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Aviation History
1950
1950 - 2219.PDF
604 FLIGHT, 21 December 1950 JET-PROPULSION TRILOGY News from America—An Independently Produced Afterburner and an Auxiliary Turbine : Details from Britain via America—The Beta Rocket Motor W HEREAS in this country the technique of gas-turbine reheat, or afterburning, is still the subjectof development work by the engine manufacturers concerned, in America it has apparently reached a stage at which the design and production of complete units can be entrusted to a specialist firm. Thus an independent con- cern—the Solar Aircraft Co., of San Diego, California—has developed an afterburner for use with the Westinghouse J-34 turbojet, and the unit has successfully completed a rigid 70-hour qualifying test for acceptance by the U.S. Navy. As may be seen from the cut-away illustration, the Solarafterburner is a divergent/convergent duct, with a pair of annular channel-section fuel distributors arranged concentrically in theplane of the largest diameter. At the forward end of the unit one-quarter the weight of conventional power-plants of com- parable power. Inasmuch as ramjet and rocket units have no rotating parts, a turbine driven by ram-air pressure is a reasonable choice as a prime mover for driving various auxiliaries. The Marquardt Company is now in production with four different types of these accessory power-plants: (i) a unit for a U.S. Navy missile, which comprises a high-speed ram-air turbine driving two hydraulic pumps and a constant-speed alternator through a reduction gear, and using a hydraulic speed control to maintain r.p.m. within plus or minus 3 per cent; (ii) a unit, for a U.S. Air Force missile, which drives a high-speed alternator direct, and embodies a special electronic governor and throttle to maintain speed within lj per cent either way; (iii) a unit for missile application, incorporating a high-speed ram-air turbine, providing direct drive to a large-capacity fuel pump; and (iv) a complete ctioned view of fterburner shows the concentric fuel-distri- butors and, at the forward end, the actuators for the outlet shutters. are two actuators (one above and one beneath) from which trans-mission shafts run rearward to actuate the " eyelid" shutters that vary the area of the outlet orifice. The downstream halfof the afterburner is enclosed by a shroud through which cold air can pass to provide some measure of thermal insulationfrom the enormous temperatures of the re-heated gases, the shroud also having the function of protecting the eyelid shuttersfrom mechanical damage. Another "accessory" development recently announced inAmerica is an air and/or hydrogen peroxide turbine auxiliary power-plant for use with high-altitude supersonic missiles.Developed by the Marquardt Aircraft Co., of Van Nuys, Cali- fornia, to meet the hydraulic, electrical and fuel pump require-ments of ramjet- and rocket-powered missiles, as well as those of turbojet aircraft, these units are claimed to be less than accessory-drive unit designed to operate both from hydrogenperoxide and ram-air. Turbine efficiencies higher than 83 per cent, including gear-box losses, are stated to have been achievedon test in a government laboratory. No details are available as to the method used in applyinghydrogen peroxide as an alternative for driving the turbine in the Marquardt design but, on the other hand, the October 9thissue of our American contemporary, Aviation Week, included an article on the Beta rocket motor exhibited on the Ministry ofSupply stand at the S.B.A.C. show in September, and gave data on the unit which English journals were not permitted to publish.When the American article was brought to the notice of the Ministry of Supply, the official reply was that the contents ofthe article could " neither be confirmed nor denied;" we have, therefore, no recourse but to give the information as it appearedin the American journal, whilst accepting no responsibility for its accuracy. Although designed by the R.A.E., theBeta is built by Faireys, and it is stated that it has already flown. The twin com-bustion-chambers are mounted one above the other in such a manner that the upperchamber can be tilted to effect pitch con- trol of the aircraft (or missile), whilst thelower chamber can be swung laterally to effect yaw control. The Beta is a "hot" rocket, in whichhydrogen peroxide is used as an oxidiser for an unstated fuel, which might be anyone of a large group of hydrocarbons. It is also stated that, as a means of cooling,hydrogen peroxide is circulated through a jacket surrounding the motor combustionchambers and nozzles. Furthermore, a portion of the peroxide flow is divertedto a steam generator to supply power to drive a turbine which, in turn, drives Interior of the' Marquardt^jpuxiliary turbine, showing typical feotteuuafcro/jgement for a variety of accessory drives. At the inflow end is seen a cone-type throttle.
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