Numerical Simulation And Optimization Of Vehicle Pneumatic Conveying System

The urban air pollution is becoming more serious in China.Dust is an important factor of urban air pollution,and road cleaning is the main method to control dust on the roads.To reduce air pollution,local governments increase investment in environmental protection.The mechanized cleaning level of urban roads is gradually improved,and the demand for road sweepers is growing,which has become one of the research hotspots.The pneumatic conveying system is one of the core modules of the sweeper.The fan at the end of the pneumatic conveying system generates negative pressure,and then forms a high-speed air flow to carry road dust into the dust collection port,so as to complete the collection operation.The performance of pneumatic conveying system directly determines the cleaning rate and energy consumption of sweeper.The pneumatic conveying system of a pure electric sweeper was taken as the research object.Firstly,the flow characteristics of pneumatic conveying system were analyzed by numerical simulation method,and compared with the experimental data to verify the reliability of the numerical simulation method.Then the two-phase flow numerical simulation method was used to study the flow in the dust collection port.By analyzing the gas flow and dust movement trajectory,the characteristics of velocity and static pressure distribution in the dust collection port were clarified,and the dust escape location was determined.Then the relation between the operating parameters(flow rate and sweeping speed)and the dust cleaning rate was discussed.Based on the analysis of the flow field,an optimization scheme was proposed.Compared with the original dust collection port,the total pressure loss of the optimized dust collection port is reduced by 8.97%,and the cleaning rate is increased by 7.21%.To improve the aerodynamic performance of the centrifugal fan,which is the power component of the pneumatic conveying system,an impeller modification and multi-objective optimization scheme was proposed.Firstly,the arc blade was used to replace the original fan blade,and the parametric model of the arc blade impeller was established.Combined with the optimal Latin hypercube sampling method,Kriging model and improved NSGA-II algorithm,multi-objective optimization was carried out with the goal of maximum total pressure efficiency and total pressure.Compared with the original impeller,the total pressure efficiency and total pressure of the optimized impeller are increased by 0.72% and 3.8% respectively.At the same time,the machining difficulty of the fan blade is reduced and the machining cost is reduced.To reduce the pressure loss of pipeline in the pneumatic conveying system,based on the flow field analysis and the pipeline flow theory,an improvement scheme of the pipeline was proposed.The results show that the total pressure loss of the optimized pipeline decreases by 29.8%.Subsequently,the fan speed was adjusted to match the fan and pipeline.Under the condition that the gas flow rate of pneumatic conveying system is basically constant,the fan speed is reduced by 15%,and the power of pneumatic conveying system is reduced by 6.9 kw.