Inlet Section Research Articles

OPTIMIZATION OF DESIGN OF THE FISH-SPAWNING PASS OF THE BAGAEVSKY HYDROELECTRIC COMPLEX USING NUMERICAL 2D MODELING

Numerical hydrodynamic modeling of the flow of water and sediment through the fish-spawning pass of the Bagaevsky hydroelectric complex on the river Don is considered. The calculations use two-dimensional shallow water and sediment transport equations by the STREAM 2D CUDA software complex. Recommendations are made to change the longitudinal profile of the bottom and the configuration of the inlet section, as well as to increase the coefficient of roughness of the bottom and sides of the channel to ensure fish protection requirements.

Numerical study on the flow and heat transfer performance of SCO2/molten salt in Z-type printed circuit heat exchangers

The utilization of a PCHE in conjunction with a SCO2 Brayton cycle and molten salt thermal storage demonstrates a high efficiency. Investigating the flow and heat transfer characteristics of SCO2 and molten salt within a Z-type PCHE is essential. However, this particular aspect has not been explored by previous researches. This study employs a Z-type PCHE to analyze the heat transfer and flow characteristics of SCO2 and molten salt under different inlet temperatures, mass fluxes, and outlet pressures. Furthermore, the heat transfer efficiency of a Z-type PCHE is evaluated and compared to that of a conventional straight-type PCHE. The results indicate that the flow pattern of SCO2 exhibits periodic behavior due to the periodic bending structure of Z-type PCHE, while the flow of molten salt is minimally affected. Furthermore, different SCO2 conditions lead to divergent patterns in flow and heat transfer efficiency compared to molten salt. Z-type channels help alleviate the decline in heat transfer that typically happens in the inlet section of straight channels. Nu for a dual working fluid in a straight-type PCHE is only 1.1 times greater than that of a single working fluid. In Z-type PCHE configuration, the ratio of the dual working fluid to the single working fluid Nu is 1.4. The sensitivity of SCO2/molten salt dual working fluid to the heat exchanger structure is significant, with Z-type PCHE demonstrating superior heat transfer capabilities. The results outlined in this study offer the prospect of improving the design and deployment of Z-type PCHE in molten salt energy storage systems that operate within SCO2 Brayton cycle.

Study on Influence of Core Structure on Catalytic Converter Performance Using CFD

In recent years, as the automotive industry is growing, one of the major hope for future vehicles is to meet emissions regulations. Automobiles pollute the air, and clean-air laws have made Catalytic Converters a legal requirement because they convert harmful pollutants from an engine's exhaust into cleaner emissions. The device works with the principle of a catalyst, something that causes or speeds up a chemical reaction without itself being changed. But the presence of a catalytic converter increases the exhaust back pressure which has an indirect effect on the engine efficiency ie engine efficiency decreases, thus increasing fuel consumption. The performance of a catalytic converter is substantially affected by the flow distribution inside the substrate, a uniform flow distribution can increase its efficiency, lower the pressure drop and optimize engine performance. The flow distribution in a catalytic converter assembly 15 is governed by the geometry configurations of the inlet and outlet cone section, the substrate, and exhaust gas compositions, and therefore a better design of the catalytic converter is very important. This Project deals with the fundamental understanding and study of complex processes taking place involving fluid flow, pressure, and velocity profiles in the catalytic converter using ANSYS WORKBENCH 2022 R1. The main objective of our analysis is to determine the most effective and optimum design of a Catalytic Converter

Numerical study on surface corrosion deposition of fuel elements and its influence on flow heat transfer

Corrosion of pressurized water reactors (PWR) in nuclear power plants can lead to serious safety hazards. This study aims to analyze the deposition of corrosion products using FLUENT software. Deposition models and thermal resistance models were developed, and the effects of deposits on the reactor’s thermal–hydraulic characteristics were evaluated. Additionally, the impact of various parameters on deposition and thermal–hydraulic characteristics was examined. Results show that deposits accumulate extensively in the inlet section of the fuel cladding, while appearing as spot deposits in the outlet section. For deposit thicknesses below 30 μm, the surface temperature of the cladding gradually increases. However, when the thickness exceeds 30 μm, the surface temperature rapidly rises. Furthermore, the study reveals that the deposition amount decreases with increasing inlet flow velocity, exhibits an upward trend with higher inlet temperature, and increases with a higher wall heat flux density. This research provides important insights for understanding core deposition and thermal–hydraulic characteristics in nuclear reactor systems. It offers valuable guidance for enhancing safety and operational efficiency in nuclear power plants.

