Engine Cooling

[Jim Sower]

I have a conical glass "cone" on my Velocty that goes from the little ridge on the aft face of the flywheel just at the base of the ring gear teeth to the prop flange. It sticks on nicely with RTV and makes for a nice smooth path for the ~ 10" - 12" run from the flywheel to flange. Anyway, I met a guy that had the same thing on his Long-EZ and he had put on some about 2" x 2" "vanes" at maybe 3" intervals around that cone near the prop flange (aft edge of the "vanes" was just outside the cowl and they were pitched at around 45 deg.

 

He claimed he had an incurable cooling problem on the ground and that these vanes cleared up. He said they helped cool during climb too. I don't have a problem on the ground, but it won't cost me much to make up some vanes to see if I can cool it a little better in flight.

 

For auto conversions, there isn't a flywheel but there is a prop flange (and back plate for spinner and all). I'm wondering if one could make a cylinderical adaptor to go back over the PSRU for maybe 3" or 4" and mount some of these vanes on it. Absent cowl cheeks, the aft opening of the cowl can be pretty round, and a blower like this could be made to fit pretty tight. It might do a lot of good - particularly on the ground - and probably very little damage in the air.

 

All anecdotal, not stringently documented .... Jim S.

[No4]

Sounds like a good idea Jim,

A sort of ducted fan to aid cooling when without airspeed.

 

For those using water cooled engines, we used to have a trick on the trucks I drove in Africa.

I used to mount a garden hose about an inch away from the front of the radiator, about an inch down from the top. The hose had about 10 small holes in it, with a bolt as a plug in one end, the other end leading to a funnel in the cab.

On a hot day,with a full load, climbing up a mountain road, the temperaure would often get to the red line. I kept a 5 litre container of water in the cab, and would pour some in. The temperaure would almost immediately drop to well in the green.

Now I'm not suggesting we fly with garden hose, a bucket, and a funnel, but a simple electric water pump linked to a small tank and a piece of irrigation pipe with reticulation spray nozzles should do the trick superbly. The weight will be minimal when empty.

How about a windscreen wash pump, tank and nozzles?

To go one step further, you could rig a similar system to cover the intercooler, which should add some horsepower, and the oil cooler. I wouldn't like to comment as to whether you could spray an air cooled engine, because it might crack something.

I understand this system is used on the Reno air racers.

 

Going one step further again, I believe they inject a water/methanol mix into the manifold, to cool the cylinders and allow more boost, but I have no idea as to how one would set up such a system. A lot of gas turbine engines use this water injection system aswell.

 

[Jim Sower]

There has been some discussion in the Rotary list on spraying water on a radiator. I think it would work best if you could atomize it pretty well, and spray the mist over a wider area. The heat of vaporization would suck SCADS of heat out of the radiator flues, just as was you experience in Africa.

 

Water injection has always interested me. I tried for a short while to water inject a Pontiac V8 around 30 years ago. I figured that when the water boiled in the combustion process it would expand and add lots of power. I further thought that it would quench the flame some and reduce Nitrous Oxide emissions. Wasn't aware of any side effects, but I speculated that the water boiling too quickly might cause something akin to detonation. Didn't have any money or sophisticated tools so I couldn't get a proper mixture (like about 1/4 to 1/2 as much water as gas) metered into the manifold and abandoned the project.

 

I seem to recall that it was water injection on takeoff that allowed B-29s to operate out of Iwo Jima and make it all the way to Japan. Of course they were in a position to change engines after 25 hrs.

[No4]

You are right Jim, atomisation is the key with the water spray. I still can't fault the windscreen washer linked to some irrigation nozzles. I think I'll try it. One for the radiator, and one for the intercooler.

 

regarding the water methanol injection, I found this in my gas turbine notes.

 

" Water Methanol Injection

 

Water Methanol consists of approximately 45% methanol and 55% water by volume. Its specific gravity is 0.94. Water methanol is sprayed into the compressor inlet and the temperature of the inlet air is reduced. This action increases the air density allowing an increased thrust to be attained. The methanol burns in the combustion chamber and restores the turbine inlet temperature without the addition of fuel. Engine power is restored [augmented] without adjusting fuel flow.

