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Development progress of the unthrottled direct injected Stratified Charge Rotary Combustion Engine Program at the Curtiss-Wright Corporation is updated since the 1974 status reported in SAE Paper 741206. Emphasis during this period has been on performance improvements in the automotive road load range. Results are given for a number of variations tested since that date, including engine performance with gasoline and other fuels. The baseline configuration has been further improved and new designs which have improved fuel consumption and reduced hydrocarbon emissions are described in the paper. These data are presented showing steady-state SFC equal or better than representative automotive diesel engines; comparable untreated emission data are presented with HC emissions reduced to a representative band level of automotive carbureted engines and with relatively low CO and NOx.

The paper covers exploratory development of the Rotating Combustion (RC) engine spark ignited stratified charge versions since 1966. Configuration improvements resulting in increased power and reduced fuel consumption are described and test results cited. Exhaust emissions are presented, with and without a catalytic converter, and compared with carbureted RC engine results as well as limited diesel engine data. It is concluded that the technical bases for an efficient, lightweight, economic, low-emission powerplant capable of broad range operation have been demonstrated. Weight and displacement parametric curves are presented for one family of advanced higher speed engines.

The Curtiss-Wright RC2-60 engine exhaust emissions were measured, with and without an exhaust reactor, under steady-state conditions at the University of Michigan and in a vehicle operated on the simulated California cycle at an independent facility. The reactor successfully reduced the emission levels in both cases. Data are presented for the steady-state trends of engine emissions as a function of engine performance variables; trends are generally similar to those of conventional gasoline engines. The particular effectiveness of an exhaust reactor with the RC engine is attributed to port characteristics and higher exhaust gas temperatures unique to this engine together with new reactor design features. Theoretical considerations and future investigations are discussed.

Engine dynamometer testing was conducted on a production automotive engine. Untreated exhaust emissions were measured over a range of hydrogen/natural gas fuel mixtures and equivalence ratios (Φ). The most important finding was that, with retarded ignition, extremely low raw NOx emissions can be attained at the same time as high brake thermal efficiency. With a 30% hydrogen mixture and Φ = 0.65, the effect of spark timing on engine efficiency is almost negligible over approximately 15° of crankshaft rotation. For an engine load of ∼400 kPa, brake thermal efficiency remained at 30%. NOx emissions can be kept below 0.05 g/kWh for bmeps up to 500 kPa and rpms above 1700, with low hydrocarbons and minimal effect on fuel economy.