Maximum Turbine Efficiency Research Articles

Pre-matching study of the natural gas engine turbocharging system based on the coupling of experiments and numerical simulation

In this study, a pre-matching method was developed based on measured performance parameters and theoretical calculations of turbochargers. First, the turbocharger of a natural gas engine was subjected to a comprehensive performance experiment. According to the experimental results, the maximum efficiencies of the turbine and compressor are 70% and 75%, respectively, and the efficiency of the turbine drops sharply from 70% to 56.6% as the pressure ratio increases from 1.25 to 2.4. In this thesis, a specific turbocharger pre-matching software has been developed in conjunction with a database. Three turbines and three compressors were selected from the self-developed database for matching and comparative study using this method. The simulation results showed that the maximum efficiency of turbine #1, #2 and #3 is 71.3%, 72.2% and 72.7%, respectively, and the efficiency of these three turbines is concentrated between 65% and 72.5%. Obviously, the maximum efficiency of the turbine has increased by 1.3–2.7% and the overall efficiency has improved after the pre-matching. Therefore, this developed pre-matching method can reduce time cost, improve work efficiency and engine performance, and is important for the design and development of turbochargers.

Performance Analysis of the Archimedes Double Screw Turbine as a Micro Hydro Power Plant with Varying Flow Rate

Samadua is an area in South Aceh Regency which has a lot of water energy potential to be used as energy to drive water turbines. The potential for water energy, it is necessary to develop renewable energy power technology, namely micro hydro power plants that can be utilized by the community. The type of water turbine that is suitable for application in the area that have water potential with low head and discharge is the Archimedes Double Screw Turbine. The Archimedes double screw turbine is a type of turbine that capable of operating with a low head of 1-15 m in river flows and irrigation and has the advantage of being environmentally friendly. The aim of this research is to design and manufacture an Archimedes Double Screw turbine that is appropriate and in accordance with the real conditions in the stream of Samadua river, -South Aceh, then analyze the influence and determine the torque ratio on the performance of the Archimedes Double Screw Turbine by measuring rotation speed, torque, power and efficiency based on variations in river flow rate. The Archimedes Double Screw turbine is made from 201 stainless steel which has dimensions of N = 2 blades (= 260 mm, = 140 mm) with a pitch of 2Ro, turbine length (L = 2 m), head = 1 m, angle θ = 300. The variables measured and observed are turbine rotation, torque, and flow rate. Tests were carried out on 3 variations of flow discharge, namely 0.02 m3/s, 0.009 m3/s, and 0.003 m3/s. The test results showed that the highest turbine rotation and power occurred at a flow rate of 0.02 m3/s of 292.10 rpm and 122.20 watts and the maximum turbine efficiency was 62%. Thus, the turbine with maximum power is obtained when the flow rate is 0.02 m3/s, while the turbine with maximum efficiency is obtained when the flow rate is 0.02 m3/s. For the numerical simulation results, the optimum pressure distribution value is 4.873 kPa and the minimum is 0.1536 kPa, so the comparison of the experimental results with the numerical simulation is that the numerical simulation optimum torque value is 2.50 N/m and the experimental optimum torque value is 2.00 N /m.

Geometrical Optimization of Pelton Turbine Buckets for Enhancing Overall Efficiency by Using a Parametric Model—A Case Study: Hydroelectric Power Plant “Illuchi N2” from Ecuador

In Ecuador, the implementation of hydroelectric power plants has had a remarkable growth in the energy sector due to its high efficiency, low environmental impact, and opportunities to generate employment. One of the sectors with the greatest benefits from this type of energy has been the rural sector, where several small-scale hydroelectric plants (0.5 MW–10 MW) have been installed, usually with Pelton turbines. Although these turbines are highly efficient, one of the challenges is to obtain the optimal geometry of the bucket to take advantage of the greatest amount of energy from the water, avoiding the separation of the fluid. In this context, this study focuses on the development of an analytical and iterative methodology that allows for the determining of the appropriate dimensions of the buckets to achieve maximum turbine efficiency. For that, a parametric model has been proposed considering the dimensions and main angles of the bucket, the net hydraulic head and the working flow, as well as the power losses. The results of the model have been validated by means of CFD and by contrasting the experimental data obtained from the “Illuchi N2” Hydroelectric Power Plant in Ecuador, and it is concluded that it is possible to improve the turbine efficiency by up to 4%.

