GE set new record efficiency for a combined cycle

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I'm not sure about the error in tip speed. If they quote 1200 MPH for tip speed, I tend to believe them. It would be a Mach number closer to 1.6 than 1.5, depending on the air temperature one would use as standard. But if this is a gas turbine derived from a subsonic airliner engine, why would the blade speed be supersonic?
 
In addition to the above, wouldn't it also be considered problematic to determine the speed of sound under the conditions the turbine blades themselves face? It's one thing to compare them to the speed of sound at ambient temperatures and pressures, but in the blades; well, that's why they have Mach numbers, isn't it?
 
I think that's the key to the problem. Who knows the turbine inlet temperature to the last stage of a GE combined-cycle turbine? Arcane knowledge for sure. I would guess ~900C. But the speed of sound would be much higher at 900C than at 20C, and would possibly lower the Mach number to subsonic.
 
Originally Posted By: A_Harman
I'm not sure about the error in tip speed. If they quote 1200 MPH for tip speed, I tend to believe them. It would be a Mach number closer to 1.6 than 1.5, depending on the air temperature one would use as standard. But if this is a gas turbine derived from a subsonic airliner engine, why would the blade speed be supersonic?


I'm going with this thought too. I'm betting they are simply stating the tip speed in mph/kph and the Mach number is probably reference close to sea-level (761.2 mph) to give it that 'wow factor'. That would correlate with their stated Mach number.

They should have left the Mach number out all together to prevent confusion. The tip of the blades are physically traveling at that speed regardless of the gas conditions they are running in.
 
Yep, the long, long last stage blades have enough problems with resonance as it is without introducing supersonic shock waves to them...they would NEVER go supersonic.

Speed of sound at the GT outlet being much hotter has a higher speed of sound...the blades are clearly subsonic....faster than a .22 bullet would work...
 
Originally Posted By: Shannow
Originally Posted By: A_Harman
But if this is a gas turbine derived from a subsonic airliner engine, why would the blade speed be supersonic?


Power turbines have moved SO far away from when I was doing perfomance testing on the old GE 25MWs 25 years ago...

https://powergen.gepower.com/content/dam...-sheet-2016.pdf


Holy shammoly, Jesus, Mary, and Joseph, that's some serious power.

519 MW = 519,000 kW = 695,000 HP. And that's just simple cycle output. Gas turbine cycle efficiency of 42%.

Combined cycle output is 50% higher.
 
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After performing an upgrade of one of the steamers that I've worked on, we wrung it's neck...best number I could get out of it was 747MW
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Originally Posted By: Shannow
After performing an upgrade of one of the steamers that I've worked on, we wrung it's neck...best number I could get out of it was 747MW
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Just had to hit 1,000,000 HP, didn't you?
 
Originally Posted By: turtlevette
Burning natural gas is not very exciting. Its easy and boring.

Natural gas should be saved for home heating and transportation.

Agreed wholeheartedly turtlevette, we should be using the fuels with the highest utility for distributed use.

Now that Oz has committed to sell 4 times as much NG overseas than our entire domestic consumption, we have a battle between NG prices and wholesale power prices that simply shouldn't be there (IMO)
 
That and black coal for domestic use competes with the export price.
I was poking around your country the other night. A 5,500 km Dingo fence?
 
userfriendly,
back in the day, the coal mines for the power stations were govt owned, as were the stations.

These days the power industry is competing on the global market to buy local coal.

Funny that you mention the dingo fence, as there are dingoes either side of it...and funny to in the conversation, as a few years ago, I had to go to the big smoke to "sell" my portfolio in the G.S. offices when we were being privatised...I nearly hit a dingo on the way down, crossing the Bell's Line of Road.

and again in the way home, with a passenger as witness...didn't see the Yowies 'though.
 
