Japanese 91 and 92 oct fuel - 'rich response'? (1 Viewer)

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tomo pauk

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Apr 3, 2008
How much (if at all?) the octane number of Japanese 91 or 92 oct fuel changes/improves with engines running at rich mixture? Fell free to point out mistakes in nomenclature I'm probably making right now :)
 
Can't speak to the Japanese usage but Octane Number does NOT change unless and until you alter the composition of the fuel itself. Historically, Octane number is a ratio of Isooctane to Heptane. 100 Octane would be pure isooctane (at the time the highest degree of resistance to compressional ignition) and 0 Octane would be pure heptane (the lowest). So 90 Octane fuel would be 90% Isooctane and 10% Heptane (N.B. The actual fuel may or may not ACTUALLY be composed of these hydrocarbons. The rating indicates that the fuels resistance to detonation is the same as this mixture would be in the test engine). High compression engines require high octane fuels to prevent the fuel from ignition as the piston comes up compressing the fuel/air mixture. Such pre-ignition causes the engine to "knock" and can be highly destructive. (N.B. Octane rating has NOTHING to do with a fuels energy content. It simply a measure of the fuels tendency to burn rather than explode.
RICH and LEAN refer to the ratio of fuel-to-air delivered to the cylinders. RICH mistures are mostly fuel whereas LEAN mixtures are mostly air.
Octane ratings greater than 100 are possible because Isooctane is NOT the most knock-resistant substance. Pure ETHANOL for example has an Octane rating of 129. The old Tetra-ethyl Lead was the Octane Booster of choice at one time in all gasoline. Today it is no longer used except in aviation gasolines
 
Can't speak to the Japanese usage but Octane Number does NOT change unless and until you alter the composition of the fuel itself. Historically, Octane number is a ratio of Isooctane to Heptane. 100 Octane would be pure isooctane (at the time the highest degree of resistance to compressional ignition) and 0 Octane would be pure heptane (the lowest). So 90 Octane fuel would be 90% Isooctane and 10% Heptane (N.B. The actual fuel may or may not ACTUALLY be composed of these hydrocarbons. The rating indicates that the fuels resistance to detonation is the same as this mixture would be in the test engine). High compression engines require high octane fuels to prevent the fuel from ignition as the piston comes up compressing the fuel/air mixture. Such pre-ignition causes the engine to "knock" and can be highly destructive. (N.B. Octane rating has NOTHING to do with a fuels energy content. It simply a measure of the fuels tendency to burn rather than explode.
RICH and LEAN refer to the ratio of fuel-to-air delivered to the cylinders. RICH mistures are mostly fuel whereas LEAN mixtures are mostly air.
Octane ratings greater than 100 are possible because Isooctane is NOT the most knock-resistant substance. Pure ETHANOL for example has an Octane rating of 129. The old Tetra-ethyl Lead was the Octane Booster of choice at one time in all gasoline. Today it is no longer used except in aviation gasolines

The mixture does affect the resistance to detonation, which is why avgas used to be rated as 100/130 (lean/rich mixtures). It's also why you run the engine in full rich for take-off and climb (unless operating at a high altitude).
As to what the rich/lean ratings of the Japanese fuels were, that would depend on a number of things, like what they were using as an octane booster, and whether the numbers given were rich or lean ratings.
 
I mostly agree with what Mike has said. however.

RICH and LEAN refer to the ratio of fuel-to-air delivered to the cylinders. RICH mistures are mostly fuel whereas LEAN mixtures are mostly air.
This is bit misleading, the "ideal" mixture ratio is 14.7 parts air to 1 part gasoline by weight.
main-qimg-f17a9263e30d738a3ea362f07c846608.jpg

and
Engine-power-and-fuel-consumption-function-of-air-fuel-ratio.jpg


This is basic and supercharged aircraft engines do depart from basic (but only somewhat). Please note that on a volume ratio you need thousands of times more air than you do gasoline (actually about 9000 times more air). Gasoline, by weight is 46.75lb per cubic ft (depends on the gasoline), while air is about 0.075lbs per cubic ft at sea level. And if you need 14.7 times more air???
In the real world many engines actually used extra gasoline, over and above the amount needed for combustion, as an internal coolant. Hot raw fuel exiting the exhaust pipe/s ir exiting partially burned as black smoke (P-47s were notorious for this) but the engine was basically an air pump.

The rich and lean become important when some fuels were discovered to have a better knock rating than other fuels when run rich, say in that 12-13 ratio area or even richer. They jumped 10-20 points on the knock scale. other fuels showed no improvement and a few actually were worse when run rich.

