Varying Flow Rates Research Articles

Impact of Hydrogen on Emission Reduction in a CI Engine when Fuelled with Blends of Diesel-Waste Cooking Biodiesel

Waste utilisation and emission of greenhouse gases are two of the world's most pressing challenges today. This study seeks to solve the problem generated by the disposal of Waste Cooking Oil (WCO) as a tiny step forward in contributing to the reduction of waste disposal. WCO has a high potential as a bio fuel for internal combustion engines, hence it was chosen for this investigation. WCO of 20% and diesel 80% is used. This study looks at the performance, combustion and emission parameters of a dual fuel compression ignition engine running on WCO biodiesel with a hydrogen additive at atmospheric condition. The parametric study include variation in engine load (0-18 kg) and hydrogen flow rate (3, 6, 9 LPM). The experiment was conducted on a four-stroke diesel (computerized), single cylinder, water cooled power at 5.2 kW at 1500rpm Kirloskar engine. From the experiment overall parametric variation of 35.38%, 34.06% and 32.37% of brake thermal efficiency was obtained and emission was observed. However, with increase of hydrogen flow rate resulted in increased engine performance, increase in CO, NOx and reduction in emission of UBHC and CO2.

Microplastic patterns in riverine waters and leaf litter: Leaf bag technique to investigate the microplastic accumulation trends in lotic ecosystems

Microplastics (MPs) are one of the major ecological concerns of the last years and despite the increasing interest and the rise of many studies regarding freshwater habitats, many aspects about distribution patterns, transport pathways and impacts of MPs in those systems need to be investigated. The present study characterizes the temporal trends of MP concentrations in waters of a riverine stretch of the northeastern Italy, subject to flow rate variations and investigates the MP accumulations patterns in the leaf litter, simulated in situ via leaf bag technique. MP concentrations in the water were significantly and negatively correlated to the flow rate regimes, with higher concentrations observed during low discharge periods. MPs accumulation in leaf bags agreed with trends observed in the water and the presence of wastewater discharge points positively affects the levels of MP contaminations within the leaf bags. These findings seem to suggest that the maintenance of a hydrological regime at relatively high levels in the investigated system could allow to maintain the self-purifying riverine processes and the disposal of microplastics like any other polluting substance. The use of leaf bag technique for the purpose to investigate MP accumulation trends on field provided useful information, is easy to modulate in terms of time periods and allow to record the evolution of the MP patterns also in relation to high flow rate episodes. Our results suggest that the method can be employed in new a perspective, to improve the knowledge about one of the major threats of the Anthropocene.

Influence of parallel and series U-loop configurations on the thermal behaviour of energy piles

Energy piles are foundation piles that have heat exchanger pipes installed in them for exchanging geothermal energy between buildings and the ground through the use of a ground source heat pump (GSHP). This is a cost-effective and environmentally friendly method to supplement heating and cooling of buildings. Heat transfer occurs between the piles and the ground through a heat transfer fluid circulating in the pipes. The heat exchanger pipes in the piles are commonly made from polyethylene pipes formed into U-loops [e.g., 1, 2, 3, 4, 5, 6, 7]. The U-loops are configured into series or parallel configurations to circulate water in the pipes. A number of studies have investigated the thermal and thermo-mechanical behaviour of energy piles with U-loop heat exchangers [e.g., 1, 2, 3, 4, 5, 6, 7]. Despite this widespread research, the fluid flow and temperature variations in the individual U-loops are not well understood for parallel and series U-loops in the piles. Given that the fluid flow behaviour varies between the two configurations [8], it can be hypothesised that the thermal behaviour of the energy piles may vary as well. 
 This study investigates the influence of series and parallel U-loop configurations on the variations in fluid temperatures and flowrates in the individual U-loops of energy piles, and the effects of these variations on the geothermal energy extracted by the piles. Heating experiments were conducted on a set of four field-scale energy piles installed below a 5-storey building in Brighton group sandy soils. The energy piles have a length of 15 m and diameter of 0.9 m, but different numbers of U-loops (1, 2, 3, and 4 U-loops in Piles 1, 2, 3, and 4, respectively). The fluid temperatures and flowrates were monitored in the individual U-loops of the piles that were connected to a plumbing manifold located in the monitoring room (Figure 1). A comparative thermal performance analysis of the two configurations was conducted to derive conclusions on the preferred configuration for improved thermal performance of the piles.
 The flowrate variations and change in fluid temperatures in the individual U-loops at Day 15 of group tests are shown in Figure 2. The flowrates were inconsistent between the U-loops in the parallel configuration but remained constant in the series U-loops. Heat exchange occurred in all the U-loops in parallel, whereas only the first few U-loops in the series configuration exchanged heat with the ground. The results suggest that all the energy piles in the group with parallel U-loops were thermally active and could improve the performance of energy pile systems compared to energy piles with U-loops in series.

