X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.100] (HELO ms-smtp-01-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 5.0c2) with ESMTP id 713624 for flyrotary@lancaironline.net; Tue, 06 Sep 2005 22:13:43 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.100; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-065-188-083-049.carolina.res.rr.com [65.188.83.49]) by ms-smtp-01-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id j872CuWf020929 for ; Tue, 6 Sep 2005 22:12:57 -0400 (EDT) Message-ID: <002a01c5b351$aa8a4b40$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Alternative fuel Date: Tue, 6 Sep 2005 22:12:58 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0027_01C5B330.2348E8B0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0027_01C5B330.2348E8B0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable =20 > Way to go, Rusty. >=20 > I'm no engineer, but I'm a pretty fair troubleshooter & recognize the=20 > need to ask the right questions & properly evaluate empirical = evidence. >=20 > In the '60s when I paid attention to auto racing, there were gas=20 > dragsters & then there were alcohol dragsters. (then nitro dragsters,=20 > but that's hardly relevant to aviation) The alky cars were noticeably=20 > faster, enough for a separate class. Indy cars in the '60s & early = '70s=20 > were alky powered. Don't know if that's still the case. This seems to=20 > run counter to 'conventional wisdom' I'm seeing here. (Sorry; I'm=20 > currently reading 'Freakonomics' & couldn't resist.) >=20 > The knocks against alcohol for potential damage to engines/fuel system = > components is deja vu to unleaded gas in the '70s. Anybody having=20 > problems with no-lead gas in their cars today? >=20 > Charlie > (trying for whitecaps) Glad to see you back on line, Charlie even if rooting for that trouble = maker, Rusty {:>). As best, I recall the one advantage to using alcohol as a fuel is its = resistance to detonation enabling much higher compression in these = engines. The alcohol normally used is methanol rather than ethanol. = Pure methanol has been used in indy cars since the mid-1960s mainly for = its high octane rating of about 135., so less likely to detonate under = high compression. Also as the following extraction will explain better = than I, other fuel characteristics that enable these engines to produce = so much power using methanol. In summary, You can run the engine much = richer, alcohol is better at cooling the charge density, much higher = compression piston (and/or boost), etc., than you can with gasoline.=20 HOWEVER, the bottom line is it still takes a much greater quantity of = alcohol than gasoline to produce the same amount of power. (Nitromethane = is a bit different story). Now if you can get a 15:1 or better = compression ratio out of your rotor, are prepared to run a blower or = turbocharger and can fit extend capacity fuel tanks to your bird then = you will likely produce more power.. Otherwise, I don't believe it = will. Ed A Extracted from Internet Sources: =20 Now unlike petrol you will find alcohol fuel will continue to provide = increased power for a mixture well above the ideal mixture strength and = you can always tend, therefore, to jet up on the rich side, and so avoid = any possible chance of running into troubles through weak mixture = causing burnt valves and holed pistons. This larger amount of fuel compared to petrol and especially as it is a = fuel with much higher latent heat value tends to do two things. The = density of the charge entering the engine is higher than petrol and a = greater weight of mixture is therefore being exploded. This is a fuel with a large cooling effect provided by part of it = evaporating after it has reached the combustion chamber and so tending = to cool the valves, piston and so on. Some may well get into the combustion chamber as liquid, due to the = reduction in temperature of the induction system, pipes, carburetor, = etc., and so extending the cooling effect, in the process counteracting = the effect of the high internal temperature. In view of this amount of fuel entering the chamber, with possibly some = of it in liquid form, the ignition system must be beyond reproach since = if the spark is weak the mass of fuel will just soak the plug and then = at once ignition troubles arise affecting starting in particular. Owing to the use of alcohol a higher compression ratio can be used with = this fuel as compared with petrol, another consideration is the type of = plug used which will be a hotter type than used before with petrol. NINETEEN TO ONE We have just mentioned the higher possible compression ratio used with = alcohol and the limit that can be used with any particular fuel depends = on the tendency of the fuel to detonate. As a rough guide the ratio for petrol is limited to about ten to one, or = with certain additives to as much as 12 to one. With alcohol, however, = you can go up to 19 to one or higher in certain cases. (For all = practical purposes however, 14 to one should be considered the maximum = usable ratio in modern short stroke automotive engines.) The possible use of a much higher ratio, of course, means we get a = higher power output from the engine, and this, in fact, is almost the = main advantage of alcohol fuel. DETONATION Detonation with alcohol fuel is really not a problem, but pre-ignition = is, or could be unless the mixture is kept well on the rich side. The reason for this is that if the mixture is on the weak side it burns = slowly and can still be so doing when the exhaust valve has opened which = then becomes overheated. This in turn ignites the next charge before the = correct time, the whole process becoming a chain reaction causing even = more rise in temperature and so it goes on until the piston holes and = other damage then follows. The first signs of this process taking place are a loss of power, a = general rise quite quickly of overall temperature, the head in = particular. To avoid this, run on the rich side always and use plugs with a good = heat capacity. It might be worth mentioning at this point that an engine set up = correctly for running on alcohol, even though on a rich mixture, will be = found to be (compared to petrol), a much cleaner running engine inside = the cylinder head, and provided the ignition side is up to its job there = will be less fouling of plugs than on petrol. Regarding Nitromethane: Note how with 40 per cent nitromethane mixture the jet size has = increased by 1.41, or put another way by 40 per cent on the diameter, = which as mentioned before means an actual fuel flow of twice the = original amount, so by comparison with petrol we now have four times as = much fuel required by the engine. ------=_NextPart_000_0027_01C5B330.2348E8B0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
> Way to = go,=20 Rusty.
>
> I'm no engineer, but I'm a pretty fair = troubleshooter=20 & recognize the
> need to ask the right questions & = properly=20 evaluate empirical evidence.
>
> In the '60s when I paid = attention=20 to auto racing, there were gas
> dragsters & then there were = alcohol=20 dragsters. (then nitro dragsters,
> but that's hardly relevant to = aviation) The alky cars were noticeably
> faster, enough for a = separate=20 class. Indy cars in the '60s & early '70s
> were alky = powered. Don't=20 know if that's still the case. This seems to
> run counter to=20 'conventional wisdom' I'm seeing here. (Sorry; I'm
> currently = reading=20 'Freakonomics' & couldn't resist.)
>
> The knocks = against=20 alcohol for potential damage to engines/fuel system
> components = is deja=20 vu to unleaded gas in the '70s. Anybody having
> problems with = no-lead=20 gas in their cars today?
>
> Charlie
> (trying for=20 whitecaps)
 
