Abstract
The choice of the structure of the mathematical model of thermal-hydraulic processes in the oil cavities of the GTE rotor supports has been substantiated. A three-dimensional CFD model has been built to calculate multiphase currents involving information on the flow distribution and heat exchange given in the scientific literature. We have considered the approaches and individual models used for these purposes. The resulting solutions are consistent with the results of the experiment on a model support and generally accepted ideas about the processes in a given class of devices. The distribution of oil in the chamber, the phase current lines, the temperature and velocity fields have been given, as well as the velocity vectors for various CFD models (VOF, Euler, Inhomogeneous) and solver types (steady and non-steady). Based on the analysis of the results obtained, it has been found that the Euler model involving a non-steady solver yields the smallest difference with the experimental values for a heat transfer coefficient. In all cases, when gravity is considered, there is an asymmetrical distribution of the oil film. The result is a change in the thermal resistance of the boundary layer and, consequently, in the heat transfer coefficient along the bearing chamber circumference. This largely determines the heat flow through the chamber wall. The proposed method of modeling workflow in the support's oil cavity is based on a mathematical notation of the heterogeneous monodisperse oil-air flow with an algorithm of inversion of the structure of two-phase flow in the near-wall region from the drip into the bubble. That makes it possible to more accurately calculate the temperature states of the GTE rotor support elements and the system that ensures the proper operation of the bearing by correctly determining the heat transfer coefficient on the part of the oil-air mixture. The constructed model makes it possible to numerically investigate the applicability of those known and to derive the new correlation dependences for the mean value of aheat transfer coefficientin the oil cavity of rotor support that is used in engineering calculations. The model also makes it possible to numerically investigate the impact of the geometry, the rotor rotation frequency, and the phases flow rates on heat output in the oil cavity
Highlights
The development of aircraft gas turbine engines (GTE) is inextricably linked to increasing the degree of rise in the pressure and temperature of the gas at the inlet to the turbine while reducing the mass and dimensions of the structure, the cost of auxiliary systems
Improving the efficiency of GTE and developing new energy-efficient technologies in the engine industry inevitably sets the tasks of improving the oil systems, which is implemented by reducing the supply of oil to friction nodes in the supports of the GTE rotors and by the rational design of the support nodes
The following tasks have been set: ‒ to justify the choice of the structure of an oil-air flow model in the oil cavity of the GTE rotor support based on the analysis of the workflow; ‒ to build a three-dimensional computational fluid dynamics (CFD) model of thermal-hydraulic processes in the oil cavity using the information on flow distribution and heat exchange given in the scientific literature; ‒ to analyze the impact of common approaches, models of individual processes, and boundary conditions, on the results of calculations and their alignment with experimental data
Summary
The development of aircraft gas turbine engines (GTE) is inextricably linked to increasing the degree of rise in the pressure and temperature of the gas at the inlet to the turbine while reducing the mass and dimensions of the structure, the cost of auxiliary systems. Due to the rotation of the flow and gravity, there is significant heterogeneity in the distribution of oil and, as a result, in the heat transfer coefficient along the wall of the chamber that forms the oil cavity. The generalizing dependences are rare and their applicability for oil cavities of the rotor supports of an aircraft GTE needs to be checked given significant differences in the geometry and mode parameters. The relationship between the thermal and hydrodynamic processes, the complexity of the chamber geometry that forms the oil cavity and the boundary conditions require that its determination should employ simulation techniques based on the mechanics of multiphase environments and computational fluid dynamics (CFD). Research conducted by Safran, Rolls-Royce, and others companies testifies to the relevance of this task and such an approach to modeling
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