Characteristics Of Turbine Research Articles

A model for predicting the unsteady hydrodynamic characteristics on the blades of a horizontal axis tidal turbine

Tidal current turbines operate in a highly turbulent environment, which results in significant fluctuations in unsteady loads and consequent fatigue and dynamic failures in the rotor. Therefore, accurate calculation of these unsteady loads is crucial. However, the existing models do not take into account the influence of varying relative blade section thickness on dynamic stall when predicting the unsteady characteristics of horizontal axis tidal turbine (HATT) blades. To forecast the unsteady characteristics of the HATT blades, this study developed a method that considers the influence of relative blade thickness on dynamic stall. The modified Leishman-Beddoes (L-B) dynamic stall model, 3D rotational augmentation model, and steady-state BEM model were combined to predict the unsteady hydrodynamic characteristics of blades by synthesizing the transient inlet velocities induced by waves, shear flow and turbulence. In this method, the static parameters required for the modified L-B dynamic stall model were calculated by XFOIL within a range of small angle of attack (AoA) and then extrapolated to cover the entire range of AoA using the Viterna extrapolation method. The required dynamic parameters were obtained by CFD numerical simulation. This method, that we call HATT-UCPM, can consider both the effects of a single element on the unsteady hydrodynamic characteristics of the blades, as well as the combined effects of shear flow, waves, and turbulence on the blades in the actual marine environment. The accuracy of the method was validate through CFD numerical simulation. The results showed that the proposed method has a high consistency with the numerical simulation results, indicating that it has a good accuracy in the prediction of unsteady characteristics of HATT blades. Finally, the study examined several cases to investigate the impacts of shear flow, waves, and turbulence on the unsteady loads of blades, both individually and in combination.

A new similarity criterion for wind tunnel testing of floating wind turbines achieving dynamic aerodynamic characteristics similarity

Floating offshore wind turbines have rapidly advanced in recent years, prompting numerous experiments. Small-scale turbines require blade redesign with low Reynolds number airfoils due to the scale effect. Consequently, the chord length of these blades no longer corresponds to the length scale, leading to dissimilar dynamic aerodynamic phenomena during platform movement. To address this, a new criterion is proposed for wind tunnel tests of floating offshore wind turbines. The criterion incorporates reduced frequency correction and optimal tip speed ratio (TSR) matching. It ensures hydrodynamic similarity through Froude number similarity and avoids excessive low wind speed through wind speed correction. Optimal TSR matching ensures the model and prototype turbines operate within similar power curve intervals. Reduced frequency corrects the platform sine motion parameters, providing the model turbine with a dynamic aerodynamic effect similar to the prototype. The National Renewable Energy Laboratory’s 5 MW wind turbine is chosen as the prototype, and the model wind turbine blades are designed using NACA 4412 airfoil and the criterion of thrust coefficient similarity. The sub-module of the FAST, AeroDyn is employed to validate the new criterion for different surge motions between the NREL 5 MW and the model. Under the new similarity criterion, the model turbine exhibits a relative root mean square error of 4.61 % and 1.54 % in power coefficient and thrust coefficient, a significant improvement compared to the current similarity criterion's relative root mean square error of 24.74 % and 8.36 %. The results reveal a circular trend variation in both thrust coefficient and power coefficient with position. Notably, the new criterion demonstrates a closer alignment with the dynamic aerodynamic characteristics of the prototype when contrasted with the current similarity criterion. Furthermore, this model design, tailored for the NREL 5 MW turbine, can be applied to model experiments with various turbine configurations. It has been successfully verified for the IEA 15 MW turbine, exhibiting promising simulation results. The proposed similarity criterion is suitable for wind tunnel testing, addressing the problem that the current similarity criterion cannot reflect the dynamic aerodynamic characteristics of prototype wind turbines. Additionally, it enables experiments on different prototype configurations using a single model turbine, reducing wind tunnel testing costs.

