Flow Computational Fluid Research Articles

Flow Pattern and Pressure Drop for Small Long‐Cylinder Cyclones Operating at High Flow Rates

AbstractTo address the gas flow pattern and pressure drop characteristics for small long‐cylinder cyclones (SLCCs) in the high operating flow rate range, experimental investigation and computational fluid dynamics (CFD)‐based simulation were performed. The pressure drop coefficient depends insignificantly on the Reynolds number at high flow rates. The tangential and axial velocities present the Rankine vortex and the roughly inverted V‐shaped distribution, respectively, similar to those in typical cyclones. The CFD simulation approximated well the experimental data of pressure drop. The pressure drop caused by vortex loss, turbulent energy loss, and resistance loss accounted for 72.5 % of the total pressure drop. The Stairmand model was found to be relatively accurate among the classical pressure drop models for the proposed cyclone. The results may help in the design and applications of cyclone separators and reactors.

A Novel Simulative-Experimental Approach to Determine the Permeability of Technical Textiles

Since years, fiber reinforced polymer composite (FRPC) parts made by Liquid composite molding (LCM) make up a significant share of the composite market. In LCM dry reinforcing structure gets impregnated with a resin system. Permeability, a material parameter with key influence on all LCM processes, quantifies the conductance of technical textiles for resin flow. Today, when a numerical filling simulation is applied for process design, large experimental test programs are required for characterization of permeability, as the permeability has to be measured for all textiles processed and also the dependency e.g. on the fiber volume content has to be considered. Together with Math2Market GmbH (M2M), the IVW currently develops a novel simulative-experimental approach (SEA), using experimental tests to calibrate a simulation model for replacing a significant amount of the experimental tests through “virtual” measurements. In a first step the functionality of the simulation and the most appropriate methods for textile modelling were investigated. For this, three routes were followed: At first a micro-computer tomograph (μCT)-scan of a glass fiber non-crimp fabric was fed into GeoDict, the material simulation software developed by M2M. Second, a digital model (DM) of the textile was created by computer modelling of basic structure and subsequent virtual compaction. μCT-model and DM were then used for computational fluid flow simulation which gives the direction-dependent permeability as an output. The DM calibrated by experiments represents the SEA and results in the digital twin. Third route was the experimental permeability measurement to generate reference values. Comparing the results of all three routes allows statements about the functionality of the simulation and accuracy of modelling. The rather deficient correlation between the results of experiments and μCT-model based simulations revealed that segmentation is a remarkable source of error despite the use of recognized methods. Different modeling approaches were followed to build up the digital twin. The best results were achieved with models undergoing a virtual compaction step, which takes various imperfections such as yarn deformation and varying nesting behavior into account. With this 2.25 - 6.75% deviation from the experimental results at an average standard deviation of 21.9 - 61.2% were achieved. Hence, the digital twin shows a better correlation than the μCT-model and high potential for substitution of experiments. Even better results are expected when in a next step a local anisotropic permeability will be allocated to the yarns.

Numerical Simulations of Electromagnetic Counteractions to Mold Fluid Flow Asymmetry Deviations

Asymmetric flow of the molten steel in a continuous slab casting mold may be detrimental to the quality of the solidified end product. Depending on the severity of the biased flow, local mold powder entrainment, non-homogeneous solidification around the perimeter of the initial shell or non-optimal inclusion seclusion may occur. In particular, nozzle clogging in the last slabs before an SEN exchange may cause strong and asymmetries in the upper regions of the mold. To avoid costly downgrades of steel quality in these slabs, it is vital to maintain stable and symmetric fluid flow conditions in the mold. The EMBR and the FC Mold are two flexible electromagnetic devices able to produce asymmetric braking/stirring along the width of the mold in slab casting, and in this way allow counteraction against e.g. biased mold flow or local excessive flow speeds. Numerical computations of mold fluid flow and magnetic flux have been carried out to quantify the required fields to symmetrize biased flow scenarios caused by e.g. SEN clogging. In conjunction with steel plant trial feedback, the simulation results have been used to setup control algorithms for the EMBR and FC Mold.

