Active Magnetic Bearings for Gas Turbomachinery in Closed-Cycle Power Plant Systems

1988 ◽  
Author(s):  
Colin F. McDonald
Keyword(s):  
High Temperature ◽  
Power Plant ◽  
Gas Turbines ◽  
Power Plants ◽  
Closed Loop ◽  
Rotating Machinery ◽  
Magnetic Bearings ◽  
Working Fluid ◽  
Active Magnetic Bearings ◽  
Closed Cycle

Bearing lubrication systems in closed-loop plants using gas (air or helium) as the working fluid (e.g., gas turbine, gas-cooled nuclear reactor, gas compressor, etc.) are very demanding since liquid lubricant ingress could contaminate the circuit, unlike open-cycle systems where the products would be expelled in the exhaust. Oil-lubricated bearings, the tribology mainstay in the power plant field, are reliable, but in the event of a failure in the seal or buffer system, the impact of oil ingress (e.g., saturation of insulation, coking on high-temperature surfaces, or in the extreme case, conflagration of equipment) can be costly and result in extended plant downtime. The emergence in the early 1980s of a new tribology technology, namely a system in which the turbomachine rotor is levitated by a magnetic field, and positively sensed and controlled in real-time by an electronic system, now offers the designer an additional option. While an active magnetic system has many advantages, its foremost are (1) potential for very high reliability, (2) obviates the possibility of closed circuit contamination by lubricant ingress, (3) system simplicity, (4) ease of operation, and (5) ease of critical speed problems. It is projected that utilization of “electronic chips instead of liquid films” will have a significant impact on the design of high-speed rotating machinery across the full spectrum of applications. This paper outlines the emergence of active magnetic bearings in rotating machinery for closed-cycle gas turbines, and in helium circulators for future high-temperature gas-cooled nuclear power plants. The paper highlights the existing industrial technology base that will make possible the deployment of active magnetic bearings in rotating machinery for the next generation of power plants that utilize closed-loop circuits.

scholarly journals Gas Turbine Power Plant Possibilities With a Nuclear Heat Source: Closed and Open Cycles

1990 ◽  
Author(s):  
Colin F. McDonald
Keyword(s):  
High Temperature ◽  
Power Plant ◽  
Heat Source ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Combined Cycle ◽  
Closed Cycle ◽  
Cycle System ◽  
Nuclear Heat ◽  
High Temperature Gas

With the capability of burning a variety of fossil fuels, giving high thermal efficiency, and operating with low emissions, the gas turbine is becoming a major prime-mover for a wide spectrum of applications. Almost three decades ago two experimental projects were undertaken in which gas turbines were actually operated with heat from nuclear reactors. In retrospect, these systems were ahead of their time in terms of technology readiness, and prospects of the practical coupling of a gas turbine with a nuclear heat source towards the realization of a high efficiency, pollutant free, dry-cooled power plant has remained a long-term goal, which has been periodically studied in the last twenty years. Technology advancements in both high temperature gas-cooled reactors, and gas turbines now make the concept of a nuclear gas turbine plant realizable. Two possible plant concepts are highlighted in this paper, (1) a direct cycle system involving the integration of a closed-cycle helium gas turbine with a modular high temperature gas cooled reactor (MHTGR), and (2) the utilization of a conventional and proven combined cycle gas turbine, again with the MHTGR, but now involving the use of secondary (helium) and tertiary (air) loops. The open cycle system is more equipment intensive and places demanding requirements on the very high temperature heat exchangers, but has the merit of being able to utilize a conventional combined cycle turbo-generator set. In this paper both power plant concepts are put into perspective in terms of categorizing the most suitable applications, highlighting their major features and characteristics, and identifying the technology requirements. The author would like to dedicate this paper to the late Professor Karl Bammert who actively supported deployment of the closed-cycle gas turbine for several decades with a variety of heat sources including fossil, solar, and nuclear systems.

scholarly journals Performance Analyses and Evaluation of Co2 and N2 as Coolants in a Recuperated Brayton Gas Turbine Cycle for a Generation IV Nuclear Reactor Power Plant

2020 ◽  
Vol 6 (2) ◽  
Author(s):  
Emmanuel O. Osigwe ◽  
Arnold Gad-Briggs ◽  
Theoklis Nikolaidis ◽  
Pericles Pilidis ◽  
Suresh Sampath
Keyword(s):  
Power Plant ◽  
Gas Turbine ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Reactor ◽  
Reactor Power ◽  
Critical Conditions ◽  
Working Fluid ◽  
Closed Cycle ◽  
Gas Turbine Cycle

