Low Pressure Drop Research Articles

Optimizing microchannel heat sink performance: Effect of step-gap design and contraction on flow boiling stability and heat transfer

Liquid cooling with cold plates (microchannels) is an advanced thermal management technique used in high-performance electronics and computing systems. Conventional microchannels have a straight fin array that shows instabilities during two-phase flow boiling. The present experimental investigation continues previous studies to explore the effects of combining the contraction before the microchannels (CBM) and a step gap above the microchannels (SGAM) in the enclosed cover of the heat sink to improve two-phase convective boiling performance. The microchannel heat sink is sized at 49 mm × 52 mm, featuring a channel width of 200 μm and a height of 3 mm, with a fin thickness of 200 μm. Dielectric fluid HFE-7000 was used as the working fluid, and the mass flux ranges from 30 to 260 kg/m2·s, with concentrated heat flux varying from 50 to 156 W/cm2. The results reveal that the combination configuration significantly reduces pressure drop by approximately 23–56 % lower than that of the plain (Conventional) configuration. This combination of configurations is especially effective at a high heat flux above 100 W/cm2. Experimental results indicate that the combination configuration lowers wall superheat temperatures compared to the plain sample, therefore enhancing the overall heat transfer coefficient by 30–154 % across the tested mass flux range. These findings underscore the potential of combining contraction before microchannels (CBM) and step gap above microchannels (SGAM) configurations to significantly enhance flow boiling stability and heat transfer performance while incurring a much lower pressure drop penalty.

Enhanced Glycerolysis of Fatty Acid Methyl Ester by Static Mixer Reactor.

This study investigates the synthesis of monoglycerides (MGs) and diglycerides (DGs) from glycerol (G) and fatty acid methyl ester (FAME) using a static mixer reactor (SMR), which combines a static mixer (SM) with a reactor tank. The SMR integrates Kenics static mixers (KSM) and low-pressure drop static mixers (LPDSM) with varying length-to-diameter ratios (L/D = 1.0 and 1.5). Keys glycerolysis parameters, including the G:FAME molar ratio of 2:1-3:1, 2-3 wt % potassium hydroxide (KOH), and reaction time of 30-90 min at 150 °C were systematically explored. The SMR design allows precise control over the reaction time without altering the feed flow rate or tube length and avoiding agitator leakage. The optimal operating conditions, determined through a face-centered central composite design, resulted in 71.35% MGs and 14.20% DGs at a 3:1 molar ratio of G to FAME, 3 wt % KOH, 60 min, and 150 °C using an LPDSM with an L/D of 1.5. In comparison, an LPDSM with an L/D of 1 achieved 79.28% MGs and 10.17% DGs under the same conditions. When applied to purified crude glycerol, these conditions yielded 61.09% MGs and 23.44% DGs. The study found that a lower L/D ratio improved the mixing efficiency but increased the pressure drop. The SMR demonstrated superior performance in glycerolysis compared with conventional stirred tank reactors and ultrasonic probe reactors, indicating its potential for enhanced industrial application.

Packing Incubation and Addition of Rot Fungi Extracts Improve BTEX Elimination from Air in Biotrickling Filters.

The removal of benzene, toluene, ethylbenzene, and xylene (BTEX) from air was investigated in two similar biotrickling filters (BTFs) packed with polyurethane (PU) foam, differing in terms of inoculation procedure (BTF A was packed with pre-incubated PU discs, and BTF B was inoculated via the continuous recirculation of a liquid inoculum). The effects of white rot fungi enzyme extract addition and system responses to variable VOC loading, liquid trickling patterns, and pH were studied. Positive effects of both packing incubation and enzyme addition on biotrickling filtration performance were identified. BFF A exhibited a shorter start-up period (approximately 20 days) and lower pressure drop (75 ± 6 mm H2O) than BTF B (30 days; 86 ± 5 mm H2O), indicating the superior effects of packing incubation over inoculum circulation during the biotrickling filter start-up. The novel approach of using white rot fungi extracts resulted in fast system recovery and enhanced process performance after the BTF acidification episode. Average BTEX elimination capacities of 28.8 ± 0.4 g/(m3 h) and 23.1 ± 0.4 g/(m3 h) were reached for BTF A and BTF B, respectively. This study presents new strategies for controlling and improving the abatement of BTEX in biotrickling filters.

