Return-Path: Received: from fed1rmmtao02.cox.net ([68.230.241.37] verified) by logan.com (CommuniGate Pro SMTP 4.2.3) with ESMTP id 434006 for flyrotary@lancaironline.net; Mon, 27 Sep 2004 13:06:02 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.37; envelope-from=ALVentures@cox.net Received: from BigAl ([68.107.116.221]) by fed1rmmtao02.cox.net (InterMail vM.6.01.03.04 201-2131-111-106-20040729) with ESMTP id <20040927170533.CXJP16348.fed1rmmtao02.cox.net@BigAl> for ; Mon, 27 Sep 2004 13:05:33 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Oil viscosity Date: Mon, 27 Sep 2004 10:05:46 -0700 Message-ID: <005001c4a4b4$3bc23b70$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0051_01C4A479.8F636370" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_0051_01C4A479.8F636370 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable I think it is a mystery, and not heating by the pump - for two reasons: = 1) The heat load added by the pump has to VERY small compared to the heat = load coming from the engine, 2) The pressure the pump is working against is basically the same as determined primarily by the pressure regulator = valve (as confirmed by his data), and the flow is roughly the same because it = is positive displacement pump. =20 Al =20 -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bill Schertz Sent: Monday, September 27, 2004 8:33 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Oil viscosity =20 Some thoughts on Rusty's improved cooling with the lower viscosity oil. = If you recall, there was an earlier discussion about drilling out the oil passage in the iron end plate and taking the oil from there. I believe = Ken Welter did this, and obtained about a (15 degree?) improvement in oil temperature. The only way this effect could be possible is that the pump = is working less hard, and there is therefore less heat being generated in = the oil by the action of the pump. =20 This could relate to Rusty's experience, namely a lower viscosity oil = would require less power input to pump, and the heating due to the pump would = be less. Add to this the beneficial effect of lower viscosity improving the heat rejection in the heat exchanger, and I can believe the improvement = is related to viscosity change. =20 There is an interesting NACA paper "Cylinder-Temperature Correlation of = a single cylinder liquid cooled engine" published in 1946 where they = studied the effects of flow rate and coolant properties on cooling = effectiveness. The correlation of lots of data where they varied the ethylene glycol concentration from 0 to 97% allowed them to determine the relative = effects of heat capacity, thermal conductivity, and viscosity of the cooling = medium. They found that high specific heat, high thermal conductivity, and low viscosity are desirable characteristics of a good cooling fluid. In = order of importance,=20 =20 Thermal conducivity (k) > heat capacity (Cp) > viscosity (v). =20 Rusty is not changing k or Cp with the lighter weight oil, and the = viscosity change only affects the heat transfer effect slightly, so I am left with = the conclusion that it is the decrease in absorbed work that makes the = biggest difference. =20 Bill Schertz KIS Cruiser # 4045 =20 =20 ----- Original Message ----- From: Russell Duffy [mailto:13brv3@bellsouth.net] Sent: 9/26/2004 4:39:16 PM To: flyrotary@lancaironline.net Subject: [FlyRotary] Re: Oil viscosity =20 5W30 seems a bit low. > > I was thinking the same thing. Leon, will an extremely light oil be able to keep the seperation between the bearings and shaft? On the other hand, will it 'wet' the walls of the cooler better and thereby transfer heat more efficiently? =20 Since when it 30 weight oil is "extremely light"? You might call it extremely standard, or extremely normal :-) As I understand it, the = first number is the cold rating, which is just for cold starting, so it = doesn't have any effect on normal operation.=20 =20 BTW, I made about 3 trips around the airport (on the ground of course), = and just made it to 140 degrees. I'm convinced it's cooling much better with = the lighter (though not extremely light ) oil. Can't wait to fly it, but = next Sunday is the earliest possible opportunity, and probably more like the = next weekend.=20 =20 Rusty (Airbike project for sale cheap on eBay now, gotta make room in = the garage) =20 =20 ------=_NextPart_000_0051_01C4A479.8F636370 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message

I think it is a mystery, and not = heating by the pump – for two reasons: 1) The heat load added by the pump = has to VERY small compared to the heat load coming from the engine, 2) The = pressure the pump is working against is basically the same as determined = primarily by the pressure regulator valve (as confirmed by his data), and the flow is roughly the same because it is positive displacement = pump.

 

Al

 

 -----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bill Schertz
Sent: Monday, September 27, 2004 8:33 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = Oil viscosity

 

Some thoughts on Rusty's improved cooling = with the lower viscosity oil.  If you recall, there was an earlier = discussion about drilling out the oil passage in the iron end plate and taking the oil = from there. I believe Ken Welter did this, and obtained about a (15 degree?) improvement in oil temperature. The only way this effect could be = possible is that the pump is working less hard, and there is therefore less heat = being generated in the oil by the action of the pump.

 

This could relate to Rusty's experience, = namely a lower viscosity oil would require less power input to pump, and the = heating due to the pump would be less. Add to this the beneficial effect of lower = viscosity improving the heat rejection in the heat exchanger, and I can believe = the improvement is related to viscosity change.

 

There is an interesting NACA paper "Cylinder-Temperature Correlation of a single cylinder liquid = cooled engine" published in 1946 where they studied the effects of flow = rate and coolant properties on cooling effectiveness. The correlation of lots of = data where they varied the ethylene glycol concentration from 0 to 97% = allowed them to determine the relative effects of heat capacity, thermal = conductivity, and viscosity of the cooling medium.  They found that high specific = heat, high thermal conductivity, and low viscosity are desirable characteristics of = a good cooling fluid. In order of importance,

 

Thermal conducivity (k) > heat capacity (Cp) > viscosity (v).

 

Rusty is not changing k or Cp with the = lighter weight oil, and the viscosity change only affects the heat transfer effect = slightly, so I am left with the conclusion that it is the decrease in absorbed = work that makes the biggest difference.

 

Bill Schertz
KIS Cruiser # 4045

 

 

----- Original Message = -----

From: Russell Duffy [mailto:13brv3@bellsouth.net]

Sent: 9/26/2004 4:39:16 PM

To: flyrotary@lancaironline.net

Subject: [FlyRotary] Re: Oil viscosity

 

5W30 seems a bit low.
>
>
I was thinking the same thing. Leon, will an
extremely light oil be able to keep the seperation
between the bearings and shaft? On the other hand,
will it 'wet' the walls of the cooler better and
thereby transfer heat more efficiently?

 

Since when it 30 = weight oil is "extremely light"? You might call it extremely = standard, or extremely normal :-) As I understand it, the first number is the cold = rating, which is just for cold starting, so it doesn't have any effect on normal operation.

 

BTW, I made = about 3 trips around the airport (on the ground of course), and just made it to 140 = degrees. I'm convinced it's cooling much better with the lighter (though not = extremely light ) oil. Can't wait to fly it, but next Sunday is the earliest = possible opportunity, and probably more like the next weekend.

 

Rusty (Airbike = project for sale cheap on eBay now, gotta make room in the = garage)

 

 

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