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Aviation History
1954
1954 - 2204.PDF
ENOID AIR VALVE BY-PASS VALVE IGNITER VALVE 6 August 1954 177 STOP VALVE THROTTLE VALVE SPARKING PLUG COMBUSTION CHAMBER FUEL JETS COOLING JACKET SOLENOID AIR VALVE IGNITER CHAMBER LER DUMP VALVE THE DEVELOPMENT OF A PUMP-FED LIQUID-FUEL AIRCRAFT ROCKET sidered as a first step, but there were then virtually no data available about scale effect; so, on balance, it appeared preferable to start off with a full-size chamber and so meet all the problems at the correct size first time. The company's subsequent experi ence has justified this decision. The approximate shape and size of the chamber were worked out fairly accurately on paper before rig testing was even begun. The two great unknowns were how the fuels would be injected and how they would be ignited. One of the first rigs, therefore, consisted simply of a suitably mounted spray nozzle, together with a supply of water and a high-capacity pump. It is charac teristic of the period that the only convenient pump with enough power was that on the trailer appliance of the works fire brigade, who were accordingly called out whenever a test was to be made. Preliminary calculations suggested that the nozzle would have to pass 60 gal/min (if both propellants were injected together) with a pressure-drop not exceeding 100 Ib/sq in—say, from 400 down to 300 lb/sq in. After experiments with one pattern of two- liquid injector, a different design was developed and tested with supplies of fresh and salt water fed simultaneously by a pair of trailer pumps. The spray was caught in a honeycomb can, the amount of fluid in each cell providing an indication of the dis tribution and a hydrometer being used to determine the specific gravity in each cell, and hence the degree of mixing. Investigation of ignition problems was another undertaking which could proceed without any special facilities. By the time this stage was reached, in 1947, the correct burner had been developed, and one was screwed into a "simulated" chamber consisting of a pair of metal drums, one inside the other, open at one end-ond with a water-cooling flow through the double wall. This apparatTJSy^Jcnown as "the bucket," was similar to the eventual combustion chamber only in the relative positions of the burner and igniter, this geometry having been guessed— accurately—in advance. A requirement of the original speci fication was that the rocket should be capable of being ignited or re-ignited in the air, but the first tests were carried out with (Left) The fuel and oxidant pumps are driven by an epicyclic gear which incorporates a band clutch. (Right) A close-up of the Snarler combustion chamber installed in the Hawker P.1072, with the access panels to the chamber and control valves removed. It will be noted that the skin was fitted quite tightly around the chamber.
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