fastmongrel
1st Sergeant
If more people drank beer and had a good time then there would be fewer wars.
Amateurs study aircraft design. Professionals study oil production.
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If more people drank beer and had a good time then there would be fewer wars.
Shortround6
Major General
Amateurs study Beer Brewing. Professionals study hops production. 
bobbysocks
Chief Master Sergeant
that's hysterical
- Thread starter
- #44
davebender
1st Lieutenant
Italy and Britain had a serious "Great Game" going in East Africa during the 1930s. German alliance with Italy destroyed their détente with Britain.
Why shouldn't 1930s Germany allow Italy to go their own way? German interests were in central Europe, not the Red Sea. And 1930s Germany badly needed British diplomatic support as a counterweight to Marxist France.
Why shouldn't 1930s Germany allow Italy to go their own way? German interests were in central Europe, not the Red Sea. And 1930s Germany badly needed British diplomatic support as a counterweight to Marxist France.
Below are links as to how the Germans synthesised iso-octane from iso-butanol during WW2 including how important stuff such as how to make the catalysts. The key is iso-butylene which can be easily made into iso-octane. I believe it was some BP chemists developed a process called alkylation in the early 30s that helped give 100/130 and in the US a regenerative catalytic cracking catalyst (that gave 100/100 octane). Without these the performance of allied engines, if unaltered would have been rather poor unless a rapid conversion to 87 octane plus water injection was developed.
Synthesis of alcohols is very efficient and straightforward and one wonder whether a blend of methanol and iso-butanol might have been quite a good fuel.
The iso-butylene was also needed for synthesis of n-buna and s-buna rubber and this limited German C3 fuel production. After the Hydrogenation (as opposed to synthesis plants) were up and running a great deal of byproduct Propane and Butane was available for use in LPG vehicles. These were supposed to be used for commercial and private vehicles such as transport trucks etc. Building the requisite 600,000 vessels proved to much for German industry and only a few thousand were built.
Modern techniques have progressed greatly. Most seem to start with production of methanol as an intermediate feed stock and then create gasoline (Mobils MTG methanol to gasoline) or Jet/Diesel/gasoline (Lurgi's megasyn) from that. These processes are up to 85% efficient if natural gas is the feed stock and 60% if coal. Fischer-Tropsh has also improved. The Germans had also worked out how to make iso-butylene from methanol rather than butanol and even to make iso-butylene from CO+H2 directly.
A few more years and the coal to liquids might have easily doubled German production for the same effort.
Technical Report 248-45 - Section V Isobutanol Synthesis
1. Isobutanol Synthesis.
The following information on the synthesis of isobutanol was obtained from Dr. Goggel of the I.G. Farbenindustrie at the Ludwigshafen plant on 28 May 1943. This synthesis is in essence an extension of the high pressure methanol synthesis which utilizes carbon monoxide and hydrogen. The isobutanol synthesis uses the same raw materials, practically the same catalyst, and pressures of the same magnitude (about 240 atmospheres). The catalyst used for the higher alcohols in zinc and chromium oxides with the addition of one percent of potassium hydroxide. The temperature used is about 430° Centigrade.
The main difference compared to the methanol synthesis is the lower output per catalyst volume, since the main product (CH3OH) is recycled to extinction. Based on a once-through operation, the product made in greatest quantity in this synthesis is methanol; about five to six parts of methanol are obtained for every part of isobutanol. In addition to this, there are a great many other alcohols and ketones produced. The total weight of these products equals the weight of isobutanol in the product.
On a water free basis the total product contains approximately:
Isobutanol 14%
Methanol 63%
High alcohols and Ketones 15%
Hydrocarbons 5%
Technical Report 145-45 - The Manufacture of Aviation Gasoline In Germany Polymerization
Proceedings of Technical Oil Mission Meeting - Butane Dehydrogenation
The first process now for making iso-octane in Germany appears to have been the dehydration of isobutyl alcohol to make isobutylene, polymerization to di-isobutylene, and hydrogenation to iso-octane. The next process started with iso-butane instead of alcohol and prepared iso-butylene by catalytic dehydrogenation. Subsequent steps were the same as in the first process. The third process developed with the advent of alkylation, which in Germany was restricted to the sulfuric acid catalyst system commercially. At this time the iso-butane was needed as one of the components of the alkylation feed stock, so dehydrogenation equipment was adapted to n-butane instead of iso-butane. The effluent butylene containing a stream was combined directly with iso-butane in the alkylation unit, and excess n-butane was recycled back to the dehydrogenation reactors.
