Performance Characteristics Of Turbine Research Articles

A New Approach of Gas Turbine Component Matching for Electrical Power Generation

Gas turbines are often required to operate at different power levels and under varying environmental conditions. But by the nature of the thermodynamic processes in the engine, it is not possible to obtain the same level of efficiency within the entire range of operation. Therefore, depending on the particular application, for example for power generation, the rotational speed would be constant and dictated by the electrical generating machine. Gas turbine engine consists of various components which are linked together in such a way that there exists a mechanical and thermodynamic interdependence among some components. This means that some operational compatibility (matching) between components will be required for a steady state or equilibrium operation. The steady state of gas turbine engine for power generation can be achieved by the matching of its compressor and turbine. The usual approach of matching the compressor and the turbine is usually based on using an iterative procedure to determine the turbine operating points which are then plotted on the compressor characteristics. The draw back of this process is being laborious and time consuming. The new approach developed overcomes this by superimposing the turbine performance characteristics on the compressor performance characteristics while meeting the components matching conditions. This can be done by introducing a new mass flow dimensionless parameter. Superimposing the turbine map on the compressor map cannot be totally accepted until both maps axes (the abscissa and the ordinate) are identical. This paper explains the new approach adopted to a single shaft gas turbine engine. Theoretically, the developed techniques can be applied to other gas turbine engines.

Turbin angin poros vertikal tipe Savonius bertingkat dengan variasi posisi sudut

Wind turbine is a technology that converts wind energy to electric power. A Savonius type rotor blade is a simple wind turbine that operates on the concept of drag. The turbine has a potential to be developed as it has a simple construction and it is suitable for low wind speeds. Savonius rotor can be designed with two or three blades in single level or multi-levels. This research was conducted to obtain two levels wind turbine performance characteristics with variations in wind speed and different positions of angle on each level. The variations of the angle position of the wind turbine were 0°, 30°, 45°, 60°, and 90° in each stage. The result shows that the performance of the wind turbine is inversely to the degree of the angle position. The maximum rotation speed of the rotor was about 150.6 rpm that was generated at the wind speed of 5 m/s and the angle position of 0°.

The influence of turbulence model and two and three-dimensional domain selection on the simulated performance characteristics of vertical axis tidal turbines

The influence of Computational Fluid Dynamics (CFD) modeling techniques on the accuracy of fixed pitch vertical axis turbine power output predictions was investigated. Using Two-Dimensional (2D) and Three-Dimensional (3D) models, as well as the Baseline-Reynolds Stress Model (BSL-RSM) and the k-ω Shear Stress Transport (k-ω SST) model in its fully turbulent and laminar-to-turbulent formulation, differences in power output modeling accuracy were evaluated against experimental results from literature. The highest correlation was found using a 3D domain model that fully resolved the boundary layer combined with the k-ω SST laminar-to-turbulent model. The turbulent 3D fully resolved boundary layer k-ω SST model also accurately predicted power output for most rotational rates, at a significantly reduced computational cost when compared to its laminar-to-turbulent formulation. The 3D fully resolved BSL-RSM model and 3D wall function boundary layer k-ω SST model were found to poorly simulate power output. Poor output predictions were also obtained using 2D domain k-ω SST models, as they were unable to account for blade tip and strut effects. The authors suggest that 3D domain fully turbulent k-ω SST models with fully resolved boundary layer meshes are used for predicting turbine power output given their accuracy and computational efficiency.

Performance characteristics of a horizontal axis turbine with fusion winglet

Any technique or method that can improve the efficiency in exploiting renewable wind or marine current energy has got a great significance today. It has been reported that adding a winglet at the tip of the rotor blades on a horizontal axis wind turbine can increase its power performance. The purpose of this paper is to adopt a numerical method to investigate the effects of different winglet configurations on turbine performance, especially focusing on the direction for the winglet tip to point towards (the suction side, pressure side or both sides of the main blade). The results show that the new design of an integrated fusion winglet proposed in this paper can generally improve the main blade's power producing ability, which is further enhanced with the increase of turbine's tip speed ratio with a maximum power augmentation of about 3.96%. No matter which direction the winglet tip faces, the installation angle of the winglet should match well with the real angle of incoming flow. As a whole, the turbine with winglet of two tips facing to both sides of the main blade can produce much more power than the one of winglet configuration whose tip faces only one side for different blade hub pitch angles and vast majority of tip speed ratios. The working principle behind the winglet in improving turbine performance may be that it can block the downwash fluid easily flowing around the tip section of the main blade from the pressure side to suction side, and hence diffuse and spread out the tip vortex. As a result, it finally decreases the energy loss. Besides, the relative projected rotor area in incoming flow direction will also be reduced due to the addition of the winglet, which is also helpful to turbine's power coefficient.

