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Re: [GMCnet] interesting new engine design [message #67777 is a reply to message #67767]

Fri, 18 December 2009 16:55

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

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ljdavick wrote on Fri, 18 December 2009 14:09

<snip>
I've always wondered why turbines weren't more prevalent for generating electricity on small sites. I had always tought that big diesel motors powering generators would be less efficient than small natural gas powered turbines. But then, I'm just guessing!

Larry Davick
The Mystery Machine

Larry,

There is a very simple fact that has kept gas turbines flying and not sitting still. (An exception will be noted after the relevant discussion.)

Gas turbines have one big feature, very high power to weight ratio. They also have two very large considerations, very high cost to manufacture and really poor (high) part load fuel rate.

Diesel engines have two big features relatively inexpensive to manufacture and very good part load fuel rate. Diesel engines have one consideration, low power to weight ratio.

The cost to manufacture a gas turbine is so high that when a "hot section" job - replacing all the parts that see fire - has to be done, it is just a little cheaper than buying a new power unit (engine).

The internal parasitic loads on a gas turbine do not decrease with output power. This is such that one unit we were mapping had a fuel rate at idle that was just a little less than 3/4 of the full power fuel rate. At design load, the unit had a fuel rate that was diesel-like (0.48#/shp-hr). Diesels almost don't use fuel at idle and that scales through the load curve.

Small gas turbines were starting to show up in the early 70's. Fuel was not a big cost issue until the first oil scare (learned a lot - haven't we?). Solar, Williams, Paxton and Air Research were a few of them. The military bought them and may still.

The exception that I promised to mention.
There have been more than a few recent gas turbine electric plants built all over the country (well, anyplace natural gas is economically available). These are installed as "All or Nothing" peak load units. As they are acceptably fuel efficient at design load, that is the only place that they are used. The local grid still has to be balanced with steam or hydro that does not take a beating to run at part load.

I really tried, but if you can't understand my answer, just tell me and I will try again.

Matt Colie

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

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[Message index]

		interesting new engine design By: fred v on Wed, 16 December 2009 21:34
		Re: interesting new engine design By: hertfordnc on Wed, 16 December 2009 22:29
		Re: interesting new engine design By: ljdavick on Wed, 16 December 2009 22:47
		Re: interesting new engine design By: Chr$ on Wed, 16 December 2009 22:43
		Re: [GMCnet] interesting new engine design By: Gary Casey on Thu, 17 December 2009 06:45
		Re: interesting new engine design By: fred v on Thu, 17 December 2009 07:44
		Re: [GMCnet] interesting new engine design By: GMC_LES on Thu, 17 December 2009 10:32
		Re: [GMCnet] interesting new engine design By: ljdavick on Thu, 17 December 2009 10:53
		Re: [GMCnet] interesting new engine design By: hertfordnc on Fri, 18 December 2009 06:16
		Re: [GMCnet] interesting new engine design By: mike miller on Fri, 18 December 2009 06:36
		Re: [GMCnet] interesting new engine design By: fred v on Fri, 18 December 2009 06:52
		Re: [GMCnet] interesting new engine design By: Gary Casey on Fri, 18 December 2009 07:11
		Re: [GMCnet] interesting new engine design By: USAussie on Fri, 18 December 2009 12:37
		Re: [GMCnet] interesting new engine design By: Steven Ferguson on Fri, 18 December 2009 08:18
		Re: [GMCnet] interesting new engine design By: GMC_LES on Fri, 18 December 2009 08:29
		Re: [GMCnet] interesting new engine design By: ljdavick on Fri, 18 December 2009 10:47
		Re: [GMCnet] interesting new engine design By: jhb1 on Fri, 18 December 2009 12:18
		Re: [GMCnet] interesting new engine design By: ljdavick on Fri, 18 December 2009 13:09
		Re: [GMCnet] interesting new engine design By: Matt Colie on Fri, 18 December 2009 16:55
		Re: [GMCnet] interesting new engine design By: ljdavick on Fri, 18 December 2009 19:07
		Re: [GMCnet] interesting new engine design By: Matt Colie on Sat, 19 December 2009 09:11
		Re: [GMCnet] interesting new engine design By: comcast on Sat, 19 December 2009 09:58
		Re: interesting new engine design By: Matt Colie on Thu, 17 December 2009 07:54
		Re: interesting new engine design By: Matt Colie on Fri, 18 December 2009 09:55
		Re: interesting new engine design By: fred v on Fri, 18 December 2009 12:53
		Re: interesting new engine design By: Bob de Kruyff on Fri, 18 December 2009 14:27
		Re: interesting new engine design By: Bob de Kruyff on Fri, 18 December 2009 19:48
		Re: interesting new engine design By: mdryan on Fri, 18 December 2009 10:03

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