Effective experiment of elevated wind machine for frost protection with long blade in large apple orchards

Abstract: In recent years, the crops have severely suffered from frost damage with the deterioration of the global climate. Conventional methods of frost protection, such as smoking, covering, and irrigation may be effective in many cases, but they are time-consuming, and some methods even easily caused environmental contamination. So study of scientific and high-effective artificial frost prevention equipment has become very necessary and an urgent need. Most wind machines for frost protection are still in the pilot stage at home and abroad, and their height and blade length, etc, are not for taller plants, such as apple trees，peach trees, and cherry trees. The Gansu meteorology department, using the principle of disturbing the air of mechanical power, invented the first domestic elevated wind machine for frost protection with a long blade, which proved the feasibility of frost protection by air in disturbing surface layer. The machine construction has the main components as follows: blade，pipe tower，fan base，underground base，engine and ladder. In order to study the effect of frost prevention and the extent of protection for an elevated wind machine, the instrumentation layout was as follows: at a distance of 53 m from the wind machine, installing a 10 m gradient observation tower of temperature within protected areas, and at a distance of 190 m from the wind machine, also installing a 10 m gradient observation tower of temperature outside protected areas as the effect of frost prevention control. Two gradient tower of temperature at 1.0, 2.0, 3.0, 4.0, 5.0, 8.0 and 10 m from the ground installed a temperature sensor respectively, which observed vertical temperature distribution; also at 2 m from the ground install a humidity sensor observed relative humidity. A projector to the ground of the wind wheel rotation axis of the wind machine for the center line, arranged the horizontal distribution of an observation point at intervals of 10 m, a total of 10 observation points, and each observation point 1, 2 and 3 m from the ground were erecting a portable anemometer for wind observation. In this paper, based on the contrast test observation data of the processes of a strong decrease in temperature from October 19 to 21,2013, the frost protection effect of the first self-designed domestic elevated wind machine for frost protection with a long blade was evaluated. The main analysis results were as follows: 1) Under the temperature inversion condition, the upper and lower air disturbance caused by one elevated wind machine with a 6m diameter blade of 12 kW power and 8.5 m in height made the temperature inversion disappear and the temperature within 1-3 m greatly increased. Relative humidity decreased rapidly, effectively preventing the generation of frost in the protected area. 2) The disturbances-affected area of strong wind was about 20 m, and wind speeds at 3, 2 and 1m from the ground were 4.0, 2.1 and 1.6 m/s respectively. The effective protection range of one wind machine was 20 m to 100 m, within level range of 20-100 m, wind speed changes of 1-3 m showed a reduced trend with fluctuations. The effective protection area of one wind machine was 1.73-3.07 hm2. The result of the research provides a reference for scientific and high-effective artificial frost prevention and promotion of an elevated wind machine for frost protection with a long blade use.