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• The heat transfer characteristics was investigated that are exhibited with the occurrence of misalignment at flat and profiled endwall using naphthalene sublimation method. • The occurrence of misalignment in the flat endwall significantly increases the thermal load in the region upstream of the endwall. • There was no significant difference in heat transfer when a misalignment occurred in the profiled endwall. • A profiled endwall had a lower thermal load than a flat endwall, and is a robust design because the thermal load changes less even if misalignment occurred. Misalignment of gas turbine engines is caused by the difference in thermal expansion from the design point when starting or stopping the engine, or when operating at partial load. This study evaluated the differences in heat transfer characteristics between a flat endwall and a profiled endwall with misalignment. To ensure consistency with the flow conditions, experiments were conducted at an outlet Reynolds number of 300,000 for both geometries. The experiment was performed under three different conditions: a case without step, a case with a forward-facing step (h / C x = -0.1), and a case with a backward-facing step (h / C x = 0.1). In the flat endwall, the thermal load of the upstream region increases significantly with both step circumstances compared to the case without a step. The misalignment causes a recirculation flow to occur between the interface of the combustor and turbine. This leads to the mainstream reattaching upstream of the endwall. Nevertheless, the heat transfer characteristics of the profiled endwall differ from those of the flat endwall under step conditions. Most locations do not experience significant changes, with only a slight increase observed in the upstream region. The recirculation flow is crucially reduced due to the intensity of the secondary vortex in the profiled shape. Hence, the increase in the thermal load on the profiled endwall with step is considerably lower than that on the flat endwall. As a result, the thermal load on the profiled endwall has decreased by 25 % for the forward-facing step and 20.7 % for the backward-facing step compared to the flat endwall. [ABSTRACT FROM AUTHOR]

Airborne particulate matter (PM) causes hazardous problems in human health, and water droplets have been utilized for PM removal in the air. However, since conventional wet scrubbing techniques mostly rely on mechanically generated water droplets, they have intrinsically limited in collection efficiencies of a single droplet. In addition, PM capturing strategies for removal of fine PM need to be established to enhance PM removal performance based on flow dynamics. Here, we propose a steam flow of water droplets generated by a photothermal membrane for air purification. The generated flow captures PM efficiently by the aid of the coupled effects of water droplets and hydrodynamic flow. The flow achieves high and sustainable deposition constants of 0.458 and 0.472 h−1 for PM 1.0 and PM 2.5 within 1 h at 4 solar intensity, which is 2.20 and 2.24 times higher than those of without solar irradiation, respectively. The deposition constants of PM using steam flow were higher than that of previous wet scrubbing methods despite a low volume of water usage. Our photothermal-driven flow with water droplets could be utilized as effective indoor air purification system that is low cost, energy-efficient, and environmentally-friendly. [Display omitted] • The solar-driven steam flow with droplets has been a helpful approach to capturing PM. • The system can be an efficient and sustainable option to remove PM over typical ones. • Water evaporation and PM removal are enhanced by increasing solar intensity. • The proposed system can be utilized indoors and outdoors under various light sources. [ABSTRACT FROM AUTHOR]

The drag reduction of commercial vehicles is the principal challenge to improving fuel saving and decreasing air pollution. Accordingly, several flow control devices, including gap fairing, cab roof fairing, boat tail, and side skirt were introduced to reduce the aerodynamic drag exerted on heavy vehicles. Although such devices have exhibited good drag reduction performance, their aerodynamic performance can be improved further. Moreover, a comprehensive and systematic research is required, including drag force measurement, flow field analysis and real-scale proving ground test, to evaluate the fuel consumption of heavy vehicles. In this study, the drag reduction effect of the aero full package (AFP) of a tractor–trailer, which integrated gap fairing, flap-type side skirt and lower inclined air deflector boat tail, was investigated through wind tunnel experiments and proving ground test. On the basis of the results of drag and PIV measurement, the integrated AFP was found to significantly modify the flow structure around the vehicle, thereby leading to a 26.5% reduction in drag coefficient compared with the reference tractor-trailer model (C D = 0.693). Furthermore, the proving ground test using real tractor–trailer verified that the integrated AFP provides 13.4% fuel saving. The present results will provide practical information for improving the aerodynamic performance and fuel efficiency of heavy vehicles. • The aero full package for tractor-trailer consist of gap fairing, flap-type side skirt and LIAD boat tail was newly proposed. • The aero full package reduces drag coefficient up to 26.5% compared with reference tractor-trailer. • The flow structures around tractor-trailer model is revealed through PIV experiments. • Real-scale proving ground test confirmed 13.4% fuel saving with the aero full package. [ABSTRACT FROM AUTHOR]

