Search

To investigate the corrosion damage and degradation mechanism of NiCoCrAlY/AlSiY composite coatings in alternating high and low temperature marine environments, the corrosion damage behavior of NiCoCrAlY/AlSiY composite coatings was studied by designing the alternating high and low temperature oxidation and high temperature oxidation-acidic salt spray alternating tests. Results showed that after 50 cycles of alternating high and low temperature oxidation at 750 ℃, the coating underwent oxidative erosion in the oxidation test, but the integrity of the surface structure was not damaged. After the experiment, the weight of the alloy increased by only 3.87 mg/cm2, indicating that the coating effectively inhibited the diffusion of oxygen into the interior and prevented the substrate from oxidative attack. During the 50 cycles of alternating high temperature oxidation and acidic salt spray tests, the NiCoCrAlY/AlSiY composite coating experienced severe corrosion degradation, and the alloy weight increased to as high as 13.52 mg/cm2 by the end of the test. Due to long-term salt spray erosion, the oxide layer structure weakened, leading to surface loosening, the formation of corrosion pits, and even peeling. As the number of alternating cycles of high temperature oxidation-acidic salt spray increased, the critical reaction causing coating damage shifted from oxidative erosion to thermal corrosion. The chlorine, generated from the eutectic reaction of the mixed salt, acted as a catalytic carrier and accelerated the growth of oxidation products, demonstrating that the NiCoCrAlY/AlSiY composite coatings had weak corrosion resistance under alternating high temperature oxidation-acidic salt spray environments.

The heat transfer process of the sweeping jet and film composite cooling (SJF) structure of the turbine blade leading edge is complex. The current work divides the overall cooling effectiveness of the SJF into the impingement heat transfer effectiveness, the convection heat transfer effectiveness inside the film holes, and the external film cooling effectiveness by the decoupled method. Various cooling effectiveness proportions and trends are compared when the blowing ratios are 1.05, 2.07, and 4.11. There is an average ratio of 64.33% for impingement heat transfer effectiveness and 38.02% for convection heat transfer effectiveness. The ratio of external film cooling effectiveness gradually changes from positive to negative with the increase of the blowing ratio. Therefore, the proportion of external film cooling effectiveness and impingement heat transfer effectiveness should be considered when applying SJF. The convection heat transfer effectiveness cannot be ignored, especially when the design scheme of the shower head is used.

The carbon emitted by vehicles traveling on curved roads is greatly affected by the alignment of the route, yet the mechanism behind this is not yet clear, leading to current horizontal alignment designs being unable to avoid this problem. To clarify the principles and indicator thresholds of low-carbon design for planar geometry, this study takes the carbon emission of traveling on curved routes as the research object, and establishes a relationship model between carbon emissions and design indicators based on the principles of vehicle dynamics and kinematics. Field tests were conducted to validate the quantitative relationship model. The model shows that both radius and superelevation are negatively correlated with carbon emissions, while the lateral force coefficient is positively correlated with carbon emissions. The contribution of radius to carbon emissions is greater than that of superelevation. This study clarifies the recommended values of low-carbon design indicators by assessing carbon emissions according to the current route design specification, outlines the principles of superelevation settings, and proposes a methodology to deal with the relationship between superelevation and the lateral friction coefficient. The research findings promote the quantification and standardization of low-carbon highway design, contributing to the early mitigation of high-carbon emissions from curved traffic during the design phase. [ABSTRACT FROM AUTHOR]

Tunnel–interchange connecting sections pose significant safety challenges on mountainous expressways due to their high incidence of accidents. Improving road safety necessitates a comprehensive understanding of driver behavior in such areas. This study explores the influences of road characteristics, signage information volume, and traffic conditions on drivers' car-following and lane-changing behavior in tunnel–interchange diverging areas. Utilizing driving data from 25 subjects of 72 simulated road models, driving performance is assessed using the Friedman rank test and multivariate variance analysis. The results highlight the significant influence of both connection distance and signage information load on driving behavior. In tunnel–interchange scenarios, the reduction in velocity increased by 62.61%, and speed variability surged by 61.11%, indicating potential adverse effects on driving stability due to the environmental transitions. Decreased connection distances are associated with reduced lane-changing durations, larger steering angles, and increased failure rates. Furthermore, every two units of increase in signage information leads to a 13.16% rise in maximum deceleration and a 5% increase in time headway. Notably, the signage information volume shows a significant interaction with connection distance (F > 1.60, p < 0.045) for most car-following indicators. Hence, the study recommends a maximum connection distance of 700 m and signage information not exceeding nine units for optimal safety and stability. [ABSTRACT FROM AUTHOR]