bluuebunny/crossref_metadata_2025 huggingface dataset:
What is the net PV energy production in Switzerland and how can we maximize it?
Authors: Martinez-Alcaraz P. , Serra-Coch G. , Alonso-Montolio C. , Coch H.
Published: December 2023

Maximizing solar energy production in Switzerland is key to meet energy transition goals. Understanding in detail the current situation, and the potential for expansion is important to develop effective strategies. With this study, we want to contribute to federal and academic efforts to measure solar energy by estimating the net energy produced by photovoltaic (PV) installations when considering their embodied energy. We calculated the values of all energy produced by PV installations across Switzerland from 1991-2021 and subtracted the embodied energy used to manufacture the PV panels and their mounting system. We considered four different types: freestanding, attached-complex, attached-simple and integrated, with progressively decreasing values of embodied energy for the supporting structure. The results show that in 2022, 50% of PV installations were producing net energy, which accounts for an accumulated historical value of 1.000 GWh, implying that 6% of the historical PV generation is net energy. If mounting systems were minimized, the accumulated net energy would reach 23%, showing the importance of integrating PV panels in building elements. These findings suggest that policies to support the diffusion of photovoltaic panels should also ensure long term use of existing installations and consider the mounting systems’ embodied energy for new ones.
BEM to BIM in the early design phase: A comparison between static and dynamic heating energy predictions
Authors: Stendal M F , Ferreira T , Dubois M C
Published: December 2023

Due to climate change and increasing pressures on resources, the demand for more energy-efficient buildings is increasing globally. Building information modeling (BIM) and building energy modeling (BEM) are two essential tools to make the necessary transition to net-zero energy buildings (NZEB). This article presents two case studies aiming to automate information from the BIM model to predict annual heating energy use at the early design phase (EDP) using static energy calculations. This article presents a comparison between results obtained with the static and dynamic energy calculations with the building energy simulation (BES) package IDA-ICE. The goal of the static calculations is to allow working directly in the BIM model in real time to obtain annual energy use based on building surfaces, heated floor area, heated volume, and other inputs related to the heating degree-day (HDD) method. This article shows that the static method provides results that differ by ±25% from results of the dynamic method, which is sufficiently precise at an early design phase to provide guidance to the architects, who make key decisions affecting building energy performance.
Transient exergy analysis of ejector cooling and thermoelectric generator systems using heat storage and parabolic trough collector for residential buildings
Authors: Gholizadeh Baris T , Ghiasirad H , Megdouli K , Anvari S , Stanek B , Skorek-Osikowska A , Bartela L
Published: December 2023

The large amount of energy consumption has attracted the attention to exploiting renewable energy sources, the most significant of which are solar energy applications in hot climates to meet the demands of cooling and power. The novelty of the present study lies in applying transient exergy analysis to two ejectors and two evaporators in an ejector cooling cycle. Furthermore, the study uses solar data specific to Tehran in Iran. Third, by absorbing waste heat from the hot parts of the condenser, the thermoelectric generator system provides the energy needed to run the pumping and electrical control systems, thereby creating a fully autonomous system. Thermodynamic model have been designed using EES software. The results of Sandia National Laboratory (SNL) and the National Renewable Energy Laboratory (NERL) have validated the parabolic trough solar model. The comparison with the experimental data collected by SNL during the LS-2 tests on the AZTRAK platform has shown good agreement. Weather conditions were analyzed as transients using Meteonorm software. The results show that the solar system produced the most heat in June and the least in December, with 816 kW and 262.3 kW, respectively. Additionally, production power and cooling in June are 5.9 kW and 86 kW, and in December: 2.7 kW and 28 kW. Regarding exergy destruction percentages, the solar collector has 86% and the storage tank has 6.5%.
Cascaded reinforcement learning based supply temperature control
Authors: Huang C , Seidel S , Bräunig J
Published: December 2023

In this work, a Q-learning based supply temperature control approach for a demonstrator building is proposed. The purpose is to improve the temperature behaviour inside the building and to tackle comfort problems such as overheating and undercooling which cannot be coped with by the standard heating curve. The Q-learning controller considers predicted future weather data as system states. This can be shown to be superior to Q-learning controllers without weather prediction. Furthermore, in order for the controller to capture different thermal effects of different time constants, a cascaded control structure is designed: An inner Q-learning based controller deals with thermal effects of smaller time constants. It is wrapped by an outer slower Q-learning controller which can tackle effects of larger time constants. Therewith, further improvement of comfort can be achieved.
Physics-informed machine learning framework to model buildings from incomplete information
Authors: Kuo T , Manikkan S , Bilionis I , Liu X , Karava P
Published: December 2023