Transient coupling modeling and dynamic response analysis of hydraulic turbine governing system and shafting system

To address the challenges posed by the connection of new energy sources to the grid, pumped storage power stations (PSPSs) are required to frequently engage in transient processes to maintain load balancing and regulate grid frequency. It remains difficult, however, to evaluate the transient characteristics of the hydraulic turbine governing system (HTGS) and shafting system because of the lack of suitable models. This study seeks to address this challenge by establishing a transient turbine model based on the surface-cluster method and the shafting system transient coupling model, accounting for hydraulic-mechanical-electrical factors. HTGS and shafting systems' dynamic response characteristics are investigated under two small oscillation processes and eleven closure laws of guide vanes (CLGVs). The findings reveal that the shafting system vibration increases with the load drop during small oscillation processes. Conversely, sudden load increases reduce shafting vibration and the change of vibration is related to the force of the blade. Moreover, the study identifies that under the fast-slow two-phase CLGV, the maximum relative head and rotor radial amplitude increase with decreasing guide vanes (GV) opening of the turning point, while the change in maximum relative speed is opposite. Under the slow-fast two-phase CLGV, the maximum head and speed increase with decreasing GV opening of the turning point, while the maximum radial amplitude of the rotor is the opposite. Finally, under all the three-phase CLGVs, the transient characteristics of the head, speed, and shafting vibration under close-close-close (CCC) CLGV are the best. The innovation of this paper is to provide a method to establish the transient coupling model of HTGS and shafting, and to study the stability and transient response characteristics of HTGU.

Numerical Investigation of Inner Flow Characteristics of a Prototype Pump Turbine with a Single Pier in Draft Tube at Part Load Conditions

Pump turbines operate under various off-design conditions, resulting in complex internal flow patterns. This study employs Reynolds-averaged Navier–Stokes (RANS) numerical methods to investigate the flow characteristics of a prototype pump turbine with a single draft tube pier in turbine mode, and then, the flow characteristics inside the draft tube are discussed with emphasis. Asymmetry between the pier-divided draft tube passage flows is inevitable due to the elbow section’s curvature. Most of the fluid flows out of one passage, while vortex motion dominates the interior of the other one, resulting in completely different pressure fluctuation characteristics for the two flow passages. The large-flow passage is mainly characterized by the wide band in the frequency domain, corresponding to the recirculation zone, while some of the measured points in the low-discharge passage exhibit frequency splitting under kinematic progression. Further analysis demonstrates a low-frequency peak corresponding to the complementary shape between the vortex rope and the recirculation zone. This work elucidates the effects of the pier on the flow behavior and pressure fluctuation characteristics inside the draft tube and fills the research gap on piers in the field of pump turbines.

Adaptation of von Karman Institute for Fluid Dynamics’ Isentropic Compression Tube Facility for High-Speed Low-Pressure Turbines Testing

Abstract This paper presents the commissioning of a newly designed High-Speed Low-Pressure Turbine (LPT) stage, operating at transonic exit Mach numbers and low Reynolds numbers, typical of modern geared turbofan (GTF) applications. The work falls within the scope of the Clean Sky 2 project SPLEEN (Secondary and Leakage Flow Effects in High-speed Low-pressure Turbines), which consists of an extensive experimental characterization of LPTs for GTFs. Geometries and measurements will constitute a valuable open-access database for the validation of simulation methods and data analysis tools. At first, the characteristics of the research turbine are illustrated. The LPT stage is designed with an equal number of stationary vanes and shrouded rotor blades. The upstream and downstream hub cavities are purged and feature engine-realistic rim seals. The nominal operating condition of the stage is reported, along with a set of off-design conditions, obtained by varying rotor speed and purge mass flows. The second part of the paper describes the substantial revamping of the CT3 large-scale compression tube at Von Karman Institute for Fluid Dynamics, traditionally employed for high-pressure turbine testing, now adapted to host a high-speed LPT stage. The third section is an overview of the time-averaged and fast-response instrumentation. The test article is heavily instrumented, to maximize the amount of acquired data, while minimizing the number of blowdown tests. The dataset for each operating conditions includes aerothermal measurements in the annulus flow, in the hub cavities and in the shroud labyrinth seal. In addition, this section presents the design of an in-house traversing system for continuous probe traversing during the test. Finally, the outcome of the commissioning phase is discussed, with particular emphasis on the operating conditions stability, as well as on the inlet and cavity injection uniformity. The commissioning of a traversing system for continuous probe traversing during the short-duration test is also discussed.