Low pressure-drop CuO/CeO2/UiO-66 catalysts for H2 purification

Pressure drop is responsible of a great part of the energy cost in industry due the energy consumed by pumps driving a fluid through the installation, and heterogeneous catalysis industrial processes suffer from this pressure drop penalty. This study demonstrates that UiO-66 significantly improves the catalytic performance of the CuO/CeO2 active phase for preferential CO oxidation in H2 streams with regard to a conventional γ-Al2O3 carrier due to the particular porous and crystalline properties of MOF materials. A packed bed of UiO-66 produces very low-pressure drop in comparison to conventional catalytic carriers, such as γ-Al2O3 or beta zeolite, being 4 times lower for UiO-66 than for γ-Al2O3 under 2 L/min flow of N2, and this ratio increases and approaches ∞ for lower gas flow rates. This feature of UiO-66 not only decreases the energy required to pump gases through the catalytic bed, but also improves catalytic performance of UiO-66-supported catalysts due to the enhanced gas diffusion into the catalytic bed. The reaction gases flow through the interparticle space left by the catalyst in a packed bed of CuO/CeO2/γ-Al2O3, and this produces high pressure drop, preferential gas pathways and mass transport limitations, negatively affecting the reaction rate. On the contrary, the reaction gases are able to flow through the UiO-66 material without channel constrictions, and the CuO/CeO2/UiO-66 catalysts avoid the gas diffusion restrictions of conventional catalysts.

Experimental study on flow patterns and pressure gradient of decaying swirling gas-liquid flow in a horizontal pipe

The utilization of swirling flow in multiphase flow devices is prevalent for purposes such as mixing, separation, stabilization, and heat transfer enhancement, primarily owing to its characteristic of inducing low-pressure drop. In the nuclear industry, for example, two-phase swirling flow is applied in the nuclear gas generator to improve gas quality. In this study, an experimental investigation was conducted on the decaying swirling flow of gas-liquid in a horizontal pipe equipped with a vane-type swirler. The flow patterns were visually examined, and the pressure gradients along the test pipe and across the swirler were measured. The findings suggest the presence of four distinct swirling flow patterns at the swirler outlet (z/D = 0), namely chain flow, swirling gas column flow, swirling intermittent flow, and swirling annular flow. Because of swirl decay, these swirling flows recover their original pattern approximately 70D downstream from the swirler, with the exception of the swirling gas column flow. The flow regime maps at z/D = 10, 40, 70 and 100 are proposed and the pattern-based pressure gradient characteristics are analyzed. It is shown that the pressure gradient rises as both gas superficial velocity (jg) and liquid superficial velocity (jl) increase. The largest pressure gradient occurs within the swirler section, while the lowest is found upstream of the swirler. Near the swirler outlet (z/D = 0–33), the pressure gradient is approximately 1.5–2.3 times higher than at z/D = 33–67. Further downstream, at z/D = 67–100, it is 2.2–3.5 times greater, depending on the flow patterns.

3D Porous Nanocellulose Based Filter from Palm Bunch Using Tert‐Butyl Alcohol‐Assisted Pore Inducive Technique for Airborne Particulate Matter Retention

