Key Takeaways & Executive Findings
- •• Rotational speed has a greater impact on total power loss than oil inlet temperature in accessory gearboxes. • Bevel gears and input shaft bearings are the primary contributors, accounting for nearly 50% of total power loss. • The MPS method effectively calculates flow fields and convective heat transfer coefficients in gearboxes. • A combined MPS and finite element thermal network approach balances accuracy and efficiency for temperature field prediction.
Abstract
The accessory gearbox is a vital component of aviation engines, and its power loss, flow characteristics, and temperature distribution significantly influence engine performance, particularly under high-temperature and high-speed conditions. However, research on the thermal and flow characteristics of entire transmission systems remains limited. This study presents a mathematical model designed to evaluate power loss and heat generation within the transmission system of an accessory gearbox. The Moving Particle Semi-Implicit (MPS) method, a Lagrangian numerical technique for fluid dynamics, was utilized to calculate the flow field of the gearbox and determine the surface convective heat transfer coefficient under stable flow conditions. Subsequently, a three-dimensional finite element thermal network method was employed to calculate the gearbox temperature distribution. This method captures detailed temperature fields of key components while estimating other components using lumped parameters, effectively balancing accuracy and efficiency in temperature field calculations. The results indicate that rotational speed has a greater impact on total power loss than the oil inlet temperature. The bevel gears, which are responsible for power input, along with the input shaft bearings, are the primary contributors to power loss, collectively accounting for nearly 50% of the total power loss. This research introduces a predictive method for examining the thermal and flow characteristics of aviation transmission systems, facilitating rapid forecasting of the flow field, temperature distribution, and power consumption.
1. Introduction
An accessory gearbox drives critical components such as the fuel system, lubricating oil system, and hydraulic system of aero-engines. As such, its performance directly impacts the overall operation of the aero-engine. The transmission system of the accessory gearbox is complex, featuring numerous high-speed gears and bearings. The frictional power loss of the gears and bearings and windage loss caused by high-speed gears convert into heat and noise [1]. If the heat generated in the gearbox is not promptly dissipated by the lubricating oil, excessive temperature may damage the gears, bearings, and housing [2, 3], significantly challenging the gearbox’s lubrication and heat dissipation capabilities.
With increasingly stringent requirements for reliability and efficiency, the transmission systems’ flow field, temperature field, and efficiency have become a new research focus. Diab et al. [4, 5] conducted windage loss tests on gears with varying geometric parameters, showing that windage loss is proportional to the cube of rotational speed or pitch radius. Winfree et al. [6] installed baffles around high-speed bevel gears to study the impact of baffle configurations on windage loss and found that optimal baffle installation can reduce windage loss by up to 70%. Massini et al. [7, 8] used high-speed cameras to capture the process of oil jets impinging on a single rotating gear and discovered that the airflow around high-speed gears could break the oil jet and reduce oil impingement depth. Christian et al. [9] utilized thermocouples to study the heat transfer mechanism of jet impingement on rotating cylindrical specimens. Increasing specimen speed reduced the oil film width and heat dissipation capacity. The oil temperature had a negligible effect on heat transfer. Chen et al. [10, 11] investigated the gear scuffing performance with oil injection lubrication and measured gear temperature with a wireless measurement system, which enabled quick evaluation of the risk of gear scuffing without frequent shutdowns during testing.
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Qinjie Lin, Liangliang Gong, Yongqiang Xu, Caichao Zhu, Huaiju Liu, Zehua Lu (2025). Numerical Analysis of Fluid and Temperature Field of an Accessory Gearbox. Chinese Journal of Mechanical Engineering. https://doi.org/10.1186/s10033-025-01295-7
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Frequently Asked Questions
What is the main objective of this study?
The study aims to develop a predictive method for evaluating the thermal and flow characteristics of an accessory gearbox, including power loss, flow field, and temperature distribution, to improve engine performance under high-temperature and high-speed conditions.
Which numerical methods are used in this research?
The Moving Particle Semi-Implicit (MPS) method is used to calculate the flow field and convective heat transfer coefficients, while a three-dimensional finite element thermal network method is employed to compute the temperature distribution.
What are the key findings regarding power loss?
Rotational speed has a greater impact on total power loss than oil inlet temperature. Bevel gears and input shaft bearings are the primary contributors, accounting for nearly 50% of the total power loss.
How does this research benefit the aviation industry?
It provides a rapid and accurate method for predicting flow fields, temperature distributions, and power consumption in aviation transmission systems, aiding in design optimization and reliability improvement.
What is the significance of the MPS method in this context?
The MPS method, being a Lagrangian technique, effectively handles complex free-surface flows and moving boundaries in gearboxes, enabling accurate determination of convective heat transfer coefficients under stable flow conditions.
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