Key Takeaways & Executive Findings
- •• • The asterisk-shaped orifice plate (米字形) maximizes gas-liquid turbulent mixing intensity, outperforming annular and parallel arrangements; this directly enhances oxygen transfer efficiency in high-strength wastewater treatment. • • Increasing hole number and diameter reduces throttling resistance, causing average pressure, velocity, turbulent kinetic energy, and dissipation rate to decline by up to 60% (from 5×10^5 Pa to 2×10^5 Pa) across tested configurations; this trade-off must be optimized for energy-efficient operation. • • With 9 triangular holes, mass transfer efficiency is significantly improved, while a 7 mm hole diameter yields optimal balance between energy utilization and mixing performance, as evidenced by pressure and velocity field measurements. • • Moving the porous plate from position I (50 mm) to position III (150 mm) from the nozzle intensifies turbulence and bubble breakup, but position III with triangular plates provides sustained pressure stability, crucial for maintaining aeration performance under variable flow conditions.
Abstract
Air-supplied jet aerators, combining hydraulic jet and gas induction principles, are critical equipment in aerobic biological wastewater treatment. However, low energy conversion efficiency and insufficient local gas-liquid mixing are core bottlenecks limiting their competitiveness. A three-dimensional flow field analysis method for jet aerators was developed based on the k-ε turbulence model and Euler-Euler multiphase flow model. The effects of different orifice plate distributions, shapes, sizes, hole numbers, and installation positions on average pressure, turbulent kinetic energy, and turbulent dissipation rate were systematically studied. Results show that the asterisk-shaped orifice plate yields the highest gas-liquid two-phase turbulent mixing intensity, followed by the annular shape, while the parallel arrangement yields the lowest. With increasing hole number and single-hole size, average pressure, velocity, turbulent kinetic energy, and turbulent dissipation rate for different plate shapes initially fluctuate downward and then stabilize. When the number of triangular holes is 9, mass transfer efficiency is significantly enhanced, and overall aerator performance is excellent. When the triangular hole diameter is 7 mm, the device achieves an optimal match between energy utilization and mixing efficiency across pressure distribution, velocity field, turbulent kinetic energy, and dissipation rate. The farther the porous thin plate is installed from the sewage nozzle, the further gas-liquid two-phase turbulence is enhanced. Experiments confirm that the boundary layer is fully developed, liquid and air are thoroughly mixed, and the orifice plate promotes bubble breakup and refinement through throttling and collision, significantly improving oxygen transfer efficiency. This research provides a theoretical basis and technical support for the transformation and upgrading of aeration technology towards high efficiency and low carbon, and for extending equipment service life.
1. Introduction
Conventional jet aerators in wastewater treatment suffer from low energy conversion efficiency and inadequate gas-liquid mixing, particularly when handling high-impurity industrial or municipal effluents. Traditional fine-bubble diffusers require extensive pretreatment to prevent clogging, whereas jet aerators with internal porous plates offer a robust alternative by using high-shear forces to strip sludge and eliminate dead zones. However, the design of such plates—hole shape, arrangement, size, and placement—has not been systematically optimized, leaving performance gains untapped.
This study addresses that gap by employing k-ε turbulence and Euler-Euler multiphase models to simulate the internal flow field of a jet aerator with various porous plate configurations. The research quantifies how plate geometry and position affect pressure, velocity, turbulent kinetic energy, and dissipation rate, providing concrete data to guide design improvements. The findings enable engineers to select plate parameters that maximize oxygen transfer while minimizing energy consumption, directly supporting the industry's shift towards low-carbon, high-efficiency aeration technologies.
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WU Yao, HAN Leng, LI Aoqi, XI Wenjun, ZHANG Shinan, ZHANG Anlong (2026). Two-Phase Flow Characteristics of a Jet Aerator with Built-in Porous Thin Plates. Chinese Journal of Environmental Engineering. https://doi.org/10.12030/j.cjee.202509009
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Frequently Asked Questions
What is the optimal hole shape and arrangement for maximizing gas-liquid mixing in a jet aerator with a porous plate?
The asterisk-shaped (米字形) arrangement of circular holes yields the highest turbulent mixing intensity, as evidenced by significant increases in average velocity, turbulent kinetic energy, and dissipation rate compared to annular and parallel arrangements. This configuration promotes bubble breakup and uniform dispersion, critical for oxygen transfer efficiency.
How does the number and size of holes affect the aerator's performance and energy consumption?
Increasing hole number and diameter reduces throttling resistance, leading to lower average pressure, velocity, and turbulent kinetic energy. For example, pressure can drop from 5×10^5 Pa to 2×10^5 Pa. However, an optimal point exists: with 9 triangular holes and a 7 mm diameter, the aerator achieves a balance between energy utilization and mixing performance, as indicated by pressure and velocity field measurements.
What is the effect of plate installation position on flow characteristics and mixing?
Placing the plate farther from the nozzle (position III, 150 mm) enhances turbulence and bubble breakup, but position III with triangular plates provides sustained pressure stability, which is beneficial for maintaining aeration performance under variable flow conditions. Pressure and velocity profiles show distinct patterns: pressure exhibits 'stable decrease-single peak-horizontal overlap', while velocity shows 'horizontal overlap-double peak-accelerated rise'.
Are there any operational issues such as 'air pockets' or uneven mixing with certain plate designs?
Yes, annular and parallel (川字形) arrangements tend to create 'air pockets' at the upper wall, leading to poor gas-liquid mixing uniformity. In contrast, the asterisk-shaped triangular plate arrangement ensures thorough mixing at the nozzle exit, effectively reducing bubble size and enhancing turbulence, thus avoiding such issues.
What is the practical significance of these findings for industrial wastewater treatment?
The optimized porous plate design can significantly improve oxygen transfer efficiency and energy efficiency, reducing operational costs and extending equipment lifespan. The ability to handle high-impurity wastewater without fine pretreatment makes this technology suitable for municipal and industrial applications, aligning with the industry's push towards low-carbon, high-efficiency aeration solutions.
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