4464Re: [Lancair] Lancair 360 oil cooling
- Sep 1, 2014Randy,Tufting was only meant for getting a visual on the slipstream near the NACA inlet.Perhaps moving the cooler to the area in-front of the #2 cylinder is the way to go. That way you're cooler performance will be independent of prop selection. That spot has served me well.ChrisOn Monday, September 1, 2014 9:55 AM, "Randy Stuart Randystuart@... [lancair]" <email@example.com> wrote:
Hi Chris,Prop change... Well, you know.. Always looking for something better. I removed a 72” F7666 prop and installed a new F7068 68” prop. I lost a few top end knots but gained a lot more trust. As a bad side effect from the new prop the NACA doesn’t work as well and the static ports don’t work and I have to add some right rudder all the time. After talking to Hartzell (pretty useless), it would appear that the slip stream change was not good. I know data is only good if it can be replicated... Craig’s plane, he changed from a 320 to a 360 and installed a new scimitar prop. NACA not working as well (higher oil temps), static ports not working well, has to trim for a lot of down elevator in cruise now. We never would have thought a prop could cause lots of problems like these but obviously they can.In hindsight I would have ordered the prop longer, oh well. I now bypass the static port with a valve under the panel, not perfect but much closer. I am thinking about changing the cooler to a larger one, maybe changing the 3” glass duct to 4”. First I need to get my cylinders broken in some.As for my NACA air intake, I made a small pop on scoop that fits on the NACA lip. It puts about an 1” into the wind, forcing more air into it. On a test fight to CMA without it and the return back to WHP with I only saw a few degrees difference. So I’m not sure adding tufting or vortex generators will increase the air pressure.RandyRandy,I look forward to seeing what kind of pressures you are both getting above/below engine, as well as, infront of/behind the cooler. I suggest plotting as a function of IAS across the flight envelope. I recorded 80 to 200 IAS. Your cooler data will be very interesting given the NACA scoop. I am curious if you see any discontinuities as a function of angle of attack (derived from IAS).Regarding the prop dependent cooling issue, you could try tufting ahead of the NACA scoop. The new prop might have changed the local flow to such a degree that the scoop is now pointed in the wrong direction.The 7068 is has pretty decent efficiency. What prompted the switch?ChrisOn Saturday, August 30, 2014 11:59 PM, "Randy Stuart Randystuart@... [lancair]" <firstname.lastname@example.org> wrote:Chris,I agree with you, the key is the inlets. Sealing the baffle and keeping the air flowing smoothly through seal placement and baffle mods helps make the system work but getting the air into the chamber properly is the first order of business. As you know, Craig uses a plenum with diffusers on the inlets and he gets reasonable results, I use the standard baffling with ramps (should be more ramps) and get the same results. Before the new cylinders I would see CHT’s in the mid 300’s, now they are in the high 300’s to just scraping 400 with only about 5 hours of break in time. Craig and I are using a manometer to get some reference readings between the two Lancairs. My biggest problem now is hi oil temps with the probable cause being a prop change from F7666 to F7068. It’s causing lot of problems. Oh well, always something..RandyRandy,I added ramps to my original set-up as well and they made a huge difference. If you carry that thought forward and imagine having ramps not just on the top but sweeping all the way around the circumference of the inlet, you end up with something much like a diffuser. That is what provides the potential for greater pressure recovery. If our inlets were larger, the value of a diffuser would diminish - some pressure recovery would occur ahead of the inlet. At the stock 3.5" all of the recovery is internal.The actual plenum top is nothing more than a means of sealing. A bolted connection is easier to control than a flexible seal between two parts with relative motion. Early experiments in this area were very illuminating. see http://n91cz.com/Interesting_Technical_Reports/NASA_CR3405.pdfgood stuff throughout, but tracking down internal leakage is discussed from page 26 on.Two of the hottest running engines I have encountered actually had plenums, but unfortunately the inlets had issues. On the other hand, the coolest running engines I have ever encountered also had plenums.I would really like to get more pressure data from aircraft with good cooling that have standard baffle set-ups to see what pressures are being obtained.Chris ZavatsonN91CZ360stdwww.N91CZ.netOn Saturday, August 30, 2014 8:23 PM, "Randy Stuart Randystuart@... [lancair]" <email@example.com> wrote:Hi TJ,I believe you’re making the same point I am, it’s all about how you get the air in, putting it where you want it and how the air is getting out. I don’t believe a well designed plenum system would work any better than a