Research On Droplet Deposition And Drift Characteristics Of Manned Helicopter Aerial Spraying And Its Application

In recent years,in order to effectively reduce the damage to ecological environment caused by pesticide residues,precision agricultural aviation pesticide application technology characterized by reducing pesticide application and increasing efficiency has developed rapidly.However,the current research on droplet deposition and drift characteristics of manned helicopter(MH)aerial spraying is still weak foundation,the influence mechanism of many factors is unknown,and the practical application lacks test method guidance and technical specifications.In view of this situation,this article carried out basic research and application effect analysis of many factors that affect the drift characteristics of MH droplets through a combination of theoretical analysis,field basic tests,application tests and data processing.The main research results are as follows:(1)In the research of the reduction mechanism of aviation application,the complexity of aircraft fuselage and rotor motion and the effects of strong turbulence on the droplets deposition and drift characteristics were discussed.It revealed the effects of flight status,droplet size,dosage form,different collision speeds and angles,and the shape of the leaves on the deposition and wetting of the medicinal solution on the leaves.The movement of the pesticide droplets onto the target plant leaves and related factors affecting spray quality had been theoretically recognized.(2)In the study of the droplet deposition and drift regular of helicopter aerial spraying,the spray tests of the AS350B3e helicopter with the AG-NAV Guía system were conducted with different operating parameters and methods.The droplet deposition and drift regular and the effects of adjuvant were studied.The results showed that when the helicopter was operated at a height of 5 m and a velocity range of 70 to 120 km/h,the effective deposit swath width increased slowly and then decreased sharply with the increase of flight velocity.It was also found that droplets with droplet size smaller than 200μm were more likely to drift,which accounted for more than 70%of the total number of droplets in the drift area.In order to ensure the best spraying effect,the aviation nozzle should be selected reasonably,and aviation adjuvant should also be appropriately used.At the same time,a buffer zone(safe area)of at least 50 m should be reserved during operation to avoid the hazards of droplet drift.The results of this study also lay the foundation for the subsequent research on the atomization characteristics of aviation nozzles and their practical applications.(3)In the study of atomization characteristics of aerial nozzles under wind tunnel medium and low airflow velocity condition of MH,the LICHENG series and the CP series flat-fan nozzles commonly used in domestic MH were studied.The atomization characteristics of each type of nozzle under medium and low airflow velocity conditions of0 to 27.8 m/s were evaluated in turn.Furthermore,the field verification test was performed for the spray characteristics of CP series nozzles.For LICHENG series nozzles,the droplet sizes of the five types of 11012,11003,11004,11006,and 11010 nozzles showed similar increase trends with the increase of airflow velocity.The reason for this phenomenon was not only related to the atomization characteristics of the flat-fan nozzles,but also to the limitations exist in wind tunnel droplet size testing by using laser diffraction device.In addition,the change of spray pressure would directly affect the quality of spray.However,as the airflow velocity increased,the significance of spray pressure on the spraying effect of these nozzles was gradually weakened.The research results of LICHENG series nozzles revealed the atomization characteristics of the flat-fan nozzles and provided a reference for the subsequent CP series nozzle tests.For CP series nozzles,The wear caused by the long-time use of the nozzle would affect the spraying performance,which made the measurement deviation of droplet size value large.The droplet size values measured by the three types of CP nozzles(CP02,CP03 and CP04)showed an increasing trend with the airflow velocity increased.The field test proved the main distribution range of each type nozzle droplet size,which was consistent with the results of the wind tunnel test,but the droplet size value measured in the field test were significantly higher.(4)In the application research of aerial spraying of MH on citrus,the Bell206L4helicopter was used as the platform for spraying,and the research on the spray droplet deposition of mountain citrus orchard sprayed by helicopter using two different aerial spraying methods was carried out.For helicopter hovering aerial spraying operations,when the spray per unit area was set to 15 L/ha,the helicopter flight height was 10 m from the tree top and the flight velocity was 120 km/h,the CP04 aerial nozzle was recommended to be equipped.Under the above operating conditions,the average droplet deposition amount of the whole mountain was0.896μL/cm~2,and the uniformity of droplet distribution was 60.82%.For the citrus trees at each sampling point,the droplet deposition volume decreased from the upper layer to the lower layer of the fruit tree.For helicopter reciprocating aviation pesticide application,the CP04 aerial nozzle was selected for the helicopter,and the spray volume of 15 L/ha per unit area and flight velocity of 120 km/h were set.The deposition amount of droplets in different sampling areas of the mountain showed a trend of the top of the mountain was the largest,the bottom of the mountain was next and the central of the mountain was the smallest.In order to ensure effective application,It was recommended that helicopters operated at a flight altitude of less than 10 m.In addition,it was also found that different tree-shaped citrus trees had some differences in droplet deposition.(5)In the application research of aerial spraying of MH on pine forestry,the distribution pattern of droplet deposition of Bell206L4 helicopter for aerial spraying of Pinus koraiensis in Changbai Mountain and Pinus massoniana in Lushan Mountain were studied.The control effect of Korean pine cone pest insects and Monochamus alternatus hope after application was also investigated.CP03 aerial nozzle had good and stable atomization performance,which was suitable for the aviation spraying control of Korean pine cone pests in Changbai Mountain.The mean deposition volume and deposition density of most Korean pine were in the range of0.065～0.073μL/cm~2and 9.6～11.6/cm~2,respectively.The amount of droplets deposited in the middle of the Korean pine canopy was significantly higher than that of the other layers,indicating that the droplet retention ability of the middle canopy of Pinus koraiensis was stronger.The study also found that there were some differences in the control effects of the two different pesticides,but the different pesticides had no significant effect on the aerial spray deposition effect.For the control of Monochamus alternatus hope in Lushan,when the MH was set a spray volume per of 15 L/ha unit area and flight height of 10～15m from the top of the tree,it was recommended that the helicopter be equipped with CP04aerial nozzle.At this time,the droplet deposition effect was the best.The study also found that the overall size of the droplets showed a trend of the middle of the canopy was smallest,the position of the trunk was next and the upper of the canopy was largest.In terms of control effect,it was finally measured that the correction control rate of Monochamus alternatus hope in Lushan region was in the range of 59.24%～95.74%,and the growth trend of Monochamus alternatus hope emergence was restrained to a certain extent.