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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.

12
votes
2answers
760 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
votes
1answer
81 views

Any unique characteristics to identify aircraft engine? [on hold]

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
votes
0answers
123 views

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

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
votes
3answers
115 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
vote
1answer
134 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
votes
1answer
174 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 ...
3
votes
1answer
198 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
votes
2answers
781 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
votes
1answer
266 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
votes
2answers
94 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 ...
0
votes
0answers
62 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
vote
1answer
152 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 ...
2
votes
1answer
93 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
votes
4answers
224 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
votes
0answers
60 views

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

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
votes
3answers
114 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
votes
2answers
111 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
votes
1answer
79 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
votes
1answer
103 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
votes
2answers
141 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
votes
0answers
77 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
0
votes
1answer
89 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
votes
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
votes
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
vote
1answer
174 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
votes
1answer
104 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
votes
1answer
143 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
votes
1answer
228 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?
1
vote
0answers
101 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
votes
0answers
77 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
votes
1answer
475 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
vote
1answer
123 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
votes
4answers
723 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 ...
0
votes
0answers
62 views

How does a mixer reduce noise in a turbofan engine?

I want to know how does a mixer reduce noise in a turbofan engine? How does its shape influence the flow and the acoustics of the output air generally?
1
vote
0answers
68 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
votes
0answers
45 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
378 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
votes
2answers
197 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
votes
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 ...
2
votes
1answer
240 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 ...
7
votes
1answer
369 views

Why does the CF6 have a lower bypass ratio than the TF39?

The General Electric TF39, which powered the original C-5 Galaxy, was the very first high-bypass turbofan brought into mass production, with a previously unheard-of 8:1 bypass ratio. Yet, when it ...
3
votes
3answers
282 views

Is it possible to build a flight-capable aircraft powered by compressed gas?

I pray this isn't a physics SE question. A star engine can be considered "gas operated". So what if we power a star engine with unleashed, formerly compressed gas instead of... actual gas/aero-...
44
votes
4answers
10k views

What is this hole at the front of the engine pylon on a Boeing 707?

Images of the Boeing 707 show a hole at the front of the engine pylon just above the engine. Can someone please tell me what is the purpose? Also why do images show the hole absent on the left outer ...
4
votes
2answers
735 views

Would a ducted fan with a nozzle like a jet engine have more thrust than a normal ducted fan?

I'm trying to design a miniature ducted fan engine for a small project, but I'm not too sure how much contraction should happen between the fan and the end of the engine, if at all. Engines like this ...
2
votes
1answer
202 views

At what Mach Number do variable cycle engines (VCEs) start showing benefits over turbofans?

Currently, most supersonic engines engines are low bypass turbofans. However turbofans start becoming infeasible as the mach number increases. Variable Cycle Engines, still have noise and weight ...
2
votes
1answer
274 views

Why does a turbofan engine force bypass air into a smaller space?

I asked a question about this same concept recently but this question involves the function of the bypass air. In this YouTube video around 1 minute in the narrator says that the bypass air is pushed ...
2
votes
3answers
241 views

Why is the first turbine in a turboprop (or turboshaft) connected to the compressor?

Typically the first turbine after the combustion chamber drives the compressor as shown in this picture. (wikimedia.org) This first turbine spins the fastest and harvests the most energy from the ...
3
votes
1answer
218 views

Is my understanding of subsonic inlets correct?

For subsonic aircraft like commercial jets, the inlet has the job of making sure the correct airflow is coming into the engine. Correct airflow is important for keeping the engine's compressor stage ...
5
votes
2answers
684 views

How does a subsonic jet engine intake design ensure correct air intake?

I think I understand that inlets are there to slow down the airflow and increase the pressure to stop the compressors stalling?. If this is the case, I don't understand how the nacelle or intake ...
4
votes
0answers
145 views

What different intake designs are there, and what are their pros and cons?

I noticed that over the years (on fighter jets specifically) there have been many different methods of directing air into the engines. Primarily, the nose-intake, side intake, and underbody intakes ...