Technical Report 248-45 - Table of Contents
An interesting fuel was 'triptane' thought by some to have a lean PN of 162 but to be only a still useful 112.
Technical Report 145-45 - The Manufacture of Aviation Gasoline In Germany Polymerization
Synthesis of alcohols is very efficient and straightforward and one wonder whether a blend of methanol and iso-butanol might have been quite a good fuel.
The iso-butylene was also needed for synthesis of n-buna and s-buna rubber and this limited German C3 fuel production. After the Hydrogenation (as opposed to synthesis plants) were up and running a great deal of byproduct Propane and Butane was available for use in LPG vehicles. These were supposed to be used for commercial and private vehicles such as transport trucks etc. Building the requisite 600,000 vessels proved to much for German industry and only a few thousand were built.
Modern techniques have progressed greatly. Most seem to start with production of methanol as an intermediate feed stock and then create gasoline (Mobils MTG methanol to gasoline) or Jet/Diesel/gasoline (Lurgi's megasyn) from that. These processes are up to 85% efficient if natural gas is the feed stock and 60% if coal. Fischer-Tropsh has also improved. The Germans had also worked out how to make iso-butylene from methanol rather than butanol and even to make iso-butylene from CO+H2 directly.
A few more years and the coal to liquids might have easily doubled German production for the same effort.
Technical Report 248-45 - Section V Isobutanol Synthesis
1. Isobutanol Synthesis.
The following information on the synthesis of isobutanol was obtained from Dr. Goggel of the I.G. Farbenindustrie at the Ludwigshafen plant on 28 May 1943. This synthesis is in essence an extension of the high pressure methanol synthesis which utilizes carbon monoxide and hydrogen. The isobutanol synthesis uses the same raw materials, practically the same catalyst, and pressures of the same magnitude (about 240 atmospheres). The catalyst used for the higher alcohols in zinc and chromium oxides with the addition of one percent of potassium hydroxide. The temperature used is about 430° Centigrade.
The main difference compared to the methanol synthesis is the lower output per catalyst volume, since the main product (CH3OH) is recycled to extinction. Based on a once-through operation, the product made in greatest quantity in this synthesis is methanol; about five to six parts of methanol are obtained for every part of isobutanol. In addition to this, there are a great many other alcohols and ketones produced. The total weight of these products equals the weight of isobutanol in the product.
On a water free basis the total product contains approximately:
Isobutanol 14%
Methanol 63%
High alcohols and Ketones 15%
Hydrocarbons 5%
Technical Report 145-45 - The Manufacture of Aviation Gasoline In Germany Polymerization
Proceedings of Technical Oil Mission Meeting - Butane Dehydrogenation
The first process now for making iso-octane in Germany appears to have been the dehydration of isobutyl alcohol to make isobutylene, polymerization to di-isobutylene, and hydrogenation to iso-octane. The next process started with iso-butane instead of alcohol and prepared iso-butylene by catalytic dehydrogenation. Subsequent steps were the same as in the first process. The third process developed with the advent of alkylation, which in Germany was restricted to the sulfuric acid catalyst system commercially. At this time the iso-butane was needed as one of the components of the alkylation feed stock, so dehydrogenation equipment was adapted to n-butane instead of iso-butane. The effluent butylene containing a stream was combined directly with iso-butane in the alkylation unit, and excess n-butane was recycled back to the dehydrogenation reactors.
Technical Report 248-45 - Table of Contents
An interesting fuel was 'triptane' thought by some to have a lean PN of 162 but to be only a still useful 112.
Technical Report 145-45 - The Manufacture of Aviation Gasoline In Germany Polymerization
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kool kitty89
Senior Master Sergeant
Yes, at least that's what I assumed as well (given the context was 1940/1941 and also relating to BoB and Operation Barbarossa), hence the comments on the Balkins campaign.
