The Oil Engine
Page 49
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Road Transport
ENTITLED "progress in the Application of the Diesel or Heavy Oil Engine to Road Transport" was a paper recently read by Major W. H. Goddard, A.M.I.Mech.E., before the members of the Diesel Engine Users Association, in London. This paper sums up the progress that has been made in the past 2i years with regard to the development of the, oil engine, and it constitutes a useful work of reference.
No purpose will be served by the'summarization of the paper, as the details embodied in it have, in the main, been published in our pages during the period in question, but certain facts may well be emphasized in regard to it.
Prominent amongst the prime-movers referred to is the Gardner engine, which has achieved considerable success. It is, of course, a marine-type direct-injection engine, which weighs approximately 22 lb. per b.h.p. in the case of the sixcylindered type. This engine, of course, does not carry electric starting equipment, the weight ofwhich amounts to approximately 24 cwt. in the case of some other oil engines.
In his paper Major Goddard states that there has been found to be little or no dilution of the crankcase oil, which tends towards a longer life for the stuffing parts than in the case of petrol engines. He claims longei life for oil.engines on account of their low crankshaft speeds, a low working temperature, a smoother expansion _stroke than in the case of a petrol engine, arid less:
violent changes in the temperature of the cooling water.
At several points the author emphasizes the need for limiting engine speed. During the discussion following the reading of the paper a large number of speakers criticised this point, emphasizing the need for a good rangesof topgear performance. An interesting point is that a 75 b.h.p. oil engine, when supercharged, has, under test, produced 150 b.h.p. with a slightly better consumption than when working normally on full load.
The advantages of supercharging were referred to by several speakers, and, as has been the case at similar previous gatherings, a bright future was predicted for the supercharged engine worlsint upon the two-stroke cycle, During the discussion Mr. Tookey laid emphasis upon the fact that progress in the development ef the oil engine will be in direct proportion to the advancement made in respect of the fuel pump and combustion-chamber design. He, said that in every respect the oil engine has a better prospect than the petrol engine. As a prevention of dribbling from the fuel nozzles, governing the pump on the suction side, as opposed to the pressure side, might be found to be a fruitful field flu. investigation.
Another speaker, referring to the tendency of high-speed oil engines to have power curves -which flatten above about 1,500 r.p.m., suggested that research should be made with regard to the duration of injection. Variation in the number of degrees of crank angle during which injection takes place might, he said, be responsible for a considerable variation in the output.
One or two persons were of the opinion that a low weight-to-power ratio did not merit such serious attention as others had paid to it, but it was pointed out that axle-weight restrictions are more likely to become keenly enforced than hitherto, and that, in this direction, there is little prospect of regulations being eased.
One speaker referred to a recent steam development in regard to boat propulsion, saying that a figure of 15 lb. per b.h.p. had been obtained and that there was a prospect of this being still further reduced. The fuel consumption of this new steam plant -worked out at .6 lb. of oil per b.h.p.-hour. This pro= gress, `he said, showed" that the oilengine manufacturer must not relax his attention in the direction of reducing weight.
For -road use there are other considvations besides the weight of the power unit ; for example, its bulk must
be taken into account. The fact remains that any increase in the weight of the engine reduces the pay-load.