Ideal night bomber for RAF: how would've you done it? (1 Viewer)

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If you have a working turbo-prop you have a working jet engine. The turbo prop is NOT a stepping stone to the the JET. It is a JET with EXTRA bits bolted on to give greater propulsive efficiency at low/medium speeds.

You might be surprised to learn that the first axial flow gas turbine that successfully ran - in Germany, naturally, was designed as a turboprop. This was the work of Herbert Wagner; he worked with Junkers to build a gas turbine powerplant for the EF-61 high altitude research aircraft. There's also quite a difference in the propulsive energy output of a turbo-jet and turbo-prop; in the latter the hot gasses produced after combustion are there purely to drive the turbine - thrust is produced by the propeller - as you probably know already.:)

British scientist Dr A.A. Griffith was drawing up complex ideas for advanced multi stage axial flow turbines to drive propellers before Whittle had begun tinkering; Griffith is one of the little known pioneer theorists on gas turbine technology. One of his ideas was a multi-stage unducted fan, with the propulsive vanes directly attached to the turbine wheels, nevertheless, his ideas, being so advanced couldn't have been built with the technology of the day.
 
Griffith is one of the little known pioneer theorists on gas turbine technology. One of his ideas was a multi-stage unducted fan, with the propulsive vanes directly attached to the turbine wheels, nevertheless, his ideas, being so advanced couldn't have been built with the technology of the day.

The Idea of Gas turbines go back to before WW I. At least for stationary powerplants and/or ship propulsion. The problem was, as you say " couldn't have been built with the technology of the day". These prototypes were failures. In-efficient compressor sections, combustion chamber design and the power turbine all needed much more work. Getting an early gas turbine to actually "run" ( keep itself going without the "starter" being engaged) was just the first step. Getting it to produce surplus power to actually do something with was the next and getting it to last for a number of hours was another. Getting the whole thing light enough to put in an airplane is another problem.
 
You might be surprised to learn that the first axial flow gas turbine that successfully ran - in Germany, naturally, was designed as a turboprop. This was the work of Herbert Wagner; he worked with Junkers to build a gas turbine powerplant for the EF-61 high altitude research aircraft.

Brown Boveri were building working axial compressor gas turbines in 1932. They certainly werent aviation engines but they had all the same principles. They built a gas turbine locomotive in 1937 which ran until 1958 but it didnt use an axial compressor as far as I am aware.
 
If you have a working turbo-prop you have a working jet engine. The turbo prop is NOT a stepping stone to the the JET. It is a JET with EXTRA bits bolted on to give greater propulsive efficiency at low/medium speeds.

True.

But the Metrovicks F1 came first and was dropped so that the F2 could be developed. For many WW2 applications the turbo prop would have been as good as a jet - if not better. Due to better speed matching to the airframes and better fuel efficiency.
 
It is true that a turbo prop would be a better match for the existing airframes how ever it is also true that the turbo prop is a more difficult engine to build (develop) than the pure jet. You have a more complicated turbine section and the reduction gear box to deal with.
 
The Hungarian Jendrasik had the first gas turbine for aviation running in 1937. Hermann Holzworth had BBC (Brown Boverei and Cie of Mannheim Germany, ie the German not Swiss division) had a constant volume gas turbine in service for many years from 1922 powering generators for the German railways and others around 1940 for use with blast furnace gas. His first 150kW unit ran in 1910. These constant volume turbines use a chamber that is filled with compressed air from via a hydraulic poppet valve, ignited by a spark or injection of a flame and then exhausted through another poppet valve to a turbine, a pair of these provides smooth power while water cooling kept the materials cheap and recovered some steam power. These engines almost came into use for aircraft. Heinkel was building one that was called the HeS 040, it was arranged like a onventional turbojet but with valves to the combusion chamber that open close for induction and exhaust. It was abandoned when progress on HeS 030 was good. There was a big business for BBC (german division) for its Velox turbo-supercharged boilers which could produce rapidly available steam (10 minutes to full power) from gas derived from blast furnaces or gasified brown coal, no less than 75 ordered or in service by 1940.

I suspect that the extra hassle of more turbine stages, reducer gearboxes, complicated control systems make the turbo-prop a non starter for combat aircraft. Niches remain such as STOL but for military struggling to obtain the upper hand they may as well use their highly developed piston engines on transports and maritime patrol aircraft while the combat aircraft use turbojets.

Even in the range area the turbo-prop offers little advantage in long flights. Unlike piston engined aircraft a turbojet does not loose efficiency at high altitude, it only looses power. By flying higher parasitic drag is reduced to the point that only induced drag is an issue and so jets do quite well in the range as well.
 
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Hi Siegfried

I suspect that the extra hassle of more turbine stages, reducer gearboxes, complicated control systems make the turbo-prop a non starter for combat aircraft. Niches remain such as STOL but for military struggling to obtain the upper hand they may as well use their highly developed piston engines on transports and maritime patrol aircraft while the combat aircraft use turbojets.

I take it by this you mean during WW2? If you do, no working turboprop had been fitted to an aircraft; the first aircraft to be powered by a turboprop was a Gloster Meteor EE227 especially modified with a reduction gearbox fitted to its engine; this was the RR Trent RB.50 torboprop fitted with a Rotol constant speed propeller. it first flew as a turboprop in September 1945.

If you don't, you need to look at a military aircraft directory. Turbo-props have powered all manner of combat aircraft; the Westland Wyvern torpedo bomber, the Fairey Gannet maritime patrol aircraft to name a couple. These days no one but poorer military nations operate piston engined transport and maritime patrol aircraft. (The RAAF have since retired the Caribou, but then you would know that being in Australia) The only MP aircraft in service today that is not a turboprop is the Nimrod, which is powered by four RR Conway low bypass turbofans. By the way, with the exception of designs over forty years old, no combat aircraft are powered by turbojets today; all turbofans.

Even in the range area the turbo-prop offers little advantage in long flights.

Not strictly true! I suspect the designers and operators of the P-3 Orion might disagree. If you are comparing this to current gas turbine technology as applied to the likes of RR Trent 1000 and GENx engines, then, yes. Turboprop powered aircraft demonstrate remarkable efficiency and range for their size and load carrying capability. Do you know much about the ATR-72 regional airliner? This has remarkably low fuel consumption and a long range carrying nearly 20 more passengers than the Dash Eight Q300 on roughly the same powerplant.

Turboprops are no more complex in design that modern pure jet engines. How much do you know about the PWC PT-6 turboprop? It and many other turbo props still use centrifugal compressors due to their simplicity and robustness. Modern high bypass turbofans demonstrate a degree of complexity that exceeds the average humble turboprop. Sure, there is a reduction gearbox, but piston engined aircraft were also fitted with such things, since before WW1. This was not new technology with the introduction of gas turbine driven propellers. This suggestion that turboprops have more turbine stages than a pure jet is rubbish. in the PW100 series turboprop there are three turbine stages. In the RR Trent 900 fitted to the A380 there are seven turbine stages. I could go on about the inaccuracy of your post, but I won't.

Might I suggest we return to the topic of the thread, please?
 
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