Numerical study and orthogonal analysis of optimal performance parameters for vertical cooling of sintered ore

The sinter cooler, essential for cooling hot sintered ore to a specific temperature, has seen recent advancements with the introduction of a vertical sinter cooling furnace. This innovation aims to enhance energy efficiency, reduce emissions, and improve waste heat recovery. Despite significant research, a quantitative analysis of factors impacting its cooling and heat transfer efficiency is lacking. This study utilizes the Euler model and local non-equilibrium thermodynamic theory to identify key factors affecting the gas–solid cooperative cooling process in the vertical cooler. Through an orthogonal experimental approach, the paper determines the optimal structural and operational parameters for the furnace. Key findings include that a gas–solid ratio of 1200m^3/t, inlet air temperature of 50 ℃, cooling section height of 6m, and diameter of 13.25m maximize efficiency, achieving a weighted range normalization value of 0.962. This configuration meets sintered ore cooling requirements while optimizing waste heat recovery. The study reveals that the impact on heat transfer efficiency is influenced primarily by the gas–solid ratio, followed by the cooling section's height, diameter, and inlet air temperature. These insights are crucial for enhancing the vertical sinter cooler's design, contributing to more energy-efficient and environmentally friendly sintering processes.

Parametric study of an empty diffuser geometric parameters and shape for a wind turbine using CFD analysis

This research examines the optimal 3D geometric parameters and shape of empty diffusers to enhance the mass flow rate of the HAWT rotor plane using a detailed parametric study. Previous works have investigated the use of diffusers to augment turbine power output; however, different curvature surfaces and the effects of all associated angles have not been considered for a thorough evaluation. This work mainly focuses on analyzing the effect of opening angles (2° to 22°), inlet shroud angles (8° to 24°), flange height ratios, flange angles (0° and 15°), and shape of the diffuser as well as flanges on velocity, pressure at the diffuser entry, and through the diffuser section at a wind speed of 4.5 m/s. At an inlet-shroud angle of 24° and an opening angle of 8°, with a diffuser flange height-throat diameter ratio of 0.3, the system achieved an 82.9% increase in flowrate. The diffuser with an inlet shroud-side lower stepped flange showed an optimum velocity of 9.12 m/s (maximum) and 8.2 m/s (average), resulting in a 102.66% and 82.2% increase in velocity, respectively. The percentage increase in velocity of the present study is 92.61%, compared with the previous maximum increase in rate of 53.8%, and then an increase in velocity of 38.81% was obtained. The optimum speed occurred at 0.175 m from the inlet section of the diffuser, indicating where the turbine should best be located. The CFD results from this work were validated with experimental data from the literature, showing a good agreement between the two. Integrated diffuser-turbine system simulation and experimental work with field tests are recommended as a way forward.

Hydrodynamics and mass transfer performance of microbubble flow in the bubble column with a contraction section

Bubble columns have many applications in the biochemical, petrochemical, and metallurgical industries. The gas-liquid system composed of microbubbles is characterized by significant phase interfacial area, high mass transfer efficiency, fast dissolution rate, strong adsorption capacity, and long self-sustaining time. This paper investigated the performance of pressurized dissolved gas microbubble generation (PDG) using a Venturi tube as the releaser using a plug-in online imaging instrument. The hydrodynamic and mass transfer characteristics of the microbubble flow generated by PDG in a bubbling column with a contraction section (BCS) were then investigated. One of the primary studies was the effect of the contraction section on the flow performance of the bubbles, the mass transfer performance, and the aeration efficiency of the PDG versus the throat inlet Venturi bubble generator (VBG). The results show that the initial bubble Sauter mean diameter is essentially constant with dissolved gas pressure, and the bubble size distribution(BSD) is similar. The bubble stream passing through the contraction section exhibits two different BSD at the center and side walls of the BCS outlet section. Microbubbles in the inlet section in the absence of external forces almost do not occur in bubble coalescence. The flow of bubbles in the contraction section is subject to a slight coalescence effect. The diameter of bubbles in the contraction section is mainly larger than 20 μm. In the contraction section, coalescence occurs mainly at the side wall. The way of occurrence is adsorption coalescence and collision coalescence. The bubbles move in a gradually confined space with a high degree of interference with each other's bubbles, and the liquid linear velocity acts as an ‘external force’ that benefits the flow of the bubbles out of the confined space. The standard aeration efficiency of PDG is 3–11 times higher than that of the VBG. At 0.3 MPa, the highest standard aeration efficiency for the PDG method was between 0.18 and 0.64 kgO2/kW∙h.