Abstract As demands for clean and sustainable energy renew interests in nuclear power to meet future energy demands, generation IV nuclear reactors are seen as having the potential to provide the improvements required for nuclear power generation. However, for their benefits to be fully realized, it is important to explore the performance of the reactors when coupled to different configurations of closed-cycle gas turbine power conversion systems. The configurations provide variation in performance due to different working fluids over a range of operating pressures and temperatures. The objective of this paper is to undertake analyses at the design and off-design conditions in combination with a recuperated closed-cycle gas turbine and comparing the influence of carbon dioxide and nitrogen as the working fluid in the cycle. The analysis is demonstrated using an in-house tool, which was developed by the authors. The results show that the choice of working fluid controls the range of cycle operating pressures, temperatures, and overall performance of the power plant due to the thermodynamic and heat properties of the fluids. The performance results favored the nitrogen working fluid over CO2 due to the behavior CO2 below its critical conditions. The analyses intend to aid the development of cycles for generation IV nuclear power plants (NPPs) specifically gas-cooled fast reactors (GFRs) and very high-temperature reactors (VHTRs).

The Efficiency of Closed-Cycle Gas Turbines Controlled by Different Methods and Programs

2020 ◽  
pp. 51-63
Author(s):  
V.D. Molyakov ◽  
B.A. Kunikeev ◽  
N.I. Troitskiy
Keyword(s):  
Gas Turbine ◽  
Heat Exchangers ◽  
Gas Turbines ◽  
Power Plants ◽  
Control Method ◽  
Low Pressure ◽  
Working Fluid ◽  
Closed Cycle ◽  
Efficient Operation ◽  
Pressure Compressor

Closed-cycle gas turbine units can be used as power plants for advanced nuclear power stations, spacecraft, ground, surface and underwater vehicles. The purpose and power capacity of closed gas turbine units (CGTU) determine their specific design schemes, taking into account efficient operation of the units both in the nominal (design) mode and in partial power modes. Control methods of both closed and open gas turbine units depend on the scheme and design of the installation but the former differ from the latter mainly in their ability to change gas pressure at the entrance to the low-pressure compressor. This pressure can be changed by controlling the mass circulating in the CGTU circuit, adding or releasing part of the working fluid from the closed system as well as by internal bypassing of the working fluid. At a constant circulating mass in the single-shaft CGTU, the temperature of the gas before the turbines and the shaft speed can be adjusted depending on the type of load. The rotational speed of the turbine shaft, blocked with the compressor, can be adjusted in specific ways, such as changing the cross sections of the flow of the impellers. At a constant mass of the working fluid, the pressure at the entrance to the low-pressure compressor varies depending on the control program. The efficiency of the CGTU in partial power modes depends on the installation scheme, control method and program. The most economical control method is changing the pressure in the circuit. Extraction of the working fluid into special receivers while maintaining the same temperature in all sections of the unit leads to a proportional decrease in the density of the working fluid in all sections and the preservation of gas-dynamic similarity in the nodes (compressors, turbines and pipelines). Specific heat flux rates, and therefore, temperatures change slightly in heat exchangers. As the density decreases, heat fluxes change, as the heat transfer coefficient decreases more slowly than the density of the working fluid. With a decrease in power, this leads to a slight increase in the degree of regeneration and cooling in the heat exchangers. The underestimation of these phenomena in the calculations can be compensated by the underestimation of the growth of losses in partial power modes.

Heat Exchanger Design Considerations for Gas Turbine HTGR Power Plant

1977 ◽  
Vol 99 (2) ◽  
pp. 237-245 ◽  
Author(s):  
C. F. McDonald ◽  
T. Van Hagan ◽  
K. Vepa
Keyword(s):  
Heat Exchanger ◽  
Power Plant ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Power Conversion ◽  
Structural Safety ◽  
Working Fluid ◽  
Closed Cycle ◽  
High Degree ◽  
Cycle Efficiency

The Gas Turbine High Temperature Gas Cooled Reactor (GT-HTGR) power plant combines the existing design HTGR core with a closed-cycle helium gas turbine power conversion system directly in the reactor primary circuit. Unlike open-cycle gas turbines where the recuperative heat exchanger is an optional component, the high cycle efficiency of the nuclear closed-cycle gas turbine is attributable to a high degree to the incorporation of the recuperator (helium-to-helium) and precooler (helium-to-water) exchangers in the power conversion loop. For the integrated plant configuration, a nonintercooled cycle with a high degree of heat recuperation was selected on the basis of performance and economic optimization studies. A recuperator of high effectiveness was chosen because it significantly reduces the optimum pressure ratio (for maximum cycle efficiency), and thus reduces the number of compressor and turbine stages for the low molecular weight, high specific heat, helium working fluid. Heat rejection from the primary system is effected by a helium-to-water precooler, which cools the gas to a low level prior to compression. The fact that the rejection heat is derived from the sensible rather than the latent heat of the cycle working fluid results in dissipation over a wide band of temperature, the high average rejection temperature being advantageous for either direct air cooling or for generation of power in a waste heat cycle. The high heat transfer rates in the recuperator (3100 MWt) and precooler (1895 MWt), combined with the envelope restraints associated with heat exchanger integration in the prestressed concrete reactor vessel, require the use of more compact surface geometries than in contemporary power plant steam generators. Various aspects of surface geometry, flow configuration, mechanical design, fabrication, and integration of the heat exchangers are discussed for a plant in the 1100 MWe class. The influence of cycle parameters on the relative sizes of the recuperator and precooler are also presented. While the preliminary designs included are not meant to represent final solutions, they do embody features that satisfy many of the performance, structural, safety, and economic requirements.

