New Diesel engine
Thaddeus J. Beier
turbocharged V-4 Diesel that was shown in the latest _Sport_Aviation_.
They had a prototype or mockup at Oshkosh, mounted on the back of
a Velocity.
It was light, powerful, simple, cheap to run, compact; in short,
everything that an aviation engine needs to be (short of being
production, and with demonstrated reliability). It runs on
cheap fuel, and has all the great Diesel advantages: No
magnetos, spark plugs, carbs... This engine also had no
heads! As it is a two stroke, there are no valves at the
top, so everything goes into the cylinder up the bottom.
I would assume that there would be a fuel injector at the
top of each cylinder, although that wasn't clear from the
photos.
It looks just terrific, if a little odd. Does anybody know anything
more about it? I have been following homebuilt aviation for fifteen
years, and I have seen countless engines come and go, but this one
seems like the real thing.
thad
-- Thaddeus Beier email: th...@hammerhead.com
Technology Development vox: 408) 286-3376
Hammerhead Productions fax: 408) 292-8624
John Burnaby
>
>I am surprised that nobody here has commented about the new 2-stroke
>turbocharged V-4 Diesel that was shown in the latest _Sport_Aviation_.
>They had a prototype or mockup at Oshkosh, mounted on the back of
>a Velocity.
>
>
Double Ditto!! C'mon all you gearheads, let's rip this thing apart. Apart
from Jet A weighing more than AVGAS, where's the downside? assuming of
course that it holds together during testing. At least for discussion,
put the lack of history on this engine aside.
John
Frank Stutzman
Well, the obvious one to me is the lack of convenience. You can go to just
about any airport and find Jet A or some flavor of avgas. I have yet to
see any airport where you can get diesel on the field. Unless there's
a significant change in the number of diesel planes out there, I don't
see it changing.
(Thad, e-mail me and tell me how 70T is doing)
Frank Stutzman
Stutzman Consulting (on contract to Bay Networks)
fr...@stutzman.com
or fra...@baynetworks.com (until January 1, 1996)
(my English teach warned me about abusing parentheses)
Henry Eilts
>>My main objections with a two stroke compression ignition engine have
>>to do with scavenging (which is largely ameliorated with supercharging
>>but that adds complexity and cost) and exhaust temperature.
According to the Manufacturer's literature, the Zoche Aerodiesel exhaust
gas temperature is much lower than conventional piston engines. So low, in
fact, that EGT monitors, TIT monitors are not required. The cylinder heads
also run cool enough that shock cooling is not possible, and CHT monitors are
not needed either.
FYI.
Hank Eilts
My views are my own, not my employers.
John Burnaby
>
>In <Pine.SUN.3.91.951030151343.1070L-100000@niner> Frank Stutzman <fra...@baynetworks.com> writes:
>
>>On 30 Oct 1995, John Burnaby wrote:
>
>>> In article <1995102719...@hammerhead.com>, th...@hammerhead.com (Thaddeus J. Beier) says:
>>> >
>>> >I am surprised that nobody here has commented about the new 2-stroke
>>> >turbocharged V-4 Diesel that was shown in the latest _Sport_Aviation_.
>>> >They had a prototype or mockup at Oshkosh, mounted on the back of
>>> >a Velocity.
>>> >
>>> >
>>>
>>> Double Ditto!! C'mon all you gearheads, let's rip this thing apart. Apart
>>> from Jet A weighing more than AVGAS, where's the downside? assuming of
>>> course that it holds together during testing. At least for discussion,
>>> put the lack of history on this engine aside.
>
>>Well, the obvious one to me is the lack of convenience. You can go to just
>>about any airport and find Jet A or some flavor of avgas. I have yet to
>>see any airport where you can get diesel on the field. Unless there's
>>a significant change in the number of diesel planes out there, I don't
>>see it changing.
>
>the engine is called a "diesel" certainly has more to do with the ignition
>method (compression) than with the specifics of the fuel required.
>
>Ten to one this thing can burn everything from 100LL to home heating oil.
>But I'll bet it's happiest on Jet-A.
>
>But a TWO STROKE? Argh! Oh well, at least it's a diesel!
>
>greg
I sent for the info on this engine and this is what I learned.
200 hp @ 2500 rpm, 190 #'s w/accessories, turbocharged, dry sump oil
system direct drive, bsfc of .38 lbs/hp/hr of Jet A (@ 6.8 lbs/gal), cost
is $15,000. Inverted tractor engine will be available later. Test stand
runs have been very encouraging, flight testing should begin about now.
Engines to be available Feb. '96
John
Gregory R. TRAVIS
Hank,
Thanks for the info. My concern with exhaust temperature is not with the
actual cylinder discharge temperature but rather with the effect of an
exhaust pulse that occurs twice as often as with a four stroke.
On a four-stroke running at, say, 2400 RPM there are 1200 exhaust periods
per minute. The exhaust system can cool between periods. On the
same engine, but in two-stroke form, there are 2400 exhaust periods per
minutes. The manifold has only half as much time to cool between
periods which leads to a hotter manifold, overall.
Yes, in general diesels have much lower EGTs than spark ignition engines -
largely because of the higher compression ratios used and the shorter
burn times. Will this make up for the increased number of exhaust pulses,
temperature-wise? It very well may! If the manufacturer's data is talking
about integrated EGT then they've already answered the question - no
problem!
Even if it doesn't, is it a real problem? Probably not - it probably means
some heavier exhaust components and, perhaps, some shielding. Neither one
is a showstopper of course.
greg
Gregory R. TRAVIS
>200 hp @ 2500 rpm, 190 #'s w/accessories, turbocharged, dry sump oil
>system direct drive, bsfc of .38 lbs/hp/hr of Jet A (@ 6.8 lbs/gal), cost
>is $15,000. Inverted tractor engine will be available later. Test stand
>runs have been very encouraging, flight testing should begin about now.
>Engines to be available Feb. '96
This sounds excellent. Does the 190#s include the turbocharger and
sump (it's not clear from the above)?
A BSFC of .38 is fantastic. It works out to 8.4GPH at 75% cruise
power on a 200 HP engine. My 180HP O-360 would consume about 10GPH -
a little over a gallon and a half more per hour - while producing
less power!
Using comparative horsepower setting (~135 HP with is 75% of 180) I
get:
Dinosaurus Lycomingus: 10GPH @ $2.00/gallon = $20/hour fuel
5 hours endurance w/50 gal. usable
Dieselus Modernus: 7.6GPH @ $1.80/gallon = $13.70/hour fuel
6:30 hours endurance w/50 gal. usable
Over the 2000 hour TBO of my Dinosaurus, that's $12,600. What's the
price of this thing? $15,000? I want one!
