Numerical Simulation of Coke Particle Erosion in Elbows with Different Curvature Radii

Literature Overview

This paper by Jiang Chen, Sun Wei, Wang Li, Ren Pingping, Zhang Xiaofei, and Ji Mingyan, published in Pipeline Technology and Equipment (2025, Issue 3, pp. 57-62), presents a numerical simulation study on the erosion behavior of coke particles in elbows with different curvature radii. The authors employed the Realizable k-epsilon turbulence model and computational fluid dynamics (CFD) methods to analyze the fluid characteristics, pressure distribution, and particle trajectories within nine different curvature radius configurations. The study aims to identify the optimal curvature radius for minimizing erosion in coke particle transport systems.

Core Technical Content and Methodology

Coke particle transport systems are common in coal chemical and metallurgical industries, where abrasive solid particles are conveyed through piping networks. Elbows represent critical erosion locations because the flow direction change causes particle impact on the inner wall, leading to material loss and eventual failure. The authors systematically studied nine curvature radius configurations to establish quantitative relationships between geometry and erosion behavior.

Key Findings on Erosion Behavior

The simulation results reveal several important patterns:

Secondary flow develops in the elbow section due to centrifugal force acting on the continuous phase, creating local turbulence and flow disturbance that enhances particle-wall interactions.
As the curvature radius increases, the internal flow field becomes more stable, and the relative velocity between the fluid and the wall decreases, resulting in reduced impact on the inner wall.
Discrete phase (coke particle) erosion of the elbow wall is significantly influenced by the curvature radius, with clear trends in impact pressure and maximum erosion rate.
The study recommends a 4D curvature radius elbow when space is limited, and a 7D curvature radius elbow as the optimal cost-performance ratio option.
Curvature radii of 2D, 3D, 5D, and 6D are not recommended due to suboptimal erosion characteristics or poor cost-effectiveness.

Curvature Radius	Flow Stability	Erosion Rate	Recommendation
2D	Low stability, high turbulence	High erosion	Not recommended
3D	Moderate stability	Moderate-high erosion	Not recommended
4D	Moderate-high stability	Moderate erosion	Recommended (space-constrained)
5D	High stability	Low-moderate erosion	Not recommended (poor value)
6D	High stability	Low erosion	Not recommended (poor value)
7D	Very high stability	Lowest erosion	Recommended (optimal value)

Engineering Practice Implications

For engineers designing coke particle transport systems, this study provides clear guidance on elbow selection. The recommendation of 4D for space-constrained installations and 7D for optimal performance offers a practical decision framework. The finding that 5D and 6D are not recommended despite having lower erosion than 2D-4D is particularly useful, as it highlights that the relationship between curvature radius and erosion is not monotonically linear, and there may be optimal points where the cost of additional material and space does not justify the marginal erosion reduction.

The identification of secondary flow as a key mechanism driving erosion is important for understanding the fundamental physics of particle impact in curved ducts. Secondary flow creates recirculation zones and increased turbulence intensity, which enhance particle-wall collisions. Engineers should consider this when designing erosion-resistant piping systems, as simply increasing wall thickness may not be sufficient if the flow field continues to generate high-impact particle trajectories.

Study Insights and Reflections

This paper provides a systematic and practical approach to optimizing elbow geometry for erosion-resistant design in solid particle transport systems. The use of the Realizable k-epsilon model is appropriate for capturing the turbulence characteristics of particle-laden flows, and the parametric study across nine curvature ratios provides comprehensive coverage of the design space. I find the non-monotonic recommendation pattern (4D and 7D recommended, while 5D and 6D are not) particularly interesting, as it suggests that there are specific flow regime transitions at intermediate curvature ratios that create unfavorable erosion conditions. The study would benefit from experimental validation, as CFD models for erosive wear can have significant uncertainties in predicting actual material loss rates. Nevertheless, this work provides valuable design guidance for engineers in the coal chemical and metallurgical industries who face erosion challenges in coke transport systems.