In this study, attempts have been made to utilize ammonia in the industrial heating field, in which highly preheated air around 1000°C is used under high temperature atmosphere inside the furnace 1200°C. The high temperature inlet air and atmosphere are realized in the bench-scale furnace. Ammonia and methane in the fraction of 30%-NH₃ and 70%-CH₄ based on lower heating value, corresponding volumetric fraction of 55%-NH₃ and 45%-CH₄ is used as fuel under the fixed thermal input of 40-kW. On the furnace, the nozzle burner is installed in which fuel nozzles are installed inner side of the annular air nozzle, and furthermore, injection nozzles called “F2 nozzle” are installed on the top side of the furnace to inject NH₃ separately from the air. To stabilize the combustion field, CH₄ is injected from the burner for all cases. Results of exhaust gas measurements show that over 1000ppm of NO_x is emitted for NH₃ burner injection, however, in the case F2#1-NH₃ injection from x = 0.3-m where x is the distance from the burner, NO_x is drastically decreased to 464ppm even with high temperature inlet air and atmosphere. NO_x concentration is further decreased by increasing the distance of the F2-NH₃ nozzle from the air, then, NO_x is reduced to 160ppm for F2#6-NH₃ injection which is located at 3.3-m from the burner air. Furthermore, unburned NH₃ and N₂O are not detected for all cases of examined. As a result of species measurement inside the furnace for F2#6 NH₃ injection case, it is found that the O₂ concentration is significantly low at the upstream of NH₃ injection position, thus, injecting NH₃ into the low O₂ concentration region is considered to be effective to reduce NO_x even for NH₃ combustion with high temperature inlet air and atmosphere.

The formation process of an initial flame kernel in laser ignition was analytically examined for understanding its experimentally-observed hugeness. First, we evaluated the thermodynamic state of the laser-heated plasma by examining the laser-absorption waves in the detonation mode and in the radiation mode, taking account of lateral energy loss. Second, we evaluated the mechanical energy loss during the plasma expansion to the initial pressure. In addition, we evaluated the thermodynamic state of the plasma after its expansion to the initial pressure. In this evaluation, we calculated not only the isentropic-expansion process but also the effects of thermal diffusion from the hot plasma to the ambient gas in an approximate manner. During the course of this study, we developed some empirical formulas for the properties of air plasma to examine analytically the formation process of an initial flame kernel in laser ignition. It has been found that the laser-absorption wave must be in the detonation mode for typical laser-ignition conditions, and that the hugeness of the initial flame kernel is ascribed not only to the hydrodynamic expansion of the high-pressure laser-heated plasma but also to the thermal diffusion from the high-temperature plasma to the ambient gas. Finally, we derived the scaling laws for the size, internal energy, and temperature of the initial flame kernel with respect to the incident energy flux and absorbed energy of the igniting laser.

This study investigates the combustion and emission characteristics of water-in-diesel emulsified fuels, focusing on varying water content and droplet sizes. Emulsified fuels were prepared with water contents ranging from 2 to 24 vol% and droplet diameters of <3 μm, 26.5 μm, and 39.8 μm, produced using both strong stirring and membrane emulsification methods. These fuels were tested in a single cylinder, air-cooled direct injection diesel engine at a constant speed of 2300 rpm. The results showed that increasing water content generally decreased engine output power due to reduced diesel fraction and latent heat effects. However, thermal efficiency improved up to 14 vol% for small droplets and 20 vol% for larger droplets, driven by an extended ignition delay and higher peak heat release during premixed combustion. Beyond these water content thresholds, thermal efficiency declined due to increased ratio of phase-specific combustion durations after and before CA50 i.e., burn ratio, leading to energy losses from prolonged diffusion-controlled combustion. Emission measurements indicated that higher water content reduced NOx and soot emissions but increased CO levels. This study concludes that emulsified fuels with larger water droplets and 20 vol% water content offer the best balance between thermal efficiency and emission reduction.

In this study, we investigate membrane distillation (MD), which is a promising desalination technology. Conventional evaporation methods require seawater to be heated to its boiling point, and reverse osmosis (RO) methods require the liquid to be pressurized to a high pressure. MD is a technology that enables freshwater production without imposing high temperature and pressure conditions. This technology uses the phase transition of water in seawater to separate the generated water vapour from seawater using separation membranes with nanoscale pores. The driving force of the water vapour is the difference in water vapour pressure before and after passing through the separation membranes, which depends on the temperatures near both ends of the separation membrane surfaces. We analysed heat and mass transport by using a thermal network method assuming a 1D steady state. The network models were applied to a direct contact membrane distillation (DCMD) and a permeate gap membrane distillation (PGMD) and compared with experimental values for distillation simply using pure water. The results show that, for the temperatures, the experimental and calculated values agreed about the membrane surface temperatures within approximately 7.5 % to 15 % of the temperature difference between the hot water and cooling water temperatures, and for the permeate fluxes, the experimental and calculated values were consistent within 25 % of the calculated values.

