X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from lrcmmta07-srv.windstream.net ([166.102.165.79] verified) by logan.com (CommuniGate Pro SMTP 5.2.16) with ESMTP id 3902869 for flyrotary@lancaironline.net; Wed, 28 Oct 2009 12:50:35 -0400 Received-SPF: pass receiver=logan.com; client-ip=166.102.165.79; envelope-from=montyr2157@windstream.net Return-Path: X-WS-COS: WSOB804 X-Cloudmark-Category: Undefined:Undefined X-Cloudmark-Analysis: v=1.1 cv=vSMLmrFS1nYbGB8bmKetT7weF86tdH00ck38nwnLmhA= c=1 sm=0 a=Ia-xEzejAAAA:8 a=oCcaPWc0AAAA:8 a=cQ-VcKmo8BBkLH5cQYEA:9 a=ycVjKMAxWODjuWI5bw8A:7 a=gnQQ7IFc0G2hkryJ75d94oSOGzIA:4 a=EzXvWhQp4_cA:10 a=KQbsVwFWXtjXAk3h:21 a=gRkbBN_GheTObZpJ:21 a=kviXuzpPAAAA:8 a=P-XWJoVZ3-uIEgBb6OMA:9 a=GoZz0oykIXXqGaqiqz8A:7 a=VnAngZ3iKzQ610Nw6bv6_S61VakA:4 a=d-1ze5jHbJEA:10 a=4vB-4DCPJfMA:10 a=vpO2y-IJJba-wKqd:21 a=N7qAfzLTu8aYuZsn:21 a=RStpfhDVw1if3x2Z5oZ2Ow==:117 X-Cloudmark-Score: 0 Authentication-Results: lrcmmta07 smtp.user=montyr2157; auth=pass (LOGIN) Received: from [98.20.149.107] ([98.20.149.107:60599] helo=newbox) by lrcmmta07 (envelope-from ) (ecelerity 2.2.2.43 r()) with ESMTPA id 37/B7-25656-63678EA4; Wed, 28 Oct 2009 11:49:59 -0500 Message-ID: From: "MONTY ROBERTS" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Prop Loads Date: Wed, 28 Oct 2009 11:49:48 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0014_01CA57C4.C0039FF0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5843 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 This is a multi-part message in MIME format. ------=_NextPart_000_0014_01CA57C4.C0039FF0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Greg et Al, ;-) =20 Being nothing more than a big fan a prop roughly follows the fan laws. Flow varies directly with RPM Pressure varies with the square of RPM Power varies with the cube of RPM I say roughly because a prop is not a "perfect fluid machine" and = therefore these rules do not apply when the prop is stalled or when the = tips start to go transonic. The efficiency of the blades also changes = with varying Re Number so this affects things a bit. This also only = applies to fixed pitch props. Tune the engine on the dyno, the dyno operator should know how. Develop = your fuel map for that. Then select your prop to absorb the desired hp = at the desired rpm based on the dyno runs and your airframe performance = and flight level. Fine tune in flight. Airplanes are different because of the vast range of air density = encountered in operation. Short of a air brake dyno in an altitude = chamber, you are going to have to live with this.=20 In an airplane with a fixed pitch prop, the engine will never see full = SL power, unless you use a climb prop and fly lower than 1000 ft all the = time towing banners at WOT. The prop will limit power output for takeoff = and climb. By the time the airplane is flying fast enough to absorb full = power in level flight, you will be at 75% of 75% SL WOT power and a low = air density. Typically operating at about a 50% or less duty cycle = compared to WOT SL performance. Boats at SL are much harder on engines = than airplanes.=20 If you have a turbo, and a CS prop, none of this really applies and you = are going to have a thermodynamic adventure. YMMV Monty ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Wednesday, October 28, 2009 11:56 AM Subject: [FlyRotary] Re: Prop Loads Greg; I had the same dilemma when running my engine on the dyno. The primary reason I wanted to simulate a prop load so I could do = tuning of the EC2 on the dyno. But that never happened. I generated an = approximate prop load curve but could never follow it - IIRC, it was = because you can't set the load, and there is more than one RPM/MAP = combination for a given load. Dyno work is basically about generating = WOT HP and torque curves. You set the mixture according to the A/F = ratio. And you always learn some other things along the way - flow = rates, EGTs, fuel burn, etc. And Gary, I don't think prop load varies as the square of the rpm - = does it? I think some aspects, like thrust, go as the square; but the = drag goes more like the cube. I generated one both ways, and neither is = the real world. Al G -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] = On Behalf Of Greg Ward Sent: Tuesday, October 27, 2009 6:43 PM To: Rotary motors in aircraft Subject: [FlyRotary] Prop Loads Hey Troops; Finally in the dyno room building the mount plate to begin testing. = Tracy says that the engine should be tested with the prop on, and this = is kind of hard in a dyno room. We are mounting the engine without the = PSRU, so that we don't tear it up in testing, and instead hooking = directly to the shaft which is loaded by means of a water brake. We can = put any load on it that we want, problem is, how to calculate that prop = load in foot-pounds, at different settings. Talked to Craig Cato, and = he is leaving for Europe, so doesn't have time to run the calcs, and I = am just a dumb high country nail-banger. Any thoughts? Greg Ward Lancair 20B N178RG in progress -------------------------------------------------------------------------= ----- No virus found in this incoming message. Checked by AVG - www.avg.com=20 Version: 8.5.423 / Virus Database: 270.14.36/2465 - Release Date: = 10/28/09 09:34:00 ------=_NextPart_000_0014_01CA57C4.C0039FF0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Greg et Al, ;-)
 