AbstractEnvironmental hazards, especially particulates, and microbiological pollutants, have resulted in significant negative impacts on human health. In this study, 3D biodegradable cellulose filters were made from nanocellulose and tested for the removal efficiency of airborne particulates. Cellulose was first extracted from palm empty fruit bunches (EFBs) using green Deep Eutectic Solvents (DESs) under moderate temperature and then homogenized at high pressure to produce cellulose at the nanoscale size. Three types of renewable choline chloride (ChCl)‐based DESs were used: lactic acid, 1,3‐butanediol, and oxalic acid. The maximum cellulose yield from DES pretreatment was 38.78 % based on raw EFB (100 % cellulose yield based on cellulose in EFB) with ChBu60 C and the maximum nanocellulose yield was 68.49 % based on cellulose in EFB with ChLa80 C after 12‐pass high pressure homogenization. The cellulose air filter was fabricated using tert‐butyl alcohol (tBuOH) solvent exchanged under freeze‐drying conditions and characterized by different state‐of‐the‐art techniques. It was shown that the ChBu80 C filter had the lowest pressure drop (10.16 mmH2O or 2.07 mmH2O cm−2) and the maximum particle filtration efficiency (32.51 % for 0.1 μm and 93.63 % for 1.0 μm particles). The process simulation and techno‐economic analysis were performed for nanocellulose production and air filter fabrication to select the most feasible technology.

Flow Performance Analysis of Non-Return Multi-Door Reflux Valve: Experimental Case Study

Non-return multi-door reflux valves are essential in fluid control systems to prevent reverse flow and maintain system integrity. This study experimentally analyzes the flow performance of multi-door check valves under different operating conditions, focusing on pressure testing and evaluating their effectiveness in preventing backflow. A wide-ranging experimental setup was designed and implemented to simulate real-world scenarios, facilitating accurate measurement of flow rates, pressure differences, and valve response times. The collected experimental data were analyzed to evaluate the valve’s performance in terms of flow capacity, pressure drop, and hydraulic efficiency. Additionally, the effects of factors such as valve size, valve configuration, and fluid properties (water) on performance were considered. It was found that the non-return multi-door reflux valve has been proven effective and reliable in preserving system integrity and maintaining unidirectional flow at the same time during pressure testing. It exhibits no backflow, remains stable and constant across varied flow conditions, and demonstrates a low pressure drop and high flow capacity, making it suitable for critical pressure testing applications. The response curve revealed that valve opening takes longer to reach higher flow rates than closing, indicating pressure instability during transition periods. This non-linear relationship indicates possible irregularities in pressure drop response to flow rate changes, highlighting potential areas for further investigation.

Water-retaining slurry washcoat for high-loading and robust CuMnOx structured catalyst toward durable monoxide oxide purification from real flue gas

Structured catalysts play key roles in many industries with the advantages of low pressure drop and efficient mass transfer. The copper-manganese oxide (CuMnOx) as a cost-effective catalyst has been widely applied in gas purification, but still lack efficient structured catalyst due to the challenge in controlling its slurry and coating quality. In this work, this challenge was addressed by introducing the water-retaining agent (WRA) into slurry with sophisticatedly designed conditions. The effects of the type and dosage of WRA, pH value, and temperature on slurry properties including viscosity, stability, and water-retention were systematically studied, and the slurry property-coating quality relationship was correlated. The preferred slurry and coated layer could be segregated into sub-millimeter-sized water-retaining regions where catalyst and binder particles were well dispersed and connected. After slow release of water and organic during drying and calcination, the CuMnOx structured catalyst with uniform, defect-free and dense coating was obtained, showing high loading (>160 kg/m3), great mechanical strength (powder shedding rate < 1 wt%), and no blockage for practical use. The robustness of the structured catalysts was validated by a scale-up preparation of 2 m3 volume amount for CO purification from real ore-sintering flue gas in a steel plant, which achieved the CO catalytic efficiency maintaining over 90 % for more than 1440 h. This work showcases an efficient strategy for structured catalyst preparation and expands the gas purification application of the industrially-favored CuMnOx.

