Junkers engine project - 3000hp/800kg

[Wuzak]

In 1940 Junkers started on an engine for use in large multi engined aircraft, with a target power of 3000hp. The engine would have been small and compact, and at 800kg (1760lb) about the same weight as a two stage Merlin.

It was expected to have a life of 5000-6000 operating hours, or approximately 10 times the life of contemporary engines!

The engine was to be a steam turbine.

The data on a drawing shown in Luftwaffe Secret Projects, Ground Attack & Special Purpose Aircraft, by Dieter Herwig and Heinz Rodem is:


Power 2238kW 3000hp
Turbine Speed 8000rpm
Propellor speed 950rpm
Turbine Pressure 100atm 1470psi
Temperature 550°C 1022°F
Exhaust pressure 0.15atm 2.2psi
Weight 800kg 1764lb


It is not clear whether or not the weight was inclusive of the boiler or not.

One potential aircraft for the Junkers steam turbine was the Messerschmitt Me 321 transport glider.

A similar project was also undertaken at that time by Professor Lösel and Dipl Ing Paucker of the Technische Hochschule. Theirs was to be 4000hp, slightly more than half the length of a Jumo 213, and just above 2/3 of the Jumo's height.

All development work on steam turbines was cancelled by the RLM in mid 1942.

A further project involving steam turbines was instigated in late 1944 for the Me264 project. Professor Lösel's Osermaschinen company was commisioned to design a steam turbine with a power output of 6000hp.

This I have already mentioned in the discussion about the Me264: http://www.tgplanes.com/Public/snitz/topic.asp?TOPIC_ID=1368

In this instance the turbine was to operate at 6000rpm, and the target specific fuel consumption was 190g/hp/hr (0.42lb/hp/hr) which was more efficient than most, if not all, contemporary piston engines.

Of course by the time this project got underway it really was too late. Before the engine could be completed the Me264 project was terminated after the loss of the prototype in Allied bombing raids.

The clear advantage of steam turbines is the ability to use any fuel that burns - low octane fuels, solid fuels, liquid fuels, gaseous fuels. It also does not require compressing of the air in order to achieve complete combustion. The clear disadvantage is the boiler. It is a high pressure vessel that is vulnerable to damage, and with it the whole system is vulnerable. The anciliaries, such as pumps, are also a potential weak link.

One wonders if the steam turbine projects had not been aborted in 1942 that there would have been a flight capable steam turbine by 1944.

[Red Admiral]

I don't doubt the small size and weight of the turbine, the single stage axial on the W.2/700 (about 1ft diameter and 3-4" long) put out around 4000hp to drive the compressor. However, the steam turbine runs at far higher pressure ratios and multiple stages would be needed to expand the steam, probably 10-15 at least which adds significantly to the length. I really doubt that the weight includes the boilers.

Really you're far better off in building a really big turboprop like the NK-12 which is very conventional, uses WWII period technology but is just very large and so puts out a great amount of power. Large is a relative term, similar diameter but greater length to something the Griffon.

Some more bits and pieces here;

http://wesworld.jk-clan.de/thread.php?threadid=4879&sid=a8f31a0b75848947ebd1f6f2fbd9f995

[Wuzak]

I think that a turbine such as the NK-12 was beyond the Germans in the 1940-45 period. It was based on knowledge gained in WW2, but I think probably had a few refinements.

The steam turbine probably runs at higher pressure than the gas turbine, but it also runs at a significantly lower temperature - of the order of 400-500°C (752-932°F). High temperatures and the lack of suitable alloys was one problem the Germans had with their gas turbine technology.

Steam turbines were a well known technology. They had been used in power generation facilities for many years. The control mechanism required were well understood. The first steam turbine powered ship was built in 1894.

Most importantly, from the German perspective, was that steam turbines were vastly more efficient than internal combustion engines at the time - especially in the case of gas turbines. The role envisaged for steam turbine powered aircraft was long range maritime patrol and, in the case of the Me264, a platform which could attack America.

I doubt that a single engined steam turbine aircraft was ever envisaged. With multi-engined aircraft the turbines could be all fed by a centrally located boiler. This is most likely the lightest solution, and the most easily protected.

The other advantage for a steam turbine is it can use fuels that even gas turbines can't.

I still think that the whole concept of a steam powered aircraft is fascinating.

[Ricky]

Steam-power was of course the only real choice before decent internal-combustion engines were available...

http://www.sciencemuseum.org.uk/images/I004/10216034.aspx?keywords=aeroplane

Properly made they had power/weight ratios similar to modern internal combustion engines.

[Groggy]

quote:Originally posted by Ricky

Steam-power was of course the only real choice before decent internal-combustion engines were available...

http://www.sciencemuseum.org.uk/images/I004/10216034.aspx?keywords=aeroplane

Properly made they had power/weight ratios similar to modern internal combustion engines.


Hi Folks,

Do not forget the post war Anglo-American Nuclear Powered Flying Boat for the U.S.Navy.
That must have used steam turbines!

