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This paper describes a computer simulation of Diesel spray formation and the locations of self-ignition nuclei. The spray is divided into small elementary volumes in which the amounts of fuel and fuel vapours, air, mean, maximum and minimum fuel droplet diameter are calculated, as well as their number. The total air-fuel and air-fuel vapour ratios are calculated for each elementary volume. The paper introduces a new criterion for determining self-ignition nuclei, based on assumptions that the strongest self-ignition probability lies in those elementary volumes containing the stoichiometric air ratio, where the fuel is evaporated or the fuel droplet diameter is equal to or lower than 0.0065 mm. The most efficient combustion in regard to consumption and emission will be in those elementary volumes containing stoichiometric air ratio, and fuel droplets with the lowest mean diameters. Measurements of injection and combustion were carried out in a transparent research engine.

The paper deals with the optimisation process of existing engines and the compilation of data to allow future electronic control of fuel injection. The general trend is towards the development of high-pressure electronic injection with injection pressures exceeding 1500 bar and with the reduced injection timing. We based our research measurements of diesel engine on the above assumptions. The measurements were undertaken on an engine tester by means of an analyser, charge amplifiers, a needle lift transducer and pressure measuring sensors. Using the measuring instruments we measured the needle lift, injection pressures in the nozzle, combustion pressures, fluctuations of pressure in the charge and exhaust ducts in relation to the crankshaft angle,crank revolutions per minute, preinjection angle and engine loading. Moreover, we measured the fuel consumption, the temperature of cylinders and bridges between valves in the engine.