Hydrodynamic Performance and Flow Field Characteristics of Tidal Current Energy Turbine with and without Winglets

In order to gain a more comprehensive understanding of the influence of winglets on the hydrodynamic performance and flow field characteristics of tidal current energy turbines, two different shapes of winglets are designed, and numerical simulation results for turbines with and without winglets are compared and analyzed. The results show that both shapes of winglets can improve the energy conversion efficiency, and the winglets with a cant angle (60°) are more effective than the flat (0°) winglets; the winglets transfer the tip vortices to the winglet tips and weaken the tip vortices, increase the pressure coefficients of the cross-section in the tip region, and inhibit the three-dimensional flow phenomenon in the tip region; the winglets will make the wake axial velocity deficit larger in the near-wake region, and with the axial distance increases, the axial velocity of the wake flow with winglets recovers faster than that without winglets; winglets can make the vortex pairing and breaking of the turbine tip vortex faster, which can also be observed by the change in the turbulent kinetic energy (TKE).

Analysis of Solid-Liquid Two-Phase Flow in the Area of Rotor and Tailpipe

In order to study the internal flow state and wear law of a bulb cross-flow unit based on the particle non-uniform phase model in the Euler–Euler method, the solid-liquid two-phase flow condition of the hydraulic turbine under different solid-phase diameters, concentrations, and guide vane openings is calculated. The results show that (1) Under the same solid-phase physical parameters, the distribution of solid-phase concentration on the working surface of the blade is positively correlated with the opening degree of the guide vane, the concentration of the solid phase on the back of the blade is negatively correlated with the opening degree of the guide vane. (2) The addition of the solid phase changes the time-domain period of pressure pulsations at the rotor inlet and the tailpipe inlet under clear water conditions, and the tailpipe pressure pulsation coefficient decreases with increasing solid-phase concentration. The pressure pulsation coefficient increases with increasing solid-phase diameter and concentration at the inlet of the rotor. (3) Numerical simulation of the wear characteristics of cross-flow turbine by Finne’s wear model reveals that the two-phase flow condition with high concentration, large particle size and small openings has a more serious effect on turbine blade wear.

An investigation on asymmetric flow characteristics of asymmetric twin-scroll turbine

Asymmetry, as the most significant characteristic of asymmetric twin-scroll turbines, has a significant effect on the flow characteristics of asymmetric twin-scroll turbines. In this paper, the effect of asymmetry on flow parameters, efficiency, twin-scroll pressure ratio ( SPR), single admission twin-scroll flow parameters ratio ( SSMR) and twin-scroll divide wall of asymmetric twin-scroll turbines were investigated for the first time. First, several turbines with the same total critical section of twin scrolls and different asymmetries were designed, as well as several turbines with the same asymmetric twin scrolls and different heights of the divide wall. Subsequently, these asymmetric twin-scroll turbines were tested and studied on the turbine performance rig. Asymmetry had little influence on turbine flow characteristics under equal admission, but a great impact under partial and single admission. Meanwhile, SMR had a low slope linear relationship with the expansion ratio for every asymmetry turbine. Moreover, the asymmetry was approximately linear with the average single admission twin-scroll pressure ratio ( SSMR ave), which could be used to guide the early design of asymmetric twin-scroll turbines. Besides, divide wall schemes testing found that the length of divide wall had a certain effect on the SSMR ave, which is a control factor to maintain asymmetric property. Finally, the relation between the expansion ratio of small or large scroll turbines and lg(SPR) was approximately exponential function, and the exponential parameter was strongly correlated with SSMR and SSMR ave, which could be the key parameter reflecting the asymmetry.

Effects of submergence depth on the performance of the savonius hydrokinetic turbine near a free surface

The influence of the submergence depth ratio on the Savonius hydrokinetic turbine and flow characteristics is numerically studied under different tip speed ratios. The tip speed ratio TSR (Ratio of the flow speed to blade speed) changes from 0.4 to 1.2, and the submergence depth ratio H*(Ratio of the depth to the turbine diameter) ranging from 0.22 to 1.1. The main conclusions are: (1) When the submergence depth ratio increases from 0.22 to 0.66, the flow field structure gradually becomes regular, and the power coefficient keeps increasing. (2) When the submergence depth ratio reaches up to 0.88, the curve of the power coefficient is similar to that of H* = 1.1, which means the effect of free surface can be ignored when H*>0.88. (3) According to the pressure distribution around the turbine, the free surface will increase the pressure difference on the blade due to the surface tension and blockage effect, thereby influencing the rotation of the turbine. (4) As the TSR increase, the submergence depth ratios of 0.55 and 0.88 are regarded as two demarcation points of the average power coefficient.