A partitioned solution algorithm for fluid flow and stress-strain computations applied to continuous casting

Continuous casting is currently the main industrial process for steel production. Since long time, industries search for efficient simulation methods, by which macrosegregation and deformation induced cracks can be predicted. As a first step this requires achieving concurrent simulation of fluid flow and stress-strain. Therefore, a partitioned solution algorithm is developed for such simulation with application to continuous casting. Liquid flow induced by natural convection or filling step, solidification shrinkage as well as thermally induced deformation of solid phase are accounted for.

Permeability versus Design in TPMS Scaffolds.

Scaffolds for bone tissue engineering are porous structures that serve as support for cellular growth and, therefore, new tissue formation. The present work assessed the influence of the porous architecture of triply periodic minimal surface (TPMS) scaffolds on their macroscopic permeability behavior, combining numerical and experimental methods. The TPMS scaffolds considered were Schwartz D, Schwartz P, and Gyroid, which have been previously studied for bone tissue engineering, with 70% porosity. On the experimental side, these scaffolds were produced by MultiJet 3D printing and tested for fluid passage to calculate their permeability through Darcy’s Law. On the numerical side, finite element (FE) models of the scaffolds were simulated on ABAQUS® for fluid passage under compression to assess potential fluid concentration spots. The outcomes revealed that the design of the unit cell had a noticeable effect on both calculated permeability and FE computed fluid flow velocity, regardless of the identical porosity, with the Gyroid scaffold having higher permeability and the Schwartz P a lower probability of fluid trapping. Schwartz D had the worst outcomes in both testing modalities, so these scaffolds would most likely be the last choice for promoting cell differentiation onto bone cells. Gyroid and Schwartz P would be up for selection depending on the application and targeted bone tissue.

An Efficient Iterative Method for Looped Pipe Network Hydraulics Free of Flow-Corrections

The original and improved versions of the Hardy Cross iterative method with related modifications are today widely used for the calculation of fluid flow through conduits in loop-like distribution networks of pipes with known node fluid consumptions. Fluid in these networks is usually natural gas for distribution in municipalities, water in waterworks or hot water in district heating systems, air in ventilation systems in buildings and mines, etc. Since the resistances in these networks depend on flow, the problem is not linear like in electrical circuits, and an iterative procedure must be used. In both versions of the Hardy Cross method, in the original and in the improved one, the initial result of calculations in the iteration procedure is not flow, but rather a correction of flow. Unfortunately, these corrections should be added to or subtracted from flow calculated in the previous iteration according to complicated algebraic rules. Unlike the Hardy Cross method, which requires complicated formulas for flow corrections, the new Node-loop method does not need these corrections, as flow is computed directly. This is the main advantage of the new Node-loop method, as the number of iterations is the same as in the modified Hardy Cross method. Consequently, a complex algebraic scheme for the sign of the flow correction is avoided, while the final results remain accurate.

Single-Phase Instability in Non-Premixed Flames Under Liquid Rocket Engine Relevant Conditions

Under rocket-relevant conditions, real-gas effects and thermodynamic nonidealities are prominent features of the flow field. Experimental investigations indicate that phase separation can occur, depending on the operating conditions and on the involved species in the multicomponent flow. During the past decades, several research groups in the rocket combustion community have addressed this topic. In this contribution, a high-fidelity thermodynamic framework comprising real-gas and multicomponent phase-separation effects is employed to investigate liquid-oxygen/methane and liquid-oxygen/hydrogen flames at high pressure. A thorough introduction and discussion on multicomponent phase separation are conducted. The model is validated with experimental data and incorporated in a reacting flow computational fluid dynamics code. Using one-dimensional counterflow diffusion flames, the thermodynamic states and processes are discussed. Both real-gas and phase-separation effects are present and quantified in terms of derived properties. Finally, the method is applied in a three-dimensional Large-Eddy Simulation of a single-element reference test case, and the results are compared to experimental data.