Gas-particle flows and erosion characteristic of large capacity dry top gas pressure recovery turbine

Based on the erosion rate model and the particle rebound model of blade material obtained through accelerated erosion test under high temperature, systematic numerical simulations of the complex gas-particle flows in inlet volute and cascade of a large capacity gas pressure recovery turbine are performed in this paper. The influence of inlet volute structure and cascade channel structure on the aerodynamic performance and erosion characteristics of turbine is first investigated. Results show that although mixing flows and vortex flows are formed in turbine intake volute, total pressure loss of volute is less than 0.7% because of low gas velocity. Erosion damage on the trailing edge of nozzles and rotating blades is mainly caused by high-speed cutting behavior of ash particles. The typical inlet volute structure results in an uneven erosion of first stage nozzles along circumferential direction. Nozzles located below the horizontal split are mainly eroded in blade root area, while erosion distribution of nozzles located above the horizontal split is irregular, and worse than the erosion degree of the lower half circle. Flow acceleration characteristics and cascade circumferential structure must be comprehensively considered so as to simultaneously improve the aerodynamic and anti-erosion performance of turbine.

Computational studies on small wind turbine performance characteristics

To optimize the selection of suitable airfoils for small wind turbine applications, computational investigation on aerodynamic characteristics of low Re airfoils MID321a, MID321d, SG6040, SG6041, SG6042 and SG6043 are carried out for the Reynolds number range of (0.5- 2)×105. The BEM method is used to determine the power coefficient of the rotor from the airfoil characteristics; in addition, the blade parameters like chord and twist are also determined. The newly designed MID321a airfoil shows better aerodynamic performance and maximum power coefficient as compared with other investigated airfoils for wider operating ranges.

Performance and dynamic characteristics of a multi stages vertical axis wind turbine

Vertical axis wind turbines (VAWTs) are used to convert wind energy to mechanical output or electricity. Vertical axis wind turbines are favorable at buildings as it can receive wind from any direction, have a design that can be integrated simply with building architecture and they have better response in turbulent wind flow which is common in urban areas. Using a calculation code based on the Double Multiple Stream Tube theory, symmetrical straight-bladed NACA0012 wind turbine performance was evaluated. The induction factor for both upwind and downwind zone is determined with the aid of a root-finding algorithm. This numerical analysis highlighted how turbine performance is strongly influenced by the wind speed (Reynolds number) and rotor solidity (turbine radius and blade chord length). Also a dimensional analysis is introduced and is to be considered in such a way to generalize the design for different turbine specifications. One of the qualities provided by dimensional analysis is that geometrically similar turbines will produce the same non-dimensional results. This allows one to make comparison between different sizes wind turbines in terms of power output and other related variables. One of the main problems affecting the turbine performance and dynamics is the torque ripple phenomena. So in this paper a turbine design configuration is introduced in order to decrease the turbine torque fluctuation. This design is carried out by constructing more similar turbine units (stages) on the vertical axis on top of each other with different orientation phase angles. The results showed that using even number of turbine assembly is better than odd number to avoid torque fluctuation and mechanical vibrations acting on the turbine. Also it is preferred to use four turbine stages as the eight stages will have no sensible effect on decreasing the torque fluctuation.

