THE 456th FIGHTER INTERCEPTOR SQUADRON

THE PROTECTORS OF  S. A. C.

 

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  The Pratt & Whitney  J-58 Engine

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J-58 Engine

The J-58 engine was developed in the 1950s by Pratt and Whitney Aircraft Division of United Aircraft Corporation to meet a U.S. Navy requirement. The engine was designed to operate for extended speeds of Mach 3+ and at altitudes of more than 80,000 ft. The J58 was the first engine designed to operate for extended periods using its afterburner, and it was the first engine to be flight-qualified at Mach 3 for the Air Force. Two J58s power the SR-71 as well as the YF-12A and most of the A-12s. In July 1976, J58 engines powered an SR-71 to a world altitude record of 85,069 ft. and another SR-71 to a world speed record of 2,193 mph. Because of the high-temperature environment in which the engine operates, it uses low-volatility JP-7 fuel which requires a chemical ignition system. This system uses Triethylborane (TEB) to ignite the fuel. The flash-resistant JP-7 fuel protects the SR-71 from the threat of inadvertent ignition as a result of the combination of high airframe and fuel temperatures during the hot portion of flight at high speed cruising.

J58 Specifications

Compressor: 9-stage, axial flow, single spool
Turbine: two-stage axial flow
Weight: Approximately 6,000 lbs.
Maximum Altitude: Above 80,000 ft.

 


 

The Pratt & Whitney J-58 Turbojet

The Pratt & Whitney J58 engine was a nine-stage, axial-flow, bypass turbojet originally developed in the late 1950s to meet U.S. Navy requirements. It was the first jet engine designed to operate for extended periods using its afterburner. The J58 generated a maximum thrust of 32,500 pounds -- more than 160,000 shaft horsepower -- and was the most powerful air-breathing aircraft engine yet devised. The J58 was specifically tailored for operation at extreme speeds, altitudes, and temperatures, and was the first aircraft engine to be flight qualified for the Air Force at Mach 3. At maximum output the fuel flow rate in the J58 is about 8,000 gallons per hour and the exhaust-gas temperature is around 3,400 degrees. The J58 was only used on the Lockheed YF-12 interceptor and its descendents, the A-12 and SR-71.

The J58 required the use of a special AG330 engine starter cart to spool the engines up to the proper rotational speed for starting. The cart was powered by two un-muffled Buick Wildcat V-8 racing car engines which delivered a combined 600 horsepower through a common gear box to the starter drive shaft of the aircraft engines. The J58s had to be spun up to about 3,200 RPM for starting.

The variable-geometry inlets for the engines were quite complex and intricate. The most prominent feature was a hydraulically-actuated conical spike which was automatically moved forward or aft by the Air Inlet Computer as required to keep the supersonic shockwave properly positioned in relation to the inlet throat. Working in conjunction with a series of bypass ducts and doors, the spike prevented supersonic air from entering the inlet and maintained a steady flow of subsonic air for the engine. At Mach 3.2 cruise the inlet system itself actually provided 80 percent of the thrust and the engine only 20 percent, making the J58 in reality a turbo-ramjet engine.

At the speeds the SR-71 operated, surface temperatures were extremely high due to aerodynamic heating: 800 degrees at the nose, 1,200 degrees on the engine cowlings, 620 degrees on the cockpit windshield. Because of the operating altitudes, speeds, and temperatures, Lockheed designers were forced to work at the cutting edge of existing aerospace technology, and well beyond in many cases. Many features and systems simply had to be invented as they were needed, since conventional technology was inadequate to the task. New oils, hydraulic fluids, sealants, and insulations were created to cope with the ultra-high temperatures the craft would encounter. A new type of aviation fuel, JP-7, was invented that would not "cook off" at high operating temperatures, having such a low volatility and high flash point that it required the use of triethylborane as a chemical igniter in order for combustion to take place. The fuel itself was rendered inert by the infusion of nitrogen and then circulated around various components within the airframe as a coolant before being routed into the J58 engines for burning.

 

The J-58

The SR-71 aircraft, built by Lockheed, is a long-range, two-place, twin-engine airplane capable of cruising at speeds up to Mach 3.2 and altitudes over 85,000 ft (26,000 m). The aircraft is characterized by its black paint scheme; long, slender body; large delta wing; and prominent, spiked engine nacelles located midway out on each wing. The propulsion system of the SR-71 aircraft has three primary components. These components are axis-symmetric mixed compression inlets, Pratt & Whitney J58 turbojet engines, and airframe-mounted, convergent-divergent blow-in door ejector nozzles.

