Re: To Euno RE: German Aircraft Synthetic Fuel Usage

On Oct 10, 5:30 am, "Ken S. Tucker" <dynam...@xxxxxxxxxxxx> wrote:
To any and all engine experts.

On Oct 9, 5:16 am, Eunometic <eunome...@xxxxxxxxxxxx> wrote:> On Oct 4, 3:15 am, "Geoffrey Sinclair" <gsinclai...@xxxxxxxxxxxxx>
wrote:

[respectable snip]

I understand a turbojet engine can run on fairly
junky fuel compared to a piston job.
True or false [  ] , (place checkmark or X in box :-)
So what are the relative fuel quality tolerances?

Extremely wide: natural gas, blast furnace gas, kerosene, diesel,
white gasoline (no tetra ethyle lead or octane required). Like
modern engines the German jet engines could cope with a wide range of
liquid fuels.

The Jumo 004 was designed from the start to run on a grade of diesel
known as J2 with a heavier grade known as K2 as possible. The
decision was made on the basis of economy and safety.

Some Me 262 missions were actually conducted with crude oil that had
been impeller refined only. The fuel was warmed and pumped on board.

The BMW003 was delayed by a directive to convert its gasoline based
system to one able to run on similar fuels to the Jumo 004



I wonder if the superior developement of German
engines, especially axial flow, was partly motivated
by a rare insight by German command that they
might have quality fuel shortages going forward.

Jet engine development seems to have been driven by the RLM
however it was certainly a strong motivator.

You will note the unusual starting system.
A two stroke motorcycle engine with its own fuel supply ( a few
litres)
It had an electric start system that was backed up by ring pulls.
Secondly a special fuel for starting the engine, again a few litres.)

There were a series of gas turbines developed for tank propulsion
known
as the GT101 (a direct drive model), GT102(seperate drive turbine) and
GT103
(seperate drive turbine with a regeneration). I believe only the
first
was tried in a jagdpanther. It was meant to power the usual
panther and tiger tank series.

It was expected that they would be easier to produce, allow much
easier to
produce synthetic fuels and provide higher power to weight ratios.

The GT101, based on a scaled down BMW003 had an unusual multistage
gearbox designed to keep the engine
spool operating at an appropriate rpm.



But the Germans seemed to have problems with
the quality of metalurgy required for jet engines,
was that a skill problem and/or a resource/refining
problem?

Mainly the unavailability of alloying elements: nickel was especially
scarce but so was chromium.
Nickel is needed to provide creep strength which is particularly
important from the point of
view of turbine blades and turbine nozzles. Chromium provides
corrosion resistance as well as heat
strength.

The primary turbine alloy, Krupps tinidur, had about 30% nickel though
it had been recognized that
an increment to 60% would be advantageous. (the allied nimonic was
about 80%) however the 30% nickel content was eventually replaced with
a combination of manganese and additional chromium due to shortages.

Apart from the turbine and its inlet guide nozzles the rest of the
engines were made of plain steel with oxide coatings to provide
corrosion resistance: this includes the combustion chambers, exhaust
nozzle and other hot parts of the engine. This in itself vastly
reduced MTBO since the combustion chamber cans had to be replaced
every 25 hours (along with the complete turbines). New alloys had
been developed that were expected to achieve about 150 hours MTBO.
In reality the Germans were driven to developing 'disposable' all
steel turbines with a life of only 2 hours or so. Hopes rested with
ceramics and cermets, initially for the turbine inlet guide nozzles
and combustion chambers with a latter plan for water cooling of the
turbine itself or ceramic blades, perhaps constrained in a ring such
that they were under compression.

Fuel controls was a weakness of the early German engines leading to
flame outs and overheating unless carefully handled and though it was
also a weakness of the early British engines the British engines were
less 'sensitive' to the issue due to their centrifugal turbines less
peaky characteristics. The axial flow compressors certainly had less
frontal area and potentially more efficient (the reasons they were
chosen) they were however considerably heavier.

Lack of skilled labour certainly was an issue; prototype and
laboratory engines built by skilled personnel were considerably more
reliable: having said that; productionising any design can be
difficult.



I do understand it's an advanced skill to build good
superchargers and compressors, at that time, it still
is.

In addition I'll ask if the Germans succeeded in
prototyping a turbine powered tank. If so the Battle
of the Bulge may have been a victory.
Ken

It certainly would have helped the German fuel situation considerably,
provided tanks with a
superior power to weight ratio. The tanks as is typical would have
required more fuel but the
fuel would have been much easier to refine and produce with much
smaller refineries that require
less capital and steel per unit of output.

The problem with the German synthetic fuel industry is that it hadn't
been dispersed or hardened to resist air attacks since the Germans had
gambled all their resources up front on a quick war nor was it big
enough to supply all needs. Gas turbines would have helped however in
all these areas.

.

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