Power Turbine Shaft Research Articles

Artificial Neural Network Model for Estimating the Pelton Turbine Shaft Power of a Micro-Hydropower Plant under Different Operating Conditions

The optimal performance of a hydroelectric power plant depends on accurate monitoring and well-functioning sensors for data acquisition. This study proposes the use of artificial neural networks (ANNs) to estimate the Pelton turbine shaft power of a 10 kW micro-hydropower plant. In the event of a failure of the sensor measuring the torque and/or rotational speed of the Pelton turbine shaft, the synthetic turbine shaft power data generated by the ANN will allow the turbine output power to be determined. The experimental data were obtained by varying the operating conditions of the micro-hydropower plant, including the variation of the input power to the electric generator and the variation of the injector opening. These changes consequently affected the flow rate and the pressure head at the turbine inlet. The use of artificial neural networks (ANNs) was deemed appropriate due to their ability to model complex relationships between input and output variables. The ANN structure comprised five input variables, fifteen neurons in a hidden layer and an output variable estimating the Pelton turbine power. During the training phase, algorithms such as Levenberg–Marquardt (L–M), Scaled Conjugate Gradient (SCG) and Bayesian were employed. The results indicated an error of 0.39% with L–M and 7% with SCG, with the latter under high-flow and -energy consumption conditions. This study demonstrates the effectiveness of artificial neural networks (ANNs) trained with the Levenberg–Marquardt (L–M) algorithm in estimating turbine shaft power. This contributes to improved performance and decision making in the event of a torque sensor failure.

EFFECTS OF BLADE HEIGHT ON THE EFFICIENCY OF GRAVITATIONAL WATER VORTEX TURBINE

This paper presents the results of a study on the effect of blade height on the efficiency of a free-vortex water turbine. Laboratory experimentation was conducted to determine the turbine's shaft power generation and efficiency. Water turbines with six blades and four different heights (208 mm, 248 mm, 288 mm, and 320 mm) were built and tested to determine the most appropriate blade height. The turbines were tested in a conical basin with inlet and outlet diameters of 600 mm and 100 mm and a height of 800 mm, at volume flow rates of 0.0088 m³/s, 0.0105 m³/s, and 0.0108 m³/s. The results showed that the turbine with a blade height of 288 mm was the most appropriate, yielding the highest efficiency of 30.46% at a water flow rate of 0.0108 m³/s.

Performance analysis of a novel small-scale radial turbine with adjustable nozzle for ocean thermal energy conversion

Ocean thermal energy is acknowledged as one of the most promising ocean renewable energy sources in low latitude sea areas. In the ocean thermal energy conversion system, the turbine plays a significant role, and it is responsible for converting the working medium enthalpy into the shaft output power. The present study is focused on the performance analysis of a novel radial inflow turbine with an adjustable nozzle in the OTEC system in order to adapt to the changing operating conditions of the turbine, which vary with the change in seawater temperature. At the design point, the predicted overall isentropic efficiency is 86.5%, and the shaft output power is 15.3 kW, slightly higher than the expected 15 kW. Furthermore, a parametric study is performed, respectively, for the nozzle vane stagger angle and the nozzle-impeller radial clearance to explore the favorable geometric parameters for different conditions. The turbine’s overall efficiency increases slightly with deceasing nozzle-impeller radial clearance, and the variation of the nozzle vane stagger angle is much more influential on the turbine shaft power and overall efficiency. The optimum stagger angle point moves from 32° to 36° gradually with the increase in nozzle-impeller clearance. Finally, the feasibility of an adjustable nozzle for the turbine under off-design conditions was verified by combining the radial clearance and nozzle stagger angle.