Throttling characteristics prediction methodology for combined grooves in directional spool valves under variable flow rates

There is a contradiction between the calculation accuracy and cost when computing the pressure and flow rate. A throttling characteristics prediction methodology for directional spool valve was proposed to balance the contradiction. The throttling characteristics were represented by the flow-number, defined as the product of the flow coefficient and the orifice area, to reveal simultaneously the mapping relationships of the two versus the spool geometry, stroke and flow rate. The pressure and flow rate characteristics at different strokes were obtained through the computational fluid dynamic (CFD) simulations that were validated through bench testing. The concept of saturated flow-number theory was introduced to describe the effects of the flow rate on the flow-number. Models for the saturated flow-number and critical flow rate were established using the U-shape groove, a typical throttling structure, as an example to illustrate the effects of groove structure and opening. The throttling characteristics of the directional spool valve could be predicted by the flow-numbers of the combined grooves. The simulated and experimental results demonstrate that the prediction methodology achieves high calculation accuracy while incurring minimal costs. This methodology holds significant implications for the forward design of valve spool throttling structures.

Ammonia autothermal reformer with air side-stream distribution for hydrogen production

Recently, there has been growing interest in utilizing ammonia through its decomposition process for on-site hydrogen production, primarily due to technical problems in hydrogen generation and storage. As ammonia decomposition is an endothermic reaction, an external heat source is required to facilitate the reaction. To address this, an ammonia autothermal reforming process that directly integrates ammonia decomposition and oxidation using air as the source of oxygen within a single reactor vessel was proposed. This process eliminates the need for additional external heat sources and simplifies the process. The design of the reactor incorporates an air distribution structure that allows for achieving a specified temperature range for the desired reaction. Thermodynamic analysis of the autothermal system revealed that high feed temperature, high reaction temperature, and low pressure are the most beneficial conditions for generating a high yield of hydrogen. The proposed process was simulated to assess its feasibility using kinetic parameters obtained from experimental data in the literature [27]. An optimization problem to minimize the reactor length in designing the proposed reactor was developed. The reactor design produces a high yield of hydrogen while maintaining the reaction temperature within the desired range. Adjusting the air flow rate at distribution points along the reactor to maintain peak temperatures at predetermined levels was shown to provide good load flexibility for variations in ammonia flow rate.

A cooperative control method for safer on-ramp merging process in heterogeneous traffic flow

The on-ramp area is a high-risk conflict zone where traffic accidents frequently occur. Connected and automated vehicles (CAVs) have the potential to enhance the safety of the merging process through appropriate cooperative control methods. This paper proposes a cooperative control method for safer on-ramp merging processes in heterogeneous traffic flow. Firstly, the gap selection process of ramp vehicles is described, thus all feasible virtual platoon results can be summarized. Next, the vehicle bond (VB) is used to describe the connection mode between vehicles within the virtual platoon. A two-layered gap selection function is proposed to ensure a safer merging process. The first layer aims to minimize the number of empty VBs, while the second layer considers fairness with respect to delay. To evaluate the control effectiveness, time exposed time-to-collision (TET), cumulative risk (CR), and conflict-potential mergence ratio (CPMR) are selected as the safety evaluation indicators. The simulation results show that the gap selection control moves the merging positions of ramp vehicles forward, resulting less risk of merging. It significantly enhances the safety of on-ramp merging without compromising traffic efficiency. At a flow rate of 650 veh/h for both the mainline and ramp, and a CAV penetration rate of 0.1–0.9, the gap selection control group achieves a decrease rate of about 0.3–0.6 for average TET and CR compared to the non-control group. In the pure CAV environment, the decrease rate can reach about 0.9. Sensitivity analysis indicates that the gap selection control is effective across varying flow rates and steady speeds. The optimal control effect is achieved when the length of the communication area ranges from 100 to 200 m.