An innovative 3D wave channel design for boosting the dynamic response of proton exchange membrane fuel cell stack

The dynamic response of proton exchange membrane fuel cell (PEMFC) is a crucial metric for evaluating these systems in vehicular applications. The forced convection effect can significantly enhance the dynamic response capabilities of proton exchange membrane fuel cells. In this study, we propose the application of the forced convection effect within a parallel flow field. This approach retains the advantages of low pressure drop at the inlets and outlets of the parallel flow field and facilitates rapid distribution of reaction gases, while simultaneously enhancing the dynamic response of actual PEMFC stacks without compromising drainage efficiency. we propose an innovative 3D wave channel design for PEMFC. Specifically, we design and assemble a stack optimized for performance. The proposed design is tested against the traditional 2D straight channel stack, with the 3D wave channel stack demonstrating an increase in peak power density by 8.05% to 33.92% across a relative humidity range of 20% to 100%. This novel design outperforms the 2D straight channel design in terms of gas distribution uniformity, and enhancedmass transfer to the diffusion layer, as well as reduction of concentration polarization in the PEMFC. It also enhances self-humidification under low humidity conditions. Most importantly, the 3D wave channel stack exhibits a superior dynamic response, with voltage fluctuations after current loading being 74.36% to 91.15% lower than those of the 2D straight channel stack. Furthermore, the 3D wave channel stack maintains superior voltage stability under starvation conditions. The findings from this study contribute significantly to optimizing the dynamic response capability of PEMFC systems, highlighting the potential of the 3D wave channel design in enhancing PEMFC performance.

Multi-Dimensional Modelling of Bioinspired Flow Channels Based on Plant Leaves for PEM Electrolyser

The Polymer Electrolyte Membrane Water Electrolyser (PEMWE) has gained significant interest among various electrolysis methods due to its ability to produce highly purified, compressed hydrogen. The spatial configuration of bipolar plates and their flow channel patterns play a critical role in the efficiency and longevity of the PEM water electrolyser. Optimally designed flow channels ensure uniform pressure and velocity distribution across the stack, enabling high-pressure operation and facilitating high current densities. This study uses flow channel geometry inspired by authentic vine leaf patterns found in biomass, based on various plant leaves, including Soybean, Victoria Amazonica, Water Lily, Nelumbo Nucifera, Kiwi, and Acalypha Hispida leaves, as a novel channel pattern to design a PEM bipolar plate with a circular cross-section area of 13.85 cm2. The proposed bipolar design is further analysed with COMSOL Multiphysics to integrate the conservation of mass and momentum, molecular diffusion (Maxwell–Stefan), charge transfer equations, and other fabrication factors into a cohesive single-domain model. The simulation results showed that the novel designs have the most uniform velocity profile, lower pressure drop, superior pressure distribution, and heightened mixture homogeneity compared to the traditional serpentine models.

Amine/vermiculite composite aerogels fabricated by polyethyleneimine-induced vermiculite nanosheet gelation for efficient direct air capture

Direct air capture (DAC), being able to remove the accumulated CO2 in atmosphere and CO2 carbon emission from discrete sources, is a promising technology for mitigating the global greenhouse effect and achieving carbon neutrality. However, achieving high-capacity, low-cost DAC of CO2 through simple methods remains a significant challenge. In this study, a simple, cost-effective, and environmentally friendly method for fabricating amine/vermiculite composite aerogels is proposed for capturing CO2 from ambient air. Natural two-dimensional material, vermiculite nanosheets with exposed surface and intrinsic negative charge, was utilized as the the building blocks for fabricating aerogel as solid amine adsorbents, via the fast gelatin between vermiculite and amine, significantly reducing the cost of adsorbent preparation while achieving promising CO2 capture capability. The effects of amine loading, amine molecular weight, and porosity on CO2 capture capacity and amine efficiency were investigated. It is found that the amine with larger molecular weights endows more stable amine anchoring in the composite aerogel, the aerogels using amine with higher molecular weights demonstrated higher residual amine ratios under vacuum conditions during the aerogel adsorbent synthesis, consequently enhancing the CO2 capture capacity of the adsorbents. By optimizing synthesis strategy and the amine loading of the composite aerogels, the highest CO2 capture capacity (0.72 mmol/g) and amine efficiency (0.29) were achieved. The monolithic structure of the aerogels ensures low pressure drop of 0.35 hPa during gas flow-through, enhancing their integration and applicability in adsorption devices. The vermiculite-based adsorbents exhibit unique advantages in practical DAC processes, including lower cost, higher amine efficiency, and stable cyclic performance. These findings hold significant promise for the application and advancement of DAC technologies.

