Gas Flow Research Articles

MPNG: A MATPOWER-Based Tool for Optimal Power and Natural Gas Flow Analyses

MPNG is an open-source simulation package for solving Optimal Power and Natural Gas Flow (OPNGF) problems. It is coded in <small>Matlab</small> and developed using the widely-used tool for power systems research and education, <small>Matpower</small>. MPNG assembles a nonlinear steady state OPNGF formulation for analyzing the integration of electricity and natural gas networks with order-of-priority classes of consumers and gas nodal price-controlled storage facilities. This paper presents the details of the nonlinear optimization model behind MPNG, as well as several features that were designed into it for the purpose of achieving robustness. These include an approximation of the Weymouth equation for handling bi-directional gas flows in pipelines, a per-unit representation for the natural gas network, and penalized slack variables for power and gas balances. Simulation results using a test case and the Colombian power and natural gas networks are presented to highlight MPNG&#x0027;s capabilities to solve OPNGF problems.

Self-Modification of Defective TiO2 under Controlled H2/Ar Gas Environment and Dynamics of Photoinduced Surface Oxygen Vacancies.

In recent years, defective TiO2 has caught considerable research attention because of its potential to overcome the limits of low visible light absorption and fast charge recombination present in pristine TiO2 photocatalysts. Among the different synthesis conditions for defective TiO2, ambient pressure hydrogenation with the addition of Ar as inert gas for safety purposes has been established as an easy method to realize the process. Whether the Ar gas might still influence the resulting photocatalytic properties and defective surface layer remains an open question. Here, we reveal that the gas flow ratio between H2 and Ar has a crucial impact on the defective structure as well as the photocatalyic activity of TiO2. In particular, transmission electron microscopy (TEM) in combination with electron energy loss spectroscopy (EELS) revealed a larger width of the defective surface layer when using a H2/Ar (50 %-50 %) gas mixture over pure H2. A possible reason could be the increase in dynamic viscosity of the gas mixture when Ar is added. Additionally, photoinduced enhanced Raman spectroscopy (PIERS) is implemented as a complementary approach to investigate the dynamics of the defective structures under ambient conditions which cannot be effortlessly realized by vacuum techniques like TEM.

Visualizing Phase Evolution of Co2C for Efficient Fischer-Tropsch to Olefins.

Cobalt carbide (Co2C) possesses high catalytic efficiency Fischer-Tropsch synthesis (FTS), while the products selectivity appears sensitive to crystallography geometry. Since the Anderson-Schulz-Flory (ASF) distribution in FTS is broken through fabricating facetted Co2C nanocrystals, yet the underlying mechanism of Co2C crystallization remains unclarified suffering from sophisticated catalyst composition involving promoter agents. Herein, the synthesis of high-purity single-crystal nanoprisms (Co2C-p) for highly efficient FTS is reported to lower olefins. Through comprehensive microstructure analysis, e.g., high-resolution TEM, in situ TEM and electron diffraction, as well as finite element simulation of gas flow field, for the first time the full roadmap of forming catalytic active cobalt carbides is disclosed, starting from reduction of Co3O4 precursor to CoO intermediate, then carburization into Co2C-s and subsequent ripening growth into Co2C-p. This gas-induced engineering of crystal phase provides a new synthesis strategy, with many new possibilities for precise design of metal-based catalyst for diverse catalytic applications.

Numerical modeling of the heat and mass transfer of rarefied gas flows in a double-sided oscillatory lid-driven cavity

