[胡东; 唐川林; 张凤华] Department of Mechanical Engineering, Hunan University of Technology, Zhuzhou 412008, China;[杨林] College of Electromechanical and Automobile Engineering, Chongqing Jiaotong University, Chongqing 400044, China
The radicals of center dot OH and center dot H are generated as cavities collapse. The hydroxyl radical, having strong oxidizing property and depending on the cavitation intensity, can react with refractory organic compound molecule. Using the choking cavitator as a cavitation generator, the influences of hydroxyl radical production on the initial concentration of methylene blue (MB), equivalent diameter of back-pressure holes and reaction time were analyzed with a visible spectrophotometer. The experimental results showed that the highest hydroxyl radical was acquired when the equivalent diameter of back-pressure holes was 5.4mm and the initial concentration of MB was 12mg/L.
Cavitation noise - Chaotic behaviour - Chaotic theory - Experimental investigations - Frequency spectra - High frequency - Lyapunov exponent - Maximum Lyapunov exponent - Noise signals - Nozzle exits - Phase space reconstruction - Standoff distance - Target position - Water jet - Water jets
The cavitation noise signals were collected separately for the cavitation nozzle and general nozzle at the target position and the nozzle exit in the condition of different standoff distance. The features of signal's frequency spectrum and power spectrum were analyzed for different nozzles. Based on chaotic theory, phase space reconstruction was processed and the maximum Lyapunov exponent was calculated separately for each cavitation signal's time series. Under the condition of this experiment, the difference between the general nozzle and cavitation nozzle was mostly marked at the target position while the standoff distance is 35 mm, which mainly displayed at the high frequency segment. The maximum Lyapunov exponent calculated appeared at standoff distance 35 mm. At the nozzle exit, the noise signal of cavitation nozzle is different from the general nozzle. The difference also displayed at the high frequency segment, and no changing with the standoff distance.