Abstract: This paper explores the optimal layout parameters for lubrication nozzles in high-speed spur gear. Computational fluid dynamics (CFD) transient simulation methods are employed to analyze the single-phase flow field around gear meshing at various linear speeds. The pressure distribution and airflow patterns in the gear meshing area and around the tooth profiles are revealed. A method for determining the optimal nozzle arrangement is proposed and validated through two-phase transient oil injection lubrication simulations.
1. Introduction
High-speed and heavy-duty spur gear transmissions are developing rapidly. Under such harsh conditions, inadequate lubrication on the tooth surfaces can lead to direct friction, generating substantial heat and rapidly increasing the temperature of the meshing tooth surfaces. This can ultimately result in wear or scuffing failure of spur gear teeth, severely affecting gear transmission performance. Therefore, it is crucial to investigate the pressure distribution and airflow patterns around the high-speed spur gear meshing area and optimize the nozzle arrangement parameters for efficient lubrication.
| Research Focus | Details |
|---|---|
| Pressure distribution & airflow patterns | Around spur gear meshing area and tooth profiles |
| Lubrication nozzle arrangement parameters | Optimization to overcome air barrier effects and enhance lubrication efficiency |
2. Numerical Simulation of Single-Phase Flow Field for High-Speed Spur Gear
2.1 Basic Control Equations
Fluid flow is governed by fundamental physical conservation laws, including the conservation of fluid volume, mass, and momentum, described by various mathematical equations.
- Fluid Volume Conservation Equation:∑qq=1αq=1\sum_{q} q = 1 \alpha_{q} = 1∑qq=1αq=1where αq\alpha_{q}αq is the volume fraction of the qthq^\text{th}qth phase fluid.
- RNG k-ε Turbulence Model:Controlled by turbulent kinetic energy kkk and dissipation rate ε\epsilonε.
2.2 Simulation Setup and Mesh Independence Verification
Gear parameters are summarized in the table below:
| Gear Parameter | Active Gear | Driven Gear |
|---|---|---|
| Number of teeth | 25 | 33 |
| Module (M) / mm | 4 | 4 |
| Pressure angle (β) / ° | 20 | 20 |
| Tooth width (B) / mm | 28 | 28 |
A three-dimensional model of the computational fluid domain is established, and fluid tetrahedral meshing is performed using ANSA software. Grid independence verification is conducted, and the final mesh size is determined to ensure computational efficiency and accuracy.
| Mesh Size | Value (mm) |
|---|---|
| Gear teeth & meshing area | 0.5 |
| End face (away from teeth) | 2.5 |
| Gearbox | 4 |
| Total mesh elements | 1.24 million |
2.3 Simulation Results and Analysis
Pressure Analysis:
- Positive high-pressure zones form on the meshing-in side, and negative low-pressure zones form on the meshing-out side.
- With increasing gear linear speed, the maximum positive pressure on the meshing-in side significantly increases, and the pressure difference in the meshing area also substantially increases.
| Gear Linear Speed (m/s) | Maximum Pressure (Pa) | Pressure Difference (Pa) |
|---|---|---|
| 40 | Low | Low |
| 80 | Medium | Medium |
| 120 | High | High |
| 160 | Very High | Very High |
Velocity Analysis:
- The airflow velocity increases significantly near the tooth profiles with higher gear linear speeds, enhancing the air barrier effect.
- The symmetry of the airflow velocity contour deteriorates, and the airflow becomes more turbulent.
3. Optimization of Nozzle Layout Parameters
3.1 Definition of Nozzle Orientation Parameters
| Parameter | Description |
|---|---|
| (S, H, N) | Nozzle coordinates (offset distance, vertical distance, end face offset distance) |
| α | Injection angle (angle between the nozzle and the tangent line to the pitch circles) |
| γ | End face angle (angle between the nozzle jet direction and the plane of the gear center) |
3.2 Optimization Analysis of Nozzle Layout
Determination of Layout Area:
- Based on airflow velocity vectors, nozzles should be placed on the meshing-in side to reduce the adverse effects of the air barrier.
| Placement Area | Advantages |
|---|---|
| Meshing-in side | Promotes oil flow towards the meshing area |
| Meshing-out side | Hinders oil flow and may cause oil to be carried away from the meshing area by airflow |
Determination of End Face Angle:
- An end face angle of 0° is optimal, aligning the oil trajectory with the airflow to minimize adverse effects.
| End Face Angle (γ) | Effect on Oil Trajectory |
|---|---|
| γ ≠ 0° | Oil trajectory susceptible to deviation by lateral airflow |
| γ = 0° | Oil trajectory aligns with airflow, promoting effective lubrication |
Determination of Coordinate Position:
- Based on airflow velocity streamlines, the optimal nozzle position is identified as (1, 39.98, 0) with a jet distance of 40 mm.
| Nozzle Position | Coordinates (S, H, N) | Jet Distance (L) | Effectiveness |
|---|---|---|---|
| Optimal | (1, 39.98, 0) | 40 mm | High lubrication efficiency |
Determination of Injection Angle:
- The optimal injection angle is 21°, ensuring the oil trajectory aligns with the airflow direction.
| Injection Angle (α) | Effect on Oil Distribution |
|---|---|
| 0° | Oil trajectory prone to deviation due to asymmetric airflow |
| 21° | Oil trajectory aligns with airflow, ensuring uniform lubrication |
4. Two-Phase Transient Oil Injection Lubrication Simulation
A two-phase transient oil injection lubrication simulation model is established to validate the optimized nozzle arrangement.
| Simulation Parameters | Value |
|---|---|
| Nozzle diameter | 2.4 mm |
| Oil injection pressure | 0.25 MPa |
| Oil density (ρ) | 904.27 kg/m³ |
| Oil viscosity (μ) | 0.00217 Pa·s |
The simulation results show that the oil trajectory aligns well with the airflow velocity streamline, entering the meshing area smoothly. The volume fraction of oil on the tooth surfaces is uniform, with an average value above 0.8, indicating effective lubrication.
| Lubrication Effectiveness | Value |
|---|---|
| Average oil volume fraction on tooth surfaces | > 0.8 |
Conclusion
This paper presents a method for optimizing the layout parameters of lubrication nozzles for high-speed spur gear. Through CFD transient simulations, the pressure distribution and airflow patterns around spur gear meshing area are revealed. The optimal nozzle arrangement is determined, ensuring effective lubrication. This research provides valuable insights for the design of lubrication systems in high-speed and heavy-duty spur gear transmissions.