You cannot have a rating higher than 100 octane because your reference fuel would be 100% octane and anything above that would be a guess. You could say "100 ocate + 1cc lead or 100 octane +4 cc lead" but this doesn't work well. it is cumbersome (try labeling a fuel truck that way). The next problem is that it is not liner, the change in behavior of the fuel is much less with the addition of the 4th CC of lead than with the first CC of lead, very diminishing returns.

This is why the PN (performance number) scale was invented/developed. It was also set up so that 100 octane was 100PN but that is the ONLY point at which the scales coincide. The lower you go the further they diverge.

As far as the Japanese fuels go, a lot depends on which oil fields the Japanese were using and how they were refining it. The Dutch East indies base stock oil contained a lot of aromatics and might have provided a significant change in rich mixture response. The British had no way to measure their first 100 octane gasoline but they knew they wanted the performance of good rich mixture response and at least specified the fuel had to contain 20% aromatics.
 
You cannot have a rating higher than 100 octane because your reference fuel would be 100% octane and anything above that would be a guess.
I will disagree with you on this point. Iso-octane and heptane mixtures are the reference standard for the Octane scale. The Research Octane Number. RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane. However there are many substances like ethanol, for example whose anti-knock properties exceed Iso-octane giving it a rating ABOVE 100.
The Motor Octane Number or the aviation lean octane rating is a better measure of how the fuel behaves when under load. MON testing uses a similar test engine as that used in RON testing, but with a preheated fuel mixture, a higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. As a result MON numbers are 8 to 10 lower than RON. Europe uses the RON as its rating while the USA uses the average of the RON and MON so "USA Regular 87 Octane" is 91-92 in Europe.

The mixture does affect the resistance to detonation, which is why avgas used to be rated as 100/130 (lean/rich mixtures).
Yes and you make my original point. Octane Rating is "Resistance to Detonation" or "Anti-knock". The fuel being used here has a fixed mixture composition and if run in a test engine would give a fixed RON and MON. BUT if that fuel is fed to an engine as a RICH mixture or a LEAN mixture the resistance to knock changes so while the fuel itself has a fixed composition and thus RON or MON, a RICH mixture of that fuel BEHAVES AS IF it had a higher Octane number just as the LEAN mixture BEHAVES AS IF it had a lower Octane number.
 
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I will disagree with you on this point. Iso-octane and heptane mixtures are the reference standard for the Octane scale. The Research Octane Number. RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane. However there are many substances like ethanol, for example whose anti-knock properties exceed Iso-octane giving it a rating ABOVE 100.

and when the fuel under test matches the performance of a test fuel consisting of 100% Iso-octane and 0% N-heptane you have a fuel with a rating of 100 octane. if the fuel performs better than 100% Iso-octane that is all you can say. Test Fuel XYZ is better than 100 octane but you cannot say it is 110 octane or 129 octane or any other number above 100 octane.

The scale stops. As I said you could try saying fuel XYZ is equal to 100% Iso-octane + x amount of lead, Lead did increase the knock rating of Iso-octane.

Some of the confusion may come from the Performance number scale. Some writers tend to use the numbers from the performance scale above 100 and just call it octane rating. It is not.
below 100 octane the octane scale works great, Test fuel ABC against 90% Iso-octane and 10% Heptane and if fuel ABC performs better than you know it is at least 90 octane, Then test it against 95% Iso octane and 5% heptane and find that it performs worse. Know you know that it is between 91 and 94 octane. Keep trying different blends of the Iso octane and Heptane until your ABC natches but does not exceed the performance of the Iso-octane/heptane blend and you have your ocate rating up to 100. But you can't go above 100 with any precision, all you can say is it is above 100 octane.
Yes Ethanol (when run rich, very rich) had an anti-knock over 100 but unless you have a reference fuel that is over 100 that is all you can say.
 