The J58 engine was developed in the late 1950s by Pratt and Whitney Aircraft Division of United Aircraft Corporation to meet a U.S. Navy requirement. It was designed to operate for extended speeds of Mach 3.0+ and at altitudes of more than 80,000 ft. The J58 was the first engine designed to operate for extended periods using its afterburner, and it was the first engine to be flight-qualified at Mach 3 for the Air Force. The J58 was only used on the Lockheed YF-12 interceptor and its descendents, the A-12 and SR-71.

The inlet spike translates longitudinally, depending on Mach number, and controls the throat area. The spike provides efficient and stable inlet shock structure throughout the Mach range. At the design cruise speed, most of the net propulsive force derives from flow compression pressure on the forward facing surfaces of the spike. Besides the spike, other inlet controls include the forward and aft bypass doors, used to maintain terminal shock position and to remove excess air from the inlet; and cowl and spike bleeds, used to control boundary layer growth.

The SR-71 aircraft is powered by two 34,000 lbf (151,240 N) thrust-class J58 afterburning turbojet engines. Each engine contains a nine-stage compressor driven by a two-stage turbine. The main burner uses an eight-can combustor. The afterburner is fully modulating. The primary nozzle area is variable. Above Mach 2.2, some of the airflow is bled from the fourth stage of the compressor and dumped into the augmenter inlet through six bleed-bypass tubes, circumventing the core of the engine and transitioning the propulsive cycle from a pure turbojet to a turbo-ramjet. At Mach 3.2 cruise the inlet system itself actually provided 80 percent of the thrust and the engine only 20 percent, making the J58 in reality a turbo-ramjet engine. The engine is hydro-mechanically controlled and burns a special low volatility jet fuel mixture known as JP7. The inlet bleed and aft bypass flow mix with engine exhaust flow just forward of the airframe-mounted ejector nozzle. Blow-in doors on the ejector nozzle remain open at low speeds and entrain additional mass flow into the exhaust stream. At high speeds, the doors close and the airframe nozzle ejector flaps reposition to form a convergent-divergent geometry. The blow-in doors and ejector flaps are positioned by aerodynamic forces.

The engine spikes and forward bypass doors are positioned by commands from the digital automatic flight and inlet control system (DAFICS). The DAFICS provides precise control of the terminal hock position. The DAFICS has significantly improved vehicle performance and range and has virtually eliminated inlet unstart, compared to the older analog control system.

A structurally modified SR-71 aircraft can carry external payloads weighing up to 20,000 lbm (9072 kg). This large weight limit permits flexibility in the configuration of a research package. However, within this weight limit, it is easy to design an external payload package whose additional drag exceeds the excess thrust capability of an SR-71 aircraft using unmodified J58 engines. To provide supplemental SR-71 acceleration, methods have been developed that could increase the thrust of the J58 turbojet engines. These methods include temperature and speed increases and augmenter nitrous oxide injection. The thrust-enhanced engines would allow the SR-71 aircraft to carry higher drag research platforms than it could without enhancement.

At maximum output the fuel flow rate in the J58 is about 8,000 gallons per hour and the exhaust-gas temperature is around 3,400 degrees. The J58 required the use of a special AG330 engine starter cart to spool the engines up to the proper rotational speed for starting. The cart was powered by two un-muffled Buick Wildcat V-8 racing car engines which delivered a combined 600 horsepower through a common gear box to the starter drive shaft of the aircraft engines. The J58s had to be spun up to about 3,200 RPM for starting.

At the speeds the SR-71 operated, surface temperatures were extremely high due to aerodynamic heating: 800 degrees at the nose, 1,200 degrees on the engine cowlings, 620 degrees on the cockpit windshield. Because of the operating altitudes, speeds, and temperatures, Lockheed designers were forced to work at the cutting edge of existing aerospace technology, and well beyond in many cases. Many features and systems simply had to be invented as they were needed, since conventional technology was inadequate to the task. New oils, hydraulic fluids, sealants, and insulations were created to cope with the ultra-high temperatures the craft would encounter. A new type of aviation fuel, JP-7, was invented that would not "cook off" at high operating temperatures, having such a low volatility and high flash point that it required the use of tri-ethyl-borne as a chemical igniter in order for combustion to take place. The fuel itself was rendered inert by the infusion of nitrogen and then circulated around various components within the airframe as a coolant before being routed into the J58 engines for burning.

