Experimental Measurement on Pebble Flow Discharge in a Hopper Silo Based on a Drainage Method

The dropping of absorption sphere from the storage vessel under accident conditions and the transportation of spent fuel elements in the reactor will both lead to the pebble flow discharging process driven by gravity in a hopper silo. Therefore, the research on the gravity-driven discharging rate of pebbles in a hopper silo has significant engineering guidance for reactor safety. In general, the idea of falling pebbles weighing to obtain the discharging rate becomes the most common experimental measurement method. However, due to the limitation of response frequency and the disturbance of pebbles falling, the resolution of experimental results is limited, and the uncertainty is introduced into the data error, which is difficult to eliminate. In this experiment, a volume measurement based on drainage method is adopted. This is a new experimental method to measure the discharge process of hopper silo. The magnetostrictive liquid level sensor is applied to measure the rise of liquid level caused by the volume of falling pebbles. Compared with the weighing method, this method has two advantages. First, the resolution of this method has a higher controllability. On the one hand, the disturbance caused by the momentum of falling pebbles will not be introduced into this method, on the other hand, the measurement accuracy is determined by the multiple controllable factors. Second, this method can obtain higher measurement frequency. the sampling frequency of liquid level sensor is 1–2 orders of magnitude higher than that of electronictong balance. Based on this new experimental method, the reliability of the method is validated by comparing the experimental results of discharge flow rate with the Beverloo’s and Nedderman’s empirical formula. Furthermore, the effect of silo outlet size on pebble discharge flow rate fluctuation have been also analyzed in this study. By use of fast Fourier transform, the fluctuation of particle discharge flow rate is separated from the discharging sampling results of liquid level sensor.

An Overview of Wellhead Burning: Fundamental Science to Burn Performance Prediction

ABSTRACT While wellhead burning has been an oil field hazard for generations, the development of capping response technologies and practices by industry experts has enabled the oil exploration community to shift its views of wellhead burning from a hazard to an oil spill response tool. This review covers some of the fundamental scientific aspects and technical issues of wellhead burning that engineers and policy makers will need to consider as this mitigation strategy is examined as a standard oil spill response tactic. For context, we examine a potential wellhead blowout scenario over a range of oil flows and examine the regimes of two-phase pipe flows, their dependence on wellbore velocities and gas-liquid ratios, and how those regimes will influence the burn efficiency with some insight from our experimental observations from two-phase spray burn testing. Among the critical findings that we present is that the worst-case discharge flow rate cannot be assumed to be the worst-case wellhead burning scenario.

EXPERIMENTAL INVESTIGATION OF ENHANCEMENT IN EFFICIENCY OF CENTRIFUGAL PUMP BY REDUCTION IN CAVITATION OF PUMP

Cavitation phenomenon is basically a process formation of bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapour pressure and it is the most challenging fluid flow abnormalities leading to detrimental effects on both the centrifugal pump discharge characteristics as well as physical characteristics. In this low pressure zones are the first victims of cavitation. Due to cavitation pitting of impeller occurs and wear of internal walls of pumps occurs due to which there is creation of vibrations and noize are there. Due to this there is bad performance of centrifugal pump is there. Firstly, description of the centrifugal pump with its various parts are described after that pump characteristics and its important parameters are presented and discussed. Passive discharge (flow rate) control methods are utilized for improvement of flow rate and mechanical and volumetric and overall efficiency of the pump. Mechanical engineers is considering an important phenomenon which is known as Cavitation due to which there is decrease in centrifugal pump performance. There is also effect on head of the pump which is getting reduced due to cavitation phenomenon. In present experimental investigation the cavitation phenomenon is studied by starting and running the pump at various discharges and cavitating conditions of the centrifugal pump. Passive discharge (flow rate) control is realized using three different impeller blade leading edge angles namely 9.5 degrees, 16.5 degrees .and 22.5 degrees for reduction in the cavitation and increase the of the centrifugal pump performance at different applications namely, domestic, industrial applications of the centrifugal pump.

Fracture Prevention Following Offshore Well Blowouts: Selecting the Appropriate Capping Stack Shut-In Strategy

Summary Following uncontrolled discharge during loss of well control events, fracture initiation occurring during the post-blowout capping stage can lead to reservoir fluids broaching to the seafloor. A classic example is Union Oil's 1969 oil spill in Santa Barbara Channel, where fracture initiation at various locations caused thousands of gallons per hour to broach onto the ocean floor over a month before it could be controlled (Mullineaux 1970; Easton 1972). Disasters such as these could be prevented if the effects of the post-blowout loss of well control stages (uncontrolled discharge and capping) are incorporated into the shut-in procedures, and the wellbore architectures are modified accordingly. In this study, analytical models are used to simulate the loads on the wellbore during the different stages of loss of control. Capping pressure buildup during the shut-in is modeled to indicate fracture initiation points during the capping stage. Using these models, the critical capping pressure for a well is determined, and subsequent critical discharge flow rates are calculated. Fracture initiation would occur if the actual discharge flow rate is below the calculated critical discharge flow rate. A hypothetical case study using typical deepwater Gulf of Mexico (GOM) parameters is performed demonstrating the likelihood of fracture initiation during different discharge flow rates, discharge periods, and capping stack shut-in methods (single-step/“abrupt” or multistep/“incremental”). An abrupt shut-in for this case study leads to fracture initiation at approximately 8 hours after shut-in, while a five-step incremental shut-in is shown to prevent any fracture initiation during the 48 hours after the beginning of the shut-in. Reservoir depletion through longer discharge periods or higher discharge flow rates, despite the adverse environmental effect, can delay or even prevent fracture initiations during post-blowoutcapping. The ability to model these fracture failures enhances the understanding of wellbore integrity problems induced during loss of control situations and helps create workflows for predicting possible broaching scenarios during the post-blowout capping stage. Dimensionless plots are used to present fracture initiation for different cases—this is useful for drilling and wellbore integrity engineers for making contingency plans for dealing with loss of well control situations.

