In order to study the horizontal fire spread characteristics of transformer oil, a series of experiments were carried out on the experimental platform developed, the influence of the initial temperature and the width of the oil pool on the flame propagation, including the propagation speed, flame morphology and the temperature field distribution of the gas-liquid two-phase, was analyzed to reveal the flame propagation characteristics and the oil surface temperature rise law in the process of transformer oil fire propagation, and a theoretical model of coupled liquid-phase convective heat transfer and flame radiation heat transfer was established by combining thermodynamic theory to quantitatively calculate the heat transfer process of surface flow in flame propagation process. Through the theoretical analysis and quantitative calculation of gas-liquid heat transfer, it is proved that the surface flow is mainly driven by surface tension and the flame spreads in the form of pulsation. Combined with the experimental data for verification, it is found that the proportion of liquid-phase convective heat transfer to the total heat flow is much larger than that of flame radiation to the total heat flow, which proves that liquid-phase convective heat transfer is the main mode of surface flow heat transfer.

The sea is an important renewable energy resource for its extension and the power conveyed by waves, currents, tides, and thermal gradients. Amongst these physical phenomena, sea waves are the source with the highest energy density and may contribute to fulfilling the global increase of power demand. Despite the potential of sea waves, their harnessing is still a technological challenge. Oscillating water column systems operating with Wells turbines represent one of the most straightforward and reliable solutions for the optimal exploitation of this resource. An analytical model and computational fluid dynamics models were developed to evaluate the functioning of monoplane isolated Wells turbines. For the former modeling typology, a blade element momentum code relying on the actuator disk theory was applied, considering the rotor as a set of airfoils. For the latter modeling typology, a three-dimensional multi-block technique was implemented to create the computational domain with a fully mapped mesh composed of hexahedral elements. The employment of circumferential periodic boundary conditions allowed for the reduction of computational power and time. The models use Reynolds-averaged Navier-Stokes (RANS) or u-RANS schemes with a multiple reference frame approach or the u-RANS formulation with a sliding mesh approach. The achieved results were compared with analytical and experimental literature data for validation. All the developed models showed good agreement. The analytical model is suitable for a fast prediction of the turbine operation on a wide set of configurations during the first design stages, while the computational fluid dynamics (CFD) models are indicated for the further investigation of the selected configurations.

The acoustic data in terms of compressional and shear wave velocity provide important petrophysical information about the rock. The sonic data is a significant input that is commonly used for deriving geomechanical parameters. Understanding the geomechanical properties of reservoir rock is essential during the drilling, development, production, and stimulation of an oil or gas reservoir. Among them, Young's modulus and Poisson's ratio are the most important elastic parameters. These properties are usually estimated from bulk density, compressional and shear wave velocity log data. Sonic data acquisition is usually achieved through dipole sonic imager log or laboratory testing on core samples which is costly and time-consuming. Acquiring sonic data from wireline logs is not feasible approach all the time; as the wireline log, specially shear-wave log, may not be recorded for every well. However, drilling data is available in a real-time for every well using real-time drilling sensors. The main objective of this paper is to predict sonic slowness logs in real-time based on the drilling data using artificial neural network (ANN). The data used in this study were recorded during the drilling of 12 ¼” hole sections from two wells. Many formations of different lithology were penetrated while drilling these sections of over 3000 ft vertical interval. The drilling and sonic datasets were recorded and preprocessed before using them for the ANN model. 2900 data points from the first well were used for building and testing the model. The input parameters included weight on bit (WOB), torque (T), standpipe pressure (SPP), pipe speed (PS), rate of penetration (ROP), and mud flow rate (Q). Another dataset of 2000 data points from the second well that was drilled in the same field was used to validate the model. The predictions were compared with sonic logs that were obtained after the drilling operation and the results appear to be highly promising for future applications. The sonic slowness ANN models showed a high accuracy for the model building (training and testing). Validation of these models was carried out using an unseen dataset. The results using the validation dataset for the compressional slowness model yielded a coefficient of determination (R 2 ) of 0.983 and average absolute percentage error (AAPE) of less than 1.25%. For the shear slowness model, R 2 was higher than 0.994 and AAPE less than 1.175%. The study offers empirical correlations that can be utilized to estimate the sonic slowness logs by engineers without the need to employ ANN software. The new shear slowness correlation was compared with other widely used correlations and the results showed high accuracy.