In micro/nano research and engineering applications, internal flows of rarefied gas in confined geometries with moving parts are of great interest. The rarefied gaseous flows in an oscillating lid-driven cavity are investigated numerically in this work, taking into account both the parallel and antiparallel motion of the driving walls. The discrete unified gas kinetic scheme (DUGKS) is applied to the evolution of the flow and temperature fields. The Shakhov collision model is incorporated into DUGKS to account for flows of non-unit Prandtl numbers. The validity of the Shakhov-DUGKS is confirmed in both single-sided oscillating and steady lid-driven cavity flows. The effects of gas compressibility, rarefaction, and lid oscillation frequency on the mass and heat transport are then thoroughly examined. The corresponding parameter spaces of the Mach, Knudsen and Stokes numbers are 0.16 ≤ Ma ≤ 1.2, 0.075 ≤ Kn ≤ 10 and 0.5 ≤ St ≤ 5, respectively. The shear force and Nusselt number Nu on the cavity walls, as well as the velocity, temperature, and heat flux lines in the cavity, are measured and analyzed. The results suggest that the anti-Fourier heat transfer phenomenon might also occur in the rarefied double-sided oscillating cavity flow. Nu is prone to non-simple harmonic oscillation in its evolution. Furthermore, in the parallel motion as opposed to the anti-parallel motion, the left wall experiences a greater intensity of heat transmission. Compressibility, expansion cooling, and viscous heating compete to provide the complicated flow and heat transfer characteristics found in cavities.

Computational study of gas-dynamic approach for noise reduction in atwo-stroke engine’s exhaust system

BACKGROUND: The traditional approach to designing exhaust mufflers relies heavily on energy dissipation. In the "gas-dynamic" approach, the flow of exhaust gases is equalized by introducing long channel(s) into the muffler to separate impulses and shift them in time. It is assumed that such mufflers will provide noise reduction without creating significant backpressure. AIMS: To evaluate the potential of the "gas-dynamic" approach to reducing the noise level of two-stroke internal combustion engines. MATERIALS AND METHODS: The study was carried out using computational models. The processes in the gas-air tract of the piston engine were calculated using a one-dimensional (1D) model. The noise characteristic was the effective sound pressure at a specified point in the environment, calculated using 2D model of propagation of disturbances in elastic medium. The object of study was a two-stroke gasoline two-cylinder engine RMZ-551i, with a resonator (providing gas-dynamic supercharging) and a muffler. Initially, the parameters and sound pressure level of the engine with the stock muffler at full load and close to nominal engine speed were calculated. Then, the structure of the stock muffler was modified by adding a "tuned" channel between its two chambers. The parameters of the modified muffler were optimized based on the criterion of reducing gas pulsations at the outlet to the atmosphere. The noise reduction of the muffler implementing the gas-dynamic approach was evaluated relative to the stock muffler and expressed in terms of sound pressure levels in dB. Performance and levels of sound pressure were finally calculated over a wide range of engine speeds. RESULTS: According to the computational estimate, the optimal implementation of the gas-dynamic approach in the muffler reduces exhaust noise by 7 dB, while engine power decreases by 2.5%. Calculation of the sound pressure level based on the external speed characteristic showed that at an engine speed of 3000 rpm, the calculated sound pressure exceedsby 8 dB the minimum (99 dB) obtained for the optimally "tuned" muffler at an engine speed of 5000 rpm. It is suggested that the gas-dynamic approach with optimization is also applicable for uniform noise reduction over a wide range of engine speeds, with a more complex structure of the exhaustmuffler. CONCLUSIONS: Theoretical evaluation of a muffler with a tuned channel connecting its two chambers was carried out, with a two-stroke engine RMZ-551i with a stock muffler as a basis for comparison. At the optimum point on the speed characteristic, the exhaust noise was reduced by 7 dB, while the calculated power decrease was insignificant. The authorsnote the suitability of the methodology for rapid assessments and automated computational optimization of mufflers that utilize wave effects. They also point out the limitations of the models used, which require validation or rather calibration based on experimental data, and the need for the development of applied models of acoustic effects and measuring devices for domestic CAE packages.

