The Research Of Operation For 600MW Sub-critical Turbine During Sliding Parameter Shutdown Process Based On The Safety And Economy

The Research of the safety and economy for large-scale steam turbine unit in the Peak shaving operation process has been focused on.Increasing the main steam temperat. drop rate during shutdown process can make the turbine quick stop, which can not only improve the economic benefit of running, but also get much more time for the unit maintenance. However, a quick shutdown correspondingly causes the rotor thermal stress increasing, which is not conducive to the safety operation of the unit. Aiming at this situation, this paper researched the main steam temperat. drop rate to determine the optimal solution during turbine sliding press. shutdown process, which meets the requirements of guarantee the rotor stress safety and improving the economy of shut-down processing.The sliding parameter shutdown process heat transfer coefficient change with the main steam physical parameters and the coefficient influences on heat transfer in some degree.Considering this situation,by using MATLAB software programming combined with water vapor physical properties, this paper calculated and outputted each part of the convective heat transfer coefficients of 600 MW sub-critical steam turbine high press. cylinder rotor during sliding parameter shutdown process.According to the normal sliding parameter shutdown curve, using finite element software ANSYS to simulate temperat. field and stress field distribution of steam turbine high press. cylinder rotor in shutdown process.The paper made different main steam temperat. drop rate schemes of shut down process.With the finite element method, the high press. cylinder rotor temperat.fieldstress field and the characteristics of the life loss of each temperat. drop rate schemes were analyzed.According to the safety index, define preliminary optimization schemes of security.In the safe operation schemes,the one which has the biggest value of economy index will be the best optimization operation solution. The results shows that:(1)When the turbine was shut down as normal slip parameters curve, with the increase of downtime, the main steam temperat. is reduced,the temperat. of high press. cylinder rotor also reduces.When T= 0 s- 8250 s, the highest temperat. of high press. cylinder rotor reduces from 537.6 ℃ to 500.9 ℃,which appears at the rotor hub.The longer the downtime is, the more obvious of phenomenon that rotor spindle radial temperat. distributes layer by layer shows. The isothermal lines distribution of rotor surface is much dense than that of axis. The thermal stress values increase gradually with the shut down time goes much longer.During the period of T = 0s-8250 s,the maximum stress value of the high press. cylinder rotor increase from 160 MPa to 160 MPa.At the end of shut down time,the stress concentration phenomenon of the velocity stage root is most obvious.Also the research finds that the temperat. of the velocity stage root in the high press. cylinder rotor decreases with the shut downtime increasing, and which shows for a linear development trend; Stress value increases over time, and the increase velocity decreases gradually.There is no linear relation between stress and shutdown time.(2) when the optimization scheme temperat. drop rates of shut down are 1.5℃/min and 2.0℃/min, the high press. cylinder rotor maximum stress values of 361 MPa and 385 MPa respectively,which are much bigger than the allowable stress that is 358 MPa.Those two schemes can not guarantee enough security. When the optimization scheme temperat. drop rates of shut down comes to 1.2 ℃ / min, 1.3 ℃ / min, 1.4 ℃ / min, the maximum stress values are 338 MPa、349 MPa、355 MPa respectively, less than the allowable stress of material that is 358 MPa,those schemes can guarantee the safety operation. And the research shows that 1.45 ℃ / min is the critical temperat. drop rate for safety.(3) The economical analysis of the temperat. drop rates,which are1.2 ℃ / min, 1.3 ℃ / min, 1.4 ℃ / min,1.45 ℃ / min,has been made.The results shows that the saving Standard coal consumption quantity increases gradually,which are 31.00 t, 42.91 t, 53.14 t, 57.69 t respectively. The rotor loss costs converted into Standard coal consumption quantity rise,which are 0.1764 t, 0.1820 t, 0.1860 t, 0.1883 t respectively.The comprehensive economic index values are 30.8236 t, 42.728 t, 53.5017 t, 57.5017 t.(4) Based on economic analysis of sliding parameter shut down operationoptimization schemes, the economyindex of 1.45 ℃ / mintemperature drop ratescheme is the biggest, and it’s bigger than that of 1.2 ℃/min. The difference between them is 12.2%.The economy index of 1.45 ℃ / min temperature drop rate is the biggest, and it’s bigger than that of 1.2 ℃ / min shutdown plan.economy times numerical indicators.The difference between the two scheme is 21%. 1.45℃/min temperature drop rate scheme is the best one.