Return-Path: Received: from fed1rmmtao06.cox.net ([68.230.241.33] verified) by logan.com (CommuniGate Pro SMTP 4.2b8) with ESMTP id 337182 for flyrotary@lancaironline.net; Wed, 28 Jul 2004 15:13:14 -0400 Received-SPF: error receiver=logan.com; client-ip=68.230.241.33; envelope-from=daveleonard@cox.net Received: from davidandanne ([68.111.224.107]) by fed1rmmtao06.cox.net (InterMail vM.6.01.03.02.01 201-2131-111-104-103-20040709) with SMTP id <20040728191241.DLTM6135.fed1rmmtao06.cox.net@davidandanne> for ; Wed, 28 Jul 2004 15:12:41 -0400 From: "DaveLeonard" To: "Rotary motors in aircraft" Subject: RE: [FlyRotary] Response to Dave's Boost Decay Date: Wed, 28 Jul 2004 12:12:49 -0700 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0082_01C4749C.332290C0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2910.0) X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 In-Reply-To: Importance: Normal This is a multi-part message in MIME format. ------=_NextPart_000_0082_01C4749C.332290C0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit RE: [FlyRotary] Dave's Turbo infoEd, you are exactly right about what is going on. I just felt my e-mail was long enough as it was. You are also right that it would probably eventually start running again as soon as everything settled out (I lost enough airspeed). The same thing happens if I am running lean and close the throttle some. Maybe it could be improved with better programming, but I just can't seem to perfect THAT art. Dave Leonard Dave, 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 lack of an automatic waste gate actuator. Since boost is very dependant on RPM, even the small of pitch changes required to maintain level flight caused enough variation in RPM to significantly change the boost - i.e. slow down just a little, boost drops, less RPM, less boost etc.. and in about a second the engine quits running. Slightly increasing the mixture is not enough to get it back as by then the RPM s have really dropped. It usually took a significant increase in mixture to start the engine again. I'm even starting to get used to the sensation of my engine stopping (watch out Ed, I'm gaining on you in glider time). 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). 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. 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). Tracy, of course, would be the one to ask. This is just my 0.02 worth Ed Anderson David Leonard The Rotary Roster http://members.aol.com\_ht_a\rotaryroster\index.html << File: ATT1916502.txt >> ------=_NextPart_000_0082_01C4749C.332290C0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable RE: [FlyRotary] Dave's Turbo info
Ed, = you are exactly=20 right about what is going on.  I just felt my e-mail was long = enough as it=20 was.
 
You = are also right=20 that it would probably eventually start running again as soon as = everything=20 settled out (I lost enough airspeed).  The same thing happens if I = am=20 running lean and close the throttle some.   Maybe it could be = improved=20 with better programming, but I just can't seem to perfect THAT=20 art.
 
Dave=20 Leonard
Dave, see my 0.02 worth in blue = below.  At=20 30 seconds at a time, you still have a ways to go to match my 14 = minutes of=20 rotary glider time {:>)
 
Ed
 
SNIP
 
 
 the = bad news. =20 It 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=20 required to maintain level flight
caused enough variation in RPM to significantly = change the=20 boost - i.e. slow
down just a little, boost drops, less RPM, less boost etc.. = and in=20 about a
second the=20 engine quits running.

     

      Slightly = increasing the=20 mixture is not
    enough to get it back as by then the RPM s have really=20 dropped.  It usually
    took a significant increase in mixture to = start the=20 engine again.  I'm even
    starting to get used to the sensation of my = engine=20 stopping (watch out Ed,
    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,=20 with a waste gate you could be dumping say 10% of your exhaust = mass=20 through the gate.  So   a slight variation in = exhaust mass=20 flow caused by varying the aircraft attitude (and rpm)  could = be=20 handled by the wastegate system without your knowledge.  As = the=20 massflow started to slow, it simply stopped dumping as much (or = any)=20 through the gate.  This kept your boost stable and therefore = the=20 air/fuel mixture control could be leaned (you would loose some = mass flow -=20 but hey! you were dumping 10% of it in any case).=20

    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=20 rpm 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=20 drops, manifold pressure decreases all of this results in even = less mass=20 flow which causes more boost drop, etc.,etc.  A feed back = situation=20 that can quickly cascade into power decay rapidly when using = manual=20 throttle 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=20 up with the current state and everything would start running = again. =20 I suspect that under boost the EC2 is of course providing gobs of = fuel to=20 go along with the high air mass flow (represented by high RPM and=20 BOOST).  Suddenly it finds the the boost all gone or greatly=20 decreased, in fact without the boost the manifold pressure may = plummet=20 very sharply.  The EC2 may simply in effect shut off the fuel = flow=20 due to this rapid decrease (same effect as if you had closed the = throttle=20 quickly). 

    Tracy,=20 of 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 >>=20

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