Experimental Study on the Flow Characteristics of Two-Stage Variable Turbines in a Twin-VGT System

The twin variable geometry turbocharger (VGT) System, through efficient use of exhaust energy, maximizes internal combustion engine (ICE) power, reduces exhaust emissions and improves reliability. However, the internal flow characteristics of the twin-VGT system are greatly affected by the environment. To ensure that the two-stage adjustable supercharged internal combustion engine is efficient in all geographical environments and under all operating conditions, it is necessary to conduct in-depth research on the internal flow characteristics of high- and low-pressure turbines. In this paper, an experimental system of the flow characteristics of a double variable-geometry turbocharging (twin-VGT) system is designed and developed. A two-stage variable turbine flow characteristic test was carried out, focusing on the relationship between the initial rotational velocity of high variable-geometry turbocharging (HVGT) and blade opening in low variable-geometry turbocharging (LVGT). The effects of high- and low-pressure variable-geometry turbocharger (VGT) blade opening on available exhaust energy, expansion ratio distribution, blade velocity ratio, compressor power consumption and isentropic efficiency were studied. The results show that when the available energy of exhaust gas is constant, with the increase in HVGT turbine speed, when the LVGT blade opening decreases by 10%, the low-pressure turbine expansion ratio increases by about 0.23.

Wake characteristics of a balloon wind turbine and aerodynamic analysis of its balloon using a large eddy simulation and actuator disk model

Abstract. In the realm of novel technologies for generating electricity from renewable resources, an emerging category of wind energy converters called airborne wind energy systems (AWESs) has gained prominence. These pioneering systems employ tethered wings or aircraft that operate at higher atmospheric layers, enabling them to harness wind speeds surpassing conventional wind turbines' capabilities. The balloon wind turbine is one type of AWESs that utilizes the buoyancy effect to elevate the turbine to altitudes typically ranging from 400 to 1000 m. In this paper, the wake characteristics and aerodynamics of a balloon wind turbine were numerically investigated for different wind scenarios. Large eddy simulation, along with the actuator disk model, was employed to predict the wake behavior of the turbine. To improve the accuracy of the simulation results, a structured grid was generated and refined by using an algorithm to resolve about 80 % of the local turbulent kinetic energy in the wake. Results contributed to designing an optimized layout of wind farms and stability analysis of such systems. The capabilities of the hybrid large eddy simulation and actuator disk model (LES–ADM) when using the mesh generation algorithm were evaluated against the experimental data on a smaller wind turbine. The assessment revealed a good agreement between numerical and experimental results. While a weakened rotor wake was observed at the distance of 22.5 diameters downstream of the balloon turbine, the balloon wake disappeared at about 0.6 of that distance in all the wind scenarios. Vortices generated by the rotor and balloon started to merge at the tilt angle of 10∘, which intensified the turbulence intensity at 10 diameters downstream of the turbine for the wind speeds of 7 and 10 m s−1. By increasing the tilt angle, the lift force on the wings experienced a sharper increase with respect to that of the whole balloon, which signified a controlling system requirement for balancing such an extra lift force.

Aerodynamic Characteristics of Wind Turbines Operating under Hazard Environmental Conditions: A Review

This paper provides a review of the aerodynamic behavior of horizontal axis wind turbines operating in hazardous environmental conditions. Over the past decade, renewable energy use has accelerated due to global warming, depleting fossil fuel reserves, and stricter environmental regulations. Among renewable options, solar and wind energy have shown economic viability and global growth. Horizontal axis wind turbines offer promising solutions for sustainable energy demand. Since wind turbines operate in an open environment, their efficiency depends on environmental conditions. Hazard environmental conditions, such as icing, rainfall, hailstorms, dust or sand, insects’ collisions, increased humidity, and sea spray, result in degraded aerodynamic characteristics. The outcome of most studies has been that the airfoils’ lift is degraded, and at the same time, drag is increased when wind turbines operate under these conditions. The objective of this review is to improve our comprehension of these crucial aspects so they are taken into account when designing wind turbine blades, and it offers suggestions for future research paths. It serves as a valuable resource that can inspire researchers who are dedicated to enhancing the aerodynamic characteristics of horizontal axis wind turbines.

