Influence of blade leaning on hydraulic excitation and structural response of a reversible pump turbine

Blade leaning is commonly seen in the runner design of reversible pump turbines which operate under varying conditions. However, there is no certain law in determine the leaning mode and level. Considering performance, hydraulic excitation and structural response, five runners with strong rotational (RL+), rotational (RL), strong counter-rotational (CL+), counter-rotational (CL) and without (NL) blade leaning are compared under high-efficiency condition in pump mode and turbine mode. The head, efficiency, internal flow pressure pulsation and runner stress are comparatively studied. Among the five runners, CL+ runner is found has the highest efficiency as pump when RL+ runner has the highest efficiency as turbine. Pressure pulsation results show that the rotor-stator interaction region is the strongest pulsation source especially for runner and blade frequencies. In pump mode, pressure pulsation intensity decreases when blade leaning mode gradually changes from rotational to counter-rotational. In turbine mode, the NL runner has the strongest pressure pulsation intensity in runner and guide vane. Both rotational and counter-rotational leaning will reduce pressure pulsation. Velocity contours indicate that blade leaning will affect the velocity uniformity especially along rotational direction and cause stronger or weaker local hydraulic excitation. Under hydraulic excitation, RL+ runner suffers the highest equivalent stress as pump while CL runner suffers the highest equivalent stress as turbine. From rotational to counter-rotational blade leaning, the maximum stress moves on the crown from low pressure side to high pressure side. Considering hydraulic excitation and structural response, the strong counter-rotational leaning blade is found better in reversible runner design.

Computational and Experimental Study of the Effect of Solidity and Aspect Ratio of a Helical Turbine for Energy Generation in a Model Gravitational Water Vortex Power Plant

Gravitational Water Vortex power plant is a relatively new plant used to generate hydropower from low head rivers and canals. There has been an increase in research in the field of runner design and canal design for GWVPPs throughout the world. As no definite equations are formulated in case of runners used in a GWVPP, they are currently produced by hit and trial method. This research focuses on studying about the use of a pure reaction turbine, Gorlov turbine, to generate power from a GWVPP. ANSYS Fluent was used to perform computational study while the experimental study was done using helical turbine blades fabricated using a 3-D printer. The energy generated is very low compared to the impulse turbines. Both the computational and experimental study shows that when increasing the aspect ratio of the turbine but keeping the solidity same, the efficiency is increased significantly. However, the studies also show that on increasing the solidity, the efficiency seems to decrease. All the turbines used submerged to 3 different depts and all the results show that increasing the submergence increased the efficiency.

Design of Internal Flow Passage of Internal Chip Removal Drill for Suction Type Internal Chip Removal System

Aiming at the current problem that the cutting chips cannot be automatically recovered in the hole-making process of carbon fiber reinforced resin matrix composites, This article first introduces a new type of drilling chip removal technology system-suction type internal chip removal system, which can timely and effectively discharge the powdery chips generated in CFRP hole processing during cutting; Secondly, in view of the problem of the internal runner design of the internal chip removal drill used in the system, this article conducted the following research: 1) Based on cutting experiments and statistical methods, classify the chips produced in CFRP hole making, and give the chip distribution rules; 2) Secondly, on the basis of fluid mechanics, using FLUENT simulation method, on the basis of defining the center distance and center angle of the inner runner for the design of the internal chip removal drill bit, the center distance and the center angle of the inner runner are given. The influence law of the chip removal center angle and the cross-sectional shape of the internal runner on the chip removal effect of the tool internal runner; 2) Based on fluid mechanics, using FLUENT simulation method, on the basis of defining the center distance of the inner runner and the center angle of the inner runner, the center distance of the inner runner, the center angle and the cross-sectional shape of the inner runner are given to the tool The influence law of the chip removal effect of the internal runner; Finally, a suction type internal chip removal system was built, and the experimental method was used to verify the correctness of the internal runner design of the internal chip removal tool.

Rapid Numerical Estimation of Pressure Drop in Hot Runner System

To determine dimensions in the hot runner systems, given a material, it is necessary to predict the pressure drop according to them. Although modern injection molding simulators are able to evaluate such pressure drops, they are expensive and demanding to be employed as a design utility. This work develops a computer tool that can calculate a pressure drop from the sprue to the gate assuming a steady flow of a generalized Newtonian fluid. For a four drop hot runner system, the accuracy has been verified by comparing the obtained results with those by a commercial simulator. This paper presents how to utilize the proposed method in the hot runner design process.

