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Aviation History
1954
1954 - 0513.PDF
FLIGHT, 26 February 1954 233 COOLING a HOT SHIP Operation of the Stratos EA 100 System in the Douglas X-3 BLOWER HEAT- EXCHANCER WATER STEAM TO ATMOSPHERE IN an S.A.E. lecture last year on the cooling and air-conditioning of high-speed aircraft, Mr. George A. Lemke, a Convair design specialist, outlined the systems generally used in America's sonic aircraft. The two diagrams reproduced widi our summary of this paper (Flight, December 4th, 1953) showed the arrangement of compressor bleeds and ram- air intakes fed through an air turbine motor which provides both expansion cooling and turbine drive for generators supplying the elec tronic equipment. A comprehensive cooling system working on the general principles outlined by Mr. Lemke is in stalled in the Douglas X-3 high-speed research aircraft. The system, known as the EA 100 and designed by the Stratos division of Fairchild Engine and Airplane Corporation, provides cooling airflow for the variety of equipment in the X-3 which specially requires such services. As an indication of its capacity, the EA 100 is stated to be capable of cooling 24 four- room houses in an outside temperature of 100 deg F; yet the installation weighs only 110 lb. Such a system has had to be provided for the X-3 because it is planned to maintain speeds ranging from Mach 2.5 to 3 for comparatively long periods. At Mach 2, for example, the skin friction will raise an ambient temperature of 67 deg F to about 320 deg F; and at Mach 2.5 temperature would reach 486 deg F. The cooling system is required to provide not only cockpit cooling, but also temperature control for the 1,200 lb of electronic equipment carried in the aircraft, and for such parts and materials as are unable to withstand the temperatures expected at the X-3's design speed; among these are tyres and other rubber com ponents, hydraulic seals and hydraulic fluid. The EA 100 system comprises four major components, not counting the control valve, its regulator and the ATM tacho meter. To produce an airflow of 100 lb/min at a temperature as low as 40 deg F, the main cooling airflow is initially bled from the engine compressor and passed through a ram-air heat- exchanger. At aircraft speeds where ram temperature-rise is great, this heat-exchanger becomes ineffective, so the air is further passed through a "blower heat-exchanger." Thence it is led to the evaporative cooler, or "boiler." Here, the air is made to RAM HEAT-EXCHANCER AIR TURBINE MOTOR EQUIPMENT ^.COCKPIT The X-3's cooling system in diagrammatic form, showing the four cooling-stages from compressor bleed to cool-air delivery. boil water supplied from a tank (at altitude, of course, boiling- point is below the standard 212 deg F). The resulting steam is vented to atmosphere. The air is now at a reasonable temperature and passes through the final stage, the air turbine motor. This, as well as providing a shaft drive for accessories, also causes expansion, and con sequent cooling, of the air flowing through it. Now fully cooled, the air is piped as required to the cockpit, electronic equipment compartments, wheel-bays, and to other heat-vulnerable components. Fluids requiring cooling, such as hydraulic oil, and possibly also fuel, are pumped through the "boiler." Photographs show that this component has six oudets—two for airflow, one each for water entry and steam out-let, and two small-bore pipes apparently for hydraulic fluid cooling. The whole system is con trolled by a governor valve which is, in its turn, adjusted by a "governor control regulator" presumably operated by the pilot. It might be thought that water for cooling purposes would constitute an unnecessary load penalty for the X-3, but the makers claim that the quantity required is acceptable in view of the lightness of the rest of the system. The heat-exchangers and the "boiler" are automatically brought into operation or cut out according to cooling demands in various conditions of flight. It has been calculated that, counting the additional structure- weight required to house the system and the fuel needed to carry and to operate it, the EA 100 entails the expenditure of some 2,600 h.p. at the X-3's designed speed; and yet the largest com ponent, the "boiler," measures only 15iin by 15|inby 16^in. Some idea of the X-3's designed performance can be gained from contrasting this cooling installation with that of the Douglas D-558-2 Skyrocket; the cooling system installed in that air craft is understood to be of almost standard design typical of current American practice. The Skyrocket does not require any more advanced system despite the fact that it has reached at least Mach 2.01. The reason for this is that on such occasions flight lasts only some 12 minutes from the time of launching at 32,000ft, through the speed run at 65,000ft, to the "dead-stick" landing. About eight minutes of this time is spent in gliding back to base. The X-3 is therefore evidently intended when fully developed to maintain tri-sonic speed for considerably greater periods of time. The cooling-system components: (A) blower heat-exchanger; (8) air- turbine motor; (C) ram air heat-exchanger; (D and £) tachometer and indicator; (F) evaporative cooler, or "boiler"; (G) flow control valve (H) contro/-vo/ve regulator. FIRE-RESISTANT HYDRAULIC FLUID FROM the Monsanto Chemical Co., of St. Louis, Missouri, comes news that their Skydrol fluid—"the only fire-resistant aircraft hydraulic fluid to receive C.A.A. approval" recently "celebrated its fifth birthday" by completing 2\ million hours of airline flying time. Developed jointly by Douglas Aircraft and Monsanto, Skydrol was first used in commercial service at the end of 1948, in the supercharger system of a DC-6 of United Air Lines. Twenty-four major airlines throughout the world now use the fluid in more than 500 aircraft, claim the makers, who add that it is available at 70 airports outside the United States, and that it has never been implicated in an aircraft fire.
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