Identification of the Structure of Liquid–Gas Flow in a Horizontal Pipeline Using the Gamma-Ray Absorption and a Convolutional Neural Network

Knowledge of the liquid–gas flow regime is important for the proper control of many industrial processes (e.g., in the mining, nuclear, petrochemical, and environmental industries). The latest publications in this field concern the use of computational intelligence methods for flow structure recognition, which include, for example, expert systems and artificial neural networks. Generally, machine learning methods exploit various characteristics of sensors signals in the value, time, frequency, and time–frequency domain. In this work, the convolutional neural network (CNN) VGG-16 is applied for analysis of histogram images of signals obtained for water–air flow by using gamma-ray absorption. The experiments were carried out on the laboratory hydraulic installation fitted with a radiometric measurement system. The essential part of the hydraulic installation is a horizontal pipeline made of metalplex, 4.5 m long, with an internal diameter of 30 mm. The radiometric measurement set used in the investigation consists of a linear Am-241 radiation source with an energy of 59.5 keV and a scintillation detector with a NaI(Tl) crystal. In this work, four types of water–air flow regimes (plug, slug, bubble, and transitional plug–bubble) were studied. MATLAB 2022a software was used to analyze the measurement signal obtained from the detector. It was found that the CNN network correctly recognizes the flow regime in more than 90% of the cases.

Investigating the vaporization mechanism's effect on interfacial tension during gas injection into an oil reservoir

AbstractIn gas injection, which is one of the fascinating enhanced oil recovery techniques, the main mechanism involves decreasing interfacial tension (IFT). Although various mechanisms can affect the IFT of a system, in most experimental and numerical studies, condensation is considered the dominant mechanism among condensation-vaporization and vaporization. Investigating the impact of each mechanism is crucial as they can influence the IFT of the system and, consequently, the effectiveness of the gas injection method. This study introduces a novel model to assess the influence of different mechanisms on system IFT. The model defines system IFT, adjusts fluid relative permeability to represent miscible, immiscible, and near-miscible states, and utilizes the Buckley–Leverett method to analyze gas fractional flow and saturation profiles when injecting carbon dioxide (CO2), methane (CH4), and nitrogen (N2). Furthermore, the research explores the impact of injection pressure and IFT at minimum miscible pressure (IFT0) on gas injection efficiency. Based on our results, for both live and dead oil, the condensation mechanism reduces IFT and near-miscible pressure; switching to a condensing-vaporizing mechanism increases these parameters. This trend was consistent across all gases studied (N2, CO2, CH4), with a more significant effect observed on the CH4-live oil system compared to N2 and CO2. Controlling the condensing mechanism in IFT measurements enhances gas flow rate and relative permeability curve within the medium. Higher injection pressure in the condensing mechanism and IFT0 = 0.5 leads to faster fluid movement and improved relative permeability due to increased driving forces. Higher IFT0 accelerates the relative permeability of fluids and gas movement within the medium by promoting miscibility sooner. The impact of IFT0 was more pronounced on the dead oil–gas system compared to the live oil–gas system in this study.

Experimental study on the discharge characteristics of air rotating gliding arc

Abstract In this study, the discharge characteristics of air rotating gliding arc are investigated by the synchronous measurements of digital oscilloscope and high-speed camera, and emission spectrum. The discharge evolution in one complete motion cycle exhibits “breakdown-elongation-extinction” process accompanied by the jump of arc root and back-breakdown phenomenon. The discharge evolves from the unstable breakdown mode (U-B), to the transition mode and finally to the stable gliding mode (S-G) by increasing the input voltage or decreasing the tangential and axial gas flow rates. The U-B mode at the input voltage of 120 V is featured by the large reduced electric field and high electron temperature of 1.90 eV, but the arc length and existence time are very short. The S-G mode at the input voltage of 270 V has relatively low breakdown frequency of 0.33 kHz and average breakdown current of 1.31 A, implying that the arc steadily glides and rotates along the spiral electrode. The average electron temperature is 0.64 eV in S-G mode, while the arc length and existence time are longer. The rotational and vibrational temperatures of N2 state are respectively measured to 2200 K and 4400 K in U-B mode, and in S-G mode are 2600 K and 4820 K. From the evolution of emission intensities of measured excited species, it is found that the NOγ band emission intensity generally rises from U-B mode to S-G mode since the gas temperature and arc existence time rise, indicating that S-G mode may be beneficial for the vibrationally-promoted Zeldovich reactions. This study could deepen the understanding of arc characteristics in air rotating gliding arc for selecting a suitable mode to achieve better plasma performance in practical applications.

