FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1952
1952 - 0484.PDF
220 FLIGHT A LIGHT DIESEL Simple U.S. Conversion of a Flat Four DIESEL aircraft engines have appeared at intervals ever since the Kaiser's War, and a number of designs have been built in this country. The only compression- ignition engine ever to become a standard power plant on series-produced aircraft, however, was the German Junkers Jumo series of opposed-piston two-strokes, with a large blower driven from the crankshaft or by the exhaust gas to ensure good scavenging. The Jumo 204 was built under licence in Britain, as the Culverin, by the Napier Company. Now comes news of a small diesel developed by Diesel i'ower Inc., of Pittsburgh, Pa. This engine embodies a number of fea tures which render it of unusual interest, and it seems possible that, despite the development of the small gas turbine, much will be seen of the principle in the future. Probably the chief drawback to the aircraft diesel has been the heavy construction demanded by the very high peak cylinder- pressure. According to a description in Aviation Week, the DPI engine embodies an "air cell" in the cylinder head, so located that fuel does not enter it. Although, apparently, no burning can take place in the cell, the burning of fuel in the main combustion space is stated by the makers to set up "a rapid succession of power pulsations until all the oxygen formerly contained in the cell is exhausted." This controlled burning is claimed to result in much smoother running, as well as flattening the engine indicator-dia gram in a very useful manner. In order to demonstrate the practicability of the principle, Mr. L. M. Barton, president of Diesel Power Inc., speaks of it as being applicable to any lightweight aircraft engine. The company's first engine of this type is, in fact, a direct conversion of the familiar Lycoming 125-170 h.p. O-290-D flat four, as installed in the Mk5 Auster. The conversion has been made on an engine taken from a crashed radio-controlled target, and has involved no change in the basic design of the moving parts or bearings. New cylinder- heads have been substituted, and high-crown pistons fitted to raise The experimental installation of the Diesel Power Inc. engine in a Taylorcraft liaison aircraft. The generally clean appearance—resulting from the absence of any spark-ignition equipment—is remarkable. the compression ratio. The air cooling has been retained—in fact the diesel appears to run cooler than did the original engine, a specimen cylinder-head thermocouple reading being about 310 deg F, as opposed to 425 to 450 deg F with petrol and spark- ignition. The DPI engine is of approximately the same weight as the original Lycoming, but whereas the engine formerly consumed about 9 gal/hr of fuel at cruising, the DPI, burning kerosene, uses only 4I gal/hr, or, on heavy diesel oil, 3 gal/hr. The engine is at present being tested in a Taylorcraft liaison aircraft; Taylcrcraft have an arrangement with DPI by which they have exclusive use of any DPI engine up to 500 h.p. Principal data include: Bore, 4Jin; stroke, 3fin.; displacement, 290 cu in; b.h.p., 100 at 2.400 r.p.m., 125 at 2,600 r.p.m.; dry weight, 245 lb approx.; compression ratio, 14:1; fuel injection by Bosch 4-A pump delivering at 1,200 to 1,500 lb/sq in to three-hole nozzles. GAS TURBINE TEMPERATURE-SENSING UNITS EFFICIENT operation of a gas turbine demands that, wher ever the gas temperature exceeds the maximum permitted value, the temperature-sensing device shall respond with the minimum time lag. Consequently, the response-rate of this unit is of paramount importance, and yet great difficulty has been experienced in determining this factor in the laboratory, due to the impossibility of reproducing operating conditions exactly. Apparatus developed by Messrs. Dahl and Fiock, of the U.S. National Bureau of Standards, is designed to give the best approximation to the conditions obtaining in the combustion stream, the heat trans ference to the sensitive element being pri marily by forced convection. This equipment consists essentially of Principal components of the Dahl and Fiock temperature-sensing test-device. A = Sensing unit. B = Duct test-section. C=>lnconel tube. D-> Cooling-water inlet. E = Cooling-air inlet. F = Release plate. G = Cushioning spring. H = Actuating spring. a Jumo 004 combustion chamber supplied by air from a blower and provided with a device for producing rapid changes in the temperature of the mounted temperature- response unit. The efflux from the com bustion chamber is led into a straight test- section in which are three convenient in strument-mounting points. The ducting to the test-section is provided with a perfor ated baffle in order to ensure an essentially uniform temperature across the central half-diameter of the gas flow, and bends to eliminate direct radia tion falling on the instrument. Pressure, temperature and mass flow of the gas stream are all accurately controlled and measured by suitable valves and instruments. In order to obtain the maximum temperature-change rate at the test instrument, the instrument was enclosed in a vertical Incoael tube in which a flow of cold air was maintained. The mounting of this tube is shown in the accompanying cross-section of the tett- section. It will be seen that, upon operation of the release plate, the Inconel tube is plucked downwards by a spring; almost instantly the test instrument is exposed to the maximum gas temperature, while the supply of cold air is automatically cut off. In this way the sensing element at a controlled moderate tempera ture is brought into sudden and intimate contact with any gas flow within the capacity of the apparatus. This test equipment has been used to study elements encased in metal and ceramic protection tubes and elements embedded in insulating materials such as quartz and beryllia. The characteristic time (that required for the element to undergo 63.2 per cent of the total temperature change imposed) has been determined for a large number of elements when subjected both to rapid heating and rapid cooling, and the apparatus has been used to develop response periods of the order of 0.02 sec for a wide variety of thermocouples, thermistors and resistance thermometers. . NAVIGATIONAL "Burton's Nautical Tables" (5th Edition). George Philip and Son, 32, Fleet Street, London, E.C.4. Price 22s. 6d. N AVIGATIONAL tables, while hardly inspiring reading, are an essential item on many bookshelves; those of Burton, while of prime concern to mariners, are sufficiently comprehensive to warrant a mention in these pages. This fifth edition published, includes a great deal of new material to meet the demands of modern navigational techniques, while the original matter has been largely rearranged and expanded. In its present form, the publication is designed to meet the examining requirements of the Extra Master's standard for many years to come.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
