X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from qmta03.westchester.pa.mail.comcast.net ([76.96.62.32] verified) by logan.com (CommuniGate Pro SMTP 6.0.4) with ESMTP id 6220577 for flyrotary@lancaironline.net; Tue, 23 Apr 2013 09:01:57 -0400 Received-SPF: none receiver=logan.com; client-ip=76.96.62.32; envelope-from=gordon@acumen-ea.com Received: from omta19.westchester.pa.mail.comcast.net ([76.96.62.98]) by qmta03.westchester.pa.mail.comcast.net with comcast id TNP11l00827AodY53R1Qry; Tue, 23 Apr 2013 13:01:24 +0000 Received: from HPElitebook ([76.123.51.236]) by omta19.westchester.pa.mail.comcast.net with comcast id TR1Q1l00H55mGuc3fR1QjC; Tue, 23 Apr 2013 13:01:24 +0000 From: "Gordon Alling" To: "'Rotary motors in aircraft'" References: In-Reply-To: Subject: RE: [FlyRotary] Re: Fuel injector pulse frequency Date: Tue, 23 Apr 2013 09:01:22 -0400 Message-ID: <003d01ce4022$a825d340$f87179c0$@com> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_003E_01CE4001.21143340" X-Mailer: Microsoft Office Outlook 12.0 Thread-Index: Ac4+tBZUsI0F0VSRSneZeX+2WGkq6wBblE0w Content-Language: en-us DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=comcast.net; s=q20121106; t=1366722084; bh=2KxWjVZFUxT1cBFFbZ01FLdcKKi6dtdlZkZA4nh5sNU=; h=Received:Received:From:To:Subject:Date:Message-ID:MIME-Version: Content-Type; b=HFzgu2ORJ9j8F6QbxY8MXqBrZKwxxanDeNnUBLUE9j/5g8UMW7M5khx8xYumuqSeS VAAPNrcXAG6KsjrNXrVqC+mBMtbY1natlUJGmWydTK6GUjV0uaPDlw+QyCfVFJXQ03 3n6AEfhM01tp9KscVu56I4u8q6Na2r7jJmhY0zSm7wte3BsT0eFM+pS+NcfrWS2DDg uTeY4DH0S87FhnwQle22XsLUgIETQT9KTLub5BahFCdf4DJ0sc8p7YWalZVKS1u6t6 ztpKxFLtmw4sACsFNnHo77ronRSCyJuImLnSiyHd0X7I5E1xpp5obK5vZI/Yubu7qJ r4Dm+uxxJbtyw== This is a multi-part message in MIME format. ------=_NextPart_000_003E_01CE4001.21143340 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Thanks, Steve. This is really great info. Do you have any info on the range of the injector pulse duration over the RPM range, i.e. min and max pulse duration I can expect? 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 1:18 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Fuel injector pulse frequency Gordon, The traces in the image are for 5000 RPM of the eccentric shaft. For each rotor, there is one combustion event for each revolution of the E-shaft. For manifold pressures less than the staging threshold, there is one primary injector pulse for each rotor for each revolution of the E-shaft. The amount of fuel delivered is determined by the length of that injector pulse, which, in turn, is primarily determined by manifold pressure. With default settings, when the system transitions to manifold pressure just above the staging threshold, the primary and secondary injectors of a given rotor are both pulsed, the pulses occur at the same time, they are of equal duration, and the pulse duration is half of the duration of the single primary injector just below the staging threshold. The other rotor receives the same signals, but offset by 180 degrees of E-shaft rotation. The effect of the injector dead time is most evident at the staging threshold. When the engine is running at a correct mixture at a manifold pressure just below the staging threshold, relatively long pulses to the primary injectors are delivered. When the manifold pressure becomes greater than the staging threshold, the mixture goes lean because the primary and secondary injectors operating at half the pulse duration deliver less fuel than the primary injectors alone at the original pulse duration. This is because the injector dead time is a larger percentage of the injector pulse when the pulse duration is short. It should be emphasized that the forgoing assumes default settings. The problem of the mixture going lean upon transitioning to using both the primary and secondary injectors can be dealt with in several ways. I have found that adjusting mode 6 to achieve the correct mixture just above the staging threshold works best for me even if all the injectors are identical. Adjusting mode 6 changes the pulse duration of both the primary and secondary injectors above the staging threshold and the change is same amount for both the primary and the secondary injectors. This is the behavior of the version of EC2 that I have. It is my understanding that Tracy has incorporated a dead time compensation in the latest versions. As a result, the latest versions may be easier to tune, but this would have no effect on building an independent fuel totalizer based on injector pulse integration. As long as the tuning process has not resulted in changing the injector pulse durations of the injectors of the two rotors (adjusting mode 4) the implication is that fuel flow can be determined by measuring the pulse duration of one primary injector, knowing the RPM, knowing if the secondary injectors are in use or not, and applying a dead time correction. I measured the injector dead time by determining the amount of fuel delivered at different pulse durations and extrapolating a plot of fuel delivered vs. pulse duration to zero fuel delivered. The pulse duration at zero amount of fuel delivered was used as the injector dead time. The dead times of identical models of injectors appears to be very consistent and may sometimes be found in the injector specifications. The flow characteristics of a given injector can be affected by (among other things) system voltage and the difference between the fuel pressure and the manifold pressure. The voltage should be well controlled in a properly operating electrical system, and the difference between the fuel pressure and manifold pressure is generally dealt with by using a manifold pressure compensated fuel pressure regulator such as the stock RX7 regulator. Steve _____ From: Rotary motors in aircraft [flyrotary@lancaironline.net] on behalf of Gordon Alling [gordon@acumen-ea.com] Sent: Sunday, April 21, 2013 7:23 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Fuel injector pulse frequency 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 ------=_NextPart_000_003E_01CE4001.21143340 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