This paper introduces a physics-informed machine learning framework that leverages statistical methods to seamlessly integrate diverse sources of information, enabling the automated generation of building energy models for specific target buildings. The proposed framework comprises five modules: building survey, building asset database, building information schema, multi-class classification, and physics-based energy model. To illustrate the framework’s effectiveness, we present a case study involving a building with two possible baselines. The results demonstrate that our developed framework successfully generates comprehensive building energy models even when faced with incomplete, effectively capturing baseline scenarios.
Exploring tools and indicators to support collaborative planning, design, implementation, operation, and evaluation of Positive Energy Districts
Authors: Andreucci M B , Delli Paoli M , Haase M
Published: December 2023

The study defines an integrated parametric workflow to support PED collaborative design and implementation. Through a preliminary detailed analysis, existing tools for urban building performance simulation and microclimatic analysis were identified, tested, and selected, aiming at maximising their interoperability potential and overall support to collaborative PED planning practices. Subsequently, it is illustrated how to conduct an ex-post simulation analysis of medium and long-term interventions, with specific projections of different scenarios considering climate change impacts on energy demand. The evaluation of the proposed climate-adaptive interventions takes place using tools for the optimization of systems and technical solutions at the basis of the energy surplus and decarbonization of districts and neighbourhoods. The aim of this research is twofold: i) shading light on the absence of data management, especially at the initial stages of the PED project, resulting in uncertainty and slow-down of the whole implementation process, as well as associated difficulties to trigger virtuous replicability processes towards inclusive urban energy transitions; and ii) promoting the adoption of tools and integrated climate adaptation and mitigation frameworks to support collaborative planning and evaluation of Positive Energy Districts.
Urban airflow prediction by pix2pix trained on FFD
Authors: Vecchiarelli Rebekah , Kraus Michael , Griego Danielle , Waibel Christoph
Published: December 2023

Existing computer-aided design tools render insufficient in their capacity to enable architects and engineers to efficiently evaluate alternative designs during early design phases due to their computationally expensive nature, which is especially the case for computational fluid dynamics (CFD) methods. One of the greatest bottleneck for integrating CFD analysis into early design phases is the limited potential for parametric analysis, where a number of design alternatives need to be quickly generated and evaluated. In this context, the present study investigates the use of the generative deep learning method “pix2pix”, which leverages conditional generative adversarial networks (cGANs) for image-to-image translation, for prediction of airflow characteristics in different representations. The evaluation proposes statistical metrics to judge the fitness of the approach in performing urban airflow prediction. Our study demonstrates that the proposed method to be implemented, trained and validated successfully for different representations of the flow field prediction under parametric city shapes by incorporating building height and vectorial information (either components or magnitudes) into the pix2pix image inputs. The findings of the study reveal that the vortical flow fields can be predicted with a high accuracy in space and magnitude in all model variations tested. Adding building height information to the input images also significantly improves Kullback-Leibler (KL) divergence compared to using uniform building heights as inputs. Using vectorial information in the form of decomposed u, v, w-vector fields during training enabled pix2pix to additionally generate vectorial predictions instead of magnitudes only.
Economic and environmental benefits of decentralized multi-energy systems for energy communities
Authors: Jobard Xavier , Capezzali Massimiliano , Dimri Neha , Duret Alexis , Fesefeldt Marten , Frossard Mija , Jacquot Vincent , Lasvaux Sebastien
Published: December 2023

In the context of growing interest in decentralised multi energy systems, this work aims at quantifying the benefit of optimized energy concepts for energy communities at the neighbourhood scale compared to individually optimized solution. To tackle this question a multi-objective optimization framework was developed and applied to a case study of 6 buildings consisting of 85% of residential dwellings and 15% to retail shop and food stores. Grouped buildings have decreased costs and greenhouse gases emissions (GHGE) respectively by 18% and 12% in the cost optimum compared to individual buildings. In the environmental optimum, costs have decreased by 11%, while GHGE remains in the same range. This decrease is at both optimum driven by electricity prices favourable to large consumers since exchanges on the electrical microgrid for this neighbourhood is very small. Optimal decrease of GHGE is obtained with greater use of HPs and smaller natural gas consumption. This work illustrates the interest of multi-objective approaches to identify optimal energy solutions for groups of buildings.
Developing tools for municipalities to meet carbon targets
Authors: Lari Khosro , Cant Kevin , Evins Ralph
Published: December 2023

Carbon emissions must be cut in half by 2030 to meet the Paris Agreement’s goals, and cities and municipalities are at the forefront of the fight against climate change. In 2017, the energy use of buildings directly accounted for 51% of emissions in the City of Victoria and offered the greatest opportunity for the municipal government to act. Unfortunately, at this point, many cities and municipalities lack the tools and locally relevant data to make effective policy decisions. This research aims to develop a practical framework for analyzing and comparing the carbon impact of policies enacted by municipal governments, and is specifically focused on the energy consumption, and operating and embodied carbon related to single-family dwellings (SFDs) in the City of Victoria, which contains a heterogeneous building stock with construction dates ranging between 1860 to present day. The underlying model has been developed based on statistical modeling and agent-based behavioral responses to different policy actions. The agent-based modelling approach models stock development in terms of new construction, retrofit, and replacement by simulating individual decisions at the building level. The results can be used to identify optimal efforts to minimizing barriers or bottlenecks in achieving low-carbon ambitions while understanding or addressing related aspects such as housing affordability. Municipalities can use the dashboard to identify and prioritize climate solutions that meet their stringent obligations.
Temperature flexible operation of district heating with booster heat pumps – Improving efficiency of existing networks
Authors: Adldinger S , Behringer L , Licklederer T , Zinsmeister D , Hamacher T
Published: December 2023