Experimental and numerical studies of detailed heat transfer and flow characteristics in the rib turbulated annulus of a double pipe heat exchanger

An enhancement in the overall heat transfer between the fluids in a Double pipe heat exchanger (DPHE) can be achieved through various active or passive techniques. The present study focuses on the passive heat transfer enhancement in the annular region of a DPHE by incorporating circular ribs on the outer surface of the inner pipe. The primary objective is to investigate the influence of the ribs on the local distribution of heat transfer and fluid flow in the annulus of the heat exchanger. The local Nusselt number (Nu) distribution was determined experimentally using a test section specially designed with a provision to measure the wall temperature distribution of the inner pipe with an IR thermal imaging camera. The pressure drop across the channels with the ribs was also measured in the experimental studies. Numerical studies are employed to gain insights into the flow characteristics in the annular region in the presence of ribs. Studies comprise various rib diameters (e/Dh = 0.08, 0.14), rib-to-rib pitches (P/e = 6, 12, 18), and Reynolds number values (Re = 5000, 7500, and 10000). The heat transfer behaviour from the experimental study is discussed based on the flow mechanism observed using numerical techniques. The flow separation and reattachment due to the rib and the induced recirculation zone cause large variations in the Nusselt number distribution between the ribs. The peak Nusselt number value between adjacent ribs is observed at the location of reattachment of the flow to the ribbed wall. Acquired data also shows that the flow and heat transfer characteristics differ significantly with changes in the P/e ratio. The rib configuration with e/Dh = 0.14 and P/e = 12 is identified as optimal, achieving a balanced improvement in heat transfer while showing a relatively lower pressure drop.

A novel center-hybrid pin-fin microchannel heat sink with embedded secondary microchannels for hotspot thermal management

With the rapid advancement of microelectronics technology, the issue of excessive localized heat flux in electronic devices has become increasingly prominent. This study introduces a center-hybrid pin-fin microchannel heat sink (CHPFMHS) for hotspot thermal management, comprising a central hexagonal pin-fin region flanked by two lateral straight microchannel zones located at the inlet and outlet. Furthermore, four types of various secondary microchannels are integrated within the pin-fins of CHPFMHS (Case 1: with no secondary microchannel; Case 2–5: with 3-direction, 4-direction, 6-direction, and vertical intersecting secondary microchannels, respectively) for effective heat dissipation with low pressure drop. The performances of CHPFMHSs and non-hybrid straight microchannel heat sink (NHSMHS) are evaluated with Re = 50–400. For all flow rates, the pressure drops in Cases 2–5 are lower than that in Case 1, with Case 4 exhibiting the lowest pressure drop among all CHPFMHSs. The thermal resistance (Rth) and temperature non-uniformity (δT) of Case 5 with hotspot area (Ah) of 2.25 mm2 and pin-fin region length (Lrpf) of 3 mm are 47.3 % and 30.8 % lower than those of NHSMHS, respectively. Among Case 1–5, the configuration of Case 5 is the most optimal. The impacts of hotspot and the pin-fin region size of the CHPFMHS have also been investigated. As Ah rises to 6.25 mm2, in comparation with NHSMHS, Rth and δT of Case 5 decrease by 52.7 % and 40.2 %, respectively. As Lrpf rises, the values of both δT and Rth, for Case 5, approach their minimum when Lrpf is close to the length of the hotspot. However, they exhibit slight changes as Lrpf continues to increase.