Changing the formation of the alliance with Italy in the first place is a broader topic, but certainly interesting point in its own right.
Neat information, but I think the calculations you did for the water-free figures are a bit off.
With water, the figures are:
Isobutanol 12%
Methanol 55%
Water 18-20%
High alcohols and Ketones 10%
Hydrocarbons Balance
Which would mean 3 to 5 percent hydrocarbons in the balance (with water removed that's roughly 3.8-6% hydrocarbons, so the average of 5% you used seems reasonable, however it's the other values that seem skewed)
If we assume 5 percent hydrocarbons from the water-free products, the relative proportions (rounded to the nearest percent) should be:
Isobutanol 15%
Methanol 68%
High alcohols and Ketones 12%
Hydrocarbons 5%
In any case, in the scenario being proposed in regards to general purpose synthetic fuel blends used from this process (rather than proceeding to full synthesis of conventional gasoline or isooctane), a good number of the side products (hydrocarbons, ketones, and other alcohols -especially acetone, methyl-ethyl ketone, ethanol, propanol, and n-butanol) would be quite useful as well.
The statements in that document regarding methanol generated in that process being impure and economically impractical to purify would be referring to production of chemically pure feedstock for technical/high grade industrial use. That impure methanol should be perfectly suitable for commercial fuel (and low grade solvent) use. Direct synthesis of methanol is still more efficient when that's the primary product desired, though, and I'm not sure if methanol behaves any less favorably than pure CO/H2 syn gas (ie if recirculating methanol uses more energy than pure syn gas feedstock), but in any case in a synthetic fuel economy it might make sense to vary recirculation rates (with some impure methanol tapped off to supplement methanol fuel feedstock for fuel blends and possibly pure methanol fuel for ground vehicles).
If such conversion was undertaken pre-war, there'd still be at very least some consideration for flexibility and ability to use foreign fuels (particularly captured fuel supplies during the early-war invasions). I'm not sure exactly hos significant this was, but it's one of the arguments I've seen for the emphasis on gasoline over diesel powered tanks and heavy transports. (along with simplifying logistics with lighter ground vehicles)
Shortround6
Major General
It took NATO quite a number of years during the cold war to switch from gasoline to Diesel. Unfortunately they took a "multi-fuel" detour that added expense and time which makes a comparison somewhat more difficult. Some vehicles were supposed to get "multi-fuel" engines that would run on a variety of fuels with the only adjustment being a knob on the drivers control panel. I am not sure that Germany could afford a dual fuel (or more ) distribution/supply system for combat or military vehicles/aircraft. Using some of these alternative fuels for different "customers" may may more sense. AS in domestic transport systems, Bus, truck, and private cars and such. Leaving the combat arms with Gasoline.
Germany's energy troubles were not helped when they had to supply over a million tons of coal per year to Italy after Italy could not get coal from England anymore and things got worse after the Battle of France when the coal could no longer go by ship from the low country ports/Rhine river and had to go by train through the Swiss alps.
But stretching Germany's fuel supply by 20-40% still leaves it way short of what was needed.
Germany's energy troubles were not helped when they had to supply over a million tons of coal per year to Italy after Italy could not get coal from England anymore and things got worse after the Battle of France when the coal could no longer go by ship from the low country ports/Rhine river and had to go by train through the Swiss alps.
But stretching Germany's fuel supply by 20-40% still leaves it way short of what was needed.
kool kitty89
Senior Master Sergeant
That would add to the argument for avoiding diesel fueled ground vehicles. Gas turbines aside, trying to engineer flex-fuel vehicles that can run on diesel/kerosene and gasoline is a total mess. Switching between different octane ratings and fuel blends within a range of alcohols/hydrocarbons/etc (all for spark ignition type engines) is a fair bit more practical than trying to mix diesel and gasoline supply logistics.