Numerical investigation of the variable nozzle effect on the mixed flow turbine performance characteristics

There are various matching ways between turbocharger and engine, the variable nozzle turbine is the most significant method. The turbine design must be economic with high efficiency and large capacity over a wide range of operational conditions. These design intents are used in order to decrease thermal load and improve thermal efficiency of the engine. This paper presents an original design method of a variable nozzle vane for mixed flow turbines developed from previous experimental and numerical studies. The new device is evaluated with a numerical simulation over a wide range of rotational speeds, pressure ratios, and different vane angles. The compressible turbulent steady flow is solved using the ANSYS CFX software. The numerical results agree well with experimental data in the nozzleless configuration. In the variable nozzle case, the results show that the turbine performance characteristics are well accepted in different open positions and improved significantly in low speed regime and at low pressure ratio.

An experimental study on the aeromechanics and wake characteristics of a novel twin-rotor wind turbine in a turbulent boundary layer flow

The aeromechanic performance and wake characteristics of a novel twin-rotor wind turbine (TRWT) design, which has an extra set of smaller, auxiliary rotor blades appended in front of the main rotor, was evaluated experimentally, in comparison with those of a conventional single-rotor wind turbine (SRWT) design. The comparative study was performed in a large-scale wind tunnel with scaled TRWT and SRWT models mounted in the same incoming turbulent boundary layer flow. In addition to quantifying power outputs and the dynamic wind loadings acting on the model turbines, the wake characteristics behind the model turbines were also measured by using a particle image velocimetry system and a Cobra anemometry probe. The measurement results reveal that, while the TRWT design is capable of harnessing more wind energy from the same incoming airflow by reducing the roots losses incurred in the region near the roots of the main rotor blades, it also cause much greater dynamic wind loadings acting on the TRWT model and higher velocity deficits in the near wake behind the TRWT model, in comparison with those of the SRWT case. Due to the existence of the auxiliary rotor, more complex vortex structures were found to be generated in the wake behind the TRWT model, which greatly enhanced the turbulent mixing in the turbine wake, and caused a much faster recovery of the velocity deficits in the turbine far wake. As a result, the TRWT design was also found to enable the same downstream turbine to generate more power when sited in the wake behind the TRWT model than that in the SRWT wake, i.e., by mitigating wake losses in typical wind farm settings.

Performance and wake conditions of a rotor located in the wake of an obstacle

Obstacles like forests, ridges and hills can strongly affect the velocity profile in front of a wind turbine rotor. The present work aims at quantifying the influence of nearby located obstacles on the performance and wake characteristics of a downstream located wind turbine. Here the influence of an obstacle in the form of a cylindrical disk was investigated experimentally in a water flume. A model of a three-bladed rotor, designed using Glauert's optimum theory at a tip speed ratio λ = 5, was placed in the wake of a disk with a diameter close to the one of the rotor. The distance from the disk to the rotor was changed from 4 to 8 rotor diameters, with the vertical distance from the rotor axis varied 0.5 and 1 rotor diameters. The associated turbulent intensity of the incoming flow to the rotor changed 3 to '6% due to the influence of the disk wake. In the experiment, thrust characteristics and associated pulsations as a function of the incoming flow structures were measured by strain gauges. The flow condition in front of the rotor was measured with high temporal accuracy using LDA and power coefficients were determine as function of tip speed ratio for different obstacle positions. Furthermore, PIV measurements were carried out to study the development of the mean velocity deficit profiles of the wake behind the wind turbine model under the influence of the wake generated by the obstacle. By use of regression techniques to fit the velocity profiles it was possible to determine velocity deficits and estimate length scales of the wake attenuation.

Performance modelling for wind turbines operating in harsh conditions

This paper presents a new method of online wind turbine performance modelling (recursive parameter estimation) that addresses the nonlinearity associated with wind turbine performance characteristics. A sliding linearization algorithm is implemented to track changes in the turbine operating environment. A multivariate polynomial approximation of the turbine power coefficient is developed to produce a linear process model approximating the operating wind turbine. The estimated model parameters are recursively calculated to compensate for changes in both the turbine operating environment and the condition of the wind turbine. The algorithm models both the steady-state and dynamic wind turbine performance throughout the entire operating range, producing a continuously valid turbine linearization with applications in gain scheduling and turbine performance optimization. Copyright © 2016 John Wiley & Sons, Ltd.