This paper illustrates a new approach for decarbonizing existing district heating networks by introducing Temperature Flexible District Heating Networks (TFDHs) using decentralized booster heat pumps. A rule-based control concept is presented to effectively manage the varying temperatures within the network. Based on an annual simulation, the optimal heat supply for TFDHs is determined and compared with simulated data of 3rd and 5th Generation district heating networks using the Levelized Costs Of Heat (LCOH) as a key performance indicator. The results of the calculations reveal a high decarbonization potential in transforming existing heat networks into temperature flexible heat networks, depending on the fuel source. TFDHs get economical, if the investment costs of the decentralized generation technology are reduced by 10 % and the natural gas price increases by 1 €ct/kWh.
Assessment of summer outdoor thermal comfort in an urban neighborhood with high-rise buildings
Authors: Kubilay A , Strebel D , Rubin A , Derome D , Carmeliet J
Published: December 2023

The use of urban vegetation and ventilation corridors can be beneficial in terms of outdoor thermal comfort. High-rise buildings modify urban ventilation by redirecting incident wind flow, which can further complicate local thermal conditions. The present study investigates the interaction of building morphology and urban vegetation during heat wave conditions. A coupled multiscale approach is performed that allows for a detailed analysis of the local impact of vegetation and high-rise buildings in an urban neighborhood in Zurich, Switzerland. Existing configuration in the neighborhood with low-rise buildings of mostly uniform height is modified with high-rise buildings. Mesoscale meteorological simulations are employed to drive the flow in building-resolved computational fluid dynamics (CFD) simulations at microscale. The results show significantly lower air temperature around groups of trees and along main streets aligned with the predominant wind direction. However, there are also locations where air temperature increases due to the presence of trees, especially when there is limited exchange with the main ventilation corridor. Initial simulations with high-rise buildings show that they can have a large influence on air temperature in the immediate neighborhood.
Influence of specific characteristics of subjects and environmental conditions on comfort level during showering
Authors: Albrecht K , Keuler J , Pärisch P
Published: December 2023

In systems that do not store domestic hot water (DHW), temperature fluctuations occur in the hot water temperature at the outlet when the DHW load changes. If these temperature fluctuations arrive at the tapping point, they influence the users’ perception of comfort. Especially in the shower these temperature fluctuations can lead to a loss of comfort. Unlike in the field of air conditioning, there have been relatively few studies on the perception of comfort in the shower, and these used only males as test subjects. Therefore, we started a study with 120 persons with the aim to involve a representative variety of test subjects. In our test facility a temperature profile with varying rates of change was imprinted and the test subjects provided feedback on whether they noticed temperature changes or found them uncomfortable. In this study, results on the comfort perception of the participants in the shower are examined in relation to individual factors such as gender, age or Body-Mass-Index (BMI), and the outside temperature. We cannot determine a specific impact of these factors on the comfort perception of a group of test subjects. Neither was an influence on the desired temperatures, which ranged between 33 °C and 45 °C, detected.
Impact of shade on outdoor thermal comfort, in the case of a Mediterranean Promenade
Authors: Tola A , Veleshnja J , Meunier P L , Bisha G
Published: December 2023

Outdoor thermal comfort is a frequent research topic nowadays. This research focuses on the Mediterranean coastal promenade, taking as a case study the coastal promenade of the city of Durres in Albania. The purpose of this research is to find out how and to what extent natural and artificial shades impact outdoor thermal comfort at the pedestrian’s level by including climate parameters during the analysis. The study is both quantitative and qualitative. Following an evaluation of the urban texture, thermal cameras and climatic instruments are used to conduct field measurements. Then, ENVI-met computer simulations are run with a focus on the PET index. The results of measurements and simulations of the promenade have indicated a high level of thermal stress. In the end, using computer simulation, two hypothetical scenarios are developed, taking into consideration the parameter of shade. They are set under identical climate circumstances on a common summer day. The results of the scenarios have shown that selecting the appropriate types of greenery and artificial shading improves pedestrian thermal comfort by 12-45 percent. Thus, it is very important how promenades and public spaces are designed, paying special attention to their physical elements such as natural and artificial shading.
Thermographic cameras for thermal comfort applications: simulated and experimental spectral response errors of various long-wave infrared detectors
Authors: Merchant C , Meggers F
Published: December 2023