Application of Quality by Design in RP-HPLC for Robust Impurity Profiling and Stability Assessment of Doxylamine

The primary purpose of this research was to create and validate a doxylamine detection method using reverse phase high performance liquid chromatography (RP-HPLC) for use in pharmaceutical formulations and bulk materials. Quality by design (QbD) served as the inspiration for this approach. The method was developed by running a C18 column at 1-mL/min through a mobile phase of 60 parts methanol to 40 parts 0.1% OPA water (pH 2.8). The detection was done with a UV detector set to 259 nm. All requirements for system applicability were satisfied by the suggested approach, including an acceptable asymmetry factor and an adequate number of theoretical plates. A correlation coefficient (R2) of 0.9990 was used to confirm linearity over a concentration of 10–50 g/mL. The approach showed good accuracy by a mean %recovery ranging from 99.59–101.45% and a %RSD between 0.11 and 0.81. Precision tests conducted both intraday and across days showed that the medication content stayed within allowable bounds. The approach was found to be robust, with only minor variations in flow rate, mobile phase composition, and detecting wavelength significantly affecting the accuracy and specificity. A 0.71 g/mL LoQ and a 0.23 g/mL LoD were determined to be analytical limits of detection and quantification, respectively. This study substantiates the development of a reliable, long-lasting, and cost-effective QbD-based RP-HPLC method suitable for the comprehensive analysis of doxylamine in tablet formulations and bulk dosage

Numerical study of unsteady tangent hyperbolic fuzzy hybrid nanofluid over an exponentially stretching surface

The significance of fuzzy volume percentage on the unsteady flow of MHD tangent hyperbolic fuzzy hybrid nanofluid towards an exponentially stretched surface is scrutinized. The heat transport mechanism is classified by Joule heating, nonlinear thermal radiation, boundary slippage, and convective circumstances. Ethylene glycol (EG) as a host fluid along with the nanomaterial’s Cu and {text{Al}}_{{2}} {text{O}}_{{3}} are used for heat transfer analysis is also considered in this investigation. The nonlinear governing PDEs are meant to be converted into ODEs employing appropriate renovations. Then, a built-in MATLAB program bvp4c is employed to acquire the outcome of the given problem. The variation of flow rate, thermal heat, drag force and Nusselt number and their influence on fluid flow with heat transfer have been scrutinized through graphs. An increase in thermal radiation, power law index and nanoparticle volume friction heightens the heat transmission rate. Skin friction is diminished by swelling the power-law index, Weissenberg number, and ratio parameters, whereas it is increased by enhancing the magnetic parameter. The heat transfer rate upsurges with an increase in Weissenberg number and nanoparticle volume fraction. Also, the nanoparticle volume percentage is expressed as a triangular fuzzy number (TFN). The triangular membership function (MF) and TFN are regulated by the chi - {text{cut}} parameter, which has a range of 0 to 1. In comparison to nanofluids, hybrid nanofluids have a higher heat transmission rate, according to the fuzzy analysis. This investigation has applications in the areas of paper manufacturing, metal sheet cooling and crystal growth.

Adsorption performance and kinetics of Cr(VI) onto activated carbons derived from the waste leaves of invasive plants Rhus typhina and Amorpha fruticosa.

