Power consumption and parameter optimizationof stalk impeller blowers

Abstract: The impeller blower is widely used in various forage harvesters, such as crop straw choppers, rubbing, and breaking machines, to convey materials because of its simplicity, reliability, easy maintenance and adjustment, high capacity and low manufacturing cost. However, some undesired problems such as high power consumption, low throwing/blowing efficiency and high clogging probability also exist in the process of throwing/blowing the materials.In order to reduce the power consumption of the impeller blower and increase its blowing efficiency, the theoretical analyzing method was used to establish the mathematical models of the power consumption, firstly based on considering the airflow, which is suitable for forward-slant, backward-slant and radial paddle. The power consumption includes two parts. One part is the energy required to accelerate the materials that will obtain kinetic energy by means of the mechanical centrifugal force when the paddle rotates at high speed. The other part is the energy that accelerates the airflow in the impeller blower and helps the materials conveying under the condition of high rotating speed of the paddle. The first power consumption is related to the material-threw angle, namely, the rotation angle of the paddle in the course of hitting, carrying and throwing out of the material. When the material-threw angle is in the range from approximately 60°to 130°, all materials are thrown out of the housing under the condition of low energy consumption, high throwing/blowing efficiency and low clogging probability. However, when the material-threw angle is less than 60° or more than 130°, few materials are thrown out of the housing directly. Most of the materials will hit the housing, which causes most of the energy lost under the hitting energy E4c and a frictional energy E4f. Through validation by using the test data of the corn stalk, it shows that the computing power consumption by using this mathematical model of the power consumption agrees well with the measured data by multiplying the E4c and E4f with a correction factor of k=0.35 respectively.Moreover, the optimum design was conducted to the structural and kinematic parameters of the impeller blower by treating the minimum specific power consumption (energy consumption of unit throughput) as the target function by using a Virtual Prototype Technology based on a modified ADAMS model of materials motion along the paddles in reference paper. The results show that when the impeller's external diameter is 700mm, its width is 160mm, its rotational speed is in the range of 650-2000r/min, the forward slant angle changes from -25° to 0 (radial paddle) and the backward slant angle changes from 5° to 25° with an increasing step of 5°, the radial paddle with a rotational speed of 650r/min consumes the minimum specific power. As is shown from the comparative analysis of the real specific power consumption and the optimized results, the optimum results are reliable.Furthermore, the optimum parameter setup for the impeller blower is gained at different operating conditions by using a parametric analysis of a Virtual Prototype Technology. For example, when the impeller blower works with the rubbing and breaking machine and throws/blows the rubbed and broken materials, and the impeller's external diameter is 700mm, its width is 160mm, its rotational speed is 1550r/min and the feeding quantity is 1.8kg/s, the parametric analysis shows that the radial paddle is able to match this operating condition perfectly. The optimum match results between the kinematic parameter and structural parameter are also validated through the power consumption test.The research results in this paper will play a significant role in decreasing the power consumption and provide the feasible theoretical reference for further designing the impeller blowers.