Integrated experimental and computational approach for nanoparticle flow analysis

We report a new method combining computational fluid dynamics and flow experiments with customized channels to understand the transport of nanoparticles. Iron oxide nanoparticles, being highly attractive for biomedical research are chosen as model nanoparticles for the transport studies. Four different polyvinyl pyrrolidone and polyethyleneimine coated iron oxide nanoparticles of hydrodynamic sizes ranging from 45–178 nm were synthesized. These nanoparticles were adjusted to different target mass concentrations and ran through a bent tube to determine flow velocity and mass loss, specific to the nanoparticles. Computational predictions were made for velocity and mass loss of fully developed flow of nanoparticles through bent channel, which compared well with experimental measurements. A diffusion dominated nanoparticle flow is predicted, based on our results. This work will provide a breakthrough for further experimental and computational research to help understand the nanoparticle targeted delivery and the design of nanoparticles for optimal delivery in biomedical applications.

Wave impact pressure and kinematics due to breaking wave impingement on a monopile

Breaking wave impact on a vertical cylinder in shallow waters is investigated numerically with the two-phase flow computational fluid dynamics model REEF3D. The model is based on the incompressible Reynolds-Averaged Navier-Stokes (RANS) equations together with the level set method (LSM) and k−ω turbulence model. The spatial and time development of the maximum wave impact pressure and the associated velocity components are examined. Further, the breaking wave characteristics and geometric properties are evaluated with two-dimensional simulations. Comparisons of numerical results and experimental data indicate good agreement for free surface elevations and the characteristics at breaking and the breaking wave forces. A total of 9 two-dimensional and 27 three-dimensional simulations are performed to investigate the influence of the incident wave characteristics, wave impact conditions and breaker types on the maximum wave impact pressure and kinematics. The factors influencing the spatial and temporal variability of the vertical distribution for the maximum impact pressure and kinematics are investigated. Three impact conditions are considered in this study: (1) the wave with a vertical front breaks at the cylinder, (2) the broken wave hits the cylinder with a moderately developed overturning wave crest, and (3) the broken wave impacts the cylinder with a fully developed overturning wave crest. Further, the vertical and longitudinal variations of the maximum impact pressure during the breaking wave impact on the monopile are assessed. The numerically simulated free surface deformations during the wave impact are also presented and discussed. Finally, the total breaking wave force and the maximum impact pressure are analyzed for spilling and plunging breakers under different wave impact conditions.

Image-based spatio-temporal model of drug delivery in a heterogeneous vasculature of a solid tumor — Computational approach

The solute transport distribution in a tumor is an important criterion in the evaluation of the cancer treatment efficacy. The fraction of killed cells after each treatment can quantify the therapeutic effect and plays as a helpful tool to evaluate the chemotherapy treatment schedules. In the present study, an image-based spatio-temporal computational model of a solid tumor is provided for calculation of interstitial fluid flow and solute transport. Current model incorporates heterogeneous microvasculature for angiogenesis instead of synthetic mathematical modeling. In this modeling process, a comprehensive model according to Convection-Diffusion-Reaction (CDR) equations is employed due to its high accuracy for simulating the binding and the uptake of the drug by tumor cells. Based on the velocity and the pressure distribution, transient distribution of the different drug concentrations (free, bound, and internalized) is calculated. Then, the fraction of killed cells is obtained according to the internalized concentration. Results indicate the dependence of the drug distribution on both time and space, as well as the microvasculature density. Free and bound drug concentration have the same trend over time, whereas, internalized and total drug concentration increases over time and reaches a constant value. The highest amount of concentration occurred in the tumor region due to the higher permeability of the blood vessels. Moreover, the fraction of killed cells is approximately 78.87% and 24.94% after treatment with doxorubicin for cancerous and normal tissues, respectively. In general, the presented methodology may be applied in the field of personalized medicine to optimize patient-specific treatments. Also, such image-based modeling of solid tumors can be used in laboratories that working on drug delivery and evaluating new drugs before using them for any in vivo or clinical studies.

