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The automotive gas turbine has not been adopted for many reasons, among which are that the materials required have been expensive, and the fuel consumption has been unremarkable. A new approach is to use a marked reduction in blade speeds (and therefore in blade and disk stresses) through multistaging, allowing the use of injection-molded compressor components and low-cost ceramic materials (e.g. technology developed for automotive turbochargers) for all hot parts. The pressure ratio will also be lowered and the heat-exchanger effectiveness increased. The resulting engine is larger than existing experimental turbines but still smaller and lighter than an equivalent spark-ignition or compression-ignition engine, with a marked improvement in projected fuel efficiency.

Two successive surveys and round-robin interviews were conducted to determine if there might be in the offing for automobiles an alternative engine which would exhibit low emissions meeting the most stringent requirements. Comparison between engines were couched in terms of selected “acceptability factors” which went well beyond emissions, alone. The overall acceptability was evaluated considering emissions, customer requirements for an engine, manufacturers' requirements for an engine, and engine efficiency and fuel versatility. An attempt was made to establish a time scale as to R and D requirements and eventual production. Comparison of all engines was made with equivalent pre-control Otto cycle engines as the standard. Alternative engines were deemed to be any power plant that was not based on spark ignition Otto cycle engines, or diesel engines. The remaining heat engines largely used continuous combustion as the heat source.