Zhuojin Pipe Fitting Co., LtdFlow Splitting Ratio and Internal Flow Characteristics of Tee Regulating Valves
Literature Overview
This paper by Sun Caizhen, Li Hong, and Tang Pan, published in Journal of Drainage and Irrigation Machinery Engineering (2019, Vol. 37, No. 5, pp. 441-446), investigates the flow splitting ratio and internal flow characteristics of a tee-type regulating valve using three-dimensional computational fluid dynamics (CFD) simulation. Funded by the National Natural Science Foundation of China (Grant No. 51679109), the study employed the standard k-ε turbulence model with the SIMPLE algorithm to simulate the internal flow field under varying inlet flow rates and valve spool rotation angles. The simulation results were validated against experimental data, showing good agreement.
Core Technical Analysis
The study systematically examined how the valve spool rotation angle affects the flow splitting behavior and internal pressure distribution:
Flow Splitting Characteristics
| Valve Angle | Horizontal Split Ratio | Dominant Flow Path | Operating Regime |
|---|---|---|---|
| 15° | Low | Primarily vertical | Minimal horizontal flow |
| 35° | ~0.55 (peak) | Balanced horizontal | Maximum horizontal diversion |
| 45° | ~0.45 | Transitional | Pressure peak |
| 55° | ~0.40 (trough) | Reducing horizontal | Minimum horizontal diversion |
| 75° | Approaching 1.00 | Nearly all horizontal | Maximum horizontal flow |
The non-monotonic behavior of the horizontal split ratio is a critical finding. The split ratio first increases to a peak near 35°, then decreases to a minimum near 55°, and finally increases again toward unity. This complex behavior arises from the interaction between the valve spool geometry and the flow field, creating multiple flow regimes within the operating range.
Internal Flow and Pressure Characteristics
The study identified several important flow features:
- Throttling Zone: The connection between the valve inlet section and the spool creates a flow area contraction, resulting in the highest local velocity and maximum pressure in the valve inlet pipe section.
- Pressure Symmetry: The inlet pressure curve exhibits symmetry about 45°, with a peak at this angle. This symmetry corresponds to the symmetric change in the effective flow area at the valve inlet as the spool rotates.
- Turbulent Flow Regime: The standard k-ε turbulence model was found to adequately capture the turbulent flow characteristics in the valve internal passages.
Engineering Practice Implications
The findings have direct relevance to the design and operation of flow control systems in irrigation, hydraulic, and industrial piping applications:
Valve Selection and Sizing
The non-monotonic split ratio behavior means that a simple linear relationship between valve angle and flow splitting cannot be assumed. Engineers must use the actual characteristic curves derived from testing or validated simulation when designing control systems. The effective operating range of 15°-75° provides a useful design parameter for control system calibration.
Pressure Management
The pressure peak at 45° and the high-velocity throttling zone at the inlet-spoo interface are critical for:
- Erosion Assessment: High-velocity zones are susceptible to erosion, particularly in abrasive service.
- Cavitation Risk: Local pressure reduction in high-velocity zones may approach the vapor pressure, creating cavitation risk.
- Noise and Vibration: Flow separation and turbulence in the throttling zone contribute to noise and vibration.
Control System Design
The complex split ratio behavior requires sophisticated control algorithms for precise flow regulation. The symmetry about 45° can be exploited for control system design, but the non-monotonic behavior between 35° and 55° requires careful handling to avoid control instability.
Study Insights and Reflections
This study demonstrates the value of CFD simulation in characterizing the internal flow behavior of complex valve geometries. The validation against experimental data provides confidence in the simulation results and establishes the methodology as a reliable tool for valve design optimization. The non-monotonic split ratio behavior is a particularly important finding that challenges simplified engineering models. For practitioners in irrigation engineering, hydraulic systems, and process piping, this paper provides the quantitative basis for selecting appropriate valve angles for desired flow splitting, and for understanding the internal pressure and velocity distributions that influence valve durability and performance. The study also highlights the importance of considering three-dimensional flow effects in valve design, as simplified two-dimensional or analytical models may not capture the complex flow interactions present in tee-type valve geometries.