Design and Operational Aspects of Gas and Steam Turbines for the Novel Solar Hybrid Combined Cycle SHCC®

2010 ◽  
Author(s):  
Stephan Heide ◽  
Uwe Gampe ◽  
Ulrich Orth ◽  
Markus Beukenberg ◽  
Bernd Gericke ◽  
...  
Keyword(s):  
High Temperature ◽  
Power Plant ◽  
Gas Turbine ◽  
Heat Input ◽  
Gas Turbines ◽  
Power Plants ◽  
Combined Cycle ◽  
Solar Irradiation ◽  
Test Field ◽  
Solar Heat

Solar hybrid power plants are characterized by a combination of heat input both of high temperature solar heat and heat from combustion of gaseous or liquid fuel which enables to supply the electricity market according to its requirements and to utilize the limited and high grade natural resources economically. The SHCC® power plant concept integrates the high temperature solar heat into the gas turbine process and in addition — depending on the scheme of the process cycle — downstream into the steam cycle. The feed-in of solar heat into the gas turbine is carried out between compressor outlet and combustor inlet either by direct solar thermal heating of the pressurized air inside the receivers of the solar tower or by indirectly heating via interconnection of a heat transfer fluid. Thus, high shares of solar heat input referring to the total heat input of more than 60% in design point can be achieved. Besides low consumption of fossil fuels and high efficiency, the SHCC® concept is aimed for a permanent availability of the power plant capacity due to the possible substitution of solar heat by combustion heat during periods without sufficient solar irradiation. In consequence, no additional standby capacity is necessary. SHCC® can be conducted with today’s power plant and solar technology. One of the possible variants has already been demonstrated in the test field PSA in Spain using a small capacity gas turbine with location in the head of the solar tower for direct heating of the combustion air. However, the authors present and analyze also alternative concepts for power plants of higher capacity. Of course, the gas turbine needs a design which enables the external heating of the combustion air. Today only a few types of gas turbines are available for SHCC® demonstration. But these gas turbines were not designed for solar hybrid application at all. Thus, the autors present finally some reflections on gas turbine parameters and their consequences for SHCC® as basis for evaluation of potentials of SHCC®.

scholarly journals Electrically Charged

2002 ◽  
Vol 124 (06) ◽  
pp. 50-52
Author(s):  
Lee Longston
Keyword(s):  
Electric Power ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Nuclear Reactor ◽  
The United States ◽  
Combined Cycle ◽  
Working Fluid ◽  
Closed Cycle ◽  
Wide Range

This article focuses on gas turbines that were produced in 2001 spanning a wide range of capacities. As the engineer's most versatile energy converters, gas turbines producing thrust power continued in 2001 to propel most of the world's aircraft, both military and commercial. The largest commercial jet engines today can produce as much as 120,000 pounds thrust, or some 534,000 Newton. More natural gas pipeline capacity will be added to feed the surge in gas-driven electric power plants that have been corning online in the United States and other parts of the world. The gas turbine may come to be used in a new, commercially promising closed-cycle configuration. A South African company has been working on plans to build and test a prototype of a closed-cycle electric power gas turbine, which uses helium gas as the working fluid and a helium-cooled nuclear reactor to provide heat to power the cycle. If the gas turbine-nuclear reactor power plant is successful, the gas turbine may be the key to yet another energy conversion device, as it has been with record-setting numbers of combined-cycle plants installed worldwide.

The μ Approach to Control of Active Magnetic Bearings

2002 ◽  
Vol 124 (3) ◽  
pp. 566-570 ◽  
Author(s):  
R. L. Fittro ◽  
C. R. Knospe
Keyword(s):  
Laboratory Test ◽  
Rotating Machinery ◽  
Vibration Response ◽  
Experimental Results ◽  
Magnetic Bearings ◽  
Pd Controller ◽  
Active Magnetic Bearings ◽  
Test Rig ◽  
Rotor Vibration ◽  
Multivariable Controller

Many important industrial problems in the control of rotating machinery with active magnetic bearings concern the minimization of the rotor vibration response to poorly characterized disturbances at a single or several shaft locations, these typically not corresponding to those of a sensor or actuator. Herein, we examine experimental results of a multivariable controller obtained via μ synthesis with a laboratory test rig. These indicate that a significant improvement in performance can be obtained with a multivariable μ controller over that achieved with an optimal decentralized PD controller.

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