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Preliminary IAE. Research Dispels Producer-gas Doubts

20th February 1942
Page 35
Page 35, 20th February 1942 — Preliminary IAE. Research Dispels Producer-gas Doubts
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Groundwork of Facts Established for One Plant with One Fuel and One Compression Ratio

RAUCH_ producer-gas data, valuable Min itself, whilst corroborative, tub, of other people's experinterits; has been obtained. by the Automobile Research Committee of the InStittition.,of Auto mobile e and now apPears in the form 'of a 'report itt the: February issue of: the Institution's journal. It may well be used as a standard , by ' which • to Judgefurther investigations and performances in actual service. •

• There can be no doubt that the work the committee has done, on this occasion, " has been thorough rind

punctiliously carried. out. It .is, course, necessary to lay a foundation. which , is. Solid and reliable, before beginning to build up any eort of structure, and one feels that what has so far been effectedconstitutes such a basis. The experiments have been Iiinited in their scope, have broken little if any new ground, but have probably proved conclusively, many results at which other investigators have in the past arrived, although with probably lees certainty.

'Plans for Future Explorations

Dr. E. Gillen, the director of research, points out in a foreword to the report that the investigations -are being continued and their scope widened, and Mr. J. Spiers, the author, concludes the report by stating that the following points would appear to merit further • stady: Higher compression ratios (7 to 1" was the highest used in the trials), supercharging, other fuels (only anthracite was employed) and conversion of compression-ignition engines. "We suggest that to this list might be added investigations with other types of producer and gascleaning apparatus, for the committee has so far confined its attentions exclusively to the " emergency " producer, Which is admitted to be of low efficiency, and was designed originally primarily for simplicity and ease of manufacture.

Summariiing the conclusions arrived at, Mr: Spiers states that the best output obtained on gas was only 53 per cent, of that on petrol, adding that it might fall as low as 40 per cent.; that the best mixture calorific value was 60 per cent. of that of the petrol-air mixture; that volumetric efficiency was 12 per cent. lower,,. and that indicated therenal efficiency was higher, detonation being' absent even with greatly advanced ignition timing. He adds that an increase of compression from . 6 to 1 to 7 to 1 gave a 15.5 per cent, rise in power.

Experiments with petrol assistance showed that some recovery of power results from improving mixture calorific value by adding petrol, but, without rise of compression, over 90 per cent, of the original petrol consumption is required for 100 per cent. recovery. With 7-to-1 compression, 72-84 per cent. sufficed.

Trials with a wet blast, which were carried out by ,introducing, steam into the producer, showe'd no improvement in mixture calorific value or in power.

Examination of • deposits on tle cylinder heads revealed the presence of. nearly 60 per cent, of silicon. ThiS would be ,expected, to cause abrasive wear of the bores and measurements showed this to be high. An average "figure quoted is 0.0034 in. after 110 hrs. 21 mins. running: No, lubricating oii troubles were experienced, "

Much interest attaches tO the Various graphs included in the. report, which have obviously been plotted in, pains, taking manner from the readings obtained in many a long series of tests. One of these contains a curve showing the gradual fall of power over a period of running determined by the capacity of the producer. On it, also, are nine other curves showing respectively the spark advance over the time taken to consume the producer-full of fuel, the drop in manifold pressure, the fairly constant volumetric efficiency, the gradual falling off (after an early rise) of Mixture calorific value, the falling rate of air flow and rising rate of gas flow, and the increases in temperature at the cooler outlet (big), filter outlet (medium) and engine inlet (small).

Gas Changes with Fuel Consumption

Tieing up, to some extent, with this graph, is another of special interest, showing gas composition and calorific value against running time. The carbon-monoxide curve steeply rises at the outset, levels at about 30 per cent, volume after roughly 75 per cent, of the fuel has been consumed, and then drops to 25 per cent. The hydrogen curve starts at 18 per cent., -peaks at 20 per cent., drops very steeply after only 10 per cent, of the fuel has been burned, and then* tails off to about 2 per cent. at the end.

The carbon-dioxide curve begins at 6 per cent., falls quickly, and gradually rises again, whilst that for methane peaks at 24 per cent. after 10 per cent

of the renning lime andfalls slowly to under I per tent.. '

On this graph the calorific-value • curves for gas 'and. mixture, respectively, both rise, steeply at the outset

with the increases in volume of the three useful gases, and then fall off •' steeply after 10. Per cent. of the fuel • has been burned, being sustained, _ however, to a material extent by the rising .earbon-monOxide content.'

This This graph is repeated with fuel comprising,' instead of wholly new anthra cite, a,. 50-50 mixture of new and

bottoms," that is, the fuel that is left in the bottotn of -the producer after the effective charge has been consumed. ' As would be eXpected it Shows lower contents of H and CH4., .

. Then . there are,graphs showing the relation' between hYdrogen content and OptiMum ignition advance, showing

i,h.p. and b.h.p., -together with various System 'depressions, a-gairist rp.m., for petrol, new anthracite' and new mixed with bottoms, and indiating efficiencies for gas With t-o' ctunpression ratios, compared with petrol, at varying

Gas and Petrol Efficiencies Compared Mechanical efficiency with gas is lower than with petrol, because the output is less. Volumetric efficiency with gas is considerably inferior through the greater manifold depression and the lack of evaporative cooling. Indicated thermal efficiency, as already mentioned, is higher.

Trials taken to enable curves to be plotted.' showing M.E.P. against mixture strength, iudicated greater sensitivity, to correct mixture on the part of gas, particularly on the " rich " side.

There are also power-speed graphs and others showing various results of adding petrol to the mixture.

• One section of the report deals with flexibility. The tests seem not exactly encouraging. One of them consisted of running the engine at full 'load and at 2,500 r,p.m., then throttling it back to no load at 1,000 r.p.m. for periods ranging from 2 to 15 mins., and then opening the throttle again.

Generally the result was that the time required for 90 per cent, of the full power to be restored was roughly proportional to the length of the' throttled period. After 5-min. periods quick responses were obtained with air-control adjustment. , After 10-15min. periods the engine stopped if the throttle was quickly opened, but could be nursed back to steady running, in some 10 mins., with eareful manipula tion of the controls.

Whilst the Institution is to be congratulated on having accomplished this excellent ground work and produced so much sound basic data, we look forward to the results of its further investigations and its publication of some really new information.


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