Gas turbine

the high efficiency is related to many factors like the kind of Gas to get the max BTU

,the turbine stracture i mean the metals the turbine has been made and the most importan thing that i alwasy thinking about that is the ,how to make use of max heat the is generated while we consumpt the Gas i mean that now only (33 to 35)% use of Gas engergy we use in our plant and we wast at least 70% of Gas energy so let us first seek the way of useing or getting max engery of gas when it consumpt so when we fix these issues i sure that we can do easyly the capital cost,the flexible in operation and the completely reliable and ather accepects

Mr Bakatash points out very significant aspects to be considered first: 1) finding the kind of fuel gas to get the maximum BTU, 2)how to make use of maximum heat that is generated, 3) minimising wastage of gas.

While attempting to fix these issues, let us also examine improved technology options.

It is reported that "Compressed air energy storage technology" uses low-cost, off-peak power to pressurize and store air that can later be expanded through a gas turbine during on-peak periods.

In this technology,the compression and generation units are in separate configuration. (In the conventional Gas turbine and Combined cycle operation, both compression and generation are on a single shaft and must work together). Using low cost off-peak electricity to run the compressor, enables economic utilisation of power developed by gas turbine to generate electricity during critical peak hours.

Views on this and other suggestions are requested.

Given that fuel gases are petroleum derivatives and hence from a non-renewable source, wouldn't it be more useful to determine how to arrange the engine to get the maximum BTU's out of whatever fuel is used, rather than adjusting the fuel mix of conventional fuels to obtain more BTU's?

For example, if the Turbine is run on methane, ethanol, or other renewable-resource derivatives, how can the turbine be reconfigured to (a) lower the current efficiency compression ratio of 22:1 and thus avoid premature combustion from some of the more volatile manufactured gases, and (b) while still obtaining the max power efficiency for whatever fuel is used to the drive shafts (before the waste heat take-off for the steam turbines)?

For example, might the combustion phase of the g.t. cycle be introduced in earlier "softer" stages and enhanced through additional h.p. air-entraned fuel injection at the later stages?

It seems to me that since these types of engines exhibit more raw power than others, the world is going to become dependent on them and other varieties of relentless IC engines run on friendly fuel sources to replace nuclear and hydro when those types of electrical generation engines (water & steam turbine) are being considered for replacement due to the environmental harm caused by their power sources.

Unless they have been configured to run as efficiently as possible on alternative -or any available- fuels, they won't maintain their ability to compete with alternative energy production facilities either.

Mark

Hi Mani, CAES(Compressed Air Energy Storage) would indeed complement your basic set-up very well, also, I presume a CHP that utilises 'waste(sic)' heat a given. However I would like to draw your attention to the following practical limitations, vis-a-vis, first cost, maintenance cost, know-how, etc.

as per example posted by Keith, you're looking at a very expensive set-up with highly specilised, and proprietary, maintenance regime., and specially prepared/treated fuel to boot!

If you observe carefully, almost 75% of medium passing thru' a gas turbine does not participate in the combustion process, not only that, it actually contributes to pollution. I talking about nitrogen and other trace gases.

Imagine, an externally heated compressed air supply to a power turbine. First, you could press the medium(normal air or nitrogen) to a pressure, which upon complete expansion, brings the final medium/gas temperature to near atmospheric condition!

As for the 'gas turbine', all you need is a power turbine - and since it doesn't require a built-in combustor or compressor, this could be made in a cantilever arrangement, with support/bearings well away from the hot zone.

Heat source; you don't need nitrogen for combustion!, and given the size of a typical power plant, the total air mass flow thru' such systems could easily justify the cost of air distillation plant.(It is this nitrogen that could serve as working medium). So, what you need is an oxy-fuel burner based heat exchanger which, in one clean sweep, also serve as a multi-fuel burner.

Given the flexibility in sizing each of the components, this also easily lends itself to scalability, i.e.: 2 dozen units versus a single multimillion dollar unit. Also, with larger number of smaller units, the turbines could be operated in on-off mode.

Gas turbine efficiency is pretty closely related to the compression ratio and expansion ratios ---the Carnot cycle efficiency is very close. Material temperature limits define the maximum compression ratio that can be achieved without blade failure in the expansion turbine. Another limit is the pressure at which the fuel is available. The most modern gas turbines operate with compression ratios of 22:1.

GE's latest lines of aero-derivative and large-frame (industrial) gas turbines are achieving very high efficiency in combined cycle (gas turbine-steam turbine) electricity generation. There have been durability issues (or rather availability factors) not meeting performance warranties--but further materials and blade manufacturing development seem to have solved those. The 'hot' blades in the expander section are extremely sophisticated with convoluted internal cooling passages and 'leading edge' cooling medium ejection ports in attempts to lower the metal temperatures--this is the performance limiting issue--hot hot can one run the combustion chamber and first expansion stages before they burn-up?

You are all right, but air inlet lower Temp and inlet air filter low diff press will also improve eff.

for 1st thing cooling/fogging is useful .

For 2nd thing,high eff filters AAF are useful.

HABIB

Combined cycle is other best way to reduce the heat losses and improve eff

HABIB

Out of curiosity, can you give a figure for efficiency? Shaft power to thermal input. Also efficiency of the gas turbine on its own? If I had to guess I'd say ~ 25%, but it's only a guess.

Cheers..........Codey

GE manufactured gas turbine driven generators with the heat from the exhaust running steam turbines. about 100 of these units were made in Durham, NC and shipped to Japan. This happened around 1980. I was an engineer at the plant "Durham" that made the boilers.

these systems have been around since the 1950's, back when the pressure ratio was only 4 to 1... Rover's car /truck turbines achieved 0.4lb fuel per HP Hr 9 as compared to say norton's motorcycle racing engine which uses 0.5 lb/hp hr. Rolls Royce have been selling the marine version of their RB211/Trent series engines for years. The biggest advantage being instant full power response.

I've been contemplating lowering the turbine ilet temperature by spraying water into0 the post combustion space. in theory this will decrease the turbine inlet temperature and increase the pressure or gas velocity allowing higher power absorption by the turbine sections. teh exhaust should also be cooler without the need for heat exchangers.

Another concept is to use external heating via a heat exchanger running stirling or ericson cycle. This allows persurisation of the whole system for high efficiency without high heat at turbine.

In reply to the Rover Truck/Car gas Turbine contribution, 0.4 lb/bhp hr compared poorly with its competitor, the Turbocharged Diesel with 0.35. Heat exchanger Seals were the main reason that this difference could not be narrowed, and hence the demise of the Turbine Truck, unfortunately. Can this problem be solved with modern technology?

The point about external cycle engines is a good one, and modern versions of this type of units is just around the corner after 150 years!