That and having the majority of vehicles able to run on the highest quality standard fuel available is a big deal. (ie Avgas can be used as mogas in most cases when needed -though the reverse isn't necessarily true) Like modern logistics with kerosene type jet fuel being more or less universal for diesel and turbine engine use. (Naphtha type fuels like Jet-B aren't acceptable substitutes for diesel though, unlike Jet-A, JP-8, etc)
The case with alcohols is a bit different as well given you can have some of the cheap/common (ie nearly straight methanol) types actually potentially being compatible with high performance (aviation) needs but unattractive due to energy density. (being able to fuel aircraft with ground fuel in a pinch -if limiting range and some performance- while not risking detonation issues is an interesting consideration) Then again, if most fuel in general (ground and air) was predominantly butanol, that would be a bit more like 87 octane B4 avgas being used for nearly everything rather than lower octane rated fuels used for ground vehicles. (or even a bit better than B4)
Shortround6
Major General
Possibly, it depends on how soon you set things up. Trying to change supplies or supply chains after going to war can bring big headaches. In the US, most of the Diesel powered tanks went to the Marine Corp. Marines/Navy already had Diesel fuel for landing craft and ship generators. And Marine tanks weren't going on multi week advances of hundreds of miles. Russians used Diesel tanks and gas powered trucks. British used some diesel tanks and some gas powered and some diesel trucks and some gas powered. I am sure there mix ups and temporary shortages but so far there don't seem to be any glaring mistakes (battle of XXX was lost because of shortage of one fuel or the other).
that is great from a supply/distribution stand point but lousy from a refining supply stand point. Depending on fuel stock ( type/source of crude oil) more gallons of lower grade gasoline can be made from each barrel of oil than higher grades. In the US army in WW II, the vast majority of trucks and light vehicles could run on 70 octane fuel. The Sherman tanks needed 80 octane. IN WW II 80 octane may have been an "aircraft" grade fuel but it was trainer/light transport fuel.
There are a large number of differences between "motor" fuel and aircraft fuel even at the 80 octane level. 80 octane motor fuel was allowed 1 part sulfur to 400 parts gasoline while aviation fuel was allowed only 1 part sulfur to 2000 parts gasoline and was often much lower. There were different allowable vapor pressures and other differences in allowable chemicals. Civilian "motor" gasoline was not the same as Military "motor" gasoline because the civilian gasoline didn't have the staility requirement of the military motor fuel and tended to deposit out gum in storage. Base stocks that 91/96 octane fuel could be made from were much rarer than base stocks that could provide 87 octane. During WW II the 'plant' that could produce 100/130 fuel cost $35.00 per gallon per day to build, mostly because it took about 120lbs of metal in the plant to produce that one gallon per day. Higher performance fuel could run up the cost very quickly. 120/150 fuel was estimated to require a plant of between 300-500lbs of steel per gallon produced per day.
For aircraft use you have a few problems, as in close to to energy content per gallon isn't quite good enough. If you car has 10% less power climbing a hill does it really matter? If you are trying to get a loaded aircraft of the ground 10% less power could mean hitting the trees or not hitting the trees. Modern fuel systems in cars can compensate for a rather wide range of power and air/fuel mixtures and they can do it automatically with engine sensors and an on-board computer. WW II Carburetors aren't going to be quite so forgiving. Neither will mechanical fuel injection, While either can be set up to run a variety of fuels they need some adjustment or replacement parts to do it effectively. Alcohol (even butanol) has a problem vaporizing properly in cold temperatures making starting and warming up hard ( one of the reasons for even summer and winter gasoline and those of us old enough to remember manual chokes.) Butanol maybe much better than the other alcohols but even in Brazil (hardly a cold country) some ethanol powered cars came with "starter" fuel tanks for gasoline.
Some av-gas specs list not only a max Reid vapor pressure but a minimum Reid vapor pressure. In 1950 US military AV gas had a minimum of 5.5 lb/sq/in for all grades.