Precision in practice: An audit study on low-flow anesthesia techniques with desflurane and sevoflurane for cost-effective and sustainable care

Introduction: In the backdrop of escalating healthcare costs and an increasing focus on resource optimization, this audit study delves into the realm of anesthesia management, specifically exploring the application of low-flow anesthesia (LFA). The primary objective was to assess adherence to hospital standards and evaluate the economic implications of LFA (&lt;1 L/min). Materials and Methods: This retrospective audit focused on 700 adult patients undergoing elective surgeries with general anesthesia. Data sources included anesthesia records, electronic recording systems, and audits by a dedicated team. Fresh gas flow rates (FGFRs), minimum alveolar concentration (MAC), and volatile anesthetic consumption were analyzed. Cost comparisons between low-flow and high-flow anesthesia were conducted, employing specific cost per milliliter metrics. Results: The average FGFR during the maintenance phase was found to be 0.45 ± 0.88 L/min. Adherence to hospital standards was notably high, with 94.29% of patients being maintained on low-flow gas rates. The differences in anesthetic consumption between low-flow and high-flow FGFR were statistically significant for both desflurane (12.17 ± 10.84 ml/MAC hour versus 43.12 ± 27.25 ml/MAC hour) and sevoflurane (3.48 ± 7.22 ml/MAC hour versus 5.20 ± 5.20 ml/MAC hour, P &lt; 0.001). The calculated savings per patient with low-flow desflurane and sevoflurane anesthesia compared to high flow were found to be 109.25 AED and 6.74 AED, respectively. Conclusion: This audit advocates for the widespread adoption of LFA as a standard practice. Beyond aligning with hospital standards, the study highlights the multi-faceted benefits of LFA, encompassing economic savings, environmental safety, and enhanced patient care.

A Solidarity Mechanism to Allocate Stored Natural Gas in Crisis

The interruption of natural gas flows via pipeline to Europe in 2022 has demonstrated that supply crises pose a threat. Although member states have demonstrated unity and solidarity, they could be better prepared to respond to such challenges. Currently, member states fill their natural gas storages independently. Cooperation and solidarity could deliver better outcomes by allowing the accumulated reserves of one or more members to be potentially redistributed to help others in need. In this paper we propose some possible guidelines for a potential solidarity framework based on voluntary participation. We argue that the proposed framework can mitigate the risk of supply-disruption of participants and formalize a game-theoretic model in order to capture the basic features of the problem. We demonstrate the operation of the approach using a simple example with risk-averse participants. JEL Classification: C51, C63, C72, L95, Q40

High aspect ratio SiO2/SiN (ON) stacked layer etching using C3HF5, C4H2F6, and C4H4F6

High aspect ratio SiO2/SiN (ON) stacked layer etching using hydrofluorocarbon gases was conducted with various ratios of H, F, and C to achieve higher etching rates and precise profile control. The experimental gases were C3HF5, C4HF5, C4H2F4, C4H2F6, C4H4F6 and C5H2F10. The oxygen gas flow rate and mixing ratio were optimized to maximize mask selectivity while avoiding clogging at the top of the mask. For comparison, C4F6/CH2F2/Ar/O2, and C4F6/C4F8/CH2F2/Ar/O2 were used as reference gas mixtures. The initial screening narrowed the candidate pool to 3 gases: C3HF5, C4H2F6, and C4H4F6. At equivalent power, the C3HF5 condition achieved a 15% faster ON etch rate, and C4H2F6 achieved a 9% faster ON etch rate compared to the reference condition. Only C4H4F6 showed a worse ON etch rate than the reference (∼33%) due to severe mask clogging. Furthermore, C3HF5 achieved a 29% faster ON etch rate under high power conditions. It also achieved a 57% faster ON etch rate without excessively compromising selectivity or bow CD expansion after optimization. We report detailed comparisons of etch rate and clogging while controlling the CD profile in the ON stack process.

