X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-lb0-f170.google.com ([209.85.217.170] verified) by logan.com (CommuniGate Pro SMTP 6.0.5) with ESMTPS id 6376230 for flyrotary@lancaironline.net; Wed, 17 Jul 2013 04:46:18 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.217.170; envelope-from=wdleonard@gmail.com Received: by mail-lb0-f170.google.com with SMTP id t13so1340299lbd.29 for ; Wed, 17 Jul 2013 01:45:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=UlcgYmGzF8na2A8PbJKQ8ysohl5HBw0dCHInNo8n0Lc=; b=OUenZlLIYAQ/QZmWD/eY96jcKzKg/C9EVxeW/rh4HTMpY1n5s1Ue4q+XX7i6fzswqq TMczldP0uv0wdwlineyI6KdnYelNpXmgvGTO948ToA95mkvr7A+PRbhkXgY00YcHJxzT omdBvgVMv2GfUv70/Db6yYm9IAmeo2xeS4trMeOtPTdSR2RktGzZfw6ut0h9JMESqyVy MZjTbn8MOvM7F2ts+QZaXHY4m+uGRh9GCxCiTShr8PWVp7xZeBMUepVdptVtpabgQZUj 5RkEwm434wYMnlTxOUbA31+73skANx9hE0txBj7NZjAGa2YXhr5RQLIXZW59f0jgQw3N oSQA== MIME-Version: 1.0 X-Received: by 10.152.87.101 with SMTP id w5mr2265134laz.48.1374050741200; Wed, 17 Jul 2013 01:45:41 -0700 (PDT) Received: by 10.112.60.70 with HTTP; Wed, 17 Jul 2013 01:45:41 -0700 (PDT) In-Reply-To: References: Date: Wed, 17 Jul 2013 01:45:41 -0700 Message-ID: Subject: Fwd: [FlyRotary] Re: Turbo Selection Workbook- Rev1 From: David Leonard To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=001a11c345c855298504e1b11eaf --001a11c345c855298504e1b11eaf Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable Bobby, now you are mixing supercharger info with turbocharger stuff which may confuse things a little. But here are some comments. My appoligies that I do not know what airframe, engine, boost method and goals you have, so the following comments just apply to my situation with a 13B turbo in an RV-6 with goals of a one-off race at Reno and otherwise keep up with 200+ h.p. formation buddies in other RV's. Dave,**** > > ** ** > > With the super charger I typically cruise with engine rpm=92s between 485= 0 > and 5400 set with the prop controller. > I have a fixed pitch prop so RPM varies much more widely. I see 5200 or so on climb out and 5400 to 6000 depending on how fast I want to cruise. I saw 7500 when racing at Reno. It is important to note that variation of mass flow will help keep away from the surge line. If you look at compressor map, as the pressure ratio goes up (the vertical axis) the mass flow through the turbo needs to go up to keep away from the surge line. With your C/S prop and lower RPM, you are using higher boost (higher A/R) without increasing the mass flow through the compressor as much as if the RPM were increasing. So, for a given horse-power output of the engine the mass flow is relatively fixed (i.e. air mass=3Doxygen mass=3Dfuel mass burned=3Dh.p). However, the pressure ratio will be lower if the engine is turning faster at a lower MP to achieve the same power output. This is more likely to prevent surge as you have noted. > Cruise climb around 5800-6200. Throttle Body is wide open and MP > controlled with a vernier cable to the super charger bypass. Applying the= se > settings to the published turbo compressor maps puts me outside the surge > line at low engine rpm and high altitude. > Yup. It is OK to run your rotary much faster than that. Maybe the prop cant turn that fast? Higher alititude always moves toward the surge issue because the pressure ratio is going up while the mass flow is not. Automotive turbochargers were built for sea level. The aircraft turbocharger makers dont seem to give up the data as readily. > Several things could be done to move the pressure ratio lower. Run higher > rpm at altitudes above 15K, > Yes, as above, I recommend that. > use a ram air inlet to eliminate and boost air pressure at the turbo > inlet or use an intercooler with a lower pressure drop. > You are likely to get minimal improvement from either of those because it is so hard to change things much (how much lower do you think you can get pressure drop?), but every little bit helps. > I have not been able to find compressor maps that compare different > turbine A/R=92s for the same compressor components. > Again, the compressor map is INDEPENDENT of the the turbine A/R. And by turbine, I mean the part that is in the exhaust. The part that is in the intake is the compressor (even in a supercharger even though it is a turbine too, and the only turbine in a supercharger system) > My concern would be using a .96 or 1.0 A/R and moving further toward the > surge line. That may not be the case. > If we have our terms right, increasing the size of the turbine A/R has no effect on surge whatsoever. We want large a/r's in aircraft use to minimize back pressure and reduce risk of compressor over speed at altitude (which did in my first turbocharger). My compressor is a T04H while my turbine is a T04 trimmed down and stuffed inside a stock turbine housing with a miserably small A/R and a stock waste gate. I happens to works very for my particular goals, though there is much improvement to be had if loftier goals were in mind. So for you to figure out which compressor you need, look not to A/R, but the mass flow A/R caluclator the input your goals and find a compressor that works. I am sorry that I have not looked at the one you sent out, but here is the one I sent out years ago. Hope it helps, Dave Leonard -- Turbo Rotary RV-6 N4VY http://N4VY.RotaryRoster.net http://RotaryRoster.net --001a11c345c855298504e1b11eaf Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable

Bobby, now= you are mixing supercharger info with turbocharger stuff which may confuse= things a little. =A0But here are some comments. =A0My appoligies that I do= not know what airframe, engine, boost method =A0and goals you have, so the= following comments just apply to my situation with a 13B turbo in an RV-6 = with goals of a one-off race at Reno and otherwise keep up with 200+ h.p. f= ormation buddies in other RV's.



Dave,

=A0

With the super charger I typically cruise wit= h engine rpm=92s between 4850 and 5400 set with the prop controller.=


I have a fixed pitch pro= p so RPM varies much more widely. =A0I see 5200 or so on climb out and 5400= to 6000 depending on how fast I want to cruise. =A0I saw 7500 when racing = at Reno. =A0

It is important to note that variation of mass flow wil= l help keep away from the surge line. =A0If you look at compressor map, as = the pressure ratio goes up (the vertical axis) the mass flow through the tu= rbo needs to go up to keep away from the surge line. =A0With your C/S prop = and lower RPM, you are using higher boost (higher A/R) without increasing t= he mass flow through the compressor as much as if the RPM were increasing.<= /div>

So, for a given horse-power output of the engine the ma= ss flow is relatively fixed (i.e. air mass=3Doxygen mass=3Dfuel mass burned= =3Dh.p). =A0However, the pressure ratio will be lower if the engine is turn= ing faster at a lower MP to achieve the same power output. =A0This is more = likely to prevent surge as you have noted.
=A0

Cruise climb around 5800-6200. Throttle Body is wide open and MP controll= ed with a vernier cable to the super charger bypass. Applying these setting= s to the published turbo compressor maps puts me outside the surge line at = low engine rpm and high altitude.


Yup. =A0It is OK to run = your rotary much faster than that. =A0Maybe the prop cant turn that fast? = =A0Higher alititude always moves toward the surge issue because the pressur= e ratio is going up while the mass flow is not. =A0Automotive turbochargers= were built for sea level. =A0The aircraft turbocharger makers dont seem to= give up the data as readily.
=A0

Several things could be done to move the pressure ratio lower. Run higher = rpm at altitudes above 15K,


Yes, as above, I recomme= nd that.
=A0

use a ram air inlet= to eliminate and boost air pressure at the turbo inlet or use an intercool= er with a lower pressure drop.


You are likely to get mi= nimal improvement from either of those because it is so hard to change thin= gs much (how much lower do you think you can get pressure drop?), but every= little bit helps.
=A0

=A0I have not been able to find compressor maps that compare different tu= rbine A/R=92s for the same compressor components.


Again, the compressor ma= p is INDEPENDENT of the the turbine A/R. =A0And by turbine, I mean the part= that is in the exhaust. =A0The part that is in the intake is the compresso= r (even in a supercharger even though it is a turbine too, and the only tur= bine in a supercharger system)
=A0

My concern would be using a .96 or 1.0 A/R and moving further toward the s= urge line. That may not be the case.


If we have our terms rig= ht, increasing the size of the turbine A/R has no effect on surge whatsoeve= r. =A0We want large a/r's in aircraft use to minimize back pressure and= reduce risk of compressor over speed at altitude (which did in my first tu= rbocharger).

My compressor is a T04H while my turbine is a T04 trimm= ed down and stuffed inside a stock turbine housing with a miserably small A= /R and a stock waste gate. =A0I happens to works very for my particular goa= ls, though there is much improvement to be had if loftier goals were in min= d.

So for you to figure out which compressor you need, loo= k not to A/R, but the mass flow A/R caluclator the input your goals and fin= d a compressor that works. =A0I am sorry that I have not looked at the one = you sent out, but here is the one I sent out years ago.

Hope it helps,

Dave Leonard
=A0
--
Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net
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