Aerodynamic drag reduction of heavy vehicles is one of the main issues in fuel saving and environmental gas emission. In general, 50% of the total aerodynamic drag is induced from the region in the front surface of the vehicle and the gap between the tractor and trailer. Various forebody drag-reducing devices for tractor–trailer vehicles were introduced, however, conventional gap fairings or side extenders have technical limitations in reducing the aerodynamic drag exerting on the cab-roof space and gap between the tractor and trailer effectively. In this study, wind tunnel tests were conducted to investigate the drag reduction effects of the newly proposed gap fairings. The proposed gap fairing reduced drag by 16.4% at maximum as well as changed the gap length and deflecting angle. The aero cab fairing (ACF), which is a combination of cab-roof and gap fairings, and the extended aero cab fairing (EACF) considerably reduced the drag coefficient by approximately 11.1% and 17.5%, respectively. A particle image velocimetry was used to investigate flow characteristics, such as spatial distributions of mean velocity, vorticity, and turbulent kinetic energy around the scaled-down tractor–trailer model (1:17) with and without gap fairings to analyze the drag-reduction mechanism of the proposed gap fairings. The proposed gap fairings including ACF and EACF significantly reduced the mean velocity, vorticity in the gap region between the tractor and trailer, and the turbulent kinetic energy on the trailer's front surface. Results can provide useful information for improving the design of new additive flow control devices in reducing the aerodynamic drag of heavy vehicles. [ABSTRACT FROM AUTHOR]

The efficiency of the gas turbine engine has been enhanced by improving aerodynamic performance and reducing heat load through control of secondary vortices according to the first-stage vane endwall configurations. In this study, the heat transfer features of flat and profiled endwalls were investigated under different turbulence intensities. Experiments were conducted under a fixed turbine-vane exit Reynolds number of 300,000 and Mach number of 0.15 on both geometries. The test specimen was scaled up 3.23 times based on the actual gas turbine vane geometry. The profiled endwall configuration was optimized considering the combustor outlet/exit geometry. Five control points were set for the vane geometry, and the minimum aerodynamic loss at the vane exit plane was determined as an objective function. As the turbulence intensity is increased, the heat transfer is increased on both endwall geometries. However, the intensity of the horseshoe vortex was significantly reduced with the profiled endwall compared with the flat endwall. Consequently, the area-averaged Sherwood number on the profiled endwall was about 25.8% (under the low turbulence intensity) and 19% (under the high turbulence intensity) lower than those of a flat endwall case, respectively. [ABSTRACT FROM AUTHOR]

The tip leakage flow between rotating turbine blades and the stationary turbine casing causes aerodynamic losses and high thermal loads. Numerous novel tip geometries have been proposed for reducing both of these effects, one of them is a shelf squealer tip. The objective of this study is to investigate the aerothermal performance of three squealer blade tip configurations: conventional, vertical shelf and inclined shelf. Heat transfer was measured to analyze heat transfer features on the blade tip using transient IR thermography method. Also, computational fluid dynamics simulation and particle image velocimetry were conducted to visualize the flow characteristics around the blade tip. The experiment was conducted under conditions of a Reynolds number of 140,000 which was based on the inlet velocity in a wind tunnel. Thermal loads with vertical and inclined shelf squealer tip configurations are lower than with the conventional squealer tip. Due to the recessed pressure side rim of the vertical shelf squealer tip, the tip leakage flow was less reattached comparing to conventional squealer tips. This resulted in reduced thermal load on the tip surface and a larger tip leakage vortex around the blade suction side, which increased aerodynamic losses. Especially in the inclined shelf squealer tip, a separation bubble was generated on its inclined pressure side rim, which reduced the tip leakage flow due to the vena contracta effect. Consequentially, the reduced tip leakage flow decreased both heat loads and aerodynamic losses for the inclined shelf squealer tip. Therefore, the inclined shelf squealer tip demonstrated a good performance with respect to both aerodynamic loss and heat transfer. [ABSTRACT FROM AUTHOR]

