Suppressing water hammer of ship steering systems with hydraulic accumulator

This article is a contribution to the design of the hydraulic steering system with an accumulator of different parameters on suppressing water hammer. The accurate model taking account of the characteristics of the entrance of the hydraulic accumulator, which have great influence on the frequency characteristics of the accumulator is developed. In addition, this article proposes a more comprehensive distributed parameter model of the hydraulic steering system with an accumulator installed before the proportional directional valve, which takes into account both the relief valve and the pipeline between the hydraulic accumulator and the proportional directional valve. The dynamic characteristics of the hydraulic steering system were analyzed both in the frequency and time domain. The numerical simulation of water hammer which used a holistic unsteady-friction model has been performed by the method of characteristics and finite difference method with spatial interpolation using Fortran language. The law that the natural frequency of the accumulator which is equal or approximate to the frequency of water hammer in pipeline has good effect on suppressing water hammer is validated by analytical and numerical simulations as well as experimental results, for the design of the nominal volume and charged pressure of the hydraulic accumulator in the hydraulic steering system.