ANSYS CFX Software Research Articles

A novel trussed fin-and-elliptical tube heat exchanger with periodic cellular lattice structures

PurposeThis study aims to computational numerical simulations to clarify and explore the influences of periodic cellular lattice (PCL) morphological parameters – such as lattice structure topology (simple cubic, body-centered cubic, z-reinforced body-centered cubic [BCCZ], face-centered cubic and z-reinforced face-centered cubic [FCCZ] lattice structures) and porosity value ( ) – on the thermal-hydraulic characteristics of the novel trussed fin-and-elliptical tube heat exchanger (FETHX), which has led to a deeper understanding of the superior heat transfer enhancement ability of the PCL structure.Design/methodology/approachA three-dimensional computational fluid dynamics (CFD) model is proposed in this paper to provide better understanding of the fluid flow and heat transfer behavior of the PCL structures in the trussed FETHXs associated with different structure topologies and high-porosities. The flow governing equations of the trussed FETHX are solved by the CFD software ANSYS CFX® and use the Menter SST turbulence model to accurately predict flow characteristics in the fluid flow region.FindingsThe thermal-hydraulic performance benchmarks analysis – such as field synergy performance and performance evaluation criteria – conducted during this research successfully identified demonstrates that if the high porosity of all PCL structures decrease to 92%, the best thermal-hydraulic performance is provided. Overall, according to the obtained outcomes, the trussed FETHX with the advantages of using BCCZ lattice structure at 92% porosity presents good thermal-hydraulic performance enhancement among all the investigated PCL structures.Originality/valueTo the best of the authors’ knowledge, this paper is one of the first in the literature that provides thorough thermal-hydraulic characteristics of a novel trussed FETHX with high-porosity PCL structures.

Numerical analysis of hydrodynamic and thermal characteristics of three inside channel configurations of a plate and shell heat exchanger (PSHE)

The Plate and Shell Heat Exchanger (PSHE) is a variation of the Plate Heat Exchanger (PHE) with a more compact and robust geometry. This paper presents the analysis of the flow in the inner channel formed by a pair of plates of a PSHE employing computational fluid dynamics to determine the hydrodynamic and thermal characteristics for three Chevron angle configurations, 15° × 15° (High/High-HH), 45° × 45° (Low/Low-LL) and 15° × 45° (High/Low-HL). The ANSYS CFX software was employed with the application of the Standard k-ε and the SST (Shear-Stress-Transport) turbulence models for comparison. Experimental pressure drop data and flow streamlines were used to validate the numerical model and to analyze simplifications in the geometric model. Pressure drop, friction factor, and Nusselt number were evaluated for the three geometries studied. A local analysis of the parameters that describe the channels was also performed in this study.

Study on the Effect of the Guide Vane Opening on the Band Clearance Sediment Erosion in a Francis Turbine

Sediment erosion is a negative phenomenon for the water turbine. The purpose of this paper is to study the effect of the guide vane opening on the particle motion and sediment erosion in the band chamber using the Euler–Lagrangian approach. The software Ansys CFX and Tabakoff erosion model are used to simulate the sediment laden flow in the full flow passage of the hydraulic turbine. The results are in good agreement with the actual erosion character on site. Results show that the guide vane opening has a positive correlation with the flow in the non-clearance channel. The increase of the guide vane opening will increase the erosion of the runner blade head, but the friction wear on the outlet side of the blade surface will decrease. The rotating action of the runner makes the sediment particles in the band chamber rotate rapidly around the center of the runner and constantly collide with the band chamber wall. Under the small opening, the smaller the opening, the easier the leakage of the band clearance occurs. The unsteady flow in the band chamber will disturb the motion trajectory of particles, change the impact angle of particles, and affect the wear in the band chamber. Under different openings, the change law of the erosion in the band clearance is closely related to the change law of clearance leakage.

