High Flow Coefficient Research Articles

Increasing energy efficiency and flow coefficient by determining fluid behaviours with computer aided design and CFD analysis in isolation valves

In this study, it was aimed to convey theoretical and practical development of the double eccentric butterfly valve, which would be the first in the sector, with highly efficient, saves energy, has a long life, and requires less maintenance. For this purpose, a prototype with lower weight and higher flow coefficient has been developed by the Computational Fluid Dynamics (CFD) method. Thanks to the use of computer aided design and simulation techniques, environmentally friendly and highly efficient valves have been produced, improving competitive conditions and an innovative product has been obtained in the sector. The design, CFD analysis, and casting simulation were carried out by Solidworks, ANSYS, and Anycasting computer programmes respectively. At the same time, as a result of this study, a design suitable for an innovative production technique that leads to less energy and less waste has been obtained. Innovative material selection and casting techniques were used by optimising the total material weight and valve cost.

Control of Flow and Acoustic Fields Around an Axial Fan Utilizing Plasma Actuators

Abstract Small axial fans, commonly employed for cooling electronic equipment, are frequently housed within narrow ducts, where intense tonal sound with duct resonance can occur, particularly when the blade passing frequency or its harmonic frequency aligns with the duct's resonance frequency. To mitigate resonant sound, this study proposes a flow control using dielectric barrier discharge plasma actuators, which induce a flow along the generation of plasma in air. The control effects on flow field, acoustic radiation, and aerodynamic characteristics are evaluated through direct aeroacoustic simulations and experiments conducted at different flow rates. The computational results reveal that swirling flow occurs in the inflow due to fan rotations at low flow coefficients. This swirling flow is weakened by utilizing plasma actuators, which are arranged to induce flows in the circumferentially reverse direction compared to fan rotations. This control method weakens the resonant sound at low and intermediate flow coefficients, while intensifying it at high flow coefficients, all at the same rotational speed. Moreover, the static pressure coefficient decreases and increases at low and high flow coefficients, respectively, with the latter attributed to an increase in the relative inflow angle induced by the control. Experimental findings demonstrate that the acoustic resonance was reduced by the control at both low and high flow rates, achieved by adjusting the rotational speed to maintain the same flowrate and static pressure rise as in the baseline case.

Computational Fluid Dynamics Simulation on Blade Geometry of Novel Axial FlowTurbine for Wave Energy Extraction

Wave energy converters (WECs) utilizing the Oscillating Water Column (OWC) principle have gained prominence for harnessing kinetic energy from ocean waves. This study explores an innovative approach by transforming the pivoting Denniss–Auld turbine blades into a fixed configuration, offering a simplified alternative. The fixed-blade design emulates the maximum pivot points during the OWC’s exhalation and inhalation phases. Traditional Denniss–Auld turbines rely on complex hub systems to enable controllable blade rotation for performance optimization. This research examines the turbine’s efficiency without mechanical actuation. The simulations were conducted using ANSYS™ CFX 2023 R2 to solve the three-dimensional, incompressible, steady-state Reynolds-Averaged Navier–Stokes (RANS) equations, employing the k-ω SST turbulence model to close the system of equations. A grid convergence study was performed, and the numerical results were validated against available experimental and numerical data. An in-depth analysis of the intricate flow field around the turbine blades was also conducted. The modified Denniss–Auld turbine demonstrated a broad operating range, avoiding stalling at high flow coefficients and exhibiting performance characteristics like an impulse turbine. However, the peak efficiency was 12%, significantly lower than that of conventional Denniss–Auld and impulse turbines. Future research should focus on expanding the design space through parametric studies to enhance turbine efficiency and power output.