Prediction of Runaway Characteristics of Kaplan Turbines Using CFD Analysis

In case of disconnection of generator from the network and failure of the governor, the rotational speed of the rotor rapidly increases and achieves maximum value, called the runaway speed. Prediction of the runaway speed at the stage of runner design would allow to select a runner considering this characteristic. Given in this paper is the numerical prediction of the runaway speed for a Kaplan turbine. Two approaches for numerical simulation were discussed. In the first one, the flow in the turbine flow passage was simulated using 3-D RANS equations of incompressible fluid using k-ε turbulence model. In the second approach, cavitation phenomena were taken into account using two-phase Zwart-Gerber-Belamri (ZGB) cavitation model. CFD calculations were carried out with using CADRUN flow solver. When setting the boundary conditions, the turbine head, being the difference of energies in the inlet and outlet cross-sections, is pre-set as a constant value, while the discharge and the runner torque are determined in the process of computation. The computed runaway speed is compared to that obtained in the model tests. It is shown that the numerical prediction of the runaway speed using the cavitation model achieves better matching with the experimental data.

Effects of Geometrical Parameters in Gravitational Water Vortex Turbines with Conical Basin

Gravitational Water Vortex Power Plant (GWVPP) is an appropriate means to convert kinetic energy of water to rotational mechanical energy at the very low head site. This study aims to establish a basic reference for the design of the runner for the Gravitational Water Vortex Turbine (GWVT) with a conical basin. Seven different geometrical parameters have been identified for runner design, and the effect of these parameters on the system efficiency has been studied numerically and experimentally. The effect of these parameters has been studied over the range of speed with torque. The results from performance tests of these runners suggest that runner height is the most significant parameter to be considered in the design of a turbine runner for GWVPP with a conical basin. The results show that the efficiency of GWVT has improved up to 47.85% as obtained from experiments.

Differences of Flow Patterns and Pressure Pulsations in Four Prototype Pump-Turbines during Runaway Transient Processes

Frequent working condition conversions in pumped-storage power stations often induce stability problems, especially when the operating point enters the S-shaped region, during which flow transitions and pressure fluctuations are serious. The pump-turbines with different specific speed values show different characteristics, but their differences in stability features are still not clear. In this study, four different pump-turbines were selected to simulate the runaway processes from turbine modes. The similarities and differences of flow patterns and pressure fluctuations were analyzed. For the similarities, pressure pulsations increase gradually and fluctuate suddenly once the backflows occur at the runner inlets. For the differences, the evolutions of backflows and pressure pulsations are related to specific speeds and runner shapes. Firstly, it is easier for the lower specific speed turbines to enter the reverse pump mode. Secondly, the blade lean angle influences the position where backflows occur, because it determines the pressure gradient at the runner inlets. Thirdly, the runner inlet height influences pressure pulsations in the vaneless space, because the relative range of backflow transitions will be enlarged with the decrease of specific speed. Overall, investigating the mechanisms of flow pattern transitions and pressure variations is important for runner design and transient process control.

Mathematical Modelling of the Initial Mold Filling with Utilization of an Angled Runner

The flow pattern plays a crucial role in the uphill teeming process. The non-metallic inclusion generation due to interaction with the mold flux is believed to be influenced by the flow pattern. In this study, a three-dimensional mathematical model of the filling of a gating system for 10, 20, and 30 degrees angled runners was used to predict the fluid flow characteristics. Moreover, a mathematical model with a horizontal runner was applied as a reference. The predictions indicate that the angled-runner-design decreases the hump height during the initial filling stage, which results in less entrapment of mold flux into the mold. Nevertheless, increasing the angle of runner can result in a lower hump height, while the 30 degree angled runner gives a much more stable increase of the hump height during the initial filling stage. Besides CFD calculations, some thermodynamic calculations are taken into account for the chemical reactions between liquid steel and gas. The results show that the bubble shrinks due to the fact that N and O are dissolved into steel. The present findings strongly suggest that changing the horizontal runner to an angled runner would be an effective means of reducing flow unevenness during the initial filling of ingots, if the added steel losses are deemed acceptable.