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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2 votes
3 answers
525 views

Why weren't WWII piston aircraft able to fly at 500mph?

So, I just noticed that typical WWII piston engine fighter aircraft had a power to weight ratio of around 300W/kg, even at gross weight and altitude. This means that if we assume that an aircraft has ...
0 votes
5 answers
207 views

How/why does engine torque and horsepower affect aircraft speed? [duplicate]

I'm curious as to why torque and horsepower affect an aircraft's speed. AFAIK, it's only the engines RPM that affect speed, right? Does this mean an engine's torque/horsepower only affects the speed ...
2 votes
2 answers
158 views

Confusing justification for new engines for Bomber B

https://en.wikipedia.org/wiki/Bomber_B With engines in the 2,000 to 2,500 hp range, twin-engined aircraft would have considerably more surplus power, allowing for much greater payloads. In theory, ...
9 votes
2 answers
996 views

Why is the inlet cone on some subsonic engines conical (sharp)?

An inlet cone, as far as I know, is a component on an engine to guide the intake air smoothly into the compressor stage of a jet turbofan engine, it performs as a fairing(aerodynamic covering)of the ...
3 votes
2 answers
598 views

What is the general operating temperature of Free Piston Turbine Engines?

The turbine in turbine engines can face temperatures from the combustion chamber up to 1700ºC, but I can't find any information on the operational temperature of free piston turbine engines. I'm ...
3 votes
2 answers
766 views

On a small/micro jet engine, can the turbine blades and vanes be made out of ceramic?

I am researching on how to make a small jet engine, and trying to figure out the materials for rotor and stator blades just after the combustion chamber so that they can hold up to the temperatures ...
0 votes
1 answer
111 views

Coordinate system in aircraft. Question about step between lines

Good day! Can you help me? I doing a restoration of the plane's geometry. I want to do restoration use a theory. But I have not information about step (size) between B.L. (W.L.) lines. As example - ...
4 votes
0 answers
126 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 ...
1 vote
1 answer
124 views

Exhaust temperature of CFM56 engines range (Nozzle downstream temp)?

EGT is available but not the temp of the exhaust nozzle in the CFM56 series.
7 votes
1 answer
3k views

How big would a single propeller need to be on a 737?

If you wanted a 737 to have the same design as a single prop light aircraft (i.e. just one prop on the nose, no turbines, APUs or other engines) - how big (and how fast) would the propeller have to be ...
40 votes
11 answers
18k views

Why do new jet engines cost billions to design?

This question might come off as crude because it involves people's salaries, but I do not understand why new designs of large turbofans cost many billions of dollars to design. For example, the Pratt &...
0 votes
1 answer
169 views

Can you augment turbofan thrust using steam injected into the bypass?

Would using waste heat from the core exhaust to turn water into steam increase takeoff thrust when injected into the bypass before/aft of the fan? If so, which would be better? Could this possibly ...
0 votes
1 answer
71 views

Humidity and its effect

We know that humidity degrades engine performance. Is there any charts or tables which quantify effect on engine performance due humidity? The question is specific to helicopters.
6 votes
1 answer
632 views

Why do modern turbofans have swept blades?

(Picture sources: CF6 and GE90) Aircraft have swept wings for two reasons: It reduces the thickness-to-chord ratio of the effective chord, which is ideal for flight at higher Mach numbers. At ...
0 votes
2 answers
238 views

Why aren't ducted rotors used in gas turbines?

I am wondering why (for what I know) no gas turbine employs ducted enclosures for blade arrays on rotor stages. I tried to search the internet for resources but I couldn't find anything related (so I'...
1 vote
1 answer
105 views

How would the shock-ramjet engine work?

I discovered a new theoretical engine called the shock-ramjet (schramjet) and I was wondering, how would it work exactly? I've read that its a high-speed engine that could be used around Mach 10, but ...
6 votes
7 answers
3k 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 ...
3 votes
2 answers
779 views

How are the compressor and turbine disks connected?

What is the typical way the compressor and turbine disks connected to (LP/HP) shaft ? How are the disks connected to each other (e.g., curvic coupling, bolts or others ?)
2 votes
1 answer
169 views

Turbofan engine fan blade leading edge fairing?

A lot of aircrafts feature a leading edge fairing for the wing, at the connection with fuselage, in order to reduce the airflow interference. Aerodynamically speaking, those fan blades in the turbofan ...
4 votes
1 answer
216 views

aerodynamic forces on an engine cowling

In Mendenhall's book about the Gee Bee racers, he describes that on the Models Z, R-1, and R-2, there was a strong tendency for the engine cowl to get pulled forward and into the prop during races, ...
6 votes
1 answer
436 views

Why should the dust protection on the Mi-17 helicopter not be used above 3000m?

The Russian Mil Mi-17 helicopters have a dust protection device fitted at engine intake (see the rounded part in front of the intake): Its checklist gives an altitude limitation from sea level to ...
8 votes
2 answers
466 views

Why do the Comet's engines point outwards?

As it's visible from the images below, when looking at the plane from the top, the engines point outwards and they are banana-shaped, why is that? (unfortunately I couldn't find a real photo ...
5 votes
4 answers
679 views

Would the combustion chambers of a turbine engine generate any thrust by itself? [duplicate]

Well, I know that the combustion chambers drive the compressors, and the reaction occurs, and all that stuff. But let's imagine that somehow someone is converting a turbine engine (turbojet, turboprop,...
14 votes
1 answer
2k views

What are those things on the B747 engine pylons?

