CFD Simulation Results Research Articles

Liquid hydrogen refuelling at HRS: Description of sLH2 concept, modelling approach and results of numerical simulations

The paper considers the concept of efficient liquid hydrogen (LH2) refuelling at hydrogen refuelling stations (HRS), presents modelling approach and 3D transient CFD simulation results. The concept is based on the advantages of transforming hydrogen from equilibrium to a non-equilibrium sub-cooled state (sLH2) during compression at pump. The modelling approach comprises a thermodynamic model of LH2 transfer from the HRS tank to the pump exit and a two-phase CFD model from the pump exit through the HRS equipment, i.e. pipes with bends, automatic valve, breakaway, nozzle, and manifold to onboard storage tanks. Due to the absence of published experimental data, the modelling approach and simulations are verified against conceptual LH2 refuelling process available in the literature. The CFD model reproduces key LH2 refuelling parameters: flow rate, pressure, temperature dynamics, including non-uniform temperature in onboard tanks and predicts pipe cooldown from 88K to allowable temperatures corridor of 23.9–26.5 K.

Analysis of the Sustainable Cooperation between a Multi-Piped Impeller and a Concentric Casing Using Experimental Planning

Centrifugal pumps are one of the most commonly used devices in all branches of industry. Their application area is very broad and practically related to all sectors of the economy. Such pumps are widely applied in the chemicals industry, liquid gas technology, and machine lubrication systems, among others. On the basis of available data, it can be assumed that pumps consume approximately 27% of the world’s electricity. For this reason, their efficiency has a significant impact on the energy consumption of many technological processes. This article presents a summary of the research concerning the cooperation between a multi-piped impeller and a concentric casing. A multi-piped impeller is a completely new concept of a centrifugal impeller, which is characterized by the fact that the energy of the liquid is transferred as a result of the flow of media through the internal flow channels, and also the flow of media around it. The type and design of the casing, with regard to the flow in it and around the impeller’s pipes, plays an extremely important role. Numerical analysis was used as the main research method, which was based on a rotatable experimental plan. The CFD simulation results were validated on a test stand. Finally, the mathematical model and the rules for selecting the geometric features of such a stator were proposed in order to achieve the highest possible efficiency when cooperating with the multi-piped impeller, which constitutes a scientific novelty.

Performance prediction and optimization of lateral exhaust hood based on back propagation neural network and genetic algorithm

The lateral exhaust hood (LEH) is commonly used to capture contaminated airflow in industrial plants. Its performance is influenced by numerous factors and exhibits a strong nonlinear relationship, optimizing this performance demands significant computational time and cost. This study proposes an LEH optimization design method that combines a backpropagation neural network (BPNN) with a genetic algorithm (GA), verified through experiments and numerical simulations. A BPNN prediction model is established based on 520 CFD simulation results. This study discusses seven factors influencing LEH performance, including the buoyant jet's velocity and temperature, the LEH's geometry and position, and the exhaust velocity. The results indicate that within the parameter range of the prediction model, there is a critical aspect ratio value that significantly affects LEH capture efficiency. The horizontal distance between the LEH and the pollution source significantly affects capture efficiency, especially when the LEH's installation height is low (H/D < 0.5). In addition, when combined with GA for fast searching, the expected combination of LEH design parameters can be obtained. This study aims to enhance the design efficiency of industrial exhaust hoods and improve worker health protection.

Applications of augmented reality (AR) in chemical engineering education: Virtual laboratory work demonstration to digital twin development

With advances in information technologies, virtual technologies have become a viable option for chemical engineering educators. Although traditional teaching methods remain effective, they have many limitations when presenting complex phenomena. Virtual technologies like Augmented Reality (AR) have shown great potential as an addition to traditional teaching methods. This study explored the practicality and potential applications of AR technologies in chemical engineering education. In this work, traditional 2D representations of CFD simulation results were replaced by AR experiences to visualise the flow pattern and assist the understanding of the working mechanism behind different devices. Other than CFD result integration, animations were also included in AR experiences for personalised training and inclusive laboratory work experience. AR-assisted training has shown good potential in reducing financial loss and equipment downtime due to improper handling. Besides delivering teaching content, the development process of a digital twin with an AR interface was used to demonstrate how virtual technologies can be involved in digitalisation in Industry 4.0. Beyond the technical contents, important design philosophies were also taught as part of the courses.

