Japanese engines with water-alcohol injection

[tomo pauk]

A not-much talked topic. The Japanese installed water-alcohol injection in many, if not most of their engines by 1944-45, though the exact data is not that widely available, at least to my knowledge. So to start the ball rolling, here are two examples.
1st: Mitsubishi Ha-112 MK2 engine used on Type 100 (or Ki-46 as it is better known) recce aircraft, Allied name 'Dinah'. The power jumped by 300 CV in low gear of S/C, and 200 HP in high gear of S/C, per Soviet tests, when water-alc injection was applied. A part of their test report, pertaining on this topic, is attached, translation by your's truly. Full test: link
2nd: Nakajima Homare, where w/a injection improved power by some 200 HP. The excellent thread is here: link

 

[soulezoo]

Question: how large were the water/meth tanks? How does this compare to other Allied and Axis aircraft with M/W?

Also curious (and I realize this can vary wildly) about usage rate (litres per minute?) of M/W when employed.

 

[tomo pauk]

Unfortunately, the Soviet report does not mention the rate of usage nor the volume of the mixture in tanks.

 

[taly01]

Methanol Water tanks (MW50) around 100L, often could also be used as a reserve fuel tank for long range ferry flights! (Me109,Ki-43).

There are some tests of F6F and F4U on wwiiaircaftperformance.com and they said the Water injection system was not working properly when testing first started, ithink they also mention rate of flows. The MW injection requires pressure sensors, throttle sensors, pressurised injector system and clean injector nozzles to work! One source I read says F6F sometimes removed it cause its a PITA.

 

[tomo pauk]

Methanol Water tanks (MW50) around 100L, often could also be used as a reserve fuel tank for long range ferry flights! (Me109,Ki-43).

That warrants at least two questions:
- was the Ki-43 ever outfitted with water-alcohol injection?
- have the of w-a tanks ever got the separate fuel transfer system?

One source I read says F6F sometimes removed it cause its a PITA.

Questions again:
- what is the source?
- who ordered/authorized the removal?

 

[greybeard]

I think the point is wondering why they resorted to water-methanol/ethanol injection.

The mixture at high specific heat (heat quantity to raise temperature by one unit for unit of reference; e.g.: 1°C for 1 cubic decimeter) injected into supercharger intake is a poor means to allow higher total compression ratio (I mean that of supercharger + that inside the cylinder; that's to say the density of charge) without detonation. Heat absorbed by evaporation of the mix partly converts adiabatic compression inside the supercharger toward an isentropic one, providing better efficiency (higher output pressures for a given power taken by supercharger).

Same results are got in a much more effective way having:

1. An higher octane fuel, allowing higher compression ratios
2. Technology (also intended as provision - by design, room, etc. - on a available engine) to put an inter/after-cooler.

A similar reasoning, can be applied to nitrous oxide versus turbo-supercharger.

Those devices, studied late in the war by Allied commissions already impressed by such technologies like Me 262 or Baka, may have appeared like advanced; actually, I think it was dictated mainly by desperation. Indeed, nowadays we've many supercharged cars: how many have a methanol-water injection?

 

[tomo pauk]

I think the point is wondering why they resorted to water-methanol/ethanol injection.

Your items 1. and 2. point us to the answer:

Same results are got in a much more effective way having:

1. An higher octane fuel, allowing higher compression ratios
2. Technology (also intended as provision - by design, room, etc. - on a available engine) to put an inter/after-cooler.

1. Japanese have had no high octane worth speaking about, they moved from 87 oct to just 92 oct. Higher compression ratio is a self-inflicted wound - reduce the compression ratio in order to maximize boost.
2. Nobody came out with intercooled/aftercooled single stage supercharged radial engine for service use in ww2. There is reasoning for that - there is no single manifold leading from superchager towards the cylinders like it is the case with most of V12 engines. Two-stage supercharged radial engine allows for an intercooler, that cools down the air compressed by the 1st stage.

So there was only one avenue where Japanese were able to increase the short-term power of their in-production radial engines - anti-detonant injection. We can also recall that some very powerful engines on the West also relied on ADI, despite having hi-oct fuel - V-1650-9, two-stage V-1710s, 2-stage R-2800, R-1820, late war German V12s, Sabre VII. Some of them also incorporated intercooling.

A similar reasoning, can be applied to nitrous oxide versus turbo-supercharger.

Nitrous-oxide system can be easily retrofitted on aircraft, the turbocharging cannot. Provided the turbochargers exist and work reliably.

Those devices, studied late in the war by Allied commissions already impressed by such technologies like Me 262 or Baka, may have appeared like advanced; actually, I think it was dictated mainly by desperation. Indeed, nowadays we've many supercharged cars: how many have a methanol-water injection?