The B-58C was proposed as a lower cost alternative to the North American XB-70 or as a medium bomber to fill the gap between the XB-70 and the XF-108 Rapier Mach 3 fighter (proposal). The B-58C, or BJ-58, was proposed as a enlarged version of the B-58A to be powered by Pratt & Whitney J58 turbojet engines. The 32,500 thrust J58 was the same engine used on the Lockheed SR-71. Design studies were conducted with two and four engine designs. As enemy defenses against high speed, high altitude penetration bombers improved, the value of the B-58C diminished and the program was canceled in early 1961.

 

  The Mighty J-58 Engine

 

The Heart Of The "Blackbird"

The Turbo-Ramjet Engine

Did you ever wonder how the Pratt and Whitney J58 engines on the Lockheed Blackbirds changed from normal turbo-jets to ramjets as the plane accelerates?
 

The engine used on the SR-71 Blackbird is called a turbo-ramjet because it is a combination of a basic turbojet engine and a ramjet. Both of these engines are discussed in greater detail in a previous question on the different types of jet engines.

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Forward view of the turboramjet engines used on the SR-71

Forward view of the turbo-ramjet engines used on the the Blackbirds.

The term ramjet is short for ram-air compression. The ramjet is the simplest form of a jet engine because it has no moving parts. This kind of engine is essentially a hollow tube into which fuel is injected, mixed with air, and burned to produce thrust, as illustrated below. The ramjet only works when it is already moving fast enough that the incoming air is compressed simply by being forced into the engine. This behavior is called the ram effect because when a volume of air is forced into a small space at high enough speeds, it is compressed to a higher pressure.

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Diagram of a ramjet engine

Diagram of a ramjet engine

This compression is accomplished in the diffuser section where the incoming air is squeezed into a small area and compressed to a high enough pressure that it can be burned with fuel. Once the fuel is injected, the mixture is fed into a combustion chamber where the fuel-air mixture is ignited to produce a high-speed exhaust. The exhaust passes out the nozzle at the aft end of the engine to produce thrust.

The advantages of the ramjet are its simplicity and its ability to accelerate a vehicle to high speeds over Mach 3. However, we have already pointed out that the engine must already be in motion before it can work, so there is a minimum Mach number that must be reached before a ramjet can be turned on and start producing thrust. Ramjets typically need to be moving faster than Mach 1 before they can be engaged. Compared to the turbojet, ramjets are also usually much less efficient until around Mach 3 or so.

Since a ramjet must already be traveling at high speeds before it will start working, a ramjet-powered aircraft is incapable of taking off from a runway under its own power. That is the advantage of the turbojet, which is a member of the gas turbine family of engines. A turbojet operates much like a ramjet except that it does not rely purely on the motion of the engine to compress the incoming air flow. Instead, the turbojet contains some additional rotating machinery that compresses incoming air and allows the engine to function during takeoff and at slow speeds.

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Diagram of a turbojet engine

Diagram of a turbojet engine

Located just behind the diffuser is a series of rotating fan blades called compressors. As the incoming air passes through these blades, it is slowed down and increasingly compressed to a higher pressure. That pressurized air is then mixed with fuel and ignited in the burner to produce a high-speed flow of air. As that high-speed flow exhausts from the engine, it passes through a stage called the turbine. The turbine is another series of rotating blades that behaves much like a windmill. The flow of air through the blades causes the turbine to rotate and generate power. The turbine and compressor sections are connected together by a shaft so that the rotation of the turbine blades causes the compressor blades to rotate as well. Once the air flow passes through the turbine, it is exhausted through the nozzle to generate thrust.

While the turbine allows a turbojet to operate at low speeds, it is also a limitation on the maximum speed of the engine. High speed flight generates very high temperatures within an engine. As speed increases, these temperatures eventually become so high that the turbine blades melt or break apart and damage the rest of the engine. For this reason, turbojets have traditionally been limited to flight below Mach 3.

Now that we've seen how the ramjet and turbojet work, we can better understand how a turbo-ramjet works. The turbo-ramjet is a hybrid engine that essentially consists of a turbojet mounted inside a ramjet. The turbojet core is mounted inside a duct that contains a combustion chamber downstream of the turbojet nozzle. The turbo-ramjet can be run in turbojet mode at takeoff and during low speed flight but then switch to ramjet mode to accelerate to high Mach numbers.

