tailieunhanh - Advanced Gas Turbine Cycles Episode 4

Tham khảo tài liệu 'advanced gas turbine cycles episode 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 38 Advanced gas turbine cycles s Fig. . diagram for irreversible closed recuperative cycle CHT . and the thermal efficiency is y a l - 1 x - x - - 1 x 1 - e 3 - x or y ớ l - l xT - xc- D e0 l - l xT l -fi 0-xc . Optimum conditions and graphical plot The isentropic temperature ratio for maximum efficiency xe is again obtained by writing 9-ụ âx 0 after some algebra this yields A xe 2 tíx Ơ 0 where A 1 - a - 3 1 fi -2a l- c a 0 - 3 1 . For the CHTXh plant with the cycle parameters quoted above for the CHTJi plant i with the values of X for maximum efficiency and maximum work become identical xe xw al 2 and y ii with xc xw and y . For their graphical interpretation Hawthorne and Davis wrote NDHT q cp Tj - T e NDNW A where AI 2e 1 NDCW 1 and the efficiency as 7 NDNW NDHT AJ NDN W 1. The graphical representation is not as simple as that for the CHT j cycle but still informative. It is also shown in Fig. which gives a plot of the CHTXJj efficiency against X for the parameters specified earlier and for . The term in the square Chapter 3. Basic gas turbine cycles 39 brackets A in Eq. is linear with X passing through the X y points 0 1 1 fi 3 l 2 1 2 where 1 - 3 - 1 1 - e 2e - 1 . The effect of varying can also be interpreted from this type of diagram. For . for a cycle CHT Xr the maximum efficiency occurs when r the square bracket line becomes tangent to the NDNW curve at A . For high values of greater than the tangent meets the curve to the left of the maximum in NDNW whereas for low the tangent point is to the right. For the point 0 is located at -00 and the square bracket line becomes horizontal touching the NDNW curve at its maximum at r rw so that for re rw. . Discussion The Hawthorne and Davis approach thus aids considerably our understanding of a s plant performance. The main point brought out by their graphical construction is that the maximum .