X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from qmta10.westchester.pa.mail.comcast.net ([76.96.62.17] verified) by logan.com (CommuniGate Pro SMTP 6.0.4) with ESMTP id 6213432 for flyrotary@lancaironline.net; Sun, 21 Apr 2013 09:23:56 -0400 Received-SPF: none receiver=logan.com; client-ip=76.96.62.17; envelope-from=gordon@acumen-ea.com Received: from omta18.westchester.pa.mail.comcast.net ([76.96.62.90]) by qmta10.westchester.pa.mail.comcast.net with comcast id SdNF1l0011wpRvQ5AdPMA7; Sun, 21 Apr 2013 13:23:21 +0000 Received: from HPElitebook ([76.123.51.236]) by omta18.westchester.pa.mail.comcast.net with comcast id SdPM1l00A55mGuc3edPMsQ; Sun, 21 Apr 2013 13:23:21 +0000 From: "Gordon Alling" To: "'Rotary motors in aircraft'" References: In-Reply-To: Subject: RE: [FlyRotary] Re: Fuel injector pulse frequency Date: Sun, 21 Apr 2013 09:23:21 -0400 Message-ID: <001e01ce3e93$650034b0$2f009e10$@com> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001F_01CE3E71.DDEE94B0" X-Mailer: Microsoft Office Outlook 12.0 Thread-Index: Ac4+WtMahlwDaJICQ5++Dw1IG3wBUgANCz/Q Content-Language: en-us DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=comcast.net; s=q20121106; t=1366550601; bh=H+qSySYwLzjXatH3DhiL3qoNhSxigKkCymeJ9tsgVDw=; h=Received:Received:From:To:Subject:Date:Message-ID:MIME-Version: Content-Type; b=je7f2H0ydGhpxqdrIBgSeRGJiwo7VNnWJ63TqKtfCR/J2DehiivMVuLT/2Ys6sjVg 8l3fVIrLaYq05uN89v2007WoNQTsf/qL3mG/r2ZF3O868zgTxnMuJV4m+7GeDwVpa9 bfHziVOiAq8+wnv4Vg6JIKZ/Q0IYUg7zFq+0JRC57AsjjVi5vrwiVeunFvq/0YARfR l20iKyUGCiVOO+N6ZYxaOdWk+vZyllTUcOZ7xouFMY6vwUJ0Cf3T8x9Lre1HRvcMIv vWnOyOME33iD0ABXXNHG8/+XdxrcF7CKutSnFK1hZYs1nWLM1DbHwxBMVFMI8fY5VO glZf57AwtbB8A== This is a multi-part message in MIME format. ------=_NextPart_000_001F_01CE3E71.DDEE94B0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit This is great info. Thanks. One of the things I really appreciate about this group is the willingness of everyone to share their knowledge and experience with those of us who are not so knowledgeable and experienced. Steve, should I see one or three injection pulses per revolution? Is this trace for 5000 or 1666 RPM? Steve's data suggests that I have been working under an incorrect understanding of the injection process. Is fuel injected: 1. During a single pulse (per combustion event) with pulse duration determining fuel delivery, or 2. During multiple (fixed duration) pulses per combustion event with the number of pulses determining fuel quantity delivered, or 3. Some combination of 1 and 2? If I read Steve's data correctly, No 1 is the case and a fuel totalizer/ flow rate instrument could be based on a look-up table or a functional relationship between pulse duration and total flow (perhaps adjusted by manifold pressure). Steve, how did you determine injector "dead time"? Did you measure it directly or use statistical methods? Do you find this value to be constant, independent of engine operating parameters, for a given injector or is it variable? If variable, what other parameters do you consider? Once again, thanks. Gordon C. Alling, Jr., PE President acumen Engineering/Analysis, Inc. 540-786-2200 www.acumen-ea.com From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Steven W. Boese Sent: Sunday, April 21, 2013 2:39 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Fuel injector pulse frequency Gordon, The attached image shows signals generated by an EC2 for a 13B engine at 5000 RPM. The signals are identified by color in the legend at the right of the image. Like Ed, I have built fuel totalizing and flow rate instruments based on discrete counter IC's and based on a microprocessor. The unit based on discrete counters was accurate only under the conditions at which the calibration was made. The reason for this is the effect of the dead time of the injector preventing a simple correlation of the length of an injector pulse with the amount of fuel delivered during that pulse when the length of the pulse is variable. Since the aviation application often involved operation at the conditions used for calibration, this limitation was not often very significant. The system using the microprocessor enabled the accurate calculation of the amount of fuel delivered by each pulse at any injector pulse length by taking into account the injector dead time. The injector dead time was determined for the injectors used and its value was part of the programming. The microprocessor version uses inputs from the primary and secondary injectors and displays the RPM, fuel flow rate, and the amount of fuel remaining in each tank since I have a duplex fuel valve with a switch telling the microprocessor which tank is in use. I chose to use the Texas Instruments Launchpad development system which cost about $5 and included two microprocessors. Of course, other components were required for the final unit, the most expensive part being the display. Steve Boese RV6A, 1986 13B NA, RD1A, EC2 ------=_NextPart_000_001F_01CE3E71.DDEE94B0 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

