X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imr-da03.mx.aol.com ([205.188.105.145] verified) by logan.com (CommuniGate Pro SMTP 5.3.2) with ESMTP id 4123286 for flyrotary@lancaironline.net; Fri, 12 Feb 2010 18:43:30 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.188.105.145; envelope-from=SHIPCHIEF@aol.com Received: from imo-ma03.mx.aol.com (imo-ma03.mx.aol.com [64.12.78.138]) by imr-da03.mx.aol.com (8.14.1/8.14.1) with ESMTP id o1CNgtU3031751 for ; Fri, 12 Feb 2010 18:42:55 -0500 Received: from SHIPCHIEF@aol.com by imo-ma03.mx.aol.com (mail_out_v42.9.) id q.c13.4c75b706 (43960) for ; Fri, 12 Feb 2010 18:42:49 -0500 (EST) Received: from smtprly-de03.mx.aol.com (smtprly-de03.mx.aol.com [205.188.249.170]) by cia-dd02.mx.aol.com (v127.7) with ESMTP id MAILCIADD021-b2404b75e7742f3; Fri, 12 Feb 2010 18:42:49 -0500 Received: from webmail-m020 (webmail-m020.sim.aol.com [64.12.101.104]) by smtprly-de03.mx.aol.com (v127.7) with ESMTP id MAILSMTPRLYDE031-b2404b75e7742f3; Fri, 12 Feb 2010 18:42:44 -0500 References: To: flyrotary@lancaironline.net Subject: Re: [FlyRotary] Re: Air Pump Date: Fri, 12 Feb 2010 18:42:44 -0500 X-AOL-IP: 24.19.204.151 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: shipchief@aol.com X-MB-Message-Type: User Content-Type: multipart/alternative; boundary="--------MB_8CC7A5435749BAB_3480_33A7_webmail-m020.sysops.aol.com" X-Mailer: AOL Webmail 30746-STANDARD Received: from 24.19.204.151 by webmail-m020.sysops.aol.com (64.12.101.104) with HTTP (WebMailUI); Fri, 12 Feb 2010 18:42:44 -0500 Message-Id: <8CC7A543563F1FD-3480-1995@webmail-m020.sysops.aol.com> X-Spam-Flag:NO X-AOL-SENDER: SHIPCHIEF@aol.com ----------MB_8CC7A5435749BAB_3480_33A7_webmail-m020.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="us-ascii" I'm remembering that early turbojet engines were sometimes designed with= centrifugal compressors because compression ratios of up to 8:1 are possi= ble. Axial compressors are much lower per stage, like about 1.8:1 or somet= hing? I suppose compressor wheel rim speed is esential for boost pressure, and= wheel thickness for volume. So there are your limits, About 6000 RPM, abo= ut 11" diameter compressor wheel about 2" thick at the eye (narrower at th= e rim where the volute is). I think this is all something that can be calculated, maybe even with an= online engineering site like efunda? With high flow and low discharge head, much of success or failure will be= involved with the art of design and fabrication skill of the builder. Tip= leakage at the rim/volute or a sharp turn into the throttle body could co= st all of the gains. It looks like George is leading on the math... -----Original Message----- From: George Lendich To: Rotary motors in aircraft Sent: Thu, Feb 11, 2010 5:43 pm Subject: [FlyRotary] Re: Air Pump Ernest,=20 A quick check of my calculations suggest that 170 MPH should be good up to= our RPM requirements. So if your wrong we are both wrong. My figures are= based on a 44 mm PP and the inlet speed in well below that, however I not= e the smaller diameter speeds get up to over 200 mph at 7,500 rpm. I can't= remember how your configured.=20 George ( down under)=20 =20 > Ed Anderson wrote:=20 >>=20 >> The way a turbo/super charger works, of course, is not by increasing th= e >> air volume flow through the engine but by increasing the air density.= The >> 100,000 rpm impeller accelerates the air velocity inside the compr= essor >> vanes and then using the old Diffuser principal, slows this air= down at >> the compressor exit and converts the increased dynamic energy= of the >> accelerated air stream into a static pressure increase reflecti= ng the >> increased air density produced.=20 >>=20 >>=20 > And the turbo charger is a centrifugal pump. 8*) One of a comparatively= > small diameter, but high speed. I'm looking at a much larger diameter,= > but a much slower speed. Diameter and speed are what determines the >= maximum static pressure. How well the pump can hold that pressure is > de= termined by its flow rate, which is in turn determined by the volume of >= the pump. I calculated that the air would flow at 170mph, with the intake= > and exits being 3" diameter. Not exact numbers, but the speed point is= > higher than my projected cruise speed, and the intake diameter is small= er > than the runner I'll actually have. I have a relatively large volume= > between the flywheel and PSRU plate, being about 4" thick. All that >= scribbling is at home someplace, and I'd be hard pressed to find it. > Ba= sically, I'm counting on that thickness to overwhelm the engines needs >= and keep the pressure near the max static.=20 >=20 > I do admit that I'm remiss in not applying the technical rigor to carry= > out the equations to the 4th digit. You and Al are good at that, Ed, bu= t > I am content to run some rough numbers. I figure the practical won't= > match the theoretical anyway. So if it looks good at first pass, build= it > and then take a measurement.=20 > I think this would be a good move if I can get 5 to 10 extra horses out= of > it. On the other side of the equation, I'm looking at what are the= > drawbacks (other than the design/build workload, which is supposed to= be > the fun part anyway). Failure modes, other than shedding blades, sho= uld > be benign or non-existent, as I'm not providing for any control hard= ware. > If the flywheel stops turning, the intake can suck air around the= > blades...but that is a moot point, because if the flywheel stops the >= engine is about done sucking air for a while anyhow. A leak in the intake= > means that I don't get as much boost as I hoped. In that case I'm just= > another normally aspirated rotary. The worst case scenario would be the= > highly unlikely event that I get TO MUCH boost. That will prove out eas= ily > enough during testing, and would only require some sort of restricti= on to > rectify.=20 >=20 > There may be up to twenty Hp waiting there, and it'll only cost about 3= to > 5lbs of aluminum. If it works, I'll have one of the coolest, most un= ique > engines at the fly-in, with one of the highest Hp/weight ratios aro= und. > If it doesn't work, I get to wear the "I tried something that didn'= t work" > badge that makes one a true Flyrotarian. ;*)=20 >=20 >=20 > --=20 > Homepage: http://www.flyrotary.com/=20 > Archive and UnSub: > http://mail.lancaironline.net:81/lists/flyrotary/Li= st.html=20 > =20 --=20 Homepage: http://www.flyrotary.com/=20 Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.h= tml=20 ----------MB_8CC7A5435749BAB_3480_33A7_webmail-m020.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="us-ascii"
I'm remembering that earl= y turbojet engines were sometimes designed with centrifugal compressors be= cause compression ratios of up to 8:1 are possible. Axial compressors are= much lower per stage, like about 1.8:1 or something?
I suppose compressor wheel rim speed is esential for boost pressure,= and wheel thickness for volume. So there are your limits, About 6000 RPM,= about 11" diameter compressor wheel about 2" thick at the eye (narrower= at the rim where the volute is).
I think this is all something that can be calculated, maybe even with= an online engineering site like efunda?
With high flow and low discharge head, much of success or failure wil= l be involved with the art of design and fabrication skill of the builder.= Tip leakage at the rim/volute or a sharp turn into the throttle body coul= d cost all of the gains.
It looks like George is leading on the math...