kool kitty89
Senior Master Sergeant
Indeed. Most of the hypothetical fuel alternatives I was posing were in the context of setting up a new infrastructure pre-war and working towards making the entire German economy self-sufficient in terms of fuel production. (one structured around the most efficient liquid engine fuels able to be synthesized rather than focusing on trying to synthesize fuel closest to the existing gasoline market)
Yes, I was more speaking of potential rare cases where substituting fuel in emergencies would be more feasible than with conventional gasoline. (particularly in the case of methanol -combustion properties are pretty reasonable, but energy density is low -and injectors/carburetors tuned to denser energy fuels might provide insufficient flow rate; manual adjustment of the mixture would address this to some extent, but running full-rich might not be enough to compensate to run properly at full throttle)
I'd actually expect butanol to be more problematic than ethanol in this respect, possibly requiring diesel style fuel warmers or (as you say) a dedicated starter tank unless suitable high volatility blends were practical. (using too much benzene, toluene, and other less-volatile octane boosters have similar problems -in terms of pure hydrocarbons, most of the high octane ones are MORE easily vaporized, at least short of very large, extremely highly branched molecules)
I'd expect methanol to be a fairly useful high-volatility starter fuel, though. And using that as the primary civilian (possibly military) ground fuel component should avoid the problems associated with pure ethanol.
Additionally, Brazil doesn't rely on anhydrous ethanol, but allows a small percentage of water to be present, further hampering starting performance. ( Ethanol forms an azeotrope mixture with water of 95.6 percent ethanol by mass (or about 97% alcohol by volume) at normal pressure, hence everclear type grain alcohol being limited to around 190~195 proof at highest concentrations)
Methanol doesn't form an azeotrope with water and thus can be separated simply by distillation. Propanol and butanol isomers and some higher alcohols do form azeotropes but are less polar than ethanol (or methanol) and can have the water 'salted out' (concentrated brine or solid salt are added to dehydrate the alcohol-water mixtures -propanol, butanol, and higher alcohols will not mix with salt water and easily float to a separate layer on top of the denser saltwater solution).
Ethanol has some of the worst combinations of properties for fuel in this respect and that association with water also worsens corrosion issues. (it also absorbs water more readily from the atmosphere than other alcohols -especially the oilier, less polar higher alcohols) Fuel blends avoiding ethanol entirely would probably make more sense with nearly pure methanol used for ground vehicles and blends of high energy density alcohols, ketones, and hydrocarbons for aircraft use. (acetone and butanone -MEK- would probably be a better additive for aviation fuel than methanol for increasing volatility/vapor pressure in as far as relatively high octane, reasonably energy dense fuels that are relatively easy to synthesize)
American ethanol-gasoline blends all use anhydrous ethanol, and blending hydrated ethanol with gasoline would be problematic anyway (possible separation or emulsions forming), though also making preventing water contamination in storage even more important. (less problematic with methanol given its volatility and better ability to form stable water-fuel emulsions in hydrocarbon blends, hence pure methanol being sold as fuel-line antifreeze like HEET)
Politics aside, ethanol isn't all that attractive as a fuel compared to other alcohols (and the variety of potential synthesis methods).
An interesting engine is the Hesselmen engine. This is little more than a direct fuel injected engine able to run or diesel, kerosene, petrol etc with a relatively powerful spark to ignite the mixture. One reason we use gasoline in cars is because its vaporisation properties allow it to be used in a carburettor. If one wants to use kerosene then the kerosene must be pre heated (as in hot bulb engines) or alternatively injected and vaporised by atomisation. Fischer Tropsch tends to produced kerosene (linear chains) and so is excellent for jet fuel but could also run in a hesselman engine.
In late 70's Saab-Valmet also developed a dual-fuel automobile based around their Saab B engine which was able to use kerosene or turpentine alongside with gasoline. The Low compression ratio for 67 octane kerosene was achieved by using pistons from the turbo model to reduce the compression ratio. The engine had an electronic ignition also used in the turbo engine. Switch between gasoline and kerosene was automatic but the driver was able to force gasoline-only mode with a manual switch. Burning kerosene the engine produced 85 hp at 5600 rpm and was available only in Finland with The Saab 99 GL Petro. The Fins had a good amount of turpentine which is produced at a rate of up to 15 gallons per 4000lb cord of wood (from the paper industry). The actual fuel was obtained by gasifying peat (which the Fins had) and put it through Fischer-Tropsch. Hesselmen engines are as efficient as petrol engines when running of diesel but they were clearly setting up the engine for a low grade fuel.
Of course you have now built a multifuel engine which is less efficient than those optimised for high grade petrol which is somewhat embarrassing if you do happen to have good fuel most of the time.