Investigation on hydraulic characteristics of a model and prototype bulb turbine based on similarity criteria

Abstract From the perspective of the world hydropower utilization trend, the medium and high head hydraulic resources are gradually decreasing, and along with much more attention to the ecological environment and land resource constraints, low-head hydropower plants have been becoming particularly prevalent. Benefit from compact structure, less investment, high capacity and wide operation range, bulb tubular turbines have come up to be the optimal option for the development and exploitation of low-head energy resources and been widely applied. In this paper, based on measurement data and CFD simulation results of model and prototype, scale effect which derived from similarity law was picked up to investigate the hydraulic performance and operating properties. Through comparison and analysis, it’s concluded that distinct from high-head application similarity conversion turns out to be more complicated for bulb turbines in case of flow characteristics, and it’s recommended that this conversion be further modified considering different boundary conditions. Such achievements will be of great help to look into the mechanism of ratio effect and accelerate research progress.

Heat dissipation analysis and multi-objective optimization of Raspberry Pi CPU by natural convection

With the high-speed and high-frequency operation of CPU chips, as well as miniaturization and dense assembly of integrated circuits, the heat generated by the Raspberry Pi CPU is constantly increasing. To address the urgent need for efficient Raspberry Pi CPU heat dissipation and ensure normal operation within a safe temperature range, this study first established a model to simulate the CPU's thermal physics parameters during operation using CFD simulation software. An experimental platform was then set up to validate the CFD simulation results. Based on the validated CFD model, initial heat dissipation design was carried out. On this basis, the heat dissipation system was optimized by altering the heat sink’s length, width, fin height, thickness, spacing, and the thermal grease’s thermal conductivity between the heat sink and CPU chip. A surrogate model was established using the response surface methodology, and the NSGA-II genetic algorithm was employed for multi-objective optimization of the heat dissipation system’s cooling performance. Compared to the initial solution, the chip temperature was reduced by 6.19 °C, but the heat sink mass was increased by 0.65 g. By conducting multi-objective optimization design and making reasonable choices for the parameters, a suitable and an optimum design, in terms of both economics and efficiency, is obtained. These results demonstrate that this research can provide theoretical guidance and technical support for practical production. Furthermore, the methods and findings from this study can be applied to the design of heat dissipation systems for similar applications.

Optimization of automotive aerodynamic performance based on DOE

Based on a new-energy sedan as the research object, the Design of Experiments (DOE) optimization integrated grid deformation method was used to optimize and improve the aerodynamic performance of a certain development model. A three-dimensional flow field comparison analysis was conducted on the improved areas of the whole vehicle flow field, and wind tunnel tests were conducted for verification. Through CFD simulation and wind tunnel test verification, the accuracy of the CFD simulation method was verified. The engineering feasible DOE optimization recommended area for the whole vehicle was summarized. The optimal prediction results based on the DOE optimization method and the corresponding CFD simulation results were analyzed for reliability. The correlation between the optimization variables and the target function was analyzed, and 6 counts reduced the whole vehicle drag coefficient by adjusting the optimization variables within a small range. Finally, wind tunnel tests were used to verify the effectiveness of the optimized variable scheme. The results provide an important reference for the optimization design and development of vehicle aerodynamic performance.

Numerical Calculation of 1P Aerodynamic Loads on Aviation Propellers

To accurately predict the 1P aerodynamic loads of aviation propellers, this paper established a mathematical model of aviation propeller 1P aerodynamic loads based on the coupling method of blade element theory and momentum theory. Correction methods such as the Prandtl tip correction method and the propeller root correction method were implemented to further improve calculation accuracy. A 1P aerodynamic load calculation procedure was developed based on the mathematical model by using the Matlab software. 1P aerodynamic loads of a three-blade propeller were predicted for three different angles including 3 °, 9 °, and 12°. The numerical calculation results show that the calculated aerodynamic characteristic parameters of individual propeller blades obtained based on the propeller 1P aerodynamic load mathematical model deviate less than 6% from the CFD simulation results, and regular periodic pulsations are observed. The numerical calculations in this paper show that the propeller 1P aerodynamic load calculation procedure developed based on this model can accurately predict the propeller 1P aerodynamic load, which can provide some reference for the study of aviation propeller aerodynamic characteristics.

