influences the gas dispersion in the annular area violently. The superficial velocity has the most significant influence on radial gas mixing in fluidized bed. The radial gas mixing in fluidized bed is better as the superficial velocity increasing. The radial gas mixing in the center part of fluidized bed is influenced by the superficial velocity and the open ratio of distributor. The radial gas mixing in the annular part of fluidized bed is influenced by the superficial velocity and the static bed height and the open ratio of distributor. The tracer injected into bed is not raise directly; it meanders unpredictably in the multi-horizontal nozzle distributor fluidized bed

Turbulent boundary layers approximating those found on the NASA Orion Multi-Purpose Crew Vehicle (MPCV) thermal protection system during atmospheric reentry from the International Space Station have been studied by direct numerical simulation, with the ultimate goal of reducing aerothermodynamic heating prediction uncertainty. Simulations were performed using a new, well-verified, openly available Fourier/B-spline pseudospectral code called Suzerain equipped with a ``slow growth'' spatiotemporal homogenization approximation recently developed by Topalian et al. A first study aimed to reduce turbulence-driven heating prediction uncertainty by providing high-quality data suitable for calibrating Reynolds-averaged Navier--Stokes turbulence models to address the atypical boundary layer characteristics found in such reentry problems. The two data sets generated were Ma[approximate symbol] 0.9 and 1.15 homogenized boundary layers possessing Re[subscript theta, approximate symbol] 382 and 531, respectively. Edge-to-wall temperature ratios, T[subscript e]/T[subscript w], were close to 4.15 and wall blowing velocities, v[subscript w, superscript plus symbol]= v[subscript w]/u[subscript tau], were about 8 x 10-3 . The favorable pressure gradients had Pohlhausen parameters between 25 and 42. Skin frictions coefficients around 6 x10-3 and Nusselt numbers under 22 were observed. Near-wall vorticity fluctuations show qualitatively different profiles than observed by Spalart (J. Fluid Mech. 187 (1988)) or Guarini et al. (J. Fluid Mech. 414 (2000)). Small or negative displacement effects are evident. Uncertainty estimates and Favre-averaged equation budgets are provided. A second study aimed to reduce transition-driven uncertainty by determining where on the thermal protection system surface the boundary layer could sustain turbulence. Local boundary layer conditions were extracted from a laminar flow solution over the MPCV which included the bow shock, aerothermochemistry, heat shield surface curvature, and ablation. That information, as a function of leeward distance from the stagnation point, was approximated by Re[subscript theta], Ma[subscript e], [mathematical equation], v[subscript w, superscript plus sign], and T[subscript e]/T[subscript w] along with perfect gas assumptions. Homogenized turbulent boundary layers were initialized at those local conditions and evolved until either stationarity, implying the conditions could sustain turbulence, or relaminarization, implying the conditions could not. Fully turbulent fields relaminarized subject to conditions 4.134 m and 3.199 m leeward of the stagnation point. However, different initial conditions produced long-lived fluctuations at leeward position 2.299 m. Locations more than 1.389 m leeward of the stagnation point are predicted to sustain turbulence in this scenario.
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The objective of this study is to examine the American Society of Mechanical Engineers (ASME) Long Radius Flow Nozzle. This study was conducted with regard to published standards for design and installation, manufacturing, and the comparative analysis of laboratory flow calibrations to the theoretical predictions of the coefficient of discharge. Several sets of identically designed Long Radius Flow Nozzles were manufactured and laboratory flow calibrated. The results of the flow calibration data were used to evaluate the accuracy of the prediction equations for the Coefficient of Discharge and to determine the effects of materials and manufacturing processes such as post weld stress relieving. Preliminary results of continuing research indicate that the uncertainty of the coefficient of discharge may be 1% or less while the published uncertainty is 2%. These results indicate that well controlled design and manufacturing processes influence the flow nozzle performance. These results are based on flow calibration data from an independent laboratory. In conclusion, the long radius flow nozzle can be designed and manufactured so the uncertainty associated with the coefficient of discharge is less than published values. Further study is required of the published equations for predicting the coefficient of discharge.

Reactor pressure vessel nozzle inner radius (NIR) areas are identified as a specific target for ultrasound examination (UT) by many regulatory codes. This region represents a particularly challenging geometry to examine. Typically the examination is performed from inside the vessel with at least the upper internals removed. Normally the inspection is on the critical path so minimizing the schedule and vessel occupation time is important to the utilities outage planning and ultimate financial performance. Although some inspection vendors have traditional qualifications for this NIR examination under various codes, this paper addresses several advanced techniques have been developed to minimize the critical path inspection time. Technology advancements include: • Stereo-vision with laser reference for precise VT sizing of any observed indication • A Small 5 degree-of-freedom arm to precisely track a transducer set along the inner-radius surface for immersion ultrasonic examination • A simple nozzle-only tool with a passive mechanism to track the nozzle inner-radius surface for contact ultrasonic examination • Advanced software (3-D iMaV) coupled with a 5-axis robot to analyze and control transducer placements and coverage from the nozzle and shell outside (OD) The net result is a more efficient examination with shorter schedules and lower overall outage costs.

Two dimensional (2-D) axisymmetric finite element models (FEMs) are often used as a simplified means of modeling cylindrical nozzles that intersect cylindrical pressure vessels. An axisymmetric model represents the vessel as a spherical shell rather than a cylindrical shell. Therefore, analysts must correct the stresses predicted by the 2-D model to account for the three dimensional (3-D) effects caused by the true nozzle geometry, which are not represented by the 2-D axisymmetric simplification. This paper presents total stress correction factors for the nozzle blend radius region of Boiling Water Reactor (BWR) Feedwater, Core Spray and Recirculation Inlet nozzle geometries. The correction factors are defined by taking the ratio of the total hoop stress from the 3-D nozzle FEM to the total hoop stress obtained from the 2-D nozzle FEM. Eighteen (18) separate nozzle designs were evaluated. These cases are considered to span the range of dimensions expected for General Electric type BWR-2 through BWR-6 Feedwater, Core Spray, and Recirculation Inlet nozzles.

