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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.

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.

Experiments have been performed in one cylinder of a production two-valve engine under firing conditions and quantify the velocity, size and number density of droplets as a function of position, crank angle, injection timing, rotational speed, load and cooling water temperature. 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 pressure traces, air and fuel flow rates and temperatures. The injection timings included those with open and closed inlet valve. 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.