Computational Fluid Flow Study on the Pressure Fluctuation Caused by the Vortex Flow Arising from Underwater Exercises of Arthritis Patients

Underwater exercise programs are among the nursing programs for which positive effects have been reported with regard to the promotion of good health in diverse subjects, such as patients suffering arthritis, as well as elderly people and middle-aged women. Through many previously conducted studies, subjects participating in underwater exercises have been reported to continuously experience reduced pain, and improvement in muscle strength, flexibility, sense of balance, and muscular endurance. However, few studies have delved into the fundamental phenomena of positive effects of underwater exercises on the human body. In this study, a model of the upper limbs of the human body was used in a simulation of underwater exercises to analyse the resulting pressure fluctuation on the skin of the hands and arms of the model through the methods of computational fluid dynamics. During the simulation of underwater exercises, pressure fluctuation of diverse frequencies, arising from the vortex flow around the articulations of the fingers and hands of the model, were identified and were seen to create varied cutaneous stimulations and massage effects. Such cutaneous stimulations seem to continuously excite capillary vessels situated between hands and finger joints, creating positive effects in blood circulation around pain sites of patients suffering from arthritis.

Numerical investigation of an advanced U-RANS based pressure fluctuation model to simulate non-linear vibrations of nuclear fuel rods due to turbulent parallel-flow

Nuclear reactor designs such as PWR and BWR are susceptible to vibrations induced on the nuclear fuel rods due to fast flowing coolants around the rods. The non-linear behaviour of flexible components have always been a challenge to compute especially when dealing with strongly coupled fluid–structure interaction cases as found in the reactors. Simulating such a behaviour involves a two-way coupling of a well resolved turbulent flow Computational Fluid Dynamics (CFD) solver to a Computational Solid Mechanics (CSM) solver. The use of a high fidelity CFD solver to resolve turbulent flows in an FSI (Fluid-Structure Interaction) simulation is computationally expensive ergo is not practical in for industrial purposes. To address this issue, a different approach is discussed in this article to simulate turbulence induced vibrations through the use of U-RANS models. The method is based on computing the modeled turbulent pressure and velocity fluctuations from values obtained by solving U-RANS (Unsteady-Reynolds Averaged Navier Stokes) equations. The calculated turbulent fluctuating field is combined with mean values to compute an instantaneous turbulent pressure field to apply an external pressure and shear force on the structure and vice-verse until convergence is achieved. This method can be used to accurately estimate the behaviour of a flexible structure in a turbulent flow. The article provides a detailed explanation of the model followed by validation with three numerical test cases. The first case involves a CFD simulation where results from the pressure fluctuation model (PFM) is compared to a benchmark DNS (Direct Numerical Simulation) of a turbulent channel flow with friction Reynolds number, Reτ=640. Later the PFM is applied to a 2-dimensional strongly-coupled FSI simulation with a flexible steel flap in turbulent water flow to study the feasibility and stability of PFM applied to an FSI problem. Finally, the PFM is used to simulate an experimental case of a brass rod excited by turbulent water performed by Chen and Wambsganns (1972). The results show that the PFM is capable of simulating turbulence induced vibration (TIV) with low-fidelity U-RANS models.

