Turbine in plant simulation

[Drexl]

Hi,

I'm doing a general simulation of a power plant and was looking for a GENERAL model for the turbine. Basically the turbine is modeled as

P = em * et * ms * (hin - h'out)

P : Electrical power (kW)
em : Mechanical efficiency
et : Thermodynamic efficiency
ms : Steam mass flow (kg/s)
hin : Steam inlet enthalpy (kJ/kg) [Calc. from inlet pres/temp]
h'out : Ideal outlet enthalpy (kJ/kg) [Condenser pres, const. entropy]

The problem is of course that in order for this simple model to be of any use I need some way of estimating et, the thermodynamic efficiency of the turbine (a simple 0.7-0.85 is not enough).

I'm not looking at estimating the efficiency based on detailed turbine measures, but rather on general data such as size (MW), steam conditions etc.

So does anyone know any easily available papers or books on the subject?

thanks
Drex

 

[Romefu12]

If you are looking for a specific model of turbine to base your simulation on, for example a Westinghouse 501F or a GE 207FA –D11, those figures for estimated thermal efficiency under ISO conditions can be found in the manufacturer’s literature, or in specific modeling software such as Gate Cycle, other than that those figures are proprietary. The numbers (.4 -.85 ) are used in modeling of some of these units so I really don’t understand what other number for Thermal Efficiency you are looking for.

Romefu12

 

[Drexl]

Hi,

Thanks for answering.

No i'm not looking for efficiency of specific models, in order to get that I basically have to buy a turbine or some expensive modeling software.

What I would like to know is typical efficiencies based on size, type of turbine, inlet/outlet conditions, and operation condition (% of full load). Or at least some of these . This could be in table, graph or equation format.

The reason for the simulation is not performance guarantees or optimization of a specific plant, more a general investigation of different set-ups with very varying conditions.

Examples of questions I would like to be able to answer is:
1) What would be a typical efficiency of a 20 MW turbine with inlet 500C/70barg and outlet 0.1 bara?
2) What would the typical efficiency of a similar turbine as above but with an extraction at 5 bara with a massflow of 2 kg/s
3) Same as above but inlet temperature 300C
4) If I run any of the above turbines on 30% steam flow, how would efficiency change?
5) How would efficiency change based on extraction flow?

Many of the above question are maybe too much to ask for, but still using 0.75 for all turbines regardless of size and operating conditions gives bad simulation results.

 

[PersonalProfile]

Have you considered contacted a / couple of suppliers?
Regards,
Lyle

 

[Drexl]

Hi
At this point I would have to contact a lot of suppliers for a whole lot of different models to get any kind of useful data.
My experince from turbine suppliers is that they are not the least interested to answer any questions (except for time between their tender and the signing of the contract).
I'm a bit surprised to find that this is such a difficult question.

Drex

 

[stgrme]

Although it will not answer all of your questions on steam turbine performance, I suggest that you obtain a copy of "Marks' Standard Handbook for Mechanical Engineers". I have an older edition (9th) with a copyright date of 1987. In my edition, Section 9.4 is devoted to steam turbines. (I presume that later additions will also include a similar section.)

This section includes a table of turbine efficiency for mechanical drive steam turbines up to 20,000 kW with varying inlet steam conditions. Other tables include representative heat rates for large (utility type) fossil and nuclear steam turbines. In my edition, the heat rates for the large turbines may be somewhat out of date due to the advancements in 3D flow analysis since the section on steam turbines was written. A later addition may include updated information.

You may also find other sub-sections of Section 9 on power plant heat excahngers (condensers and feedwater heaters) and other auxiliary equipment helpful.

You may be able to preview the latest edition at the on-line web sites of some book sellers. If the latest edition is too costly, you may be able to find used copies at some auction web sites.

Best of luck!