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Three different kinds of coolant chamber configuration for film cooling are proposed to develop the swirling coolant flow at blowing ratios ranging from 0.5 to 2.0. The results show that the difference of film cooling effectiveness for three kinds of coolant chamber configuration is little at low blowing ratio, but the advantage of swirling film cooling becomes obviously with the increase of blowing ratio. When the blowing ratio is 2.0, the jet momentum of original coolant chamber configuration is large and uniform, which leads to the lowest cooling effectiveness due to the formation of a strong kidney vortex. The first coolant chamber configuration has a low jet momentum region at upstream of the film hole, the coolant in this region interacts with high temperature mainstream and bypasses the large jet momentum coolant to attach cooling surface at downstream. The second coolant chamber configuration is sprayed with the structure of unidirectional vortex, which forms a vortex pressing on other vortex, making the coolant in pressed vortex attach surface better, producing the best coverage and the higher film cooling effectiveness. [ABSTRACT FROM AUTHOR]

The oxidation behaviour of a low-alloy steel T22 was investigated by exposure to ordinary pressure steam (0.1 MPa), high-pressure superheated steam (8 MPa), and supercritical water (SCW) (25 MPa) at 600 °C for 1000 h. The results show the exposure pressure has a significant influence on weight gains and oxide scale morphologies. All the samples approximately obey near-parabolic oxidation kinetics. Some pores are found on the samples exposed to steam while severe cracks are formed in SCW. Further, the influence of steam pressure on the oxidation process is discussed in detail. [ABSTRACT FROM PUBLISHER]

The low cost graphite/carbon black counter electrodes were prepared under low-temperature for hole-conductor-free mesoscopic perovskite solar cells. Different mass fraction of carbon black particles in the interspace of graphite flakes not only modulates the connection of carbon black and graphite flakes, but also guarantees the good contact between the counter electrode and perovskite layer, which obviously improves the charge transport properties of the cells. The electrochemical impedance spectra and incident photon-to-current conversion efficiency study show evidences of it. Based on the optimized low-temperature carbon electrode (LTCE) with a thickness of 5 μm, power conversion efficiency about 7.29% and good stability are achieved for the hole-conductor-free mesoscopic perovskite solar cells. The abundant availability and excellent properties of such carbon materials based LTCEs offer a wide prospect for its further applications in perovskite solar cells. [ABSTRACT FROM AUTHOR]

Summary: Modular high‐temperature gas‐cooled reactor power station (MHTGR) is the most promising configurations for fourth‐generation nuclear technology. Aiming at the low accuracy of the performance prediction of MHTGR compressor, the paper intends to provide an experimental basis to have deep comprehension about the nexus of loss, passage structure and working conditions, including surface flow visualization, five‐hole probe measurement at the outlet section and surface pressure measurements under different conditions (blade camber angle, incidence angle). The experimentally measured data and images give a deep insight into the influence of blade camber and incidence on the flow structure, loss and blade loading. The vortex system is mainly shaped by the action of the pressure field. When the flow turning angle is large, the effect of the working fluid properties may be inconspicuous on the overall loss of the flow, rather than the tremendous impact on the boundary layer friction loss of attached flow as in the small blade chamber angle passage. For different vortices, the effect of each factor, which may cause losses, is also wax and wane. [ABSTRACT FROM AUTHOR]

The crack growth rate (CGR) tests of austenitic steel TP347HFG were conducted under <10‐8000 ppb dissolved oxygen (DO) in steam, the alternating environment of air and steam and supercritical water (SCW) at 600–650 °C. A constant stress intensity factor (K) method and direct current potential drop technique were used in the tests to evaluate its environmentally assisted cracking (EAC) properties as superheater and reheater boiler tubes in ultra‐supercritical power plants. CGR increases monotonically with temperature and DO content. CGR in SCW is greater than that in the high‐temperature steam which indicates that exposure pressure has an obvious effect on crack propagation. The varying CGR in different experimental environments show that exposure medium participates in the cracking process. Fracture surface and cross‐sectional surface of compact tension specimen were analyzed by scanning electron microscope. The mechanism of crack propagation in different exposure environment is further discussed. [ABSTRACT FROM AUTHOR]