A Liquid-Solid Two-phase Flow Computational Fluid Dynamic Modelling of the Operational Characteristics Effects on the Cleaning Time of a Circulating Flow Loop

Flow loops and computational fluid dynamics are the main research approaches for resolving the hole-cleaning problems. Cutting transport phenomena can be considered as a Computational Fluid Dynamic (CFD) model by using Eulerian assumptions for the turbulent liquid-solid flow in concentric annuli. The effect of time along with the main operational characteristics on the hole-cleaning phenomena is not negligible but recent studies have had paid little attention to it. Poor near bit cleaning causes many problems such as bit balling, decline in the rate of penetration, pipe sticking, etc. In addition to the effect of inclination, drill pipe rotary speed, cutting size, nozzle velocity and fluid viscosity as well as the effect of the bit nozzle arrangement on the cutting transport process were discussed. The results demonstrate that at a critical inclination angle of 30 degrees the cutting transport is inefficient. For all sections, the effect of drill pipe rotary speed was negligible at high velocities. In the horizontal section, at low flow rates and high drill pipe rotation speeds, Newtonian viscous fluids or water has no effect on the time needed for initial hole-cleaning butby removing the drill pipe rotation speed in similar conditions, a dramatic influence on time is observed. In inclined annuli, increasing the cuttings size and decreasing the nozzle velocity result in having no cutting in the output. Under critical inclination (30 degrees) the effect of the nozzle angle pattern on the hole-cleaning time is negligible. However, for a vertical annulus, the nozzle angle significantly influences the cutting transport. The best performance is obtained when the nozzle angle was perpendicular to the drill pipe axes. Keywords: Two-phase flow, flow characteristics, CFD, jetting flow.

FLUID FLOW CHARACTERISTICS IN DOUBLE-SIDED LID-DRIVEN MICROCAVITY USING LATTICE BOLTZMANN METHOD

In this study, we analyze the fluid flow characteristic of rarefied gas flows in double-sided lid-driven microcavity subjected to various combinations of boundary conditions that simulate the slip at the walls using lattice Boltzmann method (LBM) constituting a single relaxation time (SRT) model. The fluid motion inside a closed square container with two rigid walls and two moving walls constitutes an exemplar for internal vortex flows. First, a complicated geometry, namely, the single-sided lid-driven microcavity is studied using the LBM-SRT model. Next, this code is extended to simulate flows in a double-sided microcavity flow. Numerical computation of fluid flow incorporating various slip boundary conditions as bounce-back and specular boundary condition (BSBC) for different values of tangential accommodation momentum coefficient (TMAC) has been investigated. Various values of Knudsen number in the slip and transition regime (Kn = 0.01, 0.05, 0.10, 0.135, and 0.15) along with different aspect ratios of 0.33, 0.50, 1.0, 2.0, and 3.0 have been considered in this study. The streamline patterns and velocity profiles were obtained for different Knudsen numbers. The formation and movement of primary vortices have been well captured with the variation of Knudsen numbers for different aspect ratios of microcavity.

CONCEPTUAL DEVELOPMENT OF THE EARTH TUBE COOLING SYSTEM FOR A TALL BUILDING

ABSTRACT Earth tubes are earth-to-air heat exchangers that are frequently utilized in energy conscious low-rise buildings, but are scarcely reported for tall buildings. The feasibility of applying earth tube cooling to tall buildings in a hot summer and cold winter climate zone was studied in this paper. Firstly, the designed cooling load of a tall building was obtained from the energy simulation using the baseline and the modified models with applicable energy efficiency measures. Based on the load, the required cooling capacity, the overall section area and the effective length of the earth tube system was deduced from the heat transfer and fluid flow calculation analytically. Then the performance of the earth tube system was crosschecked and verified via the Computational Fluid Dynamics (CFD) simulation. In the CFD simulation, earth tubes with different diameters and lengths, as well as a full-scale earth tube model with surrounding soil above the depth of constant temperature, were investigated. The outlet air temperatures of the full-scale models were computed with the consideration of different axial distances between adjacent tubes. Meanwhile, multiple conceptual design schemes and the tunnel construction method for the earth tube system were proposed from the perspective of performance enhancement, constructability, efficiency and economy. It revealed that earth tube systems are conditionally feasible for some tall buildings if their design guidelines for climate, underground spaces, construction method, friction of tube interior surface, optimization of effective length and axial distance, as well as synergy with other energy efficiency measures are followed. Even the cooling capacity of earth tubes degrade with time due to the accumulated heat underground, but in a hot summer and cold winter climate zone it can still possibly produce cooled air for a tall building with a Floor Area Ratio of less than 7 effectively in summer.