To maximize the potential of biomass from invasive plants, waste leaves from Rhus typhina (RT) and Amorpha fruticosa (AF) were used to prepare activated carbons (ACs) for the efficient removal of chromium from wastewater. Six ACs were prepared by CO2 activation at 850°C with varying flow rates (500, 1000, and 1500mL/min) and characterized by yield, pH, N2 adsorption isotherm, FTIR, SEM, TG, and XPS. The adsorption isotherm and kinetics for chromium removal were analyzed. The outcomes showed that the ACs had mesoporous structures with specific surface areas of 408.05-701.01 m2/g and pore volumes of 0.360-0.653 cm3/g. The pores are distributed among the agglomerated nanoparticles on the surface of the granules. The existence of two kinds of chromium compounds and two valance states, Cr(III) and Cr(VI), in spent ACs was identified by the FTIR and XPS spectra. The Cr (VI) equilibrium data and adsorption kinetics were well-fit with the Langmuir isotherm (R2 = 0.936-0.967) and pseudo-second-order kinetic models (R2 = 0.795-0.937). The maximum Langmuir Cr adsorption capacities of ACRT1.0 and ACAF0.5 were estimated to be 266.54 and 255.21mg/g at pH = 2.0, respectively. Concentrations of Cr(III) and Cr(VI) in filtrates after equilibrium, combined with XPS and TGA analysis of spent ACs, illustrated that Cr(VI) was converted to the less harmful trivalent chromate Cr(III) during the adsorption processes. Cr(III) and Cr(VI) probably formed compounds with carbon and nitrogen atoms on the surfaces of ACs. ACs with abundant surface N-H groups achieved high Cr adsorption performance. The waste leaves from these invasive plants are suitable for producing cost-effective and efficient ACs for removing Cr (VI) from water by chemical adsorption.

THE STUDY ON THE IRREGULARITY OF WATER COLLECTION AND DISTRIBUTION BY POROUS PIPES IN FREE-FLOW WATER MOVEMENT

One of the main utilities used to obtain drinking water in households and drinking water supply in towns are filters with drainage distribution and diversion systems in their main structural elements. The filters are equipped with porous pipes for distributing and collecting water to increase efficiency and reliability. Therefore, obtaining reliable methods for their calculation is of scientific and practical interest. The article notes that water in distribution and collection pipelines moves with a variable flow rate along the way. Moreover, the inflow or outflow of water depends on the pressure variable along the length of the pipe. If the movement is free-flowing, it depends on the variable water level. While for porous pipes, this movement is continuous. The subject of fluid moving with a variable flow rate has been studied by many authors; however, the dependences obtained in those cases mainly concerned perforated pipelines and open trays. The authors study the operation of a porous pipe under the conditions of free-flow movement, which is described by two equations, the movement of fluid inside the pipe and the movement of fluid through the pipe's walls. The article indicates the complexity of this problem. Namely, the fact that these equations are interconnected. That is, the fluid flow through the pipe walls depends on the depth of the water layer in the pipe, which is determined by the equation of motion inside the pipe. Similarly, the law of depth change is defined, particularly by the laws of the inflow. A mathematical model was obtained during the investigation of the uneven distribution and collection of water by a porous pipe. Based on this model, an approximate calculation method was developed, which makes it possible to get the value of the average flow depth in the pipe from the critical depth of water installed at the end of the pipe. To simplify the calculations, the article gives the corresponding nomograms. The validation of the model was carried out on an experimental setup. The analysis of the experimental data showed good correspondence to the calculation results performed according to the approximate method, i. e. the deviation of the flow depth in the middle section does not exceed 1.5%.

Experimental and numerical study of a condensation-driven dilution refrigerator

Dilution refrigerators are widely used in the fields of condensed-matter physics and quantum technology. For small cooling power applications, condensation-driven dilution refrigerator utilizes a condensation pump to achieve 3He cryogenic circulation and has advantages of compact structure, small 3He usage, and convenient operation. Related published research mainly focused on the overall system performances, and in-depth thermodynamics and fluid dynamics analyses are lacking. In this paper, a condensation-driven dilution refrigerator was experimentally studied and corresponding numerical simulations were performed. The results of experiments and simulations were compared and analyzed. In the experiments, lowest no-load temperature was 84.4 mK. The experimental cooling power was 1.91 μW @100 mK with a still heating power of 280 μW and the corresponding COP and second-law efficiency of the dilution cold cycle at 100 mK reached 0.0068 and 2.4% with the high temperature of 452 mK, respectively. The experiments also revealed that the charged mixture amount had a certain influence on the performance. With the help of simulations, the heat leak to the mixing chamber was estimated and certain intrinsic features of the cycle were enlightened. The heat leak and Kapitza resistance in the mixing chamber are possibly the main reasons for the differences between experimental and simulation results. Extended study based on the simulation also showed how flowrate variation changed the liquid column height difference and how the requirement of gas circulation and liquefaction set the limit on the minimum still temperature.