Design, optimization, and performance analysis of a subsonic high-through flow turbine

This paper presents the design method and numerical analysis results of a two-stage high-through flow (HTF) high-pressure turbine. Compared to conventional design principles, the HTF turbine proposed in this study is a kind of high flow coefficient turbine. This design scheme enables the turbine to effectively increase the output power and thrust while maintaining the same windward area. At the design speed, the pressure ratio of the HTF turbine is 3.8, with an adiabatic efficiency of 91.46%. The flow coefficients of the first and second stage are 0.76 and 0.86, respectively, and the loading coefficients are 2.55 and 1.47. Detailed design parameters, flow characteristics, and aerodynamic performance are presented in this paper. Based on the preliminary design result, the second stage turbine was optimized for a wide range of operating conditions. The computational fluid dynamics simulation results show that compared with the traditional turbine, the loading form of the HTF turbine changes from aft-loaded to front-loaded. In addition, there is a certain increase in tip leakage of the turbine. This study achieves high efficiency, while increasing the turbine flow rate, and provides a corresponding reference for the design method of improving turbine flow capacity.

Numerical Investigation of Butterfly Valve Performance in Variable Valve Sizes, Positions and Flow Regimes

Reliability and efficiency of valves are necessary for precise control and sufficient heat-flow to heat application plants for the integrated energy systems of nuclear power plants (NPPs). Strategic Management Analysis Requirement and Technology (SMART) valves’ ability to control flow and assess environmental parameters stands out for these requirements. Their ability to sustain the downstream flow rate, prevent reverse flow, and maintain pressure in the heat transport loop is much more efficient with the integration of sensors and intelligent algorithms. For assessing valve performance and monitoring, mechanical design and operating conditions are two important parameters. In this study, the butterfly valves of three different sizes are simulated with water and steam using STAR-CCM+ in various flow regimes and positions to analyze performance parameters to strategize an automated control system for efficiently balancing the heat–transport network. Also, flow behavior is studied using velocity and pressure fields for valve–body geometry optimization. It can be observed, through performance parameters, that the valves are suitable for operation between 30° and 90° positions with significantly low loss coefficients and high flow coefficients, and the performance parameters follow a certain pattern in both water and steam flow in each scenario.

Effect of the Return-channel Geometric Parameters on the Performance of a Centrifugal Compressor with a High-flow Coefficient

The return-channel of a preceding stage in a multi-stage centrifugal compressor has a significant effect on the aerodynamic performance of the current and subsequent stages. However, due to the relatively complex nature of the return-channel configuration with many geometric parameters, no general design guidance is available in the literature. In this study, numerical methods are used to study the effects of different geometric parameters of a return-channel on the performance of a high-flow-coefficient centrifugal compressor. A multi-objective genetic algorithm is applied to optimize the return-channel. The effects of different geometric parameters on the performance are then studied using a sensitivity analysis method. Calculation results show that the residual vortex intensity at the outlet of the return-channel is affected by the geometric angles of the inlet and outlet of the return-channel blades. The flow uniformity at the stage outlet is primarily affected by the geometric angle of the blade outlet and the number of blades. The overall performance of the compressor stage is primarily affected by the geometric angle of the blade inlet and the lateral inclination angle of the cover plate. Calculation results for a two-stage compressor consisting of the optimized first stage and its following stage show that the outlet flow field of the first stage is more uniform than the original first stage. Additionally, at the design operating condition, the polytropic efficiency and pressure ratio of the entire unit increase by 1.07% and 4.07%, respectively. The polytropic efficiency and pressure ratio for the second stage increase by 2.34% and 3.51%, respectively. The impeller head coefficient increases by 7.33%. The theoretical analysis shows that for high-flow-coefficient centrifugal compressors, reducing the residual vortex intensity of the outlet flow field of the return-channel in a stage can significantly improve the off-design performance of the following stage.