The American Society of Mechanical Engineers (ASME) published Section XI Code Case N-648-1 [1] in order to provide alternative examinations of reactor vessel nozzle inner radii. The Code Case was created because ultrasonic examination of the inner radius regions of reactor vessels nozzles is not practical within the operating fleet and the likelihood of flaws developing within these locations is extremely low. Justification for using alternative visual examinations was provided in a paper published at the 2001 Pressure Vessel and Piping (PVP) Technology Conference [2]. This 2001 PVP paper used linear elastic fracture mechanics (LEFM) to demonstrate tolerance for flaws significantly larger than would be detected using nondestructive examination techniques. However, the Code Case [1] and PVP paper [2] were only applicable to operating plants in the United States. Thus, there was a need to provide a similar fracture analysis considering the AP1000® design to support elimination of volumetric examinations of the nozzle inner radius regions. It was also important to consider improvements in facture mechanics techniques that have been recently published in the ASME Code. The ductile behavior of the material at operating temperatures allow for the use of elastic plastic fracture mechanics (EPFM) methods which provides significantly improved flaw tolerance results. This paper compares results from analyses using LEFM and the EPFM methods for the AP1000 reactor vessel nozzle inner radii region and demonstrates tolerance for large flaws within these regions in order to support a basis for elimination of volumetric inspection during in-service and pre-service examination for the AP1000 design.

The main steam super pipe used in nuclear power plant is an important safety class2 component. There are several nozzles located on it and linked with main steam safety valves. In the past two decades, the hot extrusion forming technology has been widely used to manufacture the super pipe nozzles. Comparing with traditional insert weldolet, the wall thickness of the extruded nozzle is relative small, and the nozzle inner radius is hard to control precisely in the fabrication process. Due to high temperature working condition and complicated loading conditions, the load capacity of the super pipe extruded nozzle has become an issue of concern for manufacturers and users. This paper presents a structural integrity assessment of a super pipe extruded nozzle. The nozzle stresses due to internal pressure and external loads for different operating conditions are obtained by the three-dimensional finite element analysis. The extruded nozzle is evaluated against the RCCM code Subsection C3200 Service Levels O, B and D stress limits for design, upset and faulted conditions. A parametric sensitivity analysis of the extruded nozzle inner radius size is also carried out. In addition, in order to reduce the calculation effort, an efficient calculation method is developed by using the commercial finite element program ANSYS.

This paper presents computational fluid dynamic (CFD) predictions of flow and heat transfer for an over-swirled low-radius pre-swirl system and comparison with experimental data. The rotor-stator CFD model comprises a stationary domain with the pre-swirl nozzles and a rotating domain with the receiver holes. The fluid-dynamic conditions feature an over-swirled system with a swirl ratio at the nozzle radius βp = 1.4–1.5 and rotational Reynolds number Reφ = 0.8×106 and 1.2×106. Three different treatments for the rotating and stationary domain interface are used to evaluate the influence on the flow and heat transfer behavior: a stationary approach (including Coriolis forces in the rotating domain) with “direct connection” and fixed angle between pre-swirl nozzle and receiver holes; a stationary approach with circumferential averaging of the velocity at radial bands; and a full transient simulation with the rotating domain capturing the unsteady flow due to the rotating receiver holes. Results at different circumferential angles show high variability in pressure and velocity distributions at the pre-swirl inlet nozzle radius. Circumferential averaging of these flow parameters lead to an alignment of the pressures and velocities between the three different interface approaches. Comparison with experimental pressure and swirl-ratio data show a quantitative agreement but the CFD results feature a systematic overestimation outward of the pre-swirl nozzle radius. Heat transfer contours at the rotor surface show the effect of the different interface approaches and dependence on the flow structure (for example the impinging jet and vortex structures). The three different interface approaches result in significant differences in the computed heat transfer coefficients between pairs of receiver holes. Circumferentially averaged heat transfer coefficients inward of the receiver holes radius show good agreement between the transient and stationary direct connection interfaces, whereas those for the circumferential averaging interface differ, contrary to the flow parameters, due to smoothing of local effects from the pre-swirl jets.

The purpose of this investigation is to conduct a comparative study on the formation of bubble on top of a stainless steel needle nozzle and two substrate plate nozzles. The experimental study is conducted on a submerged needle nozzle with internal diameter of 0.51 mm and 0.155 mm thickness, and two stainless steel substrate plates with nozzle diameter of 0.4 mm and 0.51mm respectively. The experiment is carried out under low gas flow rates (0.015 ∼ 0.85 ml/min). The bubble formation is recorded by a high speed video camera and detailed characteristics of bubble formation such as the variations of instantaneous contact angles, bubble heights and the radii of contact lines are obtained, which show a weak dependence on the flow rate under the conditions of current work. Using experimentally captured values of the height of bubble and the radius of contact line, the Young-Laplace equation is solved, which is found to be able to predict bubble evolution quite well until the last milliseconds before the detachment. Interestingly, it is found that the trends of the variation of bubble volume expansion rate from the stainless steel needle and the substrate plate are different, however, the rest of bubble characteristics such as radius of contact line, bubble height, contact angle, and radius of curvature of bubble apex follow same trends as the time and bubble volume change for formation of bubble on top of needle and substrate nozzles. A force analysis of bubble formation reveals that the observed variations of contact angles and other characteristics during the bubble growth period are associated with the relative contribution of surface tension, buoyancy and gravitational forces.