I missed the configuration of the engine - is it something I can get
into my 172?
greg
Bill Wallace
>But a TWO STROKE? Argh! Oh well, at least it's a diesel!
>
>greg
Actually lots of the big diesels are two strokes, and they runs lots of
hours on them without problems. For instance, some of the large train
diesels are two strokes, as are some of the truck engines. However,
they bear little resemblance to what you normally think of as a
two-stroke, since it is fuel injected rather than carburated. The
burn cycle is also somewhat different than a regular 2 cycle since
exhaust timing and intake timing can be non-symmetrical around TDC.
Bill
Paul Neelands
>> ... At least for discussion,
>> put the lack of history on this engine aside.
In the late 1930's Germany was flying passangers from Germany to Argentina
nonstop with 2 stroke turbo diesel flyingboats. Enough history?
Paul Neelands
Building a COZY IV
Gregory R. TRAVIS
>crank to top of heads is 10.75". Engine is split horizontally at main
>bearings; upper half is one piece heads, cylinders,and 1/2 crankcase.
John,
I am drooling on my SHIRT! This engine not only weighs 100 pounds
LESS than my O-360 (190#s vs. 290#s), but it's narrower (21.5" vs. 33.37"),
shorter (17.8" vs. 24.59"), and not as long (17.3" vs. 29.05"). All the
while, it puts out MORE power on LESS fuel! And it's unaffected by
altitude (in that it's turbocharged). Is it an inverted-V or do I need
a periscope to see over it?
>My only reservation about this engine is that I hope to the depths of my
>ornithological soul that it doesn't turn out to be vapor ware. I requested
>more specifics from Doug Doers, the maker, re: background, torsional
>resonance issues, TBO, etc. but I haven't heard back from him yet. Will post
>when I learn any more.
I have got my checkbook ready; this should absolutely revolutionize the
market.
greg
John Burnaby
Greg,
The configuration is a V-4, 21.5" wide, 17.8" high, 17.3" long, center of
crank to top of heads is 10.75". Engine is split horizontally at main
bearings; upper half is one piece heads, cylinders,and 1/2 crankcase.
My only reservation about this engine is that I hope to the depths of my
ornithological soul that it doesn't turn out to be vapor ware. I requested
more specifics from Doug Doers, the maker, re: background, torsional
resonance issues, TBO, etc. but I haven't heard back from him yet. Will post
when I learn any more.
John
David Fisher
> <snip>
> >> ... At least for discussion,
> >> put the lack of history on this engine aside.
> <snip>
>
> In the late 1930's Germany was flying passangers from Germany to Argentina
> nonstop with 2 stroke turbo diesel flyingboats. Enough history?
There's never enough.
As of 1941, there were several significant aircraft diesel engines made
in Der Fadderland. They included:
1) Junkers Jumo 205 - 700 hp, 0.35 sfc, 1,257 lb, 1,014 cu in
2) Junkers Jumo 207 - 1,000 hp, 0.35 sfc, 1,430 lb, 1,014 cu in
3) Mercedes-Benz DB 602 - 1,320 hp, 0.36 sfc, 4,410 lb, 5,400 cu in
No idea why the M-B was not supercharged.
David Fisher
Chief Engineer
Fisher Research Corporation
David Munday
> in Der Fadderland. They included:
Das Vaterland.
--
Dave Munday - mund...@miavx1.acs.muohio.edu - mun...@nku.edu
PP-ASEL - Tandem Flybaby Builder - EAA-284 (Waynesville, OH)
Those who beat their swords into plowshares will plow for those who do not.
Boatfly
diesel.I want to send them some money.Not to hold a production slot just
yet,but just to support their lofty goals,I prey they succeed.
Luc JOB
>
>BTW, I have seen some talk about ethanol fuels - wouldn't that be about
>the same octane / other requirements as Jet-A?
>
Except that Jet-A is by far a better lubricant for the injection pump!!!
And has far less aggressive combustion by-products than any alcohol... the
turbo will appreciate the difference...
But with a special pump, exhaust pipe and turbo...
However, as far as I know ethanol fuels have an octane grade similar or
higher than gasoline and are more prone to replace it than
diesel...(ethanol is mixed with gasoline to increase its octane grade)
But if you want something 'green', diesel fuel (or kerosene, or Jet-A) can
be subsituted by estherified vegetal oil (colza) ... without any
modifications of the system...
But if your diesel is smoking black... it will also with colza oil...
---------------------------------------------------------------------------
Luc JOB Mat. sci. Eng. Swiss Federal Institute of Technology
E-mail: luc...@lmc.dmx.epfl.ch Lausanne (EPFL)
'If nothing else works... change the standards'
1963 JODEL DR-1051 HB-EBM, wood, fabric, 2+2, <6 gph @ >125kts...
---------------------------------------------------------------------------
Ron Natalie
: j...@ix.netcom.com (John Rourke ) wrote:
: >
: >BTW, I have seen some talk about ethanol fuels - wouldn't that be about
: >the same octane / other requirements as Jet-A?
: However, as far as I know ethanol fuels have an octane grade similar or
: higher than gasoline and are more prone to replace it than
: diesel...(ethanol is mixed with gasoline to increase its octane grade)
: But if you want something 'green', diesel fuel (or kerosene, or Jet-A) can
: be subsituted by estherified vegetal oil (colza) ... without any
: modifications of the system...
Ethanol (at least refined from corn) is not a 'green' fuel. Currently more
fossil fuel is used to produce it than it replaces when you burn it.
-Ron
John Rourke
>
>>The configuration is a V-4, 21.5" wide, 17.8" high, 17.3" long, center of
>>crank to top of heads is 10.75". Engine is split horizontally at main
>>bearings; upper half is one piece heads, cylinders,and 1/2 crankcase.
>
>
>I am drooling on my SHIRT! This engine not only weighs 100 pounds
>LESS than my O-360 (190#s vs. 290#s), but it's narrower (21.5" vs. 33.37"),
>shorter (17.8" vs. 24.59"), and not as long (17.3" vs. 29.05"). All the
>while, it puts out MORE power on LESS fuel! And it's unaffected by
>altitude (in that it's turbocharged). Is it an inverted-V or do I need
>a periscope to see over it?
>
>>ornithological soul that it doesn't turn out to be vapor ware. I requested
>>more specifics from Doug Doers, the maker, re: background, torsional
>>resonance issues, TBO, etc. but I haven't heard back from him yet. Will post
>>when I learn any more.
>
>market.
>
>greg
>
You're absolutely right, this in fact is probably going to be one of the more
interesting entries in the C.A.F.E. competition (Doug has already been invited, when
the engine is ready). I talked to them at Sun n'Fun last April - here's the story:
Step 1: Get it on a test stand, was supposed to be done in April, I received a letter
in August stating it had been delayed until 2nd week of Sept.