Design of metal foam baffle to enhance the thermal-hydraulic performance of shell and tube heat exchanger

Solid baffles are widely used in shell and tube heat exchanger (STHX), while the highly increased flow resistance and dead zones remain serious drawbacks in the applications. To address this issue, metal foam baffle is proposed in this study to replace solid baffle. The numerical model with considering the thermal non-equilibrium between fluid and foam baffles was established. Laminar flow is assumed in the foam baffles region and the realizable k-ε turbulence model is assumed in the open region. Effects of porosity, pore density, thickness and number of foam baffle (N) on the performance were examined. Results show the foam baffles always lead to lower pressure drop of STHX compared to the solid baffles. Compared to five 2 mm thick solid baffles, five 6 mm thick metal baffles with the porosity of 0.80, 0.85 and 0.90 results higher outlet temperature at the pore density greater than 80, 120 and 160 PPI, respectively. The metal foam baffle leads to higher outlet water temperature compared with solid baffles at the baffle number N ≤ 7. The foam baffles with optimum pore parameters reduced the pressure drop by 12.9 % and increase the outlet and inlet temperature difference by 31.0 % compared to the solid baffles.

Construction of highly efficient flame retardant cellulose nanofibrils/bamboo activated charcoal based composite aerogel sheet for excellent PM2.5 removal

Developing biomass air filter materials with efficient filtration for particulate matter 2.5 (PM2.5) and low pressure drop is a great challenge. Targeting this issue, cellulose nanofibrils (CNF) were employed as the skeleton materials mixing with bamboo activated charcoal (BAC), polyethyleneimine (PEI), and ammonium polyphosphate (APP) as the functional fillers, followed by freeze-drying and hydrophobic modification to prepare CNF/BAC based composite aerogel sheet for capture for PM2.5. The resulting aerogel sheet showed good filtration efficiency for PM2.5 (98.64 %), which benefited from the three-dimensional network structure from CNFs and PEI and electrostatic adsorption of both BAC and APP with negative charge. After reusing for 5 times, the filtration efficiency of the system could still maintain at 95.88 %. In addition, the introduced both APP and PEI made the system have excellent flame retardant through the synergistic effect of nitrogen and phosphorus. In view of excellent properties and simple preparation, this work supplies a promising way to prepare multifunctional biomass air filter.

Polylactic acid-based composite filter with multi-gradient structure developed for high-efficiency particulate matter filtration and NH3 purification

Particulate matter (PM), ammonia (NH3) and other polluted gases emitted from animal feeding operations have emerged as significant risks to workers, surrounding residents, and the regional environment. Therefore, the development of air filters capable of simultaneously filtering PM and adsorbing toxic gases is particularly important. In this study, a three-layer gradient structure nanofiber filter was prepared by electrospinning technology, consisting of fluorinated Polylactic acid (PLA)/SiO2 as the outer layer, PLA nanofibers as the middle layer, and PLA/UiO-66-NH2 as the inner layer. This gradient structure of composite filter featured gradually decreasing pore sizes, exhibited optimal air filtration performance compared to PLA filter and commercial glass fiber filter. At 5.3 cm/s flow rate, the composite nanofiber filter achieved high filtration efficiency (99.15 % for PM0.5) and low pressure drop (89.65 Pa). Furthermore, the composite nanofiber filter exhibited highest dust holding capacity, indicating longer service life. It also featured excellent self-cleaning capabilities, allowing for reuse after simple water rinsing. Additionally, the results of ammonia (NH3) adsorption tests demonstrated the prepared composite filter’s highest adsorption capacity for NH3. Therefore, this work enhanced the application potential of high-performance air filters in the removal of PM pollution and hazardous gases.

Convection Heat Transfer and Performance Analysis of a Triply Periodic Minimal Surface (TPMS) for a Novel Heat Exchanger

Heat exchangers are necessary in most engineering systems that move thermal energy from a hot source to a colder location. The development of additive manufacturing technology facilitates the design and optimization of heat exchangers by introducing triply periodic minimal surface (TPMS) structures. TPMSs have shown excellent mechanical and thermal performance, which can improve heat energy transfer efficiency in heat exchangers. This current study intends to design and develop efficient, lightweight heat exchangers for aerospace and space applications. Using the TPMS structure, a porous construction encloses a horizontal tube that circulates heated fluid. Low-temperature water circulates inside a rectangular box that houses the complete system to remove heat from the horizontal pipe. Three porous structures, the gyroid, diamond, and FKS structures, were employed and examined. Porous models with various porosities and surface areas (15 cm2 and 24 cm2) were investigated. The results revealed that the gyroid structure exhibits the highest Nusselt number for heat removal (Nu max = 2250), confirming the highest heat transfer and lowest pressure drop among the three structures under investigation. The maximum Nusselt number obtained for the FKS structure is less than 1000, whereas, for the diamond structure, it is near 1250. A linear variation in the average Nusselt number as a function of the structure surface area was found for the FKS and diamond structures. In contrast, nonlinearity was observed in the gyroid structures.