Multiobjective Optimization Study On the Aerodynamic Performance and Anti-Erosion Characteristics of a Single-Stage Dusty Flue Gas Turbine

Abstract Solid particle erosion of dusty energy recovery turbine blades has a great impact on the operating economics and safety of the unit. To mitigate the erosion of blade and improve the aerodynamic performance of the turbine, a multiobjective optimization method for turbine cascade based on the experimental design method, genetic algorithm and CFD multiphase flow simulation was developed. The optimization results show that the number of stator and rotor blades and the trailing edge angle at 50% blade span are the main parameters affecting the efficiency and blade erosion of the dusty turbine. By reducing the number of stator blades and the circumferential bending angle of the stator trailing edge, the impingement velocity and impingement probability of particles impinging on the stator trailing edge decrease by 7.5%~16.8% and 8.9%~46.2%, respectively. Additionally, compared with the original design, the flow separation loss and secondary flow intensity of the rotor cascade are suppressed by adjusting the load distribution and inlet attack angle of the rotor; thus, the turbine efficiency effectively improves by 2.28%. Meanwhile, the optimized blade reduces the particle impingement velocity and probability on the rotor leading edge, and the erosion condition of the rotor leading edge decreases by 70%.

Experimental and numerical investigations on the performance and wake characteristics of a tidal turbine under yaw

This paper presents an extensive examination of the wake characteristics and hydrodynamic performance of a 1:60 scale horizontal axis tidal stream turbine under yawed inflow conditions. Experimental investigations were conducted in a laboratory flume, while numerical simulations utilized the actuator line method and large-eddy simulation technique. The turbine was subjected to an inflow turbulence intensity of 6% and was tested at five different yaw angles (5°, 10°, 15°, 20°, and 30°). The findings demonstrate a substantial reduction in the power coefficient as the yaw angle increases, with a notable drop of 47.1% recorded at a yaw angle of 30°. Furthermore, numerical simulations of wake characteristics, including mean velocity and turbulence intensity, were examined and compared with measurements, yielding satisfactory agreement. The yawed wake flow exhibited asymmetrical distributions of mean velocity and deviations from the centerline. Additionally, distinct deformations of the yawed wake in the y-z cross sections were observed, indicating a discernible curled kidney shape that intensified with larger yaw angles. Moreover, interactions between the turbine wake and support structures affected the width and turbulence intensity of the near wake, introducing additional unsteadiness that accelerated wake recovery.

Optimal combined wake and active power control of large‐scale wind farm considering available power

AbstractThe high‐order nonlinear complex characteristics of traditional static wake model (SWM) restrict the fast optimization of wake effect. Therefore, this paper introduces a dynamic wake model (DWM) to describe the time‐varying wake characteristics of wind turbines (WTs) with low computational cost. The traditional SWM is linearized to derive the wake wind speed sensitivity coefficients, which represents the sensitivity of wake wind speed deficit with respect to the active power reference. Considering the natural propagation characteristics of wake effect, a wake delay function is added to realize the future wind speed prediction of different locations of the wind farm. And a joint control strategy of wake and active power based on model predictive control (MPC) is proposed to optimize the power contribution of each WT to minimize wake effects, and maximize total available power. Thus, the increased available power is able to satisfy the power demand from Transmission System Operator (TSO) for ancillary services and enhance power support capability. The control performance of the proposed control strategy is evaluated by simulations under constant and varying incoming wind speed.

Evaluation of the Influence of Upstream Flow on the Energy Characteristics of a Giant Kaplan Turbine

For the giant Kaplan turbine, the reservoir dam and the retaining dam can affect the internal flow characteristics of the turbine and alter its hydraulic performance. Different heads and flows have different characteristics at the inlet of the turbine. This article conducts a numerical study on the upstream reservoir of a giant Kaplan turbine using the Volume of Fluid (VOF) method and predicts the impact of the upstream reservoir on the unit flow, efficiency, and output. After considering the impact of the upstream reservoir area, due to the uneven distribution of flow in the upstream reservoir area, the efficiency of the three units under the same water level and inflow conditions has a consistent trend with the ideal situation as the unit flow rate of the units changes, and some units have higher efficiency curves than the ideal situation. However, some units are affected by the diversion wall, resulting in streamline deviation, and their efficiency curve is lower than the ideal situation. The output also has a similar situation, especially when the upstream water level is low, the output significantly decreases.