Drilling fluids for oilfield use consist of complex mixtures of natural and synthetic materials. The viscous properties along with the particle size distribution of the applied weight materials are vital in controlling the stability of the microstructure and density of the drilling fluid. Typical oil-based drilling fluids made for North Sea oilfield drilling application with oil–water ratios (OWRs) of 80/20 and 60/40 are examined with respect to their density stability. The stability was analyzed at both rest and dynamic conditions using flow and viscosity tests, oscillatory sweep tests, creep tests, and time-dependent oscillatory sweep tests using a scientific rheometer with a measuring system applying a grooved bob at atmospheric conditions. The quantities used in ranking the stability of the fluids include the yield stress, flow transition index, mechanical storage stability index, and dynamic sag index. We observed that the drilling fluid sample with OWR = 60/40 showed a more stable dispersion with a stronger structure having higher yield stress and flow transition index values, while the mechanical storage stability index and dynamic sag index recorded lower values. Furthermore, the Herschel–Bulkley parameters for yield stress and consistency index increased in fluid with OWR = 60/40, whereas the flow index values for both fluid samples were similar. The results of this study enable drilling fluid engineers to design realistic oil-based drilling fluids with stable microstructure to mitigate weigh material settling and sag of particles for North Sea drilling operation.

Due to the increase in the greenhouse effect, lowering emissions is becoming a certain issue all over the world. It is a concern to develop alternative options to minimize the spread of exhaust gases. For this purpose, in this study, the plug flow reactor in the system consisting of solid oxide fuel cell, reactor, electric motor, battery, burner, and the heat exchanger is considered. Numerical modeling of hydrogen gas generation in a plug flow reactor is studied. The reactor indicated on-board hydrogen gas generation for an electric motor automobile has not been modeled in the literature yet. Autothermal reforming of isooctane is simulated in the comsol multiphysics software program in the reactor particularly. Conversion of isooctane and H 2 O is examined at different overall heat transfer coefficients, input temperatures, and steam/carbon ratios. Also, there are certain differences between adiabatic and non-adiabatic conditions. The produced synthesis gas of hydrogen drastically increases in the non-adiabatic case. The obtained results from the model are compared with experimental data obtained from the literature. H 2 production at the end of the autothermal reforming process indicates that the power provided from the reactor can operate a motor of an automobile. In this study, the achieved power is 65.8 kW (88 HP) and is sufficient for an automobile. Simulation results show that the reactor volume of 75 L supplies 0.18 mol −1 of H 2 and 0.08 mol −1 of CO in the non-adiabatic case.

The viscosity of extra-heavy oils including bitumen can be reduced significantly by adding solvent such as toluene to enhance extraction, production, and transportation. Thus, prediction of viscosity and/or rheology of bitumen-solvent mixtures has become necessary. More so, selecting a suitable rheological model for simulation of flow in porous media has an important role to play in engineering design of production and processing systems. While several mixing rules have been applied to calculate the viscosity of bitumen-solvent mixtures, rheological model to describe the flow characteristics has rarely been published. Thus, in this investigation, rheological behavior of bitumen and bitumen-toluene mixtures (weight fractions of bitumen WB = 0, 0.25, 0.5, 0.6, 0.75, and 1 w/w) have been studied at the flow temperature (75 °C) of the bitumen and in the range of shear rates between 0.001 and 1000 s −1 . The data were fitted using different rheological models including the Power law, Cross model, Carreau–Yasuda model, and the newly introduced ones herein named as Cross-Logistic and Logistic models. Then, a computational fluid dynamics (CFD) model was built using a scanning electron microscope (SEM) image of rock sample (representing a realistic porous geometry) to simulate pore scale flow characteristics. The observations revealed that the original bitumen exhibits a Newtonian behavior within the low shear rate region (0.001–10 s −1 ) and shows a non-Newtonian (pseudoplastic) behavior at the higher shear rate region (100–1000 s −1 ). Conversely, the bitumen-toluene mixtures show shear thinning (pseudoplastic) behavior at low shear rate region (0.001–0.01), which appears to become less significant within 0.01 to 0.1 s −1 , and exhibit shear independent Newtonian behavior within 0.1 and 1000 s −1 shear rates. Moreover, except for the original bitumen, statistical error analysis of prediction ability of the tested rheological models as well as the results from the pore scale flow parameters suggested that the Power law might not be suitable for predicting the flow characteristics of the bitumen–toluene mixtures compared to the other models.

