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Time-averaged combustion chamber surface temperatures and surface heat fluxes were measured at three locations (one in the antechamber and two in the main chamber) on the head of a single-cylinder, divided-chamber diesel engine. In general the surface temperature and heat flux were found to increase with increasing engine speed, fuel-air ratio and intake-air temperature, decreasing coolant temperature and advancing combustion timing. At motored conditions the highest heat flux was at the antechamber location. This was caused by the high swirl flows present in the antechamber. In contrast, at all other conditions the highest heat flux was measured at the location in the main chamber near the valves. This was attributed to the convective action of the high-temperature stream of combustion gases exiting the antechamber during the expansion stroke. Lastly, the local surface heat flux measurements were correlated in terms of the air and fuel consumption rates of the engine.

In this study, the performance and emissions characteristics of an uncooled, thermally insulated diesel that utilized an optimized injector-tip configuration are examined. When the uncooled engine was compared to a conventional water-cooled engine at the same brake power and airflow, the uncooled engine had equal or superior fuel consumption, significantly higher nitric oxide emissions, and significantly lower smoke and particulate emissions. The dramatic reduction in smoke emitted by the uncooled engine was not observed in studies reported earlier. This smoke reduction is attributed to the high gas temperatures and increased rates of air-fuel mixing that augmented the rate of oxidation of the soot particles when the injector tip was optimized for the uncooled engine and airflow was adjusted to match that of the cooled engine. Heat-release analyses showed that the uncooled engine had less premixed combustion and significantly shorter combustion duration than the water-cooled engine.

In this study, the effects of engine speed, air-fuel ratio, combustion timing, intake-air temperature, and coolant and oil temperature on exhaust gaseous emissions (nitric oxide, carbon monoxide and hydrocarbons) and particulate emissions (particulates, volatiles and smoke) were investigated in a single-cylinder, divided-chamber diesel engine. In addition, the trade-off behavior of the pollutants was investigated. To aid in the interpretation of the experimental findings, a single-chamber, single-zone heat release model utilizing experimental main-chamber pressure-time data was employed. The large increase in nitric oxide emission index caused either by increasing the air-fuel ratio or by advancing the combustion timing is attributed to the proportionally larger amounts of fuel that burn at near TDC conditions.

A two-stage heat-release model was developed and applied to both a divided-chamber and an open-chamber diesel engine to determine the fuel burning rates and product temperatures from measured cylinder pressure-time profiles. Measured NO emission levels for several engine operating conditions were used to select the equivalence ratios of the two stages. Combustion in the first stage was taken to occur at a stoichiometric air-fuel ratio, while second-stage combustion was considered to occur at an equivalence ratio below the cylinder-averaged equivalence ratio. An empirical fit for the equivalence ratio of the second stage was determined. Good agreement between the results of this model and the corresponding single-stage model was obtained for heat-release and heat-transfer histories. The computed combustion temperatures for the rich stage were found to be consistently higher (7 to 22% on an absolute scale) than published flame-temperature measurements.