Runner Design Research Articles

Instability mechanism and vibration performance of a pumped storage power station under runaway conditions

With the large-scale access of renewable energy to the grid, the load rejection of pumped storage power stations (PSPSs) has become increasingly frequent, thus increasing the possibility of runaway accidents. This study aimed to investigate the instability mechanism and vibration performance of a PSPS by considering the coupling effect of the pressurized pipe and pump-turbine under the runaway condition. First, models of the PSPS based on the elastic water-column (elastic model) and rigid water-column (rigid model) were established. Subsequently, the vibration performances of the elastic and rigid models were compared. The comparison revealed that the runaway instability characteristics of the PSPS were mainly manifested as a high-frequency and large-amplitude vibration caused by the elastic water-column, which was not observed in the rigid model. Therefore, the elasticity of the water-column, which has normally been neglected or simplified using a rigid water-column in previous studies, has a significant effect on the runaway stability. Finally, the effects of other factors on the stability and vibration performance were clarified. The runaway stability was mainly determined by the characteristics of the runaway operating point. The discharge-head relationship coefficient (S5) for quantifying the stability performance of the runaway operating point was extracted. Moreover, increasing pipe friction loss could suppress runaway instability. Additionally, the pipe water inertia only affected the runaway vibration performance but not the runaway stability result. Overall, the study findings deepen the understanding of the physical nature of runaway instability and provide guidance for pump-turbine runner design and stable operation of PSPSs.

Optimal runner design for balanced filling in a multi‐cavity mold using a two‐stage analytical approach

AbstractIn a multi‐cavity mold, parts from each cavity have consistent properties if the runner system ensures balanced melt‐front advancement. An unbalanced mold, however, narrows the processing window, complicating quality control and making it harder to maintain standards. Molds with an inherently balanced filling, such as the H‐type runner system, are preferred. However, as the number of cavities increases, improvements are needed to address the issues caused by shear heating. Additionally, the material waste in the H‐type runner system is significantly greater than in the fishbone runner system. Based on the rheological concept, a two‐stage analytical approach is established to optimize the fishbone runner system. The diameter of each runner in the fishbone runner system is optimized by controlling pressure drop and remaining time to achieve balanced filling. The impact of these factors is thoroughly examined, as well as why they must be controlled during optimization. The proposed work links the physical situation to its mathematical model, proving highly beneficial for new runner system designs, especially without commercial software assistance.Highlights A new approach to solving unbalanced filling in multi‐cavity molds. Pressure drop and remaining time are key factors for optimization. Two‐stage analytical approach ensures optimization accuracy. The optimal runner system reduces injection pressure for molding. An alternative method for designing fishbone runners without CAE assistance.

Determination of the effects of size parameters and lean angle on Bovet-based Francis turbine runner performance

Abstract In global hydropower generation, the Francis turbine is widely used because of its ability to work efficiently in a wide range of conditions like varying head and flow rates. Turbine’s meridional profile can be developed using traditional design approaches, like the Bovet method which uses empirical relations based on hydrological factors, that can be refined through optimization. Runner performance evaluation considers factors such as efficiency, erosion resistance, resistance to cavitation, and many more. Adjusting design parameters can enhance a turbine’s performance at a particular site. In this paper, a Bovet-based Francis runner design was obtained for Damile Micro Hydro located at Pharping, Nepal and the effect of variation of size parameters and lean angle on the runner performance was investigated. Initially, In-house MATLAB codes were used to design 99 meridional profile of different sizes by changing the size parameters as indicated by Bovet method and numerical simulation was performed to select the best meridional profile based on efficiency. After obtaining best meridional profile, the effect of lean angle was studied by varying it from -10° to 10°. Among the 99 designs based on different sizes, the simulation results indicate that the maximum efficiency was found to be 92.3% whereas the minimum efficiency was found to be 87.84%. The corrected lean angle of -5° showed the maximum efficiency and better pressure distribution along the blade.

