Mini-LEDs with Diffuse Reflection Cavity Arrays and Quantum Dot Film for Thin, Large-Area, High-Luminance Flat Light Source

Mini-light-emitting diodes (mini-LEDs) were combined with multiple three-dimensional (3D) diffuse reflection cavity arrays (DRCAs) to produce thin, large-area, high-brightness, flat light source modules. The curvature of the 3D free-form DRCA was optimized to control its light path; this increased the distance between light sources and reduced the number of light sources used. Experiments with a 12.3-inch prototype indicated that 216 mini-LEDs were required for a 6 mm optical mixing distance to achieve a thin, large-area surface with high brightness, uniformity, and color saturation of 23,044 cd/m2, 90.13%, and 119.2, respectively. This module can serve as the local dimming backlight in next generation automotive displays.

Experimental Investigation of Air–Fuel Mixing Effects on Flame Characteristics in a Direct fired Burner

The length and pattern of air–fuel mixing plays a significant role in the uniformity, flame temperature, and emission characteristics, which can lead to a superior product quality in a non-oxidizing direct fired burner for a cold-rolled steel plate furnace. In this study, a diffusion-flame-type burner and partially-premixed-type burner were experimentally investigated to understand their effects on flame shape, flame temperature, and exhaust gas characteristics. With this aim, fuel nozzle size, nozzle hole number, fuel injection angle, and mixing distance of fuel and air were varied during the experiments. Computational fluid dynamics simulations were also performed to investigate the air–fuel mixing state for a nozzle-mixed burner and a partially-premixed burner. The results show that the flame temperature of the partially-premixed burner increases by up to 26 °C on average compared to that of the nozzle-mixed burner. It is also shown that the mixing distance plays an important role in the flame temperature of the partially-premixed burner. In addition, the residual oxygen concentration and volume ratio of CO/CO2 in the flue gas of the partially-premixed burner exhibit lower concentrations compared to those of the diffusion flame burner.

Parametric Effects on Internal Aerodynamics of Lobed Mixer-Ejector With Curved Mixing Duct

The internal flow characteristics inside lobed mixer-ejector with curved mixing duct and the parametric effects on the lobed mixer-ejector performance are investigated numerically and validated by experimental test. The curved mixing duct affects the development of the streamwise vortices induced by the lobed mixer. When the mixing process undergoes the transition from the straight section to the bent section, the flow inside the curved mixing duct is dominated by the impinging and centrifugal effects. In general, the pumping ratio is decreased approximately 20%–30% once the bent section is mounted on the straight duct. The mixer-ejector performance could by improved by increasing the straight section length, due to more fully momentum utilization of primary jet and weaker influence of bent section on the back pressure near nozzle exit. The mixer-ejector pumping capacity is also augmented with the increase of mixing duct area ratio until the area ratio is reached to 3.5. And the fully-utilization of primary jet momentum inside mixing duct with big area ratio needs long mixing distance. The pumping ratio is decreased as the increase of bent angle of curved mixing duct in approximately linear relationship. When the bent angle exceeds 45 deg, the thermal mixing efficiency is decreased rapidly as the increase of bent angle.

Optimized Ammonia Injection for Power Plant SCR Systems

Ammonia injection grid (AIG) is used to introduce vaporized ammonia (NH3) into an exhaust gas stream for nitrous oxide (NOx) reduction in selective catalytic reduction (SCR) systems. Computational and experimental studies on the AIG resulted in significant improvements in the turbulence mixing between the injected ammonia and the exhaust gas. Improved mixing is instrumental to maximize catalyst performance, extend catalyst life time, minimize catalyst volume, decrease system pressure drop, minimize reagent use and ammonia slip, minimize the overall size of the SCR system, and minimize risks associated with designing the SCR system. It is found that an AIG with a turbulence-generating edge dramatically increases the mixing efficiency and, therefore, reduces the mixing distance required to obtain acceptable distributions of the NH3 to NOx ratio. Results indicate over 50% reduction of the required mixing distance due to the turbulence generating edge. This work summarizes the obtained results from computational CFD simulations for two-dimensional and three-dimensional models, however the proposed arrangement of the injection grid has been successfully tested in laboratory experiments and applied to several commercial power generating systems. The commercial performance results will be reported in the subsequent publications.

Effect of Initial Fuel Distribution and Subsequent Mixing on Emissions From Lean, Premixed Flames

Results presented here illustrate how optimizing the fuel distribution at injection reduces the subsequent mixing needed for ultralow emissions in lean, premixed gaseous flames. An experimental facility was developed for bluff body stabilization of a high pressure natural gas flame at the exit of a 4” diameter mixing tube. Fuel was injected through two concentric ring manifolds. NOx and CO drop dramatically from diffusion flame to perfectly premixed levels with increasing mixing distance. Furthermore, for each mixing distance, there is an optimum fuel split that results in minimum NOx and CO emissions. Computational fluid dynamics and laser sheet flow visualization show the recirculation zones and fluid mixing that affect fuel injection requirements. Although improved fuel injection and greater mixing will both drive the NOx-CO curve to the origin, improving the initial fuel distribution reduces the requirement for subsequent mixing.