Integrated Aerodynamic and Mechanical Design of a Large-Scale Axial Turbine Operating With A Supercritical Carbon Dioxide Mixture

Abstract In this paper, the design of a large-scale axial turbine operating with supercritical carbon dioxide (sCO2) blended with sulfur dioxide (SO2) is presented considering aerodynamic and mechanical design aspects as well as the integration of the whole turbine assembly. The turbine shaft power is 130 MW, designed for a 100 MWe concentrated-solar power plant with turbine inlet conditions of 239.1 bar and 700 °C, total-to-static pressure ratio of 2.94, and mass-flow rate of 822 kg/s. The aerodynamic flow path, obtained in a previous study, is first summarized before the aerodynamic performance of the turbine is evaluated using both steady-state and unsteady three-dimensional numerical models. Whole-annulus unsteady simulations are performed for the last turbine stage and the exhaust section to assess the unsteady loads on the rotor due to downstream pressure field distortion and to assess the aerodynamic losses within the diffuser and exhaust section. The potential low engine order excitation at the last rotor stage natural frequency modes due to downstream pressure distortion is assessed. The design of the turbine assembly is constrained by current manufacturing capabilities and the properties of the proposed working fluid. High-level flow-path design parameters, such as pitch diameter and number of stages, are established considering a trade-off between weight and footprint, turbine efficiency, and rotordynamics. Rotordynamic stability is assessed considering the high fluid density and related cross coupling effects. Finally, shaft end sizing, cooling system design, and the integration of dry gas seals are discussed.

Study on turbocompound system for a heavy-duty diesel engine by combining matching analysis with experiments

In this work, to improve the fuel economy of long-haul commercial vehicles, the effects of turbocompound system matching on engine performance were numerically and experimentally studied. Firstly, a 1D GT-POWER simulation model of an 11 L heavy-duty diesel engine was established and verified by the experimental data. Secondly, the performances of the turbocompound engine matching with different sizes of fixed geometry turbine (FGT) and power turbines were analyzed. It was found that the exhaust energy distribution between the turbocharger turbine and power turbine had a significant impact on engine performance, and the size of the turbocharger turbine had a more noticeable impact than the power turbine. Based on the FGT turbocompound system simulation result, an appropriate variable geometry turbocharger (VGT) and three wastegate turbochargers (WGT) were selected for further simulation and experimental research. In addition, the impacts of the transmission ratio between the power turbine shaft and the engine crankshaft, and the fuel injection timing on the engine performance were experimentally studied. The engine test result showed that the fuel economy was improved by 1.6% under European Steady State (ESC) cycle while keeping the weighted NOx emission the same as the original engine. Finally, the turbocompound engine with WGT was installed on a heavy-duty long-haul commercial vehicle for road tests. The fuel economy of the vehicle was improved by 2.54% under the 80 km/h constant speed road test.

Gas Turbine Compressor Configuration Analysis for Production and Efficiency Optimization at PT Saka Indonesia Pangkah Ltd.

Gas Turbine Compressors are used by Saka Indonesia Pangkah Ltd. in upstream oil and gas facilities either to boost hydrocarbon products to downstream facilities or to lift liquid hydrocarbon as a common artificial method. As production rate declining leads to gas supply deficiency to the compressors, the operating point move to surge line away from the best efficiency point. Gas feed shortage affecting the compressor’s performance which contributed to head and flow capacity. This condition is then calculated and simulated using UNISIM Design Simulator to get optimum configuration results. The simulation was performed at the same gas turbine shaft power output of each compressor. Two cases of centrifugal compressors configuration with different functions and performance are studied. Due to process dynamic conditions, constraint parameter is considered as per desired operating point. This paper also analyses techno-economic aspects between individual and serial pipelines arrangement of the two compressors by evaluating operational data and design calculation. Subsequently, this study produces assessment observations associated with the compressor performance both in individual and serial configuration and eventually analyses the rate of fuel consumption in the gas turbines as the main driver. The case study shows serial arrangement between MPC-1 and GLC with same gas turbine shaft power as individual configuration can reduce fuel consumption up to 47 kg/hr. It saves as much as USD 7,569.96 per day at low demand and USD 7,569.96 at high-demand cases.

