The use of a regenerative cycle powerplant is a means of improving the part load fuel consumption of gas turbine engines. The use of air-to-gas regenerative systems for high thermal effectiveness and low pressure drop goals, however, can involve a prohibitive increase in engine volume and weight and a severe compromise to engine configuration. This paper describes a lightweight regenerator for a 4000-shp turboshaft engine in which the transfer of heat from the turbine exhaust gas to the compressor discharge air is accomplished by a liquid metal system using NaK as the heat transport fluid. The design of the regenerator system, consisting of an exhaust gas-to-liquid metal heat exchanger, a liquid metal-to-compressor air heat exchanger and a liquid metal rotary induction pump which form the hermetically sealed liquid metal circuit, is presented. Results of analytical studies and information concerning the special manufacturing processes for these system components are described. The results of performance and durability testing of this regenerator system under simulated engine conditions are also presented and compared with predicted performance.

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