## 1 Introduction  
Most wind turbines are set up in coastal islands, grassland pastoral areas, deserts, plateaus and other areas with open terrain and abundant wind energy resources. In the case of resource shortage and inconvenient transportation in remote areas, wind power can be used according to local conditions to provide the local area with continuous electricity and stabilize social and economic development [1, 2]. With the rapid development of the wind power generation industry, the scale of operation of units continues to expand, resulting in normalization of equipment mechanical failures. Failure of fan bearings and gearboxes caused by poor lubrication accounts for about 30% [3, 4, 5]. Therefore, it is imperative to maintain good lubrication of equipment during normal operation. In order to ensure effective lubrication performance of wind turbines, researchers have optimized the equipment for problems such as blockage of the lubrication system, blockage of bearing cavity and leakage of bearing seals [6, 7]. [PERSON] [8] designed a new lubrication pump for wind power generation equipment. The lubrication pump was hydraulically driven, easy to control, high-precision, smooth-work and low-impact, and the hydraulic system improved the outlet pressure, pumping performance and reliability of the lubrication pump. The new lubrication pump effectively solved the problem of grease blockage caused by the machining accuracy of the current fan lubrication pump. [PERSON] [9] optimized the automatic retienible system, distributor oil outlet and automatic refueling interval. This optimized design addressed the difficulty of pumping grease at low temperatures and aggregation of grease in the bearing cavity, avoiding the problem of bearing over-temperature damage caused by poor oil drainage in the bearing cavity. In order to avoid grease leakage caused by a bearing oil seal bursting [10, 11, 12], researchersfocused on improving bearing oil seal sealing performance. [PERSON] et al. [13] adopted a radial sealing lip to ensure sealing of the sealing ring of the time-varying pitch bearing with radial offset in the inner and outer rings. Based on not changing the metal structure of the main shaft, [PERSON] et al. [14] adopted a new structural design of supporting ring and sealing ring to provide a better bearing grease sealing effect. The above studies effectively addressed the problem of lubrication of wind turbines in practice by optimizing the device but did not improve the lubrication performance of the overall lubrication system. Based on this problem, this study performs an overall optimization of the centralized lubrication system design for wind turbines. The fan bearing adopts an oil seal to ensure excellent lubrication of the bearing. In order to solve the problem of grease leakage in pitch bearings, the main way to recover waste grease of the existing fan bearing is to continuously add new grease to the bearing through an automatic refueling machine. The new grease will continuously squeeze the old grease in the bearing cavity and squeeze the waste grease into the oil collecting bottle installed on the bearing seat to complete the process of waste oil recycling [15]. The extrusion method is convenient and low-cost, but the recovery power is insufficient and the waste grease cannot be discharged in time, which will cause saponification, deterioration and hardening of the grease, hinder injection of new grease and eventually lead to bearing damage and generator shutdown [16; 17]. At the same time, because fan bearings are oil-sealed to ensure good bearing lubrication, long-term use of this method will cause grease seal leakage. When the bearing oil seal is unable to withstand excessive seal pressure as the grease is continually filled, the oil seal expands at the filling port, where all the new grease then overflows. Grease spilling from the cracked oil seal increases operating costs and causes environmental pollution [18].