Use of 150 octane fuel in the Merlin (Xylidine additive etc etc)

In article ,
(The Enlightenment) writes:
(Peter Stickney) wrote in message ...
In article ,
Dave Eadsforth writes:

A few points here.

In order to improve altitude performance, you've got to increase the
compression ratio of the induction system, or add an axidizer to the
fuel-air mix to help it burn. This can be done by adding supercharger
stages (Basically one supercharger feeding another, like, say, a
Merlin 60 series engine, or the turbosupercharger/engine driven blower
setups on the P-47 and P-38, or piping something like Nitrous Oxide
into the induction system, as the Germans did.

Nitrous oxide was more a technique the Germans were forced into to
help overcome a German disadvantage in high octane or high test
aviation fuels rather than a paucity in thingking.

No. Nitrous Oxide injection (GM1, in the German nomenclature) as used
by the Germans, did not increase engine power below the critical
altitude of the supercharger. It was used to increase the critical
altitude of the engine, by increasing the partial pressure of oxygen
in the fuel-air mixture.
One of the drivers of the need for this system was the supercharger
layout chosed for their large inline engines, the Daimler-Benz 60x
series, and the Junkers Jumo 211 and 213. Instead of having a
centrifugal blower mounted on the back of the engine, with air fed
from directly behind, thus allowing for easy installation of a second
supercharger stage, and the intercoolers that it requires to keep the
charge temperature down, the Germans went for a transverse
supercharger mounted transversely (cross-wise, if you will, with the
supercharger impeller's axis at right abgles to the engine's
crankshaft) fed from the side. This precluded a second supercharger
stage without a lot of drag-prodicing external ducting. THe Daimlers
also used a hydraylic variable speed coupling to drive the
superchargers on the DB601, DB603, and DB605. This is a very neat
idea. Ideally, it allows the supercharger to only draw off enough
power to produce the desired manifold pressure, so that there is more
power available at the propeller at altitude below the critical
altitude of the engine. There are drawbacks to this - Becasue it had
to operate ofer a wider speed range than gear-driven superchargers,
the efficiency of the DVL superchargers on the Merceded engines was
about 10-15% lower than those on, say, a Merlin or an Allison.
The supercharger drive also isn't as efficient, with losses in the
hydraulic system eating up about 3-4% of teh power needed to drive the
supercharger - It's like the lesser efficiency of a car with an
automatic transmission compared with th esame car with a manual
transmission.

The Germans _did_ use Anti-Detonant Injection (ADI, or MW50 in their
nomenclature) to allow increased manifold pressures (And thus
increased Horsepower) at lower altitudes. This was a 50/50 mix of
Mathanol and Water, injected into the eye of teh supercharger
impeller. It was used in some instances to make up the difference
between the German Low-Octane Avgas (87 Octane), and their High Octane
Avgas (96 Octane, not really high octane) in some engines, or to boost
the power of the high octane-rated engines at low altitudes.


The Germans did have techniques for manufacturing octane and even
higher knock hydrocarbons their technology was however more cumberson
than the US technology and this limited their production rate. Why
this was I don't know. It may have had something to do with the fact
that they had access to only snythetic oils from fischer tropsch and
hydrogenation plants or their own small crude oil industry or
Romania's all of which are regarded as poor quality crudes.
(California crude was rather highly regarded). It may have just been
that they were unaware of the US techniques.

U.S. techniques were fairly widely known. Ethyl Gasoline had been
available since the mid 1930s. Most of the high octane avgas impetus
had come from Jimmy Doolittle at Shell. One would think that when teh
Germans took Rotterdame and Copenhagen that they'd have turned up that
information. Shell is a Dutch company, and their headquarters were in
Rotterdam. (In fact, the Shell Building was used as a Headquarters
building by the Germans.)


--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster

On Sun, 1 Feb 2004 23:53:51 -0500, (Peter Stickney)
wrote:

U.S. techniques were fairly widely known. Ethyl Gasoline had been
available since the mid 1930s. Most of the high octane avgas impetus
had come from Jimmy Doolittle at Shell.

In terms of raising the PIN above 87 octane with 100 octane,
absolutely. It took pressure from Doolittle to generate a USAAC
requirement for testing in 1935, and the results of that testing were
instrumental in justifying a British Air Ministry orders in 1936-7.

