A New System of Air Cooling.
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Interesting Experiments which are Directed Towards the Simplification of , Engine-cooling Systems.
Mr. E. H. Morgan (for whom Messrs. Markham and Prance, of 143, Strand, W.C., are acting as agents) on Wednesday, the 28th ultimo, gave a demonstration in the workshops of lnes-Daimler, Limited, of 221, Tottenham Court Road, W. with a new and highly-interesting system of air cooling which he has invented. The cooling of an engine cylinder is undoubtedly a question about which there is a large amount of misconception. It is a fact, unfortunately, that petrol-engine cylinders must be artificially cooled to a certain extent. in order to obviate pre-ignition, and to permit of the effective lubrication of the reciprocating parts. but it is a common delusion that the cooler the cylinders of an engine are kept, the better will be its running. The truth of this matter is, however, that the hotter the engine cylinders are kept without signs of pre-ignition or faulty lubrication, the higher will be its capacity for work and its fuel efficiency_ A moter vehicle which carries a large quantity of water always works rather sluggishly until the motor and the whole of the circulating water has become fairly well warmed np. Mr. Morgan proposes to dispense with the water entirely, and, whilst still retaining the water jacket, currents of air instead of water are passed through them. in an engine specially designed for this system of cooling, the jackets might lie made of thin sheet metal and he separately attached to the castings of the working cylinders. Of course, the idea of air cooling is not by any means a new one ; it is a problem that has been more or less satisfactorily solved by motor manufacturers in America, but all aircooled systems which depend for the maintenance of the air currents on a fan are faulty, for the simple reason that the amount of air blown through the jackets is more or less proportional to the speed at which the engine is run, instead of the power developed. It may generally be assumed that it is less difficult to cool an engine when running at its highest speed, than when " lahntwing " at a low speed.
The experiments which Mr. Morgan has conducted have been carried out on a foul r-eylinder, 281t.p. Xl ihaesDaimler engine, such as is fitted into many of that maker's bits and lorry chassis ; it was not specially designed,
but taken from stock. The water I ump, however, was removed, and a number of holes drilled in the water jackets round the heads of the cylinders and the valve pockets. These holes, through which air is drawn into the jaeket, are so arranged as to direct the streams of cold air passing through them on to those parts of the with of the combustion chamber which stand in greatest need of cooling. Outlet pipes are fitted to the lower part of the jackets. These outlet pipes are connected to an ejector, and through this a current of air is induced hy the exhaust gases discharged from the special form of silencer which we illustrate by means of a diagram. This silencer. by the way, is of very simple and compact construction, and consists merely of a cylindrical shell about nine inches long by seven inches in diameter, in which is placed a drum of smaller dimensions. The exhaust pipe is secured to one end of the inner drum, and the discharged gases, after striking the blind end of the drum, rebound and escape through a number of small boles in the other end plate. The combined area of all these small holes is equal to the areal
af the exhaust pipe. The exhausti gases ultimately escape in the atmo-. sphere through the ejector nozzle.
Mr. Morgan previously to the tests on the 28th ultimo, had made a large number of experiments with this system, as adapted to tins Milnes-Daimler engine, and, although the temperature indicated by a thermometer (the end of which projected into the jacket space) was much higher than that obtaining in water-cooled engines, we are assured that no serious trouble has been experienced. The inventor has recently sought to increase the efficiency of the system by the use of a chemical composition for the purpose of coating the surface of the cylinder head and the space immediately surrounding the valves. This composition possesses the property of extracting heat from the iron and readily giving it up to the air which is drawn over it, the rate of transference of heat being much greater than when the air is drawn over the bare iron.
The temperature of the air within tile cylinder jackets, just previously to the commencement of the test, we observed was 70 degrees Fahrenheit, and three minutes after applying the load to the Prony brake (10 minutes after starting the engine), the temperature had risen to 190 degrees. Five minutes later, 240 degrees was reached, and a further 13 minutes' running caused the temperature to rise to 275 degrees.
Examination of the exhaust gases during the running showed no trace of lubricating oil, and it was remarked more than once during the test that Mr. Morgan was courting disaster by running the engine with such a small quantity of lubricating oil, especially as it was loaded well above the R.A.C. rating for horse-power. Throughout the test the engine ran with perfect regularity, maintaining a speed of about 840r.p.m., and by sustaining a load of 721b. at a distance of 31 feet from the centre of the brake drum showed that it was developing about 3811.p. After running about 35 minutes, the Prony brake band seized on to the drum, due to the lack of sufficient cooling water. After stopping the engine it was noticed that the temperature of the jackets rose rapidly to 440 degrees, and some little difficulty was experienced in restarting. When the engine was again started, the test continued with a 601b. load; as it ran at 840r.p.m., this represents 31.511.p. After a run of about 20 minutes' duration, trouble was again experienced with the brake band, and, after stopping the engine, there was another rise of temperature in the cylinder walls. This evidently had had the effect of burning the film of lubricant off the walls of the cylinders. So far as could be ascertained, there was no pre-ignition at any time during the run, but the stops, due to the seizing of the brake band, were so sudden that it was not possible to arrive at any definite conclusion regarding the efficacy of the system of cooling. Careful observation showed that the highest temperature reached during the normal running of the engine was in the region of 275-280 degrees Fahrenheit, and, although there was a sudden rise in the temperature when-the engine was stopped, the temperature was reduced to 280 degrees within a few minutes of re-starting. In a recent conversation with Mr. H. C. Burford, whose company is about to take up a manufacturing license for the system, we were assured that the many tests which he had seen had been of a most satisfactory nature, and, for this reason, we were all the more disappointed at the results of the test which we had witnessed. We believe the system is capable of development, and shall look forward to a future opportunity of witnessing a long brake test with an engine cooled in this manner.