Design and Analysis of Oscillating Water Column Wave Energy Converter Using Contra Rotary Self-rectifying Impulse Turbine

Background: The global energy demand is rising day to day. To cover the energy gap, governments around the world are pursuing a variety of strategies to meet energy demands. However, according to the long-term strategy, all nonrenewable energy plants must be replaced with renewable energy sources. Existing technologies are enhanced, and new sources are being investigated for this purpose. The ocean covers 70% of the planet so there is a huge potential to extract energy from this source. Objective: This research aims to optimize the design of an oscillating water column (OWC) wave energy converter to extract energy from ocean waves. Methods: The total efficiency of an OWC wave energy converter is determined by the turbine's design configuration and the chamber's partially submerged water column. The various designs of wave energy turbines were examined before simulating the contra rotary impulse turbine with middle vanes at specific angles. The efficiency of the turbine was determined using ANSYS FLUENT workbench simulations. Additionally, the design of an OWC was simulated to determine the optimal chamber slope. To conduct experiments, a 3D-printed contra rotary self-rectifying impulse turbine with middle vanes was generated as a demonstration model. Middle vanes used in contra-rotary turbines can assist in reducing turbulence between contra rotors. Results: The results demonstrate that the turbine with middle vanes has a higher torque coefficient Ct than the turbine without middle vanes. Similarly, the input coefficient Ca is higher for the turbine which has middle vanes. Therefore, the turbine with a middle vane shows better efficiency than the turbine without a middle vane in low flow coefficient as well as higher flow coefficient. Conclusion: The efficiency of the contra rotatory turbine is greater than the single rotatory turbine and the efficiency increases further when middle vanes are added.

Toward the Utilization of 3D Blading in the Cantilevered Stator from Highly Loaded Compressors

Three-dimensional blading is an efficient technique in compressor aerodynamic design, and its function mechanism in the cantilevered stator needs to be addressed. This paper focuses on the sweep and dihedral in the cantilevered stator and seeks to expose their effects through detailed flow field analysis. Results show that the forward sweep could alleviate the corner flow separation by preventing the accumulation of the secondary flow toward the corner region, resulting in stronger flow separation at the blade trailing edge; in summary, forward sweep with appropriate parameters could increase static pressure rise by 14.3%. The positive dihedral will carry the endwall flow to the upper-span sections, thereby reducing blade corner separation; hence, as much as 23.5% improvement in static pressure rise could be obtained with the appropriate dihedral. Moreover, the combination of a relatively large sweep height and a moderate sweep angle with a low dihedral height and a moderate sweep angle provides optimum aerodynamic performance; the static pressure rise coefficient sees an increment of 25.5% at the near stall point. An experiment is then performed to further validate the theory, which shows a 2% improvement in efficiency of 3D blading at small mass flow rates. However, the secondary leakage should be given attention at high mass flow coefficients, while the corner separation needs further elimination at small mass flow rates.

Passive flow control via tip grooving and stall fencing mechanisms of a marine energy harvesting turbine

Remarkable advancement in wave energy conversion technology has taken place in recent years. Due to its simplicity, the Wells turbine has been one of the most widely used power take-off mechanisms in an oscillating water column type wave-energy conversion device. However, the turbine suffers from several challenges due to its narrow operating range, which hinders the commercial feasibility of the system. Several aerodynamic applications have successfully used passive control methods to modify the flow conditions. This work applied a combination of stall fences and casing grooves for passive flow control of a Wells turbine. The computational fluid dynamics (CFD) technique is used to analyze the modified turbine numerically. The casing groove modified the tip-leakage vortices, interacted with local vortices created by the stall fences, and helped reattach the flow at higher flow coefficients. As a result, the modified turbine increases the operating range up to 33.3%. In addition, the peak-to-average (PTA) power ratio decreased by up to 27.7%.

Light Nuclei and Hyper Nuclei Collectivity Measurements at High Baryon Density Region

High energy heavy-ion collisions produce large amounts of light nuclei and hype nuclei, especially at high baryon density around collision energy of several GeV. These light nuclei and hyper nuclei carry the information of nucleon-nucleon and hyperon-nucleon interactions and affect the chemical composition and properties of the collision system. This proceeding is a brief review for the recent measurements on light nuclei collective flow, including directed flow v1, elliptic flow v2, and high order flow coefficients, at finite and high baryon densities from different experiments. The light nuclei production mechanism is discussed based on comparisons of the measurements and model calculations. The first measurement for hyper nuclei v1 at 3 GeV by STAR is also reported, which may imply the hyper nuclei are formed via the coalescence of nucleons and hyperon.