Turbulence-assisted shear controllable synthesis of silicon oxide micro/nano particles using a counter axial-swirling impinging jet flow reactor

It has been recognised that turbulence shear can be used to effectively control and affect the synthesis of micro/nano particles. The present study focuses on turbulence-assisted shear controllable synthesis of silica (SiO2) micro/nano particles and investigates such shear controllable synthesis process using a counter axial-swirling impinging jet flow vortex flow reactor. Two counter swirling flow streams impinge in the reaction chamber to significantly intensify the local turbulence shear with the aid of ultrasound irradiation. The consequence of the turbulent shear leads to either the trapping of nano-particle nucleus into the turbulent eddies to form the aggregated micro/nana particles or the confinement of the growth of agglomerated micro/nano particles so as to form highly uniform and better morphological micro/nano particles. The experimental results have affirmed the postulation that the local turbulent shear generated by the turbulent eddies with the length scales down to the Kolmogorov length scale may directly interact with the aggregated SiO2 micro/nano particles, influencing the particle spherical morphology and size distribution. In addition, it has been found that synthesis performance can be further improved by intensifying the local turbulent shear through the ultrasound irradiation in the synthesis process. Both CFD simulation and experimental results clearly indicate the existence of the correlation in the synthesized SiO2 micro/nano particle characteristics with the local turbulence shear and mass transfer occurring in counter swirl impinge jet flow.

Experimental and numerical study of thermal and electrical potential of BIPV/T collector in the form of air-cooled photovoltaic roof tile

Among renewable energy sources, Building-Integrated Photovoltaic/Thermal (BIPV/T) systems are gaining increasing interest. To improve their economic competitiveness, technologies that increase their efficiency are searched for. The paper is devoted to evaluating the impact of various air-cooling configurations on the thermal and electrical performance of a photovoltaic roof tile. A numerical model of the own experimental system was developed in the ANSYS Fluent software for a wide range of input variables. The original approach based on the SST k-ω turbulence model, Discrete Ordinates radiation model, and the use of Solar Load module were proposed. Such a numerical model allows representation of semi-transparent layers and variable solar irradiance, which is a unique realization of real system modelling. Numerous analyses conducted indicate a higher heat recovery potential for an airflow duct with a height of 25 mm for all configurations analysed. The highest value of recovered heat flux was approximately 330 W/m2 under conditions of a volumetric air flow rate of 7.5 m3/h and solar irradiance equal to 900 W/m2. Good agreement of the results of the multivariant CFD simulations with new experimental ones was confirmed. Insight into the flow phenomena behind the achieved thermal results supplemented the knowledge. The highest electrical efficiency obtained experimentally was 5.76 % for a channel with a height of 50 mm, volumetric flow rate equal to 7.5 m3/h and solar irradiance equal to 600 W/m2. The presented methodology and the results obtained can be useful in research devoted to optimising BIPV/T air-based cooling systems, which will then be tested in-situ. Moreover, new experimental data collection can be used for the verification of numerical models.