Impact of Electrochemical Impedance Spectroscopy Dataset Curation on Solid Oxide Cell Degradation Assessment

Electrochemical impedance spectroscopy (EIS) has become a standard measurement technique for detecting degradation in single cells and stacks of solid oxide cells (SOCs). Depending on the experimental setup and test equipment, instabilities and unexpected results can be observed in EIS measurements. For example, in the low-frequency range, instabilities can be induced by feed gas flow fluctuations. Another phenomenon are parasitic, inductive impedances that degrade the high-frequency range. To compensate for such influences in large EIS data sets, we propose a specially developed EIS data curation pipeline. Based on the results of its application, we demonstrate the impact on the quantitative and qualitative attribution of electrochemical processes from EIS using equivalent circuit modeling and distribution of relaxation times. Furthermore, the substantial differences in the temporal evolution of the latter during long-term experiments are highlighted for EIS measurements obtained at the SOC stack and single cell level. In addition, the significant misestimation of aging rates, especially with respect to the fuel electrode and the high-frequency series resistance, is shown when comparing EIS measurements, few of which exhibit a parasitic inductive impedance.

Contribution of vibrational excited molecular nitrogen to ammonia synthesis using an atmospheric-pressure plasma jet

The contribution of atomic nitrogen is fairly possible in plasma-assisted catalytic synthesis of ammonia since it has high adsorption probabilities on solid surfaces. On the other hand, recently, the contribution of vibrational excited molecular nitrogen to ammonia synthesis has been discussed. In this work, we compared the fluxes of atomic nitrogen and vibrational excited molecular nitrogen with the rate of plasma-assisted ammonia synthesis. We employed an atmospheric-pressure nitrogen plasma jet, and the spatial afterglow of the plasma jet and a hydrogen flow irradiated the surface of a ruthenium catalyst. The fluxes of atomic nitrogen and vibrational excited molecular nitrogen were measured by two-photon absorption laser-induced fluorescence spectroscopy and laser Raman scattering, respectively. The synthesis rate of ammonia had a positive correlation with the flux of vibrational excited molecular nitrogen, while the variation of the synthesis rate with the gas flow rate was opposite to the flux of atomic nitrogen. The experimental results indicate the contribution of vibrational excited molecular nitrogen to the synthesis of ammonia using the atmospheric-pressure plasma, where the flux of vibrational excited molecular nitrogen is more than four orders of magnitude higher than that of atomic nitrogen.

High-Speed Generation of Microbubbles with Constant Cumulative Production in a Glass Capillary Microfluidic Bubble Generator.

This work reports a simple bubble generator for the high-speed generation of microbubbles with constant cumulative production. To achieve this, a gas-liquid co-flowing microfluidic device with a tiny capillary orifice as small as 5 μm is fabricated to produce monodisperse microbubbles. The diameter of the microbubbles can be adjusted precisely by tuning the input gas pressure and flow rate of the continuous liquid phase. The co-flowing structure ensures the uniformity of the generated microbubbles, and the surfactant in the liquid phase prevents coalescence of the collected microbubbles. The diameter coefficient of variation (CV) of the generated microbubbles can reach a minimum of 1.3%. Additionally, the relationship between microbubble diameter and the gas channel orifice is studied using the low Capillary number (Ca) and Weber number (We) of the liquid phase. Moreover, by maintaining a consistent gas input pressure, the CV of the cumulative microbubble volume can reach 3.6% regardless of the flow rate of the liquid phase. This method not only facilitates the generation of microbubbles with morphologic stability under variable flow conditions, but also ensures that the cumulative microbubble production over a certain period of time remains constant, which is important for the volume-dominated application of chromatographic analysis and the component analysis of natural gas.

