Cross-wind degrades the performance of a natural draft dry cooling tower (NDDCT). Based on the basic affecting mechanism, this paper introduces a wind collecting approach. By using a wind collecting duct, the lateral flow acceleration of cross-wind is broken up, and the lateral flow kinetic energy is utilized to increase the lateral and rearward static pressure outside the radiator inlet. By adoption of a CFD model, the effect of the wind collecting approach is investigated comprehensively. It is found that the wind collecting ducts could improve the pressure distribution around the radiator bundle, reinforce the lateral air intake, and reduce the intensity of mainstream vortices, so as to enhance the ventilation rate of a NDDCT. For an outstanding performance, the two-duct wind collecting scheme is suggested, which may assure a NDDCT working in an approximately wind free manner in all investigated cross-wind range, and increase the ventilation rate by ~63% under the high cross-wind condition, which may reduce the overall coal consumption by 23500~33500 tons annually for a 660 MW coal-fired unit. The numerical results are confirmed by a hot state modelling experiment conducted in a wind tunnel.
Abstract A fast reverse intersystem crossing (RISC) remains an ongoing pursuit for multiresonance (MR) emitters but faces formidable challenges, particularly for indolocarbazole (ICz) derived ones. Here, heavy‐atom effect is introduced first to construct ICz‐MR emitter using a sulfur‐containing substitute, simultaneously enhancing both spin–orbit and spin–vibronic coupling to afford a fast RISC with a rate of 1.2 × 10 5 s −1 , nearly one order of magnitude higher than previous maximum values. The emitter also exhibits an extremely narrow deep‐blue emission peaking at 456 nm with full‐width at half‐maxima of merely 12 nm and a photoluminescence quantum yield of 92%. Benefiting from its efficient triplet upconversion capability, this emitter achieves not only a high maximum external quantum efficiency (EQE) of 31.1% in organic light‐emitting diodes but also greatly alleviates efficiency roll‐off, affording record‐high EQEs of 29.9% at 1000 cd m −2 and 18.7% at 5000 cd m −2 among devices with ICz‐MR emitters.
Abstract Highly efficient and stable blue organic light-emitting diodes (OLEDs), though desired for displays and lightings, remain rare after decades of research. Here we report a perdeuteration strategy to stabilize blue thermally activated delayed fluorescence (TADF) emitters. It is unveiled that deuteration would reduce the population at high vibrational energy levels by suppressing high-frequency vibrations, thus reducing the possibility of bond dissociation. Deuteration also leads to a denser packing of vibrational energy states, thus slowing down the internal conversion of the excited states to the ground and impeding non-radiative decay. The proof-of-concept perdeuterated blue TADF emitters concurrently exhibit not only higher efficiencies but also more than doubled lifetimes in OLEDs compared to protonated ones. By using them as sensitizers in TADF-sensitized fluorescent devices, a maximum external quantum efficiency of 33.1% and a superbly long LT80 (time to 80% of initial luminance) of 1,365 h with a Commission Internationale de l'Eclairage y-coordinate of 0.20 under 1,000 cd m − 2 are obtained simultaneously, even outperforming the best blue phosphorescent OLEDs.
Though the oxygen enrichment and fuel-rich/quick-mix/fuel-lean (RQL) combustion are effective to improve burning velocity and reduce NOx emissions respectively, their combination feasibility and characteristics for ammonia (NH3) combustion need further investigation as oxygen enrichment could increase NOx production. Thus, a kinetic modeling study was conducted on the NOx emission characteristics of an oxygen-enriched and RQL-staged NH3-fired combustor under gas turbine conditions by using the chemical reaction network (CRN) method. The results revealed that NOx emission could be minimized as long as the fuel-rich stage equivalence ratio wass optimally kept according to the oxygen enrichment intensity (Ω) in the fuel-rich stage oxidizer, regardless of the Ω in the fuel-lean stage oxidizer. With a higher Ω, the overall low NOx range became wider, while the optimal fuel-rich stage equivalence ratio increased and the corresponding NOx emission further decreased. This mainly benefits from the stronger NH3 consumption in the fuel-rich stage due to the higher temperature and OH/H/O radicals under a higher Ω, and a high fuel-rich stage temperature was proposed. However, a higher Ω in the primary stage enhanced the thermal NOx ratio in the fuel-lean stage. The results showed that the oxygen-enriched NH3 combustion wih proper fuel-rich stage equivalence ratio adjustment can simultaneously improve the burning velocity and reduce NOx emissions for a gas turbine.
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