Can't speak to the Japanese usage but Octane Number does NOT change unless and until you alter the composition of the fuel itself. Historically, Octane number is a ratio of Isooctane to Heptane. 100 Octane would be pure isooctane (at the time the highest degree of resistance to compressional ignition) and 0 Octane would be pure heptane (the lowest). So 90 Octane fuel would be 90% Isooctane and 10% Heptane (N.B. The actual fuel may or may not ACTUALLY be composed of these hydrocarbons. The rating indicates that the fuels resistance to detonation is the same as this mixture would be in the test engine). High compression engines require high octane fuels to prevent the fuel from ignition as the piston comes up compressing the fuel/air mixture. Such pre-ignition causes the engine to "knock" and can be highly destructive. (N.B. Octane rating has NOTHING to do with a fuels energy content. It simply a measure of the fuels tendency to burn rather than explode.
RICH and LEAN refer to the ratio of fuel-to-air delivered to the cylinders. RICH mistures are mostly fuel whereas LEAN mixtures are mostly air.
Octane ratings greater than 100 are possible because Isooctane is NOT the most knock-resistant substance. Pure ETHANOL for example has an Octane rating of 129. The old Tetra-ethyl Lead was the Octane Booster of choice at one time in all gasoline. Today it is no longer used except in aviation gasolines

The "knock" test to determin RON Research Octane Number was done a standardised variable compression engine. It was kept in very careful condition and calibrated against known mixtures of iso-octane (trimethylpentane) and heptane. I'm pretty sure they weren't actually 'lean' mixture but actually done at stoichiometric ratio of about 14.7 : 1 parts by mass air to fuel that allows complete combustion. (This Air to Fuel Ratio is called Lambda = 1) The engine was started at low compression and then the compression ratio was increased till the the engine began to 'knock'. There was a sort of steel pin on top of the cylinder head that began to bounce wildly when the combustion in the engine went from deflagration (controlled subsonic wavefront burn) to detonation (simultaneous combustion at several points at supersonic speed from infrared ignition or possibly preignition from hot spots on the engine. You could hear it though.

In the 1930s under the leadership of James Doolittle (who was a big knob of some kind in the USAAC/USAAF) the US Airforce started to buy exclusively 100 octane fuel, at great cost, in order to encourage the oil industry to invest in the equipment to produce it. This fuel was 100 octane.

When one sees numbers such as 100/130 the first number is the RON (Research Octane Number) while the second was the PN (Performance Number) which was the [ercentage increase in power possible when the compression ratio was increased and the mixture was run rich which was about 12:1 or 13:1 to prevent knocking (Does Anyone Actually know the air fuel or lambda ratio used on Merlins?)

So 100/130 meant the engine could produce 30% more power at the same RPM if the compression ratio was increased. In practice this was done by increasing the supercharger pressure to squeeze in 30% more air. (Squeezing in more air increases power but it does so by burning more fuel, however in the Merlin this efficiently loss was countered by considerable gains in jet thrust)

British began experimenting with American fuel, developed their rix mixture tests and standardisations I think using exotic fuels from their empire and then developed at BP British Petroleum a process called 'acid alkylation'. It was this process that gave the RAF its very important fuel. This idea of using rich fuels came out of the Schneider Trophy Seaplane races where the R type engine used a mixture of toluene, methanol etc.

Pure octane has a 100/120 RON/PN but I don't think the US 100 octane fuel was tested for PN and no specification was issued until they began supplying the British. The Americans wanted sustained power and cruise efficiency. It might be desirable to run the engine at a stoichiometric ratio of 16:1 for cruise. (any less and one might get ignition problems)

The Japanese fuel seems to have been better than the 87 octane used by everyone else previous to this but one apparently has to differentiate between IJN (navy) and IJA (army) fuel.

I recall reading part of a diary by a Japanese school girl (not my waifu) where she say's she was sent to collect pine cones that they were told were for turning into aviation fuel. Years later I learned that pineol has an octane number of about 100 and that you can also get about 4 gallons per ton of paper pulp produced. Apart from coke and coal tar oils this is how the Germans made fuel in the first word war. The Finns in the 1970s/80s were planning on running their cars of pineol in a car Hesselman engine developed by SAAB.

The feed stock for iso-octane is iso-butylene gas which the US obtained from oil refineries and latter from a catalytic cracking process. The Germans had to synthesise it from coal derived syn gas but it was less efficient and they found they needed the iso-butylene for buna-n and buna-s synthetic rubber more urgently. The acid alkylation process was well developed in time for the BoB and obviously helped the US as well. The Germans started building acid alkylation plants in 1940 but only one was complete by 1943 so they just had to keep adding octane.

Japanese tried to build coal to oil using German tech plant but because they didnt built a pilot plant they made too many mistakes and the plant never ran.

Not much on Japanese fuel tech. There was some at fischer-tropsch.org but the university has taken it down. (too valuable in my view, it had all the German WW2 technology and some Japanese oil intelligence)
 
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but you cannot say it is 110 octane or 129 octane or any other number above 100 octane.
Not only CAN but it is done quite commonly :

"Leaded Gas Phaseout". U.S. EPA, Region 10. June 1995.
It is possible for a fuel to have a Research Octane Number (RON) more than 100, because iso-octane is not the most knock-resistant substance available. Racing fuels, avgas, LPG and alcohol fuels such as methanol may have octane ratings of 110 or significantly higher. Typical "octane booster" gasoline additives include MTBE, ETBE, isooctane and toluene. Lead in the form of tetraethyllead was once a common additive, but its use for fuels for road vehicles has been progressively phased-out worldwide, beginning in the 1970s.

