CFD Modeling and LDA Measurements for the Air-Flow in an Aero Engine Front Bearing Chamber

Abstract

The continuous development of aero engines toward lighter but yet more compact designs, without decreasing their efficiency, has led to gradually increasing demands on the lubrication system, such as the bearing chambers of an aero engine. For this reason, it is of particular importance to increa.se the level of understanding of the flow fleld inside the bearing chamber in order to optimize its design and improve its performance. The flow field inside a bearing chamber is complicated since there is a strong interaction between the .sealing air-flow and the flow of lubrication oil, and both of them are affected by and interacting with the geometry of the chamber and the rotating shaft. In order to understand the flow field development and, as a next step, to optimize the aero engine bearing chamber performance, in relation to the lubrication and heat trari.sfer capabilities, the behavior of this interaction must be investigated. In this work, an investigation of the air-flow field development inside the front bearing chamber of an aero engine is attempted. The front bearing chamber is divided into two separate sections. The flow from the flrst section passes through the bearing and the bearing holding structure to the second one where the vent and the scavenging system are located. The investigation was performed with the combined use of experimental measurements and computational fluid dynamics (CFD) modeling. The experimental measurements were carried out using a la.ser Doppter anemometry system in an experimental rig, which consists of a 1:1 model of the front bearing chamber of an aero engine. Tests were carried out at real operating conditions both for the air-flow and for the lubricant oil-flow and for a range of shaft rotating speeds. The CFD modeling was performed using a commercial CFD package. Particularly, the air-fiow through the bearing itself was modeled, adopting a porous medium technique, the parameters of which were developed in conjunction with the experiments. A satisfactory quantitative agreement between the experimental measurements and the CFD computations was achieved. At the same time, the effect of the important parameters such as the air and oil mass flow, together with the shaft rotational speed, and the effect of the chamber geometry were identified. The conclusions can be e.xploited in future attempts in combination with the CFD model developed in order to optimize the efficiency of the lubrication and cooling system. The latter forms the main target of this work, which is the development of a useful engineering tool capable of predicting the fiow field inside the aero engine bearing, which can be used subsequently for optimization purposes.

Jet cooling for rolling bearings: Flow visualization and temperature distribution

“…Regarding the oil flow through a bearing compartment, only a relatively small part of the oil is used to form a lubricant film. Most of the oil is used to provide sufficient cooling capability [4,12]. Besides, the heat dissipation characteristic and the oil-air flow characteristic in a bearing can be largely affected by parameters such as pockets shape and contact angle [13,14].…”

“…For high-speed transmission systems, such as aircraft engines, turbomachinery, and drive trains, oil-jet is applied to the ball bearing cooling [4]. The automotive transmission is now focused toward higher efficiency and greater power density [5].…”

Two Phase Flow Pattern of Injection Lubrication in High Speed Bearings

“…Its performance is of vital importance to the dynamic characteristics and reliability of the whole transmission system. But the bearing will produce a lot of heat in high rotation speed, thus affecting the bearing stiffness and high-speed performance, and the friction and wear will affect the bearing reliability and service life [1][2].To achieve accurate lubrication of bearings, not only from the lubrication of bearings start, but more importantly, to understand the flow of oil into the bearings after the actual situation. There are many researches on the lubrication of rolling bearings, but they are based on the study of the pressure distribution and oil film thickness of single-phase flow [3][4][5].…”

Bubble Flow Analysis of High Speed Cylindrical Roller Bearing under Fluid-Solid Thermal Coupling

“…In order to obtain more accurate results, 2 International Journal of Rotating Machinery CFD analysis should be done. Aidarinis et al [8] constructed a CFD modeling for air flow in aeroengine bearing, in which the air flow parameters were developed by the experiments. The efficiency of the lubrication and cooling system was optimized based on the CFD calculation results.…”