Techno-economic assessment of retrofitted parabolic trough collector for Kalina power cycle

In this study, the integration of a Kalina cycle with a parabolic trough collector (PTC) was proposed. The PTC underwent retrofitting with a dual-layer coating on the receiver tube, consisting of an inner layer of MXene-doped black paint and an outer layer of silicon oxide anti-reflective coating. This coating configuration aimed to reduce re-radiation losses and enhance the solar absorptivity of the absorber surface. Additionally, MXene (Ti3C2) nanoparticle with weight concentration (0.05–0.3 wt%) is suspended in de-ionized water with varying flow rate (1–5 lpm) is used as heat transfer fluid owing to its superior thermophysical and heat transfer capabilities. Experimental analysis and mathematical modeling are conducted to assess thermal and economic performance. The outcomes reveals optimal weight concentration and flow rate to be 0.15 wt% and 3 lpm, respectively. Comparing conventional and coated PTCs, the maximum thermal efficiency was reported as 48.17% and 58.5%, respectively. The corresponding maximum useful heat generation values were approximately 422.72 kW and 513.312 kW. The thermal efficiency of the Kalina cycle calculated was 11.10%. The conventional PTC-driven Kalina cycle had a Levelized cost of electricity of $0.164/kWh and a payback period of 7 years. Meanwhile, the coated PTC-driven Kalina cycle had a Levelized cost of electricity of $0.15/kWh and a payback period of 6.42 years. The study's findings highlight the superior performance and economic feasibility of the coated PTC-driven Kalina cycle over the conventional PTC setup.

Exploring thermal isomerisation in gas chromatography analyses using natural pyrethrins: Comparison of comprehensive two-dimensional and one-dimensional gas chromatography

This study aims to assess and qualitatively compare the visual presentation of chromatographic data from the isomerisation of natural pyrethrins – a group of pesticides derived from Chrysanthemum flowers – using one-dimensional gas chromatography (1DGC) and comprehensive two-dimensional gas chromatography (GC×GC). Molecular structural changes, such as thermal isomerisation in this case, occur during gas chromatography injection and separation, to provide characteristic patterns which may not be routinely recognised on the 1D chromatogram. To demonstrate the influence of analytical method parameters on isomerisation processes, variations in oven temperature (isothermal vs. temperature programmed analysis), inlet mode (split vs. splitless), inlet temperature, and carrier gas flow rate were investigated. Increasing oven temperature was the most significant factor affecting isomerisation. Splitless injection mode and increasing inlet temperature promoted isopyrethrin formation, while the effect of inlet temperature appeared minimal with a split injection technique, most likely due to the short residence time in the inlet. Increased carrier gas flow rates in a temperature programmed analysis reduced retention time and minimised isomerisation. The unique presentation of isopyrethrin peaks on a GC×GC contour plot allows for facile recognition of isomerisation especially at low concentrations, simplifies chromatogram interpretation, and aids in analyte identification. It also confirms that the isomerisation process is irreversible since the pyrethrin I and II compounds are absent throughout the bridge formation. These benefits support the use of GC×GC over 1DGC to study isomerisation. Additionally, due to limited data in the literature, Kováts retention indices and linear retention indices of the natural pyrethrins, including isopyrethrins, were experimentally determined on four columns: DB-5 ms UI, Rxi-17Sil MS, SLB-IL60i, and SLB-IL111i.

Ignition Investigation of Pure Biodiesel in A Research Engine with Dual Fuels

Under the effect of acetylene (C2H2) as a secondary energy in diesel engines powered by Acacia methyl ester (ABD) is investigated in this study. This experimental work is carried out on single cylinder, water cooled, direct injection diesel engine. At the intake manifold air and C2H2 was combined and mixture will have specific stream rate (2 and 4 lpm). In a diesel engine, the ignition analysis of changed fuels under varied Mean Effective Brake Pressure (BMEP) is assessed and contrasted with diesel by adjusting the apparatus load between 01 and 05 BMEP. This research looks at C2H2 as a sustainable twin fuel with the goal of lowering diesel apparatus emissions while improving performance. Experiments demonstrated that supplying C2H2 at 2 and 4 Litres per minute (lpm) results in faster flame velocity and greater flammability for ABD, resulting in enhanced efficacy and improved combustion patterns. Because of its higher flammability and longer C-H chain, acacia methyl ester with acetylene (ABD-C2H2) at 2 lpm and ABD-C2H2 at 4 lpm reduced hazardous diesel motor exhaust compared to biodiesel alone. According to the findings of this investigation, adding acetylene at varied flow rates improves biodiesel's ignition patterns in a diesel engine with no changes.

