Advantages of Turf) ocharging
Page 47
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A DVANTAGES resulting from using r—k large-capacity engines running at reduced loadings could also he derived from turbocharging, Mr. E. Kellett, of the B.S.A. automotive and research department, told the Automobile Division of the Institution of Mechanical Engineers at Coventry on Tuesday. The co-author of the paper he presented was Mr. C. A. Judson.
When an 8,Hitre engine of the normally aspirated type was specified, some operators preferred to use a 9,litre unit, but, as a further alternative, a turbocharged 6-litre engine could he employed. Mr. Kellett claimed that the fuel-consumption rate of the smaller turbocharged engine would be some 12 per cent. better than that of the larger types.
Capacity of the basic engine could be reduced by re-sleeving, and the change in the bore-stroke ratio would he advantageous.. Life of such an engine would match that of a normally aspirated 9,?I itre engine.
hialifax Transport Department had tested an 8.6-litre turbocharged engine against a normally aspirated 10.6-litre unit. On hilly routes, the smaller type returned a saving in fuel consumption of only 4 per cent., brut on flat routes the improvement was 19 per cent.
Vibration developed by a turbocharger at about 36,000 r.p.m., a speed which corresponded to the deflection of the rotor bearings, could be eliminated by mounting the bearings in silicone-rubber rings.
Referring to the application of inter
cooling with a water-to-air heatexchanger to an engine developing 180 h.h:p. at 1,100 r.p.m., Mr. Kellett said that 65 per cent, cooling provided at low speeds and 35 per cent. at high speeds were relatively small. More effective intercooling was possible with an air-toair heat-exchanger, the use of which could give a worthwhile improYement iii fuel consumption.
It should be possible to accommodate an intercooler of this type on a vehicle. A unit for an engine of the type mentioned would be about 1 ft. 6 in. square and 6 in. deep. At the same meeting, Mr. D. W. Tryhorn, of the British Internal Combustion Engine Research Association, read a 'summary of his paper, " An Approach to the Problem of Pressure Charging the Compression Ignition Engine," and the discussion included comments on both papers.
The value of supercharging as a means for saVing. fuel was mentioned by a number of_ speakers as the greatest merit of the system.
After stating that flow losses in a supercharged engine should be reduced, Mr. Tryhorn pointed out that any flow of air through the inlet valve after bottom dead centre represented a waste of power. I-le also claimed that mounting the positive type of supercharger a relatively long distance from the manifold could enable the air to be substantially cooled without a heat exchanger.
Mr, Kellett emphasized that a turbocharger should be located as close as possible to the exhaust valves.