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Diagram of a turboramjet engine

Diagram of a turbo-ramjet engine

The operation of the engine is controlled using bypass flaps located just downstream of the diffuser. During low speed flight, these controllable flaps close the bypass duct and force air directly into the compressor section of the turbojet. During high speed flight, the flaps block the flow into the turbojet, and the engine operates like a ramjet using the aft combustion chamber to produce thrust.

During a typical SR-71 flight, the engine would start out operating as a turbojet during takeoff and while climbing to altitude. Upon reaching high subsonic speed, the portion of the engine downstream of the turbojet would be used as an afterburner to accelerate the plane above the speed of sound. Once the aircraft was traveling fast enough, the bypass flaps would block the flow into the turbojet and the engine would begin operating as a ramjet to accelerate to cruise speed. The SR-71 typically flew between Mach 3 and 3.5 during cruise flight, speeds at which the turbojet could not function because of the temperature limitations of its turbine blades.

This design approach gave the SR-71 the ability to operate from zero speed to Mach 3+ using the best features of both the turbojet and ramjet combined into a single engine. Today, researchers are working on new classes of jet engines that may be able to accomplish the same mission with a much simpler design. Recent developments in advanced materials capable of surviving higher temperatures may make it possible to build turbine blades that can operate beyond Mach 4. This technology is being explored in a program called the Revolutionary Approach To Time Critical Long Range Strike (RATTLRS). RATTLRS is part of the National Aerospace Initiative and is a cooperative effort between the US Navy, US Air Force, and NASA. The Navy and Air Force are hoping that this new Mach 4+ turbojet could power high-speed cruise missiles or aircraft. NASA, meanwhile, is looking for an air-breathing engine that could potentially be used in the first stage of a reusable launch vehicle to replace the Space Shuttle.

 by Jeff Scott, May 2004

 

 

   J-58 Jet  Engine Inlets

 

There are four requirements the engine inlet must meet:

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Lockheed SR-71 BlackBird - Photo: Lockheed Martin
  1. It must match the air flow captured by the inlet to the air flow required by the engine under all conditions from subsonic to Mach 3+

     

  2. Since all turbojet engines require a constant volume of air, they require subsonic flow at the inlet to the compressor face, it must reduce the velocity of flow to about Mach .3 to .5 as it enters the engine; this is no small task

     

  3. While it is reducing the velocity of the air at the compressor, it must simultaneously retain the greatest possible air pressure in order to boost flow to the compressor

     

  4. It must minimize the momentary effect upon air flow from external perturbations such as gusts

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SR-71 Air Intake Variable Inlet Control Diagram.

Unlike inlets operating in the Mach 2 and under regime, the SR-71 inlet must use variable inlet geometry  in order to manage flow over the full operating range of the aircraft.

It is important to note that the included angle of a shock wave gets proportionally smaller with increasing Mach number. At about Mach 1, the shock wave can include an angle of almost 180 degrees, but the shock sweeps back farther as speed increases, from something like this | to something more like this <.

The SR-71 inlet is classified as a ax symmetric (symmetrical around a central axis; this implies a circular shape) mixed compression inlet. This type was chosen because it offered higher pressure recovery at the compressor face, longer range, and the desired high-speed cruise performance.

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SR-71 Air Intake Design Overview.

Mixed compression inlets can provide high pressure recovery above Mach 2.2 if the shock can be maintained in such a state that it impinges just downstream of the inlet throat, even when the airflow is disturbed.

When the shock is disturbed in any way so that it moves from that point, the inlet is said to become unstarted. When this happens, the shock pops out and stabilizes forward of the inlet lip and the pressure recovery, airflow to the engine, and consequently, thrust all drop instantaneously while drag spikes upward. The nozzle must be designed to recover from the unstart condition rapidly to prevent engine damage and, on the SR-71, to prevent the airplane from yawing too much toward the unstarted engine.

 

Bypass air systems

 

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SR-71 Air Intake Inlet Design Diagram.

One of the first experiences Lockheed engineers had with the requirement for bypass ducts came during the early development of the P-80 Shooting Star. Pilots reported loud noises emanating from the intake ducts to the engine under certain conditions, a phenomenon they called duct rumble. The cause was air piling up within the duct along the inner wall, creating turbulent eddies that produced the rumble. The solution was to provide an overboard exit for this piled-up air through a system of ducts along the intakes inner wall. The air entered the duct and was led to the outside near the top and bottom of the external skin of the intake.

Supersonic wind tunnels experienced choking when air flow was blocked by shock waves that reflected back into the tunnel. The problem persisted until slots were incorporated in the tunnel walls to carry away the air from the shock waves so they would not be trapped inside the tunnel.

