High-speed Synchronous Generator Research Articles

Use of Synchronous Generators for Gas Turbine Power Plants

The combination of gas turbine engines and low-speed generators that are part of power plants is a large-mass unit with low specific indicators of the mass-to-unit power ratio. (Research purpose) The research purpose is developing a new kinematic scheme of a gas turbine engine with a high-speed synchronous electric generator, higher reliability and long service life, reduced weight and size characteristics of the power plant. (Materials and methods) Established that small gas turbine power and general-purpose power plants are not produced in Russia, research work was not systematic. It was determined that synchronous generators and gas turbine engines are used on two-shaft kinematic systems that reduce the rotation frequency of the generator rotor, where a large diameter of the free turbine entails a higher level of vibration, and due to the high level of sliding leads to a lower torque of the power plant at low rpm. (Results and discussion) It has been shown that the use of single-channel kinematic schemes contributes to simpler control, this opens up a wide prospect for their use in power plants for the purpose of supplying electricity to consumers and mobile agricultural vehicles. A new kinematic scheme of a high-speed generator has been developed, in which the rotor and stator interact with each other according to the type of sliding bearing. (Conclusions) The advantages of using a single-shaft kinematic scheme for the joint operation of a gas turbine engine with a high-speed synchronous generator have been revealed, which are expressed in a smaller moment of straining of the rotor and the absence of a sliding coefficient between the shafts. It was stated that as a result of using the proposed design of the power module, the reliability of the generator increases, the operating speed increases due to the use in the design of the polished outer surface of the rotor and the polished inner surface of the stator, working according to the type of sliding bearing, with forced oil supply at a pressure of 2-5 kilograms per square centimeter, at the same time, heat removal from the stator winding improves.

Development and experimental study of a supercritical CO2 axial turbine applied for engine waste heat recovery

CO2-based transcritical power cycle (CTPC) has been proposed as a suitable engine waste heat recovery (E-WHR) technology with the advantage of miniaturization and good recovery capacity. Expander, as the core power conversion device, is of great importance to the overall cycle performances. The main purpose of this paper is to conduct dynamic tests of the proposed turbine expander, with focus on the turbine operational characteristics and performance. In this study, a partial admission axial turbine expander coaxial with a high-speed synchronous generator is designed and manufactured considering the thermodynamic properties of supercritical CO2. The geometry of the turbine is 56 mm rotor diameter, 4 mm blade height, and 39000 rpm of operating speed at the inlet design condition of 10 MPa and 230 °C, outlet condition of 6 MPa and mass flow rate of 0.18 kg/s. The performance of the developed turbine expander and CTPC system with respect to the rotational speed and mass flow rate are investigated experimentally. Based on the experimental data, the maximum rotational speed of the the turbine reaches 41584 rpm and the turbine expander generated maximum power 2.27 kW at 20878 rpm. The power capacity of the turbine increases to the maximum value first and then decreases with the increase of rotational speed as well as the isentropic efficiency. The power generation of the turbine expander is proportional to pressure ratio as well as mass flow rate.

Generadores Síncronos de Alta Velocidad: Una Evaluación Crítica

Considering that there are electromagnetic, mechanical and thermal constraints that determine the design of high-speed electrical machines, the criteria that lead to adequate selection of the machine are established in this work. Moreover, taking into account the current state of technology, the critical values in the ratio (output power)/(rotation speed), are presented. The paper focuses on the high-speed synchronous generators, especially in permanent magnet generators, inductor alternators and flux switching alternators, emphasizing their constructive fundamentals and their advantages and disadvantages. The analysis is completed with a critical assessment that classifies them according to previously defined requirements. Although the decision of the final choice is largely determined by the application of interest, it can be said that, in general, synchronous generators with permanent magnets in the rotor are the best option.

Performance of a radial-inflow turbine integrated in an ORC system and designed for a WHR on truck application: An experimental comparison between R245fa and R1233zd

The goal of this study is to experimentally compare the performance of an Organic Rankine Cycle (ORC) system equipped with a radial-inflow turbine for two working fluids: R245fa and R1233zd. The radial-inflow turbine is a small-scale prototype designed to convert the waste heat from the exhaust gases of a truck combustion engine and was developed mainly using components of truck turbochargers. It is directly connected to a high-speed synchronous generator. The bearings system of the turbine and the generator have the innovative particularity to be respectively lubricated and cooled down by the working fluid so no additional lubricant or coolant is needed. The experimental comparison is carried out over a test-rig equipped with the radial turbine. The heat wasted by the truck through the exhaust gases is simulated using an electric oil boiler coupled to the ORC loop. The electrical power supplied by the turbine, limited to a maximum of 3.5kWel by the generator, is then dissipated in a load bank composed of truck fans while the condenser is cooled by a water loop. Measurements in steady-state are performed in order to evaluate the performance of the turbine-generator set when varying the pressure ratio, the rotational speed, the inlet temperature and the mass flow rate of the turbine and the lubrication flow rate of the bearings for various oil temperatures and mass flow rates. In order to identify the most suitable fluid for the Waste Heat Recovery (WHR) application, three comparison methods are proposed and discussed based on the measurements. Finally, because the turbine-generator set is the first oil-free prototype developed by the manufacturer, potential sources of improvements are discovered and discussed.

EM–SS-Wavelets for Characterization of High-Speed Generators in Distributed Generation

An electromagnetic–state space–wavelet neural network modeling environment is presented and used for the characterization of high-speed synchronous generators during out-of-phase operation in distributed generation (DG) of a microgrid. This mode of operation may result in stresses in the network or the failure of the high-speed generators. The approach is validated, by comparing simulation results with test data, and its effectiveness is established in terms of accuracy and fast response. In addition, it is demonstrated in a case study involving two DG units in a microgrid that the stresses and damages are minimized in an out-of-phase DG unit when connected to the grid through an inverter.

Development and Characterization of Small-Scale ORC System Using Scroll Expander

In order to determine the operating characteristics of a small-scale ORC (organic Rankine cycle) system for various low temperature heat sources, experiments were carried out. A small-scale ORC power generation system adopting R-245fa as a working fluid was designed and manufactured. Hot water was used for the heat source and the temperature was controlled by the 110 kW electric resistance heaters which provided up to 150 °C. Cooling temperature was controlled by a circulating water chiller to simulate various heat sink environments. An open-drive oil-free scroll expander directly connected to a high-speed synchronous generator was installed in the ORC unit. The efficiencies of the cycle and the expander, electric power of the developed ORC system with respect to the operating conditions were investigated by experiments. The factors which influence the performance of the oil-free scroll expander were analyzed and discussed.

Design and experimental study of ORC (organic Rankine cycle) and radial turbine using R245fa working fluid

In this study, an ORC (Organic Rankine Cycle) capable of generating electric power using a low-temperature heat source was developed and an experimental study was conducted. A radial turbine directly connected to the high-speed synchronous generator was also designed and developed. R245fa was adopted as a working fluid, in consideration of the operation conditions of the cycle and its environmentally-friendly characteristics. Experiments were conducted to analyze the operational characteristics and performance of the developed ORC. The efficiencies of the cycle and the turbine, electric power of the developed ORC with respect to the operation conditions were investigated in a series of experiments. The factors which influence the performance of the developed ORC were analyzed and discussed.