The study presents the investigation on heat transfer distribution along a gas turbine blade internal cooling channel. Six different cases were considered in this study, using the smooth surface channel as a baseline. Three different dimples depth-to-diameter ratios with 0.1, 0.25, and 0.50 were considered. Different combinations of partial spherical and leaf dimples were also studied with the Reynolds numbers of 6,000, 20,000, 30,000, 40,000, and 50,000. In addition to the experimental investigation, the numerical study was conducted using a large eddy simulation (LES) to validate the data. It was found that the highest depth-to-diameter ratio showed the highest heat transfer rate. However, the deepest dimpled channel shows the highest pressure drop, which affects the overall thermal performance of the cooling channel. The results showed that the leaf dimpled surface is the best cooling channel based on the highest Reynolds number's heat transfer enhancement and friction factor. However, at the lowest Reynolds number, partial spherical dimples with a 0.25 depth-to-diameter ratio showed the highest thermal performance.

Examining the effects of design variables on performance and emission parameters for gas turbine engines is of high importance. In this study, the effects of by-pass ratio (BPR) and turbine inlet temperature (TIT) of turbofan engine on energy, exergy, and exhaust emissions are parametrically analyzed at 0.85 Ma and altitude of 11 km. Moreover, cruise NOx emission is quantified by Boeing Fuel Flow Method 2 (BFFM2) and DLR methods. As a novelty, specific NOx production (SNP) is first quantified for PW4000 engine. In this study, parametric cycle equations regarding turbofan engine are encoded so as to compute performance and emission metrics. According to energy analysis, specific fuel consumption (SFC) of the turbofan averagely changed from 19.82 to 18.64 g/kNs due to rising BPR whereas it increases from 18.62 to 19.93 g/kNs owing to rising TIT. Furthermore, exergy efficiency of turbofan rises from 27.67% to 29.42% due to rising BPR whereas it decreases from 29.46% to 27.65% owing to rising TIT. As for NOx emission results, the higher BPR leads to the lowering of the SNP index of the turbofan from 0.46 to 0.375 g/kNs while the higher TIT yields to the increase of the SNP index from 0.377 to 0.455 g/kNs. According to the findings of this study, the decision mechanism could be improved to find out optimum design variables in terms of eco-friendly aircraft activities.

Internal motion and dynamics mechanism studies of a new composite percussion drilling tool aim at reducing stick-slip phenomenon and improving rock breaking efficiency. In this study, experiments are performed using composite percussion drilling tools to investigate its torsional and axial composite impact performance. According to the experimental results, a six degrees-of-freedom (6DOF) rigid body motion model was established to study the passive motion of a torsional hammer. The obtained results, including the tangential acceleration, were verified with experimental data, and the small pressure differences between the high and low pressure areas, which mainly determined by the inlet structure, is the main reason for the poor torsional impact effects. Based on these discoveries, the improved design increases the inlet flow to 17.2% of the total, the pressure differences to 0.05 MPa, and the instantaneous tangential acceleration to 0.198 m/s 2 , which results in increased tangential acceleration fluctuation amplitude by 1137.5% and greatly improved torsional impact performance. This research can provide a baseline for stick-slip reduction technology optimization.

