Optimization of a Spring Bearing for Gravitational Forces Compensation Based on Unified Finite Element Analysis
|Keywords||Spring Bearing, Average Membrane Stress, Bending Stress, Optimal Configuration|
|Programs in use||SIMULIA/ABAQUS, modeFRONTIER|
In the petrochemical industry, catalytic cracking is one of the major steps in the process of splitting large hydrocarbon molecules into smaller, more useful components for gasoline and jet fuel. The cracking system itself consists of a reactor and a regenerator that are interconnected by a catalyst pipeline network. Spring bearings are necessary to decrease the gravitational loads acting on the nose pieces.
The whole construction has 9 spring bearings. Spring bearing consists of the Hanger (for suspension), the Cylinder with holes and the Patch between the Wall and the Cylinder.
A goal of optimization was to minimize the mass of the most loading bearing changing a few parameters of the Cylinder, the Hanger and the Patch.
According to Russian State Standard Specification (GOST) the strength of this construction has to be estimated by two criteria:
1. The maximum value of the Average Membrane Stress (σm) has to be less than 162 MPa;
2. The maximum value of the Average Membrane plus Bending Stress (σm+σb) has to be less than 211 MPa.
In this case the stress intensity around the area of the load has not been considered. Stresses σm and σb have been calculated by the procedure of stress linearization through the thickness which has been performed for the regions with the most stress intensity.
To satisfy the requirements of the total area of the holes, the initial designs of experiment have been chosen using CSP-method (Constraint Satisfaction Problem). Algorithm MOGA-II has been used for optimization.
The mass of the spring bearing of new configuration is 2,9 times less than spring bearing’s mass of initial configuration (Fig. 1).
Figure 1. The initial and the optimal configurations
The comparison of stress distribution of the initial and optimal configuration shows that the optimal bearing is much closer to a full-strength construction (Fig. 2) and it has fewer regions with low stress intensity.
Figure 2. Stress Intensity of the Initial and Optimal Configurations
The end-point analysis shows that the Thickness, the Length of the Cylinder and the size of the Patch have the greatest influence on the mass (Fig. 3).
Figure 3. The importance of each variable on the overall project