• Investigation of heat transfer characteristics on the 2nd vane endwall when the misalignment occurs without and with purge flow using Naphthalene sublimation method and CFD. • Significant increase in heat transfer coefficient in the upstream of vane endwall due to misalignment. • With purge flow, the mixing of mainstream and purge flow increases heat transfer in the upstream of vane endwall due to increase the intensity of vortex. • The area-averaged heat transfer of the stepped endwall is increased by about 11.4% and 13.7% without and with purge flow, respectively, as compared to that of the flat endwall. Since the domestic power plants are typically operated at a partial load rather than the design point, the thermal expansion decreases, resulting in misalignment between first stage rotor and second stage stator. In this study, we investigate the heat transfer characteristics of a misalignment under purge flow at the second stage vane endwall through heat/mass transfer experiments using the naphthalene sublimation method and CFD simulations. Experiments are conducted at 4 vanes in a linear cascade with an inlet Reynolds number of 120,000, based on the vane axial chord length. In the absence of purge flow, a high heat transfer occurs in upstream of the vane endwall via horseshoe vortices. When a misalignment occurs, a more severe thermal load is observed as the mainstream attaches to the endwall due to recirculation flow upstream of the leading edge. Additionally, two high heat transfer regions are observed when a step-induced vortex occurs in the vane flow path. In case of the purge flow, the mixing of the mainstream and purge flow increases the intensity of the vortex, which increases heat transfer in the region upstream of the both flat and stepped endwall. In conclusion, we have found that the step difference has a crucial effect on thermal damage upstream of the second stage vane endwall as a little misalignment occurrence. The area-averaged heat transfer of the stepped endwall is increased by about 11.4% and 13.7% without and with purge flow, respectively, as compared to that of the flat endwall. [ABSTRACT FROM AUTHOR]

Solar steam generation is a promising technology for harvesting solar energy to purify seawater and wastewater. State-of-the-art technologies have struggled to achieve sufficient solar evaporation rate and antifouling property simultaneously. In addition, the antifouling strategies based on flow dynamics need to be established to develop more efficient membrane designs. Here we propose a new superhydrophilic thermally-insulated macroporous membrane (STIMM) composed of carbonized sucrose and polydimethylsiloxane as an efficient solar evaporator. The converted solar energy is fully utilized for evaporation by the aid of the coupled effects of superhydrophilicity and heat localization. STIMM achieves a high evaporation rate of 2.045 kg/m2/h even at its macropore size under 1 sun irradiation, overcoming the previous trend limit. The macropores of STIMM enable self-cleaning with a 93.1% salt rejection rate. The high evaporation rate and geometrical traits of STIMM generate strong convective flows to dynamically reject salt. The solar desalination system based on STIMM stably produces a practically high amount of purified water with a production rate of 24.9–30.6 L/m2/day. Our proposed STIMM demonstrates a new paradigm for facile desalination systems that are low cost, energy efficient, and self-cleaning under natural environmental condition. Image 1 • 3D bilayer macroporous membrane is developed for efficient and sustainable solar steam generation. • Superhydrophilicity of the membrane compensates for the evaporation limit at large pore sizes. • Macropores of the membrane promote sedimentation of precipitated salt crystals for sustainable seawater desalination. • High evaporation rate and geometrical traits of STIMM generate strong convective flows for dynamic salt rejection. [ABSTRACT FROM AUTHOR]

Airborne particulate matter (PM) has emerged as an important global environmental and social issue due to its harmful health effects. Various techniques have been introduced to remove indoor PM. However, an effective and sustainable method has not been established yet because of complex mechanisms and various factors. Here, we propose the use of water microdroplets generated by a MHz-frequency ultrasound, and experimentally examine the effects of the generated microdroplets on PM removal. The PM removal efficiency and PM deposition constant are analyzed by measuring the temporal variation of PM concentration. The measured experimental results are compared with analytical deposition constants. Two collection efficiencies derived in previous studies are employed to substitute a mathematical model used for determining the analytical deposition constants. In addition, the mean diameter and the moving velocity of the microdroplets are experimentally measured via a digital holographic microscopy and particle image velocimetry generated by a MHz-frequency atomizer. The present results demonstrate that water microdroplets generated by the atomizer can be effectively used to remove PM. Image 1 • PM 10 and PM 2.5 removal efficiency increases by using water microdroplets. • Collection efficiencies noticeably increase compared with previous studies. • PIV and DHM are utilized to verify flow velocity and mean diameter of water droplets. • Experimental and analytical PM deposition constants are quantitatively compared. [ABSTRACT FROM AUTHOR]

The increasing demand of lithium (Li) receives great attention to the development of efficient Li recovery techniques. In this study, a novel strategy is proposed to separate Li+ ions from concentrated seawater by using the synergetic effect of Al3+–crosslinked alginate (Alg) and hydrogen manganese oxide (HMnO). The crosslinked Al3+ in the Alg network structure generates a strong repulsive force to salt cations. This environment probably increases the contact opportunity for Li+ ions with a low adsorption affinity to HMnO by rejecting other salt cations with a high adsorption affinity. Adsorption capability and selectivity of the fabricated HMnO-incorporated Alg (HMnO/Alg(Al)) composite greatly increase compared with those of normal Alg composites. As a proof of concept application, the selectivity separation factors α Me Li of HMnO/Alg(Al) composite from concentrated seawater are evaluated as 36.36 and 40.08 for α Na Li and α K Li , respectively, at the first repetition. However, these factors decrease after the second repetition because of structural instability. The proposed Li recovery technique would be utilized as an efficient alternative to state-of-the-art Li separation methods based on the ion-intercalation mechanism and would pave the way for the efficient recovery of Li from concentrated seawater. • HMnO powders are immobilized in Al3+–crosslinked alginate composite. • Strong repulsive force of Al3+–Alg network allows selective infiltration of Li+. • The incorporation of HMnO in Al3+–Alg networks enhances Li adsorption efficiency. [ABSTRACT FROM AUTHOR]

