Numerical Investigations And Fuzzy Grey Relational Analysis Of Nozzle-entrainment-particle Flow In Sweeping And Suction Vehicle

With the development of the city, a large amount of dust particles were generated on the city roads. The traditional manual cleaning is not only low inefficient, but also the health of the cleaning workers are seriously threatened by the dust particles. In order to solve this problem, the sweeping and suction vehicle is a good choice for high efficiency and low cost. As the pneumatic conveying system is the core and complex part of a sweeping and suction vehicle, whether it can effectively work and the dust collection efficiency will directly affect the working performance of the sweeping and suction vehicle. This paper is supported by State Key Laboratory of Construction Machinery under the research grant of SKLCM2014-8 and the Key Subject of Hunan Province under the research grant of 2015KFJJ003. The method of computational fluid dynamics is employed to investigate the multiphase flow mechanism of gas-entrainment-particle bed in the sweeping and suction vehicle under negative suction pressure, providing great reference value for the optimization design of pneumatic conveying system in the sweeping and suction vehicle under negative pressure suction. The main work is as follows:(1) For dry sweeping and suction vehicle, the model of nozzle was built and investigated. The flow field distribution of nozzle, trajectory of dust particles and its residence time was obtained. Then, the model was optimized and compared. Results showed that the residence time of dust particles in the original nozzle went to 5.09 s, while the residence time of dust particles in the improved nozzle arrived at 6.23 s. This is mainly due to the added clapboard at the right and lower part of the nozzle.(2) The method of Orthogonal Experimental Design was employed to investigate the effects of three representative factors(ambient temperature, particle diameter and suction pressure) on the pressure field, the flow field, the Reynolds number field, the residence time of dust particles and the maximum velocity of flow field. Results indicated that the larger diameter of dust particles was favor for the deposition of dust particles. However, if the diameter of dust particles exceeded the diameter range of picking up dust particles, the working performance of sweeping and suction vehicle was lowered. Besides, if the negative suction pressure was too large, the diameter range of picking up dust particles was expanded, but the residence time of dust particles was reduced, the working performance of sweeping and suction vehicle was also lowered. In addition, it was found that the negative suction pressure was positively related with the maximum velocity of flow field. The largest the negative suction pressure, the highest the maximum velocity of flow field, the largest the diameter of picking up dust particles.(3) The fuzzy membership cosine value and Euclidean distance formula was applied to establish a fuzzy gray relational analysis model. The impact of ambient temperature, dust particle diameter and negative suction pressure on the residence time of dust particles and the maximum velocity of the flow field was analyzed. Results showed that the dust particle diameter owned the largest impact on the residence time of dust particles, followed by the negative suction pressure, while the ambient temperature had the lowest impact. It was also found that the ambient temperature had the largest impact on the maximum velocity of the flow field, followed by the dust particle diameter, while the negative suction pressure had the lowest impact.