Questions tagged [engine-design]

Questions about the process and principles used when designing aircraft engines. Use "jet-engine" and "piston-engine" tags to specify a certain type of engine.

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2
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2answers
124 views

What are the relative efficiencies of the various stages of a counter rotating propeller?

After going through the CFD results of a drone project I am involved in, I noticed that the data shows significantly increased (+10%) thrust generation at the second stage of a counter-rotating, 2-...
1
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3answers
228 views

Can a gas turbine be able to switch from torque to thrust?

Can a turbine engine be switched from providing torque (like a helicopter) to the rotor to transfer power to provide exhaust thrust (like a jet plane)? Related: BV-347 upgrade this way?
3
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2answers
107 views

Can an S-duct fit a turbofan exhaust instead of the intake?

Can an S-duct fit a turbofan exhaust instead of the intake? The idea here is to merge 2 exhausts into one at the exact center of the tail. This would be for twin-engine aircraft that have both engines ...
1
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1answer
55 views

On a centrifugal compressor impeller what is the difference between the radial vanes and rotating guide vanes?

I thought the radial vanes were a machined part of the impeller that just force the airstream radially? And that another name was rotating guide vanes as they are rotating with the impeller disc.. But ...
0
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1answer
148 views

Why is the intake of the 757 (RR) engine slanted? [duplicate]

I'm sitting looking at a 757 with Rolls-Royce engines and just noticed that the intake is slanted forward by 5-10 degrees. Anyone know why? (wikimedia.org)
18
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4answers
3k views

Why do airplanes use an axial flow jet engine instead of a more compact centrifugal jet engine?

Axial flow jet engines take up a lot of space. Centrifugal jet engines create high pressure. Can you create a centrifugal air pump that pushes as much air as a axial jet engine. Centrifugal air ...
2
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2answers
108 views

Could a Dyson fan displace more air without increasing the fan size?

So the Dyson Fan is cool. But it has a thrust to weight ration of 0.6. Not very efficient for flight. Its great at sucking large amounts of air but not at a very high velocity. Thrust is small amounts ...
6
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1answer
222 views

How does the CFM LEAP-1B engine achieve the same efficiency as the LEAP-1A despite its lower bypass ratio?

The CFM LEAP engine comes in 3 variants (1A, 1B, 1C). The larger LEAP-1A and LEAP-1C variants have bypass ratios of 11:1, while the smaller LEAP-1B only has a bypass ratio of 9:1. For turbofan ...
4
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2answers
127 views

What modifications are required for automotive fuel STC?

What actual engine modifications are required to allow certificated piston engined general aviation aircraft to run automotive fuel under an FAA Supplemental Type Certificate (STC)?
2
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1answer
102 views

Why do the Diamond DA-42 and DA-62 have a minimum fuel temperature requirement?

On the turbo diesel DA-42 and DA-62 aircraft there exists a minimum fuel temperature limitation where you may not start or operate the aircraft below that. Does anybody know why this is? It seems ...
0
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0answers
44 views

Oultlet vane guides

I have looked around the web and I could not fine this information. How many vanes are there for the CF6-80 and the CFM-56? Is the count dependant on anything particular, such as fan diameter?
29
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2answers
4k views

What features enable the Su-25 Frogfoot to operate with such a wide variety of fuels?

It is widely attested* that the Su-25 Frogfoot's engines (the Turmansky R-95Sh and later the R-195) were designed to function using a wide variety of fuels, including diesel, gasoline, petrol, ...
0
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1answer
124 views

Any unique characteristics to identify aircraft engine? [closed]

I love to find out the engine manufacturer and make, used in all of the aircraft I fly. Can anyone provide hints on how to identify an engine uniquely? The CFM56 on a Boeing 737NG is easy. It has a ...
0
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0answers
143 views

Does any modern jet engine have blow-in doors, if not, why? [duplicate]

Are the blow-in doors concept on some engines like the JT3D used on modern jet engines, or not? If they are unusual, please explain why?
0
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3answers
216 views

Why is carburetor heat unnecessary at full throttle?

Questions like How does aircraft design affect carburetor ice? show how carburetor mount point affects the relative passive heating of the carburetor by the engine, but I've never learned why full ...
1
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1answer
144 views

Are turbofans compensated for gyro effect?