Vortex rope interaction with radially protruded solid bodies in an axial turbine: a numerical study

Radially protruded solid rods and their interaction with the rotating vortex rope at part load condition are investigated numerically on an axial model turbine.The commercially available software ANSYS CFX was used to perform the simulation, and the test case was the Porjus U9 Kaplan turbine model operating at a fixed runner blade angle at part load condition. Four rods, with a rod diameter equal to 15% of the runner diameter were evenly distributed in a horizontal plane in the draft tube cone and protruded to a length set to intercept the RVR in its unperturbed trajectory. It is shown that the RVR plunging (synchronous) mode is completely mitigated upstream and downstream of the protruded rods. The RVR rotating (asynchronous) mode is reduced by 47% and 63% at the two monitor positions located upstream of the protruding rods, while only a minor reduction occurs to the first RVR harmonic at the monitor positions located downstream of the protruded rods. The perturbed RVR experiences an increased angular velocity due to the flow area decrease caused by the protruding rods, thus increasing the RVR frequency by approximately 53% compared to the unperturbed value. Investigation of the swirling flow indicates a locally increased swirl in the center of the draft tube downstream of the protruded rods which could explain the reduction of the RVR pressure amplitude. The overall turbine efficiency with solid rods protruded causes a marginally efficiency reduction of 0.85%. However, as the RVR pressure pulsations are reduced significantly, a more comprehensive investigation of the rods impact on the turbine performance and life time should be performed to elucidate the suitability of using solid rod protrusion for RVR mitigation.

Computational Investigation of Vertical Axis Wind Turbine in Hydrogen Gas Generation Using PEM Electrolysis

Both offshore wind and hydrogen generation are increasingly seen as central to global decarbonization. The objective of current research is to investigate the effect of wind turbine height of Vertical Axis Wind Turbine (VAWT) on hydrogen generation. The numerical investigation of VAWT is conducted using techniques of Computational Fluid Dynamics. The VAWT design is developed in Solidworks design software and CFD analysis is conducted using ANSYS CFX software. The CFD analysis conducted on VAWT aided to determine the torque generated from it at 10m/s wind velocity determining the system impacts and ability of electrolyzer technology to accommodate the varying input from wind turbine. The research findings have shown that height of VAWT blade has significant effect on power generation. The power generation from VAWT increases with increase in blade height. The maximum hydrogen mass is generated for 850mm height wind turbine i.e., 2.09Kg. The external wind flow conditions have significant effect on power generation from VAWT and therefore the effect of varying air flow conditions needs to be investigated.

Study of New Mini-Channel Trans-Critical CO2 Heat Pump Gas Cooler.

A gas cooler is one of the important parts of a carbon dioxide (CO2) heat pump water heater, and it must meet the needs of not only pressurization but also heat transfer. It is important to study gas coolers. In this paper, a heat exchanger with a spiral channel is studied. ANSYS CFX software was used to analyze the flow and heat transfer characteristics of the heat exchanger (single-plate model). The influences of the cooling pressure of CO2, the mass flux of CO2, the mass flux of water and the channel radius of CO2 are discussed. In this paper, the results show that the cooling pressure of CO2, the mass flux of CO2 and the channel radius of CO2 all have a large influence on the local heat transfer coefficient: with an increase in the cooling pressure of CO2, the peak value of the heat transfer coefficient of CO2 decreases and the average heat transfer coefficient decreases; with an increase in the mass flux of CO2, the peak value of the heat transfer coefficient of CO2 increases and the average heat transfer coefficient increases; and with a decrease in the channel radius of CO2, the peak value of the heat transfer coefficient of CO2 increases. The water mass flux has only a slight effect on heat transfer, and the lower cooling pressure of CO2 corresponds to a higher peak heat transfer coefficient, which can reach 27.5 kW∙m−2∙K−1 at 9 MPa.