Influence of Geometric Parameters for a 100 kW Inward Flow Radial Supercritical CO2 Turbine

Abstract Highly compact and efficient design makes inward flow radial (IFR) turbine a preferred choice for kilowatt scale supercritical CO2 (sCO2) power blocks. The influence of geometric design parameters on sCO2 turbine performance differs from gas turbines because of their small size, high rotational speeds, and lower viscous losses. The paper presents a computational fluid dynamics (CFD) study for a 100 kW IFR turbine to arrive at optimal geometric design parameters—axial length, outlet-to-inlet radius ratio, number of rotor blades, and velocity ratio, and understand their influence on the turbine's performance. The results are compared with well-established gas turbine correlations in the specific speed range of 0.2 to 0.8 to understand the implications on sCO2 IFR turbines. The analysis shows significant variations in the optimal values of design parameters when compared with gas turbines. It is found that sCO2 turbines require fewer blades and higher velocity ratios for optimal performance. The maximum turbine efficiency (∼82%) is achieved at a lower specific speed of ∼0.4 compared to a gas turbine with specific speed varying between 0.55 and 0.65. Additionally, higher negative incidence angles in the range of −50 deg to −55 deg are required at high specific speeds to counter the Coriolis effect in the rotor passage. The paper presents the variation of stator, rotor, and exit kinetic energy losses with specific speeds. The cumulative losses are found to be minimum at the specific speed of ∼0.4.

Experimental investigation for suction slots of wells turbine and shapes of point absorber

When it comes to reducing carbon emissions, A dependable source of renewable energy is wave energy. The endless energy crisis offers a multitude of potential solutions, including wave energy. Since there are no emissions, it is energy that is good for the environment. As a renewable energy source, it is frequently used at all times. To test the effectiveness of the Wells turbine, suction slits have been used on the turbine blades in this work. The aerofoil utilized in the Wells turbine blade was NACA015. An arrangement for comparing various body types is made in the experimental buoy setup. To engage with wave motion, the setup includes a buoy that floats in the lab. Results indicated that the three slots had good pressure drop coefficient behavior, good turbine coefficient, and maximum turbine efficiency. The buoy shapes (5) and (3) for the point absorber exhibited the best properties according to the relevant parameters.

Investigation of blade design parameters for performance improvement of hydraulic cross flow turbine

Micro hydro power plant offers the cheapest renewable as well as a clean energy resource having abundant room for development. Cross flow turbine is easy to manufacture and maintain, operable in off-grid remote areas with negligible civil work requirement leading to its high popularity in developing countries. The present study numerically investigates the effect of different blade design parameters on the performance of hydraulic cross flow turbine using Ansys-CFX®. Firstly, a comparative analysis of the full turbine and half turbine model is performed. Then, the blade leading and trailing edge is varied considering four distinct geometric profiles with varying rotational speeds of 100–240 rpm. Moreover, the blade exit angle is varied from 50° to 100°, keeping a consistent rotational speed of 180 rpm. The results are presented in terms of the torque generated, and the turbine efficiency. In addition, the localized flow around the blades is elaborated using the flow velocity contours and streamlines. The geometric combination with a circular profile for the blade leading edge followed by a sharp trailing edge transpired maximum turbine efficiency. Moreover, the optimal blade exit angle lies between 55° and 60° contrary to the general practice of radial exit.

