Basic Research On Integrated Hydraulic Propulsion Ship

A new ship propulsion method, Integrated Hydraulic Propulsion (IHP), is proposed to improve the traditional ship propulsion system and then promote the modern ship development. In this method, the output power of several (two and more) main engines is transformed to fluid power by the means of hydraulic pumps to drive propellers (hydraulic motors), steering engines, side thrusters, and etc. Meanwhile, auxiliary engines are replaced by electric generators that are driven by main engines.Based on the IHP specified, an IHP propulsion system is designed. Working condition matching characteristic (WMC) principle of the system is studied through their WMC curves. An IHP ship control strategy, CVCC, is put forward based on the principle. The engines on IHP ship can always work well under designed working condition with CVCC.An efficiency model is developed to analyze the efficiency of the IHP hydraulic transmission system, using which effects of system pressure, oil temperature, pipe diameter, and leakage coefficient on transmission efficiency (TE) are studied. Results show that the TE can reach 0.85 and the system pressure, oil temperature, pipe diameter, and leakage coefficient influence the TE significantly. On one hand, the TE can be larger as the pipe diameter increases, if the leakage coefficient is constant. The TE of max (TEM) moves from high temperature and high pressure area to low temperature and high pressure area and then to low temperature and low pressure area finally. On the other hand, the TE can be lower as the leakage coefficient decreases. The TEM moves from low temperature and high pressure area to low temperature and low pressure area. Although the TE of the IHP system is lower than the Direct Propulsion (DP) system, the total efficiency of the IHP system is still higher than the DP system if the IHP ship works under certain off-design working conditions. The economical efficiency of the IHP ship can be apparently improved by decreasing the weight and volume of the propulsion system and in the way auxiliary engines are replaced by electric generators that are driven by main engines. Furthermore, in order to promote the TE of hydraulic system, Thermo energy recovery method and apparatus is developed to recover the thermo energy produced in working process instead of to dissipate it through a cooler and etc.Moreover, based on the WMC principle, the CVCC control strategy, and the TE analysis of the IHP system, an IHP model experimental rig and an IHP dynamic mathematic model (DMM) are developed. The DMM is then validated by the experimental rig. Accordingly, simulation comparison between the IHP system and the DP system is implemented using the DMM. Results show that the maneuverability and WMC characteristic of the IHP ship is evidently better than the DP ship, and the CVCC is effective for the IHP ship. In the mean time, the response characteristic of the IHP system is analyzed to demonstrate the significant influences of oil temperature, carrying capacity and seawater density to the IHP ship characteristic and slight influences of the oil modulus.In conclusion, the IHP ship is of better maneuverability, better working condition matching characteristic, more working patterns, better safe reliability, and larger power to weight ratio, which can protect the propulsion system against overloading easily and also recover the energy generated in ship baking process etc. So, the IHP system is one of the best propulsion systems particularly for some large ships, engineering ships and special ships.