Super-Resolution Study Of Wall Sheer Stress In Cerebral Aneurysm With AI PIV

Aneurysms are one of the most common unexplored causes of death. There are many studies conducted by scientists around the world on this issue. The main problem raised is the cause of aneurysms. Here, the division includes several branches, i.e. genetic conditions, lifestyle, eg. smoking, and finally hemodynamic factors of blood flow. It is well known that the aneurysm is formed and ruptured at the site of high wall shear stress (WSS). This paper presents the comparison of results of CFD blood flow simulations with experimental values obtained with the Particle Image Velocimetry (PIV) method in a 3D model of a cerebral aneurysm. A 3D model of a cerebral aneurysm was developed using specific patient CT data. The hemodynamical parameters were analysed for different flow rates in a 3D model under pulsatile flow conditions. The CFD simulation was done using Ansys CFX software. Results of the simulation were validated with the experimental PIV method. Two different PIV methods were employed: traditional PIV based on cross-correlation (CC) algorithms and Artificial Intelligence PIV (AI PIV) based on Deep Learning and Convolutional Neural Networks. The obtained results showed a better correlation between CFD simulation and types of PIV analysis for data of AI PIV, which allows for a much higher spatial resolution of the resulting velocity field. Analysis of the results was promising and showed that AI PIV could be used to get accurate results.

Influence of pad geometry and method of oil supply on the thermal state of GTE rotor tilting-pad journal bearing

High heat generation in the hydrodynamic wedge is one of the main factors limiting application of pad journal bearings as bearings for rotors of aircraft gas turbine engines. The goal of the research is to study the influence of the oil supply method on the bearing thermal state and to determine the design factors reducing the bearing temperature. The study was carried out with the use of bearings with diameters of 100320 mm with different design of the oil supply: through oil dispensing grooves in the pads, through oil nozzles in the inter-pad space, using lead-in chamfers for the pads, with oil bypass channels. The tasks posed were solved by using volumetric geometric models with the tools of computational fluid dynamics in the ANSYS CFX package in which differential equations describing the model are solved by the finite element method. The patterns of temperature and pressure distribution over the surface of the lower, most loaded bearing pad were obtained for various options of oil supply and different geometry of bearing pads; values of the bearing load carrying capacity, maximum pressure in the working gap, the oil mass flow through the elements of the oil supply; dependences of the bearing static performance on the distance between the shaft and nozzles. Oil supply through oil dispensing grooves made in pads is a factor that negatively affects the bearing thermal state, which is associated with so-called locking of the working gap. It is shown that implementation of oil supply through the space between the pads is more efficient. The use of a lead-in chamfer with plain inserts simplifies oil supply to the working gap. The design solutions described make it possible to reduce the maximum oil temperature in the bearing by 36 degrees Celsius.

Разработка модели утилизационной газовой турбины

The demand for electricity is growing due to industry development in the world. Thus, the issue to obtain energy using installations that use secondary energy resources is relevant. In this regard, it is important to carry out the research on the operation of such installations. There are many ways to study the operation of turbines as one of the types of installations that uses secondary energy resources. For this purpose, such visual environment as ANSYS allows you to get a visual 3D representation of the turbine operation. Thus, an urgent task is to develop a numerical determined turbine model in the ANSYS CFX package and then adapt it based on experimental data. The model based on numerical experiments can be used to find ways to increase the electricity output. The top-pressure recovery turbine GUBT-25 is chosen as the object of the research. During the research the professional analytical ANSYS CFX software has been used to solve thermal-, hydro-, and gas-dynamic problems. Also, such software module as BladeGen is applied to design a solid-state model and TurboGrid is to create a grid. ANSYS CFX software uses the following basic equations for the numerical solution of the gas expansion problem in a turbine: the energy equation, the momentum equation, and the continuity equation. For the first time a numerical determined model of the GUBT-25 turbine has been developed in the ANSYS CFX analytical software. Also, a preliminary verification of the model has been carried out based on the results of the industrial experiment conducted at the OJSC “Severstal” turbine. In addition, to demonstrate the capabilities of the model the article graphically presents such characteristics as distribution of temperature and velocity in the first stage of the turbine. The developed numerical model of the GUBT-25 turbine has series of restrictions that affect the simulation results. The results of comparing the data obtained during the simulation differ from the experimental data. In case the model is more complicated, it will be possible to simulate the real processes of GUBT-25 more accurately.

