An Efficient Fan Drive System Based on a Novel Hydraulic Transmission

An efficient fan drive system based on a novel pressure-controlled hydraulic transmission (PCT) is studied in this paper. The new transmission uses a double-acting vane pump with a floating ring. By coupling the floating ring to an output shaft, the vane pump becomes a hydraulic transmission. The new transmission combines pumping and motoring functions in one unit, making it much simpler than a conventional hydrostatic transmission (HST). By controlling the pressure in the PCT, the output shaft torque and speed can be adjusted. In this paper, the fundamental principle of the new transmission is studied, with the focus on how the output shaft torque is influenced by the control pressure. To demonstrate its advantages, the new transmission is applied to a fan drive system, and the transmission efficiency is compared to an HST. Experimental results show that the input power of the fan drive system with the PCT is lower than that with an HST. By feeding the control flow to a hydraulic motor coupled to the output shaft of the PCT, a pressure-controlled hydromechanical transmission is constituted and the test result shows higher transmission efficiency than a PCT.