Comprehensive Review of Pump as Turbine

The turbine is a heart of power generation in a hydro-electric power system. A variety of different turbines are available for the purpose. The common types of Hydraulic turbines are; Pelton, cross flow, Francis, Kaplan, and propeller turbine.  However, using conventional turbines for low head and flow rate (i.e. micro hydropower) applications is not economically feasible. A low-cost alternative is to use pump as turbine. In this paper, collect and review existing Pear reviewed articles from (Scopus, google scholar, umbrella, etc.) that are directly related to pump running as a turbine from the year (2014 to 2019). Theoretical, numerical, and experimental investigations are considered. Performance improvement techniques for PAT are summarized and research gaps in related works are identified.</p

Towards Full Predictions of the Unsteady Incompressible Flow in Rotating Machines, Using OpenFOAM

The main objective of the present work is to validate methodologies for accurate numerical predictions of the incompressible flow of water in the U9 Kaplan turbine model. The term “prediction” implies that the use of detailed experimental data for boundary conditions should be avoided, and that all important features of the studied case should be included. That includes specifying boundary conditions at locations where the flow conditions can be easily estimated, and where reasonable variations in those estimations do not significantly affect the flow prediction. As an example, the U9 Kaplan turbine model has a sharply bent inlet pipe, and it is here argued that the secondary flow from that should be taken into account by including the pipe in the simulation. In the case of rotating machines, such as the U9 Kaplan turbine model, the interaction between rotating and stationary components (rotor-stator interaction) is a feature that must be included in the simulations. Three highly relevant well-documented cases have been used in the present work, the ERCOFTAC Centrifugal Pump, the Timisoara Swirl Generator and the U9 Kaplan turbine model. All three cases include rotor-stator interaction. The latter, being the main goal of the studies, has just recently been studied experimentally and is a computationally demanding case. Thus, the former two cases were used while validating the new implementations and evaluating the numerical settings, until the results were reliable and efficient. Two rotor-stator interaction methods were investigated, the steady-state frozen-rotor approach, and the unsteady sliding grid approach, and the results from four turbulence models were compared. The results show that both approaches can be used to couple the rotating and stationary parts of the domain. However, the frozen rotor yields an unphysical advection of the runner wakes, and such results should only be used for a first estimation or as initial conditions for full unsteady sliding grid simulations. The predictions compare very well with the experimental results, and the main differences can be explained by the geometrical simplifications that were made. The four turbulence models behave similarly, with a minor preference for different models in the different cases. The present work is done using the OpenFOAM OpenSource CFD toolbox. The code is chosen to facilitate an OpenSource distribution of the developments, to be shared in the scientific community, and to be directly useful in industry. It was not possible to achieve the results presented here with OpenFOAM before the start of the present work, which has significantly contributed to the validation of, and trust in, the new implementations

PREDICTION ON METER FACTOR OF THE TURBINE FLOW METER WITH UNSTEADY NUMERICAL SIMULATION

ABSTRACT The turbine flow meter is widely used in the flow rate measuring for its high accuracy and good repeatability. The flow rate will be calculated based on its meter factor, which is the most important factor of the turbine flow meter. The meter factor means pulses or revolution of the impeller per unit volume, and it can only be got from the calibration experiment. At the given flow rate, the driving torque on the impeller is equal to the drag torque, as many paper have pointed out. Based on the torque balancing equations, unsteady numerical simulation is carried out with RNG turbulence model and UDFs (User Defined Functions) in Fluent Code. The meter factor under different flow rate is calculated with the unsteady simulation. The prediction results based on the numerical simulation showed the same trends as the calibration experiment. At the most flow rate, the meter factor keeps constant, but at the lower flow rate, the meter factor higher than the constant. Because of neglecting the bearing friction drag in the process, the meter factor by numerical simulation is larger than experimen

Mathematical Modelling of Energy Systems and Fluid Machinery

The ongoing digitalization of the energy sector, which will make a large amount of data available, should not be viewed as a passive ICT application for energy technology or a threat to thermodynamics and fluid dynamics, in the light of the competition triggered by data mining and machine learning techniques. These new technologies must be posed on solid bases for the representation of energy systems and fluid machinery. Therefore, mathematical modelling is still relevant and its importance cannot be underestimated. The aim of this Special Issue was to collect contributions about mathematical modelling of energy systems and fluid machinery in order to build and consolidate the base of this knowledge

Analysis of the flow through a Francis\u27 turbine runner using computational fluid dynamics