The SR-71s complex series of bypass doors and ducts are shown in many of the following diagrams. Some general notes on their operation:

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SR-71 Air Intake Forward Bypass Diagram.

Forward bypass doors (see above) are open when the gear is down but close when the gear retracts. They are scheduled to open again at Mach 1.4 to dump excess flow captured by the inlet.

Beginning at Mach 1.6, the aero-spike begins to retract to the rear, altering the location of the point at which the shock wave is formed and moving in proportion to the changing angle of the shock. The inlet starts at about Mach 1.7 when the shock finds its way to a point downstream of the throat.

Above Mach 2.2, bypass doors come into play to help maintain the shock at its desired location.

When an unstart occurs, both spikes move forward abruptly and the forward bypass doors are opened to recycle and obtain a restart. The spikes are retracted again until the shock returns to the desired location at the inlet throat.

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SR-71 Air Intake Centerbody (Spike) Bleed Diagram.

On the SR-71, boundary layer (layer closest to the skin) piles up around the aero-spike center body and is conducted via a porous bleed inlet (see above) through the center body of the aero-spike to four hollow pylons that conduct the air out of the aero-spike and overboard.

Forward bypass doors match the inlet to the engines needs, bypassing air overboard.

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SR-71 Air Intake Aft Bypass Diagram.

Air from the shock trap tubes (see above) bleeds piled-up air into passages that lead to the engine for cooling before it exits through the ejector at the aft end of the engine.

At the rearmost point, the spike has translated aft about 26 inches. At the same time, the inlets capture area has increased by 112%, and the throat diameter at the point of minimum cross-section downstream has been reduced by 54% to maintain the shock in the proper position.

At Mach 3, the inlet itself produces 54% of total thrust through pressure recovery, the engine contributing only 17% and the ejector system 29%. The compression ratio at cruise is 40 to 1.

Source: Case Studies in Engineering: the SR-71 Blackbird

 

 

 

 

J-58 Pratt and Whitney Engine

 

Specifications:

Model: Pratt & Whitney J-58JT11D-20

Compressor: 9-stage, axial flow, single spool Turbine: two-stage axial flow

Thrust: 32,500 lbs. with afterburner

Weight: approx. 6,000 lbs.

Max. operating altitude: above 80,000 ft.

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This night shot shows one of NASA’s SR-71 Blackbird research aircraft on the ramp at the Dryden Flight Research Center, Edwards, California, with both engines running in max afterburner.

The SR-71 Blackbird was powered by two Pratt & Whitney J-58 turbo-ramjets, each developing 32,500 pounds of thrust with afterburning. The critical problems concerning supersonic flight with air breathing engines are concentrated in the air inlet area. The circular air intakes of the SR-71 contain a center body tipped with a conical spike. The spike is movable, forward for takeoff and climb to 30,000 feet after which, as speed builds up, it moves rearward, controlling the amount of air entering the engine. As it does so, Air Inlet Bypass Doors in the side of the nacelle close to establish the correct flow of air through the engine, holding the supersonic shock wave in it's critical position within the inlet. The engine itself operates at subsonic speed. At Mach 3+ the spike is three feet to the rear of it's takeoff position, slowing down the incoming airflow, establishing an area of pressure within the nacelle, which is now pushing the engine. This action is so powerful that it accounts for 58 percent of the total thrust, the engine providing only 17 percent, and the ejectors (surrounding the nacelle near the afterburner) is responsible for the remaining 25 percent. Should the shockwave be expelled from the inlet, a condition known as an "Un-start" occurs. Un-starts have been known to be so violent as to crack the pilots helmet from the severe yaw of the aircraft. If unchecked, the resulting yaw is described by SR-71 pilots as though the nose and tail are trying to swap ends. However, an automatic control system senses this problem and repositions the Spike in milliseconds, doing so with great accuracy even though air loads of up to fourteen tons are acting on the spike, dealing with the difficulty before the human brain becomes aware of the problem, and the Blackbird cruises on....faster than a rifle bullet.

The first J-58s delivered to the blackbird program, all three models, had all stainless steel lines and the oil tank gold plated, the reason was for better heat dissipation. After a couple of years, and the subsequent tear down of engines, it was noted there was an abnormal amount of corrosion caused by dissimilar metal electrolysis. The gold plate was removed because the heat dissipation properties did not out weigh the cost of replacing lines as they started leaking.