Oxidation tests were conducted on austenitic steel exposed to deaerated supercritical water at 600–700 °C and 25 MPa. The oxidation kinetics followed between a linear law and a parabolic law at 600–650 °C while followed a near-parabolic law at 700 °C. A double oxide layer, which consists of a Fe-rich outer layer and a Cr-rich inner layer, was formed on the steel. The outer layer consists of Fe 3 O 4 at 600–620 °C for 1000 h and at 650–700 °C for 400 h, while the inner layer consists of spinel in all cases. Fe 2 O 3 is formed at 650 °C for 1000 h and at 700 °C for 600 h. Exfoliations were observed at 700 °C. The formation and spallation mechanism of oxides are also discussed. [ABSTRACT FROM AUTHOR]

Jet impingement cooling is usually used in zones with extremely high thermal loads. The major factor that limits impingement heat transfer uniformity is the crossflow. The impingement cooling with return hole is applied to reduce the negative effect of crossflow on the target surface heat transfer in present paper. The influences of jet-to-plate spacing (H / D), impingement target surface curvature (α), temperature ratio (TR) and Reynolds number on flow field and heat transfer performance are investigated in detail. The results indicate that the correlation between the overall area average Nusselt number of target surface and H / D , the overall area average Nusselt number decreases by approximately 5.76% with H / D increases by one unit. Increasing the impingement target surface curvature is beneficial to expand the spanwise heat transfer. The overall area average Nusselt number increases by 295.5% for Reynolds number varying from 10,000 to 50,000 at TR = 0.910, and the overall area average Nusselt number increases by 8.68% for the TR varying from 0.668 to 0.910 at Re = 30,000. The results indicate that impingement cooling with return hole can achieve high heat transfer coefficient and uniform heat transfer distribution. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO 2 ) with dispersed W-doping shows its capability for efficient electron collection from perovskite to TiO 2 in perovskite solar cell. The conduction band (CB) of TiO 2 moves downward (positive shift) with increasing the tungsten (W) content, which enlarges the energy gap between the CB of TiO 2 and the perovskite. Thus, the efficiency of electron injection from perovskite to TiO 2 is increased. Due to the increased electron injection, W-doped TiO 2 (≤0.2% W content) enhances the short-circuit photocurrent (J sc ) of perovskite solar cell and improves the performance of perovskite solar cell. Perovskite solar cell with 0.1% W-doped photoanode obtains the highest power conversion efficiency (η = 10.6%), which shows enhancement by 13% in J sc and by 17% in η, as compared with the undoped TiO 2 perovskite solar cell. [ABSTRACT FROM AUTHOR]

A comparative study of the flow field and heat transfer characteristics between swirl and impingement of mist/air cooling on blade leading edge is carried out to find a better cooling configuration for phase transition cooling. The Eulerian–Lagrangian particle tracking technique is used to investigate mist/air cooling. Comparisons are made between these two cooling forms in such aspects as vortex structure, heat transfer enhancement, pressure loss, and thermal uniformity with and without mist injection. The influences of mist ratio and Reynolds numbers on these parameters are studied in this paper. Results show that heat transfer is enhanced while pressure loss and thermal uniformity are improved by the swirl flow created by vortex impingement. The heat transfer performance increases by about 46.2 and 51.9%, respectively, for impingement and swirl cooling with 8% mist injection, and the pressure loss coefficient increases by 19%. The difference of heat transfer coefficient between swirl and impingement cooling with and without mist injection at high Reynolds number is larger than that at low Reynolds number. In addition, the heat transfer nonuniform coefficient of swirl cooling is about 15% lower than for impingement cooling. [ABSTRACT FROM PUBLISHER]

An in-fiber integrated fluorescence online optofluidic sensor is realized in a hollow optical fiber with a suspended core. A micro-region for fluorescence quenching reaction is built in the hollow optical fiber. By etching microholes on the surface of the fiber, the fluorescence reagents can be injected into the optical fiber and form microflows in the region. Simultaneously, indicator molecules can be excitated through the evanescent field of the suspended core and the fluorescence is efficiently coupled into the core and can be detected. In this report, the concentration of nitrite can be determined by quenching the fluorescence of rhodamine 6G during optofluidic reaction in the optical fiber. Furthermore, the results demonstrate the feasibility of the integrated in-fiber optofluidic method for trace fluorescence detection. [ABSTRACT FROM AUTHOR]

