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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8
votes
1answer
206 views

What is the function of the aft stator in CFM's open rotor engine design?

CFM revealed their design for a open rotor propfan engine with two stages of blades - one active set of blades rotating in the forward and an static sets of blades on the aft. According to The ...
0
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1answer
173 views

Can anyone tell me more info about this radial engine?

non-aviation expert here doing a project for a friend. I am trying to learn a little more info about this 3D model radial engine. I downloaded it off a stock 3D model website, that offered almost no ...
3
votes
2answers
112 views

How does afterburning not affect upstream air in the engine?

I've read in many books that afterburners are designed not to affect the upstream engine components, so if there's a large amount of combustion going on after the addition of afterburner fuel, how ...
0
votes
1answer
144 views

Can liquid hydrogen be pumped directly into a jet engine without a heat exchanger? Is it burned as a gas or a liquid in the combustion chamber? [closed]

This NASA research paper on H2 engines includes a diagram of Wesley Kuhrt's 1956 design for a hydrogen-fuelled engine, which has no heat exchanger: (Image by United Technologies Corporation, via NASA....
2
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1answer
160 views

Why is a combustor in a gas turbine engine asymmetric?

As the above question stated, the upper and lower section of the combustor isn't same. Is there any reason behind it? Due to which the cooling of the combustor is also different in the upper and lower ...
6
votes
1answer
109 views

What is this scoop found on the core of a PW1127G engine near the CC/turbine section?

The view is back to front, the scoop is at 10 o'clock on engine 1. What would be it's function? I need supportive literature as well if possible.
3
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4answers
381 views

Would this mechanical apparatus be a new means of creating aerodynamic lift? [closed]

I recently came up with a conceptual idea for creating aerodynamic lift which would use an unconventional centrifugal impeller. I would like to know if this conceptual design of mine is something that ...
0
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2answers
93 views

Why is a reciprocating engine air intake a reverse bell shape? [duplicate]

Why would this inlet for the induction system get wider as the air approaches the filter? What net effect does this have on intake pressure, and how would an inlet that starts wide and then narrows ...
1
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0answers
25 views

Does an increase in Mach number lead to a decrease in Total Pressure Recovery (TPR) for supersonic inlets?

I am curious if the total pressure recover for supersonic inlets, in general, decrease for an increase in Mach number.
3
votes
2answers
158 views

How do electric propeller governors (or electrically controlled governors) work and what are their pros and cons?

I am trying to understand why electric propeller governors are not (yet) prevalent given that they offer the ability to control the RPM with high accuracy. What is the typical architecture for an ...
1
vote
3answers
176 views

Are there aircraft with multiple inlets for a turbojet engine?

Are there aerial vehicles which have multiple inlets with air ducts (shaped in S-forn) , which all lead the air to one single turbojet engine? I have not enough space to put just one inlet area on my ...
0
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0answers
42 views

Why does the CFM LEAP have so many LPT stages? [duplicate]

With the core power being similar, intuitively, the higher the number of turbine stages, the more energy is absorbed, the higher the RPM. But the PW1000G vs CFM LEAP (both engines have similar thrust ...
6
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1answer
2k views

Why do propellors have white markings on their tips? [duplicate]

Why do propellors have white markings on their tips? Here are a couple of examples:
7
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1answer
277 views

What are the “beta lines” of a gas turbine engine component?

For a compressor in particular, what do the beta lines represent? I know for a compressor map you have the lines of constant spool speed, and the contours of isentropic efficiency. I also understand ...
4
votes
1answer
971 views

Why are jet engine fan blades painted?

I came across this extremely interesting article with details on a 2018 United Airlines Boeing 777 engine failure, which is also related to the more widely-publicized failure a few days ago: http://...
0
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0answers
22 views

how to calculate power required for engine of duct fan? [duplicate]

I need 600 N thrust for my aircraft. I am planning to use duct fan. according to calculation of duct fan: T=Ct.ro.A.V^2 Ct=0.03 ro=1.09 (in my place) A=(0.26^2)*3.14=0.21225 m^2 v=300 m/s then T=624 N ...
20
votes
1answer
3k views

How much weight does a blisk save?

A Blisk is a bladed-disk, all one monocoque component. So the blades do not have to be inserted and secured, and they are not removable. No nuts and bolts either. The downside is that any serious ...
2
votes
1answer
97 views

Are centrifugal compressors/turbines less efficient internally, and if so, why?