Performance characteristic investigation and stay vane effect on Ns100 inline francis turbine

This study presents the performance characteristics of a small Francis turbine with an inline casing and is a continuation of a previous study. A new runner design has been implemented using the previous facility. The specific speed of the new runner has been modified from N s 80 to N s 100 m-kW-min -1 . This turbine can be installed in a city water supply system. To dissipate excess pressures in the water line system an inline-turbine can be used instead of an inline-pressure reducing valve. Thus, some of the energy can be recovered by utilizing the pressure difference. For best applicability and minimal space consumption, the turbine is designed with an inline casing instead of a common spiral casing. As a characteristic of inline casing, the flow accesses to the runner are in the radial direction, showing low efficiency. The installation of vanes improves the internal flow and positively affects the output power. In contrast to the previous study, the new runner reduces the effect of the stay vanes by maintaining a higher efficiency.

Performance characterization of a cross-flow hydrokinetic turbine in sheared inflow

A method for constructing a non-dimensional performance curve for a cross-flow hydrokinetic turbine in sheared flow is developed for a natural river site. The river flow characteristics are quasi-steady, with negligible vertical shear, persistent lateral shear, and synoptic changes dominated by long time scales (days to weeks). Performance curves developed from inflow velocities measured at individual points (randomly sampled) yield inconclusive turbine performance characteristics because of the spatial variation in mean flow. Performance curves using temporally- and spatially-averaged inflow velocities are more conclusive. The implications of sheared inflow are considered in terms of resource assessment and turbine control.

Experimental and numerical studies on the performance and surface streamlines on the blades of a horizontal-axis wind turbine

Investigating laminar separation over the turbine blade of a horizontal-axis wind turbine (HAWT) has been considered an important task to improve the aerodynamic performance of a wind turbine. To better understand the laminar separation phenomena, in this study, the aerodynamic forces of a SD8000 airfoil (representing the sectional blade shape) in the steady-state conditions were first predicted using an incompressible Reynolds-averaged Navier–Stokes solver with the γ–Reθt and k–kL–ω transition models. By comparing simulation and experimental results, the k–kL–ω transition model was chosen to simulate the laminar separation on three-dimensional (3D) turbine blade. Experimentally, a HAWT with three blades was then tested in a close-circuit wind tunnel between the tip speed ratios (TSRs) of 2 and 7 at the wind speed of 10 m/s. In addition, through computational fluid dynamics, the turbine performance and flow characteristics on the blade as blade is rotating were investigated. It is shown that 3D simulations agreed well with the experimental results with regard to the mechanical power of the HAWT at the testing TSRs. Moreover, the separation and reattachment lines on the suction surface of the turbine blade were also observed through the skin friction line, indicating that laminar separation moved toward the trailing edge with the increasing TSR at the blade tip region.

Jet quality characteristics according to nozzle shape of energy-recovery Pelton turbines in pressure-retarded osmosis

AbstractPelton turbines are used for energy recovery in pressure-retarded osmosis (PRO) systems. The quality of jet sprays is a significant factor affecting the performance of these turbines. This study examined jet quality characteristics according to the nozzle geometry of Pelton turbines. Jet quality tests were conducted to analyze the degree of similarity between the actual jet flow and the ideal jet flow. Power loss, discharge coefficients, and performance characteristics of Pelton turbines were examined with respect to the nozzle shape through performance tests of the nozzles and turbines. Furthermore, jet flows were numerically analyzed. The test results and analyses confirm that for a given input power, the recirculation region increases and the jet quality decreases with increasing nozzle throat angle. On the basis of the results, the optimum range of nozzle throat angle for Pelton turbines in PRO systems is suggested.