well designed baffle system. The purpose of the ramps I added was to keep the inlet air from turbulating as it was entering the inlet holes. This did make a difference. I’m sure much more could be done to keep the air flow moving smoothly, this was an example.We are over at Whiteman KWHP, just a few miles from Simi. Of course you’d would always be welcome over. We have Lancairs and Glasairs. Chris has been by for a visit a few years back. We are pilots, builders and a few grand champion winners. Just give us a heads up... randystuart@...RandyTo increase cooling in the cowling you need to smoothly slow down the air while increasing pressure, so it is your expansion space and transition that is critical, and then being able to efficiently evacuate the air afterwards. Far more important than where to blow the air (directing with ramps) is to avoid separation (and therefore turbulence) as the air expands. A plenum can be designed well (smooth transitions that don't deviate too far from the flow of air too quickly) or poorly (just a pressure box, with corners and transitions that create turbulence and don't allow the air to slow down smoothly) just like you can design standard baffles well or poorly to do the same job.If the thought process is "I'm going to put a box on the engine because I hear that works" then it will only be by accident if you do gain anything. If you think about the airflow under the cowling in terms of "bring in air, smoothly slow and pressurize the air, move through the engine, increase the velocity (and therefore reduce the pressure) on the other side of the engine to evacuate.TJRandy, I'm in Simi Valley, if you are close by and would like some assistance, I would be happy to look over your install with you and see if there is anything obvious that can be improved.On Sat, Aug 30, 2014 at 9:04 AM, Randy Stuart Randystuart@... [lancair] <firstname.lastname@example.org> wrote:With all things being equal I don’t know how one would work better then the other. Chris, I know you’ve done a lot of research in these plenums and many hours designing and building yours. Granted, Lancair’s don’t have the best cooling under any condition. The more drag the less speed, but the only difference I can see between the two is the inlet design. One is wide open and one directs the inlet air. Directing the inlet air can also be done without the plenum. Many years ago I added foam ramps on the top cowl at the inlet holes. This lowered the CHT’s by 10 ~ 15 degs, not ground shaking but directing the air better does improve cooling. I just don’t think there has to be a plenum to do this. Again I say no two plane are the same.RandyAny cooling system is only as good as the weakest link. The hard plenum/diffuser concept doesn't guarantee lower temperatures, it only offers the potential for greater cooling over conventional baffling. It is easier to seal the entire system and easier to control the internal flow and pressure recovery. I have examined good and bad implementations of both systems. When comparing pressure data from each (which is not easy to get since few are nerdy enough to make the measurements), good plenum set-ups have outperformed good conventional set-ups.Another thought on oil cooling troubles: I recall a 360 owner finding an incorrect gasket at the vernatherm housing that was partially blocking oil flow to the cooler. -might be worth checking. Measuring the pressure in-front of and behind the cooler would also provide some insight into the problem. Airflow/pressure vs oil flow.Chris ZavatsonN91CZ360stdOn Thursday, August 28, 2014 10:36 PM, "Randy Stuart Randystuart@... [lancair]" <email@example.com> wrote:I fly with another 360 from my airport, he has a full plenum and mine is conventional. We both have NACA’s for oil cooling. For the most part we both see nearly the same CHT, EGT and oil temps. I’m sure there are many variables involved in both setups but I’ve seen no difference. Some things seem to work better for some and not for others..RandyGlenn,My experience is quite different. When I went from conventional baffling to a plenum set-up my CHTs dropped 35 degrees and it reduced cooling drag by just over 50%. Oil temps were already at 180 during cruise, but with a plenum it became impossible to overheat the oil (over 210 deg F) in any kind of climb or OAT combination.I have examined a few plenum set-ups that didn't work well and the common thread has been inlet, diffuser, plenum transitions. This geometry is more critical for the tiny stock inlets of the 360 because the local velocities are so high. We rely entirely on internal pressure recovery.My 9 row cooler up front is partially blocked from the sheet metal baffling to which it is mounted and I have a deflector on the back side reducing the exit area to about 5 sqin. My pressure recovery in the upper plenum is quite good though so I don't need all of the cooler area.ChrisChris ZavatsonN91CZ360stdOn Thursday, August 28, 2014 11:10 AM, "TJ Johnson misbehaved@... [lancair]" <firstname.lastname@example.org> wrote:NACA vents are low drag, but they don't really work