Search Results (3)

Nowadays it has become particularly valuable to control the Particulate Matter (PM) emissions from the road transport sector, especially in vehicle powertrains with an Internal Combustion Engine (ICE). However, almost no publication has focused on a comparison of the microscopic characteristics of gasoline and ethanol spray under injection pressure conditions of more than 30 MPa, except in the impingement process. By using a Phase Doppler Particles Analyser (PDPA) system, the microscopic characteristics of gasoline and ethanol spray from a Gasoline Direct Injection (GDI) injector under injection pressure ($P_I$) up to 50 MPa was fully explored in this research. The experimental results demonstrate that under the same $P_I$, the second peak of the probability ($p_d$) curves of droplet normal velocity for gasoline is slightly higher than that of ethanol. Moreover, gasoline spray exceeds ethanol by about 5.4% regarding the average droplet tangential velocity at 50 mm of jet downstream. Compared to ethanol, the $p_d$ curve’s peak of droplet diameter at (0, 50) for gasoline is 1.3 percentage points higher on average, and the overall Sauter mean diameter of gasoline spray is slightly smaller. By increasing $P_I$ from 10 MPa to 50 MPa, $p_d$ of the regions of “100 ≤ Weber number ($We$) < 1000” and “$We$ ≥ 1000” increases by about 23%, and the $p_d$ of large droplets over 20 μm shows a significant reduction. This research would provide novel insights into the deeper understanding of the comparison between gasoline and ethanol spray in microscopic characteristics under ultra-high $P_I$. Additionally, this research would help provide a theoretical framework and practical strategies to reduce PM emissions from passenger vehicles, which would significantly contribute to the protection and sustainability of the environment. Full article

HVAF (High Velocity Air Flame) flame spraying can generate supersonic high-temperature gas jets, enabling thermal spraying at unprecedented speeds. However, there is a problem with the energy cost of this device. This study focused on combustors that used cheap liquid fuel (kerosene) as the fuel for HVAF. In this research, we have developed a compact combustor with a narrow channel as a heat source for the HVAF heat atomizer. Using this combustor, the stability of the flame formed in the combustor, the morphology of the flame, and the temperature behavior in the combustion chamber were investigated in detail. As a result, the magnitude of the swirling airflow had a great influence on the structure of the flame formed in the combustor, and the stable combustion range of the combustor could be determined. As the swirling air flow rate changes, the equivalent ratio of the entire combustor changes significantly, and the flame structure also transition from the premixed flame to the diffusion flame. From this study, it was confirmed that the temperature inside the combustor has great influence on the flame structure. Full article

Thermal barrier coating (TBC) plays a vital role in the gas turbine combustor liner (CL) to mitigate the internal heat transfer from combustion gas to the CL and enhance the parent material lifetime of the CL. This present study examined the thermal analysis and creep lifetime prediction based on three different TBC thicknesses, 400, 800, and 1200 μm, coated on the inner CL using the coupled computational fluid dynamics/finite element method. The simulation method was divided into three models to minimize the amount of computational work involved. The Eddy Dissipation Model was used in the first model to simulate premixed methane-air combustion, and the wall temperature of the inner CL was obtained. The conjugate heat transfer simulation on the external cooling flows from the rib turbulator, impingement jet, and cross flow, and the wall temperature of the outer CL was obtained in the second model. The thermal analysis was carried out in the third model using three different TBC thicknesses and incorporating the wall data from the first and second model. The effect of increasing TBC thickness shows that the TBC surface temperature was increased. Thereby, the inner CL metal temperature was decreased due to the TBC thickness as well as the material properties of Yttria Stabilized Zirconia, which has low thermal conductivity and a high thermal expansion coefficient. With the increase in TBC thickness, the average temperature difference between the TBC surface and the inner metal surface increased. In contrast, the average temperature difference between the inner and outer metal surfaces remained nearly constant. The von Mises equivalent stress, based on the material property and thermal expansion coefficient, was determined and used to find the creep lifetime of the CL using the Larson–Miller rupture curve for all TBC thickness cases in order to analyze the thermo-structure. Except in the C-channel, the increasing TBC thickness was found to effectively increase the CL lifespan. Furthermore, the case without TBC was compared with the damaged CL with cracks due to thermal stress, which was prevented by increasing TBC thickness shown in this present study. Full article