An investigation into the balancing of high speed, flexible shafts by external application of compensating balancing sleeves

The paper investigates the use of compensating balancing sleeves positioned at the shaft’s end for the balancing of high-speed flexible shafts. The balancing sleeve is a new arrangement that creates a pure balancing moment with virtually zero radial reaction forces. For comparison purposes, experimental results from previous research are used to benchmark performance and to demonstrate the benefits newly proposed topology. The new configuration is commensurate with what is required for the Power Turbine (PT) shaft of a twin shaft industrial gas turbine, with an overhung disc. The study is also aimed at bladed shafts, such as those used in high speed gas turbines/compressors, with a view to improving their volumetric efficiency by reducing the formation of relatively large tip leakage gaps caused by shaft deflection/blade wear of abradable seals. It is shown to be practically possible to separate the two main dynamic balancing functions i.e. the control of bearing reaction loads and shaft deflections, thus allowing for their independent adjustment. This enables the required balancing sleeve moment to be determined and set during low-speed commissioning i.e. before any excessive shaft deflection and resulting seal wear occurs, as is typical when final balancing is undertaken at full operational speed.

Mitigation of the aerodynamic noise of small axial wind turbines - methods and experimental validation

Although the characteristic Reynolds number of small horizontal axis wind turbines is only in the order of 100,000, their noise emissions can be annoying. Three different modifications of the blades aiming at attenuating the aerodynamic noise mechanisms are investigated: (i) Optimization of the blade profile, (ii) application of boundary layer tripping and (iii) addition of serrations to the trailing edges of the blades. All modifications were designed using either a novel optimization method or state-of-the-art design rules. They were tested on a three-bladed research wind turbine with 3 m diameter, which was placed on a large flat roof of an isolated tall building. Shaft and sound power were measured during substantial time periods, statistically analyzed and compared. Depending on the type and thickness of the blade profile, both, tripping and trailing edge serrations, were found to reduce noise but always degraded the turbine shaft power. The model-based optimization of the 15 % thick baseline profile S834 resulted in a new 10 % thick profile with a novel shape of the pressure and suction sides. Blades made from this profile, without trips but with trailing edge serrations, provided the best compromise between noise reduction and degradation of the aerodynamic turbine performance.

Hybrid composite shaft of High-Speed Rotor-Bearing System - A rotor dynamics preview

In this present study, the detailed rotor dynamic evaluation of hybrid composite material rotating shaft of a power turbine high-speed rotor-bearing system is presented. The slender power turbine shaft of front driving turboshaft engine powering the rotorcraft requires a stiffer and lighter material to exhibit better rotor dynamics. Based on the preliminary investigation which predicted substantial rotor dynamic advantages, the laminated composite material shaft is proposed in the compressor section of the rotor-bearing system. To avoid the direct exposure of composite material to the harsh environment of gas turbine engine, hybrid metal fiber form of rotating shaft is employed. The hybrid metal fiber shaft is comprised of a core laminated carbon-epoxy tube sandwiched by steel tubes both inside and outside. The effect of parametric variation in the laminate and length of the hybrid shaft is evaluated and compared with the existing steel shaft. The viscoelastic material damping of carbon-epoxy laminate is also included as a rotating internal damping to evaluate the rotor dynamic instability threshold of the rotor-bearing system. From the analysis, it is found that the combination of metal and fiber-reinforced material can effectively leverage the combined strengths of both materials.

A Hydraulic Performance Comparison of Centrifugal Pump Operating in Pump and Turbine Modes

