Commercial Computational Fluid Dynamics Analysis Research Articles

Cfd Analysis to Investigate the Effect of Leaned Rotor On the Performance of Transonic Axial Flow Compressor Stage

This paper describes the numerical study carried out to understand the impact of combination of forward and backward leaned rotor on the overall performance of a transonic axial flow research compressor of CSIR National Aerospace Laboratories (NAL), Bangalore. The analyses were carried out using commercial Computational Fluid Dynamics (CFD) solver Ansys-CFX. Initially CFD analysis was carried out for the baseline rotor configuration and validated the results with the experimental data. Then, three new configurations of combined Leaned rotors were modeled from the radially stacked baseline rotor by changing the circumferential curvature of original stacking line using three control points located at 0%, 50% and 100% of the blade span. Analyses were carried out for all the three configurations of modified geometries and the results were compared with the baseline configuration. The results revealed many interesting aspects which will be very useful for better understanding of the blade curvature effects on the shock and secondary losses within the transonic rotor. The discussions on the effect of combination of forward and backward leaned rotor and the consequent developments on the overall performance of the compressor are presented in detail in this paper.

CFD Analysis on Different Filling Volume Capacity and Fluid Density for Flexitank Application

When it comes to the structural design of flexitanks used for freight transportation, liquid sloshing is a crucial subject of concern. However, with consideration of the flexitank shape, there is no specific capacity value that can be used as a guide for filling the liquid inside it. This phenomenon may cause a high-pressure impact on the flexitank, resulting in a leakage on the LLDPE package. One of the solutions to reduce the frequency of leaks occurred is to fill up the acceptable volume based on hydrodynamics performance. Therefore, the purpose of this paper is to investigate, using commercial computational fluid dynamics (CFD) software, the hydrodynamic performance of various flexitank filling volume capacities based on different liquid densities. This is evaluated by comparing the hydrodynamics study for filling capacities that are 1%, 2%, and 3% higher than the rated capacity for flexitanks that has been suggested by the Container Owner Association (COA). Due to the flexitanks thin walls, it is important to consider the impacts of fluid-structure interaction (FSI). To do this, a partitioned FSI approach is used by coupling the CFD and FEA solvers for this multi-physics issue. The main standpoint of FSI is that fluid forces are applied to structures, causing deformation. Hydrodynamic parameters such as structural deformation on flexitank, von-mises stress and von-mises strain were used to identify the suitable filling capacity for three different: water, latex, and crude palm oil, as these liquids are commonly used for flexitank. The results indicate that varying the liquid filling capacity affected the hydrodynamic performance of the flexitank. Following that, increasing the flexitank filled with water by 3% and increasing the flexitank filled with latex and CPO by 1% can lead to structural damage as it gives highest maximum value of total deformation for these capacities. Since the situation of the flexitank are in the braking condition, the highest elastic equivalent strain is occurred at the front-top of the flexitank structure.

Computational analysis of fine droplet in swirl injector for desalination

Desalination refers to a water treatment process that removes salts from water. Low Pressure Flash Evaporation desalination (LPFE) process is conducted experimentally with using of high flow swirl injector. This injector is used to improve the efficiency of the plant. The effects of atomizer’s dimensions and flow parameters were studied and analyzed to get desirable droplet size and good yield. From this parametric study, we can know that droplet diameter effects yield. The theoretical results shows that droplet size should be in the range of 0.9 to 1.0 mm to get maximum yield.The internal flow behavior in high flow swirl injector also studied using a commercial computational fluid dynamics (CFD) software - FLUENT. Through these works, designed a swirl nozzle at high flow rate (1lit/s) with parameter’s study and optimized technically. This paper deals, through CFD analysis that desirable range of droplet size is analyzed and has been proved that to get maximum yield with the effect of various flow parameters. The result gives a valuable output for developing technology in desalination.

Numerical Analysis of Inertance Pulse Tube Refrigerator

The inertance type pulse tube refrigerator (IPTR) has been extensively used in industries due to its small size and efficiency. The physical phenomena of oscillating flow in IPTR is complex and it can be examined by using a commercial computational fluid dynamics (CFD) software. Researchers are not so much interested in the 3D analysis of IPTR due to high computational time but for better visualization, it is very beneficial. A two-dimensional axis-symmetric model and 3D model is considered for simulation. The temperature at the cold heat exchanger (CHX) and phase difference between pressure and mass flow rate at CHX is demonstrated. In this paper, CFD analysis of IPTR has been done and various issues involved in the simulation are presented for the betterment in the desired solution.

