Energy-saving technology for water hydraulic motor system (first report: Simulation result)

Recently, the application of water hydraulics has received considerable attention because of its inherent merits such as environmental friendliness, hygiene, washability, high safety against fire hazard, lower running cost, and availability of tap water. However, water hydraulic systems have lower energy efficiencies than oil hydraulic systems, and this prevents its wider application. The water hydraulic variable displacement pump is yet to be made available in the market as it requires advanced technology and high manufacturing cost. Currently, water hydraulic servo/proportional valve systems or independent metering systems incorporating fixed displacement pumps lose large amounts of energy because of surplus pressure and flow rate. This study is aimed at designing a novel water hydraulic transmission technique to improve the efficiency of motor systems. The proposed system uses two two-way, two-position flow control valves for controlling the pressure at the input port of the hydraulic motor by releasing small amounts of surplus flow rate to a reservoir through these valves. The surplus pressure in such systems can be minimized and made equal to the hose pressure drop. The simulation results showed that the proposed transmission system can improve the energy efficiency of the independent metering system and conventional system to approximately twice and thrice the current value, respectively. In this study, the energy losses in the three systems were also analyzed in detail.