Influence of Casing Shape on the Flow Field in Cross-flow Turbine with a Guide Wall and Cavity

Many run-off river types and small hydropower stations use Cross-flow turbines because of their excellent partial load characteristics and low manufacturing cost. But the maximum turbine efficiency is not high, so there have been many studies to improve the turbine performance. The authors have been developing a new shape cross-flow turbine with a cylindrical cavity and a guide wall to enhance the performance by controlling the runner outflow. Previous research has shown that the cavity effectively reduces pressure fluctuation at the nozzle's bottom tip and improves turbine efficiency. However, the mechanism is not fully understood. Therefore, the purpose of this study is to elucidate the mechanism of the cavity. The authors investigate how the flow pattern and turbine performance change with the flow pattern inside the cavity. It is clarified that the swirling flow in the cavity improves the turbine efficiency and suppresses pressure fluctuations at the lower end of the nozzle.

Study on the effects of runner geometries on the performance of inline cross-flow turbine used in water pipelines

To supply continuous and reliable power to the water monitoring systems and motorized control valves in urban water supply networks, the inline cross-flow turbine has been developed. This study aims to investigate the effects of different runner geometries on the performance of inline cross-flow turbines and to determine the optimal runner geometrical parameters. In this paper, a theoretical analysis of the working mechanism of a cross-flow runner is first performed to study the impacts of the runner geometry on turbine performance. Thereafter, several turbine models with different runner geometries are built and simulated to analyse the output power, water head reduction and torque generation at each runner stage. The results indicate that a good match between the flow inlet angle and blade outer angle notably enhances the turbine performance. Based on the results, the recommended optimal blade outer angle in this research is 30°. In addition, the results also show that the runner diameter ratio has a major impact on torque generation at the runner first stage. A lower runner diameter ratio leads to a higher output power, but the water head reduction is also higher. Based on the results, the suggested runner diameter ratio is 0.68. A numerical study on the number of blades indicates that when the number of blades increases from 20 to 24, the turbine output power considerably rises, and the maximum output power reaches 2285 W. However, if the blade number is further increased, the variation in output power is very slight. Thus, the proposed optimal blade number is 24. Based on the research results, the maximum turbine efficiency can reach 50.9% after runner optimization.

Blade Shape Analysis on The Performance of The Pelton Turbine Prototype

Water turbine is one of the driving machines where the working fluid is water that is used directly to spin the turbine runner. This research was conducted using a pelton type water turbine installastion with variations In the shape of the turbine blade. The research method used is an experimental method with a laboratory scale experimental design as well as the results of the design of this water turbine used as a practical tool for students majoring in mechanical engineering. The results showed the influence of turbine blade shape on the performance of the pelton water turbine prototype, so it can be concluded that the maximum tangential velocity is 12.141 rad/s, the hydraulic power value is 2.64 Watts, the kinetic power value is 3.886 Watts, maximum turbine power 99.141 Watts, maximum electric generator power 99.141 Watts, maximum turbine efficiency 25.512 %, and maximum electric generator efficiency 0.661 %.

An insight into the similarity approach to predict the maximum efficiency of organic Rankine cycle turbines

This work deals with the prediction of the maximum efficiency achievable by turbines for Organic Rankine Cycle (ORC) systems by means of similarity principles. At present, this is a key topic in the preliminary design optimization procedures of these systems. The dimensional analysis applied to the most general ORC turbines scenario helps obtain the functional relationship between maximum turbine efficiency and the most relevant design variables within the general framework of the flow similarity.Aim of the work is to search for the less wide and more convenient set of independent similarity parameters to increase the accuracy of turbine efficiency data in the optimization of ORC systems.Results show that the strict flow similarity does not hold if the same design is used for different working fluids, because real gas compressibility effects cannot be disregarded for most of the fluids usually adopted in ORC systems.On the other hand, a “quasi-similarity” approach can be applied to the design of low volume expansion ratios ORC turbines using the size parameter (SP), volume expansion ratio (VR) and the compressibility factor (Z) as predictors of turbine efficiency. Accordingly, two original correlations for the SP-VR-Z map of optimized axial turbine stages are suggested.