[Red Admiral]

quote:Originally posted by Groggy


Hi Folks,

Do not forget the post war Anglo-American Nuclear Powered Flying Boat for the U.S.Navy.
That must have used steam turbines!



Not sure on that. I've only seen nuclear powered proposals where the reactor serves a massive heat exhanger to heat up the incoming air in exactly the same way as a gast turbine.

[Wuzak]

quote:Originally posted by Groggy

quote:Originally posted by Ricky

Steam-power was of course the only real choice before decent internal-combustion engines were available...

http://www.sciencemuseum.org.uk/images/I004/10216034.aspx?keywords=aeroplane

Properly made they had power/weight ratios similar to modern internal combustion engines.


Hi Folks,

Do not forget the post war Anglo-American Nuclear Powered Flying Boat for the U.S.Navy.
That must have used steam turbines!



There was a B-36 converted to use a nuclear reator for propulsion. It didn't use steam turbines, but directly heated air and then expanded it through a nozzle to create thrust.

The aircraft flew, but I don't believe that it ever used the reactor for propulsion.

[Trexx]

quote:Originally posted by Wuzak

quote:Originally posted by Groggy

quote:Originally posted by Ricky

Steam-power was of course the only real choice before decent internal-combustion engines were available...

http://www.sciencemuseum.org.uk/images/I004/10216034.aspx?keywords=aeroplane

Properly made they had power/weight ratios similar to modern internal combustion engines.


Hi Folks,

Do not forget the post war Anglo-American Nuclear Powered Flying Boat for the U.S.Navy.
That must have used steam turbines!



There was a B-36 converted to use a nuclear reator for propulsion. It didn't use steam turbines, but directly heated air and then expanded it through a nozzle to create thrust.

The aircraft flew, but I don't believe that it ever used the reactor for propulsion.


Interesting-interesting-interesting!
I think you're mistaken about the B-36 with a reactor on board. I've read quite a bit about the A-Plane project in the U.S.

One B-36 was indeed modified to carry an operational reactor. It was a proof of concept of basic order. To figure out if an airplane could actually carry an operational nuclear reactor was the first order of business. Then if it could, the crew on board would need to be protected from toxic radiation... with all the necessary shielding. This was all accomplished with this airplane. The reactor was not part of any propuslion system at all.

Two schools of thought were explored for nuclear powerplants in airplanes.

credit for quoted item below:
http://www.megazone.org/ANP/atomair.shtml

"The reactor could be one of two types. The first and most widely used was the "slow" model, in which the neutrons are slowed by a bulky moderating substance, such as graphite or water to a low enough speed for a self-sustaining chain reaction to take place. This type of reactor was relatively easy to design and operate. However the shielding was usually made of a specially prepared concrete 5 to 10 feet thick and weighing about 200 tons, too much even for the heavy-lifting capability of the B-36H. The "fast" model ran on higher speed neutrons, the same kind that activate an atomic bomb. Such a reactor could be made the size of a 3 to 4 foot sphere and weigh approximately 50 tons. But the heat generated would be very high, at least 2,000 degrees Fahrenheit-four times as hot as the slow reactor. Unless the engineers made materials that could withstand such heat, the reactor would simply melt itself.

GE's solution for the X-6 was to design a single, large, air-cooled reactor that had a core of 143 pounds of uranium dioxide fuel elements riddled with air passages and sandwiched between rings of stainless steel. Four J-53 turbojet engines were manifolded to the front and rear ends of the reactor; air from the compressor sections of the jets passed directly through the core and then out the exhaust nozzles. The all-up weight of the power plant came to about 128,000 pounds, 60,000 pounds of which was shielding.

The GE design employed the so-called direct or open system. Air was ducted straight through the reactor, emerging super hot to replace the heat formerly generated by the burning of fossil fuel (such as kerosene) in the jet's combustion chamber. The reactor-jet power plant was to be mounted inside the X-6 in its aft bomb bay with the four J-53s underneath the aft fuselage in an exposed group. The total amount of shielding was divided. A large tank of water surrounded the reactor itself (water acting not only as a shield but also as a reaction moderator in the core). A circular, lead-and-steel Gamma-ray shield, 80 inches in diameter and 4 inches thick, was immediately behind the forward Crew compartment."

More on this fascinating subject:

http://www.everything2.com/index.pl?node_id=1498863

http://www.aboutnuclear.org/view.cgi?fC=Space,History

What's REALLY astounding is the proposal in the U.S. to have an "atomic corridor" for cross country flights to limit the fall-out radiation from the atomic exhaust. Amazing.


http://img.villagephotos.com/p/2007-10/1283790/img49.gif

http://img.villagephotos.com/p/2007-10/1283790/img50copy.gif

I swerved into these excerpts months ago. Note the design feature of pilots compartment being as far away from the reactor portion of the airplane as possible! Hot-tottie...Whoa! [:0]

[Red Admiral]

Heres another atomic powered aeroplane. Please note the size (given by the 24 fighters it carries) Weight was around 2million pounds. There are also a fair few nuclear-powered Saro Princess designs.

http://i25.photobucket.com/albums/c84/AviationImages/lockheedcarrier.jpg

[Wuzak]

quote:Originally posted by Red Admiral

Some more bits and pieces here;

http://wesworld.jk-clan.de/thread.php?threadid=4879&sid=a8f31a0b75848947ebd1f6f2fbd9f995


Just been rereading the forum you posted RA.

