X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.101] (HELO ms-smtp-02-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTP id 1032766 for flyrotary@lancaironline.net; Mon, 13 Mar 2006 17:53:28 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.101; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-025-165.carolina.res.rr.com [24.74.25.165]) by ms-smtp-02-eri0.southeast.rr.com (8.13.4/8.13.4) with SMTP id k2DMqh4r006556 for ; Mon, 13 Mar 2006 17:52:45 -0500 (EST) Message-ID: <001301c646f0$d8202b00$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: heat output Date: Mon, 13 Mar 2006 17:52:45 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0010_01C646C6.EEE5E2F0" 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_0010_01C646C6.EEE5E2F0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Thomas, while there is probably more hydrocarbon (fuel) being ejected = from the combustion chamber ports of a rotary than a non-race = reciprocating engine , I think you will find that its already being = burned in the header pipes - that is one of the reasons for the Rotary's = hotter exhaust. So great idea, but I believe you will find its already = ignited in the 1700F+ temps of the exhaust. =20 Humm, so if its already ignited, then all we need to do is shape a = rocket reaction chamber shape and get additional thrust...... On the = other hand, I think a turbo charger would probably be a more effective = use of that exhaust energy. But, that's just my opinion and it might be = interesting to see if any thrust would result. Monty???. Ed=20 ----- Original Message -----=20 From: Thomas Phy=20 To: Rotary motors in aircraft=20 Sent: Monday, March 13, 2006 5:35 PM Subject: [FlyRotary] Re: heat output Hi guys, I've been kind of following this thread, and with my not so = engineering background, I was thinking (and that's dangerous). Just how = much unburned fuel are we pumping overboard? Is there enough to say, = shape the exhaust pipe into a nozzle, add an igniter, and have a home = boy's jato, on all the time? If so, how much thrust might it produce? = Just thinking out loud. TP I think this one is a no-brainer, but my mother often said the same = about me... Ernest, Not necessarily. The conventional wisdom: The Wankel has a higher exhaust temp because of uncombusted = hydrocarbons (due to the flat combustion chamber) and possibly a lower = expansion ratio (depending on which engine you may be comparing it to). = So the Lycoming may make more power for the same fuel flow with less = heat rejection. The Wankel also has a lot more surface area for the = combustion chamber and rotors so the heat rejected to the coolant will = be more. You never get something for nothing and giving up all those = valves, push-rods, lifters, ad nauseum, comes with a price. The price is = slightly higher cooling load and egts. Just to confuse the issue and tickle some nuerons: Now that is the conventional wisdom, and if you were to compare the = wankel to 4 cyl engine of 1.3 L displacement you would conclude that the = surface area is greater and the bearing area is greater etc. If you were = to compare it to a 3.9 L 6 cyl engine at 2/3 the rpm (which is a much = more accurate comparison IMNSHO) you might find the surface areas and = bearing areas are not quite so different after all. This is like saying = that a single cylinder 302 in^3 engine has less surface area than a V8. = DUH!!!. I don't recall anybody at the drag races with a 302 briggs in = their muscle car. So even if you say the frictional losses are actually fictional = losses, the lack of complete combustion and lower expansion still makes = for higher egt and less efficient operation. =20 From a cooling drag standpoint this is not good. You have to ingest = more air and you have a lower temperature gradient to work with than = with a Lycoming. This is all very academic, but in practice, I'm not = sure it makes a hill of beans. Most aircraft cooling systems are so far = from optimum that you will never get an apples to apples comparison, = plus props, airframes etc are all different. The other issue is the = rotary (normally aspirated fixed pitch) can be run LOP at most practical = power settings without damage. This is not true of the Lycoming. So this = makes up for some of the difference. Now if you have identical airframes = with ideal cooling set ups for both types of engines running LOP at the = same flight condition I think you would find the Lycoming may have a = very slight advantage in BSFC.=20 How much fuel can you buy for the price of top end overhaul on a = 180hp Lycoming? Or for that matter the difference in the purchase price = of the rotary vs. the Lycoming? Monty ------=_NextPart_000_0010_01C646C6.EEE5E2F0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Thomas, while there is probably more hydrocarbon = (fuel)=20 being ejected from the combustion chamber ports of a rotary than a = non-race=20  reciprocating engine , I think you will find that its already = being burned=20 in the header pipes - that is one of the reasons for the Rotary's hotter = exhaust.  So great idea, but I believe you will find its already = ignited in=20 the 1700F+ temps of the exhaust. 
 
