An optimal control of start-up for nonlinear fire-tube boilers with thermal stress constraints

2019 ◽  
Author(s):  
Stefano Spinelli ◽  
Marcello Farina ◽  
Andrea Ballarino
Keyword(s):  
Optimal Control ◽  
Thermal Stress ◽  
Stress Constraints ◽  
Start Up

Distributed Parameter Optimum Control of a Nuclear Rocket With Thermal Stress Constraints

1967 ◽  
Vol 89 (2) ◽  
pp. 300-306 ◽  
Author(s):  
D. L. Briggs ◽  
C. N. Shen
Keyword(s):  
Optimal Control ◽  
Thermal Stress ◽  
Flow Rate ◽  
Thermal Stresses ◽  
Control Level ◽  
Control Program ◽  
Bilinear System ◽  
Stress Constraints ◽  
Stress Constraint ◽  
Nuclear Rocket

The problem considered here is that of controlling the flow rate through a nuclear rocket such that temperature gradients in the fuel elements, and the corresponding thermal stresses produced, do not exceed specified values. The desired control program is that which takes the system from steady-state conditions at a given flow rate to a higher, specified flow rate in minimum time without violating the thermal stress constraints. The system equations here are a pair of coupled, first-order, bilinear, partial differential equations and the thermal stress constraint is proportional to a product of state and control variables. By analyzing both the solution for a step in control and the coupling between control level and time response in the bilinear system, the form of the optimal control is deduced. It is shown how the optimal control law can be generated using a digital computer. Numerical results are given.

Coordinated Control of Gas and Steam Turbines for Efficient Fast Start-Up of Combined Cycle Power Plants

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Yasuhiro Yoshida ◽  
Kazunori Yamanaka ◽  
Atsushi Yamashita ◽  
Norihiro Iyanaga ◽  
Takuya Yoshida
Keyword(s):  
Thermal Stress ◽  
Steam Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Thermal Stresses ◽  
Control Method ◽  
Coordinated Control ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Start Up

In the fast start-up for combined cycle power plants (CCPP), the thermal stresses of the steam turbine rotor are generally controlled by the steam temperatures or flow rates by using gas turbines (GTs), steam turbines, and desuperheaters to avoid exceeding the thermal stress limits. However, this thermal stress sensitivity to steam temperatures and flow rates depends on the start-up sequence due to the relatively large time constants of the heat transfer response in the plant components. In this paper, a coordinated control method of gas turbines and steam turbine is proposed for thermal stress control, which takes into account the large time constants of the heat transfer response. The start-up processes are simulated in order to assess the effect of the coordinated control method. The simulation results of the plant start-ups after several different cool-down times show that the thermal stresses are stably controlled without exceeding the limits. In addition, the steam turbine start-up times are reduced by 22–28% compared with those of the cases where only steam turbine control is applied.

Turbine Start-Up Algorithm Based on Prediction of Rotor Thermal Stress

1996 ◽  
Vol 29 (1) ◽  
pp. 6867-6872 ◽  
Author(s):  
Akimasa Nakai ◽  
Masashi Nakamoto ◽  
Atsuyuki Kakchi ◽  
Shinji Hayashi
Keyword(s):  
Thermal Stress ◽  
Start Up

scholarly journals Optimization on start-up process of high-pressure rotor for large power steam turbine

2016 ◽  
Vol 20 (suppl. 3) ◽  
pp. 815-822 ◽  
Author(s):  
Qiu-Wan Du ◽  
Zhao-Li Zheng ◽  
Yong-Hui Xie
Keyword(s):  
Thermal Stress ◽  
Time Allocation ◽  
Thermal Structure ◽  
Equivalent Stress ◽  
Pattern Search ◽  
Transient Temperature ◽  
Obvious Effect ◽  
Large Power ◽  
Start Up ◽  
Maximum Equivalent Stress

This paper combines thermal-structure coupling technique and pattern search optimization algorithm to establish an optimization system for the start-up process of a turbine unit. Firstly, a finite element model for thermal-structure coupling calculation is established to accurately analyze the transient temperature field and thermal stress field, which can obtain the thermal stress distribution during start-up process. Afterwards, a program of optimization on rotor start-up process is exploited to improve the time allocation in each operating stage of start-up process, which minimizes the maximum equivalent stress of rotor. The maximum equivalent stress has reduced 25.7% after the optimization, which reveals obvious effect.

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