Thanks, Steve.  This is really great = info.  Do you have any info on the range of the injector pulse = duration over the RPM range, i.e. min and max pulse duration I can = expect?

 

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 = 1:18 PM
To: Rotary motors in aircraft
Subject: = [FlyRotary] Re: Fuel injector pulse = frequency

 

= Gordon,

=  

= The traces in the image are for 5000 RPM of the eccentric shaft.  = For each rotor, there is one combustion event for each revolution of the = E-shaft.  For manifold pressures less than the staging threshold, = there is one primary injector pulse for each rotor for each revolution = of the E-shaft.  The amount of fuel delivered is determined by the = length of that injector pulse, which, in turn, is primarily determined = by manifold pressure.  With default settings, when the system = transitions to manifold pressure just above the staging threshold, the = primary and secondary injectors of a given rotor are both pulsed, the = pulses occur at the same time, they are of equal duration, and = the pulse duration is half of the duration of the single = primary injector just below the staging threshold.  The other = rotor receives the same signals, but offset by 180 degrees of = E-shaft rotation.

=  

= The effect of the injector dead time is most evident at the staging = threshold.  When the engine is running at a correct mixture at = a manifold pressure just below the staging threshold, relatively long = pulses to the primary injectors are delivered.  When the = manifold pressure becomes greater than the staging threshold, = the mixture goes lean because the primary and secondary = injectors operating at half the pulse duration deliver less fuel than = the primary injectors alone at the original pulse duration.  This = is because the injector dead time is a larger percentage of the injector = pulse when the pulse duration is short.  It should be = emphasized that the forgoing assumes default = settings.

=  

= The problem of the mixture going lean upon transitioning to = using both the primary and secondary injectors can be dealt with in = several ways.  I have found that adjusting mode 6 to achieve the = correct mixture just above the staging threshold works best for me even = if all the injectors are identical.  Adjusting mode 6 changes = the pulse duration of both the primary and secondary injectors above = the staging threshold and the change is same amount for both the = primary and the secondary injectors.

=  

= This is the behavior of the version of EC2 that I have.  It is = my understanding that Tracy has incorporated a dead time = compensation in the latest versions.  As a result, the latest = versions may be easier to tune, but this would have no effect on = building an independent fuel totalizer based on injector pulse = integration.

=  

= As long as the tuning process has not resulted in changing the = injector pulse durations of the injectors of the two rotors = (adjusting mode 4) the implication is that fuel flow can be determined = by measuring the pulse duration of one primary injector, knowing = the RPM,  knowing if the secondary injectors are in use or = not, and applying a dead time correction.

=  

= I measured the injector dead time by determining the amount of fuel = delivered at different pulse durations and extrapolating a plot of fuel = delivered vs. pulse duration to zero fuel delivered.  The = pulse duration at zero amount of fuel delivered was used as the injector = dead time.  The dead times of identical models of injectors appears = to be very consistent and may sometimes be found in the injector = specifications.  The flow characteristics of a given injector can = be affected by (among other things) system voltage and the difference = between the fuel pressure and the manifold pressure.  The voltage = should be well controlled in a properly operating electrical system, and = the difference between the fuel pressure and manifold pressure is = generally dealt with by using a manifold pressure compensated fuel = pressure regulator such as the stock RX7 = regulator.

=  

= Steve

=  

=   

= From:= Rotary motors in aircraft [flyrotary@lancaironline.net] on behalf of = Gordon Alling [gordon@acumen-ea.com]
Sent: Sunday, April 21, = 2013 7:23 AM
To: Rotary motors in aircraft
Subject: = [FlyRotary] Re: Fuel injector pulse frequency

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

 

 

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