In a turbine passage, the wake, which affects the heat transfer of a turbine blade, occurs periodically due to rotation of the blade. We analyzed the effect of wake on the endwall of the turbine blade according to the relative position of the turbine blade and the vane in a stationary condition. The naphthalene sublimation method was used to measure the heat transfer and detached eddy simulation (DES) was used to analyze flow characteristics. The wake from the vane was simulated by using a cylindrical rod upstream of the blade. The cylindrical rod was placed in four which positions that were aligned leading edge-to‑leading edge. The pressure and Q criterion distributions varied according to the position of the upstream wake. As the position of the upstream wake changed, the point at which the passage vortex and wake met varied. Wake and passage vortex met at x / C x  = 0.2 in position 1 and at x / C x  = 0.55 in position 2. After the wake and passage vortex had met, the secondary flow scattered. Therefore, the local and averaged heat transfer varied due to flow characteristics. Thus designers of film cooling holes on endwalls should consider these effects to ensure appropriate cooling performance. [ABSTRACT FROM AUTHOR]

• Effect of anisotropic wicking plays an important role on subcooled flow boiling. • Significant enhancement in critical heat flux and heat transfer coefficient in presence of anisotropic wicking surfaces. • Wicking characteristic enhancement in the presence of surfaces with bent-polymerized pillar arrays. Anisotropic wicking surfaces have attracted the attention of numerous research groups in recent years. Wicking characteristics can be improved by generating unidirectional flow behavior within surfaces composed of micropillars that are bent in the direction of interest. In the present work, we created surfaces composed of bent polymerized pillar arrays with center-to-center spacings of 250 and 500 µm and experimentally investigated boiling heat transfer under subcooled flow conditions (40 K). The test surfaces were chemically coated with a 200-nm-thick hydrophilic layer to evaluate the effects thereof on subcooled flow boiling. Surface anisotropy and the center-to center spacings between neighboring pillars significantly improved surface wickability and boiling heat transfer, compared to surfaces with vertically polymerized pillars. Enhancements of the critical heat flux (17–34%) and the heat transfer coefficient (8–71%) were evident on polymerized pillar surfaces compared to bare polymerized surfaces. The experimental results were validated by theoretically analyzing the relationship between the liquid pinning forces and the polymerized pillar surfaces' configurations to understand better how boiling heat transfer was enhanced on anisotropic wicking surfaces during subcooled flow boiling. [ABSTRACT FROM AUTHOR]

• Developmental morphological effects of PM 2.5 were explored in zebrafish embryos. • Most embryos exposed to PM 2.5 exhibited hatching delays and mortality. • PM 2.5 caused pericardial edema and string heartbeats through blood circulation failure. • PM 2.5 caused apoptosis, disruption of the vascular system and liver, and inhibited motor neurons. • PM 2.5 disturbed the cellular and subcellular organelles in developing zebrafish. Contemporary research in epidemiology has found that being exposed to air pollution at an early stage of life has associations with both acute and chronic conditions of the multi-organs. Nevertheless, the reasons for this have yet to be fully explained. Because of this there is a need for a robust investigation into the damaging toxic influence of diesel particulate matter (PM 2.5) on living organisms. This study is aimed to investigate the developmental toxicity of PM 2.5 by using zebrafish (Danio rerio) embryo/larvae as a disease model and to understand the toxicity effects of PM 2.5 on ecological environment more thoroughly. This research demonstrates that being exposed to PM 2.5 leads to a significant increase in mortality, effective developmental morphology, reductions in hatching rates and lower heart rates in zebrafish. Additionally, it leads to increases in the length of string heart, area of pericardium, and apoptosis, reduces the number of normal intersegmental vessels (ISVs) and motor neurons in the trunk region and liver formation defects in zebrafish embryos. Investigation employing a scanning electron microscope demonstrates that being exposed to PM 2.5 leads to damage in zebrafish larvae skin cell layers. Histological analysis demonstrates that when these larvae are treated with PM 2.5 then abnormalities occur in the neurons, liver, heart, gills, brain, and eyes, and remarkable increase in in the cellular/subcellular levels of organelle dissolution. These findings are useful to help us understand the pathophysiological influence of being exposed to PM 2.5 on the multi-organ defects of zebrafish. More research into which particular elements that make up diesel pollution contribute to this toxicity is needed so that the dangers to development can be further analysed. [ABSTRACT FROM AUTHOR]