Numerical and Experimental Investigation of Three-Dimensional Flow in Combined Protective Canister Filters

This work deals with the numerical and experimental investigation of flow in the protective filters which combine fibrous pleats and the absorbent cartridge. The flow through the complete 3D geometry of all parts of the filters, including complex geometry of the pleats, is numerically modeled using high-quality computational grids. The sorbent filling, textile dividers as well as the material of filtration pleats are modeled as the porous media with the coefficients of the quadratic Forchheimer equation derived from the experiments in the laboratory located at the SIGMA Research and Development Institute. A comprehensive CFD analysis has been carried out using the ANSYS CFX package with the SST turbulence model, which combines advantages of both the high- and the low-Reynolds number turbulence models. The fully parametric description of the pleats enables the generation of high-quality structured computational grids for a wide range of pleat heights and widths and to use numerical shape optimization process. The numerical simulations show very good agreement of calculated and measured pressure drop for all variants of the complex geometry of the combined filter. To simulate a real application of the protective filter, the unsteady simulations which follow the human breathing pattern have been performed with the flow rate corresponding to the increased human activity.

Wind interference effect on a hexagonal-shaped high building with orifices

This research examined at how the wind load and pressure on a tall hexagonal structure varied as the apertures changed. Wind angles ranging from 0 to 90 degrees with a 30-degree gap were employed in various situations. The distance between the interference building and the model building was also gradually increased, at 50mm intervals, from 50mm to 200mm. The major building model was examined at a scale of 1:500. The validity of the ANSYS CFX package was also evaluated using a rigid model with dimensions of 100mm x 100mm and a height of 700mm. The k-ε -turbulence model was used in the study, which was carried out using Computational Fluid Dynamics (CFD) and the ANSYS CFX software package. To demonstrate the link between distinct scenarios, interference factors (IF) and contours were employed. Interfering buildings' impacts on the hexagonal-shaped building are explored. The pressure coefficient of the faces rises as the distance between the interference building and the model building grows. The impacts of apertures on the model building were also examined, with 5-20% openings given.

On the efficiency of using the Navier-Stokes approximation in thermogasdynamic calculation of low-thrust liquid-propellant rocket engines at low Reynolds numbers

A numerical method for thermogasdynamic calculation of low-thrust liquid rocket engines is presented. These engines are used as end organs of the system of space attitude control for nanosatellites and small spacecraft. The method is based on the use of the TERRA software package for thermodynamic calculation and the Ansys CFX software package for gas-dynamic calculation using the Navier-Stokes equations. The results of the thermogasdynamic calculation, as well as the flow pattern of the working fluid in the chamber, are presented. The results of validating the described method are also presented. Its capabilities and limitations are analyzed. The validation procedure is based on the comparison with the results of experimental data on the Reynolds number and the momentum thickness.

Numerical study of the human walking-induced fine particles resuspension

One of the main sources of pollution in indoor environments is human walking-induced particle resuspension. In this work, the airflow and resuspension of particles smaller than 1 μm generated by foot tapping were investigated numerically using ANSYS CFX software. The k-ω shear stress transport model was considered to simulate the unsteady airflow field around and under the shoe. The immersed solid method was then used to incorporate the shoe in a three-dimensional computational domain. Particle resuspension was predicted by means of the Rock ‘n’ Roll model. The effects of the walking speed and shoe groove pattern (transverse grooves, longitudinal grooves and no groove) were studied. Three different selected particle-substrate combinations (ATD-linoleum, PSL-linoleum and alumina-steel) were tested. The numerical simulations showed that the air below the foot was ejected as a high velocity jet. After the shoe hit the ground, counterrotating vortices were formed around the shoe. The results of particle resuspension were compared with previous experimental works, and good agreement was found. Results shown that for the different studied cases the resuspension fraction ranges over four orders of magnitude, from 10−5 to 10−1. Particle resuspension fractions increased with particle size and walking speed. However, no significant influence of the shoe groove patterns was observed.

Computational Prediction of the Performance Map of a Transonic Axial Flow Compressor

Aviation fuel efficiency is an important target for aviation industry. Aircraft engine compression ratio is a key factor to improve fuel consumption. Compression ratio can be increased using transonic compressor. In this study, performance prediction of a transonic axial compressor at design and off-design operating conditions is investigated numerically using ANSYS-CFX software. The compressor is NASA Rotor 37. Firstly, the performance at design point is predicted, where mesh independence study is performed to determine suitable mesh size. Three-dimensional flow details for meridional plane, blade-to-blade plane and airfoil surface are explored. The design point study successfully captured flow features such as shock waves and flow separation regions. When compared with experimental data, the predicted compressor pressure ratio deviation error is less than 5%. 3D flow details show that shock wave strength increases from hub to tip. The shock wave moves backward as we move from hub to tip indicating that the flow separation covers lesser portion of the blade. Secondly, off-design performance is predicted for various rotational speeds. A simple procedure is utilized to predict surge and choke limits. The predicted compressor map is compared with experimental data and it shows overall root mean square error less than 5%. The success of the method developed in this research make it a viable method to be used in the design phase of transonic compressors to evaluate the effect of design modifications for both design and off-design operating conditions.