I know the Germans experimented with these Hesselman engines and they were widely used in Sweddish trucks in the 20s and 30s. Surprisingly the Germans were often short of relatively easy to synthesise diesel since so much effort had been put into making high octane aviation gasoline they had been forced to neglect diesel production. The solution was simply to mix gasoline with lubricating oil and use that as 'diesel fuel' substitute while backing of the throttle a bit to keep cylinder temperatures down.
If you were forced to use the cruder less refine Fischer-Tropsch in that era the solution would be to use a variety of engines: diesel, gasoline but mainly Hesselman Kerosene to exploit the various fractions obtained.
I think an aero engine would do well running of 67 octane kerosene. The Low Compression ratio of the Merlin would make it suitable, it would only need a fuel injection system. The Jumo 211 might work as well with fuel injection mods and lower crown piston to drop the CR from about 6:5 to 6.
For example: The engine would run on normal 87 or 100/130 octane for startup, takeoff and climb but then disengage its supercharger to neutral to run unboosted and switch to the low grade kerosene or gasoline during cruise. As soon as power is required the fuel supply could be switched back to high octane gasoline and the supercharger engaged.
Of course such systems make more sense in vehicles and with rapid advances in fuels and the critical quest for performance it would be hard to bet on the technology in the 1930s.
Methanol would also have made a good fuel. It's lean RON is 109.6 and despite its lower calorific value the higher compression ratio and density mean that the efficiency of the engine can be increased such that it's "miles per gallon is" 70% that of gasoline with the engine more powerful to boot.
Consider a hypothetical Fw 190 with a range of 500 miles. In switching from 100/110 fuel to 109.6 ROn methanol one increase the compression ratio of BMW 801 engine to increase efficiency. We would have only 70% of the range (350 miles) however the outer wing guns on the Fw 190 could be deleted and replaced with wing tanks (done on the Fw n190D12/13) and perhaps the 130L tank added in the Fw 190A9/D9 tail for MW50 or fuel used for methanol to restore range.
We end up with a 350 milre range fighter at worst or a 500 mile fighter with slightly reduced armament. The engine looks like that when on methanol that it will outperform the gasoline 801 version running rich and over boosted. power has gone up because rich methanol introduces more kilojoules into the cylinder.
So their are options for direct synthesis of some interesting fuels that would utilise the coal efficiently. Methanol synthesis would be very efficient. Maybe 65%-70%. Synthesis of hydrocarbons less but I think acceptable so long as a variety of engines can consume the fuel such as Hesselman engines and gas turbines.
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This is all very interesting, but how does it help overcome the shortages and then critical shortages of fuels experienced by the Germans during the war?
The first shortage to the Luftwaffe was not to operational units but support units, most importantly Training Command, and was brought about by a complete lack of long term planning and the increased usage by operational units involved in the invasion of the USSSR.
The second and fatal shortage was caused by a combination of loss of territory and being bombed into next week by the western allies, particularly the USAAF. Where some stocks of fuels existed the Germans found it almost impossible to move them over the rail networks ravaged by the bombing of the 'Transport Plan'. The canal and road systems were also attacked and were subject to the attentions of British and American fighter bombers whenever weather allowed.
All these alternative fuels have to be produced in plants that would surely have been targeted by the allied air forces.
There is a 'chicken and egg' problem implicit in the title of the thread. Without fuel you can't operate your aircraft, but without competitive and well designed aircraft you can't protect the sources or distribution of your fuels.
Cheers
Steve
The first shortage to the Luftwaffe was not to operational units but support units, most importantly Training Command, and was brought about by a complete lack of long term planning and the increased usage by operational units involved in the invasion of the USSSR.
The second and fatal shortage was caused by a combination of loss of territory and being bombed into next week by the western allies, particularly the USAAF. Where some stocks of fuels existed the Germans found it almost impossible to move them over the rail networks ravaged by the bombing of the 'Transport Plan'. The canal and road systems were also attacked and were subject to the attentions of British and American fighter bombers whenever weather allowed.
All these alternative fuels have to be produced in plants that would surely have been targeted by the allied air forces.
There is a 'chicken and egg' problem implicit in the title of the thread. Without fuel you can't operate your aircraft, but without competitive and well designed aircraft you can't protect the sources or distribution of your fuels.
Cheers
Steve
wuzak
Captain
Interested to know why you think that a visible flame is desireable?
