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.

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

I have a personal project to design a gas turbine engine, the main problem that nags me is how do I determine the pressure rise in each stage of an axial compressor? Say, I'm planning on a 38:1 engine ...
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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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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 ...
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Why is Active Flow Controlnot used in Fan And Compressor of aero engines?

Why active flow control is not used in the compressor and fan of aero engines even though they provide several advantages in terms of performance? what are the challenges of using active flow control ...
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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.
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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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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)? ...
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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 ...
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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'...
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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 ...
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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) ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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?
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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 ...
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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 ...
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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....
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Are low pressure (LP) compressors and booster compressors the same thing?

Based on the above picture, are "LP compressor" and "Booster compressor" different names for the same thing or are they actually different things?
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Do any propellers/propfans use stator vanes? Why is this not a commonplace feature?

I understand that axial-flow turbine engines generally include stator vanes behind every(?) compressor and turbine stage. This makes quite intuitively sense, because without them the rotating blades ...
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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 ...
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How to understand turbo machines?(compressors,fans,pumps,turbines,etc..)

From what I understood, the energy transfer between the blades and the fluid(fluid to blade or blade to fluid) occurs due to the curvature of the blade.Its because of this curvature the stream of the ...
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How are compressor maps drawn?

I've always thought they are empirically derived: once you have your axial compressor phisically in a bench, you set both a rotational speed and a mass flow throught the turbomachine then you measure ...
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I wonder if it's possible to make a “compressed air” turbine engine [closed]

I wonder if it's possible to make an efficient turbine engine that uses only hot compressed air to move but only that, meaning there is no ignition involved. To put it simple can we use compressors ...
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What is significance of N1 and N2 in Jet engine? [duplicate]

Why N1 Low pressure compressor RPM and N2 High Pressure compressor RPM are monitored in jet engines ? Why specifically compressor RPM rather than turbine RPM ? What do N1 and N2 signify in terms of ...
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Why does a turbine engine compressor ratio affect stagnation pressure?

This might just be a misunderstanding on my part, but in an ideal Brayton cycle, the flow through the compressor and turbine is isentropic, meaning $\Delta s = 0$. However, usually you are given the ...
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How does fuel flow and altitude affect the compression ratio of jets?

Does the compression ratio of jet engines change with altitude and/or with the rate of fuel flow?
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What does the term “loading” refers to when we talk about Blade loading and Stage loading in Turbomachinery?

I have been reading about the term Blade Loading and Stage loading in case of Axial Turbines and Compressors, however, I would like to know what does the term "loading" here exactly refers to? What I ...
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Why does the Pressure ratio across the compressor increases when the mass flow rate is reduced?

I am learning about Rotating stall in Axial Flow Compressors. So, when we throttle the compressor then there is Pressure Rise and later after the peak pressure rise tip stall starts to appear. But I ...
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Could compressor stalls be caused by air in supercritical conditions?

It is likely that in compressors of jet engines appear conditions that cause the intaken air to become supercritical, cf Is the air in a jet engine supercritical? . Is it possible that ...
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Is the air in a jet engine supercritical?

Nitrogen has a critical point of 126.2 K and 3.4 MPa (34 bar). Air contains 75 % of nitrogen For example, nitrogen has a critical point of 126.2 K (−147 °C) and 3.4 MPa (34 bar). source : https://...
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Why do compressors constrict flow if this decreases pressure?

An axial compressor (and a ramjet intake, for that matter) is commonly depicted as decreasing the volume of air travelling through as we move closer to the combustion chamber. In axial compressors, ...
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What is the difference between axial compressor blades and centrifugal compressor blades?

Is there a particular difference? The way they're overhauled is the same ? (I mean do we use the same overhauling methods ?)
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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 ...
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Is N1 and N2 and any N speed the revolutions per second for the rotor blades of compressors? [duplicate]

For example the Airbus A350 has three N speeds I think is called Nucelle speed and N1 is for the fan or LP compressor, N2 is for the IP compressor and N3 is for the HP compressor. Even on the Airbus ...
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Why does the Trent XWB have intermediate compressor stages?

I realized that the Rolls-Royce Trent XWB on the Airbus A350 has intermediate compressor stages. Why is that? Other engines like the CFM56 or IAE V2500 that power most of the A320-family have low ...
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How do the compressor stages keep spinning after start in a free turbine?

In a ‘free’ (or uncoupled) turbine engine (specifically the Rolls Royce C20-250), what is spinning the compressor blades (N1) after start? It can’t be N2, because it’s a free turbine. I don’t think ...
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What engine are these fan blades from?

I bought these from a metal scrapper and paid about $30.00 total figuring they're worth more than that in cool factor. Problem is they aren't nearly as cool if I can't figure out what engine (and ...
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What is the purpose of blades on a compressor?

What is the point of having blades on a compressor. I heard on NASA that it alters the flow but how would this help. As the flow of a fluid increases, the pressure decreases, and vice versa. The ...
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Why are there curved blades on jet engines? [duplicate]

On the fan and comssorssor and turbine for that matter there are blades and they are also curved. Im already confused beucase the fan has blades but wouldn't it blow out air not suck in air? Why are ...
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How does the size of each stage vary in a high pressure compressor?

Is it true that in the high pressure compressor the stages and blades on the stages get smaller as it goes on?
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How does the FADEC prevent compressor stall during rapidly increasing thrust demand?

My understanding is that if the demanded thrust is increased rapidly on a jet engine (for example going from nearly idle to TOGA during a go-around), the engine will likely experience a compressor ...
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Why do large turbofans generally have many more LP turbine stages than HP turbine stages?

In almost every large turbofan I see, the LP turbine stages outnumber the HP turbine stages by a factor of at least 2. Here's a photo of the RR Trent 900: The Trent 900 (like most Rolls-Royce ...
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What are the specifications of the General Electric J85 engine compressor?

On the internet I can't seem to find all the specifications I need. Mostly I'm looking for the tip and hub radius and the angular velocity of the blades. Thanks.
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Does the compressor stationary vane have stagger angle?

Does the compressor stationary vane have stagger angle? ( stagger angle is the angle between chord of the blade or vane with engine's longitudinal axis )
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Why does the LP compressor rotate in the opposite direction of the HP compressor?

Why does the LP compressor rotate in the opposite direction of the HP compressor in some multi-spool turbine engines?
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What is the material composition of aircraft compressor blades?

I read up that aircraft compressor blades are generally made out of titanium. I was curious as to why is titanium the choice of material used for aircraft compressor blades? What alloys are involved ...
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Is a compressor blade slowing down the airflow or accelerating it?

When a jet aircraft flies at maximum speed, are compressor blades actually a barrier to the air flow, or is the airflow accelerated by the compressor?