Modern remote temperature sensing in the form of infrared imaging has become a widely used and important technique, with the ability to measure and characterize important but unseen Radiant heat. As more Long-wave Infrared (LWIR) detectors come to market aiming to meet a wide array of needs and goals, there is a need to differentiate and appraise LWIR detectors based upon the specific needs of thermal comfort research. While most detectors measure in the range of 8-14 μm, only 37.6% of the emitted energy of a blackbody at 300 K is contained in this spectral range. Thus, inherent to the operation of nearly all infrared detectors and cameras is an assumption about the emission curves of the objects sensed. Many materials in the built environment deviate significantly from the blackbody assumption, and the error due to this deviation is one which generic gray-body emissivity corrections are unable to fix — it is akin to taking black-and-white images with only the red channel of a camera, and using exposure compensation to correct the image to attempt a true monochrome rendition: there is simply missing information and the adjusted image will still be very clearly wrong. In this paper, we aim to evaluate by simulation and experiment the potential errors in infrared thermography used to drive thermal comfort heat transfer calculations due to intrinsic spectral assumptions of LWIR detectors.
Influence of the mass of energetic material and stand-off distance on the performance of perforator charges
Authors: Abd Elhady A , Riad A M , Shaker M A , Elshenawy T A
Published: December 2023

In this paper, the influence of the mass of Energetic Material (EM) and the relevant stand-off distance on the perforator charge performance has been investigated experimentally and numerically. An experimental program has been conducted, in which perforator charges have been constructed using different masses of an EM; where the relevant stand-off distances for the perforator charges have been changed accordingly. The constructed perforator charges with 33 mm in diameters are statically exploded against 1006 steel target and the depth of jet penetration for each tested perforator charge has been measured. Moreover, Autodyn-2D hydrocode is fed with the data of the constructed perforator charges to simulate their jet formation and its penetration process into 1006 steel target. The hydrocode predicts the dependence of the resultant jet velocity and its penetration depth into 1006 steel target on the mass of EM and the relevant stand-off distance. This dependence has also been confirmed by the corresponding static test results of small diameters perforator charges. Results show that the measured penetration depth increases from 11.0 to 13.7cm into 1006 steel target when the mass of EM increases from 36 to 41g and the relevant standoff distance decreases from 25.6 to 22.6 mm then; the penetration depth decreases again due to the limited standoff distance maintained for the tested perforator charges.
CFD simulation with analytical verification of discharging of nitrogen and helium from a high-pressure gas vessel
Authors: Elgezzar M , Rashad A , Hassan M S , Elnady T
Published: December 2023

Many applications and industrial processes may necessitate the storage of large amounts of gases at high pressures. These compressed gases could be extremely dangerous if unintentionally released. since they could be poisonous or combustible when mixed with air. This research seeks to create a CFD model and undertake an analytical investigation of the process of de-pressurization of high-pressure gas from a vessel. The vessel to be studied is used in a pneumatic power system used to operate the control surface of a flying vehicle. The study involved two working fluids (nitrogen and helium). The discharging process is considered as a typical mass and heat transfer problem solved analytically by adopting The First Law of Thermodynamics to an unsteady flow control volume and simulated by employing transient flow analysis to the CFD model. The research was carried out on 440 bars (absolute pressure) of pressurized gas vessels. Working gases for the study included nitrogen and helium. Analytical solution results for the two different gases have been compared with the CFD simulation results to assess the CFD model’s accuracy. A good match is achieved when the gas temperature, pressure, density, and outlet mass flow rate variations are compared. The results demonstrated a good match between the CFD and analytical data, proving the validity of the CFD model.
Experimental and numerical Investigation of entrapped air presence and expulsions in irregular pipelines on hydraulic transients
Authors: Warda H A , Wahba E M , Elamrousy S I
Published: December 2023

In the present study, the transient event of rapid opening of upstream valve in undulated water pipeline with entrapped air pockets was investigated both experimentally and numerically. Pressure peaks and oscillation patterns were traced with the variation of air pocket length, blocking column length and water filling column. A transient two-dimensional CFD simulation model was introduced and validated by laboratory experiments. The proposed CFD model was conducted using ANSYS fluent based on Reynolds-averaged Navier–Stokes (RANS) equations and the volume of fluid (VOF) method. A user-defined functions (UDF) for both water compressibility effect and opening valve estimated pattern were adopted to verify the experimental results. For further understanding of transient response air expulsion through air vents of various orifices diameters were experimentally investigated. Image processing technique by using photoshop were utilized to clarify Stages of air expulsions, air water interaction and orifice flow regime. The obtained results showed that pressure peaks and oscillations depend strongly on orifice size where small orifice caused an intermitted flow choked by water column in contrast to large orifice where water hammer was dominated. An experimental facility was constructed at Alexandria university hydraulics laboratory to fulfil the research objectives. Air presence challenges in hydraulic systems are extensively applied for water and fuel supply lines, firefighting, and drainage systems in airports ground facilities.
Effect of salinity on marine propeller performance
Authors: Ghoniem A M , Abo Elazm A S , Benaya M I , Mohamed S A
Published: December 2023