Humm, so if its already ignited, then all we = need to do is=20 shape a rocket reaction chamber shape and get additional = thrust......  On=20 the other hand, I think a turbo charger would probably be a more = effective use=20 of that exhaust energy.  But, that's just my opinion and it might = be=20 interesting to see if any thrust would result.  = Monty???.
 
Ed
----- Original Message -----
From:=20 Thomas = Phy
Sent: Monday, March 13, 2006 = 5:35=20 PM
Subject: [FlyRotary] Re: heat=20 output

Hi guys, I've been kind of following = this thread,=20 and with my not so engineering background, I was thinking (and = that's=20 dangerous). Just how much unburned fuel are we pumping overboard? Is = there=20 enough to say, shape the exhaust pipe into a nozzle, add an = igniter, and=20 have a home boy's jato, on all the time? If so, how much thrust might = it=20 produce? Just thinking out loud. TP

I think this=20 one is a no-brainer, but my mother often said the same about=20 me...
 
Ernest,
 
Not necessarily.
 
The conventional = wisdom:
 
The Wankel has a higher = exhaust temp=20 because of uncombusted hydrocarbons (due to the flat = combustion=20 chamber) and possibly a lower expansion ratio (depending on which = engine you=20 may be comparing it to). So the Lycoming may make more = power for=20 the same fuel flow with less heat rejection. The Wankel also has a = lot more=20 surface area for the combustion chamber and rotors so the = heat=20 rejected to the coolant will be more. You never get something = for=20 nothing and giving up all those valves, push-rods, lifters, ad=20 nauseum, comes with a price. The price is slightly higher = cooling=20 load and egts.
 
Just to confuse the issue and = tickle some=20 nuerons:
 
Now that is the conventional = wisdom, and if you=20 were to compare the wankel to 4 cyl engine of 1.3 L displacement you = would=20 conclude that the surface area is greater and the bearing area is = greater=20 etc. If you were to compare it to a 3.9 L 6 cyl engine at 2/3 the=20 rpm (which is a much more accurate comparison IMNSHO) you might = find=20 the surface areas and bearing areas are not quite so different after = all. This is like saying that a single cylinder 302 in^3 engine = has=20 less surface area than a V8. DUH!!!. I don't recall anybody at the = drag=20 races with a 302 briggs in their muscle car.
 
So even if you say the frictional = losses are=20 actually fictional losses, the lack of complete combustion and = lower=20 expansion still makes for higher egt and less efficient=20 operation.  
 
From a cooling drag standpoint this = is not=20 good. You have to ingest more air and you have a lower temperature = gradient=20 to work with than with a Lycoming. This is all very academic, but in = practice, I'm not sure it makes a hill of beans. Most aircraft = cooling=20 systems are so far from optimum that you will never get an apples to = apples=20 comparison, plus props, airframes etc are all different. The other = issue is=20 the rotary (normally aspirated fixed pitch) can be run LOP at most = practical=20 power settings without damage. This is not true of the Lycoming. So = this=20 makes up for some of the difference. Now if you have identical = airframes=20 with ideal cooling set ups for both types of engines running LOP at = the same=20 flight condition I think you would find the Lycoming may have a very = slight=20 advantage in BSFC.
 
How much fuel can you buy for the = price of top=20 end overhaul on a 180hp Lycoming? Or for that matter the difference = in the=20 purchase price of the rotary vs. the Lycoming?
 
Monty
 

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