Reduction of flow-induced noise in a household air purifier

In this study, we propose a design for a household air purifier that reduces the flow-induced noise caused by the impeller of the fan system. The noise of the air purifier was identified in experiments as induced by the air flow generated by the impeller of the purifier. This noise can be classified into tonal noise and wide-band frequency noise: The former is the noise from the impeller blade turning, and the latter is from air flow turbulence. Using a commercial computational fluid dynamics (CFD) analysis code, it was shown that flow separation occurs at the outlet of the scroll by the adverse pressure gradient, which significantly reduces the flow rate of the purifier. To avoid flow separation and maximize flow rate within the adjustable ranges of the design parameters, an improved air purifier was redesigned using an orthogonal array table. By CFD analysis, the improved design showed an increased flow rate without flow separation. Finally, after fabricating a prototype with the improved design, it was experimentally proven that noise was reduced by 4.2 dBA without sacrificing flow rate.

CFD Analysis of Aggregation and Breakage of Li-Ion Precursor in Taylor-Reactor

In this work, aggregation and breakage of Li-ion precursor in Taylor-reactor are studied for various simulation condition, i.e., agitation rate, particle property, and reactor direction. The mean particle size and distribution is important to electrochemical performance of cathode materials. The population balance equation (PBE) is solved for coupling between particle interaction and fluid dynamic. The quadrature method of moments (QMOM) is implemented in a commercial computational fluid dynamics (CFD) code. Sum of three aggregation kernels, such as turbulent, Brownian, and Stokes aggregation, is considered for the calculation. [1] Breakage kernel is a combination of power-law kernel and various daughter distribution functions. Collision efficiency is assumed to be equal and the precursor is considered as spherical particle. Three-dimensional analysis is implemented and the simulation results are compared with experimental data. [1] L. Claudotte, N. Rimbert, P. Gardin, M. Simonnet, J. Lehmann, and B. Oesterle, AIChE J., Vol.56, No.9, pp. 2347-2355 (2010)

Development of the loss coefficient correlation for cross flow between graphite fuel blocks in the core of prismatic very high temperature reactor-PMR200

The core of the very high temperature reactor (VHTR) PMR200 (a prismatic modular reactor rated at 200MW of thermal power) consists of hexagonal prismatic fuel blocks and reflector blocks made of graphite. If the core bypass flow ratio increases, the coolant channel flow is decreased and can then lower the heat removal efficiency, resulting in a locally increased fuel block temperature. The coolant channels in the fuel blocks are connected to bypass gaps by the cross gap, complicating flow distribution in the VHTR core. Therefore, reliable estimation of the bypass flow is highly important for the design and safety analysis of the VHTR core. Because of the complexity of the core geometry and gap configuration, it is challenging to predict the flow distribution in the VHTR core. To analyze this flow distribution accurately, it is necessary to determine the cross flow phenomena, and the loss coefficient across the cross gap has to be evaluated to determine the flow distribution in the VHTR core when a lumped parameter code or a flow network analysis code that uses the correlation of the loss coefficient is employed. The purpose of this paper is to develop a loss coefficient correlation applicable to the cross gap in the PMR200 core. The cross flow was evaluated experimentally using the difference between the measured inlet and outlet mass flow rates. Next, the applicability of a commercial computational fluid dynamics (CFD) code, CFX 15, was confirmed by comparing the experimental data and CFD analysis results. To understand the cross flow phenomena, the loss coefficient was evaluated; in the high Reynolds number region, the cross flow loss coefficient on Reynolds number is nearly constant regardless of the Reynolds number, whereas it varies with the gap size in the low Reynolds number region. Finally, the loss coefficient correlation was proposed on the basis of experiments and the CFD analysis. The developed correlation was compared with existing correlations, and the developed one shows better agreement with the experimental results than the existing ones. Hence, the developed correlation will be applied to the flow network code to analyze flow distribution in the PMR200 core.

Analytical Study on the Effective Thermal Conductivity of VHTR Fuel Block Geometry with Multiple Cylindrical Holes

In Korea, the Very High Temperature Gas-Cooled Reactor (VHTR) PMR200 is being developed in the Nuclear Hydrogen Development and Demonstration project. Its core consists of hexagonal prism-shaped graphite blocks for the fuel and reflector, and each hexagonal fuel block contains 108 cylindrical coolant holes and 210 fuel compacts. Because of these holes and fuels, the heat transfer in lateral directions in the fuel blocks becomes very complicated. Especially in accident situations when forced convection is lost, the majority of the afterheat flows in the radial direction by conduction across the large number of coolant holes. Moreover, radiation heat transfer is supposed to be added to the radial heat transfer modes owing to the high temperature of the VHTR core. Because of these complexities in radial heat transfer, reliable modeling for effective thermal conductivity (ETC) is required in order to analyze the reactor core thermal behavior using lumped-parameter codes, which are often used to evaluate the integrity of nuclear fuel embedded in the graphite block. In this study, the ETC model adopted in the GAMMA+ code was introduced, and the adequacy of the model was assessed by the commercial computational fluid dynamics (CFD) code CFX-13. The results of the CFD analysis were consistent with the ETC model in general even if a slight disagreement was shown for the case of high temperature. From these analyses, it could be concluded that the ETC model adopted in the GAMMA+ code is an adequate model for the analysis of the PMR200 reactor core. Moreover, it was found that the effect of fuel gap can cause an overprediction of the ETC if the fuel compact thermal conductivity is larger than the applicable range of the model.