Research on the Calculation Method of Propeller 1P Loads Based on the Blade Element Momentum Theory

Aircraft propellers produce relatively large in-plane loads, called propeller 1P loads, during maneuvers such as turning, diving, and lifting, and these loads can negatively affect the flight and control of the aircraft. In order to study the change rule of 1P aerodynamic loads, in this paper, a mathematical model of the propeller 1P aerodynamic loads has been developed based on the blade element momentum theory. This mathematical model was then corrected using the Pitt–Peters incoming flow correction method, the Prandtl tip correction method, and the propeller root flow correction method. Based on this mathematical model, a calculation procedure for the propeller 1P aerodynamic loads was developed using MATLAB software, and the accuracy of the procedure was verified by comparing the results with CFD simulation results. Numerical simulations show that the results calculated based on the proposed mathematical model for the coefficients of thrust, power, bending moment, and the tangential force of the propeller have an error of less than ±6.00% compared to the CFD simulation results. For a small inflow angle, the coefficients of bending moment and tangential force of the whole propeller fluctuate in a small range. But, as the inflow angle increases, the fluctuation range of the aerodynamic characteristic parameters of the propeller increases and the fluctuation becomes more complicated. Through numerical calculations, it has been shown that the mathematical model presented herein is reliable and accurate. In addition, it greatly shortens the calculation time and improves the calculation efficiency. It is expected that the proposed model can provide a certain help for the strength design of the propeller structure and the study of the aerodynamic performance of the whole aircraft.

Experimental and numerical study on the high-speed gas-solid nozzle erosion of choke manifold material in high pressure and high production gas well

High pressure difference, high flow rate, and high sand content in throttling manifolds of high-pressure and high-production gas wells make the problems of high-speed gas-solid erosion wear especially prominent. The failure of the throttling manifold is frequent, which is easy to induce overflow, kick, and blowout accidents, aggravates well-controlled risks, and brings safety risks. Therefore, according to ASTM G76–2013, this paper adopts the gas-solid nozzle erosion test method and air jet erosion test rig. The high speed (107 m/s-49 m/s) gas-solid nozzle erosion test of 30CrMo alloy steel was carried out under different inlet pressures (0.06 MPa–0.15 MPa) and impact Angle (15°-90°), and the erosion rate of 30CrMo alloy steel under different experimental conditions was obtained. The erosion rate equation of 30CrMo alloy steel suitable for high-speed solid particle impact is established. Based on the results of erosion experiments, the optimal particle motion model for high-speed compressible flow is constructed. Combined with the discrete phase model (DPM) and gas-solid two-phase coupling calculation method, a three-dimensional CFD erosion model of the “reduced-tuber-nozzle-erosion cavity” was established. The erosion simulation of the gas-solid nozzle of 30CrMo alloy steel, a throttling manifold material, was carried out at different impact angles (15°-90°) and inlet pressure (0.06 MPa–0.15 MPa), and the distribution characteristics of the flow field, particle movement trajectory, impact velocity distribution, and slip characteristics were revealed. The accuracy and reliability of the CFD erosion model and simulation results have been validated by test data.

Experimental research and numerical study of leakage influence on the internal two-phase flow of subsea jumper

The influences of jumper leakage on the M-type jumper's internal two-phase flow are investigated. The CFD simulation results are validated against the experimental data, demonstrating a high level of agreement. The effects of leak dimensions, different leak locations, gas-liquid ratio, and mixing speed are discussed in terms of the gas-liquid phase distribution, pressure gradient, and jumper vibrations. It is found that the flow patterns can be useful indicators for jumper leak detection, especially when the leak dimension is larger, the slug flow may be formed, producing more serious damage to the jumper. The flow pattern varies significantly with different leak locations. In addition, the flow pattern is affected by the volume percentage of water and faster mixing speeds. The pressure variations can be useful indicators. It is larger as the leak dimension increases and varies significantly in front of the leak location of the jumper. The vibrations can be useful indicators. The larger the leak dimension is, the more pronounced the vibration response is. If vibration sensors are used for leak detection, the downstream vibration signals of the jumper can be a key indicator. Faster mixing rates and water content will cause the jumper to vibrate more intensely.

