Abstract
The article covers the CFD analysis of the compressed air rotary lobe expander. Compressed air engines are commonly used in the explosion hazard zones, where the others power sources cannot be applied. The lobe construction seems to be cheaper solution in comparison with the classic turbine expanders at the corresponding power level. In the paper the rotary lobe compressed air expander model was developed in the ANSYS CFX software. During implementation of the proposed numerical model the mesh motion problem was solved, which was challenging due to relatively small gaps between lobes and the housing as well as due to high rotary speed of lobes. What is more, the compressible fluid model was applied. Therefore, these conditions make the undertaken problem more complex and calculation more time consuming. Finally, the model was validated applying the catalogue data of the producer. In the paper description of the developed model was presented. Then the results of simulations with their validation were shown which proved the correctness and accuracy of the model. The developed tool might be very useful for the further analysis of the expander including its optimization in terms of improvement of its efficiency or energy gain.
Highlights
The rotary lobe compressed air expander which is the object of the investigation in this paper in most cases is applied as the part of air motors
Such a procedure was necessary to obtain the actual value of the torque acting on the rotor, because at specific positions of the rotors, the force direction is unsuitable because it acts on the opposite direction to desired one
The forces acting on the rotors and the power calculated on their basis show cyclicality resulting from the constant rotational speed of the rotors and the regular opening and closing of the space between the rotors and the walls of the expander
Summary
The rotary lobe compressed air expander which is the object of the investigation in this paper in most cases is applied as the part of air motors. The main advantage of gas expanders is the lower cost of application comparing to conventional turbine motors at the corresponding power level, combined with arduous and long-life systems. In this paper the model of the rotary lobe compressed air expander was developed with the consideration of industrial solutions. The torque is developed by the larger rotor situated in the lower part of the housing and transferred to the rotating shaft by a synchronizing gear train. To preserve high efficiency of the expander, air gaps between the rotors and housing are relatively small which allows rotation process without physical contact. The frictionless work might result in the long maintenance free operation without downtime in industrial applications [1]
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