Questions tagged [compressor]
As the name suggests, gas turbine engine compressors provide the compression part of the gas turbine engine thermodynamic cycle. There are three basic categories of gas turbine engine compressor: axial compressor, centrifugal compressor, and mixed-flow compressor. A fourth, unusual, type is the free-piston gas generator, which combines the functions of compressor and combustion chamber in one unit.
97 questions
3
votes
1
answer
453
views
How could jet engine spools get connected?
I understand that the design jet engines have two or three spools in order to make every component running within its optimal design. But that's still not clear to me.
So, a bit of confusion still ...
- 151
1
vote
1
answer
96
views
What do the variable bleed valves on a CFM56 engine look like when starting said engine?
What do the variable bleed valves look like internally when starting engines? Does it exist a video of the VBV in operation?
- 11
-1
votes
1
answer
283
views
Why don't jet fighters have fans?
Why don't jet fighters have fans in front? They only have a hole to suck air? I assume the compressor sucks the air. Is that enough?
See from picture below, this is an F-16 jet fighter. There is no ...
- 151
2
votes
1
answer
609
views
how could engineers find pressure loss location in jet engines?
What are the tools, software or devices that jet engineers use to know if there is loss of pressure in the air? Are they using only calculations to know how much air in vs out?
It's very interesting ...
- 151
4
votes
2
answers
2k
views
I'm having a hard time conceptualizing this statement from "The Jet Engine" by Rolls-Royce
This is taken from section 21 of Chapter 3, Compressors that discusses axial flow compressors in turbine jet engines.
The more the pressure ratio of a compressor is increased the more
difficult it ...
- 41
4
votes
0
answers
147
views
How does the Allison (now Rolls-Royce) CX-31 centrifugal compressor achieve a pressure ratio of 10?
Centrifugal compressors typically have pressure ratios up to around 7 or 8. But Rolls-Royce has a graphic showing the evolution of their line of small turboshaft engines that shows the compressors ...
- 41
10
votes
6
answers
3k
views
Function of the compressor in a gas turbine engine
I am trying to understand the importance of having compressed air in the combustion chamber of a gas turbine engine. As far as I understand it, the reasons are twofold.
Firstly, the compressor is ...
- 103
0
votes
1
answer
267
views
Decreasing Area of Axial Compressor
in axial compressor, why the area is decreasing until it reaches the combustor?
and if the answer because of the pressure is inversely proportional to the volume. that's happened when the temperature ...
0
votes
1
answer
127
views
Why do we take into consideration holes for pressure thrust in jet engine calculations?
In many sources related to jet engine thrust calculations such as https://www.jet-x.org/a8.html ,
pressure thrust of a module such as combustion chamber, nozzle or compressor, is calculated by front ...
- 244
3
votes
3
answers
869
views
How can flow in the compressor of a jet engine go back to the inlet?
In aerodynamic lessons and books about jet engines, it is always said that there is a risk that air flow in the combustion chamber or compressor can go back to reverse direction, towards the inlet if ...
- 244
-1
votes
4
answers
3k
views
Why do we consider that air comes into jet engine?
While calculating air pressure and temperature during cruise of jet engines, we consider that air comes into the jet engine inlet with our flight velocity.
But why? In fact, air stops stagnant in ...
- 244
0
votes
1
answer
137
views
What increases the rotational velocity of air in an axial flow compressor?
In an axial flow compressor as used in modern jet engines, the goal of a compressor rotor is to increase the angular momentum of the air by imparting an increase in swirl velocity. (Note: the goal of ...
- 974
1
vote
1
answer
455
views
Do compressors and turbines in jet engines end with rotor or stator?
I am trying to understand compressor and turbine design principle based on stators and rotors.
I know that turbines and compressors both have a rotating and fixed section that constitute a stage.
For ...
- 244
4
votes
7
answers
4k
views
How does a fan in a turbofan engine suck air in?
I watched lots of video related to sucking process of a fan in a turbofan engine, but I'm confused at a point.
In this link and many videos like this, I found the fan'...
- 244
7
votes
5
answers
3k
views
How do gas turbine engines and turbofan engines keep constant compressor side rpm?
How do the RPMs stay constant in a gas turbine engine? For example in car with piston engine, when you keep pressing the accelerator the rpms keep picking up, to keep the rpms constant you must let ...
- 295
0
votes
0
answers
142
views
What is the amount of bleed air required for de-icing? What is the power impact of this bleed air?
I was wondering if anybody has any rough equations/figures that answer the following questions.
What is the mass/flow rate of bleed air required for de-icing based on temperature of the air intake?
...
- 1
3
votes
1
answer
545
views
From which jet engine is this blade?
Some years ago I bought a compressor blade on ebay but I don't know which jet engine it's from.
It's quite light. I tried to determine the density by the help of my kitchen equipment and it's most ...
- 83
4
votes
2
answers
481
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,...
- 87
7
votes
3
answers
2k
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 ...
- 761
3
votes
2
answers
5k
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 ...
- 761
2
votes
2
answers
6k
views
What type of bearings are used to support the shafts in jet engines? [duplicate]
I would like to know which types of bearings are commonly used to support the shafts in jet engines and why. I also read something about hydrodynamic bearings, how common are they?
- 21
4
votes
1
answer
915
views
How does a C208B's climate control system that utilizes bleed air for cabin heat work?
I'm studying the systems on my first turbine-engine aircraft, specifically, a C208B.
I know that there is "bleed air heat" that mixes with re-circulated cabin-air. I know that the bleed air ...
- 9,072
0
votes
1
answer
250
views
Why is it that low fuel gauge is one indication of a compressor stall?
I am reading from my gas turbine engine class notes that apparently, one indication of compressor stall (besides the banging sounds, torque gauge low, N1 low, ITT gauge up, etc) is the fuel levels ...