This study investigates the fluid flow through the runner of an exceptionally low specific speed Francis’ turbine using computational fluid dynamics (CFD) to predict some performance characteristic of the runner, and to determine the effect of cavitation on the flow features within the turbine. It employs FLUENT CFD codes for the analysis. The study was carried out under steady conditions in two- dimensional analysis, primarily using the RNG k-ε turbulence model. It is mainly on single phase analysis; however a single case of two-phase cavitation modeling was performed in order to evaluate cavitation effects. The hydraulic losses were much dependent on the inlet flow velocity and less dependent on the rotational speed. Cavitation occurred throughout the flow domain and this led to non-physical negative pressure predictions for the single phase analysis. For a fixed discharge, cavitation had significant effect on the prediction of the torque and hence the runner efficiency obtained from the CFD analysis. It causes a significant reduction of the runner efficiency by increasing the hydraulic losses and should be considered in the analysis of the flow features within a runner which is likely to experiences cavitation in order to overcome some of the shortcomings of the single phase predictions

Numerical Design of a Guide Vane for an Axial Fan

This study presents a custom guide vane design to substantially reduce the waste energy in axial fans. Ideally, there is no velocity component in the radial direction in axial fans, but in practice, the air leaving the axial fan has a large tangential component of velocity which produces a large amount of swirl kinetic energy. In order to solve this problem, a guide vane is designed to remove the rotational component of the air. The methodology described in this project is based on the fundamental governing continuity, momentum, and energy equations using the Finite Volume Method (FVM). In this project, the standard k-ω model is used for turbulent modeling. Two dimensional (2D) geometry of blades and airflow cross-section are designed using AutoCAD and CATIA while GAMBIT is employed to generate a suitable mesh for the three dimensional (3D) model. The mesh independence test is done to analyze the performance. The axial fan is simulated using FLUENT software to prove an increase in airflow rate after using the guide vane. Considering the final results, it can be observed that the airflow is increased up to 6.3%

Effect of Geometric Configuration of the Impeller on the Performance of Liquivac Pump: Single Phase Flow (Water)

Liquivac pumps, with their unique shaped twin start helical rotor, have found utility in various sectors but the major drawback limiting in their global exploitation is their low performance. This paper investigates the study of performance of the Liquivac pump produced by Tomlinson Hall Ltd. Experimental data was used to validate a numerical model developed in Ansys Fluent 20.2 for the Liquivac pump. Four different geometric models of the rotor were tested numerically to find the optimum design using blade number and pitch length as the criteria to achieve improved efficiency. The choice of turbulence model is an important factor in the most accurate prediction with computational fluid dynamics (CFD) simulation. Four different turbulence models were validated with experimental measurements. The realizable K-&epsilon; model gave the most accurate performance predictions with a relative deviation of 3.8%. So, the realizable K-&epsilon; model was employed for further parametric optimization of the rotor. The results indicate a reasonable improvement in the head and efficiency of the Liquivac pump with a new rotor geometry of four equidistant blades in the front, back and four flights with 30 mm pitch. This is attributed to the most favourable balance between the different losses and most guided and uniform flow inside the rotor channels

Analysis of internal flow characteristics and entropy generation of low head bulb tubular pump

To study the internal flow characteristics and energy characteristics of a large bulb perfusion pump. Based on the CFX software of the ANSYS platform, the steady calculation of the three-dimensional model of the pump device is carried out. The numerical simulation results obtained by SST k-ω and RNG k-ε turbulence models are compared with the experimental results. Finally, SST k-ω is selected for subsequent calculation. With the help of the flow line diagram and turbulent kinetic energy table of the whole flow channel of the pump device, the flow components of the pump device under different working conditions are analyzed, and the pressure and velocity distribution at the impeller and guide vane are analyzed by pressure cloud diagram and velocity cloud diagram. It is found that there are three high-pressure areas in the impeller and guide vane section, and the high-pressure regions are mainly distributed in the middle of the impeller channel. As the head decreases, the pressure at the impeller and guide vane positions decreases gradually, and the flow rate increases. Based on the entropy production principle, the wall entropy production and the distribution of mainstream entropy production at the impeller and guide vane parts are analyzed

Small-Scale Hydropower and Energy Recovery Interventions: Management, Optimization Processes and Hydraulic Machines Applications

Several topics in the small-scale hydropower sector are of great interest for pursuing the goal of a more sustainable relationship with the environment. The goal of this Special Issue entitled “Small-Scale Hydropower and Energy Recovery Interventions: Management, Optimization Processes and Hydraulic Machines Applications” was to collect the most important contributions from experts in this research field and to arouse interest in the scientific community towards a better understanding of what might be the main key aspects of the future hydropower sector. Indeed, the Guest Editors are confident that the Special Issue will have an important impact on the entire scientific community working in this research field that is currently facing important changes in paradigm to achieve the goal of net-zero emissions in both the energy and water sectors