very well for oil coolers due to low pressure recovery of the inlet and the high fin density of the cooler. In a perfect world, you get 80% recovery, in the real world it is much lower. If I were designing it in, I would be tempted to put a small ram inlet on the front of the cowling, followed by appropriate expansion space (you want to double your area while trying to keep the ramp angles under 10 degrees total) before you feed the cooler.If you read this: http://naca.central.cranfield.ac.uk/reports/1945/naca-acr-5i20.pdf They got a total recovery of 57% before they started modifying (scoops, ect., all of which add drag, removing the benefits of having a submerged inlet duct in the first place) that got them all the way to 78%, and they weren't trying to feed something with the fin density of an oil cooler.Anyway, just food for thought.TJOn Thu, Aug 28, 2014 at 4:38 AM, Glenn Long glenn.long@... [lancair] <email@example.com> wrote:Chris,I've got a 13 row in the back and a 9 row up front, just like yours. I tend to disagree on the point about a reduced inlet temperature at the second cooler. Even if the oil temperature is down to 200 when it hits the second cooler, it has plenty of work to do to get to 180. My bet is it won't be able to make the difference.I had a plenum just like you installed first and then tossed it for a convention setup. Lots of extra work and no appreciable change in temperatures. CHTs were completely agnostic to the change. My conclusion is that the oil cooling design and performance on these engines is an afterthought.Save a gaping hole at the point of intake or a nearly externally mounted 24 row oil cooler, we're just gonna run hot. I'm sure there are a folks out there who run around all day at 180, but they must be the very lucky sample population. It's unfortunate in that heat is the ultimate enemy of these engines and there are few options for getting rid of it.Looking forward to winter - GlennOn Wed, Aug 27, 2014 at 8:45 PM, Chris Zavatson chris_zavatson@... [lancair] <firstname.lastname@example.org> wrote:Not all oil coolers are created equal. Unfortunatelly it is difficult to get cooler performance data. I use a 9 row SW10599 in front of the #2 cylinder. It is a squeeze, but it fits.
It worked well with standard baffling and is exceptional with a plenum. If one goes smaller than 9 rows, the pressure required to keep the oil at 180 deg F climb substantially. You can see this when comparing air side dP for the same BTU for a 7 and 9 row cooler .
9 rows works well with typical plenum pressures and the heat dissipation of a 4 cylinder engine. I am not a big fan of NACA scoops for oil coolers, but if going this route, substantially more rows (11, 13) will reduced the pressure required to something more managable for a moderatley sized NACA scoop and can yield good results. Note that there is a huge variation in air-side pressure drop for a given mass flow in the SW data sheets. These are worth studying to get a feel for the sensitivty of performance with change in pressure drop.
Adding a second cooler in series does add more surface area, but the second cooler will have a reduced inlet temperature difference, so its efficiency will be reduced.
Note also that 'pass' defines the number of times the oil crosses the cooler most coolers are one or two pass (8406 vs. 8432).
On Tue, 8/26/14, curtismold@... [lancair] <email@example.com> wrote:
Subject: [Lancair] Lancair 360 oil cooling
Date: Tuesday, August 26, 2014, 4:45 AMtemps).Wow more
Ok had motor IO360 overhauled went
with first run case with oil spray to back of pistons( knew
that it might raise oilto fit.Flight...Climb at 110 knots 2000+ FPM
power.... Wow high oil temps was having to fly with full
ball out using right rudder to keep oil temp in check..
(Hate NACA duct design with 9 pass) SO..Added
second 7 pass oil cooler in front of cly 2. I am running it in series with
back 9 pass. Made a L shaped bracket for
the back and a straight plate for front oil cooler to
strengthen up baffle sits above mounting for cowling
clearance and had to bend up bottom mounting flange for itwith less than 10 hrs still breaking in.7 Pass fits great (I don't
climb 1000 to 7500 peak temps: oil temp to 208 with CHT of
400 and egt of 1350. Need to change gami as # 2 is my
highest egt. Level off 170 knots indicated
oil 180 CHT 375 EGT 1380. Took 2 min to cool
Also i can now do touch and go
with oil around 200.
Remember this is a new motor
think i could fit a 9 pass up front) used a 90 on outside
and 45 inside which i was able to use existing hose from
back oilcooler to the 45 and a new 35" hose to case
Flight out of Port Aransas with
100 deg ground temp made quick work out of getting the wife
to 10,000 at 120 knot climb and cooler weather. 13,500
cruise 195 true 6.8 GPH Holy $H!T batman guess i will park
CE401 for the time
Great mod for you guys with oil
cooling trouble. I know I hated that part of mine in the
,_._,___TJPIK20 N202PKVariEze N25TBGlasair II FT in progressTJPIK20 N202PKVariEze N25TBGlasair II FT in progress
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