Unsteady flow simulations in two-stage turbines of a rocket turbopump to estimate blade structural soundness for fatigue

Abstract This study first aims at detailed investigations of three-dimensional unsteady flow field in the reference and optimized rocket turbine stages by performing time-accurate flow simulations based on Transient Blade Row (TBR) method or Time Transformation (TT) method in a commercial software ANSYS CFX. Although TT method is believed to enable relatively low-cost unsteady flow simulation, detailed comparisons between TT method-based and conventional unsteady flow simulations are made before TT method application to Fluid-Structural Interaction (FSI) problem. This study then makes an attempt to conduct structural analyses of the 1st and 2nd stage turbine blades under the influence of unsteady fluid forces caused by rotor-stator interaction predicted by TT method-based flow simulations. The structural analyses are executed by use of MSC Nastran. In this study, two materials are adopted as blade material. After the Fourier-series decomposition of the calculated unsteady pressure distributions, the unsteady pressure information is mapped onto the FEM (Finite Element Method)-modeled turbine blade surface as exciting aerodynamic loading. The frequency response analyses are then performed to calculate alternating stresses of the blade, from which the maximum magnitudes of alternating stress are obtained so as to discuss the rotor blade fatigue life.

Influence of Gas Content on Performance Effect on Shunt Vane Type Aviation Fuel Pump

In order to study the flow law of shunt vane type aviation fuel pump under the condition of gas-liquid mixture transportation, based on the RNG K-ε turbulence model and the Euler-Euler non-uniformity model, using the ANSYS CFX software to calculate an aviation fuel pump under different gas content conditions, and analyzing the flow of the fuel pump and the pressure law of the blade pressure. The research shows that the gas phase is mainly distributed in the front section of the long blade suction surface and the back section of the short blade pressure surface. The increased gas content will result in increased liquid velocity in the pump, which makes the gas phase gradually develop towards the suction surface of long and short blades and diffuse to the impeller flow path. The gas content mainly affects the pressure surface load of the fuel pump blades. The pressure load curve fluctuates at the relative position of the short blade (0.5-0.6) and long blade (0.3-0.6) as well as at the end of the blade and decreases with the increase in gas content. The change of pressure fluctuation of the blade is mainly reflected at the junction of long and short blades, and the pressure fluctuation amplitude of the front section of the short blade and middle section of the long blade fluctuates greatly. With the increase in gas content, the pressure fluctuation amplitude at each monitoring point reduces. The research results can provide some reference for the design of aviation fuel pumps.

Influence of Geometrical Parameters on the Shape of the Cycloidal Function Curve of a Fan with a Cycloidal Rotor

Even though the cycloidal rotor concept has been around for almost a century, it is still not as popular as it should be. Most often it is used to propel unmanned aerial vehicles or sea-going ships, or it is applied as a river- or sea-energy converter. Despite the possibility of directing the flow by changing the inclination angle of blades and the possibility of working in both directions, there are no scientific studies on the use of the concept in HVAC (heat, ventilation and air conditioning). One of the most important elements characterizing the operation of the cycloidal rotor is the cycloidal function describing the change in the angles of the blades during rotation. To properly design a cycloidal rotor for a preferred application, an analysis of the rotor geometrical parameters must be performed and analyzed. This was performed on a four-blade rotor equipped with CLARK Y blades. Using Ansys CFX software, a CFD model of a fan operating with various cycloidal functions was created. The results were compared with the experimental data with the use of the LDA technique. Different velocity profiles were obtained despite the use of cycloidal functions with similar waveforms and small angular differences. This is due to the considerable sensitivity of the cycloidal regulation system to differences in the geometrical sizes that describe it.

