Fuel Preparation in Port-Injected Engines

Heat-transfer data are reported for stoichiometric air/fuel sprays impinging on heated intake valves. The fuels used were gasoline, ethanol and methanol. Measurements were made with stationary and oscillating valves at three air flowrates corresponding to idling, light and medium load conditions. A range of inlet valve temperatures was explored with coherent and diffuse fuel sprays targeted on the centre of the valve. The effects on heat transfer of incorrect targeting of the fuel sprays were also measured. Finally, with the oscillating valve, measurements were made with various injection timings.

Almost complete fuel evaporation was achieved at light load conditions using gasoline as the fuel and valve temperatures in the range 100-200°C. Injecting fuel on to a closed inlet valve, particularly when valve temperatures were high, gave higher heat-transfer rates than injecting on to an open valve. With the alcohol fuels, although heat-transfer rates at the valve surface were increased relative to results with gasoline, the proportion of the fuel evaporated was reduced as was the effect of injection timing.