- 439
4
votes
3
answers
3k
views
How are compressor disks connected to the shaft?
I am trying to learn how compressor disks and shaft are connected each other. I don't have any idea about the terminology so I couldn't find anything useful.
Here is a section view of a sample and I ...
- 101
2
votes
1
answer
2k
views
Do turbine and compressor rotate in opposite direction?
I have heard that they do rotate in opposite directions to maintain the equilibrium of the engine. That is the net force generated by the rotation is nearly equal to zero. But, I don't think the ...
- 1,567
0
votes
0
answers
118
views
How to compare compressors of different efficiencies and pressure ratios?
I have two different engines, the CFM56, and the CFM LEAP-X. I roughly know the design point (take-off) isentropic efficiency and the pressure ratio for the LPC/HPC for both of them which are ...
-1
votes
2
answers
631
views
What is a typical compression ratio in light turboprop aircraft propellers? [closed]
Does anyone happen to know a rough estimate of a typical light turboprop aircraft propeller's compression ratio? Something with 6-12 seats like a Cessna Caravan or Piper Malibu. Doesn't need to be ...
2
votes
2
answers
205
views
What do these temperature data listed in the EASA Type Certificate Data Sheet mean?
Could you tell me what is the Maximum Permissible Indicated Turbine Temperature (ITT) and the ambient limit temperature for sea level static thrust?
- 323
0
votes
1
answer
152
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 ...
- 323
0
votes
0
answers
84
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 ...
- 323
2
votes
3
answers
363
views
What causes air to move to combustor?
I know the pressure is highest at end of compressor. But what forces air to move low to higher pressure? Am i missing out something? I have heard seals are used to prevent leakage of air from ...
- 1,567
0
votes
1
answer
913
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 ...
- 611
0
votes
1
answer
315
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 ...
5
votes
2
answers
2k
views
Why is a centrifugal compressor in aircraft engine less susceptible to stall and surge?
I have came across a similar question here. Although the answer doesn't explain much about why and is somewhat vague. I have read that centrifugal compressor can achieve a higher pressure rise per ...
- 101
2
votes
0
answers
611
views
What is a compressor cascade?
Is a compressor cascade just the representation of the blade ring of an actual turbomachine? What is the difference between linear cascade and annular cascade? A diagram or a reference would be great.
- 121
7
votes
1
answer
617
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.
0
votes
1
answer
353
views
Will an axial compressor work with an ideal fluid?
Will an axial compressor, like the one described starting on page 275 of Mechanics and Thermodyanmics (PDF link), work if the flow was assumed to be ideal (i.e. incompressible and inviscid)?
...
- 201
8
votes
4
answers
5k
views
Do modern jet engines need igniters?
I've read that modern aircraft don't need spark plugs like conventional aircraft do, as the jet fuel autoignites once it's mixed with the hot air exiting from the compressors. Then why do aircraft ...
- 1,753
0
votes
2
answers
1k
views
Do the compressors and turbine rotate at the same speed?
Since the turbine and the compressors are connected to each other via a common shaft, do they both rotate at the same speed. Because I've read that in some jet engines (single spool engines) they don'...
- 1,753
4
votes
1
answer
334
views
Why are liquid ring compressors not used in a jet engine?
A question has been asked here before whether sliding vane compressors could be used in place of axial compressors on jet engines since they have a high compression ratio per stage (Why were rotary ...
- 2,544
3
votes
2
answers
264
views
Are compressor maps for multistage compressors drawn for one blade row or the whole compressor?
Apologies if this is a stupid question.
I am a little confused about compressor maps.
Are compressor maps such as this one, drawn for one blade row only or the whole compressor?
(source: Wikimedia)
...
2
votes
0
answers
64
views
Is there a way to determine maximum rpm for axial compressor due to material limitations?
I'm looking for RPM to Stress relation to determine maximum rotational speed that compressor/turbine blades can have without undergoing deformation due to centrifugal tensile stress.
I've come come ...
- 133
2
votes
1
answer
815
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 ...
- 618
2
votes
3
answers
1k
views
On a axial flow turbo fan or turbo jet engine what comes first the rotor or the stator?
I've been let to understand that one stage consists of a row of rotors and stators. But I'm not sure which comes first? Does the front fan blades make the first part of the stage (rotor) with a stator ...
- 618
21
votes
5
answers
14k
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 ...
- 341
4
votes
1
answer
2k
views
Are turbine and compressor blades and vanes cast or forged?
I was wondering how blades and vanes are typically made in commercial jet engines. Would you typically use investment casting to make compressor blades or just in the turbine section to accommodate ...
- 41
1
vote
0
answers
23
views
In the compressor characteristic, how do I calculate the minimum flow?
I have a small question, how do I determine the minimum flow point on the compressor characteristic? I.e. what is the safety margin on the curve?
- 21
1
vote
1
answer
207
views
In the compressor characteristic, what does this value represent?
$$ ? = \frac{m_t* \sqrt{T_3}}{P_3}$$
All I know is that it is a material property of a turbine, it has something to do with the mach number, and is used for calculating $W_T$. It's kinda similar to ...
- 21
2
votes
2
answers
5k
views
Is overall pressure ratio same as compressor pressure ratio for a gas turbine engine?
For a typical gas turbine engine, turbofan in particular, is the compressor pressure ratio same as the overall pressure ratio?
For modelling purposes can we use the same value of overall pressure ...
- 31
1
vote
1
answer
322
views
What values can/should be used for the isentropic efficiency of a compressor and turbine?
I was trying to model an turbofan aircraft engine using Matlab and Simulink. In the process I have fixed certain parameters to some specific values which are nominal operating values of the parameters....
- 31