| Cleaning nozzle is the functional core of smart toilet,which plays a key role in the experience of smart toilet.As a cutting-edge product in the cleaning nozzle,the self-excited suction pulse nozzle has the advantages of no external gas source and excitation source,simple structure,easy maintenance and good cleaning effect and comfort.However,at present,the technology of self-excited suction pulse nozzle for smart toilet is limited by the technology monopoly of foreign brands,which leads to the problems of low jet pulse frequency,long cleaning distance,long cleaning time and poor cleaning comfort in similar products of domestic production enterprises.In this thesis,according to the engineering design requirements and practical application experience,the performance optimization of a self-excited suction pulse nozzle for smart toilet is studied.The main research results are as follows:1.This thesis systematically summarizes the research status of high-efficiency water jet technology and self-excited pulse water jet technology,and discusses the feasibility of applying self-excited pulse water jet technology to smart toilet.2.Based on the derived mathematical model of the occurrence mechanism of the self-excited pulse nozzle,the left and right wall inclination angle?,the lower wall inclination angle?and the inlet hole distance L_d of the mixing chamber are selected as the influence factors of performance optimization.At the same time,a comprehensive performance test platform for the self-excited pulse nozzle for smart toilet is built,and the performance of the prototype nozzle is tested.It is found that the prototype nozzle has the following problems:(1)The velocity in the mixing chamber is low.The effect of gas-liquid vortex cluster formation and gas-liquid mixing is poor.(2)The amplitude and main frequency of the jet pulse are low,and the jet performance attenuates seriously with the injection distance,up to 30%.(3)In the actual cleaning,the cleaning distance and cleaning time are too long,which is not conducive to installation and does not meet the water-saving requirements.3.Through the numerical simulation of the whole flow field of the self-excited suction pulse nozzle,the results are as follows:(1)The numerical model method of the self-excited suction pulse nozzle has high accuracy,and the average minimum error is2.2%and the maximum is 4.5%compared with the experimental value.(2)The performance of the flow field in the nozzle directly affects the jet performance.The nozzle with high velocity in the mixing chamber has a larger negative pressure area,better gas-liquid vortex mass and gas-liquid mixing,and the jet performance is better.(3)The order of the influence on the performance of the self-excited suction pulse nozzle is the left and right wall inclination angle?,the lower wall inclination angle?and the intake hole distance L_d.(4)After the jet is ejected from the exit section of the nozzle,the jet performance is obviously improved at first,and then attenuates significantly with the increase of the injection distance.4.Based on the response surface method,the coupling effect of multi-structure parameters on the performance of self-excited suction pulse nozzle is studied.The response surface regression equations between left and right wall inclination angle,lower wall inclination angle,air inlet distance and jet impact force F,jet pulse amplitude?P,jet pulse main frequency f,cleaning distance?S and cleaning rate?are established.The results show that:(1)The influence degree of single structure parameter on jet strike force and cleaning distance of nozzle is as follows:lower wall inclination>left and right wall inclination>intake hole distance.The influence degree on jet pulse amplitude,pulse frequency and cleaning rate is as follows:left and right wall inclination angle>lower wall inclination angle>intake hole distance.(2)Considering the influence of each performance of each nozzle in practical use,the optimal range of structural parameters is as follows:The inclination angle of left and right wall is[17°,21°],the inclination angle of lower wall is[11°,13°],and the distance of air inlet is[7.2mm,7.4mm].5.The self-excited suction pulse nozzle with left and right wall inclination angle of 20°,lower wall inclination angle of 12°and inlet hole distance of 7.3mm is selected as the optimized nozzle scheme,and the comprehensive performance test is carried out.The results are as follows:(1)The air intake effect,gas-liquid vortex formation and gas-liquid mixing effect of the optimized nozzle are significantly improved,and the velocity in the mixing chamber is increased by 23.1%to reach 8m/s.(2)After optimization,the jet velocity of the nozzle is increased by 10.3%to 12.87m/s,and the cleaning distance is shortened by 35.5%,which is controlled within 10cm.(3)After optimization,the impact force of the nozzle is 0.142N,which increases by 17.4%,the main frequency of the pulse is 116Hz,the pulse amplitude is increased by 38.1%,the pulse amplitude is increased by 24.4%,and the jet performance decreases by 20%with the jet distance.(4)After optimization,the cleaning time of the nozzle is reduced by20%,and the cleaning rate can reach nearly 100%within 40 seconds.The performance of the optimized nozzle is significantly better than that of the prototype nozzle and meets the needs of practical application. |
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