Gait signatures of endurance runners with low back pain: A case controlled cross sectional study

BackgroundLow back pain (LBP) is an understudied condition among runners, and it is unclear what biomechanical features could be targeted for gait retraining to mitigate pain. Research questionHow do running biomechanics differ between healthy individuals and those with running-related LBP? MethodsThis was a case-controlled, comparative study design of community runners: running-related LBP (n=52) and healthy controls (n=52). All runners completed running history forms and performed a 3-dimensional gait analysis. Kinematic data were collected using a motion capture system and normalized to a gait cycle, while participants ran on a level grade at self-selected speed on an instrumented treadmill. Current running volume, temporal-spatial, kinetic and kinematic features were compared between groups. ResultsThe LBP group had 39.5 % lower weekly distance and 15.4 % fewer were currently training for a race (all p<.05). Runners with LBP demonstrated lower cadence (166±10 step/min vs. 171±9 step/min; p=.05), greater center of gravity lateral displacement (1.4±0.5 cm vs. 1.2 ±.3 cm; p=.044) and greater stride width variability (1.3±0.4 cm versus 1.0 ± 0.04 cm; p=.008). Runners with LBP had a greater Vertical Average Loading Rate ([VALR] 67.7±22.2 bodyweights [BW]/s vs. 62.2±21.5 BW/s; p=.022), and higher joint moments (N*m/(kg*m)) at the knee in the sagittal plane (2.13±0.50 vs. 1.87±0.56; p <.001), frontal plane (1.44±0.39 vs. 1.29±0.29; p=.013), and at the hip in the frontal plane (2.04±0.51 vs. 1.84±0.41; p=.024). No differences were found between groups in the pelvis, hip, knee, and ankle joint excursions in any plane of motion during a typical gait cycle. SignificanceThese collective motion signature may reflect challenges with control of motion and VALR in the presence of back pain. Cadence training to increase step rate, coupled with core/hip muscle activation, may be an important strategy to reduce motion variability, impact loading rate and pain symptoms while running.

The influence of the S shaped characteristics of high head pump-turbine on the minimum pressure of draft tube

Abstract The S shaped characteristics of pump-turbines have an important impact on the minimum pressure of draft tube. The quality of the S shaped characteristics is one of the key indicators to determine the success of model runner development, and this indicator is particularly important for ultra-high head pump-turbines. In order to delve deeper into the inherent relationship between the S-shaped characteristics of the runner and the optimization design and minimum pressure of draft tube, this article first defines a method for fixed-point quantitative analysis of the S shaped characteristic curve. Then, different experimental characteristic curves obtained from multiple optimized designs of the runner are used to calculate the hydraulic transition process. At the same time, the S shaped curve is quantitatively analyzed, and the relationship between the three is explored through continuous analysis. The results show that the bending degree of the equal opening lines in the middle at the S shape characteristics curves has the greatest influence on the minimum pressure at the draft tube inlet. The greater the ratio of unit flow difference to unit speed difference in the S shape characteristics curves of the equal opening line, the greater the runaway unit flow on the same equal opening line, the more favorable it is to increase the minimum pressure at the inlet of the draft tube. The optimal design of blade type and guide vane airfoil can improve the minimum pressure value of draft tube to a certain extent. The conclusions obtained in this paper can be used for reference in the research and development design of high head pump-turbine runner and the optimization calculation of transition.

Pressure Pulsation Analysis of 2D NACA66 Airfoil Based on Pulsation Tracking Network

Abstract The NACA66 airfoil is used extensively in the design of turbine runners and as a core component, the airfoil plays a vital role in the operation of the turbine. In order to investigate the details of the effect of the NACA66 airfoil on pressure pulsation, this paper investigates and analyses the NACA66 airfoil with a work angle of 14°. This study combines computational fluid dynamics (CFD) with pulsation tracking network (PTN) technology to numerically simulate the NACA66 airfoil. The simulation results show that the dominant pressure pulsation frequencies in the computational domain are mainly 100hz, 3500hz, and 6900hz, and the pressure pulsation amplitude varies for different dominant frequencies. When the dominant frequency is 100hz and 3500hz, the pressure pulsation amplitude continues to decrease from the inlet to the outlet of the calculation domain, but a small increase in pressure pulsation amplitude occurs at the trailing edge of the airfoil. When the dominant frequency is 6900hz, the pressure pulsation amplitude decreases from the inlet to the outlet of the calculation domain and increases sharply below the airfoil, which is greater than the pulsation amplitude in the surrounding area. This paper reveals the dominant frequency of the NACA66 airfoil disturbance based on PTN technology and the variation of the pressure pulsation amplitude at different dominant frequencies. The content of this study can help to explore more deeply the pressure pulsation problem generated by airfoil winding and provide ideas for solving the pressure pulsation engineering problem.

