Transient Characteristics of Three-Dimensional Flow in a Centrifugal Impeller Perturbed by Simple Pre-Swirl Inflow
Abstract
:1. Introduction
2. Numerical Setup
2.1. Physical Model
2.2. Numerical Methods
2.3. Grid Sensitivity Study
3. Results and Discussion
3.1. Development of Pre-Swirl Inflow
3.2. General Flow Patterns
3.3. Three-Dimensional Flow: Blade-to-Blade Distribution
3.4. Three-Dimensional Flow: Hub-to-Shroud Distributions
3.5. Pressure Gradient Field on the Blade Surfaces
3.6. Topology of Limiting Streamlines
4. Conclusions
- (1)
- The temporal fluctuation of flow is weak at the inlet of the blade channels (r* = 0.0). Close to the suction surface, the magnitude of radial velocity Vr for the counter-rotating inflow is 15–25% larger compared to the co-rotating inflow cases. The peak magnitude reaches the maximum about 2.5 m/s near the suction surface. In the middle of the channels (r* = 0.5), the peak magnitude of Vr moves from suction to pressure surface as the inflow gets from co-rotating to counter-rotating, and the fluctuating amplitude greatly increases, and the magnitude of Vr varies from 0 to 1.2 m/s. The fluctuation is highest at the outlet of the channels (r* = 1.0) especially for the counter-rotating inflow cases. The magnitude of circumferential velocity Vθ reaches the minimum in the central channel for the counter-rotating inflow cases, and the minimum value reaches about 2.2 m/s.
- (2)
- The internal flow of the impeller is highly three-dimensional in the hub-to-shroud direction. The strongest fluctuation of Vr occurs in the central region of the channel for the co-rotating inflow cases, while the peak is observed close to the hub for the counter-rotating inflow cases which can be negative as a result of the separated vortex. Close to the hub, compared to the zero-swirling inflow, the magnitude of Vr near the pressure surface is smaller for the co-rotating inflow cases and the degree of reduction increases with the increase in rotating speed, while for the counter-rotating inflow cases the magnitude of Vr reaches 1.25 m/s, which is 25% larger for the zero-rotating inflow cases. On the contrary, near the suction surface the magnitude of Vr is smaller for the counter-rotating inflow cases about 50–75%, compared to the co-rotating cases. For the circumferential velocity Vθ, great fluctuation appears in the central region and close to the shroud for the co-rotating inflow cases, while in the central region and close to the hub for the counter-rotating cases.
- (3)
- Both pressure and suction surfaces of the blade are mainly occupied by an adverse pressure gradient field. There is no obvious separation on the pressure surfaces because of the weak APG, and small-scale vortices appear on the suction surface around the leading edge.
- (4)
- Three-dimensional separation and reattachment of flow occur around the leading edge of the blade are observed by the limiting streamlines, while the internal flow is quite stable and uniform in the middle and downstream sections of the channels. Reattachment also occurs at the central region of the suction surface for the zero-swirling inflow, and the counter-rotating inflow could reduce the reattachment which improves the uniformity of the internal flow.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Parameter | Value |
---|---|
Inlet Diameter, D1 (mm) | 71.0 |
Outlet Diameter, D2 (mm) | 190.0 |
Inlet height, b1 (mm) | 13.8 |
Outlet height, b2 (mm) | 5.8 |
Blade thickness, t (mm) | 3.0 |
Number of blades, Z | 6 |
Inlet angle, β1 (deg) | 19.7 |
Outlet angle, β2 (deg) | 18.4 |
Blade curvature radius, Rb (mm) | 70.0 |
Specific speed, Ns | 26.3 |
Parameter | Value |
---|---|
Q/Qd | 1.0 |
Flow rate, Q | 3.06 |
Head, H | 1.75 |
Rotation speed, n | 725 |
Reynolds number, Re | 1.4 × 106 |
Grid Number | Head | |
---|---|---|
Grid 1 | 4,740,324 | 2.42 |
Grid 2 | 5,598,924 | 2.51 |
Grid 3 | 7,642,362 | 2.31 |
Grid 4 | 9,185,268 | 2.38 |
Experiment [2] | 2.41 |
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Wang, Z.; Zhang, W. Transient Characteristics of Three-Dimensional Flow in a Centrifugal Impeller Perturbed by Simple Pre-Swirl Inflow. Processes 2022, 10, 2007. https://doi.org/10.3390/pr10102007
Wang Z, Zhang W. Transient Characteristics of Three-Dimensional Flow in a Centrifugal Impeller Perturbed by Simple Pre-Swirl Inflow. Processes. 2022; 10(10):2007. https://doi.org/10.3390/pr10102007
Chicago/Turabian StyleWang, Ze, and Wei Zhang. 2022. "Transient Characteristics of Three-Dimensional Flow in a Centrifugal Impeller Perturbed by Simple Pre-Swirl Inflow" Processes 10, no. 10: 2007. https://doi.org/10.3390/pr10102007