Steady-flow analysis of low pressure compression system for turbofan engines

This paper has two main objectives. It first aims at presenting a method of prescribing boundary conditions for the steady-state flow simulations of low pressure compression systems for turbofan engines. The methodology is generic and it can be applied for steady and unsteady flow simulations of numerous similar multi-component applications. The basic idea is to extend the flow domain upstream to the far field and downstream beyond the first set of stator vanes, both in the bypass and core, where variable area nozzles are used. Fixed static pressure boundary conditions are used downstream of the nozzles which are representative of downstream blockage. With such an approach, the need to prescribe accurate boundary conditions immediately upstream and downstream of the fan is eliminated. An iterative approach is then used to obtain the correct bypass ratio. The second objective of the paper is to demonstrate the use of the methodology in mapping out the loss loop for the outflow guide vanes (OGV) and examine its effects on fan performance. Wherever possible, predictions were checked against measured data and good overall agreement was obtained.