Local Concentrating, Not Shear Stress, That May Lead to Possible Instability of Protein Molecules During Syringe Injection: A Fluid Dynamic Study with Two-Phase Flow Model.

A two-phase flow computational fluid dynamic (CFD) model was developed to study the hydrodynamic forces and the protein concentration changes of a protein solution in a syringe injector. Proteins were assumed to be nanosized solid spheres commensurate with their molecular weight and suspended in an aqueous environment, passing through the rapidly constricted sections of the syringe. Interaction between the solid and the liquid phase was taken into account, and four laminar flow cases were studied under the extensional flow. Profiles of pressure, velocity, and shear stress of the different cases were examined and compared. Hydrodynamic forces on a single protein particle were further analyzed. Our results indicate that the hydrodynamic forces are too small to affect significant conformational changes in proteins. The plunger rate showed limited impact on the distribution of protein particles inside the syringe. Nonetheless, the larger velocity gradient at the connection section of the hub toward the needle resulted in considerable accumulation of proteins. Such a concentrating effect may lead to protein aggregation and subsequent structural changes and will be examined in future studies.LAY ABSTRACT: Concentrated protein in the liquid form has become a preferred formulation strategy for delivering protein products, but it suffers from a high possibility of aggregation and precipitation, which may trigger a structural change and denaturation of the protein molecules and eventually cause the loss of the therapeutic functions of the protein products. To understand the effect of hydrodynamic forces on the change in local protein concentration in a syringe injector, we developed a two-phase flow computational fluid dynamic (CFD) model in this work. It was found that the local concentration of protein strongly depends on the velocity gradient of the fluid. A higher amount of proteins accumulates at the connection section of the hub toward the needle where the maximum velocity gradient is exhibited. The model results also imply a limited effect by hydrodynamic forces on possible unfolding of protein molecules. The local concentrating effect may enhance the possibility of molecular collision, resulting in aggregation and structural change.

Calculation of static pressure field of liquid phase in the active zone of cavitation-jet deaerator

In cavitation-jet deaerators, the process of desorption of dissolved gases proceeds when boiling overheated water is directed in the form of a swirling vortex flow into the rarefaction zone. The removal of gases is carried out from the cavitation pocket formed along the flow axis. Such deaerators are characterized by relatively low efficiency. However, their small dimensions and the ability to work without supplying a heating coolant make them useful in cases where effective deaerators of other types cannot be applied by weight and size characteristics or temperature conditions. The expansion of the scope of practical application of cavitation-jet deaerators is hampered by the lack of appropriate mathematical description that would allow solving the problems of their schematic and constructive improvement. One of the main tasks in this case is to calculate the static pressure field of the liquid phase in the deaerator core. There are no ready-made solutions to this problem in the framework of previous studies. Thus, it is relevant from scientific and practical viewpoint to develop a simulation model of active zone of cavitation-jet deaerator, which allows determining the hydrodynamic characteristics of water flows and gas-vapor mixture when the elements, the mode of water supply and drainage evaporation change. Modeling the hydrodynamic situation in the active zone of cavitation-jet deaerator is based on the numerical solution for the Navier-Stokes equations and the continuity equation. These equations are written in the Reynolds decomposition. In this case, the standard k- turbulence model is used to obtain a preliminary solution, which is then refined during the transition to the SST turbulence model. The model is implemented by means of a software package for calculating fluid flows FlowVision. For the first time, a simulation model of the active zone of cavitation-jet deaerator was developed, which made it possible to determine the hydrodynamic characteristics of water flows and gas mixture when the elements design, the mode of water supply and drainage evaporation change. The field of static pressures of liquid phase in the active zone of cavitation-jet deaerator is determined. The results obtained do not contradict the published data describing the operation of cavitation-jet deaerators. In particular, they confirm an increase in the probability of deaerator overflow when gas exhaust is turned on. The results also prove the presence of a significant dependence of the deaeration efficiency on the hydraulic resistance of the evaporation suction tract. Based on the results obtained, a mathematical model of the deaeration process under the considered conditions can be developed.