Design and Performance of Archimedes Single Screw Turbine as Micro Hydro Power Plant with Flow Rate Debit Variations (Case Study in Air Dingin, Samadua - South Aceh)

Renewable energy is energy derived from nature and can be produced continuously such as water energy as a micro hydropower plant. The development of a micro hydropower plant is to utilize the potential energy of water flow that has a certain head and discharge to be converted by turbines and generators into energy electricity that can be used in the development of Archimedes Single Screw Turbines. Archimedes Single Screw Turbine is a type of turbine that is capable of operating with low head 1-15 meter in river flow and irrigation. Aceh is one of the regions that have a large amount of water energy potential to be used as energy driving water turbines. The purpose of this study is to design, make Turbine Archimedes Single Screw construction and conduct turbine testing and determine the performance of Archimedes Single Screw Turbine based on the effect of water flow discharge on rotation, torque, power, and optimum efficiency so that it can determine the right turbine design and performance well. Archimedes Single Screw turbine is made with 201 stainless steel which has dimensions of N = 1 blade (Ro= 130 mm, Ri = 70 mm) with pitch 2Ro, Turbine length (L = 2 m), head = 1 m, Angle θ = 300. The variables measured and observed are the rotation of the turbine, torque, and flow rate. Tests were carried out on 3 variations of flow rate, namely 0.02 m3/s, 0.009 m3/s, and 0.003 m3/s. The test results, the highest rotation, and turbine power occur at flowrate 0.02 m3/s at 236.40 rpm with a power of 116.10 watts and maximum turbine efficiency is 57%. Thus, the turbine with maximum power and efficiency is obtained when the flow rate is 0.02 m3 /s.

Hydrodynamic loadings on a horizontal axis tidal turbine prototype

Until recently tidal stream turbine design has been carried out mainly by experimental prototype testing aiming at maximum turbine efficiency. The harsh and highly turbulent environments in which tidal stream turbines operate in poses a design challenge mainly with regards to survivability of the turbine owing to the fact that tidal turbines are exposed to significant intermittent hydrodynamic loads. Credible numerical models can be used as a complement to experiments during the design process of tidal stream turbines. They can provide insights into the hydrodynamics, predict tidal turbine performance and clarify their fluid–structure interaction as well as quantify the hydrodynamic loadings on the rotor. The latter can lead to design enhancements aiming at increased robustness and survivability of the turbine. Physical experiments and complementary large-eddy simulations of flow around a horizontal axis tidal turbine rotor are presented. The goal is to provide details of the hydrodynamics around the rotor, the performance of the turbine and acting hydrodynamic forces on the rotor blades. The simulation results are first compared with the experimental and good agreement between measured and simulated coefficients of power are obtained. Acting bending and torsional moment coefficients on the blade-hub junction are computed for idealised flow conditions. Finally, realistic environmental turbulence is added to the inflow and its impact on the turbine’s performance, hydrodynamics and rotor loadings is quantified.

ANALISIS DAYA DAN EFISIENSI TURBIN AIR KINETIS AKIBAT PERUBAHAN PUTARAN RUNNER

Research has been conducted about change power and efficiency on turbine. Manufacture of turbine singer aims to determine the magnitude of the reviews on power output and efficiency due to the rotation of the turbine runner. Turbine runner done with variation 90 rpm, 70 rpm, 50 rpm, 30 rpm and 10 rpm. Of the various rounds of runner that shows the maximum power change occurred on lap 50 rpm, 70 rpm and 90 rpm. Maximum power lead to speed with discharge runners 70 rpm flow 0.0078 m3 / s at 4,572 watts. Power generated minumum on debit 0.0078 m3 / s occurred on speed runner 90 rpm of 3,674 watts. Maximum turbine efficiency occurs debit on flow 0.0078 m3/s and 70 rpm with a value of 28.342%, and then declined in round 50 rpm amounted to 24.477% and the lowest in round 90 rpm amounted to 23.189%. From the calculation of the efficiency obtained maximum value is obtained at a speed of 70 rpm with a flow runner debit 0.0078 m3 / s. Key words: power, efficiency, kinetic turbines

