a little confused about an example on combined cycle calculation

[FanCG]

actually speaking, this thread should not be posted here. it is just calclulation method on combined cycle (thermodynamics).

I read an example on combined cycle recently. The calculation procedure considers the effect of fuel composition on thermal efficiency. when I did this calculation following the example, I found that the final efficiency would be greater than 100% if air surplus coefficient was large enough. Could anybody here tell me the reason?

p.s. I use trial and error method to estimate some parameters in the worksheet, but it is manually, can I do it automatically in mathcad?

thx

the mcd file is v11

[ValeryOchkov]

May be this

http://twt.mpei.ac.ru/MCS/Worksheets/PTU/PGU-eng.xmcd

will be interecting for you.

See the screenshot of this Mathcad-Web-Sheet:

[ValeryOchkov]

One example calculation of the gas mixture in the gas turbine of the Braiton thermal Cycle on Mathcad Server:

http://twt.mpei.ac.ru/MCS/Worksheets/PTU/Vv-9eng.xmcd

[FanCG]

I think this answer will be more helpful to my confusion than your last answer. what confuses me is when I change the air surplus ratio to a higher value than what is given in this example, the efficiency based on the lower heating value of the fuel will exceed 100%. I m not sure whether it is right in this book.

I will study your example a few hours later . many thanks

[ValeryOchkov]

Thanks for the interest on my example.

See too

WaterSteamPro for Mathcad >>>

this article >>>

and this part of my Mathcad Server >>>

[FanCG]

I m studying this file now (http://twt.mpei.ac.ru/MCS/Worksheets/PTU/Vv-9eng.xmcd), up to now, I think maybe my fault lies on the pre-assumption of air coefficient alpha. I will redo my calculation following this example to see whether the error I mentioned above will appear again.

ps. I think that the section "humidity ratio of air " gives a wrong unit, should it be kg/kg?

[ValeryOchkov]

Fan CG wrote:

ps. I think that the section "humidity ratio of air " gives a wrong unit, should it be kg/kg?

See properties of humid air as function of temperature and moisture g H₂O/kg dry air:

http://twt.mpei.ru//MCS/Worksheets/rbtpp/eng/tab26.xmcd

The screenshot

[FanCG]

yes, you are right. But by what I mean is as following:

I think maybe it is wrong

[ValeryOchkov]

Fan CG wrote:

yes, you are right. But by what I mean is as following:

I think maybe it is wrong

Thanks!

I have corerected the Mathcad-Web-Sheet on the server!

PS

This is one of the advantages of Mathcad Server!
If I will send the usual Mathcad-Sheets to users, and then find a mistake, I can not fix it.