Study on Dust Turbulence-Chemical Agglomeration for Electrostatic Precipitation Technology

Due to the turbulent mixing between agglomeration agent and dust, the number of collisions per unit time between particles and droplets increases with the particle size in the process of chemical agglomeration, and the agglomeration efficiency increases accordingly. Turbulent agglomeration can promote the agglomeration effect of subsequent chemical agglomeration by strengthening the collision between particles and agglomerant droplets. The author used chemical agglomeration and turbulent mixing to cooperate in order to improve the efficiency of dust removal. Turbulent mixing can promote chemical agglomeration from agglomeration effect and dust removal efficiency, which can greatly improve electric dust removal technologyTurbulent mixing is the most intense at the inlet box position, and the agglomeration effect is the best. Turbulent mixing synergistic effect has an effect on dust removal efficiency. Compared with the three curves, it can be seen that the dust removal efficiency increases rapidly with the increase of agglomeration concentration, the curve trend changes obviously. The dust removal efficiency can reach 98.36 % and it is the highest in the middle section when the wind speed is greater than 11.2m/s. Through the experiment, the turbulent mixing and chemical coagulation method has a good application prospect in the electrostatic precipitators.

Inlet Box Structure Optimization of a Large Axial-Flow Fan Using Response Surface Methodology

Large axial-flow fans are widely used in many fields. The inlet box is an integral part of large axial-flow fans, and a well-designed inlet box could effectively improve fan efficiency. However, the inlet box structure is complicated, and the existing inlet box design method severely depends on the design experience. In this study, we propose a structure optimization design system based on a surrogate model technique for researching the critical structure parameters of the inlet box and accomplishing aerodynamic performance optimization. As for this expensive optimization problem, the design system contains twice optimization procedures by using the Response Surface Methodology (RSM) with the orthogonal design method. The optimization object is an existing large axial-flow fan. The optimization objective is the total pressure efficiency of the fan, and the total pressure rise is the restriction condition. We generate eighteen different inlet boxes connect with the same impeller and outlet pipe by the orthogonal design method and calculated fan aerodynamic performance by CFX software. After the first optimization, we find the key structural parameters by the sensitivity analysis and the reselect variables total of 25 cases are adopted in a further RSM optimal process. The ultimate surrogate model estimates the fan with the optimal inlet box has a better aerodynamic characteristic and a 6.7% total pressure efficiency rise. Finally, we compare the aerodynamic characteristics of the ultimate design fan and the initial fan by CFD simulation. The numerical results show that: the total pressure efficiency is 6.5% higher than that of the initial impeller, and the pressure rise is 3% higher than that of the initial impeller. The result demonstrates that some most critical parameters of the inlet box structure decide the aerodynamic performance, and the inlet box optimization effectively increases the fan efficiency in the meanwhile.

The Effects of Inlet Box Aerodynamics on the Mechanical Performance of a Variable Pitch in Motion Fan

This paper describes research involving an in-service failure of a “variable pitch in motion” fan’s blade bearing. Variable pitch in motion fans rotate at a constant speed, with the changing blade angle varying the load. A pitch-change mechanism facilitates the change in blade angle. A blade bearing supports each blade enabling it to rotate. The author observed that as the fan aerodynamic stage loading progressively increased, so did the rate of blade-bearing wear. The reported research addressed two separate, but linked, needs. First, the ongoing need to increase fan pressure development capability required an increase in fan loading. This increase was within the context of an erosive operating regime which systematically reduced fan pressure development capability. The second need was to identify the root cause of blade-bearing failures. The author addressed the linked needs using a computational analysis, improving the rotor inflow aerodynamic characteristics through an analysis of the inlet box and design of inlet guide vanes to control flow nonuniformities at the fan inlet. The results of the improvement facilitated both an increase in fan-pressure-developing capability and identification of the root cause of the blade-bearing failures.

Fan Casing Noise Radiation

This paper presents a method for assessing the extent of casing noise radiation of a centrifugal fan relative to the aeroacoustic sources associated with the inlet box of the fan. Central to the method is a boundary element program which is used to compute the acoustic pressures on the surfaces of the fan casing in terms of its surface vibration which in this case was measured experimentally. Data from an earlier experiment was used as the starting point for this study. Available data included sound pressure measurements near and away from the inlet box of the fan and vibration measurements over the casing of the fan. Noise from the outlet duct of the fan was purposely highly attenuated. Computations of sound pressure, intensity, and power indicated that, at the blade passing frequency (300 Hz), the aerodynamic sources generated near the entrance plane of the inlet box of the fan dominate the noise spectrum in the field. On the other hand, at the first subharmonic frequency of the blade tone (150 Hz), the sound power generated from the inlet box and fan casing are within 3 dB of each other. Thus, for effective noise control at this frequency, it would be necessary to include both noise sources in the overall treatment.