Study On Throwing/Blowing Mechanism And Optimizing Parameters Of An Impeller Blower

Impeller blowers are used widely to convey materials because of their simplicity, reliability, ease of maintenance and adjustment, high capacity and low manufacturing cost. However, they also have some negative problems such as excessive power consumption, inefficiency and even clogging in the process of blowing the materials. Given the existing deficiency of the throwing/blowing theory, the throwing/blowing mechanism of an impeller blower was studied through experiments, theory analysis and computer numerical simulation, and the parameter optimization of the impeller blower was finished in this paper.(1) The 3-D air flow in an impeller blower with different parameters was simulated and analyzed using CFD (computational fluid dynamics) software FLUENT, and the basic characteristics about the air field were gained. Comparing simulation results with experimental ones showed that the mathematical model was able to accurately simulate the actual air velocities. Moreover, Study results showed that the air flow pattern would affect the blowing efficiency and power consumption, and the higher the rotational speed of the impeller was, the higher the air flow velocity at a plane of the vertical pipe was, and the farther the straw-threw distance was. Furthermore, some main geometrical parameters, such as the numbers of the paddles, the mounting angle of the paddle, the shape of housing and the arc radius of its outlet etc, were optimized.(2) The movement laws of the chopped straws along paddles have been studied by means of theory analysis, virtual prototype and high speed photograph technology. The straw-threw angle at its optimal range was from 80 degree to 130 degree, and the velocity-changing laws that the straws left the paddles were obtained. The ADAMS simulation model of the chopped straws along paddles was established by the virtual prototype technology. Meanwhile, the movement trajectory of the chopped straws was photographed. Then the regression analysis on the data was carried out to determine the value of friction coefficient, and the ADAMS model was modified based on the value of friction coefficient.(3) From high speed photograph, we found that some straws moved along a paddle till the end of paddle; others left the paddle during their movement and moved towards outlet with the help of the air flow inside the impeller, some of them collided with another paddle which took them to the outlet.(4) To reduce the power consumption and improve the throwing/blowing efficiency, the power consumption was studied by experimenting, theoretical analyzing and virtual simulating. The mathematical equations for the power consumption, efficiency and specific power consumption of the impeller blower were set up. Moreover, the geometrical and kinematic parameters of the impeller were optimized based on modified ADAMS model. As was shown from the experiment results, the modified ADMAS model and the optimization results using virtual prototype technology were reliable. The results showed that the power and specific power consumption increased by 2-3 times as the rotation speed was increased from 650 to 1050r/min of the impeller (700mm in diameter). At the same time, the specific power consumption increased by 5.5%-63.5% when the forward angle of the paddle was increased from 5°to 25°; and it increased by 3.5%-12.7% when the backward angle of the paddle was increased from 5°to 25°. When paddles were radial arrangement and rotational speed was 650 rpm the specific power consumption was minimum.The throwing/blowing efficiency range for the radial paddle was 65%~69.5% at different rotational speeds and it reached the maximum at 950 rpm.(5) To gain basic kinematic characteristics of the chopped straws inside the vertical pipe and spout, the dynamic model of chopped straws moving upward in the vertical pipe has been established, and the dynamic equations were solved with MATLAB. It provided a reference for further optimizing the geometrical parameters of the vertical pipe and spout.(6) By comparing the straws velocity and air velocity at same position, it was shown that the upward velocity was bigger than the air velocity in the process of leaving the paddles and getting into the vertical pipe, and the energy of throwing straws comes from rotating paddles; After it got into the vertical pipe, the air velocity was bigger than the straw velocity, the straws were conveyed by means of inertia and air flow, the straws were conveyed mainly by means of the paddle throwing and the air blowing.(7) The study results showed that with paddles slanted 10°backward the impeller blower increased the specific power requirement by 6.12% and the throwing distance by 16.16% respectively compared to the impeller blower with radial paddles. Therefore, when required the long distance throwing, it was suitable to select the paddles with 10°backward, if throwing distance was not required, the radial paddles should be selected in the real production.(8) The experiment equipment of an impeller-blower were developed by ourselves.