Investigation of the hydrodynamic characteristics of an axial flow pump system under special utilization conditions

In actual operation, axial flow pump stations are often used for various special purposes to meet changing needs. However, because the hydrodynamic characteristics of axial flow pump systems are still unclear when used for special purposes, there are many risks when pump systems are used for special purposes. To explore the hydrodynamic characteristics of an axial flow pump system under special utilization conditions, a high-precision full-feature test bench for an axial flow pump system is established in this paper. For the first time, an energy characteristics experiment and a pressure fluctuation measurement for a pump are carried out for a large axial flow pump system model under zero head, reverse pump and reverse power generation conditions. Then, ANSYS CFX software is used to solve the continuous equation and Reynolds average Navier–Stokes equation, combined with the SST k–ω turbulence model, and the characteristic curve and internal flow field of the pump system under special conditions are obtained. Finally, the numerical simulation results are compared with the experimental results. The results show that the velocity gradient distribution in the pump is uniform under the near zero head condition (NZHC), and there is no obvious flow collision and reflux phenomenon in the pump. Compared with the designed condition (DC), the peak-to-peak value (PPV) of pressure pulsation at the inlet of the impeller decreased by 67.16%, and the PPV at the outlet of the impeller decreased by 8.14% at H = 0 m. The maximum value of the main frequency amplitude (MFA) in the impeller area appears at the impeller inlet. Under reverse pump conditions (RPC), the phenomenon of unstable flow in the pump system is obvious, and a large range of recirculation zones appears in the nonworking face of the blade. Compared with the DC, the PPV of the impeller inlet at the optimal point of RPC increased by 122.61%, and the impeller outlet PPV increased by 11.37%. The maximum value of MFA in the impeller area appears at the impeller inlet. Under the reverse power generation condition (RPGC), no obvious flow separation was found in the nonworking face of the impeller. Compared to the DC, the PPV of the impeller inlet at the optimal point of the RPGC increased by 65.34%, and the PPV of the impeller outlet increased by 206.40%.

Behaviour of a Non-Newtonian Fluid in a Helical Tube Under the Influence of Thermal Buoyancy

Abstract This work is an evaluative study of heat transfer in the helical-type heat exchanger. The fluid used is non-Newtonian in nature and is defined by Oswald’s model. The work was performed numerically by solving each of the Navier–Stokes equations and the energy equation using the package ANSYS-CFX. Following are the aspects that have been dealt with in this paper: the effects of thermal buoyancy, fluid nature and the tube shape on the heat transfer, and the fluid comportment. The interpretation of the obtained results was done by analyzing the isotherms and the streamlines. The mean values of the Nusselt number were also obtained in terms of the studied parameters. The results of this research enabled us to arrive at the following conclusion: the intensity of thermal buoyancy and the nature of the fluid affect the heat transfer distribution but keep the overall rate of heat transfer the same.

A Flow Model for Side Chambers of Centrifugal Pumps Considering Radial Wall Shear Stress

The side chamber flow has a fundamental influence on the performance and reliability of centrifugal pumps. However, the radial wall shear stress in the flow modeling of pump side chambers is arbitrarily neglected. The current work proposes a model for the radial wall shear stress, which is an extension of the previous paper (DOI: 10.1115/1.4047532). By using the power-law for the velocity boundary layer and the Blasius law for the wall shear stress, introducing the Ekman layer thickness expression, and deducing the Bödewadt layer thickness expression, the radial wall shear stress on the rotating and stationary disks is formulated and then integrated into the side chamber flow model. Besides, the entire flow field of the centrifugal pump is solved using the computational fluid dynamics (CFD) software ANSYS CFX. The radial wall shear stress calculated by the new side chamber flow model (NSCFM) is in the identical magnitude as CFD. Compared with pressure measurements, NSCFM makes better pressure predictions than CFD from the rear seal to the hub; however, in other areas, CFD results are closer to experimental data than NSCFM results. The flow prediction tools show that the volumetric efficiency and the shroud thrust increase with the increase in flow rate. NSCFM achieves a good compromise between calculation speed and desired accuracy.