This presentation was made at CAASE18, The Conference on Advancing Analysis & Simulation in Engineering. CAASE18 brought together the leading visionaries, developers, and practitioners of CAE-related technologies in an open forum, to share experiences, discuss relevant trends, discover common themes, and explore future issues.

Resource Abstract

Caterpillar is developing compressed air tanks for drilling application in mining division. One of the main challenges in air tank design is to effectively separate and remove lubrication/cooling oil from air stream, to reduce end customer operating cost. Caterpillar teamed up with ANSYS to simulate oil/air separation process using DPM (Discrete Phase Model) on multiple tank designs, to understand and improve oil/air separation efficiency.

A 3D CAD model representing the tank interior as well as the discharge pipe was created and meshed. The mesh was imported into ANSYS FLUENT to setup material flow rates and boundary conditions. Since, the flow spirals through this tank, the choice of turbulence model is important. Realizable ke model with curvature correction is used to capture the turbulence in the flow field. Air is modeled as an ideal gas. In order to capture areas with high gradients, dynamic mesh adaption is used. After establishing a converged airflow path, oil droplets of a uniform diameter are introduced from the inlet, and are tracked in a coupled manner. A standard parcel release method is used to define the oil injection. Numerical techniques are used to under-relax and smooth out source terms. Unsteady tracking of discrete particles is coupled with steady airflow in order to model wall-film formation. Droplet film formation is captured at impingement walls, and subsequent stripping and separation of oil film is included. The KHRT model is used to model airborne breakup of oil particles. The capture efficiency is measured once steady state conditions are reached by monitoring the droplet flow rate across the top and bottom outlets. Droplet diameter and tank height are varied in subsequent simulations, to study their impact on the droplet flow rates across the outlets. Results are used to predict and correlate oil/air separation efficiency in tanks with different designs. Oil/air separation efficiency trend predictions are in good agreement with field data.