A Numerical Evaluation for a Newly Designed Closed Loop Subsonic Wind Tunnel

A wind tunnel is a piece of equipment specifically designed for studying the influence of air passing over solid matters in aerodynamic research. Computational Fluid Dynamics (CFD) was used to conduct methodical research into the design and modeling of flow characteristic in a closed-loop wind tunnel. The necessary intake fan velocity was established using an analytical velocity model, and the test section's inlet conditions were produced by applying the Reynolds number equation, assuming that the Reynolds number was 500,000. Instead than using the traditional method, a full-scale CFD model of the complete wind tunnel was taken into consideration. This made it possible to improve the flow quality over the entire circuit as well as only in the test area. The test section flow quality was more impacted by upstream flow circumstances than downstream conditions, according to analysis of the guide vane designs. Therefore, careful consideration has to be done while constructing the vanes at upstream curves, especially corners that are parallel to the test section. The simulation results showed that, in the case of a fully configured wind tunnel, flow uniformity in the test section is successfully attained.

Modeling of thermal radiation in a participating media with conjugate heat transfer

AbstractModeling a combination of thermal radiation and conjugate heat transfer in a three‐dimensional rectangular domain which has a participating media CO2 flowing through is done numerically in OpenFOAM. The rectangular duct has a vertical step (facing forward to the inlet) which is located at a distance from the inlet (the distance is same as the height of the inlet section). The domain is divided into two regions (namely solid and fluid). Carbon dioxide, a highly absorbing fluid with extinction, is used here as the participating medium. The ability of the code is verified to analyze the thermal radiation in a participating media with conjugate heat transfer. The study was carried out for a constant Reynolds number 250 and a contraction ratio of 0.5. The study focused primarily on the importance of adding thermal radiation on to thermal analysis and the reason behind the Nusselt number variation on different regions of solid–fluid interface. It also discussed the effect of radiative properties, such as optical thickness and linear scattering albedo, on the average convective Nusselt Number.

Unsteady Investigation of Intermediate Turbine Ducts Under the Influence of Purge Flows

Abstract The aerodynamic flow field at the outlet of a high-pressure turbine (HPT) stage in a modern turbofan engine is highly unsteady and strongly influenced by periodic fluctuations from the HPT rotor, also interacting with the HPT stationary vanes. Downstream of the last HPT stage, the flow enters the intermediate turbine duct (ITD), where new unsteady components are generated, due to the interaction between the incoming flow and the struts supporting the ITD. This paper illustrates the differences between the unsteady flow behavior in two state-of-the-art ITD configurations for turbofan engines: the turbine center frame and the turbine vane frame. The experimental results discussed in this work are obtained in the Transonic Test Turbine Facility, situated at Graz University of Technology, Austria. To achieve engine-representative operating conditions at the ITD inlet and outlet sections, the tested setups include not only the duct, but also the last HPT stage and the first low-pressure turbine stage row. Additionally, the test rig features a secondary air supply system, capable of feeding purge air to every stator–rotor cavity in the test vehicle. Unsteady measurement data at the inlet and outlet of the two duct configurations are acquired with fast-response aerodynamic pressure probes, for two purge flow conditions. Azimuthal mode decomposition is applied to phase-averaged data at selected radial positions, to isolate and quantify the contribution of different interaction modes to the overall unsteady flow field.