二相ノズルおよびタービンに関する研究

Low temperature thermal energy included in hot spring or waste-heat at factories has been abandoned until now. It is reported that geothermal heat of up to 120 degrees corresponds to the energy of 7.4GW. Among them, a new technology that attempts to recover the thermal energy by driving turbine with two-phase flow which is generated by flashing hot water has been developed. The high momentum and low velocity two-phase flow drives the turbine at synchronous speed to the generator. This eliminates the need for the expensive gearbox required for the conventional steam turbine systems and thereby improves the reliability and reduces the maintenance. However, the improvement of efficiency and stability is required to put to the practical use. Therefore, the basic experiment to understand the performance of two-phase turbine and flashing nozzle was conducted and discussed by using water instead of organic fluid. Water is expected to be used to prevent the environmental destruction. The visualization of two-phase flow at the nozzle exit was conducted and the power output of two-phase turbine was measured. The experimental and analytical results showed that: (1) the non-equilibrium degree changed from nozzle throat to exit.; (2) steel wool in the convergent part of nozzle could effectively reduce the non-equilibrium and suppressed the pulsation of two-phase jet; (3) the practical two-phase jet velocity was obtained from the maximum turbine efficiency and compared with the prediction with non-equilibrium model.

Control Strategy of an Impulse Turbine for an Oscillating Water Column-Wave Energy Converter in Time-Domain Using Lyapunov Stability Method

We present two control strategies for an oscillating water column-wave energy converter (OWC-WEC) in the time domain. We consider a fixed OWC-WEC on the open sea with an impulse turbine module. This system mainly consists of a chamber, turbine and electric generator. For the time domain analysis, all of the conversion stages considering mutualities among them should be analyzed based on the Newtonian mechanics. According to the analysis of Newtonian mechanics, the hydrodynamics of wave energy absorption in the chamber and the turbine aerodynamic performance are directly coupled and share the internal air pressure term via the incompressible air assumption. The turbine aerodynamics and the dynamics of the electric generator are connected by torque load through the rotor shaft, which depends on an electric terminal load that acts as a control input. The proposed control strategies are an instant maximum turbine efficiency tracking control and a constant angular velocity of the turbine rotor control methods. Both are derived by Lyapunov stability analysis. Numerical simulations are carried out under irregular waves with various heights and periods in the time domain, and the results with the controllers are analyzed. We then compare these results with simulations carried out in the absence of the control strategy in order to prove the performance of the controllers.

Design optimization of partial admission axial turbine for ORC service

An analysis of the application of a single stage partial admission axial turbine in organic Rankine cycle is presented. The cycle is utilized to recover the heat rejected by an internal combustion engine. The selected fluid is R245fa, whose real gas behavior is relevant under the studied conditions, as modeled by the Redlich–Kwong–Soave equation of state. A loss model for the flow through the axial blades is proposed in this work based on the boundary layer theory, the concept of diffusion factor, wind tunnel cascade tests available in literature and the conservation equations for compressible flow. The basic geometry and dimensions needed to achieve maximum turbine efficiency are determined under several subcritical and supercritical cycle conditions by means of a restrained design optimization algorithm. The single stage turbine preliminary design is shown to be greatly influenced by media compressibility and the use of convergent-divergent profiled nozzles is promising to achieve the highest possible performance potential, especially at high evaporator pressure conditions.

