Having a comprehensive knowledge of phase equilibrium is advantageous for industrial simulation and design of chemical processes. For further acquisition of primary data to facilitate the separation and purification of waste oil biodiesel systems, a liquid–liquid equilibrium (LLE) tank is deployed for the ternary system of waste oil biodiesel + methanol + glycerin, thereby enhancing the precision and efficiency of the process. The phase equilibrium system was constructed under the influence of atmospheric pressure at precise temperatures of 303.15 K, 313.15 K, and 323.15 K. The equilibrium components of each substance were analyzed by employing high-temperature gas chromatography, a sophisticated analytical method that enables the identification and quantification of individual components of a sample. Moreover, the ternary liquid–liquid equilibrium data were correlated by implementing the NRTL and UNIQUAC activity coefficient models. Subsequently, the binary interaction parameters of the ternary system were derived by conducting regression analysis. The experimental data demonstrated that the presence of lower methanol content in the system resulted in nearly immiscible biodiesel and glycerol phases, which ultimately facilitated the separation of biodiesel and glycerol. Conversely, with the increase in methanol content, the mutual solubility of biodiesel and glycerol was observed to increase gradually. The results showed that the calculated values of the NRTL and UNIQUAC models aligned well with the experimental values. The root-mean-square deviations of the NRTL and UNIQUAC models at 313.15 K were 2.76% and 3.56%, respectively.

Scouring experiments were conducted using a three-dimensional laser scanning technology for angles of the jet spanning the interval from 0° to 30°, and the characteristics of the scour hole in equilibrium conditions were investigated accordingly. The results indicate that the optimal scouring effects occur when the jet angle is in the ranges between 15° and 20°. Moreover, the dimensionless profiles of the scour hole exhibit a high degree of similarity at different jet angles. Numerical simulations conducted using the Flow-3D software to investigate the bed shear stress along the jet impingement surface have shown that this stress is influenced by both the resultant force and the jet impingement surface area. It reaches its maximum value when the jet is vertical, decreases rapidly as the jet starts to tilt, then increases slightly, and decreases again significantly when the angle exceeds 20°.

This study outlines the development of a three-dimensional model for the crankshaft-bearing and a multi-body dynamics model for a four-stroke marine diesel engine. The models are constructed through a simulation approach that integrates the finite element method and multi-body dynamics method. Additionally, the Greenwood/Tripp asperity contact theory and average flow model are incorporated. The investigation also delves into the dynamic coupling between the crankshaft-bearing multi-body system and the mixed lubrication effects, accounting for lubricating oil as a thermo-electrohydrodynamic model and the journal as an elastomer. The study meticulously examines the lubrication characteristics of main bearings in marine diesel engines during normal operational conditions and scrutinizes the impact of various parameters on crankshaft-bearings. The study concludes by offering recommendations and technical support for innovative optimization design and model enhancement of diesel engine crankshaft-bearings.

Water jet technology is widely used in submerged buried pipes as a non-traditional trenching process, often involving a complex sediment response. An important adjustable and influential engineering variable in this technology is represented by the impinging distance. In this study, the FLOW-3D software was used to simulate the jet scouring of sand beds in a submerged environment. In particular, four sets of experimental conditions were considered to discern the relationship between the maximum scour depth and mass and the impinging distance. As shown by the results, a critical impinging distance exists by which the static scour depth can be maximized; the scour mass ratio between dynamic and static conditions decreases as the impinging distance increases. Moreover, the profile contours are similar when the erosion parameter is in the range 0.35 < < 2. Empirical equations applicable for predicting the jet trenching contour under both dynamic and static scour modes are also provided in this study.

In this paper, the effect of jet holes under different impinging distances was studied by using Flow-3D fluid software. The results show that when the impinging distance of the jet is small, the profile is random. There is a critical impinging distance. At this time, the width and depth of the hole enter a relatively static state, which can be regarded as the key point of the transition stage. After exceeding the critical impinging distance, the depth and width of the hole quickly reach the maximum value; as the impinging distance continues to increase, the hole parameters gradually decrease. The empirical formula of hole parameters changing with impinging distance under specific working conditions is obtained.