From my related question which found a good example of a centrifugal turbine jet engine, the Henkel Hes 3. Picture Source Website (it's in Czech). Thanks to Jan Hudec for finding it. My understanding ...
3
votes
2answers
269 views

Has there ever been a centrifugal turbine in an aircraft engine?

These days, most jet engines feature axial compressors and turbines. However, there are some older aircraft engines with centrifugal compressors, like the Rolls Royce Nene. But I've never heard of any ...
1
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0answers
55 views

Texts on aero-engine structures

I have been scouring the web for resources on aero-engine structures and structural design (preferably civil turbofans) but unfortunately it seems like they are hard to come by. I would like dedicated ...
4
votes
2answers
258 views

The latest turbofan aircraft feature an exposed exhaust cone, does it come with some benefits? [duplicate]

Aircraft like Airbus A320neo/A330neo/A350 series have a visible exhaust cone, which is not visible in the older versions of Boeing 747, Airbus A330/A321/A319 etc. Why is this design preferred over the ...
0
votes
1answer
126 views

What is the purpose of air that passes through the engine core in a turbofan engine? Is it mainly to spin the fan rotor? [duplicate]

The majority of the air going through the bypass is producing most of the thrust and providing the air that cools the engine. Does is also provide the pressurization and cooling/heating for the cabins?...
18
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2answers
6k views

Why do new engines have a case with a triangular tiling pattern?

Take a look at the case of new engines such as the F-135: or the F-119: Why do they have a case with a triangular tiling pattern? Is this a new technology? A new material?
0
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0answers
52 views

What should the inlet to throat area ratio be for a CD rocket nozzle on an aircraft flying at Mach 10?

I am analysing a rocket CD (convergent-divergent) nozzle at a altitude of 15,000m. I am stuck on how to calculate the areas so that at the throat of the nozzle Mach number equals to one. The ...
6
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3answers
1k views

What is the most severe engine failure for modern turbofan?

Today I read again something about the Southwest Airlines Flight 1380 and the related engine failure resulting in one passenger being sucked out of the window. As I understood it was a fan blade out ...
3
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1answer
448 views

Why do some Turbofan engines have multi-stage fans?

I was wondering why some turbofan engine have multi-stage fans. e.g. F-119 engine: F100 Saturn AL-31
0
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1answer
125 views

What gas turbines have the following configuration?

Is there any jet engines--with published data on the dimension of the turbines and compressors--that are of the configuration of 2 Low Pressure compressor, 8 High Pressure compressor, 2 High Pressure ...
0
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0answers
34 views

What is the diameter of each stage of the PW800 engine compressor and turbine?

I am an Aerospace Engineering student working to analyze P&WC's PW800 engine family--specifically, the PW814GA, for a project and we need to know some hard-to-find data. Does anyone knows where I ...
2
votes
1answer
226 views

What is the most recent turbofan engine that used steel for its bypass fan blades?

I haven't been able to locate any engines that use steel for the bypass fan. All sources suggest Ti and composites are used for blade construction. Apart from the weight steel could partially make up ...
2
votes
1answer
65 views

Is hybrid propulsion widely used by UAVs?

Is it common to have hybrid propulsion in UAVs used for terrain mapping with long endurance, short range and altitude? Is the technology and research mature enough to make hybrid propulsion? ...
2
votes
1answer
232 views

Can turboprops use a recuperator?

A recuperator is a device which extracts heat from the exhaust of a turbine and transfers it to the front air. This heats the air, which means the turbine uses less fuel to heat the combustion chamber ...
6
votes
3answers
362 views

Why don't turbofan engines have shrouds affixed to the fan blades?

For a turbofan to be efficient the gap between the blades and the shroud has to be extremely small. Why don't we just attach the shroud directly to the blades and let it spin as one? Would that ...
3
votes
3answers
248 views

Why don't piston engines require as heat resistant materials as jet engines?

Piston engines often get away with using aluminium as their heat exposed material, while even the early jets required inconel to operate. Is that because the combustion takes only, for example, half ...
0
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0answers
48 views

What is the engine shell temperature?