Evaluation and selection of the best artificial lift method for optimal production using PIPESIM software

A well can be produced and exploited when it has production power, in other words, if the well does not have enough pressure, it will not be able to flow. Artificial production is a method to increase the lifespan of well production. The well studied in this article has a significant annual lower pressure drop; So now with the current pressure of the existing well, it is not possible to send the oil of this well to the separator of the first stage of the exploitation unit. Among the existing solutions to maintain or increase production and increase the flow pressure of the well, is the use of artificial extraction. In this article, an attempt has been made to simulate the effect of using a core pipe, gas pumping and installing an electric submersible pump (ESP) on the production flow rate and flow pressure of the well by using the well data and the static and current pressure test. The current production data with the PIPESIM software was checked, and then the best extraction method for the studied well. Finally, the installation of an ESP was determined and selected as the best method of artificial extraction.

Slot-structured catalytic membrane for sustained oily particulate matter removal with a low pressure drop

Oily particulate matter (PM) filtration faces the problems of high pressure drop and difficult regeneration. Herein, vertical arrays of MnO2 nanosheets was assembled on Zr doped TiO2 (Zr-TiO2) nanofibers to construct a core–shell structure MnO2@Zr-TiO2 (CSMT-x) catalytic membranes for highly efficient oily PM filtration and decomposition. The confining effect of the ultrathin MnO2 nanosheets enhances PM capture efficiency, and the increase of effective contact area between MnO2 and oily PM accelerate the decomposition of oily PM. The optimized CSMT-3 catalytic membrane exhibited high gas permeability and redox capacity, outperforming the Zr-TiO2 (Bare T) membrane with over 99.97 % PM filtration efficiency and a low pressure drop at the temperatures of 25–425 °C. The catalytic decomposition of PM prevented the accumulation of particles on the membrane surface, which inhibited the formation of cake layer. Therefore, the CSMT-3 membrane exhibited a slight increase in pressure drop (less than 120 Pa) even after 120 h long-term filtration. This work may contribute to the development of advanced multifunctional membranes for purification of oily PM.

Large-Eddy Simulation Study of Flow and Combustion Dynamics in a Full-Scale Hydrogen-Air Rotating Detonation Combustor-Stator Integrated System

Abstract A first-of-its-kind large-eddy simulation (LES) study is conducted to numerically investigate the combustion dynamics as well as aero-thermal phenomena in a full-scale non-premixed hydrogen-air rotating detonation engine (RDE) integrated with nozzle guide vanes (NGV) acting as the turbine stator. The LES framework incorporates hydrogen-air detailed chemical kinetics and adaptive mesh refinement. A comparative analysis is carried out for two operating conditions with different fuel/air mass flow rates but global equivalence ratio of unity. The LES model is validated against experimental data with respect to detonation wave speed/height, wave dynamics, and axial static pressure distribution. Numerical results indicate significant deflagrative combustion occurring in the fill region near the inner wall due to formation of recirculation zones in the injection near-field driven by the backward facing step. The leading detonation wave is found to be trailed by an azimuthal reflected-shock combustion wave, which consumes unburned vitiated reactants that leak through the main detonation wave. The detonation wave characteristics do not change appreciably with the presence of NGV. The exit flow is found to be nearly fully subsonic and supersonic for the low and high mass flux conditions, respectively. The presence of NGV renders the flow more axial, and significantly impacts the exit Mach number and total pressure. The low mass flux operating point, despite exhibiting more deflagrative losses within the combustor, yields overall lower pressure drop from plenum to exhaust, mainly attributed to lower pressure drop across the injectors.