Numerical simulation of water-slag elbow erosion-inhibiting by regulating the slag injection position with a novel preceding rotating sheet structure

The elbow erosion seriously jeopardizes the safe and stable operation of water–slag discharge pipeline of the coal gasification system. This work simulated water–slag elbow characteristics with various slag injection positions by simulating five simplified and representative erosion categories, including A-type horizontal-vertical elbow with an upstream flow, B-type horizontal-vertical elbow with a downstream flow, C-type vertical-horizontal elbow with an upstream flow, D-type vertical-horizontal elbow with a downstream flow and E-type horizontal-horizontal elbow. Compared with the C/D-type elbow, where particles were injected uniformly, the A-type elbow and E-type elbow were found to increase erosion rate, while the B-type elbow decreases erosion rate. An interesting discovery is that the elbow erosion rate is relatively low for small particles when particles are injected from the middle and bottom positions of the inlet section of the elbow. Based on the observation, a novel preceding rotating sheet structure was developed to regulate the particle injection position. It shows an excellent anti-erosion performance by reducing the maximum erosion rate of particles with diameters of 50, 100, and 200 μm by 23%, 35%, and 43%, respectively.

Performance Evaluation of the Pressurized Synhelion Absorbing Gas Receiver

The pressurized design of the Synhelion absorbing gas receiver concept has been presented. Despite its intrinsic increased design complexity, foreseen advantages such as receiver downscaling and more compact piping and insulation systems were the drivers for the initial development of the 250 kWth receiver design operating at high pressure (10 bar absolute). The latter was driven by the results of specific computational fluid dynamics (CFD) simulations aimed at evaluating the receiver thermo-fluid dynamics behaviour along with the relative performance. This paper shows the results of the two initial CFD simulations campaigns aimed at evaluating the effect, on the receiver performance, of the integration of absorbing inserts (i.e., a series of concentric disks specifically arranged into the cavity to capture the incoming concentrated solar radiation) and the position and shape of the inlet section of the heat transfer fluid. The simulations results allowed not only to evaluate the receiver performance, in terms of thermal efficiency, but also to observe some criticalities related to the motion of the HTF through the receiver.

Performance analysis of multi-inlet cyclone separators considering different shapes and locations of the inlet ducts

The present study analyzes the performance of multi-inlet cyclone separators with different shapes and axial locations of the inlet ducts. The cyclone model having a single inlet has been considered as the reference model. The two inlets are incorporated such that the total cross-sectional area equals the original (single inlet) section – this ensures no change in the inlet velocity. Three cases for the shape of the cross-section have been considered. In the RA variant, the two inlet areas have been halved ensuring the same aspect ratio. In the RH variant, the height of the two inlets is half of the original duct. In the last case of the RW variant, the width of the two inlets is reduced by half of the original area. The impact of relative axial displacement between the two inlets is also analyzed. The advanced closure LES has been used to investigate the flow field as well as the performance. Conclusive results indicate that both pressure losses and collection efficiencies are the lowest in the RH variant and the highest in the RW variant. Furthermore, using continuous wavelet transformation, it has been revealed that the precessing frequency of the vortex core is time-dependent.

Study on the performance of tube evaporative cooling dehumidifier based on CFD

Most of the existing numerical models for falling film dehumidifiers consider two-dimensional adiabatic-type models. However, the performance of the adiabatic type dehumidifier is relatively poor, in addition to the fact that the two-dimensional model cannot well represent the flow process of liquid desiccant and the dehumidification process in the actual operation of the dehumidifier. Therefore, in order to better study the falling film of liquid desiccant and the heat and mass transfer process inside the tube, this paper established a three-dimensional model of the evaporative cooling falling film dehumidifier with higher dehumidification performance outside the tube based on CFD technology. The results showed that the simulation results of the constructed model were in good agreement with the experimental results, and the average relative error about 12 %. The out-of-tube evaporative cooling system cooled the dehumidifier through the combined effect of droplet evaporation and low-temperature liquid film on the outer wall surface. Under the baseline conditions: the dehumidification performance of the solution outlet section was better than that of the solution inlet section. The best cooling effect and dehumidification performance was achieved when the flow rate of shower water was 0.25 kg/(m2·s) and the flow rate of evaporative cooling air was 0.3 m/s. The dehumidification performance at a solution inlet velocity of 0.01 m/s was 79 % of that at 0.06 m/s; even if the solution flow rate was small, evaporative cooling dehumidifier still had a good dehumidification performance. The results of this paper provided a reference for the design of evaporative cooling type solution dehumidifier.

