Gas phase hydrodynamics in a surface-aerated tank with a long-short blades agitator

This work aims to study the gas phase hydrodynamics in a stirred tank with a surface-aerated long-short blades agitator by the Eulerian‒Eulerian approach coupled with population balance model. Predicted local gas holdup and bubble size distribution agree well with those measured by a conductivity probe technique. The predictions demonstrate that the pressure depression in the center is the main driving force for gas suction and the downward flow carries the bubbles down to redistribute in the whole tank. The gas phase has higher gas holdup with large bubble size in the upper part and lower gas holdup but with small bubble size in the lower part of the tank. The predicted gas-liquid mass transfer coefficients agree well with our previous experimental results and just depends on the power consumption per unit volume when the aspect ratio of the liquid height to the tank diameter varies from 1.1 to 2.0.

How to improve image quality of DWI of the prostate—enema or catheter preparation?

Objectives To compare the impact of laxative enema preparation versus air/gas suction through a small catheter on image quality of prostate DWI. Methods In this single-center study, 200 consecutive patients (100 in each arm) with either enema or catheter preparation were retrospectively included. Two blinded readers independently assessed aspects of image quality on 5-point Likert scales. Scores were compared between groups and the influence of confounding factors evaluated using multivariable logistic regression. Prostate diameters were compared on DWI and T2-weighted imaging using intraclass correlation coefficients. Results Image quality was significantly higher in the enema group regarding the severity of susceptibility-related artifacts (reader 1: 0.34 ± 0.77 vs. 1.73 ± 1.34, reader 2: 0.38 ± 0.86 vs. 1.76 ± 1.39), the differentiability of the anatomy (reader 1: 3.36 ± 1.05 vs. 2.08 ± 1.31, reader 2: 3.37 ± 1.05 vs. 2.09 ± 1.35), and the overall image quality (reader 1: 3.66 ± 0.77 vs. 2.26 ± 1.33, Reader 2: 3.59 ± 0.87 vs. 2.23 ± 1.38) with almost perfect inter-observer agreement (κ = 0.92–0.95). In the enema group, rectal distention was significantly lower and strongly correlated with the severity of artifacts (reader 1: ρ = 0.79, reader 2: ρ = 0.73). Furthermore, there were significantly fewer substantial image distortions, with odds ratios of 0.051 and 0.084 for the two readers which coincided with a higher agreement of the prostate diameters in the phase-encoding direction (0.96 vs. 0.89). Conclusions Enema preparation is superior to catheter preparation and yields substantial improvements in image quality. Key Points • Enema preparation is superior to decompression of the rectum using air/gas suction through a small catheter. • Enema preparation markedly improves the image quality of prostate DWI regarding the severity of susceptibility-related artifacts, the differentiability of the anatomy, and the overall image quality and considerably reduces substantial artifacts that may impair a reliable diagnosis.

Использование шумопоглощающих материалов при проектировании шумозащитных конструкций шахтовых вентиляторных установок на угольных месторождениях Кузбасса

Представлены результаты обследования вентиляторных газоотсасывающих машин УВЦГ-9 на месторождениях Кузбасса в различных частях области. Установлены превышения норм шумовой нагрузки при расположении источников шума вблизи жилых сооружений. Авторами разработаны конструктивные решения с целью поглощения шума от элементов вентиляторных установок. Описана разработанная и собранная авторами лабораторная установка для исследования строительных материалов различных производителей. Приведены результаты авторского анализа представленных шумопоглощающих материалов для разработки блочной конструкции защиты от шума вентиляторной установки УВЦГ-9. На основании полученных авторами результатов экспериментального исследования строительных материалов сделаны выводы о возможности максимального снижения шумовой нагрузки от газоотсасывающей системы. Ключевые слова: шум, вентиляторная установка, шумозащитное укрытие, шумопоглощающий материал, шахтовые вентиляторы, шумоподавление, лабораторная установка, шумозащитный экран. The results of the survey of UVTSG-9 fan gas-pumping units at coal mines of Kuzbass in various parts of the region are presented. Exceedance of rated noise loads has been recorded where the noise sources are located close to the residential premises. Design solutions have been developed to absorb noise from working elements of the fan installations. A laboratory installation for the study of construction materials fabricated by various manufacturers developed and assembled by the authors is described. The results of the analysis of the presented noise-absorbing materials for the development of a block structure for noise protection of the UVTG-9 fan gas-suction unit are presented. Conclusions based on the results of the study of construction materials focused on suppression of industrial noise are duly presented. Keywords: noise, fan installation, noise shelter, noise-absorbing material, mine fans, noise reduction, laboratory installation, noise shield.

