풍력-열 발생 유압 시스템용 가변 교축 밸브의 특성에 관한 연구

Abstract

Greenhouse farmers in need of a heating power get heat energy from electricity or oil. However, if people get heat energy from wind power which is natural energy, it is expected to be cost effective and environmentally friendly. This thesis deals with a device turning wind power into heat-energy using hydraulic pump. The device is named 'Wind Power-Heat Generation Hydraulic System'. The heat generation system consists of a wind turbine part and a heat generation part, and the heat generation part is fabricated with a hydraulic system. The hydraulic system includes a hydraulic pump, hydraulic pipeline, an orifice, a storage tank, and so on. When the wind turbine operates, pressure proportional to the turbine torque generates. Then, when the produced pressured oil flows through the orifice installed inside the pipeline, hydraulic oil is heated at the exit of the orifice. The key point in the Wind Power-Heat Generation Hydraulic System is the orifice. In case of using cylindrical orifice with a constant cross section area, pressure produced by the hydraulic pump is low when wind speed is low, while pressure produced by the hydraulic pump is excessively high when wind speed is high. The author suggests variable throttle valves which have excellent flow control characteristics under excessive pump driving torque(excessive wind speed). This study mainly consists of three parts. In chapter 2, the author describes basic operating principle of the heat generation system composed by hydraulic devices. In chapter 3, the author proposes a flow-sensitive pressure modulator as an anti-overrun device of Wind Power-Heat Generation System. The area of flow passage is controlled by the pressure difference between inlet and outlet port in the pressure modulator. When hydraulic pump overruns, the area of flow passage decreases, then it causes a rise of inlet pressure, so overrun of the hydraulic pump is avoided due to the increased driving torque of the hydraulic pump. However, when the power capacity is small(under 1kW), it is confirmed that the diameter of the spool valve of the pressure modulator is designed to be under 1mm. In chapter 4, a variable throttle valve is proposed as an anti-overrun device of Wind Power-Heat Generation System. The proposed variable throttle valve consists of a pilot valve and a main valve. Since the variable throttle valve detects flow rate through cylindrical orifice with a constant cross section area, a pilot valve and a main valve can be designed to have proper diameter. In addition, the variable throttle valve prevents a breakdown of the system by enhancing torque of pump when wind turbine overruns. The control performance of the hydraulic systems with the flow-sensitive pressure modulator and the variable throttle valve are verified through simulation using AMESim which is a general-purpose simulation program for hydraulic control systems.