HIGHLY TURBOCHARGED SMALL AUTOMOTIVE DIESEL ENGINES.

A proposal in outlined calling for the turbocharging of a small automotive four-stroke four-cylinder diesel engine capable of developing approximately 15 kW (20 bhp) naturally aspirated, so that it can develop up to 2 one-half to 3 tunes that power when required. A maximum of 45 kW (60 bhp) is considered representative of the popular size European car. Assuming a bmep of 686 kN/m**2 when the engine is producing 15 kW (20 bhp) (full power under naturally aspirated conditions) at 3000 rev/min, the calculated bore and stroke are 62. 5 mm and 69. 5 mm, respectively, resulting in an engine capacity of 0. 85 liters; the mean piston speed is 6. 9 m/sec at the rated speed. The turbocharger would consist of a radial-flow turbine utilizing the energy in the exhaust gases; the flow rate of gas to it would be controlled by means of a bypass valve in the exhaust gas duct. The compressor would be of the centrifugal type, running at speeds of around 100,000 rev/min. It is estimated that, at the least, a 50% improvement in efficiency in comparison with a gasoline engine should be readily attainable, and possibly as much as 60%, since it is expected that for urban driving the thermal efficiency will be 20-25%, as compared with only 10% for the gasoline engine. Also, there is the additional advantage of a reduction of pollution.