|
|
I think the approach makes sense for the worse-case hot weather environment but from a northern perspective you have to do something when it gets cold. If you design a system to cool at 100F OAT, your engine it is going to be too cold at 0F OAT; in fact it will be exactly 100F less, typically 80F.
Right now I'm using grills that block off approximately 50% of inlet air flow; at 0F I add tape to reduce to 25% air flow. This is of course only ground adjustable but adequate for typical winter flying. Running synthetic oil a bit too cool is less significant than running the glycol too cool. My long-term approach will be to install an in-flight adjustable flap to restrict the outlet air of my radiator, which does not provide airflow over the engine, only my oil coolers do that.
Jeff
-----Original Message-----
From: Ernest Christley [mailto:echristley@att.net]
Sent: Thursday, March 08, 2012 3:38 PM
Subject: Re: [FlyRotary] Engine cooling
Chris Barber wrote:
Just some data points for discussion. PLEASE if you know some stuff
that is rotary specific, or just wrong, CHIME IN!!
Chris
Houston
Cooling Guidelines for V8 Engines in Aircraft by Bud Warren and
Phyllis Ridings
After much thought, Bud decided to install a thermostat in the LS1
engine of the Ravin 500 to do some test flying. During cold weather
the resulting engine temps have remained stable at 190°F at cruise,
and near 200°F during climb out; just about what we see during the
warm months of the year. This has corrected the check engine light
coming on due to the engine remaining in warm up mode.
This approach makes me nervous. It doesn't hit us much here in the southern US, but things get colder as we move north.
When it is freezing on the ground, it's very easy to get REALLY cold temps at altitude. If it is 0*F on the ground,
then the rule of thumb says that it will be -40* at altitude.
The problem described is that the engine isn't able to produce enough heat to warm the water with the amount of -40*F air that is rushing through. The prescription given is to force the water to stay in the engine longer. This necessarily means that the water will stay in the radiator longer. Now the thermostat opens even less, because what it pulls from the radiator is ice water. At some point, the water gets really hard in the radiator and stops flowing altogether. The there is no flow from the engine to melt it. The engine water keep recirculating and it eventually overheats.
The Mack truck I bought in the late 80's had a shutter arrangement in front that would close when it got to cold and block airflow through the radiator. I think a thin aluminum panel, possibly controlled by a push-pull cable from the cockpit, that slid in to partially block the radiator would be a much safer solution. It would also alleviate the concern over broken thermostats. The panel would require minimal support, as it could simply lay flat against the radiator face.
This message, and the documents attached hereto, is intended only for the addressee and may contain privileged or confidential information. Any unauthorized disclosure is strictly prohibited. If you have received this message in error, please notify us immediately so that we may correct our internal records. Please then delete the original message. Thank you.
|
|