Research On Reciprocating Compressor Performance At Off-Design Condition

Reciprocating compressors have a wide range of applications in the petroleum and chemical industries. With on-going changes in petrochemical processes, there is a need to apply capacity regulation systems to these compressors. Partial unloading capacity regulation method is one effective means of achieving this. It can cause the power consumption to reduce in proportion to the decrease in capacity. To enable the widespread application of this method, it is necessary to analyse the changes in the performance of a reciprocating compressor while its capacity is being regulated. In this paper, the thermodynamics, dynamics and kinetics status of reciprocating compressor at off-design condition were deeply studied. The analysis conclusions provide a theoretical support for determination of the regulation program and ensure the compressor’s safe operation.The main study results are as following:1) On the basis of thermodynamic calculation, the capacity formulation of reciprocating compressor at off-design condition was deduced. The capacity formulation is much more accurate and concise than former ones. Based on MATLAB GUI functionality, the user interface was designed and a feasible method was provided for quickly, accurately determination of the passive regulation program.2) The influence of capacity regulation on reversal angle in a reciprocating compressor was evaluated. Based on synthesis force curves, the reversal angles for different capacities were calculated and compared for an M-type reciprocating compressor. The calculated results demonstrate that, for a compressor for which the designed reversal angles are sufficiently large to ensure good lubrication for pin and bushing, capacity regulation could guarantee its safe operation.3) On the basis of comparative analysis of theoretical calculation and engineering simulation, the kinetics and dynamics characteristics of reciprocating compressor at off-design condition were thoroughly analysed. The analysis results show that, capacity regulation has little effect on kinematics performance. If the multistage cylinders are regulated synchronously without changing the mode of cylinder acting, the moving components load would be less than design condition, there is no need to do further security check; If the double-acting cylinder is caused into a single-acting mode, the moving components load would increase. The strength of key components should be checked.4) The potential fault of compressor at off-design condition was analyzed and estimated in detail. The corresponding method was put forward to avoid failure.