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Aircraft engine power is degraded with increasing altitude according to the resultant reduction in air pressure, temperature, and density. One way to mitigate this problem is through turbo-normalization of the air being supplied to the engine. Supercharger and turbocharger components suffer from a well-recognized loss in efficiency as they are scaled down in order to match the reduced mass flow demands of small-scale Internal Combustion Engines. This is due in large part to problems related to machining tolerance limitations, such as the increase in relative operating clearances, and increased blade thickness relative to the flow area. As Internal Combustion Engines decrease in size, they also suffer from efficiency losses owing primarily to thermal loss. This amplifies the importance of maximizing the efficiency of all sub-systems in order to minimize specific fuel consumption and enhance overall aircraft performance.

The engines used to power small unmanned aerial systems are often modified commercial products designed for use by hobbyists on small model aircraft at low altitude. For military applications, it is desirable to fly at high altitudes. Maintaining power from the engine at the reduced ambient air pressures associated with high altitudes requires some method of increasing air delivery to the intake manifold. Conventional turbochargers and superchargers are typically very inefficient for the low mass flows associated with small engines. Due to its unique characteristics, a pressure wave supercharger (PWS) can avoid many scaling-related losses. This project designed a small-scale PWS for turbo-normalization of a Brison 95 cc two-stroke engine for a small unmanned aerial vehicle. A larger PWS called the Comprex®, designed by Brown Boveri Company, was simulated using a quasi-one-dimensional Computational Fluid Dynamics (CFD) code developed at the NASA Glenn Research Center.