Tiexiong Su

Taking advantage of the ionic size and mass disorder as component design criteria, three novel high-entropy rare-earth zirconate ceramics, including (Sm_0.2Gd_0.2Dy_0.2Er_0.