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便携式烟雾机是利用脉动发动机产生的高温、高速燃气将农药雾化形成直径微小的颗粒,达到高效、环保防治林木病虫害的目的。该文建立了一套气流波动速度测试装置,利用等直径喷管中气流脉动流动特性,测定喷管不同轴向位置处的压力信号,利用同一压力信号源流过喷管不同轴向位置处,相互之间具有相关性的原理,将喷管不同位置处获得的压力信号进行相关分析。自相关分析结果表明喷管内压力信号具有典型正(余)弦信号特征,只是其中包含少许随机信号。通过互相关分析可获得喷管中两测点之间的平均压力波动速度,即气流纵波的波动速度。测试计算结果表明喷管内气流最大平均压力波动速度达5833 m/s,相当于本地音速669 m/s的8.72倍。
Portable smoke machine is the use of pulsating engine to produce high-temperature, high-speed gas atomization of pesticides to form small diameter particles, to achieve efficient and environmentally friendly forest pests and diseases purposes. In this paper, a set of airflow velocity testing device is set up to measure the pressure signal at different axial positions of nozzles by using the pulsating flow characteristics of air flow in equal diameter nozzles. By using the same pressure signal source to flow through different axial positions of nozzles, With the correlation between the principle of the nozzle at different locations to obtain the pressure signal correlation analysis. Autocorrelation analysis results show that the pressure signal inside the nozzle has typical positive (residual) chord signal characteristics, but it contains a little random signal. Through the cross-correlation analysis, the average pressure fluctuation velocity between two measuring points in the nozzle can be obtained, that is, the fluctuation velocity of the longitudinal wave of the gas flow. The test results show that the maximum average pressure fluctuation velocity of air flow in the nozzle reaches 5833 m / s, which is equivalent to 8.72 times of the local sound speed of 669 m / s.