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An odd number of cylinders is required by the combination of the single-crank radial design, the four-stroke (Otto) work cycle, and the desire to keep the power strokes evenly spaced in time. To keep the design simple and lightweight, a single-bank radial airplane engine has one crank, which means that the pistons must reach the top of their travel in ...


61

Several issues: As you mentioned, high specific fuel consumption. About to that of turboprops, but without the reliability. If you're going to live with that SFC, you might as well as go with turbines. Poor reliability. They are very sensitive to tuning and timing. A 4 stroke piston aircraft engine will run with all kinds of things wrong with it. Cam ...


56

Even if we ignore the salaries of everyone involved; engineers, sales people, management, Q/A teams, manufacturing teams, more sales people, and then a few spare engineers... I don't understand. If it's just designing a jet engine, then raw materials cannot possibly be a major factor even if it's something like titanium or composites. While the raw ...


50

Of course the basic concept of a turbine engine is relatively simple, but the devil is in the details. To make an engine efficient, reliable, powerful, and safe, a lot more components are needed. Fuel. Obviously an engine needs fuel to operate. The fuel is burned in combustors located around the circumference of the engine. This requires separate fuel lines ...


45

Constraints Different applications have different constraints: Aviation: very light weight, highly reliable Marine: very high endurance Automotive: moderately light weight, responsive Motorcycle: very light weight, very compact, very responsive Different technology ages yield different solutions due to additional constraints, always limited by the then ...


43

Yes, supersonic conditions can indeed be replicated on the ground for purposes of airframe and engine testing. Arnold Engineering Development Complex (AEDC) The U.S. Air Force and NASA both operate supersonic wind tunnels, as do Lockheed, P&W, and others. The most advanced of these facilities are probably those at Arnold Engineering Development Complex ...


43

This is because those engines have turbocompressors which are used to supply cabin air. The engine bleed air drives the turbine of the turbocompressor, which in turn would drive a compressor which would pull in air from the atmosphere through the front hole, compress it, and send it down to the Environmental Control System for use as cabin air. The ...


39

Centrifugal compressors only produce a more compact engine at low mass flow, which means low thrust. The amount of thrust an engine can produce is proportional to its intake area times exhaust velocity. Increasing the latter is undesirable, as energy and thus fuel consumption is proportional to velocity squared. So engine designers target mass flow to gain ...


38

These are secondary intake doors which allow more air to reach the engines. They are opened by the engine control computer when the main intakes are not providing enough air for the power setting of the engine. In order to minimize radar cross section, the engines of the B-2 are buried in the wings and the intake needs to be curved. Also, and for the same ...


32

It is a struggle, but it can be done. For the J58, Pratt&Whitney had a test facility at West Palm Beach which would simulate conditions at speed and altitude. From this site: The picture actually shows test cell A-1 at Pratt and Whitney’s West Palm Beach facility. […]. This test cell was actually an altitude simulation cell used for testing ...


32

Image source The generators are usually driven from the Accessory Gearbox. This CAD drawing is from the company that makes accessory gearboxes for the Rolls Royce Trent engines driving the A330 and A350, and it shows the connection of the accessory gearbox to the high pressure rotor. This picture from the book The Jet Engine by Rolls Royce shows the ...


32

Jet engines are some of the most complex machines ever created. They have to be as light, efficient, safe, and reliable as possible. There's a reason that most new airliners recently have been affected by delays from engine manufacturers. This is a hard balance to engineer when on a schedule and budget. Jet engines could certainly be cheaper to develop and ...


28

The bleed will be tapped from one or two of the 3rd, 4th, 5th or 6th High Pressure Compressor stages. Usually there are two bleed ports. The highest pressure port will supply really hot air for things like anti-icing. The lower pressure port farther upstream will supply air for air conditioning/pressurization and other pneumatics. Some systems combine ...


27

Your reasoning is correct if engine mass is not important. Ships use huge engines, because increasing the number of cylinders beyond 8 will have diminishing returns in terms of smoothing out the torque ripples, and bigger cylinders help to increase efficiency. But aircraft need to keep the mass of the engine down. Wartsila-Sulzer RTA96-C turbocharged two-...


27

Wikipedia tells you the answer: The 707 uses engine-driven turbocompressors to supply pressurized air for cabin pressurization. On many commercial 707s, the outer port (number 1) engine mount is distinctly different from the other three, as this engine is not fitted with a turbocompressor. Later-model 707s typically had this configuration, although ...


