Design Of Pneumatic Conveying System For Sweeping Vehicle And Flow Field Simulation Of Suction Nozzle

In recent years, with rapid economic development and accelerated urbanization process, the pressure of urban sanitation increased. people are paying more attention to environment protection, and requiring more on environmental quality. At the same time, the road mileage of China has increased year by year, and the expressway mileage has risen to first in the world. Mechanized and modernized sweeping way has become the trend of road maintenance. The governments has paid more attention to the sanitation and the investment has increased. With the advantages of good cleaning effect and low cost, sweeping vehicle has become the main tool of sanitation and widely used. Therefore, the sweeping vehicle market is very broad, the technical level is also rapidly developing.In this paper, the physical properties and the flow pattern of air and dust are first studied. Air resistance, upward force, impact force and gravity act on a dust particle.The impact force is the dominant force to pick up the dust particles. Through the force analysis of the dust particles, the pick-up principle is obtained. In short, when the air velocity exceeds the pick-up velocity, the dust particles roll and collide with each other,and the impacts make the dusts picked up. Two important parameters, the pick-up velocity and the suspension velocity, are calculated, which provide the theory and data for the design, simulation and structure optimization of pneumatic conveying system.Then the design of two important parts of pneumatic conveying system are studied.Suction nozzle design should meet the industry standards. The structure and the flow field should be reasonable to get less energy loss. The most important parameter is the convergent angle which largely influent the flow velocity distribution and pressure loss.It is important for the flow field analysis and the optimization of the suction nozzle.Then the selection principle of the fan is obtained through the calculation of wind pressure and amount.There are two kinds of energy loss: local loss and frictional loss.The local loss depends on the shape change in the suction nozzle, such as convergent angle. The airflow changes sharply at the shape changes, which cause swirls. So the airflow should be as smooth as possible in order to decrease the local loss. One suction nozzle is simulated. The results show that the current design has faults in flow field distribution which will lead to low cleaning efficiency.According to the principle of reducing local loss, two unreasonable structures on suction nozzle are modified and the new models are simulated. It is proved from the results that the improved structure is more favorable to accelerate and pick up the dust particles. The energy consumption is reduced and the cleaning efficiency increased.