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Hi Doofy,
I would investigate on why at zero load the fuel consumption is so dramatically different between turning at 1800 rpm and 800 rpm. Is the generator a Diesel or Otto engine ? What about the cooling system ?
Perhaps the electric generator add too much drag when turning fast, even when at zero load; is it a permanent magnet rotor, or just coils and iron ?

Basic wrote:

Hi Doofy,
I would investigate on why at zero load the fuel consumption is so dramatically different between turning at 1800 rpm and 800 rpm. Is the generator a Diesel or Otto engine ? What about the cooling system ?
Perhaps the electric generator add too much drag when turning fast, even when at zero load; is it a permanent magnet rotor, or just coils and iron ?

Its a diesel connected to a PMA type gennerator head.

I have also contimplated putting in some switching solenoids on the fuel rail to prevent fuel from being injected into the cylinders. Much like a multi displacment hemi does but instead of shutting down just particular cylinders I would rotate the cylinder every cycle. I think I may be able to keep rpms at 1800 but use less fuel doing so.

Still thinking.....

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Check out Raven Technology's Blackbird product used in firetruck generators for around about 10 years... 1000s of installs. Takes shaft speed (rpm) largely out of the equation.

[url=http://www.raventechpower.com/technology.htm[/url]

[url=http://www.raventechpower.com/blackbird.htm[/url]

[url=http://www.mdatechnology.net/update.aspx?id=a3810[/url]

PEV wrote:

Check out Raven Technology's Blackbird product used in firetruck generators for around about 10 years... 1000s of installs. Takes shaft speed (rpm) largely out of the equation.

[url=http://www.raventechpower.com/technology.htm[/url]

[url=http://www.raventechpower.com/blackbird.htm[/url]

[url=http://www.mdatechnology.net/update.aspx?id=a3810[/url]

Very cool. pretty much what Im looking for the secondary circut they use would be piggybacking on top of the existing generator head. Not sure if my windings are condusive to theis approach however. IMO

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PEV wrote:

Check out Raven Technology's Blackbird product
http://www.raventechpower.com/technology.htm

Thanks PEV this is an interesting approach.

doofy, Basics' idea about looking where the power losses are at 1800 rpm is a good one. Since most (all ?) diesal engines run "open throat" one source of loss you cannot do much about is pumping losses. The cooling systems for either the generator or the ICE are worth a look at. Is there a lot of air movement all the time ?
hope this helps simon

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SimonB wrote:

PEV wrote:

Check out Raven Technology's Blackbird product
http://www.raventechpower.com/technology.htm

Thanks PEV this is an interesting approach.

doofy, Basics' idea about looking where the power losses are at 1800 rpm is a good one. Since most (all ?) diesal engines run "open throat" one source of loss you cannot do much about is pumping losses. The cooling systems for either the generator or the ICE are worth a look at. Is there a lot of air movement all the time ?
hope this helps simon

Yeah air is always blowing as the cooling fan is 'hard-coded' to the crank via pulley. Not sure what to make of looking at the losses as I figure the amount of cooling that is needed is directly related to the speed of the engine and therefore always a parasitic draw at the same rate no matter where in the rpm range I am.

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The amount of cooling is pretty directly a function of the output power not the rpm. At no-load much less cooling is required.
For a directly coupled fan it will be specified to provide enough cooling for full load at maximum ambient temperature. At no load this will be a significant waste of energy.
Modern cars use electric fans as an easy way to save the power needed to turn the fan (most of the time).
It will certainly be worth looking into decoupling the fan drive from the engine and using a themostatic control to run the fan at a rate to match the load. Any approach will need to be very reliable as failure will probably destroy the generator and may cause a fire.

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SimonB wrote:

The amount of cooling is pretty directly a function of the output power not the rpm.

yes you are corect, but in my brave new world, less load = less rpm.

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SimonB wrote:

The amount of cooling is pretty directly a function of the output power not the rpm. At no-load much less cooling is required.
For a directly coupled fan it will be specified to provide enough cooling for full load at maximum ambient temperature. At no load this will be a significant waste of energy.
Modern cars use electric fans as an easy way to save the power needed to turn the fan (most of the time).
It will certainly be worth looking into decoupling the fan drive from the engine and using a themostatic control to run the fan at a rate to match the load. Any approach will need to be very reliable as failure will probably destroy the generator and may cause a fire.