Modelling the impacts of a large marine turbine array in the Cozumel Channel

Ocean renewable energies are a promising alternative to meet the growing energy demand. Due to the intense, persistent and relatively constant unidirectional flow, the Cozumel Channel (CC) in the Caribbean Sea is considered one of the most favorable global sites for the potential exploitation of ocean current energy. In this paper we use the Regional Ocean Modelling System (ROMS) to simulate the effects of a large number of individual turbines (5277) on the marine environment at a regional scale. A couple of two-way nested grids were used to extend the horizontal resolution from 30 m to ∼3600 m. The impacts of the turbines on circulation, water temperature, sea surface high (SSH), sediment transport and upwelling events, were analyzed. An improved estimate of the average power generated was also performed, which includes the disruption of the currents by the turbines. The results suggest that the installation of a large number of marine turbines would cause severe flow disturbances in the CC and neighboring regions, changing several aspects of the ecosystem. While the number and characteristics of the marine turbines might seem excessive, this study could serve as a benchmark to determine thresholds in the size of future turbine farms in the region.

Wind tunnel experimental study on static aerodynamic performance of SB-VAWT without intermediate support axes

Wind power generation is considered an effective way for ships to harness wind energy, and the aerodynamic characteristics of wind turbines determine wind energy utilization and efficiency. However, traditional vertical axis wind turbines have intermediate shafts and support rods, which result in large negative effects in the research of the wind turbine aerodynamic characteristics. To address this issue, a Straight-Bladed Vertical Axis Wind Turbine (SB-VAWT) without intermediate support axes is proposed. The turbine can flexibly change the number of blades, rotor diameter, and installation position of blades. The static aerodynamic performance of the wind turbine with different combinations was tested in a wind tunnel laboratory at 10 m/s. The results show that the radius of the wind turbine has a greater effect on the drag coefficient for the same number of blades, with an inverse relationship between the drag coefficient and radius, and a positive association between lift coefficient, static torque coefficient, and radius. The drag coefficient is proportional to the number of blades at the same radius, while the static torque coefficient is inversely proportional to the number of blades. According to the results, placing the initial location in the azimuth range between 30° and 50° can obtain the maximum initial starting torque. Moreover, a wind turbine with a radius of 16 cm can achieve a higher average torque. Changes in the number of blades can significantly impact turbine properties, resulting in wind turbines with distinct features.

Power maximization control of small wind system using permanent magnet synchronous generator

This article describes modeling and simulations to determine a method for the power performance evaluation of autonomous wind turbine system with this simple load scheme. The method applies to small systems equipped with a permanent magnet generator in the wind turbine a diode rectifier, boost converter and batteries. In this work, the aerodynamic characteristics of wind turbines and the power conversion system topology are explained. The maximum power tracking of the wind turbine generator system using the Matlab software is presented and its results show, at least in principle, that the maximum power tracking algorithm developed is suitable for wind turbine generation systems.

Numerical analysis on the torque characteristics of hybrid hydrokinetic turbine for different configurations and operating conditions

A hybrid hydrokinetic turbine can become an efficient converter to harness the untapped hydrokinetic energy of small-scale hydro potentials sites such as canals and rivers, determining the optimal performance parameters becomes necessary. As the torque of a hydrokinetic turbine is considered one of the important performance parameters, an extensive numerical investigation has been carried out to analyse the torque characteristics of a hybrid HKT having a different value of radius ratio and attachment angle operated under different RPM and flow velocity. Under the present study, CFD analysis of four different configurations of hybrid hydrokinetic turbines covering the range of radius ratio from 0.2 to 0.8 and attachment angle from 30° to 150° have been carried out. A URANS with the conjunction of RNG k-ε has been exercised to accomplish the objectives of the present investigation. Based on the numerical results, the best configuration is found to have an optimum radius ratio value and attachment angle obtained as 0.4 and 90°, respectively. For the best-configured hybrid HKT, the average torque developed is improved by 51%, 20%, 19%, 6% and 24% compared to other hybrid configurations, corresponding to a TSR of 0.9 and Reynolds number of 1.12 × 105. The self-starting characteristics of the hybrid configuration with a 0.4 radius ratio and 90° attachment angle are better than the other considered hybrid configurations. Further, the instantaneous torque developed by the hybrid configuration with a 0.4 radius ratio and 90° attachment angle was found to be positive at each rotor angle during one cycle of revolution. Moreover, the least rate of torque pulsation is found for the hybrid HKTs operated at low RPM and Reynolds number.