X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from smtp1.uwyo.edu ([129.72.10.36] verified) by logan.com (CommuniGate Pro SMTP 6.0.4) with ESMTPS id 6213666 for flyrotary@lancaironline.net; Sun, 21 Apr 2013 13:18:14 -0400 Received-SPF: none receiver=logan.com; client-ip=129.72.10.36; envelope-from=SBoese@uwyo.edu Received: from smtp1.uwyo.edu (localhost [127.0.0.1]) by localhost (Postfix) with SMTP id 84FB122357E for ; Sun, 21 Apr 2013 11:17:38 -0600 (MDT) Received: from ponyexpress-ht5.uwyo.edu (extlb.uwyo.edu [172.26.4.4]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by smtp1.uwyo.edu (Postfix) with ESMTPS id 0E7BC223596 for ; Sun, 21 Apr 2013 11:17:38 -0600 (MDT) Received: from ponyexpress-m10.uwyo.edu ([fe80::60dd:cb9e:6f71:3d48]) by ponyexpress-ht5.uwyo.edu ([fe80::addc:5ab0:b0f8:ab9e%13]) with mapi id 14.02.0318.001; Sun, 21 Apr 2013 11:17:37 -0600 From: "Steven W. Boese" To: Rotary motors in aircraft Subject: RE: [FlyRotary] Re: Fuel injector pulse frequency Thread-Topic: [FlyRotary] Re: Fuel injector pulse frequency Thread-Index: AQHOPpN8x6RBj1zgXk2pMKD4ZajkjZjg1tTr Date: Sun, 21 Apr 2013 17:17:37 +0000 Message-ID: <3E8191F276108F4481AB0721BBA9269E05F9C623@ponyexpress-m10.uwyo.edu> References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [70.196.196.124] Content-Type: multipart/alternative; boundary="_000_3E8191F276108F4481AB0721BBA9269E05F9C623ponyexpressm10u_" MIME-Version: 1.0 --_000_3E8191F276108F4481AB0721BBA9269E05F9C623ponyexpressm10u_ Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable 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. F= or manifold pressures less than the staging threshold, there is one primary= injector pulse for each rotor for each revolution of the E-shaft. The amo= unt of fuel delivered is determined by the length of that injector pulse, w= hich, in turn, is primarily determined by manifold pressure. With default = settings, when the system transitions to manifold pressure just above the s= taging 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 injec= tor just below the staging threshold. The other rotor receives the same si= gnals, but offset by 180 degrees of E-shaft rotation. The effect of the injector dead time is most evident at the staging thresho= ld. When the engine is running at a correct mixture at a manifold pressure= just below the staging threshold, relatively long pulses to the primary in= jectors 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 th= e 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 s= taging threshold works best for me even if all the injectors are identical.= Adjusting mode 6 changes the pulse duration of both the primary and secon= dary injectors above the staging threshold and the change is same amount fo= r both the primary and the secondary injectors. This is the behavior of the version of EC2 that I have. It is my understan= ding that Tracy has incorporated a dead time compensation in the latest ver= sions. As a result, the latest versions may be easier to tune, but this wo= uld have no effect on building an independent fuel totalizer based on injec= tor pulse integration. As long as the tuning process has not resulted in changing the injector pul= se durations of the injectors of the two rotors (adjusting mode 4) the impl= ication is that fuel flow can be determined by measuring the pulse duration= of one primary injector, knowing the RPM, knowing if the secondary inject= ors are in use or not, and applying a dead time correction. I measured the injector dead time by determining the amount of fuel deliver= ed at different pulse durations and extrapolating a plot of fuel delivered = vs. pulse duration to zero fuel delivered. The pulse duration at zero amou= nt 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 someti= mes 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 vo= ltage should be well controlled in a properly operating electrical system, = and the difference between the fuel pressure and manifold pressure is gener= ally dealt with by using a manifold pressure compensated fuel pressure regu= lator 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 t= his group is the willingness of everyone to share their knowledge and exper= ience 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=92s data suggests that I have been working under an incorrect underst= anding of the injection process. Is fuel injected: 1. During a single pulse (per combustion event) with pulse duration d= etermining 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=92s 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 rela= tionship between pulse duration and total flow (perhaps adjusted by manifol= d pressure). Steve, how did you determine injector =93dead time=94? Did y= ou measure it directly or use statistical methods? Do you find this value = to be constant, independent of engine operating parameters, for a given inj= ector or is it variable? If variable, what other parameters do you conside= r? Once again, thanks. Gordon C. Alling, Jr., PE President acumen Engineering/Analysis, Inc. 540-786-2200 www.acumen-ea.com --_000_3E8191F276108F4481AB0721BBA9269E05F9C623ponyexpressm10u_ Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable

Gordon,

 

The traces in the image are for 5000 RPM of the eccentric shaft.  F= or each rotor, there is one combustion event for each revolution of the E-s= haft.  For manifold pressures less than the staging threshold, there i= s 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 primari= ly determined by manifold pressure.  With default settings, when the s= ystem transitions to manifold pressure just above the staging threshold, the primary and secondary injectors of a give= n 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 th= e 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 thre= shold.  When the engine is running at a correct mixture at a mani= fold pressure just below the staging threshold, relatively long pulses to t= he primary injectors are delivered.  When the manifold pressure becomes greater than the staging threshold, the = ;mixture goes lean because the primary and secondary injectors operati= ng 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 p= ulse when the pulse duration is short.  It should be emphasized t= hat the forgoing assumes default settings.

 

The problem of the mixture going lean upon transitioning to us= ing both the primary and secondary injectors can be dealt with in several w= ays.  I have found that adjusting mode 6 to achieve the correct mixtur= e just above the staging threshold works best for me even if all the injectors are identical.  Adjusting mode 6 ch= anges the pulse duration of both the primary and secondary injectors above = the staging threshold and the change is same amount for both the prima= ry 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 tim= e compensation in the latest versions.  As a result, the latest v= ersions may be easier to tune, but this would have no effect on building an independent fuel totalizer based on inject= or pulse integration.

 

As long as the tuning process has not resulted in changing the inje= ctor pulse durations of the injectors of the two rotors (adjusting mod= e 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 de= livered vs. pulse duration to zero fuel delivered.  The pu= lse duration at zero amount of fuel delivered was used as the injector dead time.  The dead times of identical models o= f injectors appears to be very consistent and may sometimes be found in the= injector specifications.  The flow characteristics of a given injecto= r can be affected by (among other things) system voltage and the difference between the fuel pressure and the manifo= ld pressure.  The voltage should be well controlled in a properly oper= ating electrical system, and the difference between the fuel pressure and m= anifold pressure is generally dealt with by using a manifold pressure compensated fuel pressure regulator such as t= he 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.&n= bsp; Thanks.  One of the things I really appreciate about this group i= s 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 o= ne or three injection pulses per revolution?  Is this trace for 5000 o= r 1666 RPM?

 

Steve=92s data sugges= ts that I have been working under an incorrect understanding of the injecti= on 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 a= nd 2?

 

If I read Steve=92s d= ata 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 puls= e duration and total flow (perhaps adjusted by manifold pressure).  Steve, how did you determine injector =93dead= time=94?  Did you measure it directly or use statistical methods?&nbs= p; Do you find this value to be constant, independent of engine operating p= arameters, 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 <= /span>

 

540-786-2200

www.acumen-ea.com

 

 

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