Simulation and Optimization of an Adjustable Inlet Guide Vane for Industrial Turbo Compressors

Abstract

To investigate the kinematics and dynamics of an adjustable inlet guide vane mechanism (IGV) for industrial turbo compressors, an IGV was modeled as a multibody system (MBS) consisting of elastic interconnections and rigid bodies. Besides investigating the IGV kinematics, its vibrations and structural strength were also verified numerically. The kinematic analyses enabled the design to be optimized in terms of undesirable collisions between the interconnected bodies. The pressure exerted on the guide vanes, which is calculated by CFD simulations, forms a set of forces and torques for each blade. These sets were created for two different performance maps, referred to in the following as Gas I and Gas II. Calculating the desired drive torque, joint reaction forces and the driving ring’s displacements were the essential inputs for the dynamic multibody analyses performed. These investigations showed that the desired torque to drive the mechanism is governed by the sliding element’s friction forces. The gas forces were able to raise the torque by roughly 6% and 32.6% for Gas I and II, respectively. Due to uncertainties in the determination of the friction coefficients, the highest expected values were taken into account for selecting an accurate actuator for the IGV. The strength and vibration analyses were carried out using the Finite Element (FE) Method. All computed critical natural frequencies of the IGV can be empirically considered to be highly damped resonances in the actual system due to joint friction effects. Reaction forces determined by the dynamic multibody analyses were transferred as loads to the FE model. In most cases, the joint reaction forces have been so low that no further investigations were necessary. Hence, verification of strength was carried out using a contact FE analysis for the highest loading condition between the assembly and the pin, which transfers the entire drive force from a lever into the driving ring.