Permeability and strength of gradient printed permeable steel manufactured by selective laser melting

Based on the forming principle of laser rapid melting and layered manufacturing, the selective laser melting (SLM) process is suitable for the preparation of permeable metal materials with a certain porosity. One of the important applications of this special structure is the development of permeable steel. In this study, the permeable steel with micron-sized controllable pores was prepared by gradient printing using SLM process. The formation and connectivity mechanism of pore structure were analyzed by adjusting the interlayer arrangement of scanning melt channels, and the influence of process parameters on the pore characteristics, permeability and mechanical properties was systematically investigated. The results revealed that the porosity and pore size of permeable steel were effectively improved by controlling the hatch distance and scanning strategy, with the results ranging from 7.81 % to 17.32 % and 57 μm to 121 μm, respectively. Based on the gas permeation test, it was verified that the permeability of permeable steel showed a clear upward trend with increasing porosity, and the results ranged from 2.17 × 10−12 m2 to 4.26 × 10−12 m2, indicating that the pore structure provides a strong basis for gas flow. Moreover, the mechanical properties of permeable steel decreased significantly with the increase of porosity and pore size, and the compressive strength and tensile strength ranged from 1061 MPa to 528 MPa and 1018 MPa to 609 MPa, respectively. The mechanical behavior and deformation mechanism were closely related to the gradient evolution of the pore structure. Overall, the gradient printed permeable steel using SLM process has good permeability and mechanical properties.

Predictive modeling and multi-parametric optimization of catalytic pyrolysis of disposable face mask using a combinational approach of response surface methodology and machine learning: Insights into the influence of waste-derived catalyst

The current study aims to model and optimize the catalytic pyrolysis of face masks incorporating a waste-derived catalyst to analyze the effect of process parameters (temperature, feed-to-catalyst ratio, and inert gas flow rate) on the oil yield of the process. An integrated approach of response surface methodology (R2-0.95) and machine learning (decision trees regression, R2-0.83) demonstrated a higher prediction accuracy and lower error margins. Explainable artificial intelligence tools spotlighted temperature to be the predominant parameter followed by feed-to-catalyst ratio. Experimental oil yield (13.5%) obtained at optimized parameters (516 °C temperature, 3:1 feed-to-catalyst ratio, and 163 mL/min inert gas flow rate) was compared with those predicted through response surface methodology (13.7%) and decision trees regression (13.12%), showcasing an absolute error range of 0.2–0.4 wt%. Gas chromatography-mass spectroscopy analysis of oil highlighted the presence of silica compounds that can be extracted as value-added chemicals. Further, the overall percentage of naphthene's, paraffins, and olefins in the oil were approximated to be around 40.5% based on the peak area. The presence of hydrocarbons in oil having carbon numbers predominantly in the range of gasoline and diesel as well as a high heating value of 36.56 MJ/kg demonstrated its potential to be used as a fuel. The present study demonstrates the feasibility of valorizing the face mask into energy-dense oil comparable to commercial range fuel using a spent adsorbent based catalyst.

Study on multi-stage adjust mechanism of downhole stratification control tool for natural gas hydrate multi-gas combined production gas lift

Accurate control of natural gas flow and pressure is essential to achieving multi-gas combined production of the natural gas hydrates. In this study, a downhole stratification control tool for controlling natural gas flow rate and pressure with a multi-stage throttling structure was innovatively proposed. The multi-stage throttling structure combined an adjustable cage sleeve and a fixed nozzle. The numerical model of the internal flow field of the downhole stratification control tool was established. Through the computer fluid dynamics numerical simulation, the flow field change law inside the spool module of the downhole stratification control tool under different spool structures, different outlet pressures, and different spool openings was analyzed. Moreover, the spool module prototype was processed, and the indoor experiment of the spool's performance of reducing pressure and regulating production was carried out. The results show that the multi-stage throttling structure has the advantages of adjustable spool opening and moderate cooling range and the mass flow of gas inside the spool changes linearly with the opening of the spool. The spool module can accurately control the mass flow of natural gas under high-pressure conditions, and meet the needs of the downhole stratification control tool for accurate gas control.

