Emir Yilmaz

The global rise in carbon emissions presents a rising challenge for current and future generations. In the pursuit of zero carbon emissions, ammonia (NH3) has emerged as an attractive alternative energy source. Ammonia offers a carbon-free fuel option with a higher energy density than liquid hydrogen while maintaining ease of transport and storage. However, ammonia still has its drawbacks, such as a high autoignition temperature, slow burning velocity, and low heating value, that demand further investigation of its combustion characteristics. This experiment was done to study the effect of nozzle shape and equivalence ratio (ɸ) on the combustion of an ammonia/oxygen/argon mixture using a constant volume combustor equipped with a sub-chamber. The fuels were premixed for 10 minutes and conditioned to an initial pressure of 0.2 MPa and an initial mixture temperature of 423 K. The results show that the different nozzle shapes each have their advantages in terms of pressure and jet speed. Overall, the lean mixtures (ɸ0.6 and ɸ0.8) consistently performed better compared to the stoichiometric mixtures (ɸ1.0) in all categories investigated in this study. The round nozzle generates higher pressure, while the special shape nozzle enhances jet speed, highlighting trade-offs between the two.

<jats:p>This study examines the feasibility of utilizing the press forming method on multi-layer, multi-orientation continuous CFRP preform produced by the additive manufacturing (AM) technique. The 5-layer preforms with fiber orientations of 45° and -45° impregnated in Nylon-6 resin layers were made by a 3D printer, and press-formed in varying temperatures and pressures. Optimal forming outcomes were determined by qualitative evaluations of the surface finish, fiber impregnation, resin flow, and quantitative observations on shape variations by comparison with the mold dimensions. Experimental results showed that the molding temperature of 220°C and pressure between 0.5MPa - 1MPa could produce preforms with optimal surface conditions. There was almost no void of bubble defects, no excess resin flow, and a smooth transition was established between the carbon fiber and the matrix resin layers while allowing the full mechanical strength properties to be realized. The formed preform evaluations confirmed that the press molding method is feasible on multi-layer, multi-orientation continuous CFRP with optimal surface conditions.</jats:p>

Due to the problem with carbon dioxide (CO2) emissions, alternative fuels such as ammonia (NH3) have been garnering a lot of attention lately. This is due to its carbon-free molecular structure, ease of transport, and high energy density. Unfortunately, ammonia is not without flaws since it is considered a difficult fuel to burn in conventional internal combustion engines. To further investigate the burning characteristics of ammonia, this study is conducted for ammonia/gasoline co-combustion using a modified engine equipped with a sub-chamber. The engine ran at 1000 RPM and had a 17.7 compression ratio with two injection timings of-55° and 10° crank angle (CA) after the top dead center (ATDC), while the ammonia energy ratios were adjusted across a range from 40% to 70%. The results show that the earlier injection timing allowed better premixing between the air and fuel mixture, thus enhancing the overall combustion characteristics. For the later injection timing, the nitrogen oxides (NOx) emissions decrease at the higher ammonia energy ratio due to the denitrification of nitrogen oxides (DeNOX) process. Overall, the earlier injection timing appears to be optimal for 40% to 70% ammonia energy ratio under the present condition.