Analysis of Pressure Pulsation Influence on Compressed Natural Gas (CNG) Compressor Performance for Ideal and Real Gas Models

Zhan Liu,Longhui Liang,Zhenya Duan,Wenguang Jia

doi:10.3390/app9050946

Zhan Liu, Longhui Liang + Show 2 more

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https://doi.org/10.3390/app9050946

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Abstract

This work investigates the effects of pressure pulsations on reciprocating natural gas compressor performance thermodynamically. A nonlinear hybrid numerical model is thus developed to consider the interaction between the compressor and the pipeline system. The suction chamber, compressor cylinder and discharge chamber are modelled integrally based on the first law of thermodynamics and mass balance, and the pipeline flow is described by using the gas dynamic model. Methane is considered as the working fluid and its properties are computed based on ideal and real gas assumptions. For the real gas model, the methane properties are obtained by means of calling the NIST REFPROP database. The validity of numerical results is confirmed by previous experimental values. Results from the examinations of pressure pulsation influence demonstrate that discharge resonance requires more specific work than suction resonance in the same harmonic; in the suction system, the first harmonic response reduces the mass flow rate but significantly increases specific work, and the second harmonic response has a strong supercharging effect but the specific work is increased slightly; in the discharge system, the mass flow rate is changed little by pressure pulsations, but the indicated power and specific work are increased significantly; for the real gas model, the in-cylinder temperature during the compression and discharge phases, mass flow rate and indicated power are higher than those for the ideal gas model, whereas the specific work is less for the real gas model than for the ideal gas model.

Highlights

A reciprocating compressor is the core component dominating the refueling process in a compressed natural gas (CNG) refueling station
The experimental thermodynamic cycles of reciprocating compressors, and the experimental results have been widely measurements performed by reference [38] were typical and valuable for testing the thermodynamic cited by many researchers for comparing their numerical results
Based of thedeveloped pressure pulsation for ideal and real gas models,and some conclusions are on the examinations summarized below: of the pressure pulsation influence for ideal and real gas models, some main conclusions are summarized below: (1) Pressure pulsations in the pipeline system can lead to clear oscillations of the in-cylinder pressure

Summary

Introduction

A reciprocating compressor is the core component dominating the refueling process in a compressed natural gas (CNG) refueling station. Natural gas with a low pressure about 0.5 MPa from the distribution pipeline must be compressed to a much higher value (20 MP–25 MPa) in a CNG station [2]. The high pressure ratio achievement is realized though using a large multi-stage reciprocating compressor (three or four stages). This equipment plays a key role in both initial and operating costs at any CNG filling station due to its a huge amount of input energy. While designing CNG compressors, particular attention is paid to the enhancement of efficiency and reliability through more detailed and accurate design processes

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