Return-Path: Received: from tomcat.al.noaa.gov ([140.172.240.2] verified) by logan.com (CommuniGate Pro SMTP 4.2b3) with ESMTP id 3229031 for flyrotary@lancaironline.net; Wed, 12 May 2004 13:41:12 -0400 Received: from PILEUS.al.noaa.gov (pileus.al.noaa.gov [140.172.241.195]) by tomcat.al.noaa.gov (8.12.0/8.12.0) with ESMTP id i4CHfBKa003449 for ; Wed, 12 May 2004 11:41:11 -0600 (MDT) Message-Id: <5.2.1.1.0.20040512112440.02504d10@mailsrvr.al.noaa.gov> X-Sender: bdube@mailsrvr.al.noaa.gov X-Mailer: QUALCOMM Windows Eudora Version 5.2.1 Date: Wed, 12 May 2004 11:40:11 -0600 To: "Rotary motors in aircraft" From: Bill Dube Subject: Re: [FlyRotary] Re: Runner Length Was Ref: injector relocation In-Reply-To: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed > > It will be a while before I can prove it, but everything >I know about the process at this point, suggests that Rusty >is on the correct track in moving the injectors down close >to the housings. The effective runner length will be altered by where you do the injection. The speed of sound is reduced by about 10% (perhaps a bit more) when you add the fuel and vaporize it. This would mean that the effective runner length is reduced by about 10% when you do the injection on the upstream end of the runner. This would shift the RPM resonance point upward by about 10%. Who knows? Maybe this is why they mount secondary (high speed) injectors on one end of the runner and the primary injectors on the other. As I understand it, the fuel on the walls does not move around much, but just lays there. The only problem with up-steam injection that I have heard of is throttle response. On abrupt opening, the mixture goes too lean for a moment. On abrupt closing, the mixture goes very rich for a substantial time. If you switched off the up stream injection at some mid-point throttle position, and shifted over to 100% downstream injection, I would guess that the throttle response issues would vanish. Again, just a guess.