Clot embolization studies and computational framework for embolization in a canonical tube model

Despite recent advances in the development of computational methods of modeling thrombosis, relatively little effort has been made in developing methods of modeling blood clot embolization. Such a model would provide substantially greater understanding of the mechanics of embolization, as in-vitro and in-vivo characterization of embolization is difficult. Here, a method of computationally simulating embolization is developed. Experiments are performed of blood clots formed in a polycarbonate tube, where phosphate-buffered saline is run through the tube at increasing flow rates until the clot embolizes. The experiments revealed embolization can be initiated by leading edge and trailing edge detachment or by non-uniform detachment. Stress-relaxation experiments are also performed to establish values of constitutive parameters for subsequent simulations. The embolization in the tube is reproduced in silico using a multiphase volume-of-fluid approach, where the clot is modeled as viscoelastic. By varying the constitutive parameters at the wall, embolization can be reproduced in-silico at varying flow rates, and a range of constitutive parameters fitting the experiments is reported. Here, the leading edge embolization is simulated at flow rates consistent with the experiments demonstrating excellent agreement in this specific behavior.

Simulation and multi-objective optimization of Claus process of sulfur recovery unit

Although natural gas can provide energy with minimum greenhouse gas emissions compared to other fossil-derived fuels, the sulfur removal is the major challenge associated with its use in various applications. In this work, sulfur recovery unit was simulated using the Aspen HYSYS. The environmental, energy, and economic analyses of the process based on special criteria (profit (PBT), weighted global warming potentials (WGWP), and energy consumption (NQ)) were analyzed. After consideration of the sensitivity analysis of the process, the single and multi-objective optimizations were carried out by integrating the HYSYS simulations with MATLAB codes with the Genetic Algorithm method. Feed temperature, feed molar flow rate, combustion air temperature, and reboiler temperature are decision variables in this work. The results show that with increasing the feed temperature, the energy consumption decreases, so, the cost of energy decreases. Also, with increasing the feed temperature, and reduction of consumed energy, the equivalent CO2 emission (which is calculated based on total energy consumption) reduces, so, WGWP decreases. Maximization of PBT, Minimization of WGWP, and Minimization of NQ were considered as the single objective optimizations, separately. Optimum values of decision variables were found. For multi-objective optimization, three different cases were considered: Case 1 (Max. PBT and Min. WGWP), Case 2 (Max. PBT and Min. NQ), Case 3 (Min. WGWP and Min. NQ). In all these cases, it can be found Pareto optimal frontier. The results show that the feed molar flow rate and air combustion temperature variables have more effect than other variables.

Thermo-hydraulic performance augmentation in residential heating applications using a novel multi-fluid heat exchanger with helical coil tube insertion

This study proposes a heat transfer augmentation technique using a brazed helix tube (BHT) fabricated from a helical tube with precision brazing between coil turns in a novel multi-fluid heat exchanger (NMFHE) for simultaneous heating of water and air using solar energy. The thermo-hydraulic performance of the present NMFHE for residential heating of water (CW) and air (CA) using hot water (HW) is tested experimentally. Nusselt number and friction factor for fluid flow inside the NMFHE are calculated as the thermo-hydraulic measure relating to variations in flow rate, inlet temperature, and flow configuration. Optimal flow parameters for overall optimized performances that is, maximum heat transfer and minimum pressure drop in NMFHE are determined using the Taguchi Grey relational approach. NMFHE performs efficiently in the Counterflow (cold water reverse) flow configuration with HW flow rate of 100 LPH, CW flow rate of 200 LPH, and HW inlet temperature of 70°C. The CW flow rate has the greatest impact on both the Nusselt number and friction factor, with a contribution of 82.37% and 93.42%, respectively. A confirmation test has been conducted to validate the findings, revealing a significant performance improvement of 32.19% when using the Grey relational grade model.