This is great info.  Thanks.  One of = the things I really appreciate about this group is the willingness of = everyone to share their knowledge and experience with those of us who = are not so knowledgeable and experienced.

 

Steve, should I see one = or three injection pulses per revolution?  Is this trace for 5000 = or 1666 RPM?

 

Steve’s data = suggests that I have been working under an incorrect understanding of = the injection process.  Is fuel injected:

 

1.       = During a = single pulse (per combustion event) with pulse duration determining fuel = delivery, or

2.       = During = multiple (fixed duration) pulses per combustion event with the number of = pulses determining fuel quantity delivered, or

3.       = Some = combination of 1 and 2?

 

If I read Steve’s = data correctly, No 1 is the case and a fuel totalizer/ flow rate = instrument could be based on a look-up table or a functional = relationship between pulse duration and total flow (perhaps adjusted by = manifold pressure).  Steve, how did you determine injector = “dead time”?  Did you measure it directly or use = statistical methods?  Do you find this value to be constant, = independent of engine operating parameters, for a given injector or is = it variable?  If variable, what other parameters do you = consider?

 

Once again, = thanks.

 

Gordon C. Alling, Jr., = PE

President

a= cumen Engineering/Analys= is, Inc.

 

540-786-2200

www.acumen-ea.com

 

From:= = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On = Behalf Of Steven W. Boese
Sent: Sunday, April 21, 2013 = 2:39 AM
To: Rotary motors in aircraft
Subject: = [FlyRotary] Re: Fuel injector pulse = frequency

 

= Gordon,

= The attached image shows signals generated by an EC2 for a 13B engine at = 5000 RPM. The signals are identified by color in the legend at the right = of the image.

= Like Ed, I have built fuel totalizing and flow rate instruments based on = discrete counter IC's and based on a microprocessor. The unit based on = discrete counters was accurate only under the conditions at which the = calibration was made. The reason for this is the effect of the dead time = of the injector preventing a simple correlation of the length of an = injector pulse with the amount of fuel delivered during that pulse when = the length of the pulse is variable. Since the aviation application = often involved operation at the conditions used for calibration, this = limitation was not often very significant.

= The system using the microprocessor enabled the accurate calculation of = the amount of fuel delivered by each pulse at any injector pulse = length by taking into account the injector dead time. The injector = dead time was determined for the injectors used and its value was part = of the programming. The microprocessor version uses inputs from the = primary and secondary injectors and displays the RPM, fuel flow rate, = and the amount of fuel remaining in each tank since I have a duplex fuel = valve with a switch telling the microprocessor which tank is in use. I = chose to use the Texas Instruments Launchpad development system which = cost about $5 and included two microprocessors.  Of course, other = components were required for the final unit, the most expensive part = being the display.

= Steve Boese

= RV6A, 1986 13B NA, RD1A, = EC2

 

 

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