Dynamic Performance Analysis of Submarine Screw Compressor Deballasting System

Abstract

One dimensional dynamic model for submarine low pressure screw compressor deballasting system performance analysis is developed. Cross section of outer shell of ballast tank is described as cylinder, one dimensional flow equations combined with screw compressor performance model are employed to describe compressors flow characteristic. Coupled effect between gas pressure in ballast tank and discharging performance of screw compressor is considered in the presenting model as gas leakage during compressing process is taken into account. Deballasting duration for one certain submarine model is calculated using the developed model, and the result agrees well with that obtained by using Chinese state code for submarine low pressure system design. For different cross section tank models as circular section model, parabolic section model and trapezoidal section model, dynamic performance of screw compressor deballasting system is studied using the validated model. Gas pressure in tank, dropping speed of tank water surface and draft of submarine are simulated, and the results show that little difference of deballasting duration is caused by changing tank cross section. The most stable deballasting process is achieved by using a circular section tank. Deballsting performance is also studied as tonnage of submarine and volume of ballast tank change and commonsense conclusions are obtained.