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Aviation History
1944
1944 - 1965.PDF
SEPTEMBER ZIST, 1044 F I I G H 7 < Aircraft Heating A New System Which Operates Independently of the Engine and at All Altitudes \ j ANITROL" is the fcamc/ffiven to a system of aircraft heating developed in the United States by the firm Surface Combustion, of 'Columbus, Ohio. Liquid fuel is em ployed, of the same quality as that used in the engines of aircraft, and the heater units operate automatically, although a hand control is also pro vided. Hitherto is has been customary to heat aircraft cabins by means of a collector ring or manifold from which the exhaust gases pass into a heat exchanger. There are several draw backs to this system. The exhaust gases reach high temperature and thus have considerable were satisfied. Heater units have already been developed corrosive effect which may perforate the metal and thtRT^^hich range from a capacity of 15,000 B.T.U. to more than Details and principal parts of a "Janitrol" heater: 1, motor; 2, blower; 3, adapter ; 4, limit switch ; 5, glow-plug cut-out switch ; 6, combustion-air differential regulator ; 7, metering nozzle; 8, filter ; 9, fuel cut-off valve; 10, combustion-air inlet; n, exhaust outlet; 12, glow-plug ; 13, vaporiser ; 14, fuel pipe ; 15, ventilating air. allow carbon monoxide to enter the air which is being heated. Back pressure on the engine, resulting in a certain loss of power, is another, objection to the old system, and the fact that the heat exchanger must be located close to the engine makes necessary a somewhat elaborate system of ducting. Four Essential Conditions When Surface Combustion began to tackle the problem of an independent heat source, four conditions were laid down as essential to satisfactory operation. The first was the control of the combustion air so that a constant weight (i.e., volume increasing inversely as density) of air should be delivered to the heater at any speed, height and tem perature. The second condition was closely linked with the first: a constant flow of fuel. The third was satisfactory ignition of the air-fuel mixture at high altitudes and down to 70 deg. below zero. The fourth was keeping the flame alight under all conditions. Some of the illustrations show how these four conditions ENGINE WARMING 100,000 B.T.U., and even larger units are being developed, although in many cases a multiplicity of smaller units may offer a better solution. Reverting to the four basic conditions and the manner in which they have been met in the "Janitrol," that of a constant weight of air was achieved by taking in the air through a forward-facing scoop on the outside of the fuselage. The " ram " effect is, of course, such that at low altitudes there would be an excess of air, so that it became necessary to by-pass the ail through a differential air con trol, operated on the sylphcn bellows principle. The second condition, constant fuel flow, w/s solved fairly simply by utilising the aircraft fuel system, which already had suffi cient pressure for the purpose. A Stormproof Flame Igniting the air-fuel mixture at great, altitudes and down to 70 deg. below zeio was found to be possible by electric spark, or resistance wire, and at low temperatures the fuel could be pre-heated by a glow-Loil. To provide a flame which would not "blow out" in any circumstances was, per haps, the greatest problem oi all. As altitude is gained and the air becomes less dense, a greater volume of air has to be supplied (in this ^se by the automatic diffe/€ntial air control) in order to keep the weight of air supplied the same. This means that the air is entering the combustion chamber at greater velocity, and the ordinary steady flame would be likely to be extin guished. WINDSHIELD & GLASS SURFACE ANTI-ICING. DEFROSTING AND DEFOGGING The solution was Drawing showing installa tion of "Janitrol" high- altitude heaters in a large aircraft
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