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In-cylinder reactions of several internal combustion engine configurations were investigated using a highspeed four-spectral infrared (IR) digital imaging device. The study was conducted with a greater emphasis on the preflame processes by mutually comparing results from different engine-fuel systems. The main features of the methods employed in the study include that the present multi-spectral IR imaging system permits us to capture progressively changing radiation emitted by new species produced in-cylinder fuel-air mixtures prior to being consumed by the heat-releasing reaction fronts. The study of the Diesel or compression-ignition (CI) engine reactions was performed by varying several parameters, e.g. injection pressures, intake air temperature, fuel air ratio, and the start of injection.

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.

Neat dimethyl ether (DME), as an alternative fuel candidate for Diesel engines, was investigated by measuring primarily engine performance and exhaust gas characteristics. In addition, other responses of the engine to the new fuel were also determined at the same time, including the injector needle lift and heat release. The engine measurements with this fuel were compared with those obtained by using conventional Diesel fuel. Findings from the present work include: (1) It was necessary to add a small amount of lubricating additives to DME, if a conventional fuel injection system is employed.

Many recent publications indicate that spark ignition (SI) engines equipped with the conventional port-injection fuel system (PIF) seem to have serious fuel-maldistribution problems, including the formation of liquid layers over the combustion chamber surfaces. It is reasonable to expect that such a maldistribution is an unfavorable condition for the flame propagation in the cylinder. The in-cylinder flame behaviors of a PIF-SI engine as fueled with gasoline are investigated by using the Rutgers high-speed spectral infrared imaging system. These results are then compared with those obtained from the same engine operated by gaseous fuels and other simple fuels. The results from the engine operated by gasoline reveal slowly burning fuel-rich local pockets under both fully warmed and room-temperature conditions. The local pockets seem to stem from the liquid layers formed over the surfaces during the intake period.

Instantaneous successive spectral infrared (IR) images were obtained from a spray plume in a direct injection (DI) type compression-ignition (CI) engine during the compression and combustion periods. The engine equipped with a high pressure electronic-controlled fuel injector system was operated by using D-2 Diesel fuel. In the new imaging system used for the present study, four high-speed IR cameras (with respective band filters in front) were lined up to a single optical arrangement containing three spectral beam splitters to obtain four spectral images at once. Two band filters were used for imaging the water vapor distribution and another two band filters were placed for capturing images of combustion chamber wall or soot formation. The simultaneous imaging was successively triggered by signals from an encoder connected to the engine. The fuel injection parameters were precisely controlled and the pressure-time (p-t) history was obtained for individual sets of images.

Reduced emissions from the spark-ignition engine, when fueled by gasoline containing small amounts of MTBE, have led us to explore similar positive results in compression-ignition (CI) engine combustion by adding this oxygenate compound to Diesel fuel. This study was performed in two separate laboratories by employing the respective experimental apparatus. When a pre-chamber type CI engine was operated by using Diesel fuel mixed with several volume portions of MTBE, including 5, 10 and 15%, several positive results were obtained, as compared with those from the baseline neat Diesel-fueled operations: (1) The engine delivers overall comparable or better performance characteristics; (2) The brake thermal efficiency is higher at the advanced and late injection times; (3) Some considerable reduction of both soot and NOx emissions is found; (4) The ignition delay increases but the combustion duration decreases.

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.

Individual aldehyde (and acetone) emissions were measured from the exhaust gas of a premixed multicylinder spark ignition engine fueled with Indolene and blends of Indolene and either methanol or ethanol. The engine was operated at constant speed (2000 RPM) and MBT spark advance with fuel-air equivalence ratios (Φ) of 0.96, 0.90 and 0.82. During operation at Φ = 0.82, the engine experienced lean-limit misfiring. The DNPH method with a gas chromatographic finish was employed to obtain exhaust gas concentrations of aldehydes and acetone. Also, the methods used in the past for measuring engine exhaust aldehyde and acetone data were compared to each other and briefly discussed. Use of the alcohol blends increased the total aldehyde emission level. Formaldehyde was the largest component, exhibiting a continual increase with increasing alcohol blend level.