27

Being a ground attack aircraft, the Su-25 has an operational ceiling of 23,000 ft and will not encounter the low temperatures to which a Boeing 777 is regularly exposed. Therefore, the risk of diesel fuel gelling and clogging the fuel lines is much lower. On the other side of the temperature scale, gasoline could vaporize in hot environments and equally ...


25

Location The general design is to group elements that need to be driven by the engine around one "accessory gearbox" which is located away from the engine centerline. A driving axial shaft in therefore required. In some cases, there are multiple accessory gearboxes. Usually the accessories are located at the bottom of the engine fan case, making them and ...


24

There are many extra components, generally known as "accessories". Fuel pumps, the ignition and starter circuits and control units, turbo pumps, hydraulic pumps, stator vane angle actuators, fuel flow controls, FADEC computers, fuel metering unit, fuel filters, fuel return valves, bleed air pickups and ducts, generators, gearboxes to drive the pumps and ...


24

The afterburner, of course. In simplest sense, the afterburner is just an extension attached to the engine where the fuel is dumped into the exhaust, resulting in an inefficient but huge increase in thrust. Turbojet with and without afterburner; image from aerospaceweb.org In the above image, you can see the basic schematic of the afterburner- it ...


24

Because the LP turbine extracts power for the fan, which requires the most power. The HP and IP turbine only extract power for their connected compressors - the LP turbine extracts power for the fan and the LP compressor. The fan does work on all airflow through the engine, the compressors only on a fraction (10:1 for a high bypass like the Trent 1000). The ...


24

Doors for secondary air intakes. Buried engines need additional air during takeoff and low speed flight.


23

The B-52 was build in different versions (A-H) and the engines and their installation differ between these version1. The image in the question most likely shows the engine configuration of a B-52H. The following drawings suggest that this also changed the inlet design2. There seem to be different engine-designations depending on the application. For the B-...


22

The 777X is still in development and it will be powered by the General Electric GE9X (also still in development). The current talk is that GE is working on a proprietary method (has been for 20 years) that will make the chevrons obsolete. Namely the use of an oxide-oxide ceramic matrix composite, which they have unveiled already (October 2013) for the ...


21

(Source) Image shows CFD simulation for a jet engine carried out by Northern Arizona University. Pretty much as your illustration, but more turbulent and not as many complete turns. Let's take one rotor disk at a time. Each blade on each disk is like a wing. Air is rushing in at it. And it, is moving down on the air (or up from the other side). Giving the ...


20

The inlet angle is a compromise between cruise, when the aircraft has a low angle of attack, and the take-off and climb phase, when the engine runs at maximum thrust, and the angle of attack is several degrees higher than during cruise. Especially right after rotation, when the aircraft is heavy and slow, the angle of attack might reach into the lower two-...


19

Centrifugal is easier to make. It's just a big vacuum cleaner with a kerosene burning furnace behind it instead of an electric motor. You have a one piece impeller, as opposed to numerous little blades and discs, and can be cast or machined from a block of metal. It's not dependant on the aerodynamic lift of blades to force air from a large space into a ...


17

Turbo compressor drive was provided by 16th stage air (high pressure, high temperature) from its respective engine. 16th stage air was also used for: engine anti-icing, thrust reversers, fuel heat, hydraulic tank pressure, surge bleed valve and water tank pressure. To operate above 40,000 ft on a B-320 we had to have 3 T/Cs or 2 T/Cs and one bleed or 1 T/C ...


17

Axial turbine engines take up a lot of space...lengthwise. Centrifugal compressors are shorter and wider, and are very often used in turboprop and turboshaft engines, for instance the Rolls Royce Dart is a single axis turboprop engine. The photo demonstrates the compactness of the engine...lengthwise. . Can you create a centrifugal air pump that pushes ...


16

When a cylinder gets bigger— The square-cube principle states that its volume grows faster than its surface area.— Wikipedia Pressure and mass: Reducing the number of cylinders increases the amount of force per cylinder and per attachment point to the crankshaft. Since the surface area doesn't scale as fast, all the engine parts will have to cope with ...


15

A lot of pictures of this intake make it quite hard to determine what is the exact geometry. But the one below is by far the best - thank you @ymb1. http://www.af.mil/News/Photos/igphoto/2001513002/ Before, it was hard to tell exactly what's happening. In some pictures, it looked like the inboard engine was slightly further forward of the outboard engine. ...


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