Recuperated gas turbine aeroengines, part II: engine design studies following early development testing

Purpose To advance the design of heat exchanged gas turbine propulsion aeroengines utilising experience gained from early development testing, and based on technologies prevailing in the 1970‐2000 time frame. Design/methodology/approach With emphasis on recuperated helicopter turboshaft engines, particularly in the 1,000 hp (746 kW) class, detailed performance analyses, parametric trade‐off studies, and overall power plant layouts, based on state‐of‐the‐art turbomachinery component efficiencies and high‐temperature heat exchanger technologies, were undertaken for several engine configuration concepts. Findings Using optimised cycle parameters, and the selection of a light weight tubular heat exchanger concept, an attractive engine architecture was established in which the recuperator was fully integrated with the engine structure. This resulted in a reduced overall engine weight and lower specific fuel consumption, and represented a significant advancement in technology from the modified simple‐cycle engines tested in the late 1960s. Practical implications While heat exchanged engine technology advancements were projected, there were essentially two major factors that essentially negated the continued study and development of recuperated aeroengines, namely again as mentioned in Part I, the reduced fuel consumption was not regarded as an important economic factor in an era of low‐fuel cost, and more importantly in this time frame very significant simple‐cycle engine performance advancements were made with the use of significantly higher pressure ratios and increased turbine inlet temperatures. Simply stated, recuperated variants could not compete with such a rapidly moving target. Originality/value Establishing an engine design concept in which the recuperator was an integral part of the engine structure to minimise the overall power plant weight was regarded as a technical achievement. Such an approach, together with the emergence of lighter weight recuperators of assured structural integrity, would find acceptance around the year 2000 when there was renewed interest in the use of more efficient heat exchanged variants towards the future goal of establishing “greener” aeroengines, and this is discussed in Part III of this paper.