A mathematical model for accurately predicting face mask wearer’s inhalation exposure to self-exhaled and external pollutants

Face masks reduce the wearers’ inhalation exposure to external pollutants, but intensifying the exposure to their self-exhaled pollutants. To quantify the wearers’ inhalation exposure to the two sources of pollutants, a mathematical model for transient-state conditions was firstly established and scientifically validated, with an average relative deviation of only 3 % from the experimental data and only 6 % from the validated CFD simulated results. Proportion of leakage flow rate via gap (γ) was mainly affected by breathing flow rate (Lexh/inh) and gap’s area (Sg), followed by face mask’s surface area (Sm) and thickness (Mm). The 7 L/min of Lexh/inh led to the maximum inhalation fraction (IF) of self-exhaled pollutants at about 54 %, implying that wearing face masks poses a threat to the wearer’s health. When face mask’s volume increased from 50 mL to 150 mL, the relative intake dose (ID∗) of external pollutants decreased by 0.12 but the IF of self-exhaled pollutants increased by 9 %. When face mask’s filtration efficiency increased from 10 % to 90 %, the IF of self-exhaled pollutants and the ID∗¯ of external pollutants decreased by 13 % and 0.23, respectively. The increase of 0.80 in γ decreased the IF of self-exhaled pollutants by 8 % but increased ID∗¯ of external pollutants by 0.19, implying that protective performance always contradicts on the inhalation exposure to self-exhaled pollutants. The model established provides a new method to evaluate the performance of face masks rapidly and accurately, and further benefits the improvement of face masks and even other respiratory protective equipment.

Equivalent diffusion ratio distribution in the UGT15000 low pressure compressor

With spatial and temporal periodicity approach the results of steady state CFD simulation of compressible air flow in each blade-to-blade row of low pressure compressor (LPC) of the UGT15000 gas turbine engine (Ukrainian SSR constr. and prod.) are presented. Near the nominal rotation speed compressor map and adiabatic efficiency of each stage and the flow angles at leading and trailing blade edges are predicted and calculated. At the average radius stage flow and stage load coefficients are determined. It has been established that the reason of the low efficiency of the last stage is associated with the low stage reaction (≈0.5) leading to high airflow swirling at outlet. For LPC optimization a calculation of the radial distributions of the equivalent diffuser coefficient was performed. It is shown that the greatest total pressure losses are in the stator rows of stages 9, 8, 5 and in the rotor rows of stage 9. High losses are also shown on the upper half of the 4th, 3rd, 2nd stator blades and the lower half of the 1st rotor blades. The identified potential for increasing the efficiency of the LPC is up to 2% without significant construction changes.

Flow field characteristics and energy loss model of the effective upstream flow region of orifice in liquid jet

Orifice jets commonly adhere to the thick-walled orifice jet mechanism or the thin-walled one, where the difference between the two orifice jet mechanisms is generally considered to be caused after the fluid enters the orifice. However, ignoring the energy loss before entering the orifice could be inaccurate and even misleading. Therefore, we studied the flow behavior in the upstream flow region of thick-walled orifices (small orifices) and thin-walled ones (large ones). Firstly, the concept of the effective upstream flow region of orifice was proposed based on the film theory. It can be simplified into an approximate hemispherical multi-channel parallel contractive flow field. Then, the experiments of the effective upstream flow region were conducted by the streamlined contractive orifices with equivalent energy loss. The proportion of the energy loss before the fluid enters the orifice to the total energy loss was obtained. In addition, the maximum impact range of the effective upstream flow region was remarked by theoretical derivation, and local resistance coefficient functions were established based on the CFD simulation results. Finally, a semi-theoretical model of energy loss in this region was developed. It can quantitatively measure the proportion of increased energy consumption caused by the sucked air inside orifice, well verifying the eddy energy consumption, which provides a scientific exclusion method for predicting the complex form resistance.

Cooling Tower Plume and Drift Concentration in presence of Urban Canyon

This paper presents a computational analysis of the cooling tower plume and drift emitted by mechanical draught cooling towers situated in urban areas. The data from the Wang X (2019) and Briggs plume lift height formula are used to prove results obtained from computational Modeling of cooling tower drift and it was found to be effective. The simulation setup uses a multiphase mixture model for plume analysis and DPM for analysis of drift in the Ansys fluent. The CFD simulation results are accurate within 50 to 100 m with the Briggs plume lift height formula. The effect of wind coming from urban canyons on the cooling tower results in decreased plume lift height and increase drift concentration and deposition rate on the ground.