I would think that having an invisible flame, or nearly so, would be of great benefit to aircraft operating at night. It would mean that the drag producing and performance affecting flame dampers would be less necessary.
As to using methanol and ethanol, aren't these fuels hygroscopic? I remember reading that there were problems with alcohol fuels being researched for airliners because of this property, the effect being worse at high altitudes.
They are and it causes all sorts of problems and not just in the engines where they can have a corrosive effect but also in storage. Alcohol in fuels causes the fuels to decompose much more quickly. It's fine for relatively small amounts of specialised fuels, as in some racing cars, but poses problems when trying to supply and operate an air force (or airline).
Look up fuel phase separation and 'varnished' fuels to see some of the results.
Cheers
Steve
kool kitty89
Senior Master Sergeant
That might be useful for ground vehicles, but with the way Hesselman engines generally work, you'd not only need starter tanks for cold weather conditions, but for ALL starting and fuel switching during both warm-up and cool down.
The increased complexity of operation (and possibly manufacturing and maintenance) might not be worthwhile. Unless perhaps you're suggesting a more limited implementation that uses fuels only in the very near gasoline vaporization range, but not suitable for carburetor use. Still, the added fuel injection system and limitations of low compression ratios makes all that unattractive.
It seems like it'd make more sense to blend medium/low octane kerosene/oils with more volatile fuels to make them serviceable in normal gasoline engines. (that is IF you had an excessive supply of those range of fuel types) The same would apply to high octane fuels that are simply bad at vaporizing (like some heavy alcohols and aromatics) except those would also allow high compression ratios and greater efficiency. Most such fuels (light kerosene, heavy alcohols, and aromatics) are close enough to conventional gasoline needs that they'd be usable in partial blends with more volatile fuels or even used straight with more volatile fuel used only for starting.
Heavier oils and grades of kerosene with higher cetane ratings (usually lower octane as well -given detonation and diesel ignition are very similar) would be better suited used for diesel oil and fuel oil in other applications (and jet fuel). We've already had arguments on increased use of diesel in aircraft or ground vehicles before and while there's some argument for ground vehicles, there's still added complexity for diesel engines over gasoline. (including the large number of simple, small, air cooled volkwagon engines in use)
67 octane seems very high for kerosene in general, though ... figures I've seen for typical kerosene tend to me more in the 20s or low 30s. Usually good cetane numbers but horrible octane.
That seems impractical due to the power loss and fuel efficiency losses. Low cruise power is going to have lots of drawbacks, not to mention further complicating combat ability.
That said, perhaps something conceptually similar to the Hesselman engine would be more useful if optimized specifically for high-octane fuels but able to use a variety of fuel types ranging from low to high volatility. (though in this respect, the examples of Brazil's hydrated ethanol fuel with separate starter fuel tank would be similar, though possibly less extreme) This might not be very far from existing high compression fuel-injected engines having added stater fuel implemented. (possibly not even required in warm regions)
Similar issues apply to some gas turbine engines. Aside from Heinkel's early designs requiring start/warm up on hydrogen (to get liquid fuel up to vaporization temperature), the Jumo 004 required more volatile fuel to be used for start/warmup. (I'm not sure all models required it, but I've seen starting procedures listing use of gasoline for start-up followed by transition to kerosene/J-2/diesel)
Plus there's the potential for cold vs warm weather fuel blends. Adding fractions of super volatile light organic compounds would be practical.
If methanol had been used as a standard fuel pre-war, the designs would already include such capacity in the first place and perhaps be constructed somewhat differently than existing aircraft. That said, even at that 70%, the sheer weight penalty of that added fuel would be of serious concern. Small fractions of methanol might be acceptable in aviation fuel, but on the whole you'd want an energy density at least close to gasoline (consistently higher octane ratings allowing increased efficiency would help make up some remaining difference there too, though).
Blends of mostly butanols, propanols, acetone, MEK, along with some hydrocarbons (including aromatics from coal tar or other sources) would probably be the most attractive for aviation fuel.
