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It is well known that the use of “two volume” scavenging models, where the cylinder is idealized as two volumes with gas exchanged between them, represents a substantial improvement over the “perfect mixing” scavenging model for the computer simulation of two stroke engines. This is especially true during the early stages of the scavenging process, when scavenge ratio is low. It is shown that a simple, closed form relationship exists between the “stripping off” factor, Y, used in two volume scavenging models and the variation in scavenge efficiency with scavenge ratio.. A method is presented for estimating Y at low scavenge ratios using existing correlations of scavenge efficiency with scavenge ratio. This should make it possible to construct very good two volume scavenging models using only existing published data. Such models would be able to simulate in cylinder and exhaust gas conditions during the early stages of scavenging.

A novel two stroke cycle diesel engine is evaluated as a general aviation aircraft powerplant. Two certificated spark-ignited gasoline reciprocating engines are also evaluated in the same aircraft. The evaluation of aircraft propulsion performance considered only the effects of altered powerplant parameters on the range of an aircraft having a fixed gross weight and payload cruising at a given lift/drag ratio. Thermodynamic analysis finds the diesel engine can have a sea level power rating exceeding the 10,000 foot cruise power requirement by 55% with nearly equal specific fuel consumption, a low engine speed and a modest cylinder pressure. It uses a single-stage, radial turbocharger without intercooling or auxiliary mechanical scavenging. The diesel engine can significantly increase the range of a particular airplane now powered by a certificated turboprop engine. The candidate gasoline engines could not equal the turboprop-powered aircraft performance.