| Self-oscillation pulsed water jet(SEOPW)has many advantages over continuous jet and externally excited pulsed jet.Water jet technology has a wide range of applications in the cleaning of large equipment.According to the cleaning characteristics and requirements of large-scale storage equipment,a low-pressure self-excited pulse cavitation jet cleaning method is proposed.Consult the characteristics of jet and pulsed cavitation jets and the current research status at home and abroad,understand the research value and broad application prospects of low-pressure self-excited pulsed cavitation jets,and summarize the existing problems in the research of low-pressure self-excited pulsed cavitation jets.The relationship between the geometry of the nozzle and the pulse and cavitation effect of the water jet is still lacking.A comprehensive and accurate study of the flow field inside the nozzle is needed.In order to make better use of SEOPW technology,but also to achieve the best cleaning effect.On the basis of previous studies,the experimental research on the working state of the nozzle at different flow rates was carried out;the effect of the different chamber length of the nozzle on the pulsating pressure and the distribution of the vortex through the experiment and the half height of different chambers were also studied 1.The effect of different chamber forward tilt angles,different nozzle outlet pipe diameters,etc.on the cleaning effect.From the aspects of cavitation morphology,pressure pulse number and velocity pulsation amplitude,erosion effect and pressure distribution in the flow field.The self-excited pulse cavitation jet nozzle was numerically simulated before and after cavitation occurred to fully understand the state of cavitation and the characteristics of the flow field in the cavity.The self-excited oscillation cavitation jet experiment process was designed and the experimental device was built.Through the experimental research results,it was found that when the flow rate is the influencing factor,the effect of cavitation-free flushing in the nozzle is much lower than that when cavitation occurs in the chamber Effect;when the flow rate increases to more than 2.7 m~3/h,cavitation begins to occur in the cavity,and the location and cavitation state of cavitation bubbles are reasonably predicted;when the flow rate is Q=7.2 m~3/h,the velocity pulsation amplitude is about 17.25 m,the number of pressure pulsations generated in 1s reaches 86 times,which is the highest;in the erosion effect experiment,the flow rate has little effect on the outer diameter of the erosion circle,and the erosion rate first increases with the increase of the flow rate,at Q=7.2 m~3/h reaches the peak value,and then shows a slight downward trend;chambers of different lengths have different effects on self-excited oscillation pulses.When the chamber length=6cm,the number of peaks in 4s is 590,which is the most,and the pressure vibration amplitude is also the most At the same time,it can be clearly seen that the generation,growth,movement and collapse of small eddies raised by the shear layer are in various stages;when the length of the chamber is too long,the flow mixing is uniform enough to weaken the oscillation pulse characteristics.Apply experiments to verify the correctness of the digital model at the same time.The optimal length of the output chamber is 6cm;the optimal half-height of the optimal chamber is 50mm.At this time,the number of velocity peaks in 1s is 123,and the number of pressure pulsations is 123.,At the maximum peak number,the optimal downstream nozzle outlet diameter is preferably 16 mm,at this time the number of velocity peaks in 1s is 126,the number of pressure pulsations in 1s is 85 times,and the optimal chamber forward tilt angle is preferably selected It is 54°.At this time,the number of velocity peaks in 1s is 96,and the number of pressure pulsations is 85.Based on the above results,a reasonable and optimal parameter combination of cavitation pulse effect is obtained. |
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