GAS TURBINE ENGINE

Te Awamutu Courier, Volume 73, Issue 6284, 23 September 1946, Page 7

GAS TURBINE ENGINE

NOT ADAPTABLE TO MOTOR VEHICLES MORE RESEARCH NEEDED The recent success by a British jet-engined “Meteor” ’plane at bettering its own world’s speed record of 606 m.p.h., and the publicity that has arisen from the effort, adds further zest to the question that has already aroused considerable interest m automotive circles as to whether there is any probability of the gas turbine eventually displacing petrol and oil engines for road transport vehicles. Some experts say definitely “No” at the present time, protected by a saving clause to the effect that with the extraordinary speed of scientific progress to-day, some radical change in general design and system of working of the gas turbine may eventually bring it into the automotive field. One startling fact about the gas turbine is that it actually has to develop from 50 to 75% more power than is eventually made available as useful driving energy. In other words, the compressors, perhaps the most important part of the plant, absorb from 50 to 75% of the total output to enable the engine to deliver the. remaining 25 to 50% as useful energy. As regards thermal efficiency, from what has been seen of the gas turbine, it does not appear probable that it will ever be able to compete with the 40% thermal efficiency of the modern diesel oil engine. Then again, the big temperature of the high pressure turbine inlet, which reaches about 1230 degrees Fahr, would, it is believed, entail a whole series of new problems in any attempt to apply the principle to road transport vehicles. However, it is of interest to cite what aeronautical engineers claim for the gas turbine. Simplicity of construction makes it cheaper to construct, less liable to mechanical breakdowns and easier to service than the “piston” engine. The absence of reciprocating parts reduces vibration and practically eliminates loss of power due to mechanical friction. Cheaper fuels can be used, and it gives much greater power in proportion to weight. No doubt these claims are mostly based on data gathered from the design and performance of the two Rolls-Royce “Derwent” engines used in the record Gloster “Meteor.” When flying at 606 m.p.h., each’ engine was producing the equivalent of 10,000 H.P. No piston engine has ever approached this horsepower. The “Derwent” engine, with its enormous power output, weights only 1250 lbs., which is actually about 400 lbs. less than a modern six cylinder 100 H.P. diesel type oil engineDespite the wonderful compactness, output and power to weight ratio (8 H.P. per lb.) of the “Derwent,” there appear to be sound reasons why this type of power unit will not be adapted to motor vehicles. According to Mr W. H. Goddard, a leading English automotive engineer, they are:—

(1) Poor thermal efficiency, and consequently bad fuel consumption. (2) The extremely high temperatures which are necessary in the gas turbine would be quite impracticable in a road vehicle. (3) The impossibility of designing a reduction gear capable of dealing with the huge gap between the necessarily high speed of the turbine shaft and the comparatively low speed required for the rear axle of a vehicle. (4) Gas turbines would have to be far too small to be successful; the difficulty with turbines is to get the power down. (5) The impossibility of being able to control the speed within the somewhat exacting range, i.e., quick stopping and starting* and accelerating.