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Measurements of cylinder pressure and flame travel velocity have been obtained in a single cylinder engine with two arrangements of port geometry and with mixture equivalence ratios from 0.68 to 0.9. They are complemented by photographs of the flame development and measurements of local velocity. The investigation compares the combustion processes in terms of the maximum pressure, flame speed and in-cylinder flow velocity without and with an intake shroud which increased both the tumble and swirl ratios. The extent to which residual burned gas retarded the combustion rate and increased cyclic variability are quantified. The photographic studies confirm the dominant effect of the swirling flow on flame propagation and deviations of the flame kernel from spherical as the air-fuel ratio is increased, with much higher probability of influence of velocity fluctuations.

Previous measurements of the velocity, size and number density of droplets have been reported in one cylinder of a production two-valve engine as a function of position, crank angle, injection timing, rotational speed, load and cooling water temperature. In this paper, similar measurements are reported in two cylinders of the same engine, this time with four cylinders firing, and with two manifolds and injectors. They were obtained with a phase-Doppler velocimeter with measurements ensembled in relation to an optical shaft encoder. The engine was also instrumented to provide air and fuel flow rates and temperatures. The results show that most of the droplets emerge in a comparatively small region of the inlet valve and that the characteristics of the spray are important mainly when injection takes place with the inlet valve open.

The performance of a four-valve engine operating with combustion in all cylinders has been determined in terms of indicated mean-effective pressure, drivability and concentrations of unburned hydrocarbon in the exhaust gases with a stoichiometric mixture of gasoline and air and four injectors including two with air assist. In addition, size and velocity characteristics of the fuel sprays were measured with a phase-Doppler velocimeter outside and inside the engine. With operation at a steady rotational speed of 1200 rpm, the indicated mean- effective cylinder pressure and its covariance were found to be nearly constant with the initiation of injection from 150 to 600 degrees of crank angle after top-dead-centre of intake.