Extended reach drilling (ERD) wells with a horizontal and highly deviated section are widely applied in the oil and gas industry because they provide higher drainage area than vertical wells and hence increase the productivity or injectivity of the well. Among many issues encountered in a complex well trajectory, poor hole cleaning is the most common problem, which occurs mainly in the deviated and horizontal section of oil and gas wells. There are significant parameters that have a serious impact on hole cleaning performance in high-angle and horizontal sections. These include flowrate, rheology, and density of the drilling fluid, drill string eccentricity, pipe rotation, and cuttings size. It has been recognized that the action of most of these parameters to transport drilled cuttings is constantly a point of controversy among oilfield engineers. In the present study, extensive experiments were conducted in an advanced purpose-built flow rig to identify the main parameters affecting on circulate the cuttings out of the test section in a horizontal position. The flow-loop simulator has been designed to allow easy variation of operational parameters in terms of flowrate, mud density, drill string eccentricity, pipe rotation, and cuttings size. In addition, the study covers the impacts of laminar, transition, and turbulent flow regimes. The goal of such variation in the operational conditions is to simulate real-field situations. The results have shown that drill string rotation and flowrate were the operational parameters with the highest positive influence on the cuttings transports process. In contrast, drill pipe eccentricity has a negative influence on cuttings removal efficiency. The cuttings transportation performance is further improved by pipe rotation at different levels of eccentricity, especially at fully eccentric annuli. It was also shown that larger cuttings appeared to be easier to remove in a horizontal annulus than smaller ones. The experimental results would provide a more in-depth understanding of the relationship between drilling operation parameters and hole cleaning efficiency in ERD operations. This will help the drilling teams to realize what action is better to take for efficient cutting transportation.

The research work depicts the study of the comparison of a 1 kW fixed pitch vertical-axis wind turbine (VAWT) and a variable pitch VAWT via analytical, numerical, and experimental results. Being an emerging technology, wind turbine is becoming a source of attraction for the researchers. The VAWT in comparison to the horizontal-axis wind turbine (HAWT) has shown numerous benefits. The fundamental purpose of this study is to maximize the output power and output torque of the wind turbine. For achieving an improved output, a novel and unique mechanism, termed as pitching mechanism, is employed that follows the variable pitch concept. The mathematical modeling was performed for the straight blade variable pitch VAWT and for the fixed rotor. The four-bar mechanism was developed to execute the variable pitch mechanism and implemented in the form of the computer-aided design, model. A scaled down three-dimensional (3D) model of the rotor was manufactured using the 3D printing technique. The aerodynamic forces such as lift and drag were measured upon the rotor as per the testing on the rotor in the wind tunnel. Computational fluid dynamics (CFD) simulations were run for the fixed pitch and the variable pitch rotor. The transient analysis was performed for the azimuthal angle ranging from 0 to 360 deg and for a pitch angle varying from +25 to −25 deg in ansys software. The comparative study was undertaken, keeping in view the analytical, simulation, and experimental results. A worthy agreement was observed among analytical, software, and experimental results, and a promising increase in power and torque was observed due to the introduction of the variable pitch mechanism. The power produced by the variable pitch design showed a significant increase in the power production compared to the fixed pitch design. The numerical and experimental values of c p for the variable pitch design were quite comparable.

In this study, the internal cooling channel was investigated without any bend. Smooth surfaces and dimpled surfaces were investigated using the different combinations of connecting circular and rectangular holes. The computations were performed using the large eddy simulation (LES) model for Reynolds (Re) numbers from 10,000 to 50,000. A total of six different connecting holes were investigated with a smooth and dimpled surface. A partial spherical dimple with two circular holes showed the highest heat transfer, but it has a higher pressure loss penalty. Even though the leaf dimpled surface with the rectangluar holes indicated a little low heat transfer, it represents the highest efficiency at higher Reynolds numbers because of the low-pressure drops.

Photovoltaic (PV) power generation can help reduce households’ electricity from the power grid and thus reduce electricity bills. However, due to the intermittence and time-varying nature of PV power generation, part of the clean energy will be wasted. Especially in some places where PV power is allowed to be sold to the power grid, the PV power that exceeds the feed-in limit will be curtailed to reduce the pressure on the infrastructure of the power grid. Battery energy storage systems (BESSs) as energy buffers have attracted increasing attention to help improve the penetration of PV power to households. This paper presents an adaptive energy management method to minimize the energy cost of residential PV-battery systems. First, the uncertainty of the predictive electricity demand and PV power supply is modeled. Then a stochastic model predictive control (SMPC) strategy is used to determine the optimal power flow of the system. Due to the deviation between the predictive input values and the actual ones, the power flow from SMPC is adjusted based on the improved correction strategy (ICS) proposed in this paper. By comparing with the other two methods (one considers the uncertainty and the other does not), the proposed method can increase the economic benefits of the system by 18% and 63%, respectively. The wasted PV power that exceeds the feed-in limit can also be reduced by 24% and 31%. This verifies the effectiveness of the proposed method to improve the system's economic benefits and self-consumption of clean energy.