150 octane ratings appeared to me, from my reading of the supply
sources in the PRO and secondary sources in the oil company's
histories, to have evolved from investigation of rich-mixture response
of 100-octane supplies in the early forties. Xylidine, mentioned at
the beginning of the thread, was a Shell-derived substitute for cumene
to increase the PIN, but it was orginally used to reduce the quantity
of other iso-octanes required to blend with TEL-added feedstock to
produce 100 octane, and so stemmed from measures taken to increase
production of 100-octane supplies in 1942-43 rather than from a desire
to increase the octane rating to start with. Or at least that's how I
read it.

One would think that when teh
Germans took Rotterdame and Copenhagen that they'd have turned up that
information. Shell is a Dutch company, and their headquarters were in
Rotterdam.

Shell in the US were operationally administered seperately.

(In fact, the Shell Building was used as a Headquarters
building by the Germans.)

There was even a small hydrogenation plant in Rotterdam used for
producing iso-octanes for experimental testing, which surely could
have been used even if in small quantities.

Gavin Bailey

"Peter Stickney" wrote in message
...
In article ,
(The Enlightenment) writes:
(Peter Stickney) wrote in message
...
In article ,
Dave Eadsforth writes:

A few points here.

In order to improve altitude performance, you've got to increase
the
compression ratio of the induction system, or add an axidizer to
the
fuel-air mix to help it burn. This can be done by adding
supercharger
stages (Basically one supercharger feeding another, like, say, a
Merlin 60 series engine, or the turbosupercharger/engine driven
blower
setups on the P-47 and P-38, or piping something like Nitrous
Oxide
into the induction system, as the Germans did.

Nitrous oxide was more a technique the Germans were forced into to
help overcome a German disadvantage in high octane or high test
aviation fuels rather than a paucity in thingking.

No. Nitrous Oxide injection (GM1, in the German nomenclature) as
used
by the Germans, did not increase engine power below the critical
altitude of the supercharger. It was used to increase the critical
altitude of the engine, by increasing the partial pressure of oxygen
in the fuel-air mixture.
One of the drivers of the need for this system was the supercharger
layout chosed for their large inline engines, the Daimler-Benz 60x
series, and the Junkers Jumo 211 and 213. Instead of having a
centrifugal blower mounted on the back of the engine, with air fed
from directly behind, thus allowing for easy installation of a
second
supercharger stage, and the intercoolers that it requires to keep
the
charge temperature down, the Germans went for a transverse
supercharger mounted transversely (cross-wise, if you will, with the
supercharger impeller's axis at right abgles to the engine's
crankshaft) fed from the side. This precluded a second supercharger
stage without a lot of drag-prodicing external ducting.

I though one reason the Germans didn't have two stage superchargers
was because the lower levels of boost possible with their lower octane
fuels and larger swept volumes simply made duel stage superchargers
unnecessry or pointless. I also note that the Jumo 213E of the Ta
152H did have a two stage supercharger and an induction cooler so it
must have been possible, possibly with coaxial shafts? The Jumo 213E
also had an induction cooler which is presumably a cooling stage
before the induction manifold unlike the two stage merlin which had
the cooler between stages. I suspect that the intercooler of the
merlin is more efficient while the induction cooler method produces a
cooler charge.




THe Daimlers
also used a hydraylic variable speed coupling to drive the
superchargers on the DB601, DB603, and DB605. This is a very neat
idea. Ideally, it allows the supercharger to only draw off enough
power to produce the desired manifold pressure, so that there is
more
power available at the propeller at altitude below the critical
altitude of the engine. There are drawbacks to this - Becasue it
had
to operate ofer a wider speed range than gear-driven superchargers,
the efficiency of the DVL superchargers on the Merceded engines was
about 10-15% lower than those on, say, a Merlin or an Allison.

I think that some specialist Me 109G, those with the DB605AS engine,
were high altitude specialists. This was the superchager of the DB603
grafted onto to 603.

The supercharger drive also isn't as efficient, with losses in the
hydraulic system eating up about 3-4% of teh power needed to drive
the
supercharger - It's like the lesser efficiency of a car with an
automatic transmission compared with th esame car with a manual
transmission.

This Mercedes system was apparently developed from an mercedes
automatic transmision system for cars.



The Germans _did_ use Anti-Detonant Injection (ADI, or MW50 in their
nomenclature) to allow increased manifold pressures (And thus
increased Horsepower) at lower altitudes. This was a 50/50 mix of
Mathanol and Water, injected into the eye of teh supercharger
impeller. It was used in some instances to make up the difference
between the German Low-Octane Avgas (87 Octane), and their High
Octane
Avgas (96 Octane, not really high octane) in some engines, or to
boost
the power of the high octane-rated engines at low altitudes.