Being nothing more than a big fan a = prop roughly=20 follows the fan laws.
 
Flow varies directly with = RPM
Pressure varies with the square of = RPM
Power varies with the cube of = RPM
 
I say roughly because a prop is not a = "perfect=20 fluid machine" and therefore these rules do not apply when the = prop is=20 stalled or when the tips start to go transonic. The efficiency of the = blades=20 also changes with varying Re Number so this affects things a bit.=20 This also only applies to fixed pitch = props.
 
Tune the engine on the dyno, the dyno = operator=20 should know how. Develop your fuel map for that. Then select your prop = to absorb=20 the desired hp at the desired rpm based on the dyno runs and your = airframe=20 performance and flight level. Fine tune in flight.
 
Airplanes are different because of the = vast range=20 of air density encountered in operation. Short of a air = brake dyno in=20 an altitude chamber, you are going to have to live with this. =
 
In an airplane with a fixed pitch = prop, the=20 engine will never see full SL power, unless you use a climb prop and fly = lower=20 than 1000 ft all the time towing banners at WOT. The prop will limit = power=20 output for takeoff and climb. By the time the airplane is flying = fast=20 enough to absorb full power in level flight, you will be at 75% of = 75% SL=20 WOT power and a low air density. Typically operating at about a 50% = or less=20 duty cycle compared to WOT SL performance. Boats at SL are = much harder=20 on engines than airplanes. 
 
If you have a turbo, and a CS prop, = none of this=20 really applies and you are going to have a thermodynamic = adventure.
 
YMMV
 
Monty
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Wednesday, October 28, = 2009 11:56=20 AM
Subject: [FlyRotary] Re: Prop = Loads

Greg;

 

I had the = same dilemma = when=20 running my engine on the dyno.

 

The = primary reason=20 I wanted to simulate a prop load so I could do tuning of the EC2 on = the=20 dyno.  But that never happened.  I generated an approximate = prop=20 load curve but could never follow it =96 IIRC, it was because you = can=92t set the=20 load, and there is more than one RPM/MAP = combination for a=20 given load.  Dyno work is basically about generating WOT HP and = torque=20 curves. You set the mixture according to the A/F ratio.  And you = always=20 learn some other things along the way =96 flow rates, EGTs, fuel burn, = etc.

 

And=20 Gary, I = don=92t think=20 prop load varies as the square of the rpm =96 does it?  I think = some=20 aspects, like thrust, go as the square; but the drag goes more like = the cube.=20  I generated one both ways, and neither is the real=20 world.

 

Al=20 G

 

 

 

-----Original=20 Message-----
From: = Rotary=20 motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Greg = Ward
Sent: Tuesday, October 27, 2009 = 6:43=20 PM
To: Rotary = motors in=20 aircraft
Subject: = [FlyRotary]=20 Prop Loads

 

Hey=20 Troops;

Finally in=20 the dyno room building the mount plate to begin testing.  Tracy = says that=20 the engine should be tested with the prop on, and this is kind of hard = in a=20 dyno room.  We are mounting the engine without the PSRU, so that = we don't=20 tear it up in testing, and instead hooking directly to the shaft which = is=20 loaded by means of a water brake.  We can put any load on it that = we=20 want, problem is, how to calculate that prop load in foot-pounds, at = different=20 settings.  Talked to Craig Cato, and he is leaving for Europe, so = doesn't=20 have time to run the calcs, and I am just a dumb high country=20 nail-banger.  Any thoughts?

Greg=20 Ward

Lancair 20B=20 N178RG in progress


No virus found in this incoming message.
Checked by AVG = -=20 www.avg.com
Version: 8.5.423 / Virus Database: 270.14.36/2465 - = Release=20 Date: 10/28/09 09:34:00
------=_NextPart_000_0014_01CA57C4.C0039FF0--