URANS and ACM for determining the aerodynamic performance of vertical-axis wind turbine

This paper presents numerical results of a one-bladed vertical axis wind turbine using the k-ε RNG turbulence model. The rotor geometry was developed based on the research report available on the literature. The obtained results of aerodynamic blade loads and wake profiles downstream behind the rotor are in a good agreement with the experiment. This paper presents also the ability of calculating fluid flow parameters around the operating wind turbine by using the original approach – the actuator cell model (ACM).

ДО ПИТАННЯ О РОЗРОБЦІ ПРОГРАМНО-ОБЧИСЛЮВАЛЬНОГО КОМПЛЕКСУ ТЕПЛОГІДРАВЛІЧНОГО ПРОЦЕСІВ В МАСЛОСИСТЕМІ ГТД

Currently, in connection with the creation of aircraft engines of new generations, as well as increasing requirements for the efficiency of their design and development processes, more attention is paid to the creation of a software and computing complex with respect to the thermal and hydraulic processes in the GTE oil system. In the development of modern aircraft engines, special attention is paid to increasing the resource, reducing the mass and dimensions of the engine. Conditions for the long-term operation of the gas turbine engine cause specific requirements for individual elements and their oil systems. Effective development of a new generation of gas turbine engines is largely ensured by the introduction of automated engine oil system design systems. Increasing the efficiency of gas turbine engines and the development of new technologies in propulsion engineering inevitably sets the task of oil systems improving. A promising direction is the creation of a software and computer complex with respect to the thermal and hydraulic processes in the GTE oil system. When designing the GTE oil system, it becomes necessary to calculate the exact oil consumption and pressure losses in the pipelines, calculate the heat exchange between the oil and the elements of the lubrication system, calculate the critical flow regimes in the pipelines and local resistances. The task was to create an adequate software and computer complex for the calculation of thermal hydraulic processes applied to the GTE oil system, depending on the influence of key parameters. On its basis in the future, a thermal model of the oil system will be constructed, which will allow to determine the thermal state of the oil and the support elements of the GTE rotor. In the future, the software and computing complex will be adapted for the calculation of two-phase fluid flow, namely oil and air. Studies in the presented areas require theoretical approaches to solving problems, the use of modern software packages for conducting numerical experiments and the availability of a bench base. The article shows the structure of the software and computing complex with respect to the thermal and hydraulic processes in the GTE oil system.

بهینهسازی هندسی اجکتور فراصوتی برای بهبود عملکرد آن در سیستمهای تبرید

Due to an increasing need for refrigeration systems and their growing electrical demand and greenhouse gases production, using ejector refrigeration systems would be a suitable substitution for conventional cooling systems. Main drawback of ejector refrigeration systems is their low coefficient of performance. The key component to improve the cycle performance is the ejector. Prerequisite of improving ejector performance is an accurate computational fluid dynamics simulation for predicting its entrainment ratio. In this study, a two dimensional, axisymmetric, steady state, compressible flow computational fluid dynamics simulation of a supersonic ejector is performed. In the second part of this study, geometrical optimization of the simulated ejector for two different objective functions is performed. The first objective function considered was the ejector entrainment ratio. The optimization with this objective function led to 53% relative improvement in the entrainment ratio with a negligible decrease in critical pressure. The second, objective function considered was the exergy efficiency in which the optimization showed 39.6% relative improvement. The exergy efficiency is used for the first time in the literature as the objective function for optimization of ejector geometry.