تجزیه و تحلیل عملکرد حرارتی از کمپرسور پیستونی با سیستم کنترل ظرفیت بدون مرحله

On the basic principle of stepless capacity control system for large reciprocating compressor, the thermal cycle was analyzed. The equations for the process of suction, reverse flow, compression, discharge and expansion of clearance gas were established. According to these equations, p–V diagrams at various situations were simulated. An experimental platform was setup and the compressor with designed stepless capacity control system run well. The experimental results show that the capacity of compressor can be regulated steplessly, and the motor power is reduced proportionally with respect to the reduction of capacity. During the suction process, both the flow resistance of valve and the pressure fluctuation in cylinder can be reduced by opening the suction valves with the actuators. The simulated and experimental results showed good coincidence. The clearance volume and valve clearance Mach number had a negative influence on the thermal performance of compressor with stepless capacity control system. Highlights ► Flow resistance of valve can be reduced and pressure fluctuation can be reduced. ► Equivalent Mach number of reverse flow is much higher than that of suction process. ► Response of stepless capacity control system is important for regulation accuracy. ► Clearance and valve clearance Mach number have influence on thermal performance.

Large scale reciprocating compressors have been widely used in the industries of chemical processing, gas transport and storage, refineries, and so on. During their operation, the capacity of compressor needs to be regulated in line with the actual demand of the chemical and petrochemical processes. Various approaches have been used to control the capacity of reciprocating compressors, and by-pass regulation is simple and reliable for large-scale reciprocating compressors. However, the method of by-pass regulation results in much power dissipation because the reflux gas is compressed again [1]. Compared with the by-pass regulation, the method of actively controlling suction valve motion, called stepless capacity control method too, has much better energy-saving performance just because only the gas needed is compressed in the compressing process [2], [3] and [4]. As this approach could make system more efficient, stepless capacity control system has been applied in large-scale compressors [5]. At present, researches on the stepless capacity control focus not only on the dynamic characteristics of suction valve [6] and how to realize the action of actuator [7], but also on energy-saving performance and economic efficiency both effected by compressor load and shaft power when the stepless capacity control is employed [8]. However, in those researches, fundamental theory and principle of the stepless control system were only qualitatively analyzed, not quantitatively calculated [9] and [10]. Qualitative analysis could not provide enough theoretic reference. In Ref. [4], the theoretical models of thermal circle with stepless capacity control in described did not consider the influence of actuator and the motion of valve. In this paper, theoretical models of thermal circle considering those effect factors were established and an experiment has been done to prove them.

In this paper, the thermal performance of an L-type air compressor has been studied by theoretical model and experiment. Based on the theoretical and experimental investigations, the following conclusions can be obtained. The stepless capacity control system can meet the demand of capacity regulation of large reciprocating compressor. The capacity can be regulated automatically according to the actual needs by the system, and at the same time, the power decreases with the decrease of capacity. During the suction process, both the flow resistance of valve and the pressure fluctuation in cylinder can be reduced by opening the suction valves with the actuators. The equivalent Mach number of reverse flow process is almost 0.3, which is much higher than that of in suction process. So redesigning the suction valve for a lower reverse flow resistance is very effective for improving the efficiency of compressor. The clearance volume and valve clearance Mach number had a negative influence on the thermal performance of compressor with stepless capacity control system.