Questions tagged [turbojet]

A type of jet engine where all the air passing through the engine is used to burn fuel and drive a turbine as well as generating thrust.

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7
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1answer
221 views

What causes the horn-like noise during the start-up of some jet engines?

Here's the specific sound I'm talking about (it starts specifically 56 seconds into the video, as well as at 2:02 for the second engine): I've only really heard that ...
3
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2answers
152 views

Is the well known textbook-formula for net-thrust oversimplified or do I have a misinterpretation?

In order to understand how Jet-Engines works I came across the "famous" formula for net-thrust: https://en.wikipedia.org/wiki/Turbojet#Net_thrust $F_{thrust} = Q_{out} \cdot v_{out} - Q_{in}\...
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5answers
4k views

Do jet aircraft have a better glide ratio than propeller aircraft in general? If so, why?

Being fond of aviation, I play with software simulators a lot. I have noticed that while jets seem to be able to glide for a long distance even at zero throttle, propeller aircraft need to be ...
6
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1answer
3k views

Can you identify this engine?

I am studying Aircraft mechanics currently, and in our academy we have some aircraft engines and different types of them, and I need please your help to know the reference of one of them, and if it is ...
2
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1answer
114 views

KSEE LOC-D conundrum

Consider the LOC-D at KSEE and note the Alternate Minimums criteria. 99.9% of the time, the winds strongly favor 27R; The tower closes at 1900 PT currently (usually at 2100 PT non COVID times); LOC-D ...
0
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1answer
80 views

How do I find out the fuel consumption of the PT6A for a lightly loaded aircraft?

The Fuel consumption of PT6 engines provided by manufacturers are as follows. Cessna Caravan - Consumption ~47? GPH. At full load at ~160? Kn. Quest Kodiak - Around 49 GPH at full load at ~170 Kn ...
2
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2answers
254 views

Is it true that high-bypass engines are inherently inefficient at higher speeds?

Power consumption=Kinetic energy=$1/2mv^2$. Thrust=momentum change=$mv$. I keep being told that aircraft engines are most efficient when their exhaust velocity closely matches the freestream. The ...
2
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1answer
124 views

Does jet engine exhaust velocity relative to itself remain constant despite speed changes?

Maybe this is a stupid question. I seem to have been told, the velocity of the exhaust leaving an airbreathing jet engine relative to the engine, is constant despite changes in airspeed. However, to ...
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0answers
44 views

Why Turboprop engines are better than turbojet at low altitude and speed? [duplicate]

Please explain the Aerodynamic or engine considerations which makes turboprop more efficient at low altitude n low speed as compared to turbo jet.
-2
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1answer
141 views

Rocket Thrust vs Air breathing jet engine why is a rocket better [duplicate]

What are design dynamics that give the rocket engine higher thrust than an air breathing jet engine of similar size in comparison to a turbo jet engine, turbo fan engine, high by pass turbo fan engine,...
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0answers
115 views

How do the contrarotating turbines work in the F-119-PW-100?

I was reading about the F22 Raptor and found out that its powerplants use contrarotating turbines. How does this work Also, if the spools and their connected compressors are rotating in opposite ...
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0answers
194 views

Why did the B-52 never have a JT4A-powered version?

All versions of the B-52 use the Pratt & Whitney JT3C turbojet (except for the last version, the B-52H, which uses the JT3D low-bypass turbofan instead). Problem: the JT3C is a horribly anemic ...
20
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8answers
25k views

What is the difference between turbojet and turbofan engines?

What is the difference between a turbojet engine and a turbofan engine? I know that both of them have a fan and have turbines but how to distinguish them?
9
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3answers
1k views

Why is thrust available constant with speed for turbojet engines, when it varies with speed for turboprop engines?

Similarly, why is power available (nearly) constant with speed for a propeller engine, while it varies for a jet engine?
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1answer
521 views

What is the air/fuel mixture ratio in a turbojet engine?

How does it relates to stoichiometry ? What are the possible extinction accidents related to air/fuel mixture ratio ?
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2answers
392 views

How does an engine work when an airplane has $v=0$ on the ground?

I mean, for a turbofan: $$ T= \dot m_{air,h} (1+f) v_{e,h}+ \dot m_{air,c} v_{e,c}- (\dot m_{air,h}+ \dot m_{air,c} ) v_0+ (P_{e,h}-P_{amb} ) A_{e,h}+ (P_{e,c}-P_{amb} ) A_{e,c} $$ but $$ \dot m_{air}...
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3answers
340 views

Can a gas turbine be able to switch from torque to thrust?

Can a turbine engine be switched from providing torque (like a helicopter) to the rotor to transfer power to provide exhaust thrust (like a jet plane)? Related: BV-347 upgrade this way?
0
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1answer
131 views

Why can't turbojets or turbofans be overtemped or overtorqued the way turboprops can?