Step 2: Do a 100-hour test, check for wear, fuel consumption etc. This has probably
been done. (I'll check.)
Step 3: Fly the Velocity around the world with only two fuel stops, each leg being
9000-12000 miles. This will require an extra 200-240 gallon fuel tank.
Permits to install the temporary fuel tank, permission to fly over
foreign territories, tracking etc will have to be arranged. Doug says
that weather and winds favor a spring (April-May) or fall (Sept-Oct)
flight; I'm quite sure this hasn't happened yet, so I'm looking
forward to seeing it announced at Sun n'Fun next year, either as a
completion or as an actual date. Stay tuned!
Step 4: The most recent plan was to sell the engine for (you guessed
it) $15K, with a $2500 discount on the first 50 engines. This may have
changed.
I'm still considering it, but I want to see the flight first, and I
think my Velocity's going to be ready for an engine well before then.
Oh well! Can always change it out later!
BTW, I have seen some talk about ethanol fuels - wouldn't that be about
the same octane / other requirements as Jet-A?
-jpr
Mark Kromer
><snip>
>>> ... At least for discussion,
>>> put the lack of history on this engine aside.
><snip>
>
>In the late 1930's Germany was flying passangers from Germany to Argentina
>nonstop with 2 stroke turbo diesel flyingboats. Enough history?
In the thirties, Junkers produced the Ju 86 bomber which was powered by two
two-stroke diesel engines (also produced by Junkers I believe). It was a
sucessful design, but was superceeded before the start of WWII. The engines
were of an unconventional configuration being of the opposed piston type (two
pistons per cylinder arranged crown to crown). The engine had two crankshafts,
one at the top and one at the bottom which were geared together. This layout
allowed the intake and exhaust ports to be at opposite ends of the cylinder to
improve scavenging. I suspect that improvements in two-stroke port design
since the fifties may have made this complexity unnecessary.
- )V(ark)<
Ron Natalie
: In article <47bav5$1...@topaz.sensor.com>, r...@topaz.sensor.com says...
: >Ethanol (at least refined from corn) is not a 'green' fuel. Currently more
: >fossil fuel is used to produce it than it replaces when you burn it.
: So Ron, why is it that alcohol cost less than gasoline, diesel, jet-a,
: kerosene, or stove oil? You would think that if it took more fossil fuel
: energy to produce it than it contains, it would cost more. It costs me about
: the same as propane... 75 cents a gallon. It has less btu's but even if you
: compare it by the btu, it is still less expensive than the rest. What gives?
Energy efficiency is not directly translatable to price. Petroleum is
heavily taxed and corn is subsidized.
Electric heat is 100% efficient but it still costs more than heating
my house with a gas furnace.
-Rno
ChaniK
fuel. Octane ~110 with ~60% of the energy content per pound. You can,
however dump loads of it into your engine for power, since it also cools
the incoming fuel/air charge.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Kurt A. Kuhlmann
"Any aircraft can last a lifetime if you're careless enough."
http://user.aol.com/chanik/ed
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Charlie Kuehmann
Natalie) wrote:
> Energy efficiency is not directly translatable to price. Petroleum is
> heavily taxed and corn is subsidized.
>
> Electric heat is 100% efficient but it still costs more than heating
> my house with a gas furnace.
Ron, I don't think this is quite right. The most power you can get out of
an electrical power source into a resistive load is when the load is
matched to the internal resistance of the source. Thus at a maximum, the
source and the load are dissipating the same power, indicating the
efficiency is maximally 50%. True, you get the power you "pay for" with
electrical heat, but, without knowing it, you are paying for the power
that is dissipated by the source's internal resistance as well. A newer,
condensing gas furnace can be better than 90% efficient and will beat
electric heat anytime. Take an instance in which electric efficiencies are
much higher, such as in a well designed electric motor for an electric
vehicle and electrics will beat gas anytime. Nonetheless, I believe the
fact that electrical power is supplied by a regulated monopoly in this
country goes a long way to explain the prices we pay for this "cheap"
energy and, I agree with your comments about the subsidized and taxed
nature of fossil and alternative fuels. Sorry this is so off topic.
Cheers,
Charlie
--
Charles J. Kuehmann
The contents of this post are the opinions of the author and no one else.
Alexander Roup
>So Ron, why is it that alcohol cost less than gasoline, diesel, jet-a,
>kerosene, or stove oil? You would think that if it took more fossil fuel
>energy to produce it than it contains, it would cost more. It costs me about
>the same as propane... 75 cents a gallon. It has less btu's but even if you
>compare it by the btu, it is still less expensive than the rest. What gives?
It's because ADM ("Super Market to the World") gets *huge* government
subsidies to produce it. Look for this as an issue in the upcoming
presidential campaign. There is and editorial by James Bovard in the Nov.
2 Wall Street Journal which discusses this same issue.
David Fisher
> So Ron, why is it that alcohol cost less than gasoline, diesel, jet-a,
> kerosene, or stove oil? You would think that if it took more fossil fuel
> energy to produce it than it contains, it would cost more. It costs me about
> the same as propane... 75 cents a gallon. It has less btu's but even if you
> compare it by the btu, it is still less expensive than the rest. What gives?
Are you comparing bare prices, exclusive of taxes, and corrected for
efficiencies of scale?
David Fisher
ChaniK
especially in the midwest.
Charles K. Scott
gr...@silver.ucs.indiana.edu (Gregory R. TRAVIS) writes:
> I am drooling on my SHIRT! This engine not only weighs 100 pounds
> LESS than my O-360 (190#s vs. 290#s), but it's narrower (21.5" vs. 33.37"),
> shorter (17.8" vs. 24.59"), and not as long (17.3" vs. 29.05"). All the
> while, it puts out MORE power on LESS fuel! And it's unaffected by
> altitude (in that it's turbocharged). Is it an inverted-V or do I need
> a periscope to see over it?
Greg, stop this you're scaring me. This is entirely out of character
for you to be interested in a non aviation type engine. Halloween was
three days ago. :-)
Corky Scott
Dave J. Schwartz
: In article <47dai7$7...@topaz.sensor.com>, r...@topaz.sensor.com (Ron
While this is off the topic of aviation, I feel the need to correct the above
post. While he is correct that maximum energy transfer occurs in the matched
condition, peak efficiency occurs when the source resistance is very low
compared to the load resistance. This is, in fact, the conditions under which
the power grid operates. The builders of the power generation and distribution
equipment do everthing they can to make the grid look as much like a voltage
source with zero internal resistance. Obviously, they can't make it perfect
so there is some internal loss in the generators and grid; however, this is far
less than 50%.