• Applicability of fluid dynamics theory to helium is demonstrated. • Flow characteristics with Reynolds number of helium boundary layer are performed. • Effect of FST on transitional helium boundary are investigated. • Similarities and differences between the helium and air boundary layers are researched. This paper investigates the fundamental flow behaviors of helium, aiming at supporting the helium turbomachinery design optimization in generation Ⅳ nuclear power station. The applicability of hydrodynamics theory to helium has been discussed from many aspects including continuous medium, Newtonian fluid, Stokes hypotheses, and perfect gas state. The Reynolds average N-S method (RANS) with the γ-θ transition model is used for solving the compressible helium boundary layer. The influence of the Reynolds number on the helium boundary layer transition is explored. With the increasing Reynolds number, the transition of boundary layer occurs in advance on the plate. On the other side, the boundary layers under different Reynolds numbers have uniformity in the comparison of dimensionless parameters. The free stream turbulence (FST) is a main influence factor on the transition. Both the enhanced turbulence intensity and the large turbulence scale can make the transition be triggered in advance and reduce the onset Reynolds number. For the fluids with different specific heat ratios, the helium transition lags behind the air under the same Mach number. When under the same Reynolds number, the helium boundary layer is identical to the air. They share the same mean velocity profile and agree with the theory solution and experimental data simultaneously. [ABSTRACT FROM AUTHOR]

The aerodynamic, heat transfer and film cooling characteristics of three tip configurations (including pressure-side partial squealer tip, suction-side partial squealer tip and cavity squealers tip) with cooling are evaluated on transonic turbine, and the effect of the jet and shroud motion are talked. The flow and heat transfer mechanisms of three cooled tip configurations are analyzed. Results show that both the jet and shroud motion alter the tip gap flow, which is found to have a different impact on the aerothermal and film cooling performances of three tip configurations. The addition of cooling significantly increases the overall heat transfer coefficient of the SS tip, but has a relatively small impact on that of the PS tip and Squealers tip. As a result, the total h ¯ of SS cooled tip is even increased by 9.0% compared to Squealers cooled tip. The shroud motion increases the film cooling effectiveness of PS cooled tip and Squealers cooled tip, but reduces that of SS cooled tip. Under the moving shroud condition, Squealers cooled tip have significant advantages in aerodynamic, heat transfer and film cooling performances compared to the other two cooled tip structures. [ABSTRACT FROM AUTHOR]

• Accurate He-Xe properties calculation program is established. • Boundary layer is applied to explore the effect of fluids properties on flow loss. • A flow criteria set is specified for noble gas and air flow similarity. • Similarity criteria are verified by the flow field and efficiency of radial turbine. The performance of radial turbines with the He-Xe mixtures, helium, argon and air are examined in this paper. The published approach pertaining to Chapman-Enskog kinetic theory and corresponding states theory is adopted to calculate the transport properties of He-Xe mixtures with two different molecular weights of 15.9 g/mol and 40 g/mol. The independent or combined effects of the flow Euler number (Eu), Reynolds number (Re) and inflow velocity on flow similarity are discussed based on flat-plate flow. Under the consistent above conditions, the flows of these fluids are similar and the flow loss is merely a function of fluids properties. The established flow similarity conditions form a procedure to calculate the boundary conditions of similar turbines and its application makes the flow similar in radial turbines passages. It is reflected in the consistent topology skeleton of flow structures and the identical parameter distributions in the flow section. The turbines with He-Xe mixtures, Ar and air shares a pretty similar tendency of efficiency line and the values differ little. The differences between these turbines under the same working point have an upper limit of 0.3% before critical state. At the design point, a similar velocity triangle instead of an identical one can guarantee the flow similarity and an approximate efficiency compared with others. Once the working condition deviates from the design point, the efficiency error between the helium and other fluids widens as the working condition deviation increases. [ABSTRACT FROM AUTHOR]

