CFD Modeling of Flame Jump across Air Gap between Evasé and Capture Duct for Ventilation Air Methane Abatement

The ventilation air–methane (VAM) released from underground mines is often transported into regenerative thermal oxidizer (RTO) devices and burnt into heat energy. This study numerically investigates the scenarios where explosion occurs inside the RTO and the flame and pressure waves propagate back quickly towards the VAM discharge duct. Possibilities of secondary explosion in the discharge duct, hence in the downstream underground mines, are examined. The results critically showed that when the methane concentration accumulated in the RTO reached 7.5% or above, the flame generated from the explosion jumped to the evasé of the discharge section (over a distance of 29.4 m) and could induce explosions in underground mines.

Simplified Indirect Estimation of Pump Flow Discharge: An Example from Serbia

In the absence of a flowmeter or due to its inaccuracy, the flow rate at the discharge section of the pipeline following the observed pump can be roughly estimated if the pressure can be measured instead. To use the proposed procedure two main conditions should be achieved: (1) a manometer should be installed at the discharge pipeline between the pump and the flow regulation valve, and (2) the actual curve that relates pressure and flow for the observed pump unit should be known in advance. The described example is from Serbia, but it is of interest for any water pumping station with a submersible pump (installed in wells or tanks) where a limited number of adequate places for the measuring of flow are available (if any are available at all), but where the pressure at the discharge pipe of the observed pump can be measured. This simplified method can find applicability in installations in remote rural regions where limited resources are available. The results show that the calculated values of the flow obtained by the presented method deviate greatly in relation to the measured values provided by the portable ultrasonic flowmeter, up to 60% at one of the measuring points. However, in relation to the measured values provided by the permanently installed flowmeter the discrepancy is significantly lower (0.6–6.8%).

Silting thickness analysis of regular desilting in rectangular and trapezoidal channel

Silting in river is a dynamic process, so it needs to regular desilting. At present, underwater siltation monitoring is still in its early days and based on experience. This paper puts forward the criterion of discrimination, in which the flood discharge section is decreased by 20%. It used the method of steady uniform flow in open rectangular and trapezoidal channel for calculation. The results show that reference values of dredging thickness in different section forms were determined. Siltation thicknesses of rectangular channel are linearly related to water depth. And the reduction rate of trapezoidal channel has a quadratic function relation with silting thicknesses. They were proportional to channel width and their rates trended to mitigation when the bottom width and flood depth were constant. In addition, the reference value of dredging thickness should be determined by combining with the bottom width, surface width, water depth and other actual situation.

IMPROVEMENT OF DISCHARGE SECTION LINE MEASUREMENT PROGRAM

The article considers methods of misalignment determination of constructions and equipment, and analyses methods based on the spatial section line location. It is noted that in certain conditions the use of total stations and GNSS-receivers allows to perform a section line the measurements with necessary accuracy. To carry out measurements on the overall discharge section line program the improved method is suggested. The advantage of the suggested method is that if there is no opportunity for compulsory centering of a total station on the survey control points of the section line, it suggests using an extra survey control point of dam site to increase the measurement accuracy. The extra survey control point is settled in the site with high accuracy with the help of centering device. The measurements were performed by the suggested method and the results were analyzed. It was stated that the considered method increases the accuracy of misalignment determination of the control points on the overall discharge section line program.

Discussion of Mix Proportions of Concrete for Long-Distance Pumping

Long-distance pumping of concrete (up to 2000 m, with relay pumps installed at two locations) was carried out for placing invert concrete at a caisson—the construction site of a spillway discharge section. After quantifying the required performance and determining of the mix proportions of the invert concrete that would be used in the long-distance pumping, the authors focused on thixotropy as a factor that affects the pumping load. Through laboratory tests and using AE and a high-range water reducing agent with high dispersion effect, retention and pumpability enhancing admixture were found to be effective in reducing thixotropy.

Real Ship Experimental Research on Ship Sailing Resistance in Inland Restricted Channel

Ship sailing resistance is an important index of cross section size optimization of restricted channel. Through real ship experiment with one typical ship in inland restricted III channel, the relationship between ship sailing resistance and factors such as water depth to draft ratio, discharge section area and so on is studied. And modified calculation formula of ship sailing resistance is put forward. The results show that as water depth to draft ratio decreases, or discharge section area becomes smaller, ship sailing resistance will increase significantly. By introducing two parameters: section blockage ratio and water depth to draft ratio, the Эиванков formula of ship sailing resistance calculation is modified, and the calculation accuracy which the modified formula applied in restricted channel has greatly improved.