CFD analysis of bubble hydrodynamics in a fuel reactor for a hydrogen-fueled chemical looping combustion system

This study investigates the temporal development of bubble hydrodynamics in the fuel reactor of a hydrogen-fueled chemical looping combustion (CLC) system by using a computational model. The model also investigates the molar fraction of products in gas and solid phases. The study assists in developing a better understanding of the CLC process, which has many advantages such as being a potentially promising candidate for an efficient carbon dioxide capture technology.The study employs the kinetic theory of granular flow. The reactive fluid dynamic system of the fuel reactor is customized by incorporating the kinetics of an oxygen carrier reduction into a commercial computational fluid dynamics (CFD) code. An Eulerian multiphase treatment is used to describe the continuum two-fluid model for both gas and solid phases. CaSO4 and H2 are used as an oxygen carrier and a fuel, respectively. The computational results are validated with the experimental and numerical results available in the open literature. The CFD simulations are found to capture the features of the bubble formation, rise and burst in unsteady and quasi-steady states very well. The results show a significant increase in the conversion rate with higher dense bed height, lower bed width, higher free board height and smaller oxygen carrier particles which upsurge an overall performance of the CLC plant.

CFD analysis of tracer response technique under cake-enhanced osmotic pressure

A cake-layer mass transfer model applicable for RO, that incorporates the cake-enhanced osmotic pressure (CEOP) effect of a particulate fouling layer, is presented. This model includes the effect of a variable dissolved solute concentration on the specific cake resistance and porosity of the cake layer. The model is based on one-dimensional diffusion of the dissolved solute through the cake layer, and uses the solute concentration at the cake surface and the cake mass per unit area to calculate the solute concentration at the membrane surface and the trans-membrane osmotic pressure. The cake-layer mass transfer model is incorporated into a commercial Computational Fluid Dynamics (CFD) software package. Simulations are validated against experimental data, and the model predictions are within ±7% for permeate fluxes and within ±14% for measured concentration polarisation.The model is used to interpret and assess tracer response test results for estimating concentration polarisation and fouling resistance. Model predictions confirm the assumption for the tracer experiment that the average concentration polarisation along the membrane wall does not change significantly after a step change in the feed concentration of the tracer solute. However, it was found that the tracer experiment over-estimates the concentration polarisation index and under-estimates the fouling resistance, particularly under fouled conditions. The sources of error are discussed and a multiple tracer response test is proposed to minimise estimation error.

Experimental and numerical investigation of impingement heat transfer on a flat and micro-rib roughened plate with different crossflow schemes

A combined experimental and numerical investigation of the heat transfer characteristics within an array of impingement jets on a flat and micro-rib roughened plate has been conducted. The experiments are carried out in a perspex model using a transient liquid crystal method. Local jet temperatures are measured at several positions on the impingement plate to account for an exact evaluation of the heat transfer coefficient. The effects of variation of jet-to-plate spacing, crossflow schemes and jet Reynolds number on the distribution of the local Nusselt number and the related pressure loss are investigated experimentally. The jet-to-plate spacing H/ d = 3 results in the highest heat transfer coefficients for both the flat and the micro-rib roughened plate. Overall heat transfer performance on the micro-rib roughened plate is always best for the minimum crossflow case. The heat transfer enhancement ratio increases with increasing Reynolds numbers. All the data from the micro-rib roughened plate is compared to that of the flat plate. The measurements are complemented by a numerical part, in which one particular case from the experiments is investigated by means of a commercial Computational Fluid Dynamics (CFD) software package. In the numerical results, for the heat transfer pattern the same trend as in the experiments is found. In the comparison of local heat transfer coefficients, results from experiments and predictions are of the same order. Significantly more local details are captured in the CFD analysis. The numerical study also addresses and compares the effects of 1D and 3D heat transfer by accounting for the solid domain of the rib material (conjugate heat transfer). The results of the latter show that the CFD predictions can be regarded as a valuable complement to experimental measurements for configurations where heat transfer on rib roughened surfaces are to be evaluated.

