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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5 votes
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Why isn't Yamaha EPeX300Ti more popular in aviation?

The answer to this question might be obvious to experienced aviators. But as an armchair enthusiast, I really couldn't find a satisfactory answer anywhere on the internet. Below two pages came from ...
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1 vote
1 answer
86 views

How to compute the mass flow rate for a turboprop at cruise given the static sea level value?

I am trying to obtain the mass flow rate of the Allison T56-A-15 used on the C130H at cruising altitude (so as to solve the Joule-Brayton cycle at cruising altitude). I know from "Turboshaft, ...
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  • 11
0 votes
1 answer
63 views

How to determine engine CG in order to calculate moments acting on it?

The aircraft has four engines mounted in pods under the wing. I know the values for the location of engine nacelle front face from the fuselage nose (longitudinal) and distance between engine ...
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0 votes
2 answers
105 views

Propulsion/ power plant

Let’s say I require 100Hp as stated by my calculations of Thrust for an aircraft- When finding a power plant for this, would it be better to use a power plant with more Hp or exactly that 100Hp please?...
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6 votes
4 answers
475 views

Why is China still heavily reliant on Russian turbofan engines?

According to Paul Schwartz, China is "still heavily reliant" on Russian turbofan engines: Beijing is still heavily reliant on Russian aircraft engines, however, due to the great difficulty ...
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4 votes
3 answers
396 views

Why do some jet engines have fewer fan blades than others?

I have found out upon researching jet engine fan blades that they can vary from 16 to 34. Why do they vary, I mean, does decreasing or increasing the number of fan blades have any performance impact? ...
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0 votes
1 answer
103 views

If I put two ductfans behind one another, would I got the sum of the rated thrust or other thrust values?

I am trying to design a VTOL system for a drone and I don't want to have extending motor arms that make it look like a quadcopter. I want to use duct fans and thrust vectoring nozzles. However, the ...
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-4 votes
1 answer
5k views

Would blade-less (Dyson style) jet engines work? [duplicate]

Is it possible to design an aircraft with blade-less (same concept as Dyson) design to generate thrust? What are some of the key benefits, drawbacks and examples of attempts (if any) at this kind of ...
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-3 votes
1 answer
101 views

Is this concept of a hybrid between a Turbine Engine and a Reaction Engine (Rocket) practical? [duplicate]

So, I don't understand much about engineering in general, but since this is a discussion forum, I like to think that this is just a thought exercise (because it is probably useless). So, the idea ...
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  • 453
3 votes
5 answers
2k views

Are there Hybrid Electric-Combustion Turbine Engines where only the compressor is electric driven?

So, from what I could understand about conventional Turbine Engines and its various types is that normally the combustion chamber ignites fuel with compressed air, rotating a low pressure fan which ...
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  • 453
0 votes
1 answer
130 views

Would this concept of Autogyro/Gyroplane be efficient or practical?

First, i'm quite ignorant on aerospace engineering, so I hope I don't make too many incorrect assumptions. If you don't know what an Autogyro/Gyroplane is, here is the Wikipedia article of it. The ...
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  • 185
0 votes
1 answer
317 views

What are the advantages and disadvantages of fluidic thrust vectoring on aircraft?

The Rockwell XFV-12 was a research project for combining supersonic speed with Vertical Take-Off and Landing, From wikipedia: The XFV-12 used a thrust augmented wing concept... in which exhaust would ...
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  • 185
3 votes
1 answer
137 views

Could small ramjets on the tip of propellers allow for supersonic spin of turbine blades?

Well, of course, if it was practical, someone would've already done that, but I'm still curious. As you can imagine, I'm an illiterate on the matter of aerodynamics, and even though supersonic ...
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  • 185
4 votes
1 answer
176 views

Thrust varaition of a Turbofan engine with altitude and mach number [duplicate]

my classmates and I are trying to find a mathematical model for a low bypass turbofan engine, we ended up finding a model given by Snorri on "General Aviation Aircraft Design", but the ...
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8 votes
2 answers
232 views

What are the design principles that result in thin, long-span, narrow chord main rotor blades?

Regardless of the overall design configuration of a helicopter, it appears that helicopters have main rotor blades that all fall into the class of ultrahigh aspect-ratio wing design: that is, you ...
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3 votes
2 answers
302 views

Airflow through axial flow compressor

So I'm reading the Gas Turbine Engine Fundamental, and suddenly come across the airflow passes through one axial compressor stage. I wonder why the Resultant Rotor Inlet Velocity is pointing downward,...
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7 votes
3 answers
1k views

Is this image of Compressor aerodynamics correct?

Image Source: Air Gas Turbine Technology by Treager, Chapter 5 The rotation direction of rotor shown seems opposite. If it is correct, these are the questions I would like to ask: Why the Y vector is ...
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0 votes
1 answer
101 views

How to determine the length of the CD nozzle?

I am designing a convergent nozzle as well as a CD(Converging-Diverging) nozzle. How do I find out the length of those nozzles? If the throat of the CD nozzle has 0 length then what should be the the ...
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0 votes
1 answer
83 views

What kind of signal is outputted from engine fire sensors

Engine fire sensor informs the pilot engine fire and triggers fire extinguisher to release their payload. However, fire extinguisher valves are controlled through pressure operated switches or ...
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1 vote
0 answers
67 views

Why pressure and temperature decreases along the length of a convergent nozzle?