Physical testing of performance characteristics of a novel drag-driven vertical axis tidal stream turbine; with comparisons to a conventional Savonius

An experimental study of the performance and optimisation of a prototype novel drag-driven vertical axis tidal stream turbine is presented. The drag turbine has several unique advantages, including simple blade design, deployable in shallow waters and potential denser array spacing. Performance optimisation was conducted in the hydraulics flume at Cardiff University (CU), where the turbine reached Cpmax/λ=0.132/0.441 for its 90° phase angle configuration. The CU turbine was then tested using the wider and deeper hydraulics flume at IFREMER, France. Testing at IFREMER reduced the blockage factor from 17% at CU down to 1%; into the range of unblocked conditions. Testing in an unblocked environment, under similar flow conditions, reduced the peak efficiency of the CU turbine by 43% to Cpmax/λ=0.067/0.346. Finally the CU turbine was compared to the performance of a Savonius turbine. The design of the Savonius was based on a literature review. The CU turbine showed inferior efficiency values compared to the performance of the Savonius. The Savonius reached Cpmax/λ=0.098/0.962 in unblocked conditions, 46% greater than Cpmax of the drag turbine.

シュラウドを有する浮遊式海流発電用水車に関する研究

The environmental problem and related energy problem are recently the serious problem all over the world. The renewable energy is now highlighted as one of the solution to the problem. The possible use of ocean current as an energy resource begins to draw attention in the renewable energy. In this paper, horizontal axis ocean current turbine performance estimated by Computational Fluid Dynamics is carried out. The numerical estimation method is able to calculate not only a turbine performance characteristics but also turbine with shroud (the collection device) performance characteristics. This method is validated by comparing with experimental results.

Effect of twist angle on the performance of Savonius wind turbine

This study aimed to understand the performance and shape characteristics of a helical Savonius wind turbine at various helical angles. The power coefficient (Cp) at different tip speed ratios (TSRs) and torque coefficient (CT) at different azimuths for helical blade angles of 0°, 45°, 90°, and 135° were observed under the conditions of a constant projection area and aspect ratio. The numerical results discussed in this paper were obtained using an incompressible unsteady Reynolds average Navier–Stokes (k-ε RNG) model. A numerical analysis in the unsteady state was used to examine the flow characteristics in 1° steps from 0° to 360°. In addition, an experiment was performed at a large-scale wind tunnel, and the results were compared with those of the numerical analysis. Wind speed correction was also employed because of the blockage effect between the wind turbine and wind tunnel. Our results showed that the maximum power coefficient (Cp,max) values in both cases had similar tendencies for the TSR range considered in this study, i.e. from 0.4 to 0.8, except for the twist angle of 45°. The Cp,max occurred at the twist angle of 45°, whereas it decreased by 25.5% at 90° and 135°. Regarding the CT values at various azimuths, the results showed that the peak-to-peak values in the profiles for 90° and 135° were less than those for 0° and 45°.

Characterising a turbine for application in an organic Rankine cycle

Turbines are critical components of electricity generating low grade WHR&U (waste heat recovery and utilisation) systems, and determining the performance of the turbine is crucial to the successful implementation of these systems. In this paper, an experimental waste heat turbine kit – with the turbine rotor later replaced with an in-house designed and manufactured radial inflow turbine rotor – was sourced, assembled and tested in a designed and built test bench, using air as the working fluid. From the obtained test data, the turbine performance characteristics were determined, and plotted as turbine performance maps. The determined performance characteristics for the turbine working with air were then further used to scale the turbine for a refrigerant-123 application, thus predicting its performance for integration into an organic Rankine cycle low grade WHR&U system.

Wave–current interaction effects on tidal stream turbine performance and loading characteristics

The transient interaction between tidal currents and the rotation of a horizontal axis turbine rotor have the potential to induce high asymmetric loadings, which are subsequently transmitted to the drive shaft and potentially high speed drive train components. To mitigate the potential for early component failure, analysis of asymmetric loading on marine turbines is fundamental to the design process. To investigate these loads a turbine mounted on a circular stanchion has been used to highlight the effects of introducing more realistic boundary conditions. Depending on their wavelength, waves can also have a significant effect on the overall design decisions and placement of devices. Thrust loading and bending moments applied to the drive shaft can be of the order of hundreds of kN and kNm respectively.Knowledge of the flow regime can allow designers to evaluate material selection for components and incorporate some deformation capability of the turbine blades to increase the power output and potentially alleviate some of the stress distribution through key structural points. The resulting data can then be used to estimate component life via fatigue prediction.This paper includes a multi-physics approach to modelling tidal energy devices and the potential for modelling to inform device condition monitoring.