The Germans did have techniques for manufacturing octane and even
higher knock hydrocarbons their technology was however more
cumberson
than the US technology and this limited their production rate.
Why
this was I don't know. It may have had something to do with the
fact
that they had access to only snythetic oils from fischer tropsch
and
hydrogenation plants or their own small crude oil industry or
Romania's all of which are regarded as poor quality crudes.
(California crude was rather highly regarded). It may have just
been
that they were unaware of the US techniques.

U.S. techniques were fairly widely known. Ethyl Gasoline had been
available since the mid 1930s. Most of the high octane avgas
impetus
had come from Jimmy Doolittle at Shell. One would think that when
teh
Germans took Rotterdame and Copenhagen that they'd have turned up
that
information. Shell is a Dutch company, and their headquarters were
in
Rotterdam. (In fact, the Shell Building was used as a Headquarters
building by the Germans.)

The Germans had good chemistry and good chemists. The biggest
industry in the world even today. As early as 1939-40 Goering was
calling for the production of large quanties of high test avialtion
fuels what came of this demand I don't know.

I suspect that the effort of producing octane was such that they
simply did not build their force around it. Synthetic fuel already
cost 4 times the same as mineral oils.





--
Pete Stickney
A strong conviction that something must be done is the parent of
many
bad measures. -- Daniel Webster

"Peter Stickney" wrote in message
...

snip
The higher engine output comes from the increased Manifold Pressure.
High Octane fuels tend to have a somewhat lower energy content than
those with lower Octane (or Performance) Ratings. (Technically, if
it's over 100 Octane, it's a Performance Number.)

No, higher octane fuel burns slower; but it contains more usable energy.

"Tarver Engineering" wrote in message ...
"Peter Stickney" wrote in message
...

snip
The higher engine output comes from the increased Manifold Pressure.
High Octane fuels tend to have a somewhat lower energy content than
those with lower Octane (or Performance) Ratings. (Technically, if
it's over 100 Octane, it's a Performance Number.)

No, higher octane fuel burns slower; but it contains more usable energy.


The octane rating or RON (Research Octane Number) of a fuel has
nothing to do with its energy content. All hydrocarbons have an
energy content of about 11.5kW.Hr per kg. (about 41Mega.Joules per kg)
Ethyle and Methyl alcohole for instance have a RON of about 130
(which is why it is used in indianapolis car racing) yet have around
half the energy content of gasoline.

The fuels physical density does vary with gasoline being about 0.73kg
per litre while diesel is about 0.78kg per liter. Military aviation
fuels for piston engines, gas trubines and rockets are generally
designed to be physically as dense as possible.

While, as you say, an increased RON means that more of the fuels
energy can be used in a piston engine because it can be given a higher
compression ratio and therefore expansion ratio without preignition or
knocking. If the same gasoline is burned in a multifuel diesel, gas
turbine or wankel the best or worst RON makes no difference at all.

Higher RON number do two things: First they eliminate pre-ignition due
to hot surfaces or the high temperatures caused by compression.
Second they prevent explosive combustion. Combustion should be a
controlled burn at subsonic velocities along a wavefront explosive
combustion (not the technical term) means that the combustion becomes
supersonic and is propagated by infra red radiation simultaneously in
the mixture.

The higher RON of Allied engines seems to have been used not to
increase compression ratio to obtain more power but to allow higher
emergency boost pressures and this practice would not increase fuel
efficiency just maximum power. Both the Merlin and the German Daimler
Benz and Junkers Jumo engines seem to have had a compression ration of
around 6.5. (varying between 6.2 to 6.9 and also varying as to which
bank of cylinders due to the con rods/king rod differences). I
recollect the distinct impression that the Merlin even had LOWER
compression ratios than the German engines.

Diesel engines are given a cetane rating. high cetane numbers are
generally desirable as this means the fuel is easy to ignite but slow
to burn. A centane number of 45 is considered good and 30 is low.

The German synthetic fuel fischer tropsch plants produced
extraordinarily high centane ratings of around 85 (catalysts produce
long linear chains). This was so high it meant that exhaust
temperatures went up by 25% and efficienciues down by 5% as the fuel
barely finished its combustion by the end of the power stroke.
Generally German diesel was a mixture of high cetane Fischer Tropsch
diesel blended with low cetane diesel from the hydrogenation plants.
This then gave an ideal blend.

Oddly despite the ease of producing diesel they often had to make
substitute diesel (maximum power suffered) by blending 95 gasoline
with 5% motor oil as gasoline production was emphasised. It was the
Russians that used the safer diesel in their tanks.