Abstract
Abstract A series of computational fluid dynamics (CFD) simulations are performed to analyze the effects a rotor off-take bleed has on the performance of an intermediate compressor duct (ICD). To validate the CFD results, a comparison is made to measurements obtained from an experimental facility located at GKN Aerospace Engine Systems in Sweden. To achieve a deeper understanding of the flow physics, hybrid Reynolds-averaged Navier–Stokes/large eddy simulation (RANS/LES) simulations are performed for a single operating condition. The CFD simulations are capable of predicting the behavior when extracting large amount of air through the bleed pipe, where an improved prediction is obtained with the hybrid simulation. The performance of the ICD is severely compromised with increased amount of bleed as the flow delivered to the downstream component is highly disturbed. The disturbed flow is caused by the extraction of axial flow through the bleed pipe, increasing the incidence into the low-pressure compressor’s outlet guide vanes (OGVs) resulting in unfavorable velocity profiles into the ICD. This behavior causes the flow to separate at the OGV blades, where the separation increases with increasing bleed. Furthermore, when including the full bleed system, significant circumferential distortions are observed, showing the necessity of the integrated design.
Highlights
The demand for highly efficient aircraft engines has risen over the past decades and pushed engine manufacturers to seek for further improvements
Series of simulations were performed on a geometry of an experimental rig, which represents an intermediate compressor duct (ICD) from an aircraft engine
The aim was to study the effects on the ICD performance when removing 0%, 10%, 30%, and 40% of the inlet mass-flow through a bleed pipe located upstream of the ICD
Summary
The demand for highly efficient aircraft engines has risen over the past decades and pushed engine manufacturers to seek for further improvements. This has led to the development of high-bypass-ratio turbofan engines with large fans and high-pressure ratio engine cores. To get an efficient compression, the LPC tends to have large hub-to-tip ratio, whereas the HPC has lower radius to limit the tip leakage losses and reduce the weight of the rotor disk. To lead the flow through the radial offset, it is common to use an S-shaped duct, where the radial offset between the LPC and the HPC is increasing with the evolution of increased bypass-ratio engines. The ICD design should deliver reasonable inlet conditions to the HPC as highly disturbed flow has negative impact on the HPC’s performance
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