The prime example of "Over 100 Octane Fuels" has been around for over 20 years: VP C16 Race Fuel (blue). C16 is designed for turbocharged, supercharged, and nitrous-assisted combinations. VP says C16 is good for combinations featuring compression ratios of up to 17:1, and is recommended by many of the top nitrous oxide companies. C16's octane rating is actually 117. That's the RON rating the MON is actually higher at 118. Their X16 (red) blend has a RON of 114 and their oxygenated Q16 (yellow) blend has a RON of 116.

Aral Ultimate 102 sold in Germany has a RON of 102. Petro-Canada's Ultimate 94 actually has a RON of 101.5. E85 fuel in the US, 85% ethanol, has a Octane (RON) of 102-105, benefitting from ethanol's RON of 108.6.

If you want more exotic compound not generally considered "fuels" XYLENE has a RON of 118 and a MON of 115. TOLUENE has a RON of 121 and a MON of 117.

On a personal note my Merc Maurader 429's rebuilt engine with shaved heads and copper head gasket ran 13:1 compression and would only run on Sunoco 260 with a (at the time) RON of 102-103

So I reiterate, Octane number RON or MON has nothing whatsoever to do with either fuel composition or energy content. The numbers indicate resistance to the pre-ignition tendency (burning vs. exploding) of the fuel. During the infancy of spark engine development Iso-Octane was the best substance known at the time and as such was given a 100 rating
 
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Blending octane number of ethanol in HCCI, SI and CI combustion modes. - Free Online Library

The Research and Motor octane number (RON and MON respectively) are used to characterize the autoignition properties of the fuel in the SI engines [25]. The scale of RON and MON are based on two paraffinic hydrocarbons: Iso-octane defines the maximum limit of the scale with a value of 100, and n-heptane defines the minimum limit of the scale with a value of 0 [25]. Although, it is possible to have fuels beyond 100 octane number. For fuels with octane numbers above 100, the scale is extrapolated through the addition of dilute tetraethyl lead (TEL) to iso-octane based on an empirically determined relationship [41]. This extends the octane number scale to its maximum value of 120.3. Blends of iso-octane and n-heptane are referred to as primary reference fuels (PRFs). A PRF65 refers to RON of 65 with iso-octane percentage of 65% and 35% of n-heptane by volume. The RON and MON are measured in a standardized single cylinder Cooperative Fuel Research (CFR) engine using ASTM standard tests [41,42]. The RON is obtained by running the CFR at 600 rpm, with an inlet air temperature of 52[degrees]C and constant spark timing of 13[degrees] before top dead center (bTDC). The compression ratio is adjusted until trace knock is detected. Since the CFR engine for this study was modified, RON for the fuel blends were obtained by determining the transfer function for PRFs ranging from 70 to 100. The transfer function for this study is defined as the conversion procedure of the compression ratio readout to the mixture of iso-octane and n-heptane. Figure 3 show the compression ratio for trace knock obtained in SI combustion mode with PRFs. Figure 4 illustrates the procedure followed to obtain the compression ratios for different PRF mixtures for the transfer function in the SI mode. A knock criteria of peak to peak pressure fluctuations of 2 bar [+ or -] 0.02 for a moving window of 188 cycles was set to determine the compression ratio. For all fuel blends, the compression ratio was adjusted until peak to peak pressure fluctuation of 2 bar was obtained. A lambda sweep was then performed to confirm that the lambda for maximum knock was used.

Note that the above references refers to HCCI engines, something I know BMW were working on in 1940 referred to as a ring cycle.

Below is the Wartsila Test Engine. These have been the way of testing RON for 100 years.
https://www.corelab.com/refinery/cms/docs/F1F2_Product_Brochure_GEA_30653.pdf
 
Thank you.

I have no idea of when they extended the octane scale beyond 100. I do know that the method of using 100 octane plus the amount of lead to get the anti knock result needed was considered in 1940 or so but rejected at that time. Or at least rejected by Sam Heron who helped come up with the Performance Number scale. During WW II and after in the aviation world this was the scale used to describe aviation fuel. 108/135 and 115/145 use PN figures. 100 Octane and 100 PN are equal.

