WI: Steam turbine development not cancelled

[Siegfried]

@ Wuzak
Thanks for that info.

If the claimed weight could be achieved the engine would be no heavier than a piston engine: eg BMW 801 1022kg for 1729hp.

Putting boiler in the fuselage means that the weight has to be transferred to the wings. It also subject the crew to potential injury. The only reason to put it there is if you intend to stoke the boiler with a shovel (too small really) or have feeding equipment for slurry coal.

What about an nacelle with a anular style condenser similar to the radiator of a Jumo 211 as used on a Ju 88, followed by the turbine followed by a space for the undercarriage with the boiler in the rear of the engine nacelle. A 12.5 mm thick 1.1m diameter Armour disk weighing 150kg will protect the boiler and rear of the engine.

The boiler is a small part of this engine. The condenser is the vulnerable part. I suspect a further condenser will be needed outboard of the wings.

 

[Siegfried]

In the summer of 1972, I spent 3 months in Idaho Falls, Idaho on a summer intern job at the AEC's LOFT project. (Loss Of Fluid Test)

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An atomic aircraft is quite plausible, if you increase the size to about 500-1000 ft wing span range the gauge of the wing skins becomes so thick it forms its own nuclear shielding. Aluminum is a good shield as it does not contaminate. You would need an outsize runway.

Most of the atomic jet powered projects seem to have a canard configuration: the reactor over a wing while the crew sits in a cabin about 200ft or so ahead of the reactor.

 

[davebender]

I think your numbers are off. Especially for the engine.

price data for 1941 for some German aircraft types, via Olaf Groehlers GdLK, 1910-1980:
Without engine / with engine, in Reichsmarks (RM)
Bf 109E : 58 000 / 85 970. The DB601 engine costs 27,970 RM.
Bf 110C : 155 800 / 210 140. The DB601 engines cost 27,170 RM each.

Bear in mind these are early war production costs (i.e. Me-109E was replaced by Me-109F during 1941). Production cost per item drops significantly as production numbers increase. Something that still holds true today when discussing F-35 production costs. By 1942 Me-109s, Me-110s and DB601 / DB605 engines were significantly less expensive.

The Fw-190 followed a similiar production cost curve but mass production didn't start until 1942. Consequently the Me-109 and DB605 engine were significantly less expensive then the Fw-190A and BMW801 engine right to the end of the war.

Ju-88. An even better example as so much cost data is available on the internet.
http://www.econ.yale.edu/growth_pdf/cdp905.pdf
1939 to 1940. Ju-88 airframe production cost drops from 523,385 RM to 210,648 RM.
.....Ju-88 Production began during 1939. 69 aircraft were produced that year. So the 523,385 RM represents the cost for a hand built prototype. 210,648 RM represents the cost after 69 aircraft have been built on the assembly line.

Ju-88 airframe production cost drops to 131,145 by 1943. Labor costs drop by almost two thirds as production methods became more efficient. There were also significant reductions in material costs. On the other hand, tooling costs increase as skilled labor was replaced by unskilled labor.

That's probably more production cost information then you ever wanted to know.

 

[wuzak]

According to Daimler-Benz DB 603 - Wikipedia, the free encyclopedia the DB603 had a max continuous output of 1500hp. So two of these (or a DB613) would be equivalent to the 3000hp Jumo steam turbine. The dry weight of two DB603s would be 1840kg, not including radiators and oil coolers. If the Jumo had the 0.7kg/hp requirement it would weigh approximately 2100kg for the complete installation.

 

[wuzak]

A drawing of the Junkers steam turbine with reduction gear

A diagram of the Junkers steam turbine for a wing installation. Note that the boiler is in the nacelle behind the turbine.

A size comparison between the 4000hp steam turbine developed by Professor Lösel and Dipl-Ing Pauker and the Jumo 213.

Images from Dieter Herwig and Heinz Rode, Luftwaffe Secret Projects: Ground Attack Special Purpose Aircraft

 

[wuzak]

They key is also where are the radiators/condensors going on this aircraft? Will evaporative skin cooling be used?

I doubt evaporative skin cooling would be used.