Side note: When #957 crashed off the North end of the runway at Beale AFB and pictures were published, the hew and cry that came from the civilian segment about all the gold that was on the engine caused quite a commotion, even when it was explained why the gold was there.

 

 

Supersonic Engine Inlets

 

Subsonic Engine

Conventional jet engines have a compressor section which uses fans to compress the air before it enters the combustion section of the engine. Modern supersonic jets continue to use this same basic engine design in order to facilitate subsonic flight. At the bottom of this page we will consider designs which work in supersonic flight and which do not require a compressor. First we must consider how to make the compressor work in supersonic flight however.

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The compressor fans will not work on supersonic air. Therefore, the airflow must be slowed to subsonic speed before it enters the compressor section of the engine. This is the job of the engine inlet, sometimes called the diffuser.

Supersonic engines with Bypass are being developed, but all current supersonic engines do not use bypass. Bypass will not work in supersonic flight of course. Therefore, the development efforts are directed toward an engine on which the bypass can be turned on and off for subsonic and supersonic flight

 

 

Supersonic Diffusers or Inlets

The diffuser can be quite simple or quite complex, depending on a number of factors including how wide the desired supersonic speed range the aircraft is to be. Many jet fighters for instance are not designed for sustained supersonic flight and therefore can use quite a simple engine diffuser.

 

Convergent Divergent Diffuser

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The diagram to the left shows a simple convergent divergent diffuser. This simple design works because of the fact that supersonic flow will slow down as it enters a constricted area. You will note that this is the opposite response to subsonic flow, which tended to accelerate through a constriction ( In a Venture Subsonic flow accelerates due to the pressure waves it generates as the the air particles are pushed together. As we know, the air attempts to maintain a constant density and as a result a pressure wave is set up which causes the air to accelerate through the constriction.)

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You can see the convergent-divergent diffuser engine inlet on the F-15

However, at supersonic speed pressure waves can not move out ahead of the air and cause it to accelerate. Therefore the air piles up, becomes more dense, and slows down. This is still all in accordance with Bernoulli's equation which tells us that if the static pressure increases and the density increases, then the velocity must decrease in order to keep the total energy constant. (Generally this tendency of supersonic airflow is more intuitive than subsonic airflow to most people.)

 

The objective of the convergent divergent diffuser is to slow the airflow to Mach one just before the throat of the diffuser (venture.) The subsonic flow will then slow further as it moves through the divergent section, thus slowing to well below the speed of sound before it enters the engine.

Obviously the geometry of the diffuser has to be specific to the speed the aircraft is flying. Therefore, if the aircraft is to fly at many different speeds some more complex system will be required. Generally the convergent divergent diffuser is only suitable for short bursts of supersonic flight, at less than mach 2 (such as on a Fighter.)

 

Center Body Diffusers

 

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A more elaborate type of diffuser is the center body design. This design has a sharp center body which strikes the airflow producing an oblique shock wave. It will frequently be designed to produce several weak shock waves rather than one strong shock wave.

The inlet geometry is then such that the air is drawn into the engine inlet at right angles to shock wave. The resulting flow is subsonic, as we learned previously. It is important that the shockwaves not enter the inlet because the high pressure pulses they would create could damage the engine.

A divergent chamber then slows the airflow further before it reaches the compressor.

As before, the geometry of the center body (i.e.. how far ahead of the inlet it is) must vary for the speed of the aircraft. This is easily accomplished by mounting the center body on a track mechanism. It will be automatically extended as the aircraft fly's faster, and retracted as it slows down. This design is suited to sustained supersonic flight and therefore would be a better choice for an airliner than the convergent divergent diffuser described above.

 

Cutaway Drawings

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Diagrams from Air & Space Magazine

 

J-58 Airflow and Temperature Range

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PRATT & WHITNEY

 

The Blackbird Engine History

 

The J-58 Photo Gallery

 

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J-58 Engine on Display     USAF Museum

Close-up of J-58 Inlet with Spike Installed

Close-up of J-58 Inlet with Spike Removed

SR-71 Spike and J-58 Engine

SR-71 J-58 Engine In Afterburner on the Test Cell at Beale AFB, Ca.

J-58 Engine Testing in Afterburner at Lockheed Martin Corp.

 

 

Shock Diamonds shown in Afterburner at Night

 

COURTESY OF LOCKHEED-MARTIN,  PRATT & WHITNEY

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COURTESY OF PAUL KUTCHER

 

 

Last Updated

02/10/2014

 

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