However, to avoid confusion at the time, it was decided to keep the old octane ratings for fuels under 100 because the PN scale didn't track the octane scale under 100. It was much lower and it was felt changing existing fuel numbers would confuse things.
Heron was trying to come up with a scale or rating system that would reflect the actual difference in the fuels potential performance. Which the octane scale does not do and niether does 100 octane + X cc of lead. That is to say a change of several points on the octane scale does not track the difference in performance well depending on where on the scale you are. There is a much greater change between 96 and 99 octane than there is between 77 and 80 octane for example. Same with trying to use 100% iso octane + lead. There is a huge change in the 1st cc of lead and progressively less change the more lead is added. I will try to post a few charts later. The book I have is not in very good condition and trying to lay it flat in the scanner may finish off the binding.
 
Thank you very much for input and clarifications.
Questio: is it safe to assume that Japanese 91 and 92 oct fuel was just providing that kind of octane rating, regardless on mixture? Basically like the 87 oct behaved? Or I'm missing the mark widely?
 
Tomo, ot sure of your point/question here but comb through these US Navy reports:
The Japanese relied on US oil imports up to 1941 when the US stopped all exports to Japan. That drove the Empire to attack the Netherlands East Indies in order to secure oil supplies. In 1944 the Allies started the oil refinery bombing operations against Japanese refineries in Balikpapan, Borneo; this mirrored the same attacks they did the year before against the German oil refineries in Ploesti, Romania

The US didn't start attacking the home island oil refineries and synthetic oil plants in Japan in earnest until late in the war as the USN submarine attacks against Japanese shipping was quite effective in limiting the transport of Japanese fuel / oil to its own forces

As for fuels, the following were captured on Guadalcanal in 1942
15,000 gallons of Benzene
40,000 gallons of Diesel Oil
An unspecified amount of high quality kerosene
800-900 drums of 90 octane avgas
150,000 gallons of 65 octane motor fuel
800 gallons of lube oil

From REPORTS OF THE U. S. NAVAL TECHNICAL MISSION TO JAPAN
X-38(N)-1 Japanese Fuels and Lubricants-Article 1, Fuel and Lubricant Technology
http://www.fischer-tropsch.org/primary_documents/gvt_reports/USNAVY/USNTMJ Reports/USNTMJ-200K-0292-0390 Report X-38 N-1.pdf

X-38(N)-2 Japanese Fuels and Lubricants-Article 2, Naval Research on Aviation Gasoline
http://www.fischer-tropsch.org/primary_documents/gvt_reports/USNAVY/USNTMJ Reports/USNTMJ-200K-0391-0884 Report X-38 N-2.pdf

X-38(N)-3 Japanese Fuels and Lubricants-Article 3, Naval Research on Alcohol Fuel

X-38(N)-4 Japanese Fuels and Lubricants-Article 4, Pine Root Oil Program

X-38(N)-5 Japanese Fuels and Lubricants-Article 5, Research on Rocket Fuels of the Hydrogen Peroxide-Hydrazine Type

X-38(N)-6 Japanese Fuels and Lubricants-Article 6, Research on Diesel and Boiler Fuels at the First Naval Depot, Ofuna

X-38(N)-7 Japanese Fuels and Lubricants-Article 7, Progress in the Synthesis of Liquid Fuels from Coal

X-38(N)-8 Japanese Fuels and Lubricants-Article 8, Naval research on Lubricants
http://www.fischer-tropsch.org/prim...rts/USNTMJ-200M-0022-0493 Report X-38 N-8.pdf

X-38(N)-9 Japanese Fuels and Lubricants-Article 9, Fundamental Hydrocarbon Research

X-38(N)-10 Japanese Fuels and Lubricants-Article 10, Miscellaneous Oil Technology and Refining Installations

In essence, the Japanese had the following avgas available for general use
92 octane - up to 1942
91 octane - 1942 to 1945
87 octane - last months of the war
100 octane - produced in experimental quantities
 
Not much on Japanese fuel tech. There was some at fischer-tropsch.org but the university has taken it down. (too valuable in my view, it had all the German WW2 technology and some Japanese oil intelligence)

Most of the Japanese tech may still be available from the Japanese Archives as most of the USSBS Japanese records are there. All you need is the right search item German translations of activities in Japanese aircraft production 7 September 1945. Report No. 9-a(50), USSBS Index Section 6 - 国立国会図書館デジタルコレクション the select English languare and click on the search icon.
 
The industry and its resultant innovation to support a wartime environment is almost unbelievable.
 

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