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.
28
questions
2
votes
0answers
125 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 ...
18
votes
7answers
10k 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?
0
votes
0answers
27 views
What is the flow rate through the bypass tubes on the J58 engine?
Does anybody know how large the mass flow rate through the bypass tubes on the Pratt & Whitney J58 engines at subsonic and supersonic conditions is? Also is there any information available to find ...
8
votes
3answers
308 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?
1
vote
1answer
77 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 ?
1
vote
2answers
386 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}...
1
vote
3answers
271 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
votes
1answer
107 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 ...
11
votes
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
votes
1answer
2k 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 ...
26
votes
6answers
4k 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
votes
2answers
569 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
votes
1answer
254 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?
0
votes
2answers
510 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 ...
1
vote
2answers
213 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
votes
2answers
387 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
votes
2answers
334 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 ...
1
vote
2answers
111 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 ...
14
votes
1answer
9k 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
votes
1answer
1k views
Are there any differences between turbofan and turbojet engines besides bypass air?
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 ...
9
votes
2answers
676 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-...
4
votes
2answers
866 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 ...
0
votes
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
votes
1answer
240 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
votes
2answers
164 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 ...
1
vote
2answers
121 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
votes
1answer
491 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
votes
2answers
364 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 ...