Numerical study on the indoor flow field and ventilation performance in the power room of a hybrid locomotive that passes through a tunnel

Under the background of energy saving, emission reduction, and green transportation, the electrification construction of railway lines is difficult owing to long cycles and high costs. Hybrid locomotives have emerged as fuel locomotives that can run on electrified lines and that achieve energy saving, emission reduction, and railway emergency on non-electrified lines. Train power equipment is highly integrated in the locomotive power room, which leads to the ventilation and heat dissipation performance of indoor high-heat equipment becoming one of the main factors that affect the safe operation of trains. This study focuses on the flow field and ventilation of locomotive power rooms in railway vehicle/tunnel systems and explores the variation of the ventilation flow rate and flow field in a power room when trains pass through a tunnel at different speeds. Based on the unsteady Reynold-averaged Navier–Stokes (RANS) equations and shear-stress transformation (SST) k-ω turbulence model, the relative motion between a train and a tunnel is simulated by sliding mesh, and the related algorithm settings are verified through experiments. The results show that: train speed is linearly related to the air inlet flow rate, and trains have a critical speed, which affects the original indoor air-cooling circulation system. This critical speed is reduced by the tunnel environment; The propagation and superposition of the pressure wave in a tunnel have no evident effect on the flow rate of the power room vent; Train speed is negatively correlated with the fan efficiency; thus, it deteriorates the fan efficiency in the tunnel environment; The symmetrical distribution of ventilation openings in a power room can effectively balance the fresh-air flow, but it is not conducive to cooling equipment located near the locomotive. These conclusions can contribute to improving future designs of the ventilation systems of hybrid electric locomotive power rooms.

Surface modification of polypropylene hollow fiber membranes using fluorosilane for CO2 absorption in a gas-liquid membrane contactor

Conventional methods for improving the hydrophobicity of polypropylene (PP) membranes to prevent wetting phenomena require complex pretreatment procedures in order to activate the surface for enabling the reaction with fluorosilane (FS)-based materials. This study successfully prepared PP membrane contactors with enhanced hydrophobicity through a simple single-step dip-coating method using perfluoroether-grafted silanes for CO2 capture. The FS coating layer on the PP membrane surface was confirmed through ATR-FTIR spectroscopy, XPS, FE-SEM, and EDS. Furthermore, the evaluation of the CO2 absorption performance and long-term stability of the FS-coated PP membrane according to the variation of the gas flow rate (50, 100, 200, 400, and 800 mL/min) confirmed the superior chemical stability and durability of our membranes to those of previously reported hydrophobic membranes. The as-prepared FS-coated PP membrane expands the application scope of gas-liquid membrane contactors for CO2 capture from the flue gas of coal-fired power plants.

Bio-based synthesis of a sustainable Nano drag reducing agent for sprinkler irrigation systems

High-grade silica Nano particles were extracted from rice husk using a straightforward thermochemical method. The specifications of the isolated Nano particles were verified using a variety of material characterization techniques. Siloxane and silanol groups were notably visible in the spectra obtained using Fourier transform infrared spectroscopy. Scanning Electron Microscopy images revealed main Nano particles alongside secondary Micro particles. The size of the particles varied from 14.56 to 33.72 nm. The drag reduction experiments were took place in a facility that uses a forced closed loop. The extracted Nano silica was mixed with faucet water at a weight concentration of 50 to 400 mg/l to reduce drag. Records of pressure loss were obtained along a 186 cm carbon steel tube with internal diameters of 1.6 and 2.7 cm and variable flow rates of solutions at a comfortable temperature of 25 °C. The friction factor values were found to be around Blasuis asymptote for pure water but they were found to be near maximum drag reduction asymptotes when using the Nano material. A maximal drag reduction of nearly 68 % was achieved by using 400 ppm of Nano silica. It was observed that there is a crucial Reynolds number around 96000 that should not be surpassed since any additional increase results in a drop in drag reduction. Furthermore, a relationship between wall shear stress and velocity of the fluid was established.