I know that the pressure and temperature follows stagnation relations of pressure and temperature as well as area mach relation inside a convergent nozzle along the length. And according to that ...
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3 votes
2 answers
953 views

What is a ram recovery point?

As aircraft speed increases, thrust tends to decrease somewhat; as the aircraft speed reaches a certain point, ram recovery compensates for the losses caused by the increases in speed. The inlet must ...
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4 votes
2 answers
211 views

How much extinguishing agent is needed for an engine fire?

I am quite interested in the firefighting fluid tank choices in turbofan-equipped aircraft. As seen in this picture: Although this is only the APU, but the fire extinguishing agent bottle looks quite ...
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0 votes
1 answer
139 views

Why are there motive flows for the turbine pumps of Williams International FJ44-3A engine?

For my university project, I am designing the fuel supply of an aircraft using a Williams International FJ44-3A engine. Studying the related FAA TCDS, I read "Fuel from the motive flow port on ...
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2 votes
1 answer
185 views

What is the maximum Mach number that can be achieved at the exit of CD nozzle?

I understand that you can get Mach 1 at the throat of a convergent-divergent (CD) nozzle and after that you can have two roots, one is for subsonic and other is for supersonic. Considering the ...
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3 votes
3 answers
332 views

How do jet engines cool the gas in the combustion zone?

The adiabatic flame temperature of kerosene in air is 2093 C (source). Modern jet engines have a turbine inlet temperature (TIT) of 1700 to 1800 C. This is the max acceptable temperature before the ...
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0 votes
0 answers
51 views

What is the air bleed property from a GE H85-100 engine?

I am doing a university project to design a system to pressurize aircraft cabin for an aircraft using the GE H85-100 engine. I want to know from which stage of compressor the pressurized air is coming ...
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7 votes
0 answers
235 views

Engine Bearings Damage in Radial Engines

Studying the P47's dive performance in DCS, I noticed how it's easy to damage the engine bearings if you windmill the prop at high speed. Doing some research, I discovered that all radial engines are ...
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1 vote
1 answer
241 views

Why aren't air turborockets used in military fighters?

Why aren't air turborocket engines used in jet fighters? Few Third World countries have the capability to manufacture high quality turbine blades. Thus, why not use air turborocket engines for the ...
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11 votes
1 answer
1k views

Which popular turboprop engine feathers its propeller blades with each shutdown?

Chapter 12 of the FAA Airplane Flying Handbook, discussing multiengine flying, goes into quite a bit of detail in the propeller section about how most feathering-propeller-equipped engines on ...
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3 votes
2 answers
256 views

Why in a CFM56-3 is vibration measured in displacement for N1 and in velocity for N2?

N1 is measured in mils (thousandth of an inch) and N2 is measured in IPS (inches per second). Why are different methods used?
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2 votes
1 answer
119 views

BHP increases with Altitude

Searching on internet, I found some performance charts of the Merlin Engine BHP output: As you can see there is an increase in BHP,(mainting a constant Boost Setting), until reaching the critical ...
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4 votes
2 answers
329 views

Are turbine blisks common in jet engines?

This comes from a slightly related question about blisks. A blisk is a single component shaped like a disc with blades on it. This can be for compressors or turbines. I want to ask about the turbine ...
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2 votes
1 answer
160 views

Why is the RPM limit on a Lycoming IO-540 different in the -C and -D versions?

On a Lycoming IO-540, it seems there is a Max RPM difference between the -C and -D versions (and thus a max HP difference too). Does anybody know what is different in the engines that causes this, or ...
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4 votes
1 answer
361 views

What would be the advantage of a Puller vs. Pusher configuration on Embraer's new Turboprop?

Embraer recently teased a turboprop aircraft with aft-mounted, open rotor engines. Why would this aircraft not use a pusher configuration? The reasons that are frequently stated as a benefit for a ...
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  • 1,735
1 vote
0 answers
105 views

Why doesn't the -30% SFC fully account for the dramatic reduction in fuel consumption compared to the 1960s?

In looking at the specific fuel consumption (SFC) of some aero engines I find that for example, the Rolls Royce Conway turbofan engine had typical cruise SFC of 0.874 lb/(h lbf) whilst the most modern ...
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9 votes
1 answer
371 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 ...
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0 votes
1 answer
212 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 ...
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3 votes
2 answers
123 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 ...
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0 votes
1 answer
222 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....
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2 votes
1 answer
176 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 ...
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  • 1,475
6 votes
1 answer
132 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.
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3 votes
4 answers
399 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 ...
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0 votes
2 answers
126 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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1 vote
0 answers
32 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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3 votes
2 answers
276 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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  • 715
1 vote
3 answers
199 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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6 votes
1 answer
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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  • 6,467
7 votes
1 answer
526 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 ...
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  • 73
4 votes
1 answer
1k 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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  • 155
23 votes
1 answer
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 ...
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