Calculating thermal input for HV diesel generator 2

[benjho]

Hi guys,

im trying to work out the thermal input for a large diesel generator. It produces 4.16kV and 1.7MW power so quite big engines.

Read about some things on internet but its mostly about welding inputs.

Any help would be appreciated.

B

 

[PersonalProfile]

Assume thermal output is intended.

1. Contact manufacturer.
2. Failing 1. rough estimate (assume n= / >50%) = / < 1.7 MW.

Regards,
Lyle

 

[waross]

13+ KWHr per Gallon of diesel fuel at normal SG. For Specific Gravity fuel above or below standard fuel the PU change in thermal content will be very close to the PU change in SG.
For a more accurate solution you must see the specs on the set. Read the fine print and check the fine print for the SG of the test fuel. Some manufactures have been known to fudge their test results by using heavier than normal fuel for test runs.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[7anoter4]

Usually, as lylebrown00 said the Manufacturer will indicate this in his catalogue [For instance from Sulzer 305 g/kwh ]
You may calculate following for instance:

http://www.freestudy.co.uk/thermodynamics/t4201.pdf

Here an example:
Pkw = 1700 [kw] generator output
GENeff = 95% ask the manufacturer
Pmec=Pkw/GENeff= 1789.5 kw diesel output
dieseleff= 26% ask the manufacturer
energyMJ= 45.3 MJ/kg diesel fuel energy/kg
kgperMJ= 1/energyMJ= 0.022075 kg/MJ
MJ=Mw*sec
kgperMwh= kgperMJ*3600 = 79.47 kg/Mwh netto
kgperMwhrequired= kgperMwh/dieseleff = 305.65 diesel input per Mwh
For 1.7 MW it needs 1.7895*305.65= 546.96 kg/hour.
546.96 kg=546.96/0.83= 659 litres [174.1 gal/hour]

 

[jraef]

Bill's da man!

I was going to say something much less specific such as measure the electrical kW output and the fuel input, convert them both to BTUs and the delta is the thermal output (waste) of the DG.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[benjho]

Hi again guys,

Thanks a lot for the info but im still a bit confused.

Is there an equasion that I can use for the info you have all given me?

Cheers
Ben

 

[waross]

Apologies all.
My research into consumption was done some years ago in Canada. 13+ KWHr per Gallon Canadian or imperial would be about 11+ KWHr per Gallon US. All major emgines in the 50KVA to 500 KVA range did better than 13 KWHr per gallon Canadian but none reached 14 KWHr per gallon Canadian.
From the website of a major gen-set maker:
Fuel consumption data at full load with diesel fuel with specific gravity of
0.85 and conforming to BS2869: 1998, Class A2.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[benjho]

Hi guys,

Thanks a lot for the info but im still a bit confused.

Is there an equasion that I can use for the info you have all given me?

Cheers
Ben

 

[catserveng]

Most modern turbocharged high speed diesel engines have a BSFC of about 185 grams/bhp-hr, so using your generator example.

1700ekW /.94 (typical gen eff) = 1808bkW X 1.34 = 2423bhp

2423bhp X 185 (est BSFC) = 448255 grams/hr / 453.59 = 988 lbs/hr

Now get the specifications from the fuel you'll be using, you need to know the lbs/gal and the BTU/gal

As example, typical #2 diesel that used to be available in my area had an API number of 32, a specfic gravity of .865 and weighed 7.2 lbs/gal, the typical BTU content of that fuel was 127,000 BTU/gal, so using that info for your engine and the assumed BSFC,

988lbs/hr / 7.2 lbs/gal = 137 gals/hr

137 X 127,000 = 17,399,000 BTU/hr

A few notes,
Most newer engines are probably a little better than that on BSFC.
If it has a package mounted mechanical drive fan you'll need to account for that.
Most fuels in use today are lighter than I used (was an old standard for testing we used to do a few years ago).

Sorry all my math in US units, but you should be able to convert to metric if you need to. To get more accurate information you'll need to get with your manufacturer or dealer and get specific unit specifications. Of course most emissions data specification sheets provided for engines today list the target engine thermal input, as does most heat balance info.

Hope that helps, Mike L.

 

[benjho]

Thanks Mike, that a great help!!!

Very much appreciated!!

Ben