I could get one of those nifty fan controls with a clutch and a solenoid that is activated by a thermostat.

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SimonB wrote:

The amount of cooling is pretty directly a function of the output power not the rpm. At no-load much less cooling is required.
For a directly coupled fan it will be specified to provide enough cooling for full load at maximum ambient temperature. At no load this will be a significant waste of energy.
Modern cars use electric fans as an easy way to save the power needed to turn the fan (most of the time).
It will certainly be worth looking into decoupling the fan drive from the engine and using a themostatic control to run the fan at a rate to match the load. Any approach will need to be very reliable as failure will probably destroy the generator and may cause a fire.

quick question, would it be more efficient to run the fan off of the electricity drawn from the gennerator head or to go the mechanical clutch/thermostat route that is using mechanical energy?

Interested in your thoughts.

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doofy wrote:

quick question, would it be more efficient to run the fan off of the electricity drawn from the gennerator head or to go the mechanical clutch/thermostat route that is using mechanical energy?

Interested in your thoughts.

Either approach will work. With an electric fan you do get the mechanical to electrical to mechanical losses but the fan(s) can be mounted right on the radiator and be more efficient.
I'm guessing that the water pump is driven off the same V belt that drives the fan so you can't do away with the belt completely.
You could thnk about using a much larger external radiator and passive cooling but would need to make sure it had enough heat dissipation for full load.
It is probably fairly easy to test the effect of removing the fan by measuring the fuel consumption with the fan removed. You will need a couple of desk fans powered off a separate supply to keep the air flow going for cooling and to keep an eye on engine temperature during the test.

Last edited Thu, 10 Nov 2011, 2:17am by SimonB

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SimonB wrote:

doofy wrote:

quick question, would it be more efficient to run the fan off of the electricity drawn from the gennerator head or to go the mechanical clutch/thermostat route that is using mechanical energy?

Interested in your thoughts.

Either approach will work. With an electric fan you do get the mechanical to electrical to mechanical losses but the fan(s) can be mounted right on the radiator and be more efficient.
I'm guessing that the water pump is driven off the same V belt that drives the fan so you can't do away with the belt completely.
You could thnk about using a much larger external radiator and passive cooling but would need to make sure it had enough heat dissipation for full load.
It is probably fairly easy to test the effect of removing the fan by measuring the fuel consumption with the fan removed. You will need a couple of desk fans powered off a separate supply to keep the air flow going for cooling and to keep an eye on engine temperature during the test.

Great idea. I actually have an old 50 gallon water heater that I wanted to actively heat to get even more efficiency from the diesel while running. I have a heat exchanger running into the tank. Also using the radiator as a shop heater in winter time. It would be kind of nice to have an all in one utility(electricity and domestic water heating) Again, the only way this makes financial sense is to use old vegetable oil and filter to 5 microns.
But in an end of times scenario, I would have a jem.

Fun Fun Fun

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doofy wrote:

I actually have an old 50 gallon water heater that I wanted to actively heat to get even more efficiency from the diesel while running. I have a heat exchanger running into the tank. Also using the radiator as a shop heater in winter time. It would be kind of nice to have an all in one utility(electricity and domestic water heating) Again, the only way this makes financial sense is to use old vegetable oil and filter to 5 microns.
But in an end of times scenario, I would have a jem.

That really would be an efficient use of the waste heat ! In yachts I've been on they do the same thing, using engine waste heat for domestic hot water.
Best of luck with it. Let us know how it turns out.
Best Simon

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Here was my response back from the Raven guys.

"Hi

Thanks for your inquiry.

Our generator needs a shaft speed of at least 3000 RPM, and can go as high as 9000 RPM keeping 120VAC 60 HZ power.

We often match to engines going less than 800 RPM by way of belt and pulley or PTO gears.

Our generators are field controlled – excited ( not permanent magnet type) and that is integral to keeping the 60 Hz output.

Not sure if this could match your needs.

Regards,

---Chris ----------------------------------------------------------------

"

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