Seems I was wrong. In the picture above the shaded section of the wing is labelled "oberflächenkühler", which translates as "surface cooler".

 

[Siegfried]

Here are some calculations on the condenser:
The engine at 2000kW and with a sfc of 190grams/hp/hr which is 260 grams/kW/hr. Assuming a diesel like fuel we have 11kW.Hr of energy per kg.

This means that for each 1kW.Hr generated we are burning 260 grams worth of fuel with 2.85 kW.Hr worth of energy and needed to dispose of 1.85kW as waste heat.

About 80%-85% of this has to come out of the condenser, the rest is lost in the boiler exhaust.

Therefore for each kW of power generated we need to dump 1.6 kW out through the condensers.

For each 2000kW stream engine that means 3200kW of waste heat has to be disposed of through the condensers.

The Me 264 V3 had 127 sqm of wing area, hence 64 sq m per wing and per engine.
Assuming that 50% of the area could be exploited we need to transfer out
100kW per sq m. However it looks as if half the condensation was to happen
in the radiator type flow through condenser so this is down to 50kW/sq m.

How would the condenser be made?

I imagine 10mm thick plate with 8mm diameter holes at 9mm centers to produce tube with 1mm thick walls (adjacent tubes sharing a 1mm wall). The side facing the airflow is filled in and smooth. The side facing the wing is corrugated to keep wight down and assure line contact for mininal heat transfer into the main wing. Every 10th tube is solid and can be drilled to rivet or countersunk screw the condenser to the wing surface.
This assembly should come out at 11kg/sq m which works out at 380kg per engine per wing.

The tube like structure at the back ensures line contact and minimizes heat transfer into the wing. Nevertheless a lagging material is provided to stop the wing getting hot. The condenser might even need to be mounted on posts or bolted down with insulating washers and sleeves. Air circulation through the wing keeps its cool.

One problem with the early He 177's that used evaporation steam cooling was heat distortion of the airfoils aerodynamic properties and this will need to be considered.

I imagine two seperate wing surface condensers per wing with the normal flow type condensers will provide 3 opportunities to cut off leaks caused by battle damage and thereby still maintain some degree of power.

I tend to think that just building a large condenser may be the best option if it can be built to recover thrust through the Meredith effect.

 

[swampyankee]

100 Celsius is an incredibly high outlet temperature for a steam turbine; marine and utility turbines will have outlet temperatures more like 20 or 30 Celsius (a friend, who was MPA on a USN steam turbine frigate, reported that ships had significant power loss due to the warm waters in the Persian Gulf and Red Sea in the summer of 1980).

I'd also tend to take reports of sfcs equivalent to 0.42 with a very large grain of salt.

 

[KiwiBiggles]

Thanks to SwampYankee for resurrecting this thread.

I feel the Bristol Tramp should be mentioned here, developed in the early 1920s but never flown. It was a development of Bristol's existing Pullman four-engine triplane, with the four Liberty engines replaced by a two 1500 hp steam engines in the fuselage, driving two propellers on the wings through a gearbox and driveshafts.

As anticipated in some of the posts above, the major obstacle encountered was designing a reliable closed-circuit boiler and condenser. Although there were also difficulties trying to transmit 3000 hp through an airframe designed for at best half that power.

 

[Shortround6]

 

[swampyankee]

That temperature seems very low for a 100 atm system. Unless the boilers werent using superheaters which would seem to me to be very dangerous any water carry over is going to be fatal in the HP stage of the turbine.

To add to what Wuzak said: 550 Celsius is pretty close to the upper limit for utility turbines today. Of course, 100 atm is quite a bit lower than the working pressure of a modern steam plant, which will frequently exceed 200 atm. The Philadelphia Electric Eddystone plant was built built for 5,000 psia (about 345 atm) and, iirc, 650 C.

The German aircraft steam plant probably used a forced-circulation, once-through steam generator. For one thing, a conventional boiler relies on gravity, so it's probably not the best choice for an aircraft, second, FCOT steam generators have lower thermal mass, so they can respond more quickly.

I remain, however, very skeptical of the reported sfc.