Flow mixing and pressure drop characteristics for marine selective catalytic reduction applications were investigated numerically to develop an efficient static mixer. Two different mixers, line- and swirl-type, were considered. The effect of vane angles on the relative intensity, uniformity index, ...
Flow mixing and pressure drop characteristics for marine selective catalytic reduction applications were investigated numerically to develop an efficient static mixer. Two different mixers, line- and swirl-type, were considered. The effect of vane angles on the relative intensity, uniformity index, and pressure drop was investigated in a swirl-type mixer; these parameters are dramatically affected by the mixer geometry. The presence of a mixer, regardless of the mixer type, led to an improvement of approximately 20% in the mixing performance behind the mixer in comparison to not having a mixer. In particular, there was a tradeoff relationship between the uniformity and the pressure drop. Considering the mixing performance and the pressure drop, the swirl-type mixer was more suitable than the line-type mixer in this study.
Flow mixing and pressure drop characteristics for marine selective catalytic reduction applications were investigated numerically to develop an efficient static mixer. Two different mixers, line- and swirl-type, were considered. The effect of vane angles on the relative intensity, uniformity index, and pressure drop was investigated in a swirl-type mixer; these parameters are dramatically affected by the mixer geometry. The presence of a mixer, regardless of the mixer type, led to an improvement of approximately 20% in the mixing performance behind the mixer in comparison to not having a mixer. In particular, there was a tradeoff relationship between the uniformity and the pressure drop. Considering the mixing performance and the pressure drop, the swirl-type mixer was more suitable than the line-type mixer in this study.
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문제 정의
Finally, it can be concluded that the swirl-type mixer with a vane angle of 45 is more suitable model in this study based on the results of mean RI, UIc and pressure drop. Further research focused on the effect of the vane size becoming larger or smaller may be needed under line- and swirl-type mixers. The effectiveness of swirl-type mixers is carefully guessed to be initiated from the larger-scale swirl than those of line-type mixers.
가설 설정
3. However, σ significantly increased near the SCR filter because a large recirculation zone formed in the diffuser region.
제안 방법
2, have 36 vanes each. A swirl-type mixer was developed in this study with several unique features: a simple design for production; a variable vane angle to generate different swirl flows; and the flexibility for installation and to control the mixer volume in the pipe. Both types of mixers with various vane angles were simulated in 3-D to investigate the flow pattern, turbulence characteristics, and uniformity of water, which is assumed to be UWS at the SCR catalyst entrance.
The purpose of this study was to evaluate the effect of mixer geometry on the relative intensity, uniformity index, and pressure drop with the objective of enhancing the de-NOx efficiency. Additionally, information pertaining to the selection of proper static mixers was provided based on the correlation between the uniformity index and the pressure drop.
A swirl-type mixer was developed in this study with several unique features: a simple design for production; a variable vane angle to generate different swirl flows; and the flexibility for installation and to control the mixer volume in the pipe. Both types of mixers with various vane angles were simulated in 3-D to investigate the flow pattern, turbulence characteristics, and uniformity of water, which is assumed to be UWS at the SCR catalyst entrance.
In this study, both line- and swirl-type mixers were considered; each mixer was divided into three cases of vane angles: 30º, 45º, and 60º.
Turbulent and swirling flows can also achieve a great improvement for flow mixing with respect to flow recirculation phenomena through a longer distance. In this study, information regarding the selection of proper static mixers was provided based on the correlation between the uniformity index and the pressure drop. The results show that the mixer for SCR applications can be effectively optimized by using a well-designed mixing device.
26). The purpose of this study was to evaluate the effect of mixer geometry on the relative intensity, uniformity index, and pressure drop with the objective of enhancing the de-NOx efficiency. Additionally, information pertaining to the selection of proper static mixers was provided based on the correlation between the uniformity index and the pressure drop.
이론/모형
The effects of a mixer’s geometric structure on the flow mixing characteristics and the resulting pressure drop were investigated numerically using a commercial finite volume, three-dimensional (3-D) CFD code; FLUENT (version 6.3.26).
The standard κ-ε turbulent model was used to calculate the turbulent quantities.
성능/효과
3) The swirl-type mixer is more effective than the line-type mixer with respect to the enhancement of mixing performance, even though there is a tradeoff relationship between the uniformity index and the pressure drop. Therefore, the swirl-type mixer with a vane angle of 45º is the most suitable model in this study based on the results of both parameters.
When selecting a static mixer in SCR applications, it is necessary to consider the mixing and the uniform distribution of the UWS in front of the SCR reactor as well as the pressure drop, which is not desirable for the optimization of engine power throughout the system. Finally, it can be concluded that the swirl-type mixer with a vane angle of 45 is more suitable model in this study based on the results of mean RI, UIc and pressure drop. Further research focused on the effect of the vane size becoming larger or smaller may be needed under line- and swirl-type mixers.
After this point, RI gradually decreases, and exhibits uniform distributions as it approaches the SCR filter. The maximum RI values were as follows: 1.54% at position 1 for case 1, 1.96% at position 5 for case 2, 2.75% at position 2 for case 3, 4.67% at position 2 for case 4, and 2.99% at position 2 for case 5. Incorporating the mixer is most effective for improving mixing performance immediately behind the mixer when the vane angle is greater than 45º.
For all cases, the UIc increased along the stream-wise direction. The maximum values of the UIc were 98.5% for case 4, 96% for case 3, 94% for case 2, 93.6% for case 5, and 90% for case 1. The sequences for the UIc at different position are as follows: case 3 > case 5 > case 1 > case 4 > case 2 before the mixer at the position 1; case 4 > case 5 > case 3 > case 2 > case 1 behind the mixer at the position 2; case 4 > case 3 > case 5 > case 2 > case 1 at positions 3 and 4; and case 4 > case 3 > case 2 > case 5 > case 1 in the right front of the catalyst filter at the position 5.
The sequences for the UIc at different position are as follows: case 3 > case 5 > case 1 > case 4 > case 2 before the mixer at the position 1; case 4 > case 5 > case 3 > case 2 > case 1 behind the mixer at the position 2; case 4 > case 3 > case 5 > case 2 > case 1 at positions 3 and 4; and case 4 > case 3 > case 2 > case 5 > case 1 in the right front of the catalyst filter at the position 5. These results indicate that the UIc increases with increase in the vane angle of the swirl-type mixer, and the cases for the swirl-type mixer generally show better mixing performance than the line-type mixer, even though the line-type mixer outperforms it behind the mixer and in the region of the diffuser. This superior performance is due to a small-scale vortex generated by the up and down induced flow behind the line-type mixer that vanishes rapidly in a short region.
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