------------------------------------------------------------------------------
/ | Dave Schwartz - Hewlett Packard, Spokane Division
/__ __ | P.O. Box 2500
/ / / / | Spokane, WA. 99220-2500
/ / /__/ |
/ | Internet: schw...@hpspkla.spk.hp.com
/ | Phone: (509)921-3648
-----------------------------------------------------------------------------
Stephens Akro - N31RS These opinions are strictly my own
----------------------------------------------------------------------------
Gregory R. TRAVIS
Oh Corky you misunderstand me so...
This engine sounds like a perfect aviation engine. Reliable, simple,
economical.
This is a direction in which Lycoming should have ventured two decades
ago. Frankly, the minute this company makes a production engine
for less than $30,000 that fits the other criteria that I've seen
here I'll buy one. Anything above a 1000 hour TBO will be icing on
the cake, all else being as stated, on this engine.
Not wearing any kind of costume,
greg
ChaniK
is
a measure of 'anti-knock'. Specifically, it is the ability of the fuel to
resist spontaineous auto-igniton of the endgas during the compression
stroke.
As the spark ignited flame front squeezes the remaining unburnt fuel/air
mixture in the cylinder, temperature rise leads to chemical changes such
as
the formation of alkyl radicals leading to chain branching of the
hydrocarbons via, primarily, HO2 and OH radicals. If the endgas
self-ignites, the resulting reasonant high pressure waves created by the
interaction of the desired flame front with the undesired endgas can
easily
destroy an engine in short order (aka detonation). Octane enhancers such
as
methyl tertiary butyl ether (MTBE) and tetra ethyl lead (TEL) act to
inhibit
these chemical pathways at various points, thus allowing the fuel to be
consumed by the flame front. As you can see, there is no mention of the
fuel
energy content. To a small extent, higher energy fuels can lead to higher
compression of the endgas which can exacerbate knock, but this is not a
dominant factor.
John Rourke
>
>Octane is not substantially related to the energy content of fuel. Octane is
>a measure of 'anti-knock'. Specifically, it is the ability of the fuel to
>resist spontaineous auto-igniton of the endgas during the compression stroke.
That's what I thought. I've spent the last hour or so at the RAFDC website
trying (in vain) to find the equivalent octane numbers for diesel and/or
biodiesel. Ethanol has an octane number above 100, I've seen 110-115 mentioned
as the range. Do you know what it is for diesel?
>As the spark ignited flame front squeezes the remaining unburnt fuel/air
>mixture in the cylinder, temperature rise leads to chemical changes such as
>the formation of alkyl radicals leading to chain branching of the
>hydrocarbons via, primarily, HO2 and OH radicals. If the endgas
>self-ignites, the resulting reasonant high pressure waves created by the
>interaction of the desired flame front with the undesired endgas can easily
>destroy an engine in short order (aka detonation). Octane enhancers such as
>methyl tertiary butyl ether (MTBE) and tetra ethyl lead (TEL) act to inhibit
>these chemical pathways at various points, thus allowing the fuel to be
>consumed by the flame front. As you can see, there is no mention of the fuel
>energy content. To a small extent, higher energy fuels can lead to higher
>compression of the endgas which can exacerbate knock, but this is not a
>dominant factor.
>
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>Kurt A. Kuhlmann
>"Any aircraft can last a lifetime if you're careless enough."
>http://user.aol.com/chanik/ed
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
My original question was that since ethanol is being looked at as a replacement
for 100LL when it is no longer available, this new engine might be an ideal
platform for such fuel:
1) Doug said it will burn most anything that won't knock at high compression (I
think he mentioned 12:1, I'm not sure)
2) Even though gasoline technically has higher energy content (about 125,000
BTU/gal), improper ignition (estimated as high as 20% of the time) and a low
compression ratio of 7:1 or 8:1 (because of it's low octane) means it doesn't
convert all that energy content efficiently (as detailed in the above post),
and worse yet, doesn't burn completely, leaving excess unburned hydrocarbons.
3) Ethanol has only 75,000 BTU/gal, and therefore performs poorly in comparison
to gasoline, possibly showing a 30-40% range reduction, *AT LOW COMPRESSION
RATIOS*. Baylor University did studies using an O-235 and IO-540 with
high-compression pistons (9.7:1 for the O-235 and (I think) 10.5:1 for the
IO-540), and saw only a 10% range reduction, but a 20% increase in H.P. with
practically *ZERO WEAR*. It is now STC'ed for the Piper Pawnee, I believe, and
just about there for the Cessna 152. They also say a TBO of 4000 hours is
conservative!
4) Now, putting 2 and 2 together, integrating with respect to t and applying a
choice Laplacian Transform or two, I wonder if the 12:1 pistons in the engine
we were describing would be appropriate for even better utilization of an
alternative fuel such as ethanol.
Undoubtedly there are other factors I am not aware of - I only got the above
information in a couple hours of net-surfing. So now I'd like to throw out a
couple other questions:
1) What *are* the octane numbers for #2 diesel, stove oil (white gas?),
kerosene, JP-4, Jet-A or anything else you can think of that is easily
transported in liquid form (butane???). Or, if such fuels don't really
*have* an octane number, per se, where are they in relation to avgas
(this is a post about aviation, after all!) in areas of volatility,
specific BTU content, etc.
2) Are there any other alternative engines that are particularly well
adapted to high-compressibility (dare I say high-octane?) fuels? What
about rotary engines, turbine (other than pure jet) engines, Stirling
engines (probably not), whatever?
All you engine fanatics, let's hear it! 100LL will be gone soon, this
is the perfect time to tout your favorite alternative!
-jpr (Interesting sig pending. Website pending. Velocity pending.)
Gregory R. TRAVIS
[ About Octane]
John,
Here's an article I wrote a while back for this group.
------------------------------------
The octane number assigned to a motor fuel has very little to do with the
actual chemical "octanes" in the fuel and everything to do with how well the
fuel resists detonation (which is directly related to the amount of
energy (heat) required to get the fuel burning in the first place).
Therefore, it is possible to assign octane VALUES to fuel which contain no
octanes whatsoeve.
WHY DO WE CARE ABOUT OCTANE? WHAT IS PREIGNITION? WHAT IS DETONATION?
The octane value of a fuel is an empirical measure of its ability
to resist detonation and, to a limited extent, preignition.
What is preignition?
Preignition occurs when the fuel/air mixture in a cylinder
ignites BEFORE the spark plug fires.
It can be caused by burning contaminates (such as carbon, or
a spark plug of the wrong heat range) in the cylinder
or by extreme overheating.
What is detonation?
Detonation occurs when the flame-front in a cylinder does
not proceed smoothly from the point of ignition
(the spark plug) to the opposite side of the cylinder.