Glad to see you back on line, Charlie even if = rooting for=20 that trouble maker, Rusty {:>).

As best, I recall the one advantage to using = alcohol=20 as a fuel is its resistance to detonation enabling much higher = compression in=20 these engines.    The alcohol normally used is = methanol=20 rather than ethanol.  Pure methanol has been used in = indy=20 cars since the mid-1960s mainly for its = high octane=20 rating of about 135., so less likely to detonate under high = compression. =20 Also as the following extraction will explain better than I, other fuel=20 characteristics that enable these engines to produce so much power using = methanol.  In summary, You can run the engine much richer, alcohol = is=20 better at cooling the charge density, much higher compression piston = (and/or=20 boost), etc., than you can with gasoline. 
 
 HOWEVER, the bottom line = is it=20 still takes a much greater quantity of alcohol than gasoline to produce = the same=20 amount of power. (Nitromethane is a bit different story).  Now = if you=20 can get a 15:1 or better compression ratio out of your rotor, are = prepared to=20 run a blower or turbocharger and can fit extend capacity fuel tanks = to your=20 bird then you will likely produce more power..  Otherwise, I don't = believe=20 it will.
 
Ed A
 
Extracted from Internet Sources:
 
Now unlike petrol you will find alcohol = fuel will=20 continue to provide increased power for a mixture well above the ideal = mixture=20 strength and you can always tend, therefore, to jet up on the = rich=20 side, and so avoid any possible chance of running into troubles through = weak=20 mixture causing burnt valves and holed pistons.

This larger = amount of=20 fuel compared to petrol and especially as it is a fuel with much higher = latent=20 heat value tends to do two things. The density of the charge = entering=20 the engine is higher than petrol and a greater weight of mixture is = therefore=20 being exploded.

This is a fuel with a large cooling = effect=20 provided by part of it evaporating after it has reached the combustion = chamber=20 and so tending to cool the valves, piston and so on.

Some may = well get=20 into the combustion chamber as liquid, due to the reduction in = temperature of=20 the induction system, pipes, carburetor, etc., and so extending the = cooling=20 effect, in the process counteracting the effect of the high internal=20 temperature.

In view of this amount of fuel entering the chamber, = with=20 possibly some of it in liquid form, the ignition system must be beyond = reproach=20 since if the spark is weak the mass of fuel will just soak the plug and = then at=20 once ignition troubles arise affecting starting in=20 particular.

Owing to the use of alcohol a higher = compression=20 ratio can be used with this fuel as compared with petrol, = another=20 consideration is the type of plug used which will be a hotter type than = used=20 before with petrol.

NINETEEN TO ONE

We have just mentioned = the=20 higher possible compression ratio used with alcohol and the limit that = can be=20 used with any particular fuel depends on the tendency of the fuel to=20 detonate.

As a rough guide the ratio for petrol is = limited to=20 about ten to one, or with certain additives to as much as 12 to one. = With=20 alcohol, however, you can go up to 19 to one or higher in certain=20 cases. (For all practical purposes however, 14 to one should be = considered the maximum usable ratio in modern short stroke automotive=20 engines.)

The possible use of a = much higher=20 ratio, of course, means we get a higher power output from the engine, = and this,=20 in fact, is almost the main advantage of alcohol=20 fuel.

DETONATION

Detonation with alcohol = fuel is=20 really not a problem, but pre-ignition is, or could be unless the = mixture is=20 kept well on the rich side.

The reason for this is that if the = mixture is=20 on the weak side it burns slowly and can still be so doing when the = exhaust=20 valve has opened which then becomes overheated. This in turn ignites the = next=20 charge before the correct time, the whole process becoming a chain = reaction=20 causing even more rise in temperature and so it goes on until the piston = holes=20 and other damage then follows.

The first signs of this process = taking=20 place are a loss of power, a general rise quite quickly of overall = temperature,=20 the head in particular.

To avoid this, run on the rich side = always and=20 use plugs with a good heat capacity.

It might be worth mentioning = at this=20 point that an engine set up correctly for running on alcohol, even = though on a=20 rich mixture, will be found to be (compared to petrol), a much cleaner = running=20 engine inside the cylinder head, and provided the ignition side is up to = its job=20 there will be less fouling of plugs than on petrol.
Regarding = Nitromethane:
 
Note how=20 with 40 per cent nitromethane mixture the jet size has increased by = 1.41, or put=20 another way by 40 per cent on the diameter, which as mentioned before = means an=20 actual fuel flow of twice the original amount, so by comparison with petrol we now have four times as much = fuel=20 required by the engine.  =
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