The influence of efficiency of the cooling system on the thermodynamic parameters and performance of a two - stage VC 20.96 reciprocating compressor designed to serve as a marine engine starter

Mateusz Grzelczak

doi:10.2478/pomr-2013-0037

Abstract

ABSTRACT The paper presents results of the research related to the analysis of the thermodynamic and flow processes occurring in a prototype VC 20.96 two-stage liquid-cooled reciprocating compressor. The compressor has been developed and manufactured by H. Cegielski Poznan metal works in collaboration with the Poznan University of Technology. The research related to the VC compressor was realized within the KBN 3127/C.T07-6/2002 project titled “Development of design of type-series of reciprocating compressors and their implementation in production”. The basic task of the project was to develop two type-series of liquid- and air- cooled reciprocating compressors of the V- and W- arrangement, designed to serve as marine engine starters. The result of the design work was the manufacturing of two compressors: the VC 20.96 liquid-cooled compressor and the WP 18.80 air-cooled one. The main aim of the research described in this paper was to evaluate the efficiency of the cooling system which uses inter-coolers integrated with the compressing stages and the cooperation of the compressing stages in terms of pressure ratio distribution. Owing to the cooling method, the applied design assumptions enabled to develop a compact compressor fulfilling the assumed operating parameters.

Highlights

The requirements set for the compressing machines installed in marine engine rooms force the designers to develop simple and reliable design solutions with particular focus on their limited size
The obtained indicator diagrams enabled to verify the efficiency of the cooling of the cylinder walls, based on the determined polytropic exponents of the compression process
The first stage phase of the research consisted in the measurement of the stationary parameters such as temperatures, pressures, volumetric flow rate of air and coolant in the characteristic control cross-sections of the reciprocating compressor

Summary

INTRODUCTION

The requirements set for the compressing machines installed in marine engine rooms force the designers to develop simple and reliable design solutions with particular focus on their limited size. In light of the above given conditions the engineers aimed at ensuring the assumed parameters such as pressure increments and volumetric flow rates of the compressed gas, guaranteeing high efficiency of the process through the improvement of the cooling. In the VC compressor has been implemented a solution that consists in integrating the inter-cooler and the after-cooler with the compressing stages This required developing complex casts of the cylinder heads and coolers. The applied uneven distribution of pressure ratio between the first and the second stage contributed to the development of excessively high temperatures in the second stage compression chamber. Another problem yet occurred - the air in the second stage suction chamber heated up.

Design parameters:

EXPERIMENTAL RESULTS

SUMMARY AND CONCLUSIONS