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Measurements are reported of heat transfer to a number of non-aqueous liquids that may be used as high temperature engine coolants. Included are engine lubricating oil, propylene glycol and LP 1693. The measurements were made with the coolants flowing at velocities ranging from 0.5-5 m/s in ducts similar in geometry to those employed in cylinder-heads and engine blocks. Heat fluxes up to 100 W/cm2 were used. For most tests the pressure drop across the test section was held constant but a number of tests are reported for constant coolant flowrate. The heat-transfer data obtained are shown to be in good agreement with predictions from the Chen correlation for flow-forced, sub-cooled nucleate boiling. This model is used to evaluate the heat-transfer performance of other non-aqueous coolants, namely ‘Thermex’ and ethylene glycol.

An experimental, fuel-vaporization system has been designed and installed in the intake systems of three port-injected, gasoline engines. Baseline, cold-start testing was undertaken using manufacturers' calibrations, where appropriate, in conjunction with standard, production fuelling systems. When vaporized fuelling was used, fuel enrichment was reduced to the lowest levels consistent with stable operation. In some cases this was achieved by altering the input signals to the engine's control unit; in other cases a programmable fuelling control system was used. This paper presents details of the design of the fuel prevaporizers and the operating temperatures and power consumption required to achieve complete fuel evaporation. Reductions in HC emissions which can be achieved by using prevaporized gasoline during cold-cranking and warm-up phases of engine operation are also reported. The response of the fuel prevaporizer to sudden changes in fuel flow has also been investigated.

The Vapipe is a device that has been developed jointly by Shell Research Limited, Thornton Research Centre, and the National Engineering Laboratory to reduce car exhaust emissions and improve fuel economy. It achieves better mixing of the charge entering the engine by vaporizing the gasoline in the inlet system. Heat for this purpose is conveyed from the exhaust system by means of a heat pipe. The heat pipe must be designed to cater for the possibility of gross mismatch between the heat available from the engine exhaust and the heat needed to vaporize the fuel. This can occur under transient conditions of engine operation. Two Vapipe systems have been tested, one in which surplus heat from the exhaust is rejected to the cooling system of the car and the second in which the boiler efficiency is varied to maintain the correct flow of heat to the fuel vaporizer. Both systems operate well but the latter is very much cheaper to make than the former.

The distribution of air mass flowrate between the cylinders of a 4-cylinder, carburetted automotive engine has been measured using a propane injection technique. The results show that over a wide range of operating conditions the engine has acceptably uniform distribution of air flow. At low- and medium-speed conditions the insertion of quite large obstructions into individual limbs is shown to have little effect on the air mass flows through these limbs. Only at high engine speeds and loads do these resistances have significant effect. The measured data are compared with corresponding predictions from a computer model of the engine and good agreement is shown.

A four-stroke, spark-ignition engine is described that seeks to achieve high expansion ratio and low throttling losses at light load, whilst retaining good knock resistance at full load operation and without the need for expensive mechanical changes to the engine. The engine does, however, incorporate a second inlet (transfer) valve and associated transfer port linked to the intake port. The timing of the transfer valve is different from that of the main inlet valve. Load modulation is achieved by control of the gas outflow from the transfer port. A computer model of the engine is first validated against measured data from a conventional engine. Comparisons are made of incylinder pressure at part load conditions, total air flowrate through the engine and intake port air velocities as a function of crank angle position.

Measurements of heat transfer to water/ethylene glycol mixtures are reported for a range of coolant velocities (0.1 to 5.5 m/s) and heat fluxes (up to 140 W/cm2). At the highest velocities (3 and 5.5 m/s) forced convection was the dominant mode of heat transfer. At lower velocities, however, strong nucleate boiling occurred and at the lowest velocities dryout or vapour blanketing of the test section was detected. For most of the tests reported the pressure drop across the test section was held constant and the coolant flowrate adjusted accordingly. A number of tests are, however, reported for conditions of constant flowrate. The heat-transfer data obtained are shown to be in good agreement with a heat-transfer model that allows for forced convection and nucleate boiling.