Vast majority of supercharged cars are not military equipent, they are equivalent of light transport aircraft of ww2 if we really want to compare. Want extra power? People with money use the 'nitro' today.
The Allies were using ADI on their aircraft from late 1943/early 1944 - P-47s, F4U, F6U, FM-2, P-63. Let's recall that aircraft with water injection engines won perhaps all of post-war air races.

 

[soulezoo]

I think the point is wondering why they resorted to water-methanol/ethanol injection.

The mixture at high specific heat (heat quantity to raise temperature by one unit for unit of reference; e.g.: 1°C for 1 cubic decimeter) injected into supercharger intake is a poor means to allow higher total compression ratio (I mean that of supercharger + that inside the cylinder; that's to say the density of charge) without detonation. Heat absorbed by evaporation of the mix partly converts adiabatic compression inside the supercharger toward an isentropic one, providing better efficiency (higher output pressures for a given power taken by supercharger).

Same results are got in a much more effective way having:

1. An higher octane fuel, allowing higher compression ratios
2. Technology (also intended as provision - by design, room, etc. - on a available engine) to put an inter/after-cooler.

A similar reasoning, can be applied to nitrous oxide versus turbo-supercharger.

Those devices, studied late in the war by Allied commissions already impressed by such technologies like Me 262 or Baka, may have appeared like advanced; actually, I think it was dictated mainly by desperation. Indeed, nowadays we've many supercharged cars: how many have a methanol-water injection?

I have it in my truck... along with NOS. There's another reason for its use beyond what you identified. Injection into the airstream into the intake manifold (after intercoolers or CAC) is not done so much to cool the intake air, but rather to help keep in check exhaust gas temperatures within the cylinder. Most pistons are made of aluminum alloys and aluminum melts at 1220* F (roughly). EGT's can exceed this quite quickly. So the water injection (also used on jets for the same purpose) allows the use of a much larger fuel/air mixture (more power) than can be done safely without the aid.

 

[taly01]

<<That warrants at least two questions:>>> and some hoped answers.....

Me109 "extra" tank could take GM-1 nitrous/Methanol-Water/Fuel if plumbing was done, but i have no diagrams of it.
I think it was Janes F6F book (Anderton) that mentioned removing (or maybe not using) ADI equipment. It may have been as with 130 octane ADI was not needed with standard WEP boost setting? and F6F5 were hardly been in many desperate fights in 1945.

Ki-43-III Water methanol injector-------- 一式戦闘機「隼」研究所−栄（ハ２５、ハ１１５）エンジン
There was equipment of water methanol injection device characterizing the latter set of fighter "Hayabusa". In the Zero fighter, only one machine was manufactured and it did not reach practical use, but 1,153 aircraft were equipped in the fighter "Hayabusa" Type III.
With regard to Type III, Oshima Design Principal said, "In particular, it contributed greatly to the improvement of about 100 horsepower by water methanol injection.
This water methanol injection does not mean to obtain explosion cal (calorie) directly by burning water ethanol, but it is an abnormal explosion (detonation) due to high heat generation when the engine is compressed and rotated faster than before, It is a device to suppress detonation by cooling with water methanol, which improves the explosion resistance of gasoline and prevents the melting and destruction of pistons and valves.
Originally it is good to spray only water, but if it rises to high altitude in other than hot areas, it will be below 0 degrees and water will freeze, so methanol (methyl alcohol) is added to lower the freezing point and make it antifreeze. The equipment injects water ethanol with gasoline at a boost pressure of + 200 mmHg or more with a supplemental injection metering device using bellows, introducing it with air-fuel mixture into the cylinder and igniting it,
In addition, since the engine is mostly made of aluminum alloy, including with the piston, cylinder and cylinder body, we added a small amount of potassium dichromate for aluminum corrosion prevention in addition to water + methanol.................

+200mm Hg is only +4psi, So it seems fuel quality was low also.

 

[tomo pauk]

Thank you very much for the link, I'll dive in ASAP

 

[tomo pauk]

...
Me109 "extra" tank could take GM-1 nitrous/Methanol-Water/Fuel if plumbing was done, but i have no diagrams of it.
I think it was Janes F6F book (Anderton) that mentioned removing (or maybe not using) ADI equipment. It may have been as with 130 octane ADI was not needed with standard WEP boost setting? and F6F5 were hardly been in many desperate fights in 1945.

The use of R-2800-10 mandated the 100/130 grade fuel from get-go, it needed ADI in order to achieve war emergency power. Hence I'd politely disagree with claim that ADI system was removed for F6F in ww2.