In order to analyse problems with fluid flow, computational fluid dynamics is one of the most helpful tools available. This paper presents a numerical simulation of the effect of salinity on a marine propeller of an aircraft carrier in advance of the propeller open water (POW) test. A five-bladed fixed-pitch propeller is analysed using an unstructured mesh in the flow domain (PPTC - VP1304). Solving the RANSE equations describing the flow with a streamlined solver To begin, the accuracy of the numerical model was checked by comparing the results to previously published experimental data on the propeller. The verified model was then used to investigate how salinity impacted propeller performance in open water. The effect of fluctuating salinity was investigated by adjusting the properties of the flow fluid in a computational model. Lower advance ratios are where the effect of salinity, a decrease in efficiency of up to 4%, really shows up. However, it had little to no effect at higher advance ratios.
A novel in-flight thrust modulation technique for SPRM: proof of concept
Authors: Abdelraouf A M , Mahmoud O K , Al-Sanabawy M A
Published: December 2023

Thrust modulation (termination or reduction) is one of the most sophisticated topics in rocket motors. Thrust termination is employed when combustion must be terminated to ensure proper stage separation, to avoid motor explosion, to attain certain range, or for research purposes. While liquid and hybrid propellant rocket motors have the ability to extinguish thrust, thrust termination in solid propellant rocket motors (SPRMs) need the use of specialized technology. In-flight thrust termination of (SPRMs) can be achieved by sudden and sufficient increase in throat area. Increasing throat area causes high depressurization rate which consequently leads to extinguishing the rocket motor. In contrast, in-flight thrust reduction can be theoretically attained either by reducing chamber pressure to a new equilibrium level or by reducing the divergent section length. The objective of the present paper is to prove the concept of using Linear Shaped Charge (LSC) for thrust modulation; a technique novel to SPRM applications. Thrust termination concept is proved via a set of static firing tests on a standard test motor. In addition, a mathematical model is developed to predict the drop in thrust due to cutting the nozzle at any arbitrary location. The model is validated by comparing with published experiments for thrust termination and reduction. A parametric study is conducted based on model results. It is confirmed that by cutting the nozzle along its divergent section, thrust reduction less than 20% can be attained. Further reduction can be achieved by cutting the nozzle along its convergent section.
Enhanced range-doppler algorithm for SAR image formation
Authors: Sakr M , Amein A S , Ahmed F M , Amer G M , Youssef A
Published: December 2023

A Synthetic Aperture Radar (SAR) system is a powerful source of information due to its capability to operate day and night and in all weather conditions. It is essential for military and civilian purposes. Pulse-focusing is employed by the SAR system for achieving both long-range detection and fine-range resolution. The Range-Doppler Algorithm (RDA) is the most popular pulse-focusing technique for creating images from coherent SAR data. Pulse compression techniques for SAR signal processing targets seek to improve map resolution, lower peak power, and increase the Signal-to-Noise Ratio (SNR) of the detected object. This paper demonstrates an enhanced RDA algorithm that uses a modified pulse compression technique based on mismatched filter optimization where Quadratic Constrained Quadratic Program (QCQP) is used. The performance evaluation of the proposed method is performed using visual assessment and the standard image quality metrics peak-side-lobe-ratio (PSLR), impulse-response-width (IRW), and integrated-side-lobe-ratio (ISLR). Simulated and real SAR raw data are used for performance evaluation. The experimental results demonstrate the proposed method’s robustness, efficiency, and reliability in providing a higher-quality SAR image than the traditional RDA algorithm.
Effective reduction of sidelobes in pulse compression radars using NLFM signal processing approaches
Authors: Selim M G , Mabrouk G G , Elsherif A K , Youssef A
Published: December 2023

Pulse compression techniques are widely used in modern radar systems to enhance range resolution and detection capability. As signal design is one of the basic factors of an efficient radar system, the problem of designing a radar signal with good characteristics using pulse compression is addressed in this paper. A linear frequency modulated (LFM) waveform has been widely used for conventional radars. However, it has a higher sidelobe level which makes the detection of weak targets very difficult in presence of strong targets returns and as a result the problem of masking occurs. In order to get suppressed sidelobes of radar matched filter output as well as preserve the main lobe resolution and level to overcome the problem of masking, nonlinear frequency modulated (NLFM) signals are used in modern radars. In this paper, we will introduce two different approaches to design an optimized NLFM signal which is characterized by optimized sidelobe level (SLL). The first is the exponential piecewise linear function (EPWL) which is the modification of piecewise linear (PWL) functions relying on an exponential predistortioning function. The second is the odd-term polynomial approximation (OTPA) in which the generation of NLFM signal depends only on odd-powered terms of the polynomial function. Furthermore, the simulation results of autocorrelation functions (ACF) of the proposed signals show its superiority over the traditional LFM signals and significantly enhancement compared to the recent background work. The Doppler sensitivity of the designed signals has been evaluated, revealing that the first approach offers Doppler tolerance and is suitable for surveillance radar systems, while the second approach with a lower sidelobe level is used in applications such as Synthetic Aperture Radar (SAR). Finally, the ambiguity function of the designed signals has been measured to illustrate the effect of the Doppler effect relative to different velocities.
Railway track monitoring using drones
Authors: El-Sayed M.F. , Riad H.S. , Zohny H.N. , Zahran M.S.
Published: December 2023