Methanol itself also has significant problems with corrosion with some materials, particularly relevant here being aluminum. Plain carbon and stainless steels don't have that problem, so fuel tanks and lines that avoid aluminum would be mostly acceptable. Any engine with significant aluminum content (including carburetor components, cylinder heads and pistons) could have problems with corrosion if significant residue remained in the cylinders. (I don't think it's as much of an issue during operation, but more during stationary periods -parked or in storage) This is one of the concerns that cropped up with MW/50 systems, though the water content in there was also a concern for any rust vulnerable steel components.
Still, aside from very cold conditions, the high vapor pressure of methanol should cause residue to evaporate out of the system quickly. Ethanol is more problematic in this respect, as would water from a MW/50 system. (methanol-water mixtures would also arrest the evaporation of the methanol to some extent, so methanol reactions with aluminum would be prolonged compared to dry methanol)
Blends with some other fuels and corrosion inhibitors can help, but on the whole, those efforts would probably make more sense oriented to ground vehicle design than aircraft. (use in water injection blends would still make sense, though)
The corrosion and hygroscopicity issues are mostly problems with methanol and ethanol, not heavier alcohols, though I already touched on that above.
kool kitty89
Senior Master Sergeant
For safety with ground handling in case of accidental fires. This would probably be more useful for ground vehicle use, though.
Exhaust flares are nearly invisible much of the time with normal gasoline as well, methanol (and some heavier alcohols) might diminish this somewhat further, but the difference would be far less extreme than comparing open-air combustion. (methanol burns cooler and smokelessly in open air without the incandescent carbon orange or smoke of gasoline or oil fires, vaporized and mixed with air, the flames aren't as distinctly different)
Still, that gain might be useful for night fighters. Even with methanol itself not being a great option for aircraft fuel, a blend of other alcohols and ketones would still apply here. You would want to remove aromatics, though. Benzene, toluene, xylene, napthalene, etc all tend to be very luminous flame producers even when lean (in fact it's what made early coal gas burn bright -and later forced the introduction of incandescent mantles with purified coal gas and natural gas).
Indeed, there were a good many bigger problems at hand before the sheer logistical issues of peak production capacity and efficiency would really be the dominant limiting factors.
Aside from that, the one area the hypothetical alternate fuel production plan would have affected the above issues is vulnerability of manufacturing plants. Fischer–Tropsch synthesis plants could be made relatively small and dispersed. Cheaper and easier to set up and more difficult to target than the massive hydrogenation plants Germany predominantly relied on. Plants that were hit would be much less costly to repair or replace, and moving/expanding the production network would be much faster, easier, and generally more flexible. This might also have alleviated at least some pressure on the transportation network as less centralized fuel production and storage could potentially mean shorter distances to get where it needs to be. (that depends on the exact distribution of those factories and which fronts are more active)
But better defensive capabilities in general is one of the serious issues that needed to be dealt with. Even in hypothetical cases of different offensive strategies or more compromises made to avoid further expansion/conflict in favor of holding/stabilizing central Europe under Axis control you'd need to maintain air superiority with strong day and night defenses. (better coastal defenses too) But following the Blitzkrieg with digging in and preparing for a cold war was not part of the existing plans. (or fitting for Nazi doctrine in general)
Even a literally cold war! The worn winter camouflage so beloved of aircraft modellers dates almost invariably from the first winter of the war in the east (41/42). The Luftwaffe did not have a permanent white camouflage aircraft lacquer available until the following winter. But then there was no intention to have to fight over one winter, let alone several.
Cheers
Steve
syscom3
Pacific Historian
This is like a chemistry lesson.
kool kitty89
Senior Master Sergeant
Let alone dealing with Russian winters ...
Oh, but a neat document relevant on the alternate fuel blends topic:
http://www.google.com/url?sa=t&rct=...=w36EQGfs91GL3iFCwcrfOg&bvm=bv.89947451,d.cGU
It includes use ethanol, n-butanol, acetone, various grades of gasoline, naphthas, and diethyl ether (poor octane but good vaporization characteristics, so tested to see what blends could still achieve acceptable octane ratings).
The naphtha fuel studies would be somewhat in line with Koopernic's comments on using kerosene in gasoline type engines. (but more in line with my own suggestions in focusing on normal gasoline types and blending other fuel types to improve vaporization and combustion characteristics)