Hydrodynamic Simulation of Green Hydrogen Catamaran Operating in Lisbon, Portugal

Similar to other industries, the maritime industry is also facing increasing restrictions on ships regarding pollution control. The research presented in this paper is aimed at studying the pros and cons of alternative fuels followed by a detailed analysis on hydrogen fuel cells (PEMFC) for a particular ship operating in Lisbon, Portugal. Dynamic forces acting on the ship have been studied for a year. Assessing various scenarios based on these results aids ship operators in making informed decisions regarding the future course of action for their existing vessels. These different cases are first: business as usual (diesel engine), second: replacing the diesel engine with a hydrogen hybrid system and, third: replacement of the ship with a new hydrogen hybrid ship. The study is based on the simulation of numerical equations and CFD simulation results. As the result, the second scenario is best suited in both aspects; namely, environmental and economic.

CFD analyses of large-scale tests highlighting the effects of thermal radiation in steam-containing atmospheres

In simulations of heat transfer in large gaseous volumes under moderate temperatures, thermal radiation is traditionally neglected to simplify the computations. In recent years however, some small as well as large-scale experiments have demonstrated that thermal radiation may have a strong effect on the temperature field if the atmosphere contains an infrared absorbing gas such as vapor, even in small concentrations. This has in particular been shown in the H2P2 series of tests performed in the large-scale PANDA facility at the Paul Scherrer Institute. For these tests an air-helium-steam mixture was compressed with a helium injection, which caused the formation of a hot bubble. The initial vapor volume fraction varied between 0.1 % and 60%. In this paper, we report the results of CFD simulations conducted for the five H2P2 tests. The turbulence model k-ω SST was used, while thermal radiation was considered using the simple P1 model as a default, in conjunction with the Weighted Sum of Gray Gases Model (WSGGM) to specify steam absorptivity. For comparison purposes we also made use of the more advanced Monte-Carlo model for selected experiments. CFD Best Practice Guidelines were employed, in particular through preliminary grid and time-step sensitivity studies.The temperature and helium concentration fields matched the experimental data quite accurately, except for the test with very low vapor content (H2P2_1_2, 0.1% vol. steam), where the temperature was somewhat over-estimated. This may be due to the inadequacy of the radiation models at these extreme conditions. Two major conclusions can be drawn from this study: 1) ignoring thermal radiation can lead to large over-predictions of temperature, even when the steam content is low (order of 1%) and 2) the simple P1 model provides sufficient accuracy. Use of the more sophisticated Monte-Carlo model yielded similar and slightly more accurate results, albeit at a considerably larger CPU expenditure (5–7 times).

CFD Simulation on the Effect of Adding Dimple Balls Stagger Position on Base Plate on the Performance of V-Corrugated Air Heating Solar Collector

The ever-increasing increase in energy consumption requires great attention. Therefore, efforts need to be made to find new energy sources, such as solar energy. The absorber plate absorbs solar energy in the form of radiation, and heat is transferred by convection to the working fluid through the solar collector. Increasing the thermal efficiency of the solar air collector by modifying the absorption area using a v-corrugated absorber and also increasing the convection heat transfer coefficient by creating turbulence in the heat transfer area. Flow turbulence can be achieved by providing a disturbance in the form of a dimple in the working fluid channel above the base plate. This research was conducted utilizing numerical simulations and experiments. CFD simulation aims to obtain the most optimum ratio of ΔT/ΔP values of diameter and dimple distance using ANSYS Fluent software with a diameter variation of 6mm, 8mm, 10mm, and 45mm spacing; 50mm, and 5mm. Based on the results of CFD simulations that have been carried out on each variation of the distance and diameter of the dimple, it can be concluded that the closer the distance between the dimples, the smaller the resulting pressure drop, and the larger the diameter of the dimple, the greater the resulting temperature value. The use of a larger dimple diameter results in an increase in the heat transfer area and further increases the outlet temperature. The expected ratio is the value of the largest temperature increase and the smallest pressure drop. In the calculation of the total ratio, the dimple diameter of 10 mm with a distance of 45 mm has the highest ΔT/ΔP ratio value.