Modeling and Simulation of a Gas-Exhaust Design for Battery Thermal Runaway Propagation in a LiFePO4 Module

The release of flammable gases during battery thermal runaway poses a risk of combustion and explosion, endangering personnel safety. The convective and diffusive properties of the gas make it challenging to accurately measure gas state, complicating the assessment of the battery pack exhaust design. In this paper, a thermal resistance network model is established, which is used to calculate the battery thermal runaway propagation. Gas accumulation after thermal runaway venting of a LiFeO4 module is studied using ANSYS Fluent under different venting schemes. The results show that the scheme of battery inversion and simultaneous exhaust from the side and bottom of the module is optimal. The methods and results presented can guide the design of LiFeO4 cell pack runners.

Predicting pump-turbine characteristic curves by theoretical models based on runner geometry parameters

The characteristic curve of a pump-turbine is the essential data for calculating the hydraulic transient processes of a pumped storage power station. However, this curve is often unavailable during the preliminary design stage of pumped storage power stations. The shape of the characteristic curve directly influences the transient guarantee parameters. To date, adjusting the runner geometry to control the characteristic curve's shape for improving hydraulic transients remains a challenging issue. This paper proposes a model for predicting the characteristic curve that correlates its shape with the runner's geometric parameters. Considering the bidirectional flow in pump-turbines, two sets of governing equations are derived separately for the centripetal and centrifugal flow conditions. The governing equations for the unit discharge curve and the unit torque curve are constructed based on the energy equation and torque equation, respectively. Each term in these equations is subsequently organized into the expressions involving the runner's geometric parameters and unit parameters. To make the equations solvable, several sets of feature points are introduced. Based on the approach to obtain the feature points, an experiment/CFD (Computational Fluid Dynamics)-based prediction method and a statistics-based prediction method are proposed. Verifications using manufacturer-measured curves show that the experiment/CFD-based method is well-suited for model test acceleration and characteristic curve repair due to its higher prediction accuracy and availability, while the statistics-based method is more suitable for borrowing similar curve data during the power plant's preliminary design phase or rapidly predicting the corresponding characteristic curves during runner design. This work establishes a theoretical basis for improving hydraulic transient guarantee parameters by runner design optimization.

Advanced cooling channel structures for enhanced heat dissipation in aerospace

Thermal protection is crucial for active cooling runner structures. It’s highly effective for achieving thermal insulation in aerospace applications. This study focuses on evaluating the thermal insulation performance of the heat dissipation runner structure under varying flow rates. The results demonstrate the exceptional thermal insulation capabilities of the heat dissipation runner structure, with a noticeable positive impact on thermal protection through appropriate flow rate increments. A simulation and analysis model for thermal insulation performance is developed and validated against experimental findings. By delving into robust heat transfer theory and turbulence mechanisms, it is observed that the local turning radius and length of the runner exhibit an inverse relationship with the heat dissipation performance of the structure. Through localized optimization of the runner design and implementation of a series–parallel connection mechanism, eight distinct heat dissipation runner structures are meticulously crafted. Analysis of temperature uniformity and flow consistency within the runner structure is conducted using thermal resistance, inlet pressure loss, and comprehensive evaluation criteria. Results underscore the strong thermal insulation performance of the eight runner structures, highlighting a direct correlation between the number of parallel runners and enhanced heat dissipation efficiency, while revealing an inverse correlation with the number of local turns. Notably, at a flow rate of 0.0005 m3/s, the thermal insulation performance of the eight flow channel structures peaks. Furthermore, it is observed that increasing the series connection of the runners only serves to complicate the structural design without significant benefits to heat dissipation. Thus, it is recommended to minimize the series connection direction in the runner design to optimize thermal management effectiveness.