Investigation of the Performance of V-cut Turbines for Stirring Shear-thinning Fluids in a Cylindrical Vessel

The impeller design is the most crucial parameter to enhance the performance of stirred tanks. The cut in the impeller blade is a new technique to save the energy of impellers in mixing vessels without increasing the mixing time or reducing the product quality. In this paper, the new technique of cut is applied for a disc turbine rotating in an unbaffled cylindrical tank. Effects of the V-cut shape are highlighted. Non-Newtonian shear-thinning fluids are considered for the three flow regimes (laminar, transient, and turbulent). Effects of the number of blades on the flow patterns, pumping rate (Nq) and power consumption (Np) are explored. From the obtained results, a recirculation loop of flow is observed at the tip of each blade for impellers with less than three blades. These recirculation loops disappear with the increased number of blades. Under laminar flow conditions, the obtained results also revealed a decrease in power consumption and an increase in the discharge flow rate with the rise of Reynolds number. However, almost any changes were observed for these parameters (Np and Nq) under turbulent flow conditions.

Discharge Flow Rate for the Initiation of Jet Flow in Sky-Jump Spillways

The sky-jump spillway is an economical and effective solution to return water to a river, eventually complemented by a pre-excavated basin. However, an inappropriate design could endanger spillways and even the dam itself. For the design of a sky-jump it is necessary to evaluate the position and dimensions of the potential pre-excavated basin based on the characteristics of the water flow to be evacuated and the geometric configuration of the sky-jump. The jump of the water jet occurs when a certain flow rate is reached. This flow rate for the initiation of the jet flow determines the position of the impact area closest to the spillway. We propose a new formula for the determination of the flow rate for the initiation of the jet flow, which incorporates as a novelty the influence of the curvature of the flip bucket. A methodology for the direct determination of the flow rate for the initiation of the jet flow is also presented. The new formula and methodology, based on experimental laboratory work and numerical modeling, will support the designer to choose the energy dissipation way, in the riverbed or inside the flip bucket, for low and frequent discharge flows.

Feasibility Evaluation of Micro-Hydropower System Generation for Different Types of Sewage Treatment Plants

Small scale hydropower is among the most attractive and cost-effective sustainable energy technologies available, by harnessing electricity through moving water. Naturally, moving water can be found in rivers and also man-man conduits where there is a continuous water flow. The sewage treatment facility has continuous water flow at the effluent pipe that can generate electricity by means of small-hydropower system. However, there are no sewage treatment plants (STP) in Malaysia that reclaim the energy through the usage of water turbines. This study is conducted to evaluate the feasibility of a micro-hydropower (MHP) system at the continuous flow of effluent discharge point of domestic STP that comprises of a low head with high flow fluctuations. This work comprises of evaluation of the potential power output of MHP generator which attached to different type of STP. The work starts with selection of a five STP which have maximum current population equivalent (PE) over design PE loading ratio. Next, the effluent discharge flow rate & outfall head are collected and recorded. Finally the potential output power for all selected STPs is calculated. The highest continuous effluent discharge flow rate contributing in high potential power and will be identified as the feasible STP for the MHP system installation.

New Compound Open Channel Section with Polynomial Sides: Improving Cost and Aesthetics

Previous research on compound trapezoidal cross sections has mainly focused on improving the prediction of the discharge (flow rate) because of its inherent challenges. This paper focuses on two other important aspects: Section shape and optimal construction cost. First, the paper proposes a new compound section with third-degree polynomial sides of main channel with horizontal bottom (HB) that allows its top corners to be smooth, called herein compound polynomial section. The special cases of this versatile section include the simple polynomial section, polygonal section, trapezoidal-rectangular section, two-segment linear-side section, and parabolic bottom-trapezoidal section. The simple polynomial section, which is the bank-full part of the compound polynomial section, can further produce parabolic (with or without HB), trapezoidal, rectangular, and triangular sections. Second, an optimization model that minimizes construction cost (excavation and lining) of the compound (or simple) polynomial section is developed. The model includes discharge and physical constraints. Theoretical and empirical methods of discharge prediction were used in the model. The results show that the simple polynomial section was more economical than the popular parabolic section by up to 8.6% when the side slopes were restricted. The new polynomial-based sections not only reduced construction cost, but also improved maintenance and aesthetics. As such, the new sections should be of interest to researchers and practitioners in hydraulic engineering.