Abstract
Increasingly, the turbomachinery industry is facing issues related to high temperatures and oil misting inside coupling guards. This leads to machinery downtimes and loss of revenue. Many in the turbomachinery industry are investing significant time and effort to reduce heat generation inside coupling guards. The present computational fluid dynamics (CFD) investigation of Air+Oil flow and heat transfer in the coupling guard was conducted to investigate these issues. In prior investigations, the emphasis has been mostly placed on predicting temperature by modeling pure airflow in the coupling guard. This paper presents CFD simulations completed under two conditions: 1) with pure AIR -in a Single phase and 2) a multi-phase fluid combining Air+Oil.
The coupling guard geometry is cylindrical in nature. Given the symmetry in the geometry, a 90-degree sector was modeled, allowing significantly smaller meshes and lower run times without compromising quality. In this paper, the modeled geometry includes both Fluid + Solid domains that do not contain an inlet or outlet. This work explains the CFD methodology for multiphase and conjugate heat transfer analysis.
The objective of this paper is to predict the temperature on the coupling guard considering Air + Oil flow and heat transfer. The domain evaluated consists of several stationary and rotating components. The CFD domain used for the conjugate heat transfer analysis consists of fluid between the rotating shaft and the stationary cover. The solid domain includes the coupling guard cover. The commercially available software ANSYS CFX 18.1 was used. The mesh was created using Tetrahedral/Prism elements. Both steady-state and unsteady CFD analyses were completed. As noted, multiphase CFD analyses were carried out using Air and Oil VG68 as a homogenous type of mixture.
Detailed flow field characteristics (total and static temperature, pressure, streamlines colored by Mach number, etc.) and CFD-predicted temperatures are compared between the Pure Air and Air+Oil simulations. Also, available measurements were used to validate the CFD results. Temperature results obtained from the CFD simulations were found to be in good agreement with the experimental data. The CFD modeling approach developed can be used to design coupling guards with lower surface temperatures.
A computationally efficient method for full-core conjugate heat transfer modeling of sodium fast reactors
