X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from tomcat.al.noaa.gov ([140.172.240.2] verified) by logan.com (CommuniGate Pro SMTP 4.3.5) with ESMTP id 1024767 for flyrotary@lancaironline.net; Tue, 28 Jun 2005 11:39:12 -0400 Received-SPF: none receiver=logan.com; client-ip=140.172.240.2; envelope-from=bdube@al.noaa.gov Received: from mungo.al.noaa.gov (mungo.al.noaa.gov [140.172.241.126]) by tomcat.al.noaa.gov (8.12.11/8.12.0) with ESMTP id j5SFcSnB029686 for ; Tue, 28 Jun 2005 09:38:28 -0600 (MDT) Message-Id: <6.2.1.2.0.20050628091806.0377a168@mailsrvr.al.noaa.gov> X-Mailer: QUALCOMM Windows Eudora Version 6.2.1.2 Date: Tue, 28 Jun 2005 09:37:16 -0600 To: "Rotary motors in aircraft" From: Bill Dube Subject: Re: [FlyRotary] Re: NPG + use in aircraft?? In-Reply-To: References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed At 11:58 PM 6/27/2005, you wrote: > Al >What I meant was due to the high boiling point of PG it would protect >against"film" boiling which causes pre-ignition. I don't think so. The higher boiling point would raise the temperature of the hot spot. This is not likely to impede film boiling. It takes a fairly stout heat source (and a big temperature difference) to get film boiling in plain water. Raising the boiling point would only make a difference if you were very close to the transition and everything else stayed the same. The higher viscosity of NPG would tend to impede convective cooling (as well as forced convection) which would promote localized film boiling. The lower specific heat and heat of vaporization for NPG would make it much more prone to film boiling as well. Looking at the numbers, it seems to me that if you have film boiling problem using water, you are going to be much worse off using NPG. Bill Dube'