An Investigation of Non-Linear Surge Characteristic in a High-Speed Centrifugal Compressor

Abstract In centrifugal compressors, it is common to observe a rapid reduction in surge margin toward high rotational speed, which shows a non-linear surge characteristic against the change of rotational speed. This paper presents a comprehensive experimental and numerical study to understand the flow mechanisms leading to the non-linear surge behavior in a high-speed centrifugal compressor. It shows that for the studied compressor, there are two critical flow coefficients (ϕ = 0.255 and 0.136) where the stability of the compressor stage is significantly weakened. At a higher speed, the impeller rotating stall happens at the first critical point where the diffuser instability is also enhanced. This is caused by the increase of the flow non-uniformity at the impeller exit as well as increased diffuser inflow angle due to the impeller compressibility effect. Therefore, both the impeller and diffuser’s instability are matched and trigger the surge at a high flow coefficient. In contrast, at a lower speed, the diffuser instability is not enhanced by the impeller rotating stall, this mismatch of the two component’s instability allows the compressor to pass through the first critical point and extend the surge limit to the second critical point where the diffuser reaches the stability limit and causes the rotating stall spontaneously. By these different behaviors at each speed, the non-linearity of the surge characteristic is established.

Numerical Predictions of Mean Performance and Dynamic Behavior of a 10 MWe SCO2 Compressor With Test Data Validation

Abstract High-fidelity aerodynamic analysis has been demonstrated for mean performance and unsteady dynamics in a sCO2 compressor designed by Hanwha Power Systems Americas for a 10 MWe Concentrating Solar Power plant. Simulations were performed with crunchcfd® software tool that was matured to accurately model near critical real fluid effects in sCO2. Pretest predictions for mean performance were validated with test data collected later. Performance predictions were accurate and captured sensitivity of the efficiency to inlet temperature of CO2 as well as steep drop-off at high flow rates due to condensation in the inlet throat. Detailed analysis was performed to understand the source of these performance losses at near critical conditions. Unsteady dynamic effects in the compressor at off-design conditions were also identified and quantified. In particular, a system wide “condensation surge” condition was detected at high flow coefficients that results in large amplitude pulsations with accompanying mass flow fluctuations at low frequencies and has potential to cause damage in closed-loop systems.

A study of counter-rotating impulse turbine for wave energy conversion-effect of middle vane thickness on the performance-

Abstract In an oscillating water column (OWC) based wave energy device, a water column that oscillates due to the sea wave motion generates a bi-directional airflow in an air chamber, and finally, the bi-directional airflow driven air turbine converts the pneumatic energy into mechanical energy. The counter-rotating impulse turbine for bi-directional airflow has been proposed by M. E. McCormick of the United States Naval Academy in 1978. In a previous study, the authors investigated the effect of the turbine geometry on the performance of a counter-rotating impulse turbine for bi-directional airflow, and it was clarified that the efficiency of the turbine is higher than an impulse turbine with a single rotor for bi-directional airflow in a range of high flow coefficient. Moreover, this impulse turbine has a disadvantage that the efficiency in a range of low flow coefficient is remarkably low due to the deterioration of the flow between the two rotors. In this study, in order to make the counter-rotating impulse turbine practically compatible, the thickness of the middle vanes installed between the two rotors was changed, and the effect of the thickness on the turbine performance was investigated by the computational fluid dynamics (CFD) analysis. As a result, it was found that the efficiency of the counter-rotating impulse turbine with middle vanes increases as the thickness of the middle vanes decreased.

