The stepless flow control system offers important energy-saving technology for reciprocating compressors in the petrochemical and oil refining industries. Optimizing the movement characteristics of the unloader and suction valve is vital to improving the energy-saving level of the system and reducing the overall operating cost. However, the system has many of the characteristics of multi-system coupling and multi-parameter crossover; thus, it is difficult to optimize the key control parameters. In this study, to optimize the system inlet pressure, return pressure, and return spring stiffness parameters, a working model of the flow control system based on multi-system coupling was established. Using the ejection and withdrawal speeds of the unloader, the flow displacement deviation, and the gas work deviation of the control system as the optimization parameters, we used the response surface method to establish an optimization proxy model between the objective function and key parameters. Additionally, verification of the model’s accuracy and sensitivity analyses were completed. Finally, a double optimization scheme based on a non-dominated genetic algorithm (NSGA-II) was proposed. Simulation and experimental results show that with optimization of the return spring, oil inlet pressure, and oil return pressure, the unloader’s kinematic characteristics were also optimized at full load. The impact energy of the ejector and withdrawal speed of the unloader were reduced, and the compressor flow control error was less than 5%, which effectively improved the comprehensive working performance of the stepless flow control system.
The actuator is the key to the stepless capacity control system of a reciprocating compressor. The coupling effect between the actuator and the reciprocating compressor was not considered in the traditional design, and the large design margin led to low system reliability, high cost and low safety. In this paper, a reciprocating compressor and actuator were taken as research objects. The backflow clearance of the suction valve was simulated by CFD (computational fluid dynamics), The relationship between backflow clearance and resultant gas force of the valve plate was discussed. By building a mathematical model of actuators considering backflow clearance and impact rebound, the relationship between the parameters of actuators was studied. Based on the mathematical model and CFD analysis, the hydraulic force and spring stiffness were taken as the design variables, the impact velocity of ejection or withdrawal and the backflow clearance were taken as objective functions, and the actuator parameters were optimized with NSGA-II (Non-dominated Sorting Genetic Algorithm – II). The optimization results show that when the backflow clearance is 0.0065 mm, the hydraulic force is 94.25 N, and the spring stiffness is 11,575.84 N/m, the objective functions are optimized, the parameters are significantly improved, and a good effect is achieved on the experimental table of a 2D reciprocating compressor.
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