In recent times, the use of drones to monitor various types of transportation lines has attracted more attention. Unmanned aerial vehicles (UAVs) have a number of potential benefits over manual methods for inspecting transportation lines due to its permit scalable, quick, and affordable solutions to tasks that would otherwise be unsuitable for individuals who are subject to fatigue and measurement uncertainty. Therefore, the current study investigates the use of drones in image processing, early warning and situation assessment in the transportation sector. Due to their ability to capture aerial images in extremely high resolution at a low cost and while also covering large areas, drones are a very important source of visual data. The main goal of this work is to collect and analyse drone-shot images using MATLAB software in order to locate the line’s fault and take the necessary corrective action to prevent accidents and save lives. The results of the current work concluded that the using of aerial image processing is very effective to increase and maximize the capacities of the transportation lines. Moreover, it gives more safety for the lines. UAV can survey and take pictures of the railway line for a distance of about 8.4 km in one hour, whereas a worker would need a full day to cover the same distance (a worker scans a distance of 7 km per day), so it saved time and effort.
Numerical investigation of model Francis turbine for performance enhancement with geometrical modification
Authors: Kayastha A , Ghimire A , Bijukchhe P L , Neopane H P , Dahlhaug O G
Published: December 2023

Most of the hydropower plants in Nepal are run-of-river type and over 60% of them are operating with Francis turbines. There are huge fluctuations in flow during the dry and wet seasons, which force the power plant owner to operate the turbines at off-design conditions which can induce cavitation and fatigue loads on the turbines. This study focuses on numerical analysis of a model turbine designed for the Jhimruk hydropower plant in Nepal. A geometrical modification is made to the model turbine runner blades by attaching two pairs of vortex generators (VGs) to each blade surface on the pressure side at 0.5% span, at the leading edge. The flow on the blade breaks off and separates from the surface during the off-design conditions so VGs are introduced to mitigate swirls generated at the inlet of the turbine. VGs can help to reattach the flow and improve off-design performance of the turbine. The performance of model turbine is analyzed at different guide vane openings to simulate different operating conditions by keeping the operating head constant and varying the rotational speed of the turbine from 500 to 1500 rpm. Performance curves and hill diagrams of the turbine are generated for each case with and without VGs. The results show that VGs at off-design conditions show a maximum increment in efficiency by 12% and 1 to 5% on average. The power output is also boosted by 1 to 6 kW at off-design conditions. This objective has been achieved when compared to efficiency and power at low-discharge and high-speed regions. In conclusion, VGs are simple but effective tools to enhance the performance of hydraulic turbines as well.
Review on erosion phenomenon, maintenance, and financial calculation of lifetime as an asset for Pelton turbines
Authors: Abregu Jim , Acharya Nirmal , Solemslie Bjørn W.
Published: December 2023

Prevention of greenhouse emissions is the top priority for all countries, which urges them to switch to renewable energy as much as possible. Hydropower is one of the renewables that have high flexibility and at the same time compatibility to be used with any other renewable sources. Moreover, hydropower plants operating in the Himalayas, Andes, and Alps are facing operational challenges due to the high concentration of sediment loads in rivers. Although the arrangement of traditional sediment control mechanisms like dams and sand traps, the erosion tendency of hydro-turbine components operating in this sediment-laden water increases with the increased concentration of sediments. Much past research has been directed towards understanding sediment behaviors, investigation of flow, and effect of concentration, shape, and size, especially with Francis turbines. However, there are very fewer studies regarding sediment erosion and flow behavior in the case of the Pelton turbine. Hence, delving deeper into the flow characteristics, sediment behavior, and performance of the Pelton turbine is important to better understand the flow and sediment pattern of these types of turbines. The paper consists of the evaluation of studies conducted on the flow pattern in the Pelton turbine buckets and its validation with the numerical analysis models using image processing. It is being used in the Waterpower Laboratory at the Norwegian University of Science and Technology, NTNU. This paper also evaluates the scope of investigations about erosion by sediments in Pelton buckets using image analysis and state-of-the-art technology in the hydropower sector. In addition, a review is done about the predictability of erosion based on the measurements of the quantity of sediments that passes through the turbine. This research paper can build a background for quantifying sediment erosion in Pelton turbines with a certain degree of error, which can be utilized as a reference in future studies. The life cycle estimation of a turbine is also analyzed with the consideration of its location and financial return requirements together with the type of maintenance that it may have and the repair that is foreseen, in the case of a non-coated surface.
Numerical Simulation of Erosion in Pelton Spear Valve at Different Openings
Authors: Pandey A , Ghimire A , Bijukchhe P L , Pokharel N , Kapali A , Chitrakar S
Published: December 2023