Fluid dynamic analysis and design strategies for a deswirler device for the direct measurement of radial turbine isentropic efficiency in experimental test rig

Turbocharging remains a key technology for improving the performance of automotive engines and plays a significant role in reducing fuel consumption, particularly when combined with downsizing and engine hybridization. Experimental information on the steady flow performance of turbochargers remains a crucial requirement for optimizing engine-turbocharger matching. This aspect is even more important referring to turbine efficiency, particularly in a radial inflow turbine used for turbocharging. The isentropic efficiency, which is directly evaluated based on measurements of thermodynamic parameters at the inlet and outlet sections, is affected by significant errors. This inaccuracy is mainly due to the non-uniform distribution of flow field and temperature at the outlet measuring section, which results in incorrect evaluation of the turbine outlet temperature, thus of turbine isentropic efficiency.This paper presents an experimental campaign aimed at evaluating the impact of a specific flow field conditioning device at the turbine outlet, with the goal of obtaining a direct evaluation of the turbine isentropic efficiency. A CFD model, which was validated using experimental data, was developed to better understand the performance of the flow field-conditioning device. Additionally, a simplified theoretical model was proposed to generalize the swirl boundary conditions, without the need to model the turbine. A porous medium was calibrated to simulate the honeycombs of the flow field. An optimization procedure was then integrated into the CFD model to provide design suggestions to improve the performance of the flow field conditioning device.

Sonlu Farklar Yöntemi Kullanılarak Geçirimsiz Baraj Tabanına Yerleştirilen Palplanş Perdesinin Yerinin Belirlenmesi

In water currents within the ground, a boiling event may occur if the flow direction is opposite to gravity in the outlet area of the flow floor. To prevent a boiling event, the length of the flow path is increased or a weight filter is used in the area where there is a risk of boiling. Increasing the length of the current path is possible by creating an impermeable layer in the upstream (inlet) section of the dam or by making an impermeable sheet pile wall under the dam. The construction of the sheet pile wall under an impervious dam is expensive and difficult. In this study, the sheet pile wall under the dam wall was placed in various positions between upstream region and downstream (outlet) region of the dam, and the value of the dam's seepage rate was analyzed by finite difference method. Vertical seepage rate values and safety numbers against vertical boiling have been found by taking the gradient of the hydraulic head. It has been seen that the sheet pile wall placed in the exit zone of the dam is the solution that minimizes the leakage rate, and, therefore, maximizes the vertical safety number against boiling.

U susret revitalizaciji turbina HE Đerdap 2: Merenje rasporeda vektora brzina na ulazima turbina

The continuous flow measurement on hydroelectric turbine units is conventionally carried out using the relative methods (mostly Winter-Kennedy), where the complex velocity field in flow cross section is replaced by a single measured quantity. On a physical model, mapping parameters are determined. The Winter-Kennedy method is most used, where this relative (index) flow quantity is obtained by measuring differential pressure. The measurement uncertainty of the determined flow using this method is usually significantly higher than the uncertainty of other relevant quantities for determining the optimal turbine operating conditions. To reduce the flow uncertainty, it is necessary to perform "absolute measurements" of the entire velocity field and determine the necessary corrections to the index method under real operating conditions. This is especially true for plants where disposition is different from one used on physical model, which is the case of “Đerdap 2” and recognized problem of skewed inflow. With the aim of better assessing the hydraulic efficiency of turbines and to collect data on the actual operating velocity distribution in the inlet section in front of trash-rack needed for planned revitalization works, an innovative system for absolute flow measurement has been designed and implemented. The moving frame was designed and installed at the turbine inlet, upstream from the trash-rack. The 15 electromagnetic (EM) sensors and two redundant acoustic Doppler sensors were installed on horizontal bar. Each sensor measures all three velocity components. The frame moves by lifting along the entire height of the flow section, allowing the entire velocity field to be scanned. The position of the frame is tracked by two encoders, while two pressure sensors are used to measure the water depth. Measurements are synchronized with the local SCADA system, so appropriate turbine operation data are also used. Considering the specificities of the measurement system itself with newly developed EM sensors, as well as hydraulic conditions, an adequate procedure has been developed to assess the uncertainty of the measured flow. This paper presents the measurement method and provides some measurement results on the units of the “Đerdap 2” hydroelectric power plant.

