The Research On Key Technology Of Control Of The Turbo-expander

In the field of cryogenic technology,turbo-expander is an extremely important traditional energy-technical equipment.As the heart of the machinery for air separation,turbo-expander makes it run economically with the reasonable regulation to isentropic efficiency and refrigerating capacity.Since the traditional extensive mode of control is no longer suitable for the era theme of high efficiency and energy saving for turbo-expander,it is necessary to find a more reasonable control strategy and to use the advanced control algorithms in the optimal control of turbine expander.The improved control strategy for refrigeration of turbo-expander achieves the higher isentropic efficiency with the optimal rotary speed and the decoupling of the quality control and the quantity control on cooling capacity by the cooperation of the braking effect of fan butterfly valve and the adjustment of rotating nozzle blade assembly in the concrete implementation scheme,which realizes a precise control of the cooling capacity by using generalized predictive control.The main works in this paper as follow:(1)Aiming at the defective solution of the isentropic efficiency in the traditional control of turbo-expander,a method is proposed to maintain the higher isentropic efficiency with improved optimal rotary speed.Firstly,the corresponding relationship between the maximum isentropic efficiency and the best characteristic ratio is obtained by analyzing the characteristic curve of the turbo-expander;Secondly,the relationship between isentropic efficiency and rotor speed is gained at different temperatures,through the combination of the definition of the best characteristic ratio,the various parameters and the law of thermodynamics.Finally,the relationship between the optimal rotary speed and the temperature drop is received under the condition of large isentropic efficiency by the relationship between rotary speed and isentropic efficiency.According to this relationship,we can get the larger isentropic efficiency in engineering practice.(2)In allusion to the strong coupling of the traditional control of the turbo-expander in the cooling-capacity regulation,the improved control strategy and implementing scheme of cooling capacity is proposed,which is to maintain a large isentropic efficiency with the control of the improved optimal rotary speed and to achieve flow control with the adjustment to rotating nozzle vane.Specifically you can control the fan outlet valve and the nozzle valve to complete the regulation of speed and flow,respectively.The strategy achieves economical refrigeration relatively by the auxiliary regulation of the expansion volume under the premise of maintaining the larger isentropic efficiency.Therefore,the control of refrigerating capacity can be more easily and precisely,which is independent of each other on quality and quantity.(3)On account of the optimal control of the improvement strategy of the turbo-expander,the optimal opening,the optimal rotary speed and the optimization control model of cooling is obtained,based on the characteristic analysis of the control valve,the law of the proportion of fans and the design parameters of the specific turbo-expander.At the same time,this model of refrigeration is simulated by Generalized Predictive Control algorithm,and a satisfactory optimization control effect is achieved.