A vertical axis hydrodynamic turbine with flexible foils, passive pitching, and low tip speed ratio achieves near constant RPM

A full-scale vertical axis turbine with flexible foil blades and a passive spring-loaded pitching mechanism was tested in the Glomma River in Norway, demonstrating a maximum turbine efficiency of 37% (0.79 m/s, 3.7 RPM), 25% (1.18 m/s, 4.2 RPM), and 20% (1.55 m/s, 4.7 RPM). The turbine rotational speed showed a limited revolutions per minute (RPM) variation (increasing by only a factor of 1.3) with a doubling of inflow speed. The turbine RPM and load variations were controlled using five wings, double-cambered morphing blades with a relatively high blade lift/drag ratio over a wide range of angle of attacks, and passive spring-controlled blade pitching. The inherent passive blade pitching demonstrated a distinct flopping motion around the nominal (non-pitched) position at ∼0° azimuth angle and a less distinct motion at ∼180° for each revolution around the axis. The turbine's high solidity design, morphing blades, and Knoller-Betz effect limited the RPM variations over a wide range of water velocities. The flex foil turbine had higher power coefficients at lower tip speed ratios compared to typical lower solidity turbines with fixed blades, higher tip speed ratios, and no blade pitching and/or flopping.

Nonlinear Digital Simulation Model of Hydroelectric Power Unit With Kaplan Turbine

Mathematical and simulation models enable hydroelectric power unit dynamic behavior analysis using computers. To approximate the power unit dynamics as accurate as possible, nonlinear high-order model is required. This paper describes a hydroelectric power unit with double regulated Kaplan turbine. The runners of such turbines permit the blades angle to be varied on the run depending on operating conditions. This ensures maximum turbine efficiency under all operating conditions. Detailed mathematical and digital simulation model of the hydroelectric power unit with double regulated turbine was presented for turbine control system analysis. Simulation model developed for Varazdin HPP (power unit 1) is verified by several comparisons with real measurement results.

Influence of Atmospheric Stability on Wind Turbine Power Performance Curves

The impact of atmospheric stability on vertical wind profiles is reviewed and the implications for power performance testing and site evaluation are investigated. Velocity, temperature, and turbulence intensity profiles are generated using the model presented by Sumner and Masson. This technique couples Monin-Obukhov similarity theory with an algebraic turbulence equation derived from the k-ϵ turbulence model to resolve atmospheric parameters u*, L, T*, and z0. The resulting system of nonlinear equations is solved with a Newton-Raphson algorithm. The disk-averaged wind speed u¯disk is then evaluated by numerically integrating the resulting velocity profile over the swept area of the rotor. Power performance and annual energy production (AEP) calculations for a Vestas Windane-34 turbine from a wind farm in Delabole, England, are carried out using both disk-averaged and hub height wind speeds. Although the power curves generated with each wind speed definition show only slight differences, there is an appreciable impact on the measured maximum turbine efficiency. Furthermore, when the Weibull parameters for the site are recalculated using u¯disk, the AEP prediction using the modified parameters falls by nearly 5% compared to current methods. The IEC assumption that the hub height wind speed can be considered representative tends to underestimate maximum turbine efficiency. When this assumption is further applied to energy predictions, it appears that the tendency is to overestimate the site potential.

Solar chimney turbine characteristics

A typical layout of a solar chimney power plant has a single axial turbine with radial inflow through inlet guide vanes at the base of the chimney. Turbine efficiency depends on the turbine blade row and turbine diffuser loss coefficients. The paper presents analytical equations in terms of turbine flow and load coefficient and degree of reaction, to express the influence of each coefficient on turbine efficiency. It finds analytical solutions for optimum degree of reaction, maximum turbine efficiency for required power and maximum efficiency for constrained turbine size. Characteristics measured on a 720 mm diameter turbine model confirm the validity of the analytical model. Application to a proposed large solar chimney plant indicates that a peak turbine total-to-total efficiency of around 90% is attainable, but not necessarily over the full range of plant operating points.