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To examine the effects of exhaust gas recirculation (EGR) on the exhaust emissions and on the cycle-by-cycle variation of combustion process in a methanol engine, the authors have tried to measure the emissions of total hydrocarbon, carbon monoxides, nitric oxides and formaldehyde and to record the cylinder pressure development histories of 1000 cycles duration. Moreover, the standard deviation of peak pressure Pmax, the heat release rate and the averaged pressure history are analyzed. The results are compared with those of gasoline fueled operation.

The engine performance, combustion characteristics and exhaust emission of pre-chamber type compression ignition engine operated by various biomass fuels were investigated experimentally. The biomass fuel investigated in this report are an emulsified fuel made with gas oil and hydrous ethanol or hydrous methanol, an emulsified fuel made with hydrous methanol and rape-seed oil, and neat rape-seed oil, and gas oil. There are small deviations of the experimental results between the biomass fuels, however, the general tendencies of the engine performances and exhaust gas characteristics operated by biomass fuels are as follows: The brake thermal efficiency during biomass fuel operation becomes maximum at a certain injection timing as well as those of the gas oil operation. And this injection timing is advanced with increasing the biomass content in the fuel.

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.

A direct fuel-injection two-stroke cycle engine operated with neat methanol was investigated. The engine performance, combustion and exhaust-gas characteristics were analyzed experimentally and compared for operation with a carburetor, EFI injection at the intake manifold, and EFI injection at the scavenging port. The power and the brake thermal efficiency of the direct fuel-injection engine were higher than those of engines operated with a carburetor and either of the two EFI methods. The exhausted unburnt fuel of the direct fuel-injection engine was lower than that for operation with a carburetor, and formaldehyde and the CO concentration were of the same level as for operation with the carburetor and EFI methods. The NOx concentration of the direct fuel-injection was half the level of the result of carburetor operation.

Effects of the intake air oxygen enrichment (IOE) on the combustion processes and performance of a spark ignition (SI) engine were investigated when the engine was operated under part load conditions both after and during the warm-up period. The study was performed by comparing the direct measurements of engine performance and emission characteristics with instantaneous digital imaging of in-cylinder reaction processes obtained using our high-speed dual-spectra infrared imaging system developed at Rutgers. The IOE under the partial load operations of an SI engine produced some comparable improvements in the thermal efficiency and mean effective pressure to those from the full load operations. Although no dramatic reduction of unburned hydrocarbon emissions with the IOE was realized in the present measurement, the insignificant increase of Nox under the same condition is noteworthy.

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.

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.

Visualization of in-cylinder reaction processes and performance analysis of a direct-injection Diesel engine equipped with a high injection pressure (HIP) unit were conducted. The study was directed towards evaluation of high-power-density (HPD) engine design strategies, which utilize more intake air operating at rich overall fuel-air ratios. Two separate engine apparatus were used in this study: a Cummins 903 engine and a single-cylinder optical engine equipped with the same family engine components including the cylinder head. The engines were mated with an intensifier-type HIP fuel system fabricated at Rutgers which can deliver fuel injection pressure of over 200 MPa (30,000psi). The one-of-a-kind high-speed four-band infrared (IR) imaging system was used to obtain over fifteen hundred sets of spectral digital movies under varied engine design and operating conditions for the present analysis.

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.