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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.

In an effort to obtain a better under-standing of the mechanisms leading to the presence of unburnt hydrocarbons (uHC) in the exhaust gases from automotive gasoline engines, a fast-response, flame ionization detector has been deployed in the exhaust port of a firing engine. The detector used has a response time of approximately 1 ms and so was able to follow changes in uHC concentration levels during the exhaust stroke. After checking that the signal from the detector was not corrupted by pressure or temperature excursions in the exhaust port, the instrument was used to record uHC emissions signatures at various stations in the exhaust port of a single cylinder engine. Measurements were made at intervals of 2 degrees of crankangle movement (CA) during steady-state engine operation at 2000 r/min, 2 bar bmep. The shape of the uHC versus CA signature was found to change as the probe sampling head was moved downstream from the exhaust valve.

Equations describing the transient behaviour of air and liquid fuel in the intake system of port injected engines are used to predict firstly the variations in air/fuel ratio and ultimately the variations in engine torque that result from rapid throttle openings. Corresponding values of measured and predicted data are compared over a range of conditions and show that the model predicts essentially the correct trends.