Part load to full fuel efficiency for small natural gas 4 stroke engine 1

[rkbest]

I am looking for literature supporting very low efficiencies of small about 8 to 10 kW rated natural gas fired SI engines- water cooled.
Something similar to the graph as attached. I know that the efficiencies go low at part load but how much and are their any testing result that i can refer to. I did not find much info on spec sheets by manufacturers. Although large engines data is easily available. Any help.
I had a thread but i was deleted due to wrong group without being moved here.

 

[GregLocock]

The losses in a natural gas engine will be the same as for a petrol engine at low load.

Cheers

Greg Locock


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[rkbest]

are you be sure that losses be exactly same % as gasoline? As the fuel properties and flame propagation would change with different fuel.

 

[BrianPetersen]

A chart like that can be derived from the BSFC (brake specific fuel consumption) chart by looking up the values at a constant RPM (whatever the RPM of the generator is) and doing the appropriate units conversions.

Your next challenge will be to find the BSFC chart for the specific engine that you are looking that.

Failing that ... the BSFC charts for generic spark-ignition engines are all similar in concept, so try finding one for an engine that operates in a similar RPM range. Gasoline versus natural gas fuel won't make an appreciable difference, but how much error are you willing to tolerate in the results?

 

[GregLocock]

No it won't be EXACT but it will be very similar.

Cheers

Greg Locock


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[turbomotor]

I am guessing, but I think details like mixture ratio and compression ratio will have more effect on the SFC than the direct impact of fuel type. The interesting thing with NG or methane is that regular combustion is possible over a larger range of mixtures, allowing for robust lean of peak operation. Also, I think the knock resistant for methane is relatively high, allowing for high compression ratio. The effect of both of these "allowances" may result in an improvement in system efficiency.

 

[Lou Scannon]

You could try searching websites of public entities that fund alternative fuel R&D projects; perhaps among them you will find small natural gas engine project reports.
Suggestions that come to mind:
[ul]
[li]California Energy Commission[/li]
[li]California Air Resouces Board[/li]
[li]SoCal Gas[/li]
[li]SCAQMD (South Coast Air Quality Management District)[/li]
[li](US) Department of Energy[/li]
[li]NGV Coalition[/li]
[li]IANGV (International Association for Natural Gas Vehicles)[/li]
[li]GRI (Gas Research Institute)[/li]
[/ul]

For all I know some of these organizations may now be dormant or defunct, but perhaps their reports are nevertheless archived somewhere.

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[tbuelna]

...I am looking for literature supporting very low efficiencies of small about 8 to 10 kW rated natural gas fired SI engines- water cooled....

So you only want some data that supports your preexisting conclusions?

I hope you appreciate your use of the phrase "very low efficiencies" is entirely subjective. What is your definition of "very low efficiencies"?

I also assume you meant natural gas fueled SI engine rather than natural gas fired SI engine. The combustion event of an SI IC engine is initiated by a spark produced by the spark plug.

As others noted, the part load efficiency of an SI IC engine using NG fuel would not differ much from one using petrol, all other things being equal.