An Iterative Method to Derive the Equivalent Centrifugal Compressor Performance at Various Operating Conditions: Part II: Modeling of Gas Properties Impact

Waleed Albusaidi,Pericles Pilidis

doi:10.3390/en8088516

Abstract

This is the second part of a study conducted to model the aerothermodynamic impact of suction parameters and gas properties on a multi-stage centrifugal compressor’s performance. A new iterative method has been developed in the first part to derive the equivalent performance at various operating conditions. This approach has been validated to predict the compressor map at different suction pressures and temperatures using the design characteristics as reference values. A further case is included in this paper in order to emphasize the validity of the developed approach to obtain the performance characteristics at various gas compositions. The provided example shows that the performance parameters at different gas mixtures can be predicted to within ±1.34%. Furthermore, the conducted optimization in this paper reveals that the proposed method can be applied for the compressor design evaluation corresponding to the expected variation in suction conditions. Moreover, the examined case study demonstrates the effect of gas properties’ variation on the operating point and aerodynamic stability of the entire compression system. In order to achieve that, a simple approach has been established to assess the contribution of gas properties’ variation to the inefficient and unstable compressor performance based on the available operational data.

Highlights

The centrifugal compressor is used for wide variety of applications in oil and gas industry including gas transport, gas lift, and gas injection
This is followed by a sensitivity study in order to investigate the effect of the physical gas properties on the compressor aerothermodynamic parameters, including stage efficiency, compressor structure, and surge margin
This emphasizes the validity of the new model to derive the performance characteristics at various suction conditions and gas compositions

Summary

Introduction

The centrifugal compressor is used for wide variety of applications in oil and gas industry including gas transport, gas lift, and gas injection. Yuanyuan et al [8] improved the previous model by reducing the required measurements and by introducing a systematic approach to determine the off-design efficiency This method does not consider the effect of the thermodynamic parameters on the polytropic efficiency and density ratio. The first section tests the validity of the new approach for the performance prediction of multistage centrifugal compressors at various gas compositions This is followed by a sensitivity study in order to investigate the effect of the physical gas properties on the compressor aerothermodynamic parameters, including stage efficiency, compressor structure, and surge margin. In order to achieve that, a new approach is introduced to assess the contribution of the gas properties’ variation to compressor performance based on the available operational data

Method Validation at Various Gas Compositions

Demonstration of New Method Validation for Design Evaluation

Impact of Gas Molecular Weight

Findings

Conclusions