flyrotary@lancaironline.net Mailing List Archive

Ed;

I got my numbers from a plot of the distribution of heat shown as a function of mixture (lambda) for a rotary that Paul Lamar posted years ago. I think the difference in our numbers comes mostly from different assumption on mixture, and accounting for unburned fuel. Your number of 25% is correct for a rich mixture; lambda about 0.925. My number, 28% corresponds to a lambda of about 1.10, more like leaned cruise. However; for either condition it shows 6.5 to 7.0% (can’t read the chart with any more accuracy) of the fuel energy goes to the oil cooler.

At lambda of 0.925 the graph shows: 25% to power out; 7% to oil; 12% to the coolant; 35% out the exhaust; 17% unburned gas; 4% other.

At lambda of 1.10 it’s: 28% to power out; 7% to oil; 16% to coolant; 42% out the exhaust; 5% unburned gas; 2% other.

Are we maybe putting too fine a point on this? J

Subject: [FlyRotary] Re: Cooling oil

Well, my figures for 160Hp show fuel burn of 1.58 lbm/min, so a quick sanity check shows 1.58*60 = 94.8 lbsm/hour/6 = 15.8 Gallons/hour which sounds about right for 160HP with a "Best Power" A/F of 12.56

So 1.58 lbm/min *19,000 BTU/Lbm = 30020 BTU/Min

Taking Al's apportionment we have

Power = 28%*30020 = 8405.6 BTU/Min = 198.02 HP (I think this is a bit high on HP for a 15.8 gallon/hr fuel flow, I would expect to

see a fuel flow of around 18.5 gph for close to 200HP)

Coolant = 18%*30020 = 5403.6 BTU/Min

Oil = 7%*30020 = 2101.4 BTU/Min

Exhaust the remainder.

So using Al's figures, we are closer to the 1775 BTU figure for the oil cooler. I use 25% for power and 25% for waste heat and 50% for Exhaust, just to be on the conservative side. Also I allocate 2/3 of waste heat to coolant and 1/3 to oil.

Al's percentages may be closer to reality than the ones I use, which are pretty standard for a reciprocating engine. But, I have never found any similar percentages for the rotary. If someone could direct me to a credible source, I will revise my allocation of BTUs.

Thanks

Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC

----- Original Message -----

From: Dale Rogers

To: Rotary motors in aircraft

Sent: Friday, June 11, 2004 10:26 AM

Subject: [FlyRotary] Re: Cooling oil

Al,

Perchance, did you forget that the 160 HP is *output*,
not the total produced from the fuel burn?

Dale R.
COZY MkIV-R #1254

>
> From: "Al Gietzen" <ALVentures@cox.net>
> Date: 2004/06/11 Fri AM 12:46:45 EDT
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Subject: [FlyRotary] Re: Cooling oil
>
>
>
> Subject: [FlyRotary] Re: Cooling oil
>
>
>
>
>
> ----- Original Message -----
>
> From: "Joseph Berki" <joseph.berki@grc.nasa.gov>
>
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
>
> Sent: Thursday, June 10, 2004 12:39 PM
>
> Subject: [FlyRotary] Re: Cooling oil
>
>
>
>
>
> > It would be interesting to measure flow in both engines. I thought that
>
> > both Lycoming and Mazda engines rejected 2/3 heat load through the
>
> > oil that is why I started going down this road. If the engines generated
>
> > the same Hp than the heat load should be similar.
>
> >
>
> > Joe Berki
>
>
>
> Joe, both engines may generate the same heat load, but the proportion
>
> rejected through the coolant in case of the Mazda is 2/3 of its waste heat
>
> while the oil rejects another 1/3 of the waste heat. Neither engine rejects
>
> anywhere near 2/3 of its waste heat through the oil.
>
>
>
> Most aircraft engines reject on the order of 300-600 BTU/Min through the
>
> oil, the Mazda at 160HP rejects approx 2446 BTU/Min through the oil.
>
>
>
> Ed Anderson
>
>
>
> Ed;
>
>
>
> That number looked a bit high to me, so I went in to my file to check. My
> data shows 28% of the fuel burn energy in the rotary gets converted to HP,
> 18% goes to the coolant, and about 7% to the oil. Most of the rest goes out
> the exhaust pipe. For 160 HP output, I think that should be 1725 BTU/Min
> going to the oil cooler. So about 3 times the comparable powered Lyc.
>
>
>
> Double check me on this.
>
>
>
> Al
>
>
>
>
>
>
>

Subject: [FlyRotary] Re: Cooling oil

----- Original Message -----

From: "Joseph Berki" <joseph.berki@grc.nasa.gov>

To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>

Sent: Thursday, June 10, 2004 12:39 PM

Subject: [FlyRotary] Re: Cooling oil

> It would be interesting to measure flow in both engines. I thought that

> both Lycoming and Mazda engines rejected 2/3 heat load through the

> oil that is why I started going down this road. If the engines generated

> the same Hp than the heat load should be similar.

>

> Joe Berki

Joe, both engines may generate the same heat load, but the proportion

rejected through the coolant in case of the Mazda is 2/3 of its waste heat

while the oil rejects another 1/3 of the waste heat. Neither engine rejects

anywhere near 2/3 of its waste heat through the oil.

Most aircraft engines reject on the order of 300-600 BTU/Min through the

oil, the Mazda at 160HP rejects approx 2446 BTU/Min through the oil.

Ed Anderson

Ed;

That number looked a bit high to me, so I went in to my file to check. My data shows 28% of the fuel burn energy in the rotary gets converted to HP, 18% goes to the coolant, and about 7% to the oil. Most of the rest goes out the exhaust pipe. For 160 HP output, I think that should be 1725 BTU/Min going to the oil cooler. So about 3 times the comparable powered Lyc.

Double check me on this.

Al

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