GM 90 cogen project

[squarebob]

Now that I have got the engine, it is time to start the project and document the progress as I move forward. I hope to run a 150 amp 24v alternator for a battery bank charger, also a 5kw genhead for other loads and heat exchangers on the cooling and exhaust. Some history: The engine was purchased from Mike M.  about 5 years ago and never used. That makes it a NEW GM90. I got it home this weekend and got it off the trailer and into the shop on Monday.

Bob

[squarebob]

I picked up a napa 253 thermostat ( 195 degree ) and a 1 1/4" union. The thermostat fit real nice in the union. I don't know if it will seal but we will give it a try. I drilled a 5/64 bleed hole in the stat as it had no jiggle pin.

Bob

[squarebob]

I plan on running on a WMO - ORD ( off road diesel ) mix. I think I will start at 50/50 ratio and tweak it from there. I plan on starting and stopping the engine on ORD to make it easier to start. I plan on an electric start as cranking is not for me. I am known as " the rugged indoor type" !!! 2 heart attacks years ago have slowed me down a bit. Please feel free to give advice and keep me from going way off track as I play with this project.

Bob

[LowGear]

When I first looked at your thermostat "O-Ring" leaped into my mind to reduce side sluice.

Casey

[vdubnut62]

SquareBob, somebody makes a neat Oring thermostat gasket with a channel in it.  Think U shaped rubber channel with  the ends joined to make a circle.
It may be a toyota truck from about 85-86 with the 22re engine or either a nissan sentra of  the same vintage.
Should work like a charm to stop  drips.
Sucks getting old, CRS is such a pain....
Ron

[squarebob]

If this setup leaks, I will look into that thermostat.
Here are the frame rails I made yesterday.

[squarebob]

Had a productive day today. Got the frame rails painted and installed on the engine. Then I set about making the mount for the alternator. Got the pieces made in record time and then tacked the assembly to the frame. I sure am enjoying this project.

Bob

[Ronmar]

It is the Toyota 22R, RE and RE-T engines that use that split O-ring thermostat seal. 83 to 95...  You should be able to get the seal at just about any auto parts store... 

The project is looking good.  What type starter are you planning, ring gear, belt or contact wheel?

[squarebob]

My thoughts are to use a contact wheel setup.
I am wondering if this starter has enough balls to get those big flywheels going.........

http://cgi.ebay.com/ebaymotors/New-Briggs-Stratton-Starter-16-Tooth-390838-4975594-/140442794807?pt=Motors_ATV_Parts_Accessories&hash=item20b30afb37

I like this one because it looks like I could get buy without a bearing support on the end of the shaft and it has a mounting tab built in.

[rl71459]

Its balls look kinda small to me

[vdubnut62]

That looks like a briggs and stratton starter to me. If so, it's got Chicken Balls, sorry.
Permanent magnet, with a plastic brush holder that melts under heavy use, at least the aftermarket ones.
Ron

[squarebob]

I found the starter I am going to use . It is a 1 Kw, 20 pound unit from an early 60s Ford truck. Good flanges and a nice long shaft for the drive roller. Bigger balls than the B&S Starter I was looking at. Cost is 39.99.

Bob

[squarebob]

Too hot to work in the shop so a little math test for myself. Lets not worry about parasitic and other losses for now. I need to size the heatex and radiator and hoses to properly remove the heat from the system.
The GM 90 is said to use 235 G fuel per Kw/Hr output. Listed output is 4.4 Kw. Assume 80% load, then 4.4@80%= 3.52Kw
3.52Kw * 235g = 827 grams of fuel per hr consumption
Assume 7lbs and 130,000 btu per gallon of fuel. or 18,571 btu per lb of fuel.
827 grams = 1.823 lbs of fuel.
1.823 * 18,571 btu = 33,855 btu/ hr output. Apply the 1/3rd rule and you get 11,285 btu's each of rotational energy, exhaust btu's and coolant btu's per hour.
Lets look at the coolant first. 11,285 btu/hr divided by 60 minutes = 188 btu's per minute produced.
Assume 50 deg F temp rise. 145 Deg F coolant into engine from radiator or heatex and 195 Deg F coolant out of engine.
Known - 1 btu raises 1 lb of water 1 Deg F
188 btu divided by 50 Deg F rise =3.76 lbs of water flow needed per minute to remove the heat generated.
3.76 divided by 8.34 ( weight of water per gallon ) = .45 gallon per minute flow of water thru engine to keep it cool.
First conclusion: 1/2" dia. heater hose from engine to radiator / heatex will be a sufficient diameter to handle the flow.
I am now exhausted from all the math. Am I in the ballpark here or have I had too much to drink tonight?
Thanks

Bob

[vdubnut62]

I would like to add something with great gravity, insight and intelligence, but all I can come up with is this...............
We need a smiley that scratches his head, then his ass, and repeats.
My apologies to all. Sorry.
Ron 

[Ronmar]

Bob,  most every reference I have seen shows #2 diesel at 140KBTU per gallon...  Your numbers sound pretty good for 80% load, but perhaps just a little low.  I have measured just shy of 18KBTU/HR out of my heat exchanger with my 6/1 at it's maximum sustainable load.  I don't know the primary coolant flow as it is thermosiphon and I havn't figured a way to accurately measure it.  But I guess using a little reverse math, I can make an estimate.  I am delivering 195F coolant to the heatex and the return temp to the engine is around 100F at full load.  From that 95F drop I am extracting 18,000 BTU/hr, so 18K divided by 95 = 189 pounds of water per hour thru the primary loop? Divide by 8lb/gal for 23.6 gal/hr. Divide by 60 for approx .39 GPM of thermosiphon flow on my system?  I am of course using 1" plumbing, which was convenient as the heatex I chose has 1" NPT ports:).

JusT remember, whatever components you choose need to be sized for full load/worst cooling conditions.  The heat must flow from the engine:). What kind of pump are you going to use?