It refers to the SPONTANEOUS ignition of the ENTIRE
charge in the cylinder. This ignition is often
caused by the extreme pressure rise in the cylinder that
occurs when the charge is first ignited (by the
spark plug).
WHAT ABOUT FUELS?
There are six things to consider when comparing hydrocarbon fuels:
1. Volatility. In short, what's the fuel's propensity
to vaporize. This effects the ability to easily mix the
fuel with air and the fuel's tendency to "vapor-lock"
2. Pre-ignition & knock resistance. Referred to as "Octane value."
How much energey does it take to get the fuel burning - how much
does it resist auto-ignition from compressive heat?
3. Energy content. How much ENERGY can be extracted from
the fuel as a percentage of its volume OR mass.
4. Heat of evaporation.
5. Chemical stability, neutrality, and cleanliness
6. Safety
The first three factors are often confused and interrelated when, in fact,
they measure three completely separate things. There is no
natural collelation between them.
General rules:
Heavy fuels (diesel, jet): Low volatility, low knock resistance,
high energy PER VOLUME
Light fuels (gasoline): High volatility, high knock resistance,
low energy PER VOLUME
Note that gasoline, partially, makes up for its (relatively) low energy-per
gallon by the fact that a gallon of gasoline weighs less (by about 15%) than
a gallon of jet fuel.
Octane rating is in no way correlated with engine power
or efficiency. There is more potential "energy" in a gallon of
diesel fuel than a gallon of gasoline, yet the diesel fuel has a much
lower octane value (more on that below).
HOW DO YOU DETERMINE OCTANE?
Ok, then, how IS octane rating determined? First, you go out and get
a suitable supply of the fuel which you wish to test. Then, you get yourself
some heptane (made from pine sap) and some iso-octane (a petroleum
derivative). Finally, you and your buddies arbitrarily,
agree that iso-octane has an "octane" rating of 100 while heptane has
an octane rating of 0.
Next, you call up Waukesha Motors and order yourself an ASTM-CFR test
engine. This single-cylinder wonder has a three bowl carburetor and
a movable cylinder head that can vary the compression ratio while
the engine is running.
You fill the ASTM-CFR full of your "mystery" fuel and, for automotive
fuels, you run two test protocols using the ASTM. One protocol is
called the "motor" protocol and the other the "research" protocol.
You vary the compression ratio until the onset of knock and write down
all kinds of various scientific parameters.
Next, you run your "reference" fuel, made up of various proportions of
heptane and iso-octane through the ASTM-CFR. You keep varying the
proportion of heptane to iso-octane until you get a fuel that
behaves JUST LIKE (knock-wise) your "mystery fuel." Once you get
that, you say to yourself "How much heptane did I have to add to
the iso-octane to get the mixture to knock in the ASTM-CFR just
like my mystery fuel?" If the answer is, say, 10% heptane to 90%
iso-octane, your mystery fuel has an octane number of 90.
How do the "motor" and "research" protocol differ? Mostly in
input parameters. For example, in the motor protocol the inlet
temperature is maintained at 300F while in the research protocol
it's kept at 125F. The engine is run at 900RPM in the motor
protocol and 600 RPM on the research.
Note that the motor protocol and the research protocol will yield
different "octane" numbers. At the pumps, the numbers are averaged
together to get the value you see. The DIFFERENCE between the
two numbers is called the fuel's sensitivity. Highly cracked
fuels have high sensitivity while paraffinic fuels often show
near zero difference between the two. The fuel's sensitivity is
NOT published at the pump but can be a valuable indicator as
to the fuel's REAL WORLD octane performance. Remember, the
octane tests are conducted in a lab using a special test engine;
the lower the fuel's sensitivity, the more likely it is that
the fuel will, indeed, behave as expected. Generally, the
closer the fuel's RESEARCH rating to the published rating
the more reliable the published rating.
HOW DO YOU DETERMINE AVIATION GASOLINE OCTANE?
The octane of aviation fuel is not measured in exactly the
same was as is automobile fuel.
Once again, you start with your trusty ASTM-CFR engine. But, in the
aviation case, you do not vary the compression ratio to try and
initiate knock. Instead, you pressurize the intake to higher and
higher values until the onset of knock. Other than that, the parameters
are the same as for the "motor" method used for automobiles. Supposedly
the pressurization method (as opposed to changing compression ratios) is a
throwback to the 1950s and 60s when supercharging was common
in aircraft engines. The engineers were particularly concerned
with the fuel's behavior under boost.
The other major difference is that there are not usually two "protocols" for
testing aviation gasoline. There is just one. However, the test
is run twice. Once at the RICH limit (mixture full forward) for the engine
and again at the LEAN (mixture leaned to the lean limit as specified by the
manufacturer) limit. Thus fuel tested for aviation use gets TWO
octane ratings, neither of which is an average (100/130 for example).
Because of the different ways in which automotive and aviation
gasoline octane is measured one must be very careful when
comparing absolute numbers. 100 octane avgas is not equal
to 100 octane autogas (but it's close!). Note that the rich number
rating of an aviation engine will correspond very closely to its
autogas (mogas) motor rating requirement (see the above paragraph). Thus
when shopping for autogas for your 91/96 O-360, you should look for a
filling station at which the MOTOR octane rating of the fuel is at least 91.
You should also be careful leaning the engine as this may cause its
octane requirements to go above what the autofuel can provide. Look for
an autofuel with an octane number as far above the lower aviation octane
number as you can. If you can get one which is at or above the
"lean" octane requirement (the higher number) then you should be a-OK.
Thus an engine rated for 80/87 aviation should have no trouble whatsoever
running on 89 octane (or higher) unleaded. Engines rated for 91/96
should run on at least 91 (motor) octane unleaded but note that this is
lower than the lean limit requirements (96) of the engine. Therefore it is
especially critical to limit leaning with such an engine/fuel combo when
running at high power settings.
HOW DO THEY GET OCTANE NUMBERS ABOVE 100?
Often it's done by pure extrapolation. A more reliable method, however, is
through the use of so-called performance numbers. Briefly, these are
arrived at by determining the instantaneous mean effective cylinder
pressure (IMEP), using the fuel under test, at the highest boost
that does NOT cause knocking. This number is then multiplied by 100 and the
resultant is divided by the IMEP at the highest boost that does NOT cause
knocking on the 100 octane equivalent fuel.
HOW DOES LEAD AFFECT OCTANE?