What are the highest temperature locations in the outer shell on an aircraft engine? Particularly, modern turbofans like the Trent 900 for example. I'm interested in the temperature constraints of ...
7
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7answers
3k views

Why don't bypass ducts in jet engines narrow down the flow to accelerate it?

Since decreasing the flow area increases flow velocity, why don't turbofan bypass ducts narrow down to produce more thrust?
3
votes
2answers
162 views

How has afterburner design changed since its inception?

I came across a NACA summary paper on the past 5 years of afterburner development and started reading cause it seemed interesting. However, a couple of pages in I scrolled back up and realized that it ...
1
vote
1answer
170 views

What is the temperature range of engine mounts connected to the pylon?

I want to know what is the temperature of the engine mounts in modern turbofan engines for example, Rolls Royce Trent 900. Also, what are the temperature considerations you need to make while ...
15
votes
4answers
4k views

Why hasn’t the Wankel rotary engine seen more use in aircraft?

The Wankel rotary engine seems to have several advantages over traditional reciprocating cylinder-and-piston designs. In general, they have a much higher power-to-weight ratio, less vibration, and ...
2
votes
0answers
123 views

How hot is the outer casing of a turbofan engine?

I am able to find temperatures inside different components of turbofan engines, but I can't seem to find what would be the temperature of the external casing/shell of the engine. For example, ...
0
votes
1answer
79 views

How to determine the number of compression stages given a compression ratio?

I have a personal project to design a gas turbine engine, the main problem that puzzles me is how do I determine the pressure rise in each stage of an axial compressor? Say, I'm planning on a 38:1 ...
5
votes
1answer
247 views

Why do the Comet's engines point outwards?

As it's visible from the images below, when looking at the plane from the top, the engines point outwards and they are banana-shaped, why is that? (unfortunately I couldn't find a real photo ...
8
votes
2answers
2k views

What is the purpose of a freewheeling unit in an helicopter, if a centrifugal clutch is already present?

Some helicopters such as the Bell 47 are fitted with a centrifugal clutch. Centrifugal clutch will engage only at certain engine RPM. If the engine fails, the engine RPM will reduce and the ...
0
votes
1answer
95 views

Why are inlet vanes used instead of variable geometry inlets to prevent compressor surge/stall?

Jet engine core axial compressors (that of subsonic turbofans anyway) are designed to keep air flowing the right way at max RPM(or close to it). Below that, the airflow slows more and more, and ...
1
vote
0answers
79 views

How to avoid shock (particularly Oblique shock) inside Cd nozzle?

Using the Area ratio (A/A*) and for the desired exit Mach number I have designed a cd nozzle. The Inlet total pressure (Po) and the total temperature (To) is calculated using Isentropic relations for ...
10
votes
4answers
9k views

How are turboprops and other propeller planes pressurized?

I know how most turbofan jets are pressurized: But it can't be the same with turboprops, as I don't understand how propellers can take in the air. Yet, planes like Q400s can fly above 8000', all the ...
1
vote
1answer
37 views

Considering a piston engined aircraft, what resistance pressure would be generated within its engine bay against its cooling intake?

Consider a piston engine with all its coolers and components within an aircraft engine bay. To cool this engine, cooling intakes are positioned facing the direction of flight. Now, the condition at ...
1
vote
3answers
461 views

Why weren’t large, high-power radial engines built to take advantage of the Meredith effect?

Most aircraft piston engines fall into two general categories:1 Radial engines (radials for short2) have their cylinders radiate out from the crankshaft in a star pattern; they tend to have a blunt, ...
3
votes
2answers
185 views

How do turbofan internals handle the load from the thrust?

To my understanding, turbofan engines get the majority of their thrust from the fan in front of the engine, up to around 70-80% while the core flow generates around 20-30%. Forward movement is ...
13
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2answers
2k views

Why don't NK-12 powered contra-rotating propellers turn in equal rpm?

The Kuznetsov NK-12 is a Soviet turboprop engine of the 1950s, designed by the Kuznetsov design bureau. The NK-12 drives two large four-bladed contra-rotating propellers, 5.6 m (18 ft) diameter (NK-...
5
votes
1answer
551 views

What is the purpose of the air inlets on an A320neo's pylon (LEAP-1A)?

What is the purpose of the air inlets on an A320neo's pylon (LEAP-1A)? Passive cooling, air bleed like in the 707, or something else?