This study investigated a premixed propane-air flame in a partially tapered swirl burner. Experimentally, we found that a flame resembling a morning glory flower formed at an equivalence ratio near the lean flammability limit. A numerical simulation of the flame with detailed chemistry revealed that the upstream flame tip existing at the central axis in the recirculation zone was significantly weakened, whereas the curved flame convex downstream was significantly strengthened. In addition, high peaks of temperature, heat release rate (HRR), and concentrations of OH, O, and H radicals were formed immediately behind the latter curved flame, which enabled the flame to exist stably under conditions very close to the lean flammability limit. Subsequently, to identify the influence of the Lewis number on the flame shape, adiabatic methane-air swirling flames were simulated with the Lewis numbers manipulated between 0.90 and 1.20. The results show that an increase in the Lewis number from unity changes the flame shape from a circular paraboloid to one somewhat similar to a morning-glory flower, whereas a decrease in the Lewis number from unity changes the flame shape from a circular paraboloid to one somewhat similar to a comet. This result suggests that the large difference in flame shapes among hydrogen-air, methane-air, and propane-air under very lean conditions is due to the difference in their Lewis numbers.

In recent years, industrial boilers that generate power from biomass have drawn a lot of attention. Nevertheless, a sizable portion of thermal energy is frequently lost to the environment as flue gas throughout the process. Stirling engine: a very efficient external combustion engine and little emissions as compared to other available engines, would be a good solution to overcome this issue as it can be used with any type of heat source. When the Stirling engine is connected to a heat source with a lower temperature, it exhibits a significant reduction in performance. Consequently, in this study a computational fluid dynamic (CFD) simulation model of Stirling engine was introduced in order to evaluate the possibility of recovering low temperature waste heat from biomass combustion. It has been shown to be effective in delivering useful, comprehensive information for further improvement of the engine. Then further parametric analysis will be investigated to enhance the engine’s performance. The investigation involving waste heat from wood pellets, coconut husk and bagasse as heat source then demonstrates the engine’s ability to recover and utilize heat as low as 70°C and generate power output ranging from 30 to 40 W and thermal efficiency of around 14%. Parametric analysis using different regenerator porosities, engine speeds and working fluid gases were also carried out to determine the optimal Stirling engine’s performance. The results demonstrate optimum performance at 0.85-0.9 of porosity and engine speed of 700 rpm and above. Overall, the results showed promising outcomes of Stirling engine to recover low temperature heat from biomass.

With the increasingly stringent emission requirements for shipping, methanol is a promising alternative fuel. The effects of mixing ratio and ambient temperature on the spray and ignition characteristics of high proportion methanol / Polyoxymethylene dimethyl ethers (PODE) blended fuel were studied on the visual constant volume combustion bomb experimental platform. The maximum mixing ratio of methanol was 70 %. The spray penetration, spray cone angle and spray area of the blended fuel increase with the increase of methanol ratio. During the development of the blended, the spray penetration first increases and then decreases, and finally tend to be stable. The time for the spray penetration to reach its peak is negatively correlated with the ambient temperature. As the methanol blending ratio increases, the flame spontaneous luminescence intensity and flame area decrease, and the ignition delay period prolongs. The increase of ambient temperature can improve the combustion performance of the blended fuel, but the effect of the mixing ratio on the fuel ignition gradually weakens with the increase of ambient temperature. It is of great significance to study the spray and ignition characteristics of high proportion methanol / PODE blended fuel for the application of high proportion methanol fuel in marine diesel engines.

The rapid progression of industrialization and the integration of artificial intelligence in recent years emphasizes the critical need for efficient thermal cooling solutions. Despite significant strides in technology, existing liquid cooling methods, notably boiling heat transfer and spray cooling, encounter substantial obstacles attributable to the well-documented Leidenfrost effect. Upon contact with a highly heated surface, a liquid generates a vapor layer that acts as an insulator, elevating the liquid above the surface and severely impeding heat transfer efficiency. While notable advancements have been achieved in mitigating the Leidenfrost effect, a comprehensive understanding of the underlying mechanisms remains limited. Furthermore, challenges persist in sustaining high-temperature environments across diverse structures, materials, and technologies, impeding progress in this domain. This review aims to provide a thorough account of fundamental tactics for suppressing the Leidenfrost phenomenon on high-temperature substrates. It will underscore distinctive attributes and challenges while exploring avenues for the development of efficient and sustainable thermal management solutions.