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The impact of minutely oxygen-enriched air on spark-ignition (SI) engine combustion was studied by obtaining engine performance measurements and investigating in-cylinder reactions. This study was initiated to determine if development of a new air-cleaner method, which may employ molecular sieve or membrane technology to slightly increase the oxygen concentration in the inducted air, is beneficial for engine operations. The air introduced into a single-cylinder SI engine was added with oxygen to produce oxygen concentrations of 21, 22 and 23%. Some results from engine tests performed with the oxygen enrichment are: The heat release lag, cycle variation and combustion period decreased; substantial reduction of emissions of unburned hydrocarbon emission and noticeable decrease of carbon monoxide were observed; and the brake thermal efficiency and engine output increased.

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.

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.

The flame propagations in the very first firing and subsequent cycles in an SI engine during cold start were studied to gain a better understanding of reaction fronts associated with liquid fuel (regular unleaded) in the cylinder. This work was performed using the Rutgers high-speed spectral infrared digital imaging system on a single-cylinder engine with optical access. The engine was mounted with a production engine cylinder-head mated with a conventional port fuel injection (PFI) system. In the study, four images in respective spectral bands were simultaneously obtained at successive instants of time during the combustion period, which was done for eight sequential cycles. This multiple-band successive-imaging was repeated in intervals of about two minutes over a period of more than twenty-five minutes after the engine start. During this experiment, the temperature changes at the intake port, the water jacket and the exhaust gas were monitored.

In-cylinder flame propagation and its impact on thermal characteristics of the combustion chamber were studied by using a new high-speed spectral infrared imaging system. In this work, successive spectral IR images of combustion chamber events were captured while varying several parameters, including fuel/air, spark timing, speed, and warming-up period. Some investigation of cyclic variation, knock, and high-temperature components during the non-combustion period was also conducted. It was found that the spectral images obtained in both short and long wavelength bands exhibited unique pieces of in-cylinder information, i.e., (qualitative) distributions of temperature and combustion products, respectively. During the combustion period, the temperature of early-formed combustion products continued to increase while the flame front temperature, e.g. near the end gas zone, remained relatively low.

In-cylinder reaction processes in a production port-fuel-injection (PFI) spark-ignition engine having optical access were visualized using a high speed four-spectra IR Imaging system. Over one thousand sets of digital movies were accumulated for this study. To conduct a close analysis of this vast amount of results, a new data analysis and presentation method was developed, which permits the simultaneous display of as many as twenty-eight (28) digital movies over a single PC screen in a controlled manner, which is called the Rutgers Animation Program (RAP for short). The results of this parametric study of the in-cylinder processes (including the period before and after the presence of luminous flame fronts) suggest that, even after the engine was well warmed, liquid fuel layers (LFL) are formed over and in the vicinity of the intake valve to which the PFI was mated.

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.

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.

Engine combustion behaviors were investigated when the mixture condition at the intake port was varied. This experimental study was performed for several engine variables including types of cylinder head (gas motions), spark plug loction and MBT timing. Among the variables for the mixture condition at induction were the fuel/air mixture ratio (excess air factor) and the portion of atomized liquid fuel out of total fuel in the mixture. The engine operation was analyzed by obtaining the mean effective pressure, thermal efficiency, heat release history, stability of combustion, and lean misfire limit.

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.

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.