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A new engine design is evaluated using 1-D engine cycle simulation. The new design changes how force on the piston is transferred to useful torque at the output shaft. The coupling design brings with it many possible advantages including custom piston motion, variable compression ratio, extended power stroke, and reduced friction. Each of these benefits is explored individually and collectively. The actual engine exists today only in a compressed air version. A development plan is in place to build and test a fuel burning prototype in 2010. Lacking data from a firing engine, some assumptions are required in the analysis and these are documented. The engine is evaluated in this work in two forms; 1) a power stroke for every two output shaft revolutions and 2) a power stroke for every output shaft revolution. Both of these engine variations are in the development plan and both are needed to address different applications that the engine may be designed for.

Measurements of the instantaneous heat flux at three positions on the cylinder head surface, and the steady-state cylinder head temperatures at four positions on the cylinder head have been obtained. Engine tests were performed for a range of air-fuel ratios including regimes rich of stoichiometric, stoichiometric, and lean of stoichiometric. In addition, ignition timing was advanced in increments from 22° BTDC to 40° BTDC. All tests were run with the throttle either fixed in the wide open position, or fixed in a position that produced 75% of the maximum power with the standard ignition timing and an air-fuel ratio of 13.5. This was done to ensure that changes in air mass flow rate were not influencing the results. In addition, all tests were performed with a fuel mixture preparation being provided by system designed to deliver a homogeneous premixed charge to the inlet port. This was done to ensure that mixture preparation issues were not confounding the results.

Control of the flow of thermal energy in an air-cooled engine is important to the overall performance of the engine because of potential effects on engine performance, durability, design, and emissions. A methodology is being developed for the assessment of thermal flows in air-cooled engines, which includes the use of cycle simulation and in-cylinder heat flux measurements. The mechanism for the combination of cycle simulation, the measurement of in-cylinder heat flux and wall temperatures, and comparison of predicted and measured heat flux in the methodology is presented. The methodology consists of both simulation and experimental phases. To begin, a one-dimensional gas dynamics code (WAVE) has been used in conjunction with a detailed in-cylinder flow and combustion model (IRIS) in order to simulate engine operation in a variety of operating conditions. The methods used to apply the model to the air-cooled engine case are described in detail.