Trailing edge mixing flows associated with coolant injection are complex, in particular at transonic flows, and result in significant aerodynamics losses. A series of tests and calculations on a high-pressure turbine vane cascade with trailing edge injection were conducted to investigate the influence of trailing edge injection on the loss characteristics of the transonic profile. Wake traverses with a five-hole probe and measurements of the pressure distribution on the profile were taken for injection mass flow ratios of 0 and 4.1% under a test Mach number of 0.7. In the meantime, two-dimensional numerical predictions were carried out for exit isentropic Mach numbers of 0.7, 0.85 and 1.1 and injection mass flow ratios of 0, 4.1%, 4.7% and 5.2%. Numerical predictions show a reasonable agreement with the experimental data, and wake total pressure losses and flow angles as well as pressure distributions on the profile were compared to calculations without trailing edge injection, showing a significant effect of trailing edge injection on the wake development and its blockage effect on the flow in the vane cascade passage. The outlet total pressure loss and flow angle are increased with increasing exit Mach number. The trailing edge injection of 4.1% increases the static pressure in the rear part of vane suction side, and then reduces the vane loading, thus causing decreased wake losses at different exit Mach numbers. At transonic flows, the injection also reduces the strength of the shock wave at the trailing edge pressure side. In addition, the injection decreases the outlet pressure circumferential-unevenness at an exit isentropic Mach number of 0.7, while it increases the pressure circumferential-unevenness at higher exit Mach numbers. [ABSTRACT FROM AUTHOR]

To assess the role of dissolved oxygen in supercritical water on the growth processes of oxide scales, a marker experiment of ferritic–martensitic steel was performed by exposing to supercritical water (H 2 16 O) containing marked 18 O 2 at 600 °C under 25 MPa. The oxide scale was analysed by using Secondary Ion Mass Spectrometry (SIMS). The oxygen isotope profile shows that dissolved oxygen and supercritical water react with metals simultaneously. Dissolved oxygen changes the oxidation/reduction potential of supercritical water leading to an increase in the oxidation rate. The oxidation rate increases with increase in dissolved oxygen content in supercritical water. The mechanism of the effect of dissolved oxygen on oxidation is discussed. [ABSTRACT FROM AUTHOR]

Perovskite solar cells as a hot research topic show the necessity of controlling the interface. In this work, an insulating alkyl chain layer is self-assembled at the perovskite/hole transport material interface, which successfully exhibits a dual function: blocking electron recombination and resisting moisture at the same time. Improved solar energy conversion efficiency and stability of the device are both achieved. [ABSTRACT FROM AUTHOR]

Numerical simulation is performed to explore leading film cooling enhancement by the application of injecting water mist into the air. The accuracy of numerical simulation program for conjugate heat transfer methodology is verified with the C3X gas turbine vanes cooled with leading edge films. The effect of various parameters including mist concentration, mist diameter, different particle wall interactions conditions, and different forces on the improvement of cooling performance is investigated in this paper. It indicates that mist film cooling can decrease the temperature of boundary layer without impact on the temperature of the mainstream and the thickness of boundary layer. [ABSTRACT FROM PUBLISHER]

In the turbine passage, the secondary flow makes the film cooling jets driven from the pressure side to the suction side, resulting in the corner region of the pressure surface is difficult to cool. In this paper, end-wall film cooling performance and aerothermal performance with the three cases, which include the cylindrical cooling scheme, the swirling cooling scheme and the compound cooling scheme, at different axial positions of the turbine passage are studied respectively. Results show that significant improving the cooling performance for the swirling case at corner region of pressure surface is found. Furthermore, its overall adiabatic averaged cooling effectiveness at different axial positions are all increased. Compared with the compound and cylindrical cases, the swirling cooling effectiveness of the first row is increased by 77.4% and 63%, respectively, at M = 2.2. The physical mechanism of the improvement end-wall cooling performance is that the pair anti-vortex produced by the swirling coolant are twisted and squeezed each other, which makes the coolant injections attached to the wall and achieves a larger coolant coverage in lateral direction. Although the swirling cooling scheme increases the heat transfer of the endwall, it still has the best overall endwall cooling performance. • The interaction between the swirling coolant and the mainstream restructures the vortex structure and restrains the passage vortex. • The swirling coolant has better ability to adhere to the wall and stability, making it difficult for swirling coolant lifted off the wall. • Swirling cooling scheme enhances endwall overall cooling performance. • The pressure surface corner region where is difficult to cool obtains good coolant coverage effect. [ABSTRACT FROM AUTHOR]