I noticed some dots and lines on the Boeing 747 engine pylons. What are they? The above image is as seen in this video at 2:18.
46 votes
4 answers
14k views

What is this hole at the front of the engine pylon on a Boeing 707?

Images of the Boeing 707 show a hole at the front of the engine pylon just above the engine. Can someone please tell me what is the purpose? Also why do images show the hole absent on the left outer ...
7 votes
1 answer
2k views

What is the purpose of the air inlets on an A320neo's pylon (LEAP-1A)?

What is the purpose of the air inlets on an A320neo's pylon (LEAP-1A)? Passive cooling, air bleed like in the 707, or something else?
0 votes
0 answers
53 views

Do we use static pressure in thermodynamic cycles like brayton instead of total pressure?

I observed that pressure plotted in the graph above increases from 0 to 1. 0 is inlet entrance and 0' (not shown in the graph) somewhere between 0 and 1 is compressor entrance. Now, we know that at ...
8 votes
2 answers
884 views

Where exactly is the engine compartment, remarked in yellow?

Where exactly is the engine compartment, remarked in yellow? We know that normally the air going to the engine passes through the air filter. But when we open the alternate air valve, where does the ...
1 vote
1 answer
814 views

What is the purpose of variable stator vanes in the power turbine part of a free shaft gas turbine?

both M1 Abrams tank and T-80 tanks have free shaft gas turbine engines and both of their engines have variable stator vanes in their power turbine part. It says in the picture below that these ...
9 votes
7 answers
3k views

Why don't bypass ducts in jet engines narrow down the flow to accelerate it?

Since decreasing the flow area increases flow velocity, why don't turbofan bypass ducts narrow down to produce more thrust?
4 votes
3 answers
2k views

In high-altitude piston aircraft, what type of forced induction (boost) is used?

In high-altitude piston aircraft, what type of forced induction (boost) is used? Turbocharger or supercharger?
0 votes
1 answer
135 views

The F104 tail pipe is not parallel to the runaway when the aircraft taxi.What is the reason?

The tail section is upward for clearance or to vector up the engine exhaust that will help to rise the nose when the aircraft take-off?
3 votes
1 answer
149 views

Was there any attempt on making a turbofan for mach 1-2 with a "decelerator" air intake?

What made me ask this question is the SR-71 hybrid engines and the efficiency difference between certain engines. Here is an article from wikipedia showing the efficiency of the engines accordingly to ...
-7 votes
1 answer
186 views

If they really wanted to, COULD they make a 100% fail-safe airplane? [closed]

With literally every single electronics device that I have bought in the last X years breaking very quickly or immediately, and being of horrible quality, this thought keep popping up in my mind: If ...
4 votes
0 answers
427 views

RR Ultrafan: Why the dramatic change of fan blade design?

The Rolls Royce Ultrafan prototype has been in development for a few years and has usually been seen in the media with very distinctive curved leading edge design as such: However, this week (...
5 votes
3 answers
3k views

Would a ducted fan with a nozzle like a jet engine have more thrust than a normal ducted fan?

I'm trying to design a miniature ducted fan engine for a small project, but I'm not too sure how much contraction should happen between the fan and the end of the engine, if at all. Engines like this ...
24 votes
4 answers
7k views

How did the propellers on the B-29 stop perfectly in sync?

In the photos below, the propellers on the B-29 props all stop in the same position. Is this done by hand, it is this automatic?
2 votes
1 answer
170 views

Is there a good online source on rotating detonating pulse engine?

I can't find a clear presentation that would explain the workings of a rotating pulse detonation engine graphically, only useless (to a layman) cfd simulations of the combustion chamber. Please share ...
5 votes
3 answers
465 views

How is lift transferred from rotor to chassis (or weight, the other way around)?

I am trying to find out how a helicopter rotor's lift is transferred to the chassis. Equivalently, how is the weight of the helicopter transferred to the rotor blades? While looking for this online, ...
5 votes
0 answers
1k views

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 ...
6 votes
4 answers
998 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 ...
1 vote
1 answer
166 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, ...
9 votes
2 answers
3k views

What is "Boost"/"Super Boost" in the PW127M/N?

This incident describes rejected take-off due to the "boost" being inoperable. The reason for the RTO is obvious: engine power lower than expected. But what is this ominous "boost" technology?
0 votes
1 answer
223 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 ...
0 votes
2 answers
120 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?...
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 ...
4 votes
3 answers
1k 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? ...
8 votes
5 answers
10k views

Why is there a pressure drop in the combustion section of a jet engine?

This image, referenced in this question, shows in green the pressure value in a jet engine: The combustion section between compressor and turbine is where fuel is injected, mixed with air, and ...
5 votes
4 answers
1k views

Why weren’t large, high-power radial engines built to take advantage of the Meredith effect?

Most aircraft piston engines fall into two general categories:1 Radial engines (radials for short2) have their cylinders radiate out from the crankshaft in a star pattern; they tend to have a blunt, ...
0 votes
1 answer
302 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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