-----Original Message-----
From: George Lendich <lendich@aanet.com.au>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Thu, Feb 11, 2010 5:43 pm
Subject: [FlyRotary] Re: Air Pump

Ernest, 
A quick check of my calculations suggest that 170 MPH should be good up to= our RPM requirements. So if your wrong we are both wrong. My figures are= based on a 44 mm PP and the inlet speed in well below that, however I not= e the smaller diameter speeds get up to over 200 mph at 7,500 rpm. I can't= remember how your configured. 
George ( down under) 
 
> Ed Anderson wrote: 
>> 
>> The way a turbo/super charger works, of course, is not by increas= ing the >> air volume flow through the engine but by increasing the= air density. The >> 100,000 rpm impeller accelerates the air veloci= ty inside the compressor >> vanes and then using the old Diffuser pr= incipal, slows this air down at >> the compressor exit and converts= the increased dynamic energy of the >> accelerated air stream into= a static pressure increase reflecting the >> increased air density= produced. 
>> 
>> 
> And the turbo charger is a centrifugal pump. 8*) One of a comparative= ly > small diameter, but high speed. I'm looking at a much larger diame= ter, > but a much slower speed. Diameter and speed are what determines= the > maximum static pressure. How well the pump can hold that pressur= e is > determined by its flow rate, which is in turn determined by the= volume of > the pump. I calculated that the air would flow at 170mph,= with the intake > and exits being 3" diameter. Not exact numbers, but= the speed point is > higher than my projected cruise speed, and the in= take diameter is smaller > than the runner I'll actually have. I have= a relatively large volume > between the flywheel and PSRU plate, being= about 4" thick. All that > scribbling is at home someplace, and I'd be= hard pressed to find it. > Basically, I'm counting on that thickness= to overwhelm the engines needs > and keep the pressure near the max st= atic. 
> 
> I do admit that I'm remiss in not applying the technical rigor to car= ry > out the equations to the 4th digit. You and Al are good at that,= Ed, but > I am content to run some rough numbers. I figure the practic= al won't > match the theoretical anyway. So if it looks good at first= pass, build it > and then take a measurement. 
> I think this would be a good move if I can get 5 to 10 extra horses= out of > it. On the other side of the equation, I'm looking at what ar= e the > drawbacks (other than the design/build workload, which is suppo= sed to be > the fun part anyway). Failure modes, other than shedding bl= ades, should > be benign or non-existent, as I'm not providing for any= control hardware. > If the flywheel stops turning, the intake can suck= air around the > blades...but that is a moot point, because if the fly= wheel stops the > engine is about done sucking air for a while anyhow.= A leak in the intake > means that I don't get as much boost as I hoped= . In that case I'm just > another normally aspirated rotary. The worst= case scenario would be the > highly unlikely event that I get TO MUCH= boost. That will prove out easily > enough during testing, and would= only require some sort of restriction to > rectify. 
> 
> There may be up to twenty Hp waiting there, and it'll only cost about= 3 to > 5lbs of aluminum. If it works, I'll have one of the coolest, mo= st unique > engines at the fly-in, with one of the highest Hp/weight ra= tios around. > If it doesn't work, I get to wear the "I tried something= that didn't work" > badge that makes one a true Flyrotarian. ;*) =
> 
> 
> -- 
> Homepage: http:= //www.flyrotary.com/ 
> Archive and UnSub: > http://mail.lancaironline.net:81= /lists/flyrotary/List.html 
>  
-- 
Homepage: http://www= .flyrotary.com/ 
Archive and UnSub: http://mail.lancaironline.net:81/lists/fly= rotary/List.html 
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