A particle-resolved direct numerical simulation method for the compressible gas flow and arbitrary shape solid moving with a uniform framework

Compressible particle-resolved direct numerical simulations (PR-DNS) are widely used in explosion-driven dispersion of particles simulations, multiphase turbulence modelling, and stage separation for two-stage-to-orbit vehicles. The direct forcing immersed boundary method (IBM) is a promising method and widely applied in low speed flow while there is few research regarding compressible flows. We developed a novel IBM to resolve supersonic and hypersonic gas flows interacting with irregularly shaped multi-body particle. The main innovation is that current method can solve the interaction of particles and high-speed fluids, particle translation and rotation, and collision among complex-shaped particles within a uniform framework. Specially, high conservation and computation consumption are strictly satisfied, which is critical for resolving the high speed compressible flow feature. To avoid the non-physical flow penetration around particle surface, an special iterative algorithm is specially derived to handle the coupling force between the gas and particles. The magnitude of the velocity difference error could be reduced by 6–8 orders compared to that of a previous method. Additionally, aerodynamic force integration was achieved using the momentum equation to ensure momentum conservation for two-phase coupling. A high-efficiency cell-type identification method for each step was proposed, and mapping among LPs and cells was used again to select the immersed cells. As for the collision force calculation, the complex shape of a particle was represented by a cloud of LPs and the mapping of LPs and cells was used to reduce the complexity of the algorithm for contact searching. The repetitive use of the mapping relationship could reduce the internal memory and improve the efficiency of the proposed algorithm. Moreover, various verification cases were conducted to evaluate the simulation performance of the proposed algorithm, including two- and three-dimensional moving and motionless particles with regular and complex shapes interacting with high-speed flow. Specifically, an experiment involving a shock passing through a sphere was designed and conducted to provide high-precision data. The corresponding results of the large-scale numerical simulation agree well with those obtained experimentally. The current method supports flow simulations at a particle-resolved scale in engineering.

Photosensitive iron–aluminum oxide gas sensor

In this study, the structural, topographic, and optical properties of iron–aluminum oxide (AlxFe2−xO3, 1 > x > 0) thin film grown by co-sputtering method were investigated. Firstly, AlxFe2−xO3 films grown by magnetron RF–DC co-sputtering method were annealed at 540 °C and then XRD analyses were performed. The absorption measurement, Raman shift, XPS, gas sensor measurements, and SEM images were taken, respectively. The band gap energy of the AlxFe2−xO3 samples was obtained and measured as approximately 2.41 eV, and different peaks at various intensities were seen in the XRD analysis. According to the XRD analysis of the AlxFe2−xO3 semiconductor, the peaks occurred at 33.42°, 41.16°, and 54.43° and the XRD analysis results show that the structure is polycrystalline. As seen in the measurement of the AlxFe2−xO3 gas sensors, acoustic gas sensorsgas sensor, the current value increased with the flow of hydrogen gas. This means that the oxygen that hydrogen detached from the thin film surface contributes to the conductivity of the remaining electrons in the structure, which means that the thin film was an n-type semiconductor. It was seen that the AlxFe2−xO3 gas sensor was very sensitive to light. During the feature measurement, it was seen that the current value measured under the light increases considerably.

Flow structure and heat transfer characteristics of sweeping and steady impingement jets with/without chevrons on a semi-circular concave surface

Striving for improved gas turbine performance requires operating at higher gas flow temperatures, posing challenges in preserving the structural integrity of the gas turbine. To respond to these challenges, gas turbine manufacturers have turned to internal cooling and jet impingement to provide an effective solution for cooling the leading edge of the gas turbine blades. Fluidic oscillator is known for its sweeping behavior and expansive coverage of targeted surface and, thus, it can efficiently remove heat. In this study, the author numerically simulated the cooling performance of the leading edge of the gas turbine blades under constant heat flux while using four different configurations of jet impingement: a sweeping jet, a sweeping jet with chevrons, a steady jet, and a steady jet with chevrons. The results showed that the sweeping jet configuration with chevrons outperformed the steady jet configurations owing to oscillating jet impingement and a higher intensity of turbulence that increased the entrainment of jet flow. Under the configuration of a sweeping jet with chevrons, the targeted surface recorded an average Nusselt number that is 19.2% higher than the one with a steady jet without chevrons, along with a more uniform distribution of the surface temperature. The outstanding behavior of the sweeping jet with chevrons is due to the its internal flow behavior, i.e., oscillating flow nature of the sweeping jet with augmented turbulence at the exit of the chevron's nozzle.