![]() ![]() Aft bypass flow joins the cowl bleed flow and passes through the engine ejector.The cowl bleed is a “shock trapshock trap” ram bleed that supplies air through tubes across the bypass door region into the engine secondary passage, where it is used for cooling, and fed through to the engine ejector.Forward bypass doors, located close to the throat, match the inlet to the engine, bypassing air overboard.This bleed passes overboard through louvers at the ends of the centerbody support struts.The boundary layer that builds up on the centerbody is removed ahead of the terminal shock through a porous bleed.The SR-71 engine air inlet is a mixed external and internal compression, axi-symmetric inlet, with gradual isentropic compression approaching the throat.Total Pressures in the Engine and Nacelle During Supersonic Cruise The JT11D-20 is made from high-temperature nickel-based alloys except for the inlet guide vanes, first compressor stage and gearbox internal parts. High temperatures required new materials and processes. JT11D-20 - A Successful Leap Into the Technical Unknown SR-71 Port Nacelle Open with J58 Along Side J58 Design Requirements Were a Leap Into the Unknown At full afterburner power the afterburner glows cherry red.Ground starting requires using two 300 hp Buick Wildcat racing engines connected to the J58 starter drive.– Afterburner section temperature reaches 3200☏ – Air entering the combustor reaches 1,400☏ The engine operates in the most hostile environment any engine has ever been subjected to:.A pyrophoric chemical – triethylborane (TEB)– ignites the main engine and the afterburner. A special ignition system is used to light this fuel.Fuel is JP-7, which has an extremely low vapor pressure and a very high flash point.Fuel consumption at a cruising Mach number is approximately 8,000 gallons per hour.The Pratt & Whitney JT11D-20, Designated “J58” by the Military The engine operates from 4,000 rpm (idle) to 7,400 rpm (max).At Mach 3.2, 54% of the thrust was provided by the inlet (differential pressure between external and internal inlet spike surfaces), 17% by the engine, and 29% by the ejector.The important features of each will be briefly covered, as each part was critical for proper operation of the integrated “propulsion system”.The “propulsion system” consisted of the air inlet, the air flow control system, the J58 engine, and the exhaust nozzle assembly (part of the airframe).The P&W J58 (JT11D-20) had the power of the Queen Mary started life with 30,000 lbT, and ended with 34,000 lbT.Designed to fly at Mach 3.2, wind tunnel tested to Mach 3 5 and flew missions at Mach 3 3+ at altitudes of 86,000+ feet.The SR-71 was the finest air breathing jet aircraft ever developed, built, and flown.General Comments on the SR-71 Propulsion System SR-71 Flight Records Sustained Speed In Level Flight Vehicle Was Designed With Radar Signature Reduction Techniques.Powered By Two Pratt & Whitney J58 Turbojet Engines, Each With The Power Of The Queen Mary. ![]() Total Time Above Mach 3.0: 11,000+ Hours (22 Million Miles).Total Flight Time Of All "Blackbird" Aircraft: 53,000+ Hours.Range Is 3,000 Miles, 15,000 Miles With Refueling.Cruising Altitude Is Between 74,000 And 85,000 Feet. ![]()
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