Analysis of the oil supply system of a high-pressure shell scroll compressor

The supply of lubrication oil has a great influence on the reliability and efficiency of a scroll compressor, because oil plays a role in lubrication, sealing, and heat transfer in the compressor. In this work, a comprehensive steady and transient analysis on the oil supply system of a high-pressure shell scroll compressor was carried out using a commercial computational fluid dynamics (CFD) program. Various parameters, including pressure difference, compressor rotation speed, oil temperature, bearing clearance, and diameter of the oil gallery, were investigated to find the relations with oil flowrate. Among them, oil temperature and bearing clearance are indicated as the most sensitive, and pressure difference follows. Compressor rotation speed and diameter of the oil gallery are insensitive. Some hydrodynamic parameters can also be obtained in detail, such as pressure drop and oil flow velocity. This CFD analysis has proved to be helpful for the design and optimization of an oil supply system in a scroll compressor.

Coupled Numerical Analysis of Quenching Process of Internal Combustion Engine Cylinder Head

The paper provides details about a newly developed method of coupled modelling procedure for the simulation of quenching process using a commercial Computational Fluid Dynamics (CFD) code AVL FIRE, followed by Finite Element Method (FEM) analysis to predict the stresses within the structure using ABAQUS. Boiling mass transfer process is triggered by submerging of a heated solid part into a subcooled liquid bath. As a result, two-phase flow with boiling phase change is handled using the Eulerian two-fluid method. Mass transfer effects are considered for both film and nucleate boiling regime. Separate computational domains constructed for the quenched solid part and the liquid (quenchant) domain are numerically coupled at the interface using the AVL-Code-Coupling-Interface (ACCI) feature. The program handles multiphase flow dynamics in the liquid domain in conjunction with the temperature evolution in the solid region in coupled fashion. The paper features numerical simulation results of a real cylinder head of a four cylinder gasoline engine. Comparison between measured and computed temperatures at different monitoring positions shows very good agreement for two cylinder head orientations. Significant nonuniformity in temperature distribution within the structure was observed, which is of great importance in evaluating residual stresses and fatigue patterns within the quenched object. The temperature field was mapped from volume-based computational grid used in CFD analysis onto a node-based grid used in FEM. Based on temperature distribution, the stresses and deformation within the cylinder head were calculated.

CFD Analysis of Compressible Flow Across a Complex Geometry Venturi

A commercial computational fluid dynamics (CFD) package was used to develop a three-dimensional, fully turbulent model of the compressible flow across a complex-geometry venturi, such as those typically found in small engine carburetors. The results of the CFD simulations were used to understand the effect of the different obstacles in the flow on the overall discharge coefficient and the static pressure at the tip of the fuel tube. It was found that the obstacles located at the converging nozzle of the venturi do not cause significant pressure losses, while those obstacles that create wakes in the flow, such as the fuel tube and throttle plate, are responsible for most of the pressure losses. This result indicated that an overall discharge coefficient can be used to correct the mass flow rate, while a localized correction factor can be determined from three-dimensional CFD simulations in order to estimate the static pressure at locations of interest within complex venturis.

Computational Fluid Dynamics Analysis for Process Impact Assessment during Thermal Pasteurization of Intact Eggs

Transient temperature and albumen velocity profiles during thermal pasteurization of intact eggs were studied using a commercial computational fluid dynamics (CFD) package. Simulated temperature profiles were in close agreement with experimental data for eggs of different sizes. Convective heat transfer only occurred in the egg white fraction, and conductive heat transfer only occurred in the yolk. For process assessment, a generally accepted kinetic inactivation model for Salmonella Enteritidis was incorporated into the CFD analysis. Minimum process times and temperatures needed to provide equivalent pasteurization at 5-log reductions of the target microorganism were obtained on a theoretical basis. The combination of CFD analysis and inactivation kinetics can be very useful for assessing pasteurization of intact eggs and can enable processors to gain a better understanding of these processes and to establish process conditions for consumer-safe eggs.

CFD Analysis of the First-Stage Rotor and Stator in a Two-Stage Mixed Flow Pump

A commercial computational fluid dynamics (CFD) code is used to compute the flow field within the first-stage rotor and stator of a two-stage mixed flow pump. The code solves the 3D Reynolds-averaged Navier-Stokes equations in rotating and stationary cylindrical coordinate systems for the rotor and stator, respectively. Turbulence effects are modeled using a standardk−εturbulence model. Stage design parameters are rotational speed890 rpm, flow coefficientφ=0.116, head coefficientψ=0.094, and specific speed2.01(5475 US). Results from the study include velocities, and static and total pressures for both the rotor and stator. Comparison is made to measured data for the rotor. The comparisons in the paper are for circumferentially averaged results and include axial and tangential velocities, static pressure, and total pressure profiles. Results of this study show that the computational results closely match the shapes and magnitudes of the measured profiles, indicating that CFD can be used to accurately predict performance.