Methane Emission Control at the High-Productive Longwall Panels of the Yalevsky Coal Mine

The analysis of the experience of methane emission control at the V. D. Yalevsky mine (Kuznetsk coal basin, Russia) during the series of shallow gassy coal seams mining with the high productive longwall was performed. The analysis of the efficiency of gob degassing by the vertical wells and isolated methane removal by gas-suction fans is performed. The efficiency of reducing the distance between ventilation crosscuts between entries is shown. It is also shown that the problems of providing the longwall high productivity in conditions of increasing the natural gas content in the coal seams are associated with gas emission from the extracted coal seam and the lack of effective methods for its early and preliminary degassing. Recommendations for using advanced mining of close-up coal seams as an effective method of degassing of rock mass within the zone of influence of undermining and overmining are given.

The Investigations of the Balance Hole Area and Radial Seal Clearance’s Influences on Turbine Efficiency in the Wheel Chamber

First of all, this paper presents the overall efficiency correlation to the balance hole diameter of the 3-stages air turbine test results. All 3 wheels have the same balance hole geometry, with total 5 holes in the wheel, and the variation of diameter is 0 mm, 16 mm, 25 mm, 30 mm, 40 mm, 50 mm, and 60 mm, respectively. The test results show that the lowest efficiency condition is the one without balance hole, and increases with the hole diameter until 25–30 mm, but decreases after it. Then, a single stage CFD model, including the first stage stator, moving blade, stator hub leakage, and wheel chamber, is built to simulate the stage efficiency trend under steady flow condition. The relative efficiency correlation of the simplified single stage CFD model matches very well with the test results. The CFD results show that, the maximum efficiency happens when there is minor gas suction from the main gas path, about 0.1%–0.2% compared with the main mass flow, but when the gas suction is above 0.2% of the main mass flow, the efficiency decreases, as less flow is passing through the moving blade to convert energy. Finally, the radial seal clearance’s influences in the wheel chamber between the diaphragm and the wheel is checked by CFD using the same geometry pattern. Five different radial seal clearances model, including 0 mm (ideal condition), 0.6 mm, 1.2 mm, 1.8 mm and 6 mm (without radial seal) are built, under two different balance hole diameter (14 mm and 25 mm), and three different hub seal clearances (0 mm, 0.6 mm and 1.2 mm) conditions. The CFD results show that the throttling effect is very small when the radial clearance is above or equal to 0.6 mm, with almost constant efficiency variation with the clearance up to 6 mm, under specified stator hub clearance and balance hole diameter. Very small deficiency (0.2%) is detected under small balance hole diameter (14 mm) and large stator hub clearance (1.2 mm) condition, as the hub leakage mass flow is much beyond the balance hole flow capability.

Vibration Analysis Based on the Mathematical Model of the Air-Suction Device Tillage Seeder Seeding

In order to study air-suction when tillage planter in the field farming, Vibration due to the surface roughness of the resulting excitation tillage effects on seed planter of the device, Derivation of the air-suction device tillage planter seeder vibration characteristics of the mathematical model, Vibration characteristics of the mathematical model derived gas suction device tillage seeder seed planter primarily by structural properties, Forward speed when operating, Seed row distance between the soil surface, Soil roughness and soil sticky decision. Can predict and analyze working condition tillage planter seed quality through the establishment of the vibration characteristics of the mathematical model.

Gas Suction Turnip Seed Suction Nozzle Design and Experimental Research

The gas suction turnip seed metering device is the core requirement of precise seeding, in this article, through analysis and research of the geometric parameters of radish seeds, affect the seed is obtained by means of experiment draw the related factors of seed suction nozzle, including adsorption seed when the surrounding air velocity and adsorption under a certain air needed distance, and the specific parameters of these factors were determined.