Enhancement of OWC Wells turbine efficiency and performance using riblets covered blades, a numerical study

Oscillating water column (OWC) is one of the first devices used for wave energy conversion. This wave absorber converts pneumatic energy to mechanical energy through a Wells turbine. In this paper, the micrometer protrusions similar to shark skin (riblet) were added to the Wells turbine blades to investigate its effect on the improvement of the device performance as well as its efficiency. The flow interaction with Wells turbine was modeled using Star CCM+ software. In this process, the structured grid was used throughout the study domain. The numerical modeling results show that for high flow coefficients, applying riblet on the blade surface results in an increase in the thrust coefficient and a decrease in the blade suction surface pressure. The proposed design significantly improves the pressure distribution around the blade and the separation point, as well as the efficiency of the turbine within the computational range. Another benefit of riblets is the delay and reduction of separation at the tip of the blade. In addition, there is an increase of 18.4% in the torque coefficient and 16.8% in the efficiency of the riblet covered blades in deep fatigue conditions. Furthermore, the results show that in computational range, the Wells turbine demonstrates 2.3% increase in efficiency.

Regional Physiographic Study for the Hydrology of Kali Lamong Watershed Area

This study aims to determine the effect of physiography based on slope and land cover for water control in Kali Lamong watershed. The data used in this research are DEM data and Landsat 8 imagery data. The process of processing slope data is through conversion coordinates system, DEM clip, create slope, reclassify, dissolve shapefile, and slope classification analysis. Landsat 8 data processing goes through a process through conversion coordinates system, composite band, crop composite, extent shapefile, sharpen band, unsupervised classification, and land cover classification analysis. Slope classification maps and land cover classification maps are used for flow coefficient classification for physiographic analysis based on slope and land cover for water control in Kali Lamong watershed. On the land cover classification map, five land classifications were obtained, namely agriculture (158413000 m2), settlements (72701400 m2), industrial land (11571600 m2), plantations (46017800 m2), and waters (15268500 m2). On the slope classification map obtained 5 classifications, as flat with a slope of 0-8% (288469544 m2), as slope with a slope of 8-15% (7656738 m2), as rather steep with a slope of 15-25% (1905360 m2), as steep with a slope of 25-45 (526614 m2), and as very steep with a slope of more than 45% (32148 m2). From the combination of Landsat 8 image data and slope data, flow coefficient analysis was carried out. The flow coefficient is influenced by land cover and slope. From this research, the classification of low flow coefficient is less than 0.25, medium flow coefficient is 0.25-0.5, and high flow coefficient is more than 0.75. The average flow coefficient of Kali Lamong watershed is 0.49 with a moderate flow coefficient classification value. This shows that 49% of the runoff water is in Kali Lamong watershed. The higher the flow coefficient value, the water runs off the surface. So that it can be used as an initial study for the technical planning of Kali Lamong hydrology and the development, improvement, utilization, and control of water flow in Kali Lamong.

The Effect of Land use Changes on the Paya Tumpi Flash Flood, Central Aceh District

Central Aceh Regency is a highland area with little risk of flooding due to its elevation, allowing water to drain quickly. Floods began to occur more frequently in the Central Aceh District in 2015s, with overflowing water in Urban Drainage in various locations. The land use of the Paya Tumpi Waterway Network has shifted from forest to agricultural. As evidenced by the high flow coefficient, which can lead to flooding in the Paya Tumpi watershed area, insufficient agricultural land processing can wreak havoc on the hydrological function of the water flow network. A low topography characterizes the site. Due to an overflown of the water flow network in Paya Tumpi village, Central Aceh Regency experienced a Flash Flood on May 13, 2020. The main issue addressed in this research is the impact of land changes on the hydrological function of the water flow network against Banjir Bandang. Using hydrological analysis and land change, we determined the flood discharge that occurred. In deciding the flood discharge, hydrological analysis and land change analysis using GIS software were used. The findings revealed that the flood influenced changes in land use, causing the water network's capacity to become ineffective.