Turboprops that aren't FADEC controlled can be overtorqued or overtemped if the power lever is moved too far forward yet I have never heard of a jet that can't be "firewalled", FADEC or not. Why is ...
12
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2answers
1k views

Are centrifugal turbojets easier to make than axial ones?

Looking at the history of jet engines, I noticed that the British first made centrifugal-types, but the Germans went straight into axial-types. Which type is easier, if any? By that I mean, which ...
0
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1answer
4k views

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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8answers
5k views

Why do we refer to “power” for turboprop engines and “thrust” for turbojet/fan engines?

In jet engines, I read that thrust is related to the fuel flow rate, whereas in turboprop engines power produced is related to the fuel flow rate. What is the reason and brief math behind this?
10
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2answers
793 views

When were the last subsonic turbojet-powered airliners retired from commercial passenger service?

The very first jetliners (Comet, Tu-104, Caravelle I-VI, 707-120/-220/-320, DC-8 series 10-30, original 720, CV-880) all used turbojet engines, turbofans not being available until later; when ...
3
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1answer
394 views

What is the difference between active tip clearance control system and passive tip clearance control system in turbine?

What are the main differences between turbine active tip clearance control system and passive tip clearance control system?
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2answers
868 views

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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2answers
403 views

How can I determine specific heats of gases for turbojet engine calculations?

I'm in a combustion lab and we are performing experiments on a turbojet engine. However, I am having some trouble calculating the exit velocity and compressor/turbine powers of the engine. Consider ...
2
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2answers
449 views

Can a turbojet jet or turbofan powered aircraft land and take off from water?

Can a turbojet jet or turbofan powered aircraft land and take off from water? How much clearence from the water surface would it need for its engines so that it does not suck up water?
7
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2answers
433 views

What exactly does the MB-326's 'relight' button do?

The following picture shows the engine throttle of an Aermacchi MB-326, which is powered by the Rolls-Royce Viper turbojet: (source - all photos © Drive&Fly Model Club) I wonder what exactly the ...
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2answers
118 views

Fans of tubofan jet engines

Does the thrust of the fan in a turbofan jet engine decrease proportionally with decrease in the diameter of the fan? As the fan in a jet engine is responsible for over 70% of the total thrust can a ...
15
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1answer
12k views

Which jet engines have the highest thermal efficiency?

Some automakers (Mercedes-Benz, Toyota) have recently been making news about the improved thermal efficiency of their engines, stating that they reached the 50% mark. I was wondering if it was the ...
2
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1answer
1k views

Are there any differences between turbofan and turbojet engines besides bypass air? [duplicate]

I think I understand both engine types, but I am just wondering am I right in saying that the only difference between the two types of engines is the bypass air (i.e. a turbofan is just a turbojet ...
10
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2answers
735 views

Why were turbojets the first kind of turbo-engines, instead of turboprops?

During WW2, the first jet engines appeared en mass in combat aircraft. Britain and Germany made the first ones. But why were turbojets first? Why not turboprops, which are easier since the turbo-...
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2answers
1k views

Are there turbofan/turbojet analogues to a centrifugal-compressing jet engine?

Axial-compressor jet engines fall into two categories (and only two as far as I'm aware): turbofan and turbojet. I'm wondering if centrifugal-compressor jets also have such a distinction or something ...
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1answer
1k views

How small can turbojet engines be made whilst remaining fuel efficient, light, cheap, and producing enough thrust to carry a human, gas, and casing? [closed]

I've seen many videos of small turbojet engines (small enough to hold in your hands) that produce 30-40 pounds of force. If you mounted a couple of these on a small craft, that wouldn't even support ...
6
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2answers
356 views

Why is a turbofan engine less efficient when air leaks over fan blade tips?

Image source I understand part of the reasoning for minimal clearance between the casing and the fan blades, is to have the larger fan blade possible, which generates a larger low pressure area to ...
4
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2answers
177 views

What structural design methods were used for early turbojets?

I have had this question for long time. Can anyone please give me some references on early turbojet engine design methodologies? For example P&W J57 which was designed in early 1950's: How were ...
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2answers
127 views

Is there a way to calculate thrust without running experiments?

Is there any way to calculate the thrust generated without conducting experiments? In my case I need to figure out thrust generated by electric duct fans and/or turbojets.
5
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1answer
569 views

What is the actual exhaust velocity of the exhaust from the J58 engines at cruise (Mach 3.2)?

The SR-71 ran on two J58 turbojet engines and cruised at Mach 3.2. What I want to know is, what is the actual exhaust velocity (relative to the airplane itself) of the jet exhaust at those conditions?...
3
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2answers
437 views

Are there cases of a thrust reverser used on a turbojet engine?

In the case of a turbojet (with no "cold" bypass flow), the airflow being directed forward by an hypothetical thrust reverser can be really hot. Depending on the location of the engine, this flow may ...