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Knock resistance rating for Natural Gas

Knock resistance rating for Natural Gas

(OP)
Greetings,
I am looking for the procedures to calculate the knock resistance rating for natural gases, required for Gas Engines °BTDC adjusting . Specifically, I need the calculation procedures for WKI (Waukesha Knock Index for Waukesha Gas Engines), Methane Number (Caterpillar Gas Engines) and n-Butane Number (White Superior Gas Engines).

RE: Knock resistance rating for Natural Gas

Have you tried asking the respective local dealers for this information?

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

RE: Knock resistance rating for Natural Gas

(OP)
I need the ecuations, i mean, the calculation procedure. I already have the WKI and Gas Engine Rating Pro (GERP), but I need to do a spreadsheet comparing all of these methods for knock resistance rating for natural gases

RE: Knock resistance rating for Natural Gas

That's a tall order. You are effectively asking for engine manufuacturers to divulge their hard-won intellectual property regarding fuel composition versus knock sensitivity.

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

RE: Knock resistance rating for Natural Gas

So why exactly? If you use the CAT program for a Jennbacher or Waukesha engine and have a problem likely it will be on you. I can't speak for other manufacturers but know the CAT Methane number program is validated in the engine labs and test cells, and if you have to make adjustments, use the calculator, that is why it is free to download.

Have you looked at this paper? http://www.google.com/url?sa=t&rct=j&q=&am...

This is the European Engine Manufacturers Association position paper on methane number calcs.

Mike L.

RE: Knock resistance rating for Natural Gas

(OP)
We have on a same Gas compressor plant more than 20 gas engine(Waukesha and Caterpillar and gas Engine and Solar Turbines) and the gas fuel source change frecuently, so it is important to update the ignition timing and that is why I want to use a single spreasheet to calculate Methane Number and WKI.

RE: Knock resistance rating for Natural Gas

You might try to generate a representative range of different composition cases, run them through the various calculators or lookup tables, then do a correlation in Excel to get the one-stop shopping spreadsheet you want. I mean, you could generate curves and use the curve coefficients to back calculate empirical calculations, which is what they are after all.

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

RE: Knock resistance rating for Natural Gas

KI for Natural gas varies wildly. Pure Methane is high, Natural gas with propane, butane and other "anes" has a lower KI. I have seen some cog samples that were not much better than 93 octane pump gas due to other heavy molecule junk in the fuel.

RE: Knock resistance rating for Natural Gas

That's true, and the OP seems to be quite aware of this. Basically, the OP is asking for the inner workings of the various OEM's knock rating/methane no. calculators, not the black box version, which seems to be readily available.

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

RE: Knock resistance rating for Natural Gas

A simple linear regression on a dozen different gas samples and results would work just fine.

I find it quite funny when the gas engine packager wants to know the composition of the fuel gas in our rich gas gathering system so they can set the engine up. I said it's the same as the composition that I gave 6 months ago for the last unit. The engineer gets all excited and says it can't be, this compressor is going to be 5 miles away from the last one. I try to explain to the kids that the composition changes every hour if not sooner.

RE: Knock resistance rating for Natural Gas

Please note that the WKI calculation is very different than the calculations generated by CAT GERP. The two should not be interchanged. The most commonly available method of calculating MN is the CARB method, easy but not very accurate, especially if you gas contains significant quantities of CO2, H2S, H2, or CO. The CAT GERP method matches measured MN better than most applications in my experience. They are releasing a new version that (version 5) that supposedly further improves the MN calculation. I've a paper comparing various MN calculation methods if anyone is interested. It was presented at the 2014 Gas Machinery Conference.

I've generated an open source method that very closely matches the measured MN data available in the public domain. It does have some limitations for 'producer gases' but should work well for most natural gas compositions. https://github.com/gchoquet/EngineControlSoftware/

RE: Knock resistance rating for Natural Gas

I forgot to mention that the Cummins Westport method uses the CARB method, I would only recommend using that method if you have a Cummins Westport engine. A better tool is the Cummins Gas Analysis Tool: https://quickserve.cummins.com/gas_analysis_tool/i... which provides answers similar to CAT GERP (Version 4).

RE: Knock resistance rating for Natural Gas

@gchoquet: could you post the title of the paper which compares the different MN calculation methods?

thank you very much.

RE: Knock resistance rating for Natural Gas

Error 404 - Not Found

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Knock resistance rating for Natural Gas

Thank you Jay.

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