Helium and Combustion Gas Turbine Power Conversion Systems Comparison

Abstract

For closed-cycle gas turbines, in a size to meet utility power generation needs, the selection of helium as the working fluid represents the best solution in terms of the overall power conversion system considering the differing requirements of the turbomachinery and heat exchangers. Helium is well suited for the nuclear Brayton cycle because it is neutronically inert. The impact of helium’s unique properties on the performance and size of the power conversion system components is discussed in this paper. The helium gas turbine plants, that have operated were based on 1950s and 1960s technology, represent a valuable technology base in terms of practical experience gained. However, the design of the Gas Turbine Modular Helium Reactor (GT-MHR), which could see utility service in the first decade of the 21st century will utilize turbomachinery and heat exchanger technologies from the combustion gas turbine and aerospace industries. An understanding of how the design of power conversion systems for closed-cycle plants and combustion gas turbines are affected by the working fluids (i.e., helium and air, respectively) is the major theme of this paper.

Perspective on a Combustion-Free Gas Turbine to Meet Power Generation Needs in the 21st Century

“…) represents a valuable data base,and advantage should be taken of this for the NCBC plant. The overall design of helium turbomachinery is well understood (Endres 1970,Haselbacher 1974,McDonald 1994b,and much of the design methodology associated with combustion gas turbines is applicable for helium turbomachinery (McDonald 1995c).To ensure that the turbomachine operates well in the demonstration plant,a series of subcomponent tests will provide the data for the rotating machinery.Technology in the following areas will be generated from rig tests, 1)aerodynamic performance of the compressor and turbine blading,2) acoustic data,3) magnetic journal and thrust bearings,4) rotor dynamics,5) seals,6) controls,and 7) casing containment confirmation (in the event of an overspeed rotor burst).…”

The Indirect Cycle: A Logical and Practical Nuclear Gas Turbine Power Plant Concept

“…Operating in helium (with its low molecular weight) necessitates a large number of compressor and turbine stages and this results in a long slender rotor. Helium turbomachine design methods are well established (McDonald, 1994c) with technology from combustion turbines being directly applicable (McDonald, 1995c). Advantage can also be taken of experience gained in Germany from the operation of the aforementioned Oberhausen gas turbine plant and a helium gas turbine test facility (Weisbrodt, 1995).…”

The Key Role of Heat Exchangers in Closed Brayton Cycle Gas Turbine Power Plants

“…The compact recuperator (Kretzinger, 1985) permits utilization of high effectiveness (i.e., 95%) with attendant gains in plant efficiency. • Operating in the clean helium secondary loop, very small hydraulic diameter passages can be used with resultant surface compactness values on the order of three times that in open cycle gas turbine recuperators (McDonald, 1995c). Operating in the laminar flow regime, but with highly offset surfaces, very high heat transfer coefficients can be realized by virtue of the surface geometry, high system pressure, and the high thermal conductivity of helium and this results in a very high thermal density (i.e., 17 MW/m 3).…”