Microturbine Rotational Speed Selection

2013 ◽  
Author(s):  
C. Rodgers
Keyword(s):  
Permanent Magnet ◽  
Output Power ◽  
Thermal Efficiency ◽  
Rotational Speed ◽  
High Speed ◽  
Mechanical Design ◽  
Pressure Ratio ◽  
Direct Drive ◽  
Power Turbine ◽  
Speed Selection

This paper delves upon the Aero-Thermodynamic performance and Mechanical design aspects of microturbines comprising a single shaft radial compressor driven by a single stage radial inflow turbine with a combustor and recuperator sized to directly drive a permanent magnet type high speed generator with an output power in the 5–10KW bracket and commensurate rotational speeds in the 100–200 krpm range. It is initially shown that stipulation of a cycle design point output power, turbine inlet or exit temperatures, and compressor pressure ratio delivering optimum thermal efficiency inherently confines rotational speed selection, and that independent rotational speed choice away from those identified optimum speed regimes may result in cycle thermal efficiency compromises. Confining the cycle analysis within temperature limits of cost competitive superalloys and foil materials reveals that the achievement of optimum thermal efficiency is more dependent on temperature at the turbine exit rather than at inlet. Albeit the choice of rotational speed is of particular importance in the compressor and turbine design it moreover is dominant in the mechanical design of the rotating assembly in terms of high speed bearing life and shaft dynamic stability. As a consequence rotating assembly and bearing design options suitable for direct drive permanent magnet generators are reviewed and recommendations offered as to the prime candidate assemblies for future microturbines in the 5.0 to 10.0 kW power output range.

Particular Coupled Electromagnetic, Thermal, Mechanical Design of High-Speed Permanent-Magnet Motor

2020 ◽  
Vol 56 (3) ◽  
pp. 1-5 ◽  
Author(s):  
A. Koronides ◽  
C. Krasopoulos ◽  
D. Tsiakos ◽  
M. S. Pechlivanidou ◽  
A. Kladas
Keyword(s):  
Permanent Magnet ◽  
High Speed ◽  
Mechanical Design ◽  
Permanent Magnet Motor

150 kW Class Two-Stage Radial Inflow Condensing Steam Turbine System

2011 ◽  
Author(s):  
Kazutaka Hayashi ◽  
Hiroyuki Shiraiwa ◽  
Hiroyuki Yamada ◽  
Susumu Nakano ◽  
Kuniyoshi Tsubouchi
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Output Power ◽  
Power Output ◽  
Thermal Efficiency ◽  
Rotational Speed ◽  
High Pressure Turbine ◽  
Two Stage ◽  
Electrical Efficiency ◽  
Design Value

A prototype machine for a 150 kW class two-stage radial inflow condensing steam turbine system has been constructed. This turbine system was proposed for use in the bottoming cycle for 2.4 MW class gas engine systems, increasing the total electrical efficiency of the system by more than 2%. The gross power output of the prototype machine on the generator end was 150kW, and the net power output on the grid end which includes electrical consumption of the auxiliaries was 135kW. Then, the total electrical efficiency of the system was increased from 41.6% to 43.9%. The two-stage inflow condensing turbine system was applied to increase output power under the supplied steam conditions from the exhaust heat of the gas engines. This is the first application of the two-stage condensing turbine system for radial inflow steam turbines. The blade profiles of both high- and low-pressure turbines were designed with the consideration that the thrust does not exceed 300 N at the rated rotational speed. Load tests were carried out to demonstrate the performance of the prototype machine and stable output of 150 kW on the generator end was obtained at the rated rotational speed of 51,000 rpm. Measurement results showed that adiabatic efficiency of the high-pressure turbine was less than the design value, and that of the low-pressure turbine was about 80% which was almost the same as the design value. Thrust acting on the generator rotor at the rated output power was lower than 300 N. Despite a lack of high-pressure turbine efficiency, total thermal efficiency was 10.5% and this value would be enough to improve the total thermal efficiency of a distributed power system combined with this turbine system.

scholarly journals Design and Optimization of a High-Speed Switched Reluctance Motor