Tetraethyl lead raises the "octane rating" of a fuel not because it
addes more "octanes" to the fuel but because it makes the fuel knock
at a higher compression ratio in the ASTM-CFR. It works by slowing
the flame front. Slowing the flame front has the effect of slowing the
pressure rise in the cylinder. Since the pressures do not rise as
fast, there is less chance of spontenous combustion AHEAD of the flame
front, which is what causes knocking. This, in turn, allows a higher
"real" compression ratio to be used.
WHAT OTHER FACTORS AFFECT OCTANE REQUIREMENTS?
Combustion chamber design, localized hot spots, piston speed, and a
host of other factors can all contribute to a engine's
propensity to ping.
Additionally, in the aviation world, altitude extremes and super/turbo
charging affect octane requirements. Increased induction pressures
(such as would be encountered in a turbo/supercharged engine) cause
more rapid flame-front propagation. Likewise, decreased exhaust
pressure (as would occur at altitude) also tends to increase flame-front
propagation speed. Both of these effects can combine to raise
octane requirements - especially at altitude.
Note that the latter effect also affects the proper fuel/air ratio
for BEST ECONOMY operation. The reason is left as an exercise for
the reader.
HOW DOES THE OCTANE OF DIESEL AND/OR JET FUEL COMPARE TO GASOLINE?
Diesel and Jet fuel (along with kerosene) have, indeed, TERRIBLE
"octane" numbers; typically about 15-25 "octane". They tend to ignite
easily from high compression. Their use in a gasoline engine will quickly
destroy the engine.
Diesel fuel is rated by its "cetane" number which is determined, like
octane, by running the fuel in a test engine. Instead of heptane and
iso-octane they use napthalene (cetane rating = 0) and n-cetane
(cetane rating = 100). In total opposite to octane ratings, the
higher the cetane rating the higher the fuel's propensity
to knock!
Just as using a fuel with an octane number higher than necessary in a gas
engine will gain you noting, using a fuel with a cetane number higher than
necessary in a diesel engine gets you nothing. On the other hand, where
using a fuel with too low an octane number in a gas engine will result
in a damaged engine, using a fuel with too low a cetane number of a diesel
engine will just result in a rough-running (or not running at all)
engine with no damage.
WHAT'S THE DEAL WITH DIESELS?
Why can diesel engines tolerate a low octane fuel? In all gasoline engines,
(including injected gasoline engines!) the fuel/air mixture is present
in the cylinder the entire time the piston is travelling upward on its
compression stroke. This means it could be ignited at any time whereas
we only want it to be ignited when the spark plug fires, some time
just before the very top of the stroke. Furthermore, we want a nice,
even, steady, pressure rise in the cylinder as a result of ignition. This
means that we want the "flame-front" to travel linearly from the source
of ignition (the sparkplug) to the other side. We do not want combustion
to occur randomly within the mixure as that may cause a too-rapid pressure
rise which will throw off all our calculations about where the piston should be
and when.
First, In a diesel engine there is NO fuel in the combustion chamber as the
piston starts up on its compression stroke. Instead, fuel is INJECTED at high
pressure (up to 3000PSI!) into the combustion chamber at the EXACT
moment when ignition is desired. In a diesel engine with a compression
ratio of around 20:1 (compared to 7:1 for many "modern" gas engines),
the heat of compression will have raised the combustion chamber temperature to
arond 1000-1500F. The injection time takes about .002-.004 seconds during
which the fuel spontanously ignites from the heat of compression at just
the right time. Even so, a diesel fuel with too low a cetane rating may
not ignite, or may ignite poorly - especially on cold days starting a
cold engine.
The second critical difference is that Diesels are set up to burn the fuel
in a slightly different way.
In a gas engine, you typically set it up so that the mixture is
ignited before the piston hits the top of the stroke. What you're
aiming for is for the mixture to be fully burned around the top of the
stroke - thus combustion pressures are maximized at the top of the stroke
and gradually fall off as the piston moves downward on the power stroke
(and increases the volume in the cylinder). Diesels, on the other hand,
are set up to inject fuel very close to the top of the compression
stroke. The fuel spontenously ignites (auto-ignition) and, actually,
"knocks" just like it does in does in a gasoline engine (hence the
classic diesel "knocking"). The combustion pressures in the diesel increase
evenly as the piston goes DOWN. The net result is that the diesel piston
"feels" a constant pressure on it as the piston travels from top dead
center to bottom dead center whereas a normally operating gasoline engine
piston "feels" a constantly decreasing pressure as it travels to the
bottom of the stroke. The net result is that the diesel feels a lot
lower PEAK pressure while the pressure is MAINTAINED over a longer
period. The gasoline engine feels a much higher peak pressure which
starts to fall off immediately as the piston travels downward. The
implication, for the latter, is that it periodically operates very
close to the capabilities of the base metals. Anything, such as knocking,
which increases those peak pressures even more is apt to push beyond the
capabilities of the base metals and result in engine damage.
Knock in a gasoline engine tends to occur at the END of combustion, when
pressures inside the cylinder have reached, as a result of spark ignition,
very high values - values high enough to auto-ignite the fuel.
Knock in a diesel engine happens at the BEGINNING of combustion as a direct
result of piston compression only. It is what allows FURTHER combustion
as the piston moves downward. This continued combustion keeps the cylinder
pressure constant as the piston moves towards BDC.
WHAT DOES A LOW OCTANE VALUE MEAN, TO ME?
In the absolute worst case, if the fuel is too low octane,
it may spontaneously ignite BEFORE the spark plug fires due to thermal rises
from the heat of compression or from "hot spots" in the cylinder itself.
This kind of ignition is called PRE-ignition (as opposed to knocking) and
is a PATHOLOGICAL case which will just turn an engine to scrap. Diesel
fuel is low enough octane that mixing it with gasoline can cause pre-ignition!
What usually happens, and what we usually call "knocking" or pinging is
that the fuel/air mixture does not ignite before the spark plug fires but
does ignite spontaneously after that. The sparkplug fires and this causes an
immediate, rapid, rise in combustion chamber pressure. This causes fuel on
the other side of the flame-front to ignite BEFORE the flame-front reaches
it. In turn, this causes combustion chamber pressure to rise even more
rapidly. The result is an "explosion" inside the combustion chamber
as opposed to the desired "just very rapid burning."
WHAT DOES A HIGH OCTANE VALUE MEAN, TO ME?
A high octane rating ensures that it takes a REALLY hot ignition source to
ignite the fuel (such as a spark plug or the flame-front itself) and not
just the rise in pressure & temperature that's a result of normal combustion.
Note that the thermal rises in the cylinder are in direct proportion
to the compression ratio of the engine (more below). The higher the
compression ratio, the higher the octane of the fuel that's needed.
