1、PDF外文：http:/ 9040 字 出处： Powder Technology, 2010, 200(1): 16-24 附录 Numerical study on particle removal performance of pickup head for a street vacuum sweeper Sim-Lin Lau, Michael K. Stenstrom ABSTRACT The purpose of this paper is to investigate the particle removal performance of pickup h
2、ead for a street vacuum sweeper numerically. An integrated 3D numerical model was constructed based on particle suction process in computational fluid dynamics (CFD) software. The airflow through the pickup head was treated as a continuum, while particles were modeled as dispersed phase. The Reynold
3、s stress model (RSM) and discrete particle model (DPM) were chosen in order to predict the air and particles flow accurately. The numerical simulation results show that the sweeper-traveling speed and the pressure drop across the pickup head have great effects on the particle removal performance. Th
4、e removal efficiency of particles increases with the lower sweeper-traveling speed or the higher pressure drop, and small size particles have higher grade efficiency than that of large size particles under the same operating conditions. Moreover, the removal mass flow rate of particles increas
5、es with the higher sweeper-traveling speed. Therefore, a trade-off should be considered among high removal efficiency, low energy consumption, and high removal mass flow rate. Through the numerical simulation, the effectiveness of street vacuum sweeper for removing particles from road surface
6、is evaluated, and an optimal operating condition is obtained. Besides, more information is generated to better understand the particle suction process of the pickup head. Keywords: Pickup head； Particle removal performance ；CFD ；Sweeper-traveling speed Pressure drop 1.Introduction Currently, t
7、here is a widespread concern over the pollution of particle matter. Dust and silt are the major sources of particle matter pollution, the removal of which therefore attracts considerable attention 1. Street sweeping is typically practiced to remove the accumulation of dust and silt from road surface
8、 to improve aesthetics, public healthy, and storm water quality, so it is considered as an effective pollutant control practice for many local authorities 2,3. Pickup head is the key component of street vacuum sweeper, which is designed to pick up particles efficiently from road surface and send the
9、m to dust collection hopper smoothly. The particle removal performance of the pickup head is the most important index for a street vacuum sweeper. Many researches have been performed on estimating the particle removal performance of street sweeping. For example, a study by Chang et al.
10、4 evaluated the effectiveness of street sweeping and washing for controlling ambient total suspended particles by experiments, which indicated that the street sweeping and washing process was effective at removing dust and silt from urban roads. However, some researchers such as Vaze and Chiew 5 con
11、sidered that the contribution of street sweeping to environmental quality was not very clear, and may have an adverse impact because street sweepers did not pick up smaller size particles effectively. Kang and Stenstorm 6 studied the street sweeping effectiveness as a stormwater management practice
12、by using statistical power analysis. They pointed out that the effect of street sweeping should not be underestimated because some previous researches were based on insufficient data. Therefore, new methods were needed to evaluate the street sweeping effectiveness. As the particle remov
13、al performance for street vacuum sweeper varies based on sweeping technology, operating conditions, sweeping frequency, street dirt loading and particle size distribution 7, it is necessary to develop a repeatable and reliable method to calculate the particle removal performance of pickup head for a
14、 street vacuum sweeper. In order to evaluate the particle removal performance of pickup head, engineers generally concentrate on two parameters, the sweeper-traveling speed and the pressure drop across the pickup head. Their influences on the particle removal efficiency and the particle removal mass
15、 flow rate directly relate to the performance of the street vacuum sweeper. Chen et al. 8 investigated the influence of sweeper structure and sweeper-traveling speed on the particle removal performance by experiments. They found that the wing plate of pickup head and the sweeper-traveling speed had
16、great influence on the critical pickup velocity of particles. Meanwhile, they analyzed the relationship of the particle pickup velocities and the airflow rates. With the rapid development of the computer technology, the computational fluid dynamics (CFD) has been successfully adopted to study
17、various industrial pneumatic conveying processes 9,10. Although many works have studied the particle removal performance by experiments over the past decades, few works considered the particle removal performance of pickup head using CFD. Xu et al. 11 conducted a 3D numerical simulation on the flow
18、field of pickup head and gas system for a highway mechanical sweeper. They analyzed the interaction between the pickup system and the filter system, and optimized the combined system based on numerical results. Zeng et al. 12 employed the CFD technology to simulate the flow field of pickup head. The
19、 study showed that the performance of street sweeping was improved significantly by changing the structure of pickup head, and the numerical simulation proved that the CFD was an effective tool to calculate the flow field characteristics of pickup head. However, these works did not account for the i
20、nfluence of particles on the flow field during the investigation, so the particle removal efficiency and the particle removal mass flow rate cannot be obtained. More importantly, influences of the sweeper-traveling speed and the pressure drop, which are the most important parameters, should not be n
21、eglected while modeling the performance of pickup head. Gas cyclone is the device that utilizes centrifugal force to separate particles from carrier gas, whereas pickup head for a street vacuum sweeper is the device that employs vacuum pressure to suck up particles from road surface. Therefor
22、e, the particle removal performance of pickup head will be also calculated by using the CFD approach, which has been validated by the successful investigation of the particle collection performance of gas cyclones 13,14. The aim of the present study is to investigate the particle removal perf
23、ormance of pickup head under various sweeper-traveling speeds and pressure drop using commercial CFD program Fluent 6.3. The numerical CFD model is verified by sweeping field experiments. Based on the numerical results, the balance among the particle removal efficiency, the pressure drop across the pickup head and the removal mass flow rate is considered, and an optimal operating condition is obtained. 2.Sweeping field experiments
