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The combustion in a spark ignition engine was studied when it was fueled by neat methanol using the timed injection method at the intake port. The measurements from this fueling were compared with those obtained from a carburetor fueled operation. In the study, results of the cylinder pressure analysis and the in-cylinder high-speed photographic observation showed that the reaction in the timed methanol engine combustion had multiple-stage combustion processes. The multiple-stage reaction was pronounced based on the double spikes in heat release history and droplets individually burning in the mixture. The injection time for the best methanol fueled engine operation seemed to be that right after the intake valve opening when the lowest specific fuel consumption was obtained with smallest cyclic variation in the pressure-time history and when the lowest emissions (NOx, UHC and HCHO) were produced.

The effects of knock with varied intensity on spark-ignition engine performance and emission characteristics were investigated using a single-cylinder CFR engine operated by several different fuels. The variation of knock under a fixed engine speed was obtained by operating the engine using different octane numbers of the fuel and the variation of fuel's octane number was made as follows: For gasoline, two fuels having different octane ratings were used to obtain three different octane-number fuels, 85.3, 87.1, and 88.9; for gasoline/alcohol blend fuels, the volumetric alcohol contents in the blend were 0, 5, and 10% to obtain octane ratings of 85.3, 85.7 and 86.2, respectively; for natural gas (with over 94.5% methane by volume), small different amounts of alcohol were introduced into the stream of gas to produce octane numbers of 116, 118 and 120. For the same fuel, the knock intensity was stronger at lower engine speed and lower with high octane number.

A novel way of using low-cetane-number petroleum gases in a compression ignition (CI) engine is introduced, by directly injecting blends of such fuels with dimethyl ether (DME), a high-cetane-number alternative fuel for low soot emissions. This method both extends advantages of DME and complements its deficiency. Although DME mixes with most hydrocarbon fuels in any ratio, in order to demonstrate the feasibility of the new method and facilitate the analysis, DME-propane blends were investigated in a direct injection CI engine. Some findings of the study are listed. In the engine operated by DME and propane blends, there was no need for significantly increasing the complexity of the fuel system than that employed in the use of neat DME. For the same reason, this method eliminates or minimizes cumbersome hardware necessary when the said gaseous fuels are separately introduced in CI engines.

A single-cylinder direct-injection (DI) Diesel engine (Cummins 903) equipped with a new laboratory-built electronically controlled high injection pressure fuel unit (HIP) was studied in order to evaluate design strategies for achieving a high power density (HPD) compression ignition (CI) engine. In performing the present parametric study of engine response to design changes, the HIP was designed to deliver injection pressures variable to over 210 MPa (30,625psi). Among other parameters investigated for the analysis of the I-IPD DI-CI engine with an HIP were the air/fuel ratio ranging from 18 to 36, and intake air temperature as high as 205°C (400°F). The high temperatures in the latter were considered in order to evaluate combustion reactions expected in an uncooled (or low-heat-rejection) engine for a HPD, which operates without cooling the cylinder. Engine measurements from the study include: indicated mean effective pressure, fuel consumption, and smoke emissions.