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This four-stroke engine study examines how micro-chamber generated radicals can facilitate the robust control of autoignition in direct-injection (D.I.) diesel engines. These internally produced radicals enable combustion under much lower than normal diesel compression ratios (CR's) and temperatures and make the chemical-kinetics control of autoignition timing a reality. In an attempt to better understand the mechanisms enabling radical based chemical control, the altered chemistry of radical ignition is studied numerically for the case of H 2 combustion. Numerical simulation is based on a detailed mechanism involving as many as 19 species and 58 reactions. This H 2 chemical-kinetics mechanism is simultaneously solved within two separate but connected open systems representing the distinctive main-chamber and micro-chamber processes (Figure 1). During the combustion cycle these two open systems continuously interact, passing energy and chemical species between one another and the atmosphere while attempting to equalize pressure differences.

Comparison is made of the nonsteady combustion and flow processes predicted by the method of characteristics for time dependent compressible flow in a heat balanced engine with photographic records of combustion flow fields observed by high speed Fastex Schlieren and holographic interferometry. Pressure exchange and the accompanying mass transport are demonstrated analytically and observed optically. Qualitative agreement between the initial top dead center calculation and photographic evidence is seen. Schlieren and interferometer records give typical combustion flow field interactions through all strokes of an operating four stroke glass walled two dimensional engine. At least four models of time dependent combustion are identified over the entire power stroke and the influence of geometry on the control of combustion chamber pressure and temperature is discussed. (Author)

The heat balanced or combined cycle engine with time dependent combustion sustained by two chamber geometry is demonstrated experimentally. Evidence of time dependent heat addition is given where combustion creates a field of pressure waves sustained by pressure exchange between two chambers. The basic cycle and operating characteristics are reviewed and experimental results with CFR and glass-walled engines demonstrate the engine characteristic as compared to OTTO engines. Improvements in thermal efficiency over the OTTO engine in excess of 45 percent are demonstrated in some operating regimes. Considerable reduction in peak pressure and exhaust emission is also demonstrated.