In a multi-spool design is the gyro effect canceled or mitigated by having the two or more spools spinning in different directions?
4
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1answer
267 views

How difficult is it to design a high bypass turbofan given a military derived core?

Suppose one of the big-threes is given a military low-bypass turbofan core, how difficult would it be to produce a design centered around this core that matches the competitive performance of a ...
4
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1answer
217 views

Are all engines fan blades made out of titanium?

I was wondering if all engine fan blades are really made out of titanium.
11
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2answers
910 views

Are centrifugal turbojets easier to make than axial ones?

Looking at the history of jet engines, I noticed that the British first made centrifugal-types, but the Germans went straight into axial-types. Which type is easier, if any? By that I mean, which ...
2
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1answer
422 views

How is the F-22's nacelle/engine bay ventilated?

How is the aircraft skin around the engine bay in the F-22 cooled? As in the F-35, there are scoops below the wings, which provide ram air around the engine bay, but you don't see any scoop around in ...
0
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2answers
101 views

Why can't ramjet diffusers be stacked to achieve a good overall pressure ratio?

The problem with ramjets is that they only gain efficiency similiar to turbojets at speeds above mach 2. However, ramjets can operate at speeds of a few hundred km/h. Why therefore cant ramjet ...
2
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2answers
182 views

What is the minimum size of a ramjet?

Having recently learned that 155 mm ramjet artillery shells are now a thing, I wonder how much ramjet engines can be miniaturized. Could we see ramjet tank shells? Man-portable recoilless guns? ...
1
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1answer
179 views

Who should design the nozzle of jet engines on aircraft?

There is a question in my mind that which company should design the nozzle of jet engine - the aircraft designer or the engine designer? If you watch this documentary: BBC Documentary Rolls Royce ...
3
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1answer
179 views

How does propellers' pitch change during the use of reverse thrust in turboprop/propfan propelled planes?

Which way do proplellers turn during the use of reverse thrust in turboprop/propfan propelled planes: A) Do the leading and trailing edges of propellers remain the same or... B) Do the propellers ...
3
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4answers
258 views

What changes are needed for a piston-prop aircraft to withstand saltwater environment?

I'm interested in WW2-era piston-prop aircraft. I want to know what changes are needed to make the aircraft withstand saltwater corrosion. Presumably these are different and more expensive than the ...
0
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0answers
64 views

What % of horsepower in a turbine is used by the compressor section? [duplicate]

If a turbine generates 10,000 shaft horsepower, I am trying to understand how much horsepower has been used to compress the air. So the turbine that generates 10,000 hp must in fact generate 10,000 ...
3
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3answers
132 views

Would there be a purpose for a set of compressors in an electric turbo fan?

This is actually a two part question. Would there be a purpose to a compressor in an electric turbofan where there is no need for a combustion chamber, and if not, is there then a purpose for a bypass ...
0
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2answers
115 views

How do engines cope with various intake airflow speeds?

On a recent trip out of Washington Dulles to San Francisco, our B777 met with 200+ mph headwinds (as per the passenger entertainment system) at 35,000 ft for the first half of the route, before ...
2
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1answer
82 views

Is there a good online source on rotating detonating pulse engine?

I can't find a clear presentation that would explain the workings of a rotating pulse detonation engine graphically, only useless (to a layman) cfd simulations of the combustion chamber. Please share ...
0
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1answer
147 views

How does the debris rejection system in the CFM LEAP engines work?

How does the debris rejection system in the CFM LEAP engines work? LEAP - The debris rejection system
0
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2answers
175 views

Could a jet engine be made from cast aluminium?

What materials are used to make the high temperature-high pressure bearing parts in a jet engine? I'm asking about the combustion chamber, combustors, nozzle and diffuzers (as in ramjets) rather than ...
3
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0answers
80 views

Could injectors be used as an alternative to turbopumps in jet engines?

Could injectors be used instead of turbopumps in aeroengines? Are there jet engimes that already use them? https://en.m.wikipedia.org/wiki/Injector
2
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1answer
172 views

Why and how can a fume event occur?

« A fume event occurs when bleed air used for cabin pressurization and air conditioning in a pressurized aircraft is contaminated by fluids such as engine oil, hydraulic fluid, anti-icing fluid, ...
9
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3answers
2k views

Is the bleed air passengers breathe tapped from the engines before or after it comes in contact with fuel? And why? Isn't this unhealthy?