Francis Type Turbine Runner Design and Comparison with Model Test Results

Cavitation wear and hydraulic efficiency decrease in hydroelectric power plants have frequently been the subject of various research and studies. A hydroelectric power plant built on the Kızılırmak River in Türkiye started operating in 1960 and has not been subjected to any large-scale rehabilitation work other than general maintenance until today. The power plant has 4 Francis-type turbines, each with a power of 32 MW. Due to cavitation wear of turbine runners over the years, performance loss, vibration, and noise problems have arisen. Moreover, the maximum turbine hydraulic efficiency, which was 92% in 1960, the year the power plant was commissioned, decreased to 87.9% according to the efficiency measurements carried out at the power plant in 2020. In this study, Computational Fluid Dynamics (CFD) analyses were accomplished with Reynolds averaged Navier Stokes (RANS) calculations for the redesign of the Francis-type turbine runner and finally checked by a model test according to IEC 60193. It was observed that the model test and CFD results were close to each other, especially at the best efficiency point. The maximum turbine hydraulic efficiency, which was calculated as 94.95% as a result of CFD analysis at the nominal head, was calculated as 95.19% by the model test. The x-blade shape created in the redesigned turbine runner blades ensured homogeneous pressure distribution and increased the hydraulic efficiency significantly.

Design and optimization of runner and gating systems, in high-pressure casting and sand casting, for an aluminum alloy valve cover

The weight and speed advantage of aluminum die-casting leads to its use in many parts in the automotive industry. Casting simulation programs are used, to avoid time-consuming and expensive production costs, and to design the production process. For casting production one of the most important factors is the runner design, which directly affects castability, material selection, and casting quality. With the correct design of runner systems, there will be no problem with the casting part. In this study, the final part and the runner design for the aluminum alloy valve cover were modeled in CAD, according to the empirical calculations. Furthermore, an appropriate casting method was selected for the valve cover not only according to the results of both high-pressure die-casting and sand-casting simulations but also economic calculations. The main technical parameters for selection were mold and part temperature distribution, liquid metal flow rates, cold shut possibilities, final air quantities, microporosity, and microporosity values. After the final decision, the casting part was produced with high pressure die casting by the implementation of the final runner design.

Analysis on Hydraulic Design of Runner Blades of Francis Turbine

Francis turbine is the most widely used model in hydropower station, and the hydraulic design of runner blades affects the efficiency of the unit. This paper discusses how to complete the hydraulic design of Francis turbine runner blades according to the given parameters. In hydraulic design of Francis turbine runner, firstly, the structural scheme is determined according to the given parameters. On the basis of referring to excellent hydraulic model, a Francis turbine runner blade is designed according to the given head. By analyzing and calculating the data, the geometric parameters and axial projection of the Francis turbine runner flow channel are determined, and the axial flow network is drawn and checked, so as to complete the calculation of axial vortex line and blade drawing. Finally, the airfoil is thickened by a certain thickening principle.

INVESTIGASI EFEK SOLIDITAS RUNNER TERHADAP PERFORMA TURBIN CROSSFLOW

The crossflow turbine is a popular type of hydropower generator used to convert water energy into electricity. It offers several advantages, including a simple design, reliable performance, and suitability for low-head water flows. This study investigates the effect of runner solidity on the performance of a crossflow turbine. The designed turbine will operate at a three-meter head with a flow rate of 41.55 litters and a runner speed of 300 rpm. The runner design is straightforward, using blades made from four-inch pipes for easy availability and simple manufacturing and repair processes. Variations in runner solidity are achieved by adjusting the number of blades. The investigation uses runners with 15, 20, 25, 30, and 33 blades, representing solidities of 11.7%, 14.6%, 17.5%, and 19.2%, respectively. The results show that the runner developed from a set of blades produced by four-inch pipes, operating under the designed conditions, achieves maximum performance with an efficiency of 81.42% at a solidity of 17.5%, or 30 blades