The problem I see with replacing the boiler with a chemical steam creation method (HTP?) is that you lose one of the reasons that steam turbines are efficient - recirculation of the water/steam through the system. The condensor part can be achieved by using the hot steam to heat the incoming air for combustion, heating the cabin, etc. (This can also be done in gas turbines, I believe theoretically raising their efficiency, but not done as far as I am aware. A couple of German WW2 turboprop projects tried to use this to gain efficiency, but didn't reach maturity before war's end.)

I take the point about needing some sort of supercharging, but again this doesn't need to be to the same degree as for piston engines - merely maintining sea level pressure in the incoming air should be more than enough. And to some degree the system will be self compensating - at lower pressures water evaporates at lower temperatures.

[Wuzak]

I have been thinking about the need for a supercharger in a steam turbine aero powerplant.

The steam turbine cycle is closed loop, effectively, so there is no effect on its performance due to altitude. However, for the steam to be at the proper temperatures and pressures there needs to be the same amount of heat put into the system at all altitudes to maintain power.

One way to achieve this is to maintain sea level atmospheric pressure in the combustion chamber via a supercharging system. The other way is to increase the volumetirc flow rate of the air - without compressing it. In both instances the goal is to maintain the mass flow rate of air and thus the mass flow rate of fuel.

The equipment that was to be used in the ME264 (from Messerschmitt Me 264 Amerika Bomber - The Luftwaffe's Lost Transatlantic Bomber) consisted of four capiliary tube boilers, each one metre in diameter in 1.2m high; a boiler feed waer pump and auxiliary turbine; a main turbine, 0.6m in diameter and 1.82m in length; a combustion air draught fan, condeser, controls and auxiliaries.

The suggestion from that is that there was no supercharging of the combustion air, or any attempt to maintain sea level pressure, but the combustion air fan was to maintain the mass flow rate of air to the boiler.

The size of the boiler is given there, and is quite compact. In Luftwaffe Secret Projects, Ground Attack & Special Purpose Aircraft a proposed installation diagram is shown having the turbine out in front of the wing leading edge, like a normal wing mounted engine was at the time, with the boiler behind it buried in the wing.

[Wuzak]

Reading further I have discovered that the turbione units proposed for the Me 264 had a requirement for weight to power of 0.7kg/hp.

At nominally 6000hp that equates to 4200kg! A not insignificant amount.

So, if we compare the power to weight ratio with an advanced German pistion engine:


Steam Turbine Jumo 213
power 6000 hp 1725 hp
weight 4200 kg 940 kg
9240 lbs 2068 lbs

w/p 0.7 kg/hp 0.545 kg/hp
1.54 lb/hp 1.199 lb/hp
p/w 1.429 hp/kg 1.835 hp/kg
0.649 hp/lb 0.834 hp/lb


The Jumo 213 is calculated without radiators, etc.

The top German radial was the BMW 801. Its numbers are:


BMW 801
1600 hp
1065 kg
2343 lbs

0.666 kg/hp
1.464 lb/hp
1.502 hp/kg
0.683 hp/lb


Later versions of the 801 had more power, so their power to weight ratio was much improved. The allies were able to produce engines with higher power to weight ratios than the Germans, such as the R-2800 and the Merlin.

We must be careful comparing these, for the hp numbers are in different conditions. For the above mentioned the hp rating is a max hp at a certain altitude. Some may be able to produce more power under WER conditions - but only for a short time. The 6000hp is the steam turbine's maximum continuous rating. In WER conditions it is said that the steam turbine can go to 100% overload - not sure what that means, but I am guessing it means that for short periods (much longer than WER on piston engines though) the steam plant is able to operate at 12000hp!

[ChrisMcD]

quote:Originally posted by Red Admiral

Heres another atomic powered aeroplane.


How about the Tu 95LAL
http://www.aviation-history.com/articles/nuke-bombers.htm
You can usually rely on the Russkies to have a go at something like this - and I do like the M60; sort of giant F 104

[Nekard]

Steam turbines where a serious proposition by several +60 years ago. Take a look in " Gas Turbines and Jet Propulsion for Aircraft" by Geoffrey Smith. One exampel is the flying boat from Great Lakes Aircraft Corp (US) with steam concept. Frenchman Mr Leduc had in 1942 un interesting system with heat recovery from a reheat to drive the compressor via a steamturbine ( flash boiler ?). Mr Sikorsky also used heatrecovery in his patent. Thermal efficincy in any kind of engine gives us a potential for heat recovery still today. Even a heatpump could be of interest to boost steam if not too complex.