REFLECTOR: High Oil Temps
Brian Michalk
michalk at awpi.com
Mon Jun 24 12:57:51 CDT 2013
What would happen if you just vented into the engine compartment?
On 6/24/2013 9:52 AM, Brent Bourgeois wrote:
> I did lots of measuring in flight and found inlet area is not nearly
> as important as exit area. Most have way to much inlet and the largest
> portion of the air never makes it through the cooler. I was never
> successful cramming more air in the cooler and achieved real good
> results sucking it out. ( that's for cylinder cooling also) A ramp or
> lip in front of the exit can be used to actually make the air behind
> the cooler much lower pressure than in front. My coolers are good for
> about 15 degrees each. The best thing I did was to move the oil lines
> each to their own duct and add a 1 inch hole inlet and a 1.5 x3
> reverse ramp on the duct exit 6 inches before the firewall. There is
> more cooling available in those 2 long aluminum lines than most coolers.
> Cool the oil and the CHT problem will take care of it self.
> Call if I can help
> 985-785 eight two nine 9
> Brent
> N61VB
>
>
> ------------------------------------------------------------------------
> *From:* steve korney <s_korney at hotmail.com>
> *To:* Reflector Reflector <reflector at tvbf.org>
> *Sent:* Sunday, June 23, 2013 10:09 PM
> *Subject:* Re: REFLECTOR: High Oil Temps
>
> It will take about 8 square inches of inlet to get enough air to each
> oil cooler at 150 knots...
>
>
>
> Steve
>
> ------------------------------------------------------------------------
> Date: Sun, 23 Jun 2013 21:35:47 -0500
> From: michalk at awpi.com
> To: reflector at tvbf.org
> Subject: Re: REFLECTOR: High Oil Temps
>
> They are the stock coolers, about 4.5" x 6" face area. The inlet duct
> is not a real NACA scoop. I extended the face of the cooler to the
> skin of the plane. Once I have enough hours, I will experiment with
> closing down the aft lip of the inlet, making a diverging duct.
>
> I've already closed down my armpit scoops a little based upon oil
> flows on the fuselage. I have variable armpit scoops, but at the
> moment they are only ground adjustable.
>
> On 06/23/2013 09:29 PM, steve korney wrote:
>
> Hey Brian...how big are the oil coolers and how much inlet scoop
> area do you have...?
>
>
>
> Steve
>
> > Date: Sun, 23 Jun 2013 17:42:44 -0500
> > From: michalk at awpi.com <mailto:michalk at awpi.com>
> > To: reflector at tvbf.org <mailto:reflector at tvbf.org>
> > Subject: REFLECTOR: High Oil Temps
> >
> > Today I had a very good test flight.
> >
> > I've been battling high CHT and oil temps, and made the decision to
> > increase my prop pitch for todays flight to bring down RPM's.
> That made
> > a marked difference in CHT temps, and I could fly without
> redlining the
> > CHT's.
> >
> > Now, I still have high oil temps. My oil cooler arrangement is
> two oil
> > coolers in the nose in parallel. The secondary cooler has a
> radiator
> > fan attached with a flapper valve that doubles for ground
> operations and
> > cabin heat. Needless to say, the fan doesn't do a very good job,
> and I
> > think is the source of my high oil temps.
> > For this thought game, assume two identical oil coolers with
> equal oil
> > flow in parallel. This means that each cooler gets 50% of the oil.
> > Now, assume no cooling air flows through one of the coolers. The
> result
> > is that half the oil is cooled, and the other half gets returned
> at the
> > same temperature it began. The result is that I get 50% of the
> cooling
> > that's available.
> >
> > What I've done in the meantime is I've capped off my second
> cooler. I
> > have not flown with this configuration, and will do so this coming
> > weekend. I really do think this will get me within the temperature
> > ranges to get around to some serious flight testing.
> >
> > Now, the real question:
> > Given two identical coolers that flow equal parts oil, and also
> have
> > equal amounts of airflow, is it better to plumb them in series
> or in
> > parallel for maximum heat rejection? It seems to me that
> parallel is
> > like having more frontal cooler area, while in series would be like
> > having a thicker cooler, with the larger frontal area being the
> more
> > efficient design.
> >
> > Does anyone have any info on this?
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