The Effect of Land use Changes on the Paya Tumpi Flash Flood, Central Aceh District

Central Aceh Regency is a highland area with little risk of flooding due to its elevation, allowing water to drain quickly. Floods began to occur more frequently in the Central Aceh District in 2015s, with overflowing water in Urban Drainage in various locations. The land use of the Paya Tumpi Waterway Network has shifted from forest to agricultural. As evidenced by the high flow coefficient, which can lead to flooding in the Paya Tumpi watershed area, insufficient agricultural land processing can wreak havoc on the hydrological function of the water flow network. A low topography characterizes the site. Due to an overflown of the water flow network in Paya Tumpi village, Central Aceh Regency experienced a Flash Flood on May 13, 2020. The main issue addressed in this research is the impact of land changes on the hydrological function of the water flow network against Banjir Bandang. Using hydrological analysis and land change, we determined the flood discharge that occurred. In deciding the flood discharge, hydrological analysis and land change analysis using GIS software were used. The findings revealed that the flood influenced changes in land use, causing the water network's capacity to become ineffective.

On the Correlation Between Spanwise Inducer Incidence and Impeller Diffusion for Ruled Surface and Barreled Sweep-Bow Impeller Design at Inlet Guide Vane-Off-Design

AbstractIn the present paper, three centrifugal stages of high volume flow coefficient are compared to each-other regarding their aerodynamic performance in design point and off-design point conditions at different speed and inlet guide vane (IGV)-setting angle: two stages with full-blade design (no splitter blades) have been numerically designed with different design geometry methodology. One geometry is based on a classical ruling surface design with a linear leading edge, the second geometry based on a fully-three-dimensional surface including a blade bow at the trailing edge and a barreled sweep at the leading edge. According to impeller test rig measurements and computational fluid dynamics (CFD) calculation, the classical ruling surface designed impeller outperforms the more sophisticated centrifugal stage with fully 3D-blade at fully axially guided IGV-flow. In the contrary, at closing IGV-off-design setting angles, toward surge operation, the fully 3D-blade impeller performs with higher efficiency and steeper negative pressure slope. On the search of the geometrical causes for the different aerodynamic performance (especially at IGV-off-design conditions), focus is set on the analysis of IGV-flow-interaction with the inducer flow and impeller diffusion. The one-dimensional analysis of the spanwise flow at the impeller leading edge reveals that, compared with the ruling surface impeller, the fully 3D-blade performs with lower flow incidence losses in favor to IGV-off-design operation than at IGV-neutral position. The streamwise flow analysis confirms the improved flow incidence characteristics of the 3D-blade impeller due to reduction of aerodynamic blockage and entropy production in the vicinity of the impeller leading edge. Based on CFD calculations, a new correlation of secondary flow and flow incidence is proposed, to be used for one-dimensional modeling.

The fate of nonlinear perturbations near the QCD critical point

The impact of the QCD critical point on the propagation of nonlinear waves has been studied. The effects have been investigated within the scope of second-order causal dissipative hydrodynamics by incorporating the critical point into the equation of state, and the scaling behavior of transport coefficients and of thermodynamic response functions. Near the critical point, the nonlinear waves are found to be significantly damped which may result in the disappearance of the Mach cone effects of the away side jet. Such damping may lead to enhancement in the fluctuations of elliptic and higher flow coefficients. Therefore, the disappearance of Mach cone effects and the enhancement of fluctuations in flow harmonics in the event-by-event analysis may be considered as signals of the critical endpoint.

Performance of 2-D inlets with curved compression surface formed by segments with controllable compression angle

Suppose that curved surface consists of tiny polylines. Two 2-D inlets with curved surfaces formed by equal compression angles of the micro-element segments and a slight increase in the compression angle of the micro-element segments are designed respectively. The numerical simulation method is used to compare the performance of two curved surface 2-D inlets with the reference three-wedge compression 2-D inlet. Select NASA classic test data, in order to determine the turbulence model and calculation method chosen by the numerical simulation Fluent software. Numerical simulation results show: the pressure ratio of the curved compression system at the place corresponding to the wedge compression second shock wave is only 0.55 of the wedge compression pressure ratio, which is much smaller than the critical pressure ratio of the boundary layer separation; at design point, the performance of three inlets is similar; at non-design points, the 2-D inlets with the curved surface have a higher flow coefficient and total pressure recovery coefficient. The configuration of the small segments compression angles is the key to the performance of the curved surface compression two-dimensional inlet.