Experimental Investigation on Effect of Hoop Thickness on Performance of Hooped Pelton Wheel

A recent improvement in Pelton runner design, the hooped runner, is based on a redistribution of behaviour among the buckets and hoops and which allows stresses to be minimized and efficiency is nearly equivalent to conventional Pelton Runner apart from low nozzle opening of 40% and 60%. This advanced design having a couple of superiority from the mechanical orientation as well as from the assembly point of view without any different difficulty from the hydraulic orientation that establishes the significance of this unique concept. In the present work, an actual laboratory-scale hooped Pelton runner is developed. The thickness of its hoop is varied as 2 mm, 3 mm and 4 mm and to prove the competence of this advanced design and the influence of hoop thickness on the hydraulic performance of the Pelton wheel, detailed experimental studies have been performed. From the results it has been concluded that the power output and efficiency of hooped Pelton runner are nearly the same as the conventional Pelton runner at all nozzle opening.

Numerical Analysis of Francis Turbine being operated in variable speed from sediment erosion perspective

Sediment erosion in hydro turbines is one of the most daunting reasons incurring huge losses to power plant owners located in the Hindu Kush Himalayan region. Repetitive repair and maintenance of runners of Francis turbines installed in such power plants have been one of the major contributor to these losses. There is no measure of how much these power plant owners have lost due to reduction in efficiency brought about by the eroded surfaces of runners. Amidst several optimizations performed in changing the runner design, this study has been conducted to study the applicability of the pre-existing designs being operated in variable speed conditions, irrespective of its practical difficulties. Numerical simulations have been performed to determine the sediment erosion of the runners at different operating conditions. In addition to the guide vane angles, and the amount of sediment injected into the system; which is parametrized as a function of the guide vane angles; rotational speed of the runner has also been varied. Complete efficiency hill diagram and sediment erosion hill diagram have been developed to analyse the efficiency and sediment erosion at several operating conditions. Finally a comparison of the variations in efficiency and sediment erosion upon operating the turbine in synchronous speed and variable speed modes have been shown. Basically, the efficiency of the turbine and sediment erosion on blade surface can be increased and decreased respectively, at off design conditions by operating the turbine in variable speed.

Parametric Study for Runner Modifications of Die Casted Part with Venting Systems

High-pressure die casting (HPDC) is a process used for creating complex components by injecting the molten metal inside the cavity at high pressure. Failure in die casting may reduce product mechanical properties, surface quality, and life cycle. In this paper, the die-casting process of an inspection instrument – test piece is investigated for parametric study and Computational fluid dynamics (CFD) analysis. Parameters used in the die-casting process are important since it affects the molten flow quality inside the cavity. Thus, a parametric study is done to investigate the optimum parameter use in the die-casting process of the test piece. Runner gating system design is also one of the important criteria to maintain the quality of products. This paper also investigated the effect of runner gating system design optimization in reducing gas porosity. The CT scan of the sample mold is included to compare the relationships between gas porosity occurrence with CFD results. This paper proposed a new runner design named outward curvature runner with an air vent that can improve velocity and temperature distributions in reducing die-casting defects. In addition to that, air vents are installed to extend the volume and promote higher suction, to eliminate gas bubbles entrapment inside the cavity.

