三方機械工業股份有限公司

1. Introduction

In pneumatic conveying systems, elbows are among the most wear-prone and blockage-prone components. Conventional short elbows, long elbows, and large-radius elbows often cause particles to impact the inner wall at high speeds during direction changes, leading to severe wear, turbulence, reduced conveying efficiency, and increased energy consumption.
The wear-resistant spiral elbow utilizes fluid dynamics principles of Q=AV and Bernoulli’s theorem, forming a spiral chamber with deceleration and pressurization inside the elbow to reduce wear, stabilize conveying, and lower energy usage.

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2. Theoretical Basis

2.1 Flow Equation Q=AV

For gas-solid two-phase flow:

Q=A⋅V

• Q: volumetric flow rate (m³/s)
• A: cross-sectional area (m²)
• V: flow velocity (m/s)

Under steady-state conditions, Q is constant. Increasing A in the spiral chamber reduces V accordingly.

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2.2 Bernoulli’s Theorem

For incompressible flow, neglecting gravitational effects:

P+(1/2)ρV²=constant

As VVV decreases, static pressure PPP rises.
This means that the gradually expanding cross-section of the spiral chamber naturally forms a relative positive pressure zone, while the main pipeline maintains high-speed flow and forms a relative negative pressure zone. The pressure differential promotes smooth material transfer from the chamber outlet to the main pipeline, reducing sharp-turn impacts.

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2.3 Pressure and Velocity Distribution

• Main flow velocity V_1​, pressure P₁​
• Chamber inlet velocity V₂​, pressure P_2​
• Lower chamber velocity V₃​, pressure P_3​

Design yields:

V₁≫V₂>V₃

P₃>P₂≫P₁

This shows the lower chamber has the highest pressure and lowest speed, effectively absorbing impact energy.

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3. Flow Characteristics of the Spiral Chamber

3.1 Gradual Expansion Profile

The cross-section expands from the upper inlet, producing a diffuser-like effect and generating stable vortices that guide material along the outer wall, avoiding direct impacts.

3.2 Flow Direction via Pressure Vectors

The pressure difference between chamber outlet and main pipeline pushes material toward the main outlet, minimizing turbulence-induced energy loss and blockage risk.

3.3 Helical Motion and Flow Straightening in Pneumatic Conveying

During pneumatic conveying, the fluid and particles move in a helical trajectory along the chamber’s curved surfaces. This motion straightens the flow, converting turbulence into smoother streamlines while leveraging positive pressure effects from cross-sectional expansion for natural pressurization.
Since the material and airflow follow the physical helical path with almost no direct impact points, pressure loss is significantly lower than in conventional elbows.

3.4 Advantages in Energy Saving, Decarbonization, and Sustainability

By minimizing pressure loss, the spiral chamber reduces blower load, cutting energy consumption. Over long-term operation, it extends component life and reduces replacement frequency, contributing significantly to energy efficiency, carbon reduction, and sustainable business practices.

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4. Comparison with Conventional Elbows

Item	Short Elbow	Long / Large-Radius Elbow	Tee-Type Deflector	Wear-Resistant Spiral Elbow
Velocity Change	Sudden	Slower but still impact	Deflector-dependent	Smooth deceleration
Pressure Profile	Large drop	Moderate	Prone to build-up	Positive-negative synergy
Wear Location	Bend point	Bend point	Outlet end	Distributed along outer wall
Energy Consumption	High	Medium	Medium-high	Low
Pressure Loss	Large	Medium	Medium-large	Lowest
Blockage Risk	Medium-high	Medium	High	Low

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5. Special Conditions and Maintenance Measures

• High Temperature: Consider expansion effects on velocity and pressure loss (NTP correction).
• High Humidity: Prevent plug formation from material-moisture binding (use dehumidifiers).
• Foreign Objects: Install pre-filters to prevent large particle build-up.
• Shutdown Blockage: Use Prepurge negative pressure cleaning to naturally expel blockages.

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6. Conclusion

The wear-resistant spiral elbow combines gradual expansion geometry with a helical guiding chamber, achieving:

1. Reduced wear via helical deceleration and pressurization
2. Blockage prevention through pressure-differential flow guidance
3. Minimal pressure loss for significant energy and carbon savings
4. Extended service life and lower maintenance costs

It is an ideal high-efficiency replacement for conventional elbows in high-wear, high-throughput, or long-distance pneumatic conveying systems, enabling both environmental and operational benefits.