This work experimentally investigates the effects of elevated combustor pressures on the characteristics of a lean premixed reacting methane/air jet injected into a lean vitiated crossflow using a 12.7 mm axial jet. Experiments were conducted in an axially staged combustor, which implements a reacting jet in crossflow (RJIC) configuration and operates over a pressure range of 1−5 atmospheres. Simultaneous CH* chemiluminescence and particle image velocimetry (PIV) are used to study the flow field and flame behavior. The results show that the reacting jet trajectory exhibits greater penetration with elevated pressure, which is a novel finding compared to available data in the literature. However, the flame liftoff point and ignition delay time both decreased with elevated pressure, which was attributed to decreased vorticity along the flame boundary which corresponds to increased Damköhler numbers (Da). Emissions measurements confirm the NO x increase with pressure as reported in the literature for single-stage gas turbine combustors. Concurrently, emission measurements for the staged configuration show the strong NO x benefit of the RJIC system: the data prove a reduction of global outlet emission levels at elevated pressure with the axially staged configuration. The axial emission reduction was attributed to the decreasing liftoff at elevated pressure levels. Hence, the research emphasizes that the flame and emission characteristics are coupled; they are not only dependent on the geometric parameters and momentum flux ratios but are also a function of pressure.

Fracture-cavity carbonate reservoirs are noncontinuous and highly heterogeneous with the present of large-scale fractures, cavities, and erosion pores. The multiscale and diversity of medium in reservoirs have a noticeable influence on the transient pressure analysis. In the typical curve matching, the connection between large-scale fractures and cavities must be considered. Unfortunately, the current well-testing model cannot be used to analyze the date of fracture-cavity carbonate reservoirs. The aim of this study is to develop an efficient well-testing model to obtain parameters and number of large-scale fractures and cavities. To solve the aforementioned problem, a pressure-transient analysis model for fracture-cavity carbonate reservoir with radial composite reservoir, multiscale fractures–caves in series connection, and dual-porosity medium (fracture and erosion pore) is established in this study. Laplace transformation is used to solve the mathematical model. The linear flow in the main fractures and the radial flow of caves drainage area are solved by coupling. The pressure-transient curves of the bottom hole have been obtained with the numerical inversion algorithms. The typical curves for the well-testing model are drawn. Nine flow stages and variation characteristics of typical curves are analyzed. The sensitivity analyses for different parameters are carried out. From the calculations, with the increasing in the length of large-scale fractures, the duration of linear flow is increased. While the radius of cave is the bigger, the convex and concave are the larger. Therefore, the location and the size of caves and large-scale fractures can be analyzed. As a field example, actual test data are analyzed by the established model. An efficient well-testing model is developed, and it can be used to interpret the actual pressure data for fracture-cavity carbonate reservoirs.

The drag-based vertical-axis Savonius wind rotor is a potential candidate for harvesting renewable energy. It is very simple in design and can be deployed as an off-grid electricity system in remote locations having no access to electricity. The present work aims to develop a novel blade profile for the Savonius rotor in order to improve its performance. In that connection, an arc-elliptical-blade profile has been developed and rotor performance has been assessed through wind tunnel testing at three different Reynolds numbers (Re = 87,039, 107,348, and 131,066). Further, its performance is compared to that of a conventional semicircular-bladed rotor under identical test conditions. The experiments revealed the maximum power coefficient (C Pmax ) of 0.11, 0.162, 0.213 at Re = 87,039, 107,348, and 131,066, respectively, for the arc-elliptical-bladed rotor. To complement the experimental findings and to examine the flow behavior around the rotor blades, the computational fluid dynamics (CFD) simulations have also been performed using ansys fluent software. The local torque is found to be greater around the advancing arc-elliptical blade than around the advancing semicircular blade. It has also been noticed that the pressure distributions over concave sides are similar regardless of the blade shape.