 

Note: This form of thrust augmentation is of very limited duration and usually only when take off power requirements are critical because of high OAT's or high Density Altitudes. "

 

I heard of a Fokker Frienship turboprop in which the mechanics filled the water methanol container with the oil slops bucket. Both engines burnt right through their casings and they had to ditch onto a frozen river.

[Jim Hann]

No 4,

 

You make me glad that I have "dry" engines on the 41! I know the old Metros had Water/Meth injection, but all the newer birds use something like the APR we have on the 41.

 

Basically, the Integrated Electronic Control (IEC) for the engine will modify its parameters when something bad happens (the other engine quits) to allow more power than would be available at the current SAT (OAT). For the TPE-331-14 on the Jetstream 41, it gives us a 40degree C rise in maximum EGT, which correlates to 13% increase in torque but it won't go above 100% total torque. It can be used for five minutes only.

 

The penalty? Every time the APR fires it costs the company 12 cycles (engine starts), and 200 hours of engine life for every hour of use, or 3.33333333 hours per minute.

 

I have never had to use it in 2,800 hour on the airplane, but I did have the APR fire once on short final on both engines (malfunction), it was a little strange, but nothing bad happened except that the airplane was in maintenance for two days to find out why it happened.

 

Anybody want to try that with a piston?

[No4]

Every now and again I buy a Drag racing magazine for Japanese cars. It has been interesting to look at the turbo and intercooler set ups.

One loony gets 1100 hp at the wheels from a 2.5 litre Nissan six, running 45 psi boost at 11,000 rpm, phew.

 

I turned to page 69, and there was an article on water injection! weird. In their example, they have fixed two misting irrigation nozzles over the intake of a carburretor, attached to a windscreen washer pump. ( de ja vu?). They claimed a 20 kw ( 26 hp) rise in power, and it can replace the intercooler, or supplement it.

 

Nice rig the Jetstream 41, Jim. There are quite a few down here in NZ. One was parked at the Aero club for us to look at, i gave it the fine tooth comb treatment. I hope to use an "emergency power" system with my diesel, but I'm not so sure I'll use water/meth.

[John Slade]

Hey, this water misting thing was supposed to be for cooling, wasn't it? Now you tell me I can inject a mist into the throttle body and get more power. Hmmm. I just happen to have a spare vacuum tube I was going to plug. I guess now I'll need a bigger bottle for cooling.

 

I'm still trying to figure out where to put my duel overflow / screenwasher bottle. Now I need another one.

 

My cowl's getting to the point that you couldn't FIT a cat in there, never mind swing it.

 

Made quite a bit of progress today. There could be light at the end of the tunnel after all.

[No4]

Increased air density = more fuel = more hp

 

For pistons they say there is a problem with hydraulicing if too much un atomised water is pumped in. They advanced the timing by 5' degrees.

No idea how it might affect a rotary; don't have to worry about detonation in a diesel, its always detonating, and when it stops you start to worry.

[Jim Sower]

Yeah. I understand that detonation is a major drawback to water injection, and it's hard to control tight enough to get good benefit without putting yourself in jeorpady of detonation. In a rotary, there's no pistons to burn holes in, but there are apex seals, and breaking one disables two "cylinders". So John shouldn't worry too much about spray bars and pumps and metering. He barely has tanks enough for the fuel that beast is going to consume. No place to put a water tank.

 

But talk about great density! 7.5 lb/cuft.

 

I think they used water injection on F-105 (it needed all the help it could get). They HAD to use it on TO if they had it. Otherwise they were toting 300# or water around with them, and it was a block of ice in a ruptured tank by the time they got home.

[No4]

ERM,

bit out of my depth with the petrol engine, but I'm sure they use water meth to PREVENT detonation, No? Same same intercooling.

preventing detonation = retard timing = loss of power

water meth = advance timing = more power.

 

They put dry ice in the water intercooled dragsters to get serious density. Now maybe if I run a pipe from the air conditioner to the ... stop it no4, oh ok.

 

I'm going to design in a 44 gallon drum, and have a pressure washer blasting onto the intercooler, radiator, and into the turbo intake.. ah no, I can't back that one up either..

[LargePrime]

Increased relative humidity lessens detonation likelyhood.

 

Modern engines have automagic (knock sensor) spark advance and retard to make the most out of the fuel provided. Water misting into the intake can be quite usefull for these engines. Turns cheap gass into race fuel.

 

Your typical lyc/cont has no modern controll system so it really is of Limited use.