On the effectiveness of Reynolds-averaged and subgrid scale models in predicting flows inside car cabins

The aim of the present study is to analyze the performances of unsteady Reynolds-averaged Navier–Stokes (URANS) and large eddy simulation (LES) approaches in predicting the airflow patterns inside car cabins and to give insight in the design of computational fluid dynamics simulations of a real car cabin. For this purpose, one eddy viscosity-based turbulence model (shear stress transport k–ω) and two subgrid scale models (wall-adapting local eddy-viscosity and dynamic kinetic energy) were tested, and numerical results were compared with particle image velocimetry measurements carried out on a commercial car. The URANS model exhibited great accuracy in predicting the mean flow behavior and was appreciably outperformed by the LES models only far from the inlet sections. For this reason, it was deemed suitable for conducting further analyses, aimed at characterizing the airflow patterns in winter and summer conditions and performing a thermal comfort analysis. The thermal regime was found to have a very little effect on the air flow patterns, once the quasi-steady state regime is achieved; in fact, both in winter and in summer, the temperature field is fairly uniform within the car cabin, making the contribution of buoyancy negligible and velocity fields to be very similar in the two seasons. Findings also reveal that thermal comfort sensation can be different for passengers sharing the same car but sitting on different seats; this aspect should be considered when designing and operating the ventilation system, since the minimum comfort requirements should be met for all the occupants.

Synergistic effects of nano-enhanced waste transformer oil and hydrogen premixing on CI engine performance and emissions

Waste materials possess untapped potential when harnessed effectively. One such resource is waste transformer oil, derived from electrical transformers, which can be converted into a valuable fuel source for compression-ignition (CI) engines using pyrolysis techniques. In this study, we explored the utilization of a 50 % blend of waste transformer oil with diesel, augmented with Titanium dioxide nanoparticles (referred to as “nano fuel of waste transformer oil”), in an unmodified CI engine. To further enhance the performance of this nano fuel, we introduced hydrogen (at flow rates of 2.5 LPM, 5.0 LPM, and 7.5 LPM) into the inlet section during the suction phase, promoting premixing within the cylinder. Hydrogen premixing significantly improved combustion dynamics. Notably, when 7.5 LPM of hydrogen was introduced alongside waste transformer oil-derived nano fuel, a remarkable 37.30 % increase in brake thermal efficiency was achieved. Moreover, this configuration exhibited a 15.33 % reduction in brake-specific fuel consumption (BSFC), a 27.09 % decrease in carbon monoxide (CO) emissions, a 37.50 % decrease in unburned hydrocarbon (UHC) emissions, and a 28.53 % reduction in smoke opacity compared to traditional diesel operation. These results highlight the potential for enhanced CI engine performance and reduced emissions through the strategic combination of waste transformer oil-based nano-fuel and hydrogen premixing. Consequently, we recommend further exploration of hydrogen premixing in conjunction with nano-enhanced waste transformer oil for superior CI engine performance.

Методика и алгоритм расчета местных потерь напора в трубопроводах

The article is devoted to the hydraulic calculation of pipelines. For the storage of liquid products used in the national economy, there are tanks, which are usually combined into tank farms. Equipment for transporting liquids within the tank farm includes pumping units, pipelines, shut-off and control devices, etc. The growing needs of the economy create the necessity of build new and expand existing storage facilities for liquid products at industrial and transport objects. Hydraulic calculation is an important part of the tank farms pipeline systems design. This paper presents a methodology and algorithm for determining of local fluid pressure losses in pipelines. The calculation is based on the characteristics of pipeline system sections in which local hydraulic resistance occurs: a change in the diameter or direction of the pipeline, installation locations of auxiliary devices, etc. The Weisbach formula is used to calculate the local pressure losses. This takes into account the values of the local resistances coefficients and average flow velocities in the respective sections. The average flow velocities are determined by the given values of the flow rates and flow profiles on the sections. The local losses coefficients, depending on the type of resistance, are also found according to the calculation formulas, or are set as the initial values. Local pressure losses are calculated for curved sections of pipelines, conical transitions (confusers and diffusers), inlet and outlet sections, shut-off, control and safety valves, instrumentation, branches.