Ki-43-III Water methanol injector-------- 一式戦闘機「隼」研究所−栄（ハ２５、ハ１１５）エンジン
There was equipment of water methanol injection device characterizing the latter set of fighter "Hayabusa". In the Zero fighter, only one machine was manufactured and it did not reach practical use, but 1,153 aircraft were equipped in the fighter "Hayabusa" Type III.

Bingo!

Originally it is good to spray only water, but if it rises to high altitude in other than hot areas, it will be below 0 degrees and water will freeze, so methanol (methyl alcohol) is added to lower the freezing point and make it antifreeze. The equipment injects water ethanol with gasoline at a boost pressure of + 200 mmHg or more with a supplemental injection metering device using bellows, introducing it with air-fuel mixture into the cylinder and igniting it,
...
+200mm Hg is only +4psi, So it seems fuel quality was low also.

The high compression ratio of the late-war Ha-115 (and Ha-45, the Homare, even more) will certainly make problems in achieving high boost values, especially on 92 oct fuel used by Japan. The bigger impeller on the Ha-115 will probably heat the charge more than prevoius models from the Sakae stable, hence ADI as necessity if more boost (=power) is wanted.

 

[taly01]

I ........ Heat absorbed by evaporation of the mix partly converts adiabatic compression inside the supercharger toward an isentropic one, ................ I think it was dictated mainly by desperation. Indeed, nowadays we've many supercharged cars: how many have a methanol-water injection?

Thats an interesting way to look at it as been a very expensive water evaporative air conditioner!

Australian SAAB dealers did sell a small batch of Saab 99 turbo with water injection! (and sports sedan 3 piece wheels and huge flared body kit) it let boost raise from around +12psi to +17psi.
Saab turbo cars increased their compression ratio from 7.2:1 in the first 99 turbo (draw SU type carb), then 8.5:1 when the got some anti knock sensor and 9:1 with some tweaks then finally up to 10.5:1 with a full computer controlled system that could allow for octane rating of fuel.

Its a pity they didn't have anti-knock sensors in WW2!

 

[BiffF15]

I think they did, called them "pilots", and performance varied...

Cheers,
Biff

 

[Koopernic]

Question: how large were the water/meth tanks? How does this compare to other Allied and Axis aircraft with M/W?

Also curious (and I realize this can vary wildly) about usage rate (litres per minute?) of M/W when employed.

Water/Alcohol mixture injection rates usually matched 1 for 1 fuel flow rates, about 0.55 lbs per hp per hour.

 

[tomo pauk]

...
Also curious (and I realize this can vary wildly) about usage rate (litres per minute?) of M/W when employed.

The only definitive data I currently have is for the DB 605 series of engines, where for example the DB 605AM used about 1 litre of MW 50 mixture per each 3.5 liters of fuel:

 

[vikingBerserker]

Great info!

 

[Koopernic]

The info I used came from a section on high altitude fighters in Rudiger Kosins book. Wait for a photo latter tonight. There is very specific info on GM1 flow rates for the Jumo 213E.

Note water is 40% more dense than avgas. Note the specification is for C3+MW50. Maybe B4+MW50 needed more water flow. We know DB played with spark plugs as well as piston strength, compression ratio, spark timing to get from 1.7 ata to 1.8 ata and latter.

The ability to use B4+MW50 instead of C3+MW50 became a big issue due to the allied oil campaign and it pretty much revamped the entire German engine production program. For instance the 1750 hip DB603E used B4 but to get to 2250 as the DB603EM it needed C3+MW50 this meant that the DB603LA was chosen for production as this could get the power with only B4+MW50 due to its intercooler. But for that problem the first Ta152 in production would have been the cropped wing Ta 152C with DB603EM.

This effected the DB605 as well, hence the DB603DB to use B4+MW50.

The Germans used two types of MW50 mechanisms. One system used supercharger pressure to pressurise the water tank to blow the water into the engine. This system was called Oldenburg on the Fw 190D9 and Ribbentrop on the Fw 190A9

Another system used a mechanical pump which because it achieved much better atomisation/vaporisation was a "high flow" system with greater power also used on the Fw 190D9. It made a big difference.

You don't want atomisation (droplets) but an actual vapour. Good mechanical atomisation at high pressure gets that started. It's possible that improved methods of water injection is what allowed the use of B4+ MW50 over C3+MW50.

Either way it's an interesting data sheet. Water usage is clearly very economical.

 

[DarrenW]

For what it's worth:

 

[mad_max]

WI on P & W had the fuel flow decreased when using it. WI most probably needed used on Japanese Engines because of the low octane fuels towards the end of WW2.

 

[DarrenW]

This is an excellent topic that's often neglected and sorely needs attention. Thanks Tomo for creating this thread. Because of it I've started researching information pertinent to late war Japanese radials and look forward to what others can share on the subject as well.