Runner profile optimisation of gravitational vortex water turbine

&lt;span lang="EN-GB"&gt;This study discusses the numerical optimisation and performance testing of the turbine runner profile for the designed gravitational water vortex turbine. The initial design of the turbine runner is optimised using a surface vorticity algorithm coded in MATLAB to obtain the optimal stagger angle. Design validation is carried out using computational fluid dynamics (CFD) Ansys CFX to determine the performance of the turbine runner with the turbulent shear stress transport model. The CFD analysis shows that by optimising the design, the water turbine efficiency increases by about 2.6%. The prototype of the vortex turbine runner is made using a 3D printing machine with resin material. It is later tested in a laboratory-scale experiment that measures the shaft power, shaft torque and turbine efficiency in correspondence with rotational speeds varying from 150 to 650 rpm. Experiment results validate that the optimised runner has an efficiency of 45.3% or about 14% greater than the initial design runner, which has an efficiency of 39.7%.&lt;/span&gt;

The effect of runner installation and design on the performance of gravitational vortex water turbine

ABSTRACT Development in hydropower technology leads to modern and efficient technology. The emergence of gravitational vortex water turbine (GVWT) is a promising invention. It is suitable for harnessing energy from low head and flow rate water sources, ranging from approximately 0.7–2 m and 0.03–5 m3/s. A series of experimental studies had been conducted to develop the GVWT with a propeller runner. The objective of this study is to analyze the effect of runner design, including the number of blades, runner diameter and runner installation position, on the GVWT’s performance. A preliminary study on a dual-stage GVWT was carried out to increase the single-stage GVWT performance. The experimental result shows that 4-blade and 5-blade runners provide better performance than 3-blade runner and 6-blade runner. For a 5-blade runner, the optimal installation position is between 60% and 70% of depth. Installing a runner in the basin produces a blockage effect, which increase the runner performance. An extremely large blockage ratio causes stoppage which is undesirable. The maximum allowed blockage ratio is 0.8. The preliminary study on the dual-stage GVWT proves that it increases the GVWT’s performance. The efficiency of GVWT ranges from 25% − 50%.

Hydrogen-enhanced fatigue crack growth of martensitic stainless steel: A predictive model and experimental validation

Atomic hydrogen (H) diffusion in metallic structures affects the mechanical properties of steel alloys. However, the effect of hydrogen embrittlement on the fatigue crack propagation rate (FCGR) is not fully understood, and serious uncertainties can affect the design and inspection schedules of hydraulic turbine runners based on the defect-tolerance approach. The FCGR in a complex microstructure such as tempered martensitic stainless steel is governed by the H content, stress distribution, and microstructure at the crack tip. The synergetic interactions between these parameters should be kinetically studied as the crack propagates. In this study, an original model was proposed to predict the influence of H on the fatigue crack propagation rate. The model was developed specifically for tempered martensitic stainless steels containing austenite. Subsequently, it was validated through experiments performed on 415 martensitic stainless steel containing 20% of reformed austenite (RA). The material’s FCGR was tested in its raw condition, also after charging with H. Compact tension (CT) specimens were tested at two constant stress intensity factor ranges (ΔK = 8 MPa.m0.5 and 15 MPa.m0.5) and three cyclic loading frequencies (f = 35 Hz, 3.5 Hz, and 0.35 Hz). The results show a very good agreement with the predictions of the model. Moreover, both the model and the experimental results reveal that there is a critical ΔK that is dependent on the loading frequency at which the impact of H on the FCGR is maximum. Moreover, as predicted by the model, a decrease in the loading frequency led to an increase in the susceptibility of the FCGR to H.

Strategies employed in the design and optimization of pump as turbine runner

The low hydraulic efficiency of the pump as turbine (PAT) poses a major challenge to the runner design. This paper introduces a new strategy for designing and optimizing the performance of PAT runner. The strategy process is mainly divided into four steps, namely blade parametric design, significance evaluation of parameters, construction of optimizing surrogate model and optimization of improved PSO algorithm. Compared with the current design methodologies, not only does this optimization strategy propose the system design and optimization process, but also it breaks down the process into well-defined steps and simplifies them. The hydraulic efficiency of PAT optimized by this optimization strategy reaches 84.76%, which improves 3.93%. A test bench has been built to test the optimizing strategy. The maximum difference of experimental data is 1.5%, which meets the requirements of practical engineering application, and verifies the reliability of the optimization strategy process. The optimizing strategy process can be extended to apply to pump, fan, conventional turbine and other blade fluid models, and it can be further extended to apply to the optimization design of 3D blades with a high specific speed.