Return-Path: Received: from [24.25.9.103] (HELO ms-smtp-04-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.2b8) with ESMTP id 336406 for flyrotary@lancaironline.net; Tue, 27 Jul 2004 19:46:04 -0400 Received-SPF: error receiver=logan.com; client-ip=24.25.9.103; envelope-from=eanderson@carolina.rr.com Received: from EDWARD (cpe-069-132-183-211.carolina.rr.com [69.132.183.211]) by ms-smtp-04-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id i6RNjUVw015445 for ; Tue, 27 Jul 2004 19:45:32 -0400 (EDT) Message-ID: <001501c47433$f3fc0330$2402a8c0@EDWARD> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Response to Dave's Boost Decay Date: Tue, 27 Jul 2004 19:46:35 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0012_01C47412.6CB82FA0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1409 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1409 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0012_01C47412.6CB82FA0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable RE: [FlyRotary] Dave's Turbo infoDave, see my 0.02 worth in blue below. = At 30 seconds at a time, you still have a ways to go to match my 14 = minutes of rotary glider time {:>) Ed SNIP the bad news. It became very difficult to run lean of peak with the=20 lack of an automatic waste gate actuator. Since boost is very dependant = on=20 RPM, even the small of pitch changes required to maintain level flight=20 caused enough variation in RPM to significantly change the boost - i.e. = slow=20 down just a little, boost drops, less RPM, less boost etc.. and in about = a=20 second the engine quits running. Slightly increasing the mixture is not=20 enough to get it back as by then the RPM s have really dropped. It = usually=20 took a significant increase in mixture to start the engine again. = I'm even=20 starting to get used to the sensation of my engine stopping (watch = out Ed,=20 I'm gaining on you in glider time).=20 I think, Dave, you are once again pointing out the risks and = difficulty in trying to maintain boost control through throttle control = alone. Here is what I think what may be happening - a rapid feed back = situation. Without the boost gate and using manual throttle control you = have no "reserve" of exhaust mass flow. In other words, with a waste = gate you could be dumping say 10% of your exhaust mass through the gate. = So a slight variation in exhaust mass flow caused by varying the = aircraft attitude (and rpm) could be handled by the wastegate system = without your knowledge. As the massflow started to slow, it simply = stopped dumping as much (or any) through the gate. This kept your boost = stable and therefore the air/fuel mixture control could be leaned (you = would loose some mass flow - but hey! you were dumping 10% of it in any = case).=20 Now you disable the waste gate and go to manual control of boost by = the throttle. Here YOU must adjust the throttle and mixture control = precisely and exactly to maintain X level of boost. There is no exhaust = mass flow reserve like you had with the waste gate. You are exactly at = the state where throttle and mixture produce X psi boost. Now, the = attitude of the aircraft changes causing the engine rpm to drop = slightly, this results in less mass flow - but now you have no reserve = mass flow. Mass flow drops, turbine wheel slows, boost drops, manifold = pressure decreases all of this results in even less mass flow which = causes more boost drop, etc.,etc. A feed back situation that can = quickly cascade into power decay rapidly when using manual throttle = control.=20 I am not certain why the fuel mixture gets out of whack. I would = think if you waited long enough (30 sec?) the system would stabilize and = the E2 catch up with the current state and everything would start = running again. I suspect that under boost the EC2 is of course = providing gobs of fuel to go along with the high air mass flow = (represented by high RPM and BOOST). Suddenly it finds the the boost = all gone or greatly decreased, in fact without the boost the manifold = pressure may plummet very sharply. The EC2 may simply in effect shut = off the fuel flow due to this rapid decrease (same effect as if you had = closed the throttle quickly). =20 Tracy, of course, would be the one to ask. This is just my 0.02 = worth Ed Anderson David Leonard=20 The Rotary Roster=20 http://members.aol.com\_ht_a\rotaryroster\index.html=20 << File: ATT1916502.txt >>=20 ------=_NextPart_000_0012_01C47412.6CB82FA0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable RE: [FlyRotary] Dave's Turbo info
Dave, see my 0.02 worth in blue = below.  At 30=20 seconds at a time, you still have a ways to go to match my 14 minutes of = rotary=20 glider time {:>)
 
Ed
 
SNIP
 
 
 the bad = news.  It=20 became very difficult to run lean of peak with the=20
lack of an automatic = waste gate=20 actuator.  Since boost is very dependant on
RPM, even the small of pitch = changes required=20 to maintain level flight
caused enough variation in RPM to significantly change the = boost - i.e.=20 slow
down just a=20 little, boost drops, less RPM, less boost etc.. and in about = a=20
second the engine = quits=20 running.

     

      Slightly = increasing the=20 mixture is not
    enough to get it back as by then the RPM s have really = dropped. =20 It usually
    took a=20 significant increase in mixture to start the engine again.  I'm = even
    starting to=20 get used to the sensation of my engine stopping (watch out = Ed,=20
    I'm gaining on = you in glider=20 time). 

    I=20 think, Dave, you are once again pointing out the risks and = difficulty in=20 trying to maintain boost control through throttle=20 control alone.

     =20 Here is what I think what may be happening -  a rapid feed = back=20 situation. Without the boost gate and using manual throttle = control=20  you have no "reserve" of exhaust mass flow.  In other = words, with=20 a waste gate you could be dumping say 10% of your exhaust mass = through the=20 gate.  So   a slight variation in exhaust mass flow = caused by=20 varying the aircraft attitude (and rpm)  could be handled by = the=20 wastegate system without your knowledge.  As the massflow = started to=20 slow, it simply stopped dumping as much (or any) through the = gate. =20 This kept your boost stable and therefore the air/fuel mixture = control could=20 be leaned (you would loose some mass flow - but hey! you were = dumping 10% of=20 it in any case).

    Now you=20 disable the waste gate and go to manual control of boost by the=20 throttle.  Here YOU must adjust the throttle and mixture = control=20 precisely and exactly to maintain X level of boost.  There = is no=20 exhaust mass flow reserve like you had with the waste gate.  = You are=20 exactly at the state where throttle and mixture produce X psi = boost. =20 Now,  the attitude of the aircraft changes causing the = engine rpm=20 to drop slightly, this results in less mass flow - but now you have = no=20 reserve mass flow.  Mass flow drops, turbine wheel slows, boost = drops,=20 manifold pressure decreases all of this results in even less mass = flow which=20 causes more boost drop, etc.,etc.  A feed back situation that = can=20 quickly cascade into power decay rapidly when using manual throttle=20 control. 

    I am not=20 certain why the fuel mixture gets out of whack. I would think = if you=20 waited long enough (30 sec?) the system would stabilize and the E2 = catch up=20 with the current state and everything would start running = again.  I=20 suspect that under boost the EC2 is of course providing gobs of fuel = to go=20 along with the high air mass flow (represented by high RPM and = BOOST). =20 Suddenly it finds the the boost all gone or greatly decreased, in = fact=20 without the boost the manifold pressure may plummet very = sharply.  The=20 EC2 may simply in effect shut off the fuel flow due to this rapid = decrease=20 (same effect as if you had closed the throttle quickly). =20

    Tracy, of=20 course, would be the one to ask.  This is just my 0.02=20 worth

     

    Ed=20 Anderson

     David Leonard
    The Rotary Roster
    http://memb= ers.aol.com\_ht_a\rotaryroster\index.html=20
     << = File:=20 ATT1916502.txt >> =

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