Again, if the mixture in a gasoline engine ignites BEFORE the spark plug
fires, we call that "pre-ignition." Pre-ignition will damage an engine
before you finish reading this sentence. To reiterate, what we're really
concerned with is called "knock" and that's the spontaneous ignition
of the fuel-air mixure ahead of the flame-front as a result of the rise
in cylinder pressure caused by the onset of ignition (caused by the
firing of the spark plug).
WHAT ABOUT AIRCRAFT?
Now, back to aircraft. We want to make aircraft engines with the following
characteristics:
1. Very high power/weight ratio
2. Low specific fuel consumption (so we don't need to
carry around heavy fuel)
The easiest way to do this, without involving lots of complex machinery that
might fail and add weight, is to raise the compression ratio of the engine.
An engine's efficiency is in direct proportion to its compression
ratio. Unfortunately, raising the compression ratio means we
need to protect against knock/detonation. How do we do this?
We use high (100 octane) fuel!
greg
ChaniK
the speed of flame front propagation. It changes the chemistry going on
in the endgas under late compression at ~400 - 600 degrees C. Good post
though.
"The alkyl lead anti-knocks work in a different stage of the
pre-combustion
reaction to oxygenates. In contrast to oxygenates, the alkyl lead
interferes
with hydrocarbon chain branching in the intermediate temperature range
where HO2 is the most important radical species. Lead oxide, either as
solid particles, or in the gas phase, reacts with HO2 and removes it from
the available radical pool, thereby deactivating the major chain branching
reaction sequence that results in undesirable, easily-autoignitable
hydrocarbons."
ref: C.K. Westbrook "The Chemistry Behind Engine Knock"
Chemistry&Industry(UK), 3 August 1992
and Bruce Hamilton "Automotive Gasoline"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Kurt A. Kuhlmann - Empire Development Avionics
John Rourke
>
>In <47g1gj$e...@ixnews6.ix.netcom.com> j...@ix.netcom.com (John Rourke ) writes:
>
>[ About Octane]
>
Greg-
Hey, thanks! Every time I've had this conversation with someone who knows 'a little'
about octane, I ask them to get specific, and no one ever has like you just did!
Finally!
Anyway, a couple questions now, specifically related to two aircraft engines I am
considering:
1) Doug Doers' new purpose-built diesel aircraft engine, developing about 200+ HP at
100 lbs less than IO-360, at 66% specific fuel consumption;
2) Lycoming IO-540 with high-compression kit and certificated for
ethanol developing about 300 HP at 40 lbs more than IO-360, with 120%
fuel consumption.
Actually, after having learned a lot more in the last week about
ethanol, I wish I could go with an IO-360 using ethanol (will it be
certificated too?) yielding maybe 210-230 HP, or a regular IO-540 at
270 HP, but what to do when 100LL gets scarce?
Anyway, let's see what I think I've learned, based on your treatise:
1) Ethanol can be used with high compression because it resists
pre-ignition and knocking due to its high octane, while Jet-A can be
used with high-compression because of it's low octane giving it the
ability to ignite instantly upon diesel injection.
2) Ethanol (with a Reid vapor pressure of 2.5) and 'Jet-A' (I won't
call it diesel; diesel is a method, not a fuel, right?) will both be
harder to start, especially when it is cold.
Is that correct?
In the Baylor University research, they suggest having a small tank of
gasoline for starting, to get around the hard starting problem.
Question: How can you use 100LL in a situation optimised for
110-octane? Or do they really optimise it that high? Or does the fact
that an octane number above 100 is fictional, and there are some other
factors?
I'll ask Doug how he plans to get around hard starting on the diesel.
And does anybody know what happens to 100LL January of 96, when all
leaded gasoline is supposedly verboten?
Again, thanks. I've been reading this newsgroup for about 3 months
now, and I hadn't seen any reference to this.
-jpr
Johnny
>And does anybody know what happens to 100LL January of 96, when all
>leaded gasoline is supposedly verboten?
>
Lead sucks. Good to see it go. The sooner the better. Bye Bye.
BTW, there are a lot better ways to get a suitable octane rating besides
adding lead. I have seen racing fuel rated to a performance number of 120 with
no lead. Some tracks don't allow lead anymore. There just isn't any reason to
run lead through your engine and then into the atmosphere, and into what
will become your future crankcase waste oil. What's really crazy is that 100LL
still has gobs of lead in it. Low lead would imply just that, but as I
understand it, it still has more than pump regular, which fortunatly is just
about all gone. I will be glad to see 100 no-lead... so will my children, and
there children.
-j-
John Rourke
Yes, I think everybody agrees lead in the atmosphere is not a good
thing. And I'm glad to hear there are alternatives.
But do you know the answer to my question? Will 100LL be unavailable
53 days from now? What will replace it? What is the best alternative
to plan for now?
-jpr
Johnny
>
>Yes, I think everybody agrees lead in the atmosphere is not a good
>thing. And I'm glad to hear there are alternatives.
>
>But do you know the answer to my question? Will 100LL be unavailable
>53 days from now? What will replace it? What is the best alternative
>to plan for now?
From what I have heard from a couple different FBO owners, there are no plans
to discontinue 100LL or leaded fuel in general. I don't know if the EPA
mandates apply to aviation fuel or not. Or they may have a different time
frame for having to comply. I'm not worrying about it too much cause I run
auto fuel anyway.
-j-
KLBurke
~100octane in avaition fuel.
Gregory R. TRAVIS
>I believe that lyc and conny are addressing that issue currently as they know
>that no-lead is just around the corner. There new engines will have to be able
>to live with no lead (about time they figured it out). Of course the longer
>they wait, the more money they will be able to charge for the new replacement
>"upgrade" engines, and/or retro fit no-lead upgrade kits.
Lycoming did extensive research with unleaded fuels on its engine line in the
early-mid 1980s. The conclusion was that unleaded fuels, of sufficient
octane rating, would generally not be a problem as far as valve seat
recession was concerned.
I believe that they did find some seat recession at peak and near-peak
horsepower but found that a number of non-lead fuel additives took care of
the problem. Lycoming already uses hardened valves and seats.
Note that there are several SAE papers dealing with this very problem in
AUTO engines. Valve set recession is a problem with most reciprocating
engines when run on unleaded fuel at high power outputs.
>My buddy has a 125 hp O-235-L2C
>(compression increase STC) at 9.3:1 and it has displayed a touch of detonation
>when it is really hot when being run on 92 octane auto fuel... but the funny
>thing is that it has displayed the same hint of detonation on 100LL under the
>same hot conditions.
Yes - the 9.3:1 compression O-235 is known to detonate using 100LL under
certain situations! In particular, the STOCK sparkplug (as specified
by Lycoming for "normal" compression O-235s) will cause detonation. It's
important to go to a colder (Auburn) plug if you're going to run the O-235
at high compression.