The modifications of impeller may show diverse impact on centrifugal pump operating in pump and turbine modes. To clarify this problem, the hydraulic performance of a low specific speed centrifugal pump operating in both modes was firstly obtained by CFD method and verified by experiment. Then, based on the single-factor design method, a series of calculations have been conducted to identify the effects of impeller geometry parameters on the hydraulic performance in different modes. The variations of head, shaft power and hydraulic efficiency curves with different impeller parameters were explored. It is found that compared with turbine, the pump shows a more obvious variation of head. The outlet angle has positive impact both on the head consumed by pump or generated by turbine. The change of turbine shaft power is apparently smaller than that of pump for different impeller geometry parameters. Only the outlet width somewhat changes the turbine shaft power. The hydraulic efficiency in both modes shows different variation under different impeller geometric parameters, while the hydraulic efficiency of both modes is reduced with the outlet angle increasing. Meanwhile, the response amount of hydraulic efficiency caused by certain change of impeller parameters was estimated by sensitivity analysis method. It is found that only the appropriate blade number and outlet width can improve the hydraulic performance both in pump and turbine modes. Eventually, the hydraulic loss, skin friction loss and theoretical analysis were performed to explore the reason of hydraulic performance variation due to different impeller parameters. The change of slip factor, impeller inlet area, impeller outlet area or hydraulic loss results in the change of hydraulic performance in both modes. The results can be useful for hydraulic performance improvement for both pump and turbine modes through impeller geometry modification.

Numerical analysis of wind supercharging solar chimney power plant combined with seawater desalination and gas waste heat

Performance investigation of the wind supercharging solar chimney power plant combined with seawater desalination and gas waste heat (WSCPPDW) was conducted in this study. The objective of this paper is to investigate the influence of operational and structural parameters on the WSCPPDW performance and to analyze the flow field characteristics in the WSCPPDW. The mathematical model of WSCPPDW, proposed before, could hardly reflect the effect of structural parameters and flue gas jet. Hence, 3D numerical simulation of WSCPPDW was carried out, using CFD ANSYS Fluent. To explore the optimum operational and structural parameters of WSCPPDW, simulations with different turbine rotational speed, nozzle length, chimney outlet radius and chimney mixing section length were conducted. The results show that the flue gas jet could form a high-temperature and high-speed jet area in the chimney, having entrainment effect on the surrounding airflow. Besides, as the turbine rotational speed increases, the freshwater yield decreases and the turbine shaft power increases first and then decreases, getting peak at 200 rpm. With the increase of nozzle length, the freshwater yield and turbine shaft power first increases and then decreases; With the increase of the chimney outlet radius, the freshwater yield and turbine shaft power first increases and then decreases; As the chimney mixing section length increases, the freshwater yield and turbine shaft power increases significantly at first and then decreases slightly. From the parametric study, it is concluded that for the turbine rotational speed, the nozzle length, the chimney outlet radius and the chimney mixing section length of 200 rpm, 6 m, 9 m and 60 m, respectively, better performance could be achieved. Concretely, the power generation and hourly freshwater yield of WSCPPDW reached 377.9 kW and 20.3 ton/h, respectively.

Design of Control Laws Based on Inverted Decoupling and Linear Matrix Inequality for a Turboprop Engine

Abstract This paper proposes a systematic approach to design control laws for a turboprop engine. The proposed approach includes interactions decoupling and control laws design based on linear matrix inequality (LMI). First, since the main objective of the turboprop engine control system is to ensure propeller-absorbed power at a constant propeller speed, the linear model of a turboprop engine can be linearized into a two-input two-output (TITO) plants, and there exist the interactions between two control loops. Because inverted decoupling can well retain the dynamic characteristics of the original system, it is used to decouple the interactions so that the TITO plant can be divided into two single-input single-output plants, that is, gas-generator shaft speed is controlled by fuel flowrate and power turbine shaft speed is controlled by blade angle. Then, the control laws are designed separately for each control loop by solving the LMI group derived from static output feedback (SOF) and regional pole placement. Finally, the proposed approach is implemented on a two-spool turboprop engine (TSTPE) integrated model. The simulation results show that there exist strong interactions between two control loops of TSTPE, applying inverted decoupling to decouple these interactions is effective, and the gas-generator shaft speed and the power turbine speed can track their commands with appropriate performance by controlling the fuel flowrate and blade angle under the action of the designed control laws and inverted decoupling.

Design, Fabrication and Performance Test of Axial Flow Hydro Turbine

Hydropower is the source of renewable energy for more than a century leading to a decrease in the burning of fossil fuels whichhas an effect on the environment. The axial flow hydro turbine is placed for a small water flow rate and the low head application. Axial flow hydro turbine consists of guide vane mounted in the stationary casing and blades connected on the hub. Axial flowhydro turbine consists of four runner blades, the number of guide vane is 6 and the guide vane angle is 73˚. In this research, theavailable head and flow rate are 3.4 m and 0.14 m3/sec. Hydrofoil shape of runner blade selected NACA 6412 and modeling theblade geometry used SolidWorks software. In this research, the modal of the axial flow hydro turbine is made with thermoplasticfilament material due to produce easily. The turbine assembly was tested with various water velocities at Lon Town IrrigationChannel in Madayar Township, Myanmar. Experimental results of turbine shaft power and generator output power are alsoestimated in this research. The maximum turbine shaft power and generator output power are observed 3.66 kW and 3 kW atvolume flow rate of 0.15 m3/s.

Performance analysis and optimized control strategy for a three-shaft, recuperated gas turbine with power turbine variable area nozzle

Performance analysis and optimization for a three-shaft, recuperated gas turbine with power turbine variable area nozzle (VAN) is conducted in this paper. A modified recuperator simulation model is obtained from recuperator experiment. A gas turbine performance simulation program is established. The influence of power turbine shaft speed on engine performance is studied and optimized control of power turbine shaft speed is proposed. Comparative performance analysis proves VAN angle control improves engine performance, but leads to less compressor surge margin and increased risk of over temperature. The optimized control of VAN angle under different safety operation temperature limits and ambient temperature is investigated. Power turbine shaft speed barely influences the optimized control of VAN angle, but temperature limits and ambient temperature greatly do. By decoupling power turbine shaft speed and VAN angle, an optimized control strategy for power turbine shaft speed and VAN angle is proposed, which brings 6.37%, 15.88%, 47.80% increases in output power, and 10.84%, 25.59%, 64.97% increase in thermal efficiency when relative high-pressure shaft speed is 0.95, 0.90 and 0.85, respectively. Maximum thermal efficiency could be achieved at part-load conditions rather than design-point if temperature limit is relaxed.

A detailed analysis of free vibration on 70 MW hydro power turbine rotor

Most prime movers have vibrational problems due to the inherent unbalance due to some reason or other, the mass centre of the rotor does not coincide with the geometrical axis of the shaft known as eccentricity. During the shaft rotation a small eccentricity gives rise to a transverse force that increases with shaft rpm and tends to higher deflections of the shaft. In this approach a specified 70 MW hydro power turbine shaft is selected, models are prepared with the beam, mass, and combination elements in advanced engineering simulation software ANSYS for the specified design parameters and dimensions of the turbine shaft for free vibration analysis. The turbine rotor is placed at different locations from left to right of the turbine shaft for different bearing supports using subspace modes extraction method and modes extracted up to critical speed of 3000 rpm, which is the operating speed of the turbine. The results which include the Eigen values, Eigen vectors and responses of free vibrations and used bearing properties are recorded. Finally, it was concluded that there exists a safe location of the turbine rotor on the turbine shaft for each of the different bearing properties.

The effect of different structural parameters on wind supercharged solar chimney power plant combined with seawater desalination

Based on the mathematical model of the wind supercharged solar chimney power plant combined with seawater desalination (WSSCPPCSD), the velocity field characteristics of basic WSSCPPCSD were analyzed through three-dimensional numerical simulation. To investigate the influence of different structural parameters of system performance, systems with turbines of different blade numbers, installation angles and relative radial clearances, with guide cone or guide vane were also simulated. Unsteady numerical simulations of H-type wind pressure ventilator with different wind wheel blade installation angles were conducted, as well as another helix-type wind pressure ventilator. The results show that the increase of turbine blade number could lead to a reduced freshwater productivity, and the rotational speed corresponding to maximum turbine shaft power shifts in the direction of lower speed. Besides, with the increase of blade installation angle, both the freshwater productivity and the turbine shaft power increase first and then decrease. As the radial clearance of turbine blades increases, the system freshwater productivity increases and the noise decreases, and the turbine shaft power has a maximum value when the relative radial clearance is 2%. The addition of guide cone and guide vane can effectively improve the flow field. As for the wind pressure ventilator, system freshwater productivity and shaft power both increases first and then drops with the increase of wind wheel blade installation angle. In addition, the helix-type wind wheel can improve the self-starting performance of the wind pressure ventilator and decrease the fluctuation of blade torque at the same time, so as to improve the stability.

Automatic Simulation Method for Performance Analysis of Kerosene-Based Turbo-Pump

Kerosene-based turbo-pump is crucial to pump-fed expansion cycle scheme of the scramjet system in aerospace applications. An automatic simulation method was developed to conduct performance analysis of kerosene-based turbo-pump at low costs. Turbulence simulation combined with a multi-species surrogate model of kerosene was employed to study objective characteristics by simulating the flow-field inside the turbo-pump at 100000 rpm. Automatic simulation process, based on Design of Experiments technique, response surface model and high-fidelity numerical simulation, was applied for similarity analysis and Pareto front analysis, respectively. Results indicate that, all the characteristic curves of pump developed head (ΔHp) and turbine shaft power (Pt) with respect to mass flow rate at various rotating speeds, agree well with Similarity Criterion; ΔHp is negatively related to the efficiency of pump (ηp) in general, but the contrary is the case for Pt and the efficiency of turbine (ηt).

Numerical Study of a Gas Turbine's Shaft Cooling

This paper focuses on the numerical study of a shaft's cooling, positioned at the end of the gas turbine hot section. Due to convection and conduction phenomena, the high temperatures of the primary gas flow are transferred -via the power turbine's blades and disk- to the power turbine's shaft. If the values of these transmitted temperatures are too high, in time, negative effects can occur, like: rotor imbalance or overheating the oil surrounding the power turbine's shaft. Therefore, for the turbine's shaft to operate properly, a cooling method must be applied. The cooling method considered in this study, is a secondary air flow path, which crosses through the labyrinth, part of the shaft itself and turbine's disk.In order to investigate the heat transfer between the secondary air flow and the turbine's shaft, several computations were performed, using the CFD software Ansys CFX. Several cases were analyzed, by modifying the geometry, the material, as well as the air mass flow passing through the analyzed path. The comparison between the different results led to the selection of the best configuration, in terms of cooling performances.

Modeling the near-wake of a vertical-axis cross-flow turbine with 2-D and 3-D RANS

The near-wake of a vertical-axis cross-flow turbine was modeled numerically via blade-resolved k–ω shear stress transport (SST) and Spalart–Allmaras Reynolds-averaged Navier–Stokes (RANS) models in two and three dimensions. The results for each case were compared with the experimental measurements of the turbine shaft power, overall streamwise rotor drag, mean velocity, turbulence kinetic energy, and momentum transport terms in the near-wake at one diameter downstream. It was shown that 2-D simulations overpredict turbine loading and do not resolve mean vertical momentum transport, which plays an important role in the near-wake's momentum balance. The 3-D simulations fared better at predicting performance, with the Spalart–Allmaras model predictions being closest to the experiments. The SST model more accurately predicted the turbulence kinetic energy, while the Spalart–Allmaras model more closely matched the momentum transport terms in the near-wake. These results show the potential of blade-resolved RANS as a design tool and a way to “extrapolate” experimental flow field measurements.

A new steam turbine model for utility system design and optimization

Steam turbine shaft power performance and efficiencies depend on turbine size, type, and operating conditions. This work develops a new turbine performance model based on thermodynamic principles and semi-empirical equations to obtain general steam turbine performance estimation. Moreover, the basis of performance model and its relation to turbine efficiencies is analyzed to make clear how key operating and structural parameters affect the performance model. The new model has been validated against commercial steam turbine data and literature data and gives high accuracy for a wide range of steam turbines. The proposed model overcomes problems from previous models, which did not account for changes in steam mains pressures, and can be applied in utility system design, operational optimization, and system retrofit with complex multi-stage turbines allowing for changes in steam header conditions directly.