Yanmar 2TNV70 CHP Project

[Tom Reed]

Some people have done that. I understand that the Midnight classic is a good choice as the load on the generator can be limited.

[SPSInc]

I have a handful of them left over from a previous product line. What kind of power are you needing? I probably have one that will work for you.

[SPSInc]

i watched the video again and have a question.

Would the exhaust HX be more efficient and work better if the engine exhaust went thru the center with the coolant surrounding it?

The egr coolers that I was going to use have the exhaust going thru the center small tubes with the coolant around them,so just wondering.

Mr.Fixit - I guess you can argue which is more efficient. It's been done both ways. It just so happens it works out for a better mechanical fit later in the next revision to run the exhaust over the tubes than through them. This HX took about the perfect amount of heat out of the exhaust so I didn't look any further.

[SPSInc]

Speaking of 48v PMG's. How do you regulate them? I was interested in one of Henry's awhile back but was unclear how to regulate them. I was thinking perhaps you could feed them into a solar charger as PV voltage isn't fixed like a traditional alternator.

To regulate the output you either have to adjust the speed at which the PMG spins or put a converter on its output like a SCR chopper circuit or PWM controlled device or better yet a solar controller.

[RJ]

what do you use to control the engine speed based on load? Interesting setup. Can you run the output directly into a PV controller for either charging a batter bank or converting it into AC. Thinking a grid tied setup PV setup.

[SPSInc]

I will be designing a microprocessor based controller to control the engine speed. I installed a linear actuator in place of the electronic fuel stop solenoid to do the electronic engine governing. You could do a set speed application and rectify and run the output through a solar charge controller too.

[vayidaho]

I, too, have a 2NT70-HGE project going. I initially considered belt driven so the engine could operate at a higher speed for best torque. But, after consideration, I chose direct drive.

My thinking was that since Yanmar designed the engine plain, oil lubricated rear bearing for direct drive, any side thrust from belts would have to be supported by the oil film in the plain rear bearing...an iffy thing.  I can imagine having to take down the engine after a few hundred hours to replace the rear bearing and seal. Not a nice thought.

However, if you could use a SAE-7-1/2 flywheel output shaft adapter with a long stubshaft running true, and support the far end of it with a ball bearing-pillow block, you might be able to eliminate the side wear on the rear engine bearing.  I had one designed and built by Gardner with a 1-3/8 dia stubshaft and it should allow me to chose either sheave drive or direct drive.  I will post more later when it arrives.

Tom

[Henry W]

My understanding is you want to couple an 1800 rpm ST-3 to the Yanmar 2TNV70.
I would not recommend running that diesel at 1800 rpm it will be a shaker because of the odd firing of the 2 cylinders and could tear things up pretty fast. Those engines like to run loaded 2600 RPM's and up to 3600.

The sweet spot for those engines are Low side 2600, Ideal 2800, High side 3000 rpm's

Belt driving it would be the safest bet.

Henry

[Henry W]

I forgot to mention that many Generator and APU manufactures like running these modern diesel engines around 200 rpm's over the peak torque curve. The reason is when the engine is loaded the RPM's drop and the engine will still be over the peak torque curve.

Henry

[Henry W]

I, too, have a 2NT70-HGE project going. I initially considered belt driven so the engine could operate at a higher speed for best torque. But, after consideration, I chose direct drive.

My thinking was that since Yanmar designed the engine plain, oil lubricated rear bearing for direct drive, any side thrust from belts would have to be supported by the oil film in the plain rear bearing...an iffy thing.  I can imagine having to take down the engine after a few hundred hours to replace the rear bearing and seal. Not a nice thought.

However, if you could use a SAE-7-1/2 flywheel output shaft adapter with a long stubshaft running true, and support the far end of it with a ball bearing-pillow block, you might be able to eliminate the side wear on the rear engine bearing.  I had one designed and built by Gardner with a 1-3/8 dia stubshaft and it should allow me to chose either sheave drive or direct drive.  I will post more later when it arrives.

Tom

That engine can take a side load. Running double BX belts with the proper tension would be fine. And the side load would be less than a serpentine belt setup. Some APU Manufactures used that engine and they warrentee it for up to 4000 hours.  http://www.truckgenerators.com/userguide.pdf

Henry

[vayidaho]

My understanding is you want to couple an 1800 rpm ST-3 to the Yanmar 2TNV70.
I would not recommend running that diesel at 1800 rpm it will be a shaker because of the odd firing of the 2 cylinders and could tear things up pretty fast. Those engines like to run loaded 2600 RPM's and up to 3600.

The sweet spot for those engines are Low side 2600, Ideal 2800, High side 3000 rpm's

Belt driving it would be the safest bet.

Henry

Actually, I no longer plan to drive the 4 pole head direct. If I choose the ST head, I will use belts with the rear stubshaft support. I will run the engine at 2600 RPM  as you suggest.  My other thought is to direct drive a PMG through a Charge Controller to keep my 24 volt battery bank happy, and run my cabin off the inverter.

Thanks for the advice!

Tom

[Henry W]

Your welcome Tom,

What PMG are you looking at?

[vayidaho]

PMG?  Have not found one yet. I understand that George at UTTERPOWER used to make a pretty good one, but apparently it is no longer available.  In the meanwhile, I found a self excited 2 pole 5KW Gen Head from BRANDNEWENGINES at a good price, so I will run the diesel at 2600 and the head at 3600 using belts, while I wait for a decent copper wound 1800 RPM ST to appear.

I tore my new ST head apart to confirm it was wound with aluminum as reported in another forum. Sure enough. And crappy solders where coils were connected.  Also had an extremely loose coil which would have to be packed with RTV to keep from vibrating.  So, it goes to the scrap dealer. Too much labor involved in trying to keep junk running. Besides, I never liked the open bearings. Too messy when heated up.

Got my flywheel adapter from Drew Yagelski at Guardian, 219-876-5248 at a very good p-rice for custom machining. Weighs 10.6 lbs, bolts to the SAE 7-1/2 flywheel, has a 1-3/8 stubshaft 5 inches long. He will make anything you need if you send him a sketch.  The engine should benefit from more rotating mass at the lower speeds.

Tom

[mr.fixit]

I have a Mec-Alt(spelling?)from that same supplier belt driven to a 2TNV Yanmar.
Henry is right on with his rpm recomendations. I run mine at 2640rpm and I think that would be the minimum for a good load.
Mine normally runs 4000-4500 watts thru the inverter-charger.
I have found that the voltage(from the gen head) drops quite a bit when loaded over 4500 watts.Sometimes down to 95-100v.Then the inverter spits the generator off.
I may try to re-pulley and get the engine up to2800rpm or so.

[mike90045]

..

I tore my new ST head apart to confirm it was wound with aluminum as reported in another forum. Sure enough. And crappy solders where coils were connected.  Also had an extremely loose coil which would have to be packed with RTV to keep from vibrating.  So, it goes to the scrap dealer. Too much labor involved in trying to keep junk running. Besides, I never liked the open bearings. Too messy when heated up....

Tom

Why not have a motor shop rewind it and get new bearings ?   I just did new sealed bearings in mine - no heat issues with them, and much quieter now.