My car (yes I know it is completely different inside the
>combustion chamber, but I going to mention it anyway) runs a 10:1 compression
>ratio, and it runs 38 degrees total spark advance with no ping on 92 octane
>pump primo. It has aluminum heads... when it had the iron heads I could only
>go to 9.5:1 before I got ping on the same fuel.
I'll bet your car has a hemi combustion chamber? The parallel-valve (non
hemi) combusion chambers used on some Lycomings and Continentals are not
exactly known for their detonation resistance.
Other than the above - I totally agree with Johnny; lead is a bad thing
all around. It's bad for our engines (car and aircraft) and it's bad for
the environment.
Now, if we could only find a REASONABLE substitute!
greg
Johnny
>Now, if we could only find a REASONABLE substitute!
>
>greg
Ditto!
-j-
Johnny
>
>Racing fuel is rated only by the research method, and so is equivalent to
>~100octane in avaition fuel.
huh?
So what do you have when you "research test" a fuel with a slower combustion
rate than 100% octane? What would the research octane of Methanol be then? Or
of Propane? Or Ethanol? The Union Oil racing fuel we use says 105 octane right
on the side of the barrel. So does the S&S and the H&H (except it's not 105
it's 113 and 115). When you order the fuel, you order it by Octane... "Ship me
10 barrels of 108 please".
Anyway, the point was that you don't need lead to get into performance numbers
and well over the 100 octane level.
Besides all that, the major problem comes when you take away the lubrication
properties of the lead in a lycoming or conny. Research done and reported by
the EAA would suggest that once a new lycoming has got a deposit of lead on
the valve face and seat (a deposit that never really goes away), it can then
run auto fuel without any apparent increase in valvetrain problems. But if you
take a new (or freshly rebuilt) lycoming and start it off on auto fuel, the
lack of that layer of lead on the valve face and seat seems to cause a higher
rate of valvetrain failures.
I believe that lyc and conny are addressing that issue currently as they know
that no-lead is just around the corner. There new engines will have to be able
to live with no lead (about time they figured it out). Of course the longer
they wait, the more money they will be able to charge for the new replacement
"upgrade" engines, and/or retro fit no-lead upgrade kits.
My O-235 has no problems on auto fuel. Super low compression, and it had about
1900 hrs of lead build up in the engine before it got any auto fuel. I know of
several 8.5:1 160 HP O-320's that get fed premium auto fuel (92 octane) on a
regular basis, and have no problems from it. My buddy has a 125 hp O-235-L2C
(compression increase STC) at 9.3:1 and it has displayed a touch of detonation
when it is really hot when being run on 92 octane auto fuel... but the funny
thing is that it has displayed the same hint of detonation on 100LL under the
same hot conditions. My car (yes I know it is completely different inside the
combustion chamber, but I going to mention it anyway) runs a 10:1 compression
ratio, and it runs 38 degrees total spark advance with no ping on 92 octane
pump primo. It has aluminum heads... when it had the iron heads I could only
go to 9.5:1 before I got ping on the same fuel.
If it get's really bad out there, and they take away all of the 100 octane
fuel, leaded or not, I suppose that we could all just go to auto fuel with
non-lead octance booster added to it. Or Ethanol. Or Methanol (add a couple
tanks for that one). Or even Propane if you designed the aircraft and tanks
for it. It would seem that any of those would be better than leaded avgas.
Just as a side note, if you ever get a chance to talk to a machinist that
works at a piston aircraft engine zero time shop, ask him what they have to
go through with the spent wash tank solution that is full of lead
contamination, in high concentration, when they have to get rid of it.
-j-
Lyons M G
avgas is the severe tendency for vapor lock at altitude. The issue of
reduced energy density is an issue also.
Basically they are able to use very high quantities of ethers to increase
the "octane rating at sea level for racing and street use but the vapor
pressure or pressure where the fuel evaporates at room temperature is
reduced to an unaccepatable level and the threat of vapor lock and
subsequent engine shut down precludes the use of this type of fuel in
aircraft.
alternative methods have been looked at but the energy density becomes
worse with the ones that I am familiar with.
diesel, kerosene and JP4 are basically the same fuel. they are not rated
with an octane number because they are designed to operate in a different
type of cycle. They are supposed to auto-ignite or detonate that is how
they run with out spark plugs. they use a Cetane number for comparision
which is basically how easy they will auto-ignite. If my memory is not
too far off I recall this to be equivilant to obout 50 octane fuel.
Bruce Frank
: I am surprised that nobody here has commented about the new 2-stroke
: turbocharged V-4 Diesel that was shown in the latest _Sport_Aviation_.
: They had a prototype or mockup at Oshkosh, mounted on the back of
: a Velocity.
: It was light, powerful, simple, cheap to run, compact; in short,
: everything that an aviation engine needs to be (short of being
: production, and with demonstrated reliability). It runs on
: cheap fuel, and has all the great Diesel advantages: No
: magnetos, spark plugs, carbs... This engine also had no
: heads! As it is a two stroke, there are no valves at the
: top, so everything goes into the cylinder up the bottom.
: I would assume that there would be a fuel injector at the
: top of each cylinder, although that wasn't clear from the
: photos.
: It looks just terrific, if a little odd. Does anybody know anything
: more about it? I have been following homebuilt aviation for fifteen
: years, and I have seen countless engines come and go, but this one
: seems like the real thing.
: thad
: -- Thaddeus Beier email: th...@hammerhead.com
: Technology Development vox: 408) 286-3376
: Hammerhead Productions fax: 408) 292-8624
But, it is not inexpensive to buy. Does the company have a flying example
out there? The "mock-up" has been around at OSH for so many years many
don't believe it is really into production yet.
Bruce A. Frank, "Ford 3.8L Engine and V-6 STOL
b...@marlin.ssnet.com Homebuilt Aircraft Newsletter"
*--------------------------------**----*
\ (-o-) / AIRCRAFT PROJECTS CO.
\_____/
/ \
O O
Terry Schell;x3332
>
>But, it is not inexpensive to buy. Does the company have a flying example
>out there? The "mock-up" has been around at OSH for so many years many
>don't believe it is really into production yet.
>Bruce A. Frank, "Ford 3.8L Engine and V-6 STOL
>b...@marlin.ssnet.com Homebuilt Aircraft Newsletter"
Bruce-
I think you are confusing this engine with *another* diesel that has
been showing up for OSH for about 6 yrs. without going into
production. The engine being discussed has only been to OSH once -
although there were pictures of it in the Velocity booth in '94.
You're right about it not being that cheap (at least initially), but
this doesn't look like "vaporware."
BTW - does anyone know what is happening with that *other* diesel? I
am still interested, but have begun to loose faith.
Terry