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6733
Author(s):  
Stefan Kocan ◽  
Pavol Rafajdus ◽  
Ronald Bastovansky ◽  
Richard Lenhard ◽  
Michal Stano
Keyword(s):  
Permanent Magnet ◽  
Output Power ◽  
High Speed ◽  
Permanent Magnet Synchronous Motor ◽  
Switched Reluctance Motor ◽  
Torque Ripple ◽  
Synchronous Motor ◽  
Switched Reluctance ◽  
Design And Optimization ◽  
Reluctance Motor

Currently, one of the most used motor types for high-speed applications is the permanent-magnet synchronous motor. However, this type of machine has high costs and rare earth elements are needed for its production. For these reasons, permanent-magnet-free alternatives are being sought. An overview of high-speed electrical machines has shown that the switched reluctance motor is a possible alternative. This paper deals with design and optimization of this motor, which should achieve the same output power as the existing high-speed permanent-magnet synchronous motor while maintaining the same motor volume. The paper presents the initial design of the motor and the procedure for analyses performed using analytical and finite element methods. During the electromagnetic analysis, the influence of motor geometric parameters on parameters such as: maximum current, average torque, torque ripple, output power, and losses was analyzed. The analysis of windage losses was performed by analytical calculation. Based on the results, it was necessary to create a cylindrical rotor shape. The rotor modification method was chosen based on mechanical analysis. Using thermal analysis, the design was modified to meet thermal limits. The result of the work was a design that met all requirements and limits.

A Generalized Procedure to Estimate Matching of Power Turbine With Aeroderivative Gas Generator at High Speed Settings

2005 ◽  
Author(s):  
Inam U. Haq
Keyword(s):  
High Pressure ◽  
High Speed ◽  
Pressure Ratio ◽  
Gas Generator ◽  
High Pressure Turbine ◽  
Data Manipulation ◽  
Turbine Inlet ◽  
Engine Design ◽  
Power Turbine ◽  
Set Up

This paper encapsulates generalized considerations of power turbine matching with aeroderivative gas generator at high power settings. A computation route is set up to estimate the magnitude of the desired parameters from design point knowledge of a gas generator. Then, a method is delineated to verify matching of power turbine inlet nozzle area with exhaust of gas generator by measuring tangible tested parameters. Data manipulation revealed that there exists a favorable correlation between pressure ratio of high pressure turbine and gas generator speed that may directly reflect the influence of physical area change of power turbine inlet nozzle area. A practical example is presented to demonstrate the procedure. From engine design to retirement, the generalized considerations may be applied on several occasions where question of matching may become important and require explanation for performance and financial justifications. Some generalized rules of matching are condensed and their applications are suggested.

scholarly journals Off-Design Performance Comparison Between Single and Two-Shaft Engines: Part 1 — Fixed Geometry

2020 ◽  
Author(s):  
Th. Nikolaidis ◽  
A. Pellegrini ◽  
H. I. H. Saravanamuttoo ◽  
I. Aslanidou ◽  
A. Kalfas ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Mass Flow ◽  
Thermal Efficiency ◽  
Rotational Speed ◽  
Pressure Ratio ◽  
Performance Comparison ◽  
Part Load ◽  
Design Performance ◽  
Research Activities ◽  
Compressor Pressure Ratio

Abstract This paper describes an investigation into the off-design performance comparison of single and two-shaft gas turbine engines. A question that has been asked for a long time which gas turbine delivers a better thermal efficiency at part load. The authors, notwithstanding their intensive searches, were unable to find a comprehensive answer to this question. A detailed investigation was carried out using a state of the art performance evaluation method and the answer was found to be: It depends! In this work, the performance of two engine configurations is assessed. In the first one, the single-shaft gas turbine operates at constant shaft rotational speed. Thus, the shape of the compressor map rotational speed line will have an important influence on the performance of the engine. To explore the implications of the shape of the speed line, two single-shaft cases are examined. The first case is when the speed line is curved and as the compressor pressure ratio falls, the non-dimensional mass flow increases. The second case is when the speed line is vertical and as the compressor pressure ratio falls, the non-dimensional mass flow remains constant. In the second configuration, the two-shaft engine, the two-shafts can be controlled to operate at different rotational speeds and also varying relationships between the rotational speeds. The part-load operation is characterized by a reduction in the gas generator rotational speed. The tool, which was used in this study, is a 0-D whole engine simulation tool, named Turbomatch. It was developed at Cranfield and it is based on mass and energy balance, carried out through an iterative method, which is based on component maps. These generic, experimentally derived maps are scaled to match the design point of a particular engine before an off-design calculation is performed. The code has been validated against experimental data elsewhere, it has been used extensively for academic purposes and the research activities that have taken place at Cranfield University. For an ideal cycle, the single-shaft engine was found to be a clear winner in terms of part-load thermal efficiency. However, this picture changed when realistic component maps were utilized. The basic cycle and the shape of component maps had a profound influence on the outcome. The authors explored the influence of speed line shapes, levels of component efficiencies and the variation of these component efficiencies within the operating range. This paper describes how each one of these factors, individually, influences the outcome.

