The method of cavitation is increasingly applied in water environmental protection. Based on the numerical simulation method, a study on the structural parameters of the shear-type hydrodynamic cavitation generators for wastewater treatment is proceeded. The internal flow field is described by employing the mixed multiphase flow model and the Zwart cavitation model. Experiments were conducted by applying the wastewater from a dyeing factory as the medium. The degradation rate of COD in water characterizes the cavitation performance of the hydrodynamic cavitation generator, and the rationality of the numerical simulation approach is validated. The findings indicate that different structural parameters have a great influence on the cavitation performance. The appropriate number of tooth rows creates a flow field with a greater vapor and velocity than the other parameters. The number of teeth in a single row, the outer diameter of the hydrodynamic cavitation generator and the tooth bevel angle also affect the cavitation performance to some extent, and there is an optimal value. The study provides a reference for the applicability of a numerical simulation of the flow field inside the hydrodynamic cavitation generator and the structural optimization of the rotary hydrodynamic cavitation generator.

Pipeline inspection gauges easily become wedged in offshore and onshore small-diameter pipelines (where the outer diameter, D, of the pipe is less than 150 mm), particularly at the bends. To reveal the relationship between PIG capacity and bend curvature radius, a quantitative study on the passing capacity of PIG was conducted in this paper from three key perspectives of performance: safe application, sealing, and driving. The results demonstrate that the pipeline inspection gauge exhibits better passing capacity as the curvature radius of the bend increases. To improve the poorest passing capacity, in the case of R = 3D, different numbers of grooves are opened in the cup. The results demonstrate that the cup with 24 square grooves has a substantial impact on optimizing the passing capacity of the pipeline inspection gauge. This enhancement results in improvements in safe application performance (40.8%), sealing performance (12.22%), and driving performance (17%). This research aims to expand our understanding of blockages in small-diameter pipelines and provide a basis for optimizing the structure of the pipeline inspection gauge for small-diameter pipelines.

This paper presents a comprehensive investigation of flow-induced noise characteristics in ethylene cracking furnace tubes, covering both pre- and post-coking conditions. Large-eddy simulation (LES) was employed in conjunction with a generalized Lighthill’s acoustic analogy model. The results indicate that noise sources can be classified as dipole acoustic sources, with energy primarily concentrated ranged from 300 to 1500 Hz, in comparison to standard conditions. The primary location of the acoustic source was identified in the region commonly referred to as the “necking” of the furnace tube, demonstrating a strong correlation with turbulence intensity near the tube wall. As the coke layer thickness in the furnace tube increased from 5 mm to 15 mm, both the sound power level and turbulence intensity exhibited significant growth. Specifically, the sound power level increased by 60.5% while the turbulence intensity increased by 58.5%. Variations in the overall sound pressure level (OASPL) curve measured within the tube could be utilized to assess coking levels. Significant peaks in the OASPL curve were observed as the furnace tube underwent substantial coking, with coke layer thicknesses of 10 mm and 15 mm. The corresponding OASPL values recorded were 79.25 dB and 119.08 dB, respectively. The findings of this work offer significant insights that may contribute to enhanced safety measures in the operation of ethylene cracking furnace tubes.