Effects of Probe Stem Surface Suction on the Aerodynamic Performance of a Compressor

Pneumatic probes can be used to obtain the flow field parameters such as pressure, temperature and air flow angle, and has been widely used to measure the flow field in compressors. When probes are inserted into the compressor to measure the flow field, the probe stems will cause blockage in the flow field and interfere with it, reducing the pressure ratio and efficiency of the compressor. This paper proposes a method to reduce the interference of the stems by their surface suction. Three-dimensional models of a compressor with different types of probe stems were established. Computational Fluid Dynamics (CFD) simulations of the flow within a low-speed compressor without/with the probe stems and the stems having surface suction holes were conducted. The involved numerical methods were validated by the experimental data. The effects of the surface suction holes on the performance of this compressor were compared and analyzed in terms of blockage coefficient in the passage by the vortex identification method. The results show that probe stem surface suction can reduce the blockage of the stems on the downstream flow field. Compared with the situation of no suction, there is an optimal suction mass flow rate that can minimize the adverse effect of probe stems on the compressor aerodynamic performance. For the same type of the probe stems, the compressor performances, i.e., pressure ratio, efficiency and stability margin, are recovered with the increase of the number of suction holes along the span-wise direction.

Cardboard Box Depalletizing Robot Using Two-Surface Suction and Elastic Joint Mechanisms: Mechanism Proposal and Verification

This paper proposes a new method for a depalletizing robot in distribution center to transfer cardboard boxes. Through the use of elastic joint mechanisms, the proposed method reduces the deformation and breakage of cardboard boxes as well as shifts in position and posture due to collapses of the stacks. To validate the proposed method, we developed a linear depalletizing robot that consists of a main arm that supports a vacuum suction type end effector via elastic joint mechanisms and a conveyor arm for conveying cardboard boxes. The proposed transfer method is characterized by a series of actions using the elastic joint mechanisms of the end effector to pick up and lift a cardboard box by two of its sides and then tilt and take it out of a roll box pallet on a conveyor. Tests show that the robot can successfully transfer cardboard boxes using only simple motions in spite of various changes in box position and posture, and that the new joint mechanisms operate effectively.