The spear valve is one of the most eroded hydro-mechanical components of the Pelton turbine operating in sediment-laden conditions. The spear valve is used to regulate or control the flow. In a multi-nozzle system, though having the same design, the spear valves show varying erosion patterns and intensities. The only difference was found to be the openings of the nozzle/spear valve. This demonstrates that there is some sort of connection between the nozzle opening and the erosion of the spear valve. The difference in erosion intensity in different spear valves can be seen on the site but the underlying phenomenon behind the erosion needed to be studied numerically. In this research, erosion patterns were numerically investigated using an open-source CFD tool, OpenFOAM. For this simulation, the sediment particles and their properties were incorporated into the flow using the built-in Lagrangian library of the OpenFOAM. To investigate the erosion in real time, a transient simulation was undertaken for various nozzle openings. This study only focuses on the erosion at the tip of the spear valve neglecting other parts of the nozzle. This study demonstrates that the erosion in the tip of the spear valve increases with the restriction in flow.
Rotational Speed Measurement of a Shaft Using Infrared Sensor with NI Data Acquisition system and LabVIEW
Authors: Sapkota P , Pokharel N , Silwal R , Chitrakar S , Neopane H P , Thapa B
Published: December 2023

Rotational speed measurement is the process of determining the number of rotations completed in a unit time. Generally, it is measured in Hertz, radians per second and rotations per minute (RPM). Rotational speed measurement is very critical parameter in condition monitoring, speed control, and supervision of rotational equipment like generators and turbines. This paper presents an alternate method of measuring the speed of a shaft using one of the cheapest infrared sensors available in Nepalese market. The principle of measurement of speed is on the basis of reflected and absorbed infrared light which is acquired using data acquisition unit of National Instrument. The signal processing has been carried out in a LabVIEW program and speed of shaft has been verified using the other optical sensors.
Numerical study of erosion on labyrinth seals of Francis turbine
Authors: Rijal Mamata , Neopane Hari Prasad , Chitrakar Sailesh , Pandey Arun , Dev Jwala Prasad
Published: December 2023

Sediment erosion is one of the most challenging problems in hydropower plants in Nepal. The sediments like quartz erode the turbine components like runner blades, labyrinth seals and others. This study has focused on the erosion effects in different labyrinth seals of the Francis turbine. Labyrinth seals are non-contact seals used for minimizing unwanted leaks between stationary and rotating parts. The labyrinth consists of two parts: a static seal connected to the turbine covers and a rotating part connected to the runner. The labyrinth gap is small for a new turbine and so the leakage is low. The leakage grows as the gap widens due to erosion in the seals. This causes a reduction in the efficiency of the turbine. Thus, numerical analysis performed on 2-dimensional straight-through (unilateral and bilateral), stepped, and full-length labyrinth seals of Francis turbine have been covered in this research paper. The numerical models were constructed with a structured grid using ICEM. CFD simulation in OpenFOAM was carried out to understand the flow with sediment particles in different labyrinth seals. The volume eroded was evaluated using the Finnie erosion model. The pressure, velocity profile and volume eroded in labyrinth seals were investigated. The study showed stepped labyrinth seal had a maximum volume eroded on both the stator wall and rotor wall compared to other seals. Similarly, the study revealed that the rotating part of the labyrinth seal is more affected by sediment erosion than the stationary part of the seal. This is due to the high accumulation of sediment particles in the rotor wall of the labyrinth seal.
Numerical Investigation of Compatibility of Synthetic Natural Gas with Conventional Liquefied Petroleum Gas Burners
Authors: Pandey B , Ghimire R , Sapkota N , Dev A
Published: December 2023

Nepal is seeking carbon-free alternative fuels due to environmental concerns and economic issues resulting from fossil fuel usage. Carbon-neutral SNG has the potential as an alternative to LPG gas in domestic cooking, but traditional LPG equipment may not be compatible with SNG. Computational Fluid Dynamics (CFD) was used to study the compatibility of traditional LPG equipment with SNG, and it was found that essential optimization is needed to obtain optimal cooking conditions by SNG combustion. Engineering Equation Solver (EES) was used to determine the optimum inlet pressure for varying nozzle sizes. Based on the results of the study, it was determined that the optimal nozzle size for the selected type of burner is 1.15 mm. This particular nozzle size was found to provide better uniformity of flame temperature and complete combustion, resulting in an average temperature of 1700 K at a fuel inlet pressure of 2.75 kPa. This makes it a potentially better option for cooking compared to LPG, as it could potentially provide faster cooking times. The results were verified using the Python CANTERA model. A 40-50% increase in the nozzle orifice size from the traditional LPG nozzle orifice size is suggested for such conversions.
Based on Gradient Algorithm for the Inverse Source Problem of a Class of Time-space Fractional Diffusion Equations
Authors: Qin Xianru , Li Yushan
Published: December 2023