I can't imagine Donald Trump's gringo fence working any better, unless he takes away all their shovels.
If Dingo can go under a fence, so can Zorro. (fox)
 
How Gas Turbine Power Plants Work

http://energy.gov/fe/how-gas-turbine-power-plants-work

Quote:
One of the major achievements of the Department of Energy's advanced turbine program was to break through previous limitations on turbine temperatures, using a combination of innovative cooling technologies and advanced materials. The advanced turbines that emerged from the Department's research program were able to boost turbine inlet temperatures to as high as 2600 degrees F - nearly 300 degrees hotter than in previous turbines, and achieve efficiencies as high as 60 percent.

Another way to boost efficiency is to install a recuperator or heat recovery steam generator (HRSG) to recover energy from the turbine's exhaust. A recuperator captures waste heat in the turbine exhaust system to preheat the compressor discharge air before it enters the combustion chamber. A HRSG generates steam by capturing heat from the turbine exhaust. These boilers are also known as heat recovery steam generators. High-pressure steam from these boilers can be used to generate additional electric power with steam turbines, a configuration called a combined cycle.

A simple cycle gas turbine can achieve energy conversion efficiencies ranging between 20 and 35 percent. With the higher temperatures achieved in the Department of Energy's turbine program, future hydrogen and syngas fired gas turbine combined cycle plants are likely to achieve efficiencies of 60 percent or more. When waste heat is captured from these systems for heating or industrial purposes, the overall energy cycle efficiency could approach 80 percent.
 
Originally Posted By: SHOZ
How Gas Turbine Power Plants Work

http://energy.gov/fe/how-gas-turbine-power-plants-work


Thanks for the refresher...like the G.E. machine is doing ...low 60s.

Your 80% that you've quoted in the other thread and used this same puff piece to support is ONLY when combined with district heating and the like.

Otherwise you are stuck with plain old thermodynamic heat rate...and most of the CCGTs are NOT being put in population centres where district heating is remotely viable.
 
Originally Posted By: Shannow
Originally Posted By: SHOZ
How Gas Turbine Power Plants Work

http://energy.gov/fe/how-gas-turbine-power-plants-work


Thanks for the refresher...like the G.E. machine is doing ...low 60s.

Your 80% that you've quoted in the other thread and used this same puff piece to support is ONLY when combined with district heating and the like.

Otherwise you are stuck with plain old thermodynamic heat rate...and most of the CCGTs are NOT being put in population centres where district heating is remotely viable.
So you view is ~60% will not be topped as far as efficiency for Nat Gas?
 
Originally Posted By: SHOZ
How Gas Turbine Power Plants Work

http://energy.gov/fe/how-gas-turbine-power-plants-work

Quote:
One of the major achievements of the Department of Energy's advanced turbine program was to break through previous limitations on turbine temperatures, using a combination of innovative cooling technologies and advanced materials. The advanced turbines that emerged from the Department's research program were able to boost turbine inlet temperatures to as high as 2600 degrees F - nearly 300 degrees hotter than in previous turbines, and achieve efficiencies as high as 60 percent.

Another way to boost efficiency is to install a recuperator or heat recovery steam generator (HRSG) to recover energy from the turbine's exhaust. A recuperator captures waste heat in the turbine exhaust system to preheat the compressor discharge air before it enters the combustion chamber. A HRSG generates steam by capturing heat from the turbine exhaust. These boilers are also known as heat recovery steam generators. High-pressure steam from these boilers can be used to generate additional electric power with steam turbines, a configuration called a combined cycle.

A simple cycle gas turbine can achieve energy conversion efficiencies ranging between 20 and 35 percent. With the higher temperatures achieved in the Department of Energy's turbine program, future hydrogen and syngas fired gas turbine combined cycle plants are likely to achieve efficiencies of 60 percent or more. When waste heat is captured from these systems for heating or industrial purposes, the overall energy cycle efficiency could approach 80 percent.


How old is this article? 2600F turbine inlet temperatures were achieved with single-crystal film-cooled turbine blades back in the late 1980's. I worked on an advanced gas turbine project at Allison Gas Turbine back in the early 80's that targeted over 3000F. Also, combined cycle powerplants were already being installed by Allison back then as well. Only back then, it was called cogeneration.
 
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