Passengers are often surprised to hear that the air they breathe comes from inside the engines. This sounds unhealthy. Can you explain, why it is not ? Is bleed air tapped (for cabin pressurization) ...
0
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0answers
35 views

Adjusting nozzle shape for reduced flow rate

Suppose i have a ramjet engine, but in the combustion area i make an opening along the whole cirumference (a slit) feeding a channel, in which the pressure is the same as in the combustion chamber. ...
1
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1answer
217 views

Does preheating fuel before it reaches the turbine result in a performance improvement?

Preheating fuel before it reaches the combustion stage was first proposed several decades ago as a way to improve mixture, fuel economy, and to reduce emissions in car engines. One example of this ...
3
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1answer
179 views

What is the difference between active tip clearance control system and passive tip clearance control system in turbine?

What are the main differences between turbine active tip clearance control system and passive tip clearance control system?
-1
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1answer
154 views

Turbofan design parameters [closed]

I am writing a model for LM Prepar3D to simulate the flight model of a commercial airliner. The specification I am following requires some parameters from the engine (CFM56). ...
4
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1answer
244 views

Which aircraft/powerplant manufacturers use metric hardware?

The vast majority of airframes and powerplants use U.S. standard/SAE hardware. Which manufacturers of engines and airframes use metric hardware?
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0answers
110 views

How does a partially covered air intake affect the thrust of a propeller ?

does a partially covered air intake of a ducted propeller significantly affect its thrust? If so, will it be like 10 or rather 90 percent less thrust ? Thanks for your answers! Simon
0
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0answers
100 views

How does the number of blades affect the static thrust of a propeller? [duplicate]

Since I couldn‘t find an answer to this question I thought I‘d ask you guys! By which factor does the thrust of a propeller increase if I double the number of blades, the motor being powerful enough ...
0
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1answer
584 views

What is the cause of cracking and corrosion in Trent 1000 engines?

According to this description and this one of some Trent 1000 engine problems, there appears to be a problem with cracking/corrosion of the fan blades, but does anyone have any insight as to why this ...
1
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1answer
251 views

Could a kerosene fueled jet engine run on methanol without significant modifications? [duplicate]

Could a kerosene fueled jet engine run on methanol without sacrificing performance other than specific impulse? Would it require changes to the fuel injection/turbopump system? Would the combustor ...
3
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4answers
938 views

What drives the shape of an engine's intake on a fighter jet?

Rectangular intakes have more corners which might increase subsonic pressure losses and would weigh larger than a pitot (Semi-circular) type intake. Are the designer drivers solely based on supersonic ...
1
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0answers
70 views

Do plug nozzles improve efficiency on lower throttle settings?

Plug nozzles are used to adjust for the overexpansion/underexpansion of the exhaust with altitude. Do they also adjust for overexpansion/underexpansion of the exhaust caused by lowered mass flow ...
0
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0answers
49 views

Are throttleable rocket engines the less efficient the lower the power setting?

Are throttleable rocket engines less efficient the lower the power setting? Logically that would lead to lower pressures in combustion chamber and so lower thermodynamic efficiency. Or is it remedied ...
4
votes
1answer
546 views

Is this a blisk?

GE Aviation bought the Czech company Walther to get their 600-800shp turboprop engines, now called the H75... On their website, two thirds down the page, the following picture has the caption The H-...
6
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2answers
203 views

How do engine manufacturers derive varying amounts of thrust from a single engine model?

What changes do manufacturers make to an engine to vary the amount of thrust it produces for different applications? Take the GE CF34 for example where there is a 10780lb difference between the thrust ...
28
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2answers
5k views

What are those hatches on the engines of a B-2 that are open during takeoff?

I just watched this drool-inducing video of Northrop Grumman B-2 Spirit, And noticed that there are a couple of hatches near each engine, which were open: I initially thought they were open for some ...
3
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1answer
323 views

Why are most turbofans tractors, but most propfans pushers?

Turbofans and propfans are, in concept, quite similar: both have a turbojet core, plus one or more additional turbine stages that drive a fan(s) which blows air around the core (this is known as ...