Since entering the 21st century, the establishment of fractional-order diffusion equations in various fields has been of great value and has garnered widespread attention. This study focuses on inverse source term problem for time-space fractional diffusion equation (TSFDE) using given boundary data. First, the identification source problem is transformed into a functional minimization problem utilize the Tikhonov-type regularization method. Then, the sensitivity and the adjoint problem are derived, and the gradient of functional is obtained. The conjugate gradient algorithm is used to solve the minimization problem. Finally, three xamplel with different types of source terms are used to stated the effectiveness and stability, the impact of various parameters on the numerical results is analyzed.
The Discrete Grey Power Model Based on the New Information Priority and its Application
Authors: Yang Baohua , Li Kegang , Zhao Jinshuai
Published: December 2023

How to upgrade the performance and suitability of the forecasting method and reduce the modelling error for nonlinear small sample data series has been one of the most key problems in grey system theoretical exploration. The main work of this study, a discrete grey power model is formulated that can not only simulate the development of exponential and power function systems but can also reflect the interaction between them. The new model not only ensures that the more recent information is given some priority but exhibits a lower simulation error and greater prediction accuracy. The findings indicated that the presented model minimizes the average relative error in theory, with better adaptability than previous models in simulation and prediction. The case study demonstrates that the new model is more appropriate for predicting small sample data than the previous grey power model. This research addresses limitations in existing grey models and expands the grey model system.
Positive Definiteness of the Sample Covariance Matrix of Multi-poisson Distribution
Authors: Miao Jianqun , Wu Jianq
Published: December 2023

Studying the positive definiteness of the covariance matrix of discrete samples helps to determine whether the dimensionality of the samples can be reduced, which is beneficial for optimizing the number of samples and designing optimal plans for sampling surveys. This paper aims to provide a method to determine the variable numbers of the sample subjecting to Poisson distribution. Methods. It is based on the theory of I-linear combination and its properties which are the author’s previous studying results. Results. study shows the covariance matrix of multi-Poisson distribution is positively defined and the probability of the sample covariance matrix of multi-poisson distribution is about 1 when the sample capacity is very large. Conclusion. The dimension size of the sample data matrix of multi-poisson distribution can be reduced when the sample capacity n is no more than the dimension size p.
An Improved Multi-dimensional Uncertainty Quantification Method Based on DNN-DRM
Authors: Zhao Yingge , Wang Lingyue , Li Ying , Jin Ruixia , Yang Zihan
Published: December 2023

Mathematical modeling is a method that uses mathematical methods to solve problems in real life. In the process of modeling, the inherent properties of the parameters and the change of the model design conditions will bring great uncertainty to the simulation results. In this paper, a deep neural network and dimension reduction method (DNN-DRM) is proposed to quantify the impact of parameter uncertainty on simulation results in modeling systems with multi-dimensional uncertainty, and reduce the risk caused by uncertainty. Firstly, the methods for training DNN substitute model and testing the generalization ability of models were investigated. Then the DRM based on DNN was constructed to solve the uncertain parameters in the system. In the experiments, three mathematical models with different types of complexity were modeled. Finally, the performance of the method was evaluated by probability distribution, mean and standard deviation of output values. The results show that compared with Monte Carlo simulation (MCS), the DNN-DRM can efficiently and accurately calculate the multi-dimensional uncertainty problem with a strong interaction, and effectively alleviate the “curse of dimensionality” difficulty, which provides a reference for the analysis of problems encountered in real life.
Predicting Forming Defects in Thin-walled Circular Tubes Made of A286 Based on Deform-3D
Authors: Jiang Yulian , Feng Zhiguo
Published: December 2023

We conduct a study on the thin-wall characteristics of a certain type of A286 thin-walled pipe fittings during the swaging forming process, focusing on the issues of folding and incomplete filling. In order to explore the forming mechanism of defects in thin-wall pipe fittings, the Deform-3D finite element software is utilized for numerical simulations. Through analysis of the forming results, equivalent stress, equivalent strain, material flow lines, and material flow patterns during the swaging forming process, it is found that the occurrence of defects in the thin-wall pipe fittings during the forming process is closely related to the material flow behavior. When the material flows in a positive extrusion manner during the thin-wall feature forming process, the specimen exhibits obvious folding defects. Moreover, there is significant stress concentration occurs in the transition region between the rod and the head.