X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from poplet2.per.eftel.com ([203.24.100.45] verified) by logan.com (CommuniGate Pro SMTP 5.3.2) with ESMTP id 4123318 for flyrotary@lancaironline.net; Fri, 12 Feb 2010 19:46:27 -0500 Received-SPF: none receiver=logan.com; client-ip=203.24.100.45; envelope-from=lendich@aanet.com.au Received: from sv1-1.aanet.com.au (mail.aanet.com.au [203.24.100.34]) by poplet2.per.eftel.com (Postfix) with ESMTP id E0F82173957 for ; Sat, 13 Feb 2010 08:45:51 +0800 (WST) Received: from ownerf1fc517b8 (203.171.92.134.static.rev.aanet.com.au [203.171.92.134]) by sv1-1.aanet.com.au (Postfix) with SMTP id 6E3D4BEC05C for ; Sat, 13 Feb 2010 08:45:51 +0800 (WST) Message-ID: From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Air Pump Date: Sat, 13 Feb 2010 10:45:52 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0011_01CAAC99.B6828020" 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 X-Antivirus: avast! (VPS 100212-2, 02/12/2010), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_0011_01CAAC99.B6828020 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Shipchief, I get my lead on calculations from Ed, he's the Guru on numbers here. George ( down under) I'm remembering that early turbojet engines were sometimes designed = with centrifugal compressors because 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 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 cost 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 note 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 the >> air volume flow through the engine but by increasing = the air density. The >> 100,000 rpm impeller accelerates the air = velocity inside the compressor >> 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 reflecting 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 > 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 intake 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 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, but > 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, = 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 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 easily > enough during testing, and would only = require some sort of restriction 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 unique > engines at the fly-in, with one of the highest = Hp/weight ratios 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. ;*)=20 >=20 >=20 > --=20 > Homepage: http://www.flyrotary.com/=20 > Archive and UnSub: > = http://mail.lancaironline.net:81/lists/flyrotary/List.html=20 > =20 --=20 Homepage: http://www.flyrotary.com/=20 Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html=20 ------=_NextPart_000_0011_01CAAC99.B6828020 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Shipchief,
I get my lead on calculations from Ed, = he's the=20 Guru on numbers here.
George ( down under)
 
I'm remembering that = early=20 turbojet engines were sometimes designed with centrifugal compressors = because=20 compression ratios of up to 8:1 are possible. Axial compressors are = much lower=20 per stage, like about 1.8:1 or something?
I suppose compressor wheel rim speed is esential for boost = pressure, and=20 wheel thickness for volume. So there are your limits, About 6000 RPM, = about=20 11" diameter compressor wheel about 2" thick at the eye (narrower at = the rim=20 where the volute is).
I think this is all something that can be calculated, maybe even = with an=20 online engineering site like efunda?
With high flow and low discharge head, much of success or failure = will be=20 involved with the art of design and fabrication skill of the builder. = Tip=20 leakage at the rim/volute or a sharp turn into the throttle body could = cost=20 all of the gains.
It looks like George is leading on the math...



-----Original=20 Message-----
From: George Lendich = <lendich@aanet.com.au>
To:=20 Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: = Thu,=20 Feb 11, 2010 5:43 pm
Subject: [FlyRotary] Re: Air Pump

Ernest, 
A=20 quick check of my calculations suggest that 170 MPH should be good up = to our=20 RPM requirements. So if your wrong we are both wrong. My figures are = based on=20 a 44 mm PP and the inlet speed in well below that, however I note the = smaller=20 diameter speeds get up to over 200 mph at 7,500 rpm. I can't remember = how your=20 configured. 
George ( down under) 
 
> Ed = Anderson=20 wrote: 
>> 
>> The way a turbo/super = charger=20 works, of course, is not by increasing the >> air volume flow = through=20 the engine but by increasing the air density. The >> 100,000 rpm = impeller accelerates the air velocity inside the compressor >> = vanes and=20 then using the old Diffuser principal, slows this air down at >> = the=20 compressor exit and converts the increased dynamic energy of the = >>=20 accelerated air stream into a static pressure increase reflecting the = >>=20 increased air density=20 produced. 
>> 
>> 
> And the = turbo=20 charger is a centrifugal pump. 8*) One of a comparatively > small = diameter,=20 but high speed. I'm looking at a much larger diameter, > but a much = slower=20 speed. Diameter and speed are what determines the > maximum static=20 pressure. How well the pump can hold that pressure is > determined = by its=20 flow rate, which is in turn determined by the volume of > the pump. = I=20 calculated that the air would flow at 170mph, with the intake > and = exits=20 being 3" diameter. Not exact numbers, but the speed point is > = higher than=20 my projected cruise speed, and the intake diameter is smaller > = than the=20 runner I'll actually have. I have a relatively large volume > = between the=20 flywheel and PSRU plate, being about 4" thick. All that > = scribbling is at=20 home someplace, and I'd be hard pressed to find it. > Basically, = I'm=20 counting on that thickness to overwhelm the engines needs > and = keep the=20 pressure near the max static. 
> 
> I do admit = that I'm=20 remiss in not applying the technical rigor to carry > out the = equations to=20 the 4th digit. You and Al are good at that, Ed, but > I am content = to run=20 some rough numbers. I figure the practical won't > match the = theoretical=20 anyway. So if it looks good at first pass, build it > and then take = a=20 measurement. 
> I think this would be a good move if I can = get 5 to=20 10 extra horses out of > it. On the other side of the equation, I'm = looking=20 at what are the > drawbacks (other than the design/build workload, = which is=20 supposed to be > the fun part anyway). Failure modes, other than = shedding=20 blades, should > be benign or non-existent, as I'm not providing = for any=20 control hardware. > If the flywheel stops turning, the intake can = suck air=20 around the > blades...but that is a moot point, because if the = flywheel=20 stops the > engine is about done sucking air for a while anyhow. A = leak in=20 the intake > means that I don't get as much boost as I hoped. In = that case=20 I'm just > another normally aspirated rotary. The worst case = scenario would=20 be the > highly unlikely event that I get TO MUCH boost. That will = prove=20 out easily > enough during testing, and would only require some = sort of=20 restriction to > rectify. 
> 
> There may be = up to=20 twenty Hp waiting there, and it'll only cost about 3 to > 5lbs of = aluminum.=20 If it works, I'll have one of the coolest, most unique > engines at = the=20 fly-in, with one of the highest Hp/weight ratios around. > If it = doesn't=20 work, I get to wear the "I tried something that didn't work" > = badge that=20 makes one a true Flyrotarian. = ;*) 
> 
> 
>=20 -- 
> Homepage: http://www.flyrotary.com/ 
> Archive = and UnSub:=20 > http://mail.lancaironline.net:81/lists/flyrotary/List.htm= l 
>=20  
-- 
Homepage: http://www.flyrotary.com/ 
Archive and = UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.htm= l 
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