Development of an Optimization Tool For Reciprocating Compressors Available to Purchase

Although optimization of gas pipeline systems is often performed at the level of the overall pipeline network, optimal results may not be obtained if the individual compressor stations and the units in those stations are not operating optimally or if sufficiently detailed information about compressor performance is not available. The objective of the present work is to focus on the optimization of reciprocating compressors and compressor stations in order to provide information about how to optimally operate individual units and stations to meet the requirements of the overall pipeline network optimization strategy. Optimization of a single compressor unit is addressed in the present work. It is anticipated that, in the future, the same approach can be extended to performing optimization at the station level. As a basis for this work, a compressor optimization software tool was developed that is capable of identifying operating strategies that meet given optimization goals. The optimization tool is built using a modular approach so that additional modules can be added in the future as needed to accommodate different station configurations and to meet various optimization goals. The tool currently includes modules for a reciprocating compressor and a gas engine driver. The compressor module is based on an accurate and comprehensive model of reciprocating compressor fluid dynamic and thermodynamic behavior. A comparison of results from the compressor model to experimental data shows that the model predictions of capacity and indicated horsepower are within 5% of measured data. The driver module is based on tabulated performance data that matches measured power and fuel usage data for selected engines. An initial version of the optimization tool for a single compressor unit has been developed to demonstrate the value of the results and prove the feasibility of this approach. Details of the compressor model program are presented in this paper. Example results from optimizing fuel consumption for a typical pipeline compressor with a gas engine driver at various speeds and load steps are presented. The optimization tool was used to develop performance maps showing how much fuel a driver consumes in order to meet a given capacity at various combinations of speed and clearance. In addition, the optimization tool was used to show that for the characteristics of one particular driver, fuel consumption is less if capacity is reduced by slowing the unit at a fixed clearance as opposed to increasing the clearance while running at a constant speed. It is anticipated that this type of compressor optimization software tool will be useful in analyzing installed equipment to identify inefficiencies in order to improve unit and station operations. It is intended that this optimization tool be developed further to include more complex multiple stage reciprocating compressors, centrifugal compressors, more detailed controls, and other compressor station components so that accurate compressor station optimization can be achieved. This tool is expected to be of value at the design stage when making decisions about how to select and specify equipment.