In recent decades, increasing attention has been paid on accurate modeling of circulating fluidized bed (CFB) risers to provide valuable guidance to design, optimization, and operation of reactors. Turbulence model plays an important role in the accurate prediction of complex gas-solid flows. Recently developed Wray–Agarwal (WA) model is a one-equation turbulence model with the advantages of high computational efficiency and competitive accuracy with two-equation models. In this paper for the first time, the Eulerian–Eulerian approach coupled with different turbulence models including WA model, standard κ–ɛ model, and shear stress transport (SST) κ–ω model is employed to simulate two-phase flows of gas phase and solid phase in two CFB risers, in order to assess accuracy and efficiency of WA model compared to other well-known two-equation models. Predicted gas-solid flow dynamic characteristics including the gas-solid volume fraction distributions in radial and axial directions, pressure profiles, and solid mass flux distributions are compared with data obtained from an experiment in detail. The results demonstrate that the WA model is very promising for accurate and efficient simulation of gas-solid multiphase flows.

It is well-known that Poiseuille number (Po, hitherto viewed mainly as a fluid mechanics parameter) decreases along a hydrodynamically developing flow, from infinity at inlet to a fixed value downstream. This study reveals that the dimensionless entropy generation rate per unit length due to fluid friction ( S ˙ ¯ ′ g e n , f r ) varies exactly the same way; hence, Po and S ˙ ¯ g e n , f r ′ are jointly studied for their dependence. Laminar hydrodynamic development of isothermal flow of incompressible fluid (water) in a circular micro-tube (diameter, D) is examined. Results are obtained for a given flow velocity for different D, and then, numerical experiments are conducted for different flow velocities for the same D-values. Striking similarity in trends of Po and S ˙ ¯ g e n , f r ′ shows a unique linear relation between them for the hydrodynamically developing region. It is theoretically shown that Po is a direct measure of entropy generation due to fluid friction, which explains its numerically obtained linear relation with S ˙ ¯ g e n , f r ′ . It is found that in hydrodynamically developing region, both Po and S ˙ ¯ g e n , f r ′ , decrease with decreasing D, which is the identified micro-effect.

Reverse circulation gas drilling has been considered to solve engineering problems such as formation water influx, wellbore instability, and excess gas requirement in gas drilling. The performance of reverse circulation gas drilling depends to a large extent on the structure design of the drill bit. An analytical model and a numerical model were developed in this study to simulate the asymmetric converging flow of gas under the drill bit for reverse circulation gas drilling. The two models were compared and applied to the evaluation of a drill bit structure design for bottom hole cleaning capacity of gas flow. It was found that the pressure, velocity, and specific kinetic energy given by the analytical model are slightly lower than that given by the numerical model. The relative difference between the gas flowrates given by the analytical model and the numerical model is less than 5%. For the drill bit structure design considered in this study, the gas flow energy between the short blades is much higher than that between the long blades. A gas injection rate of 10 m 3 /min (360 ft 3 /min) is expected to clean the drill cuttings between the short blades, while a gas flowrate of 28 m 3 /min (990 ft 3 /min) is required to clean the drill cuttings between the long blades. Although the numerical model gives more accurate result than the analytical model in predicting hydraulics parameters, the analytical model is recommended for evaluating drill bit structure design because of its simplicity and conservativeness.

Twisted Darrieus water turbine is receiving growing attention for small-scale hydropower generation. Accordingly, the need for raised water energy conversion incentivizes researchers to focus on the blade shape optimization of twisted Darrieus turbine. In view of this, experimental analysis has been performed to appraise the efficiency of a spiral Darrieus water rotor in the present work. To better the performance parameters of the studied water rotor with twisted blades, three novel blade shapes, namely U-shaped blade, V-shaped blade, and W-shaped blade, have been numerically tested using a computational fluid dynamics three-dimensional numerical model. The maximum power coefficient of the Darrieus rotor reaches 0.17 at a 0.63 tip-speed ratio using twisted blades. Using V-shaped blades, the maximum power coefficient has risen to 0.185. The current study could be practically applied to provide more effective employment of twisted Darrieus turbines and to improve the generated power from flowing water such as river streams, tidal currents, or other man-made water canals.