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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2answers
88 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 ...
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0answers
24 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.
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2answers
143 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 ...
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3answers
174 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 ...
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0answers
39 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 ...
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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:
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1answer
201 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
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1answer
945 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://...
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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 ...
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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
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1answer
83 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 ...
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2answers
231 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 ...
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0answers
54 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 ...
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2answers
236 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 ...
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1answer
123 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?...
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2answers
5k 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?
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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 ...
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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 ...
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1answer
409 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
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1answer
123 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 ...
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0answers
32 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
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1answer
219 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
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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
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1answer
222 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
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3answers
325 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
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3answers
246 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 ...
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0answers
46 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 ...
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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?
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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 ...
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1answer
158 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 ...
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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 ...
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0answers
116 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, ...
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1answer
67 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 ...
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1answer
242 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 ...
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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 ...
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1answer
88 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 ...
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0answers
66 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 ...
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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 ...
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1answer
35 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 ...
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3answers
430 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, ...
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2answers
179 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 ...
12
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2answers
1k 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-...
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1answer
482 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?
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1answer
130 views

Which compressor is more like to surge and stall - axial or centrifugal?

I am studying about stall and surge in rotodynamic compressors and want to understand which one is more prone to these phenomena.
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1answer
268 views

How to calculate the number of blades?

Inspired by building a new drone, I got lost in curiosity. What if I have a fixed length of rotor blades and a target amount of lift I want to, well, lift. How do you calculate the number of blades? ...
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1answer
71 views

Could high density abrasion-resistant ceramic turbine blades allow for the use of borane fuels?

In the late 1950s the U.S Air Force searched for a fuel with similar characteristics to jet fuel but with higher energy density allowing longer flight range for bombers. In 1947 the British had ...
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6answers
8k views

Do turbofan engine cowlings dilate during spool-up?

I was watching this Youtube video, portraying a Fokker 70 taking off. I wouldn't have noticed if it weren't for a comment, but during spool up (~ 3:24 in the video), it appears as if the engine ...
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4answers
9k views

Are jet engines designed in a way to make an explosion result in the least damage possible?

I know most engines are super reliable today, but do manufacturers do anything to at least make an explosion result in the least damage possible?
36
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1answer
7k views

Do the Mt. Everest rescue helicopters have modified engines to operate at high altitudes?

There are so many climbers on Mt. Everest today that there is now a helicopter rescue service there. They operate rescue up to 21,000 + ft. Because this is essentially stationary service it seems that ...
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1answer
59 views

Are solid fuel rocket engines designed differently and how? [closed]

How do solid fuel (Hydrazine, UDMH) and oxidizer (N2O4) differ in design from cryogenic rocket engines such as LH2 and LOX? Are there differences related to temperature, material design, turbopumps, ...