Experimental and Numerical Study of Orifice Discharge Coefficients in High-Speed Rotating Disks

1996 ◽  
Vol 118 (2) ◽  
pp. 400-407 ◽  
Author(s):  
S. Wittig ◽  
S. Kim ◽  
R. Jakoby ◽  
I. Weißert
Keyword(s):  
Rotational Speed ◽  
High Speed ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Tangential Velocity ◽  
Laser Doppler Velocimeter ◽  
Rotating Disks ◽  
Complex Flow ◽  
Local Flow ◽  
Discharge Coefficients

Experimental and numerical results of the flow through orifices in rotating disks are presented, with emphasis on basic physical phenomena. It is shown that rotational effects strongly influence the massflow discharged, a phenomenon that cannot be modeled by a stationary setup. The study includes the determination of discharge coefficients under variation of the length-to-diameter ratio, pressure ratio, and rotational speed. The pressure ratio covers low as well as critical values, the maximum rotational speed is 10,000 rpm, which is equivalent to a tangential velocity of 110 m/s. In order to understand the flow structure, local flow velocities were measured by means of a two-dimensional Laser-Doppler Velocimeter. Phase-resolved measurements have been carried out in front of and behind the orifices. A three-dimensional Finite-Volume Code with body-fitted coordinates in a rotating frame of reference is employed for the numerical analysis and the verification of its possibilities and limitations. The results reveal a very complex flow field, which is dominated by high velocity gradients in close vicinity to the orifices. The comparison of the computational solutions with the experimental data shows good agreement. Based on the measurements in combination with the numerical solution, a detailed insight into the physical properties of the flow is achieved.

Thermo-Economics of a Small 50 KW Turbogenerator

1997 ◽  
Author(s):  
C. Rodgers
Keyword(s):  
Thermal Efficiency ◽  
Gas Turbines ◽  
High Speed ◽  
Pressure Ratio ◽  
Operating Time ◽  
Cycle Performance ◽  
Material Technology ◽  
Diesel Cycle ◽  
Near Term

Recent projections foster the belief that small high temperature heat exchanged gas turbines incorporating ceramic rotors, and ceramic exhaust beat exchangers, may eventually have thermodynamic efficiencies competitive with Diesel cycle engines. Small high speed Brayton cycle gas turbine turbogenerators on the near term verge of production will indeed have improved thermal efficiencies, but ceramic material technology has not yet matured to the engine production stage. Although thermal efficiency is a dominant driver, manufacturing costs and long term engine durability are still a major concern to the engine manufacturer. As a consequence the thermodynamic performances of small gas turbines are still, in this last decade of the 20th century, primarily constrained by the temperature limits of the metallic stator/rotor and metallic heat exchanger. This paper reviews optimum thermo-economic design considerations for a small 50 KW output turbogenerator, covering the effect of cycle performance parameters on, engine configuration, rotational speeds engine weight, manufacturing and direct operating costs. The effect of design pressure ratio on part load thermal efficiency is also addressed for applications with extended operating time at low output powers.

Advanced Supersonic Component Engine for Military Applications

2007 ◽  
Author(s):  
Shawn P. Lawlor ◽  
Robert C. Steele ◽  
Peter Baldwin
Keyword(s):  
Shock Wave ◽  
Gas Turbines ◽  
High Speed ◽  
Size Range ◽  
Pressure Ratio ◽  
Fuel Efficiency ◽  
Axial Flow ◽  
Direct Drive ◽  
Wave Compression ◽  
Shock Wave Compression

A 1500 kWe Brayton cycle engine is in development that has the efficiency of a diesel, but with the size, weight and maintenance attributes of a gas turbine. The Advanced Supersonic Component Engine (ASCE) combines many of the proven features of shock wave compression and expansion systems, commonly used in supersonic flight inlet and nozzle designs, with turbo-machinery practices employed in conventional axial flow gas turbines. The superior efficiency of the ASCE is a result of high pressure shock wave compression and supersonic expansion phenomena that produce high component efficiencies and a unique engine configuration that minimizes flow stream turning losses throughout the system. The engine employs a two stage counter-rotating configuration to achieve a 30:1 pressure ratio and a 42% simple cycle efficient engine to drive a high-speed direct drive permanent magnet (PM) electric motor/generator for all electric power and propulsion applications. The system promises a specific fuel consumption equal to or better than current reciprocating diesel engines in this size range, but with a 10:1 weight reduction and a 4:1 improvement in time-between-overall compared to marine diesel systems in this size range. This is a 2:1 increase in fuel efficiency at full power over existing gas turbines in this size range.

VECTRA™ Power Turbine Development Program

2001 ◽  
Author(s):  
Bruce R. deBeer ◽  
David A. Nye
Keyword(s):  
Gas Turbines ◽  
High Speed ◽  
Mechanical Design ◽  
Development Program ◽  
Dynamic Strain ◽  
Load Testing ◽  
Operating Characteristics ◽  
Gas Generator ◽  
Full Load ◽  
Power Turbine

Dresser-Rand developed the VECTRA-40 power turbine specifically for the LM2500+ gas generator. This “clean sheet of paper” design uses some of the best features from both aeroderivative and heavy duty gas turbines. After the design phase was complete, an extensive development program was undertaken to confirm that both the mechanical and aerodynamic design objectives were met. Two units were built, instrumented, and tested to full load. In addition, several components were rig tested to verify stiffness, natural frequency, or operating characteristics. Finally, some events that could not be physically tested, such as blade out response, were tested virtually. During development testing, the power turbine was extensively instrumented with state-of-the-art sensors to verify the mechanical design and aerodynamic performance of the VECTRA. A PC based data acquisition system (DAQ) was constructed to simultaneously acquire and record over 1000 individual channels of data. Instrumentation was installed to record the mechanical responses and operating temperatures of all rotating components, as well as critical stationary components. Other groups of instrumentation were used to verify flowpath performance, cooling air distribution, and lubrication system operation. The physical devices connected to the DAQ system ranged from industrial transducers and signal conditioners to an innovative external telemetry system for rotating thermocouples and dynamic strain gages. The VECTRA is a high speed power turbine that was initially designed for mechanical drive applications. However recent component testing and full load testing of two units in generator drive packages have demonstrated that it is also well suited for power generation applications.

scholarly journals Design and Operating Mode Study of a New Concept Maglev Car Employing Permanent Magnet Electrodynamic Suspension Technology

2021 ◽  
Vol 13 (11) ◽  
pp. 5827
Author(s):  
Ze Zhang ◽  
Zigang Deng ◽  
Shuai Zhang ◽  
Jianghua Zhang ◽  
Li’an Jin ◽  
...  
Keyword(s):  
Permanent Magnet ◽  
Rotational Speed ◽  
Driving Force ◽  
High Speed ◽  
Levitation Force ◽  
Reaction Force ◽  
Operating Mode ◽  
Low Noise ◽  
Force Model ◽  
Electrodynamic Suspension

Based on the principle of permanent magnet electrodynamic suspension (PMEDS), a new concept maglev car was designed by using rotary magnetic wheels and a conductor plate. It has the advantages of being high-speed, low-noise, environmentally friendly, safe and efficient. The PMEDS car is designed to use a permanent magnet electrodynamic wheel (EDW) to achieve the integration of levitation force and driving force. The levitation force is generated by the repulsive force of the eddy current magnetic field, and the driving force is generated by the reaction force of magnetic resistance. A simplified electromagnetic force model of the EDW and a dynamics model of the PMEDS car were established to study the operating mode. It shows that the PMEDS car can achieve suspension when the rotational speed of the EDWs reaches a certain threshold and the critical speed of the EDWs is 600 rpm. With the cooperation of four permanent magnet EDWs, the PMEDS car can achieve stable suspension and the maximum suspension height can reach 7.3 mm. The working rotational speed of EDWs is 3500 rpm. At the same time, the movement status of the PMEDS car can be controlled by adjusting the rotational speed of rear EDWs. The functions of propulsion, acceleration, deceleration, and braking are realized and the feasibility of the PMEDS car system is verified.

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