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Tuesday, April 02, 2013

Another Gas Turbine Cutaway

Since the Gas Turbine Cutaway post appears to be one of the most-viewed on the blog, here's another one.  This is a really odd design that Alstom came up with back in the 1980s. 

It's a pretty cool design, and it kind of reminds me of a model airplane engine.  This is the Alstom GT11N.  I think it puts out about 100 Megawatts.  What's interesting about this design is that combustion occurs outside of the turbine proper, in a "silo combustor". 

Air is drawn in at the right side in this picture, compressed in several stages, and then it flows up just inside the wall of the the large cylinder at the center.  This pre-heats the combustion air while keeping the inner combustion liner cool and preventing it from melting.  The air is blended with natural gas (or fuel oil) at the top of the silo combustor.  The fuel/air mixture is burned as it travels down in the silo, then the hot gases are routed into a donut called the hot gas casingthat spreads them all around the turbine shaft, where they are allowed to expand and drive the turbine.

Here is another picture (actually an advertisement) that shows some of the parts in the gas flowpath.
I don't know much more about this machine than this.  It doesn't appear to have been too successful commercially, because there isn't much on the web about them, and the axial combustion scheme appears to be the dominant technology.  Still, I thought this was a cool idea...


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