| As a kind of agrometeorological disaster,heat damage to horticultural lawn is very harmful.Long-term heat stress in summer will cause excessive water loss and metabolic disorder of turfgrass,resulting in slow growth,withered leaf tips,and even wilting death.The current lawn fan equipment in China has a single mode of action,high power consumption and limited air supply distance.The traditional shading and irrigation measures not only have poor cooling effect,but also take time and effort.Therefore,in order to develop a low-power,long-distance and better cooling effect of the horticultural plant cooling fan equipment,the overall design and key components of the horticultural plant cooling fan system are firstly carried out;then,through orthogonal test and CFD simulation,the structure parameters and cooling effect of the air duct are optimized and simulated respectively;finally,the horticultural plant cooling fan system developed is tested.The spray performance and cooling effect were studied.The main research contents and results are as follows:(1)The overall design and key components of the cooling fan systemAccording to the existing arc-arc blade blades and the cooling requirements of the lawn in high temperature environment in summer,the overall and key components of the horticultural plant cooling fan system are designed,including the design and selection of key components such as swing head mechanism,wind drum structure,motor,water pump,nozzle and fog ring.The overall layout of the whole system structure is arranged,and swing head mechanism,air duct structure and spray system are designed.A prototype of horticultural plant cooling fan is developed.(2)Structural optimization of air duct and numerical simulation of cooling effectOn the basis of establishing the mechanics model of the air duct,three factors,namely the diameter of the air outlet,the length of the air inlet and the length of the air outlet,are selected to carry out the orthogonal experimental design,taking the total pressure at the inlet,the total pressure at the outlet and the wind speed at the outlet of the fan as the evaluation indexes.The CFD simulation results show that the diameter of the outlet is a very significant parameter affecting each index,the length of the outlet section takes the second place,and the length of the inlet section has less effect.If the total outlet pressure and the outlet wind speed are to be increased,the outlet diameter and the length of the outlet section can be appropriately reduced,and the length of the inlet section can be appropriately increased.The optimal structural parameters of the air duct are calculated:the diameter of the air duct outlet is 1070 mm and the total length of the air duct is 840mm.Based on the optimized duct structure,the temperature and humidity fields of the spray two-phase flow field were numerically simulated,and the effects of different spray flow rates on temperature and humidity field were studied.The results show that the spray flow rate increases,the cooling range increases,and the relative humidity increases.At the same time,the layout of 15 nozzles on the fog ring is determined.(3)Spray performance test and cooling effect experimentThe flow characteristics test,ventilation performance test and spray cooling effect test of the optimized horticultural plant cooling fan are carried out.The experimental results of nozzle flow characteristics show that the flow rate of the same type of nozzle increases with the increase of pressure.Under the same pressure condition,the flow rate of the nozzle increases with the increase of aperture.The experimental results of fan ventilation performance show that the air volume of fan outlet is 701.30 m~3/min,and the maximum air speed of fan outlet reaches 16.00 m/s.With the increase of distance,the wind speed gradually decreases and tends to be stable at 50 m.The results of the spray cooling test showed that the temperature would reach equilibrium after spraying for a period of time.The optimum spray time determined under the experimental conditions was 300 s.According to different nozzle combinations and fan action modes,different test treatments are set up and compared.4 test treatments were set up:15 WJ-7010 nozzles(A1),15 WJ-8010 nozzles(A2),5 WJ-7010 nozzles and 10 WJ-8010 nozzles(A3),5WJ-7010 nozzles and 10 WJ-8010 nozzles,and fan elevation angles(A4).Each test was carried out in three stages:blow dryer(T1),blow dryer and Spray(T2),and blow dryer(T3).The results of spray cooling test show that each treatment has a good cooling effect.At the height of 1.5 m,the cooling range of each treatment is A1>A3>A2>A4,and the average temperature can be lowered by 1.15°C~10.66°C;at 0.75 m height.At the same time,the cooling range of each treatment is A2>A1>A3>A4,and the average temperature can be reduced by 1.98°C~10.61°C.On the lawn surface(near-surface),the cooling range of each treatment is A2>A1>A3>A4,average The temperature can be reduced by up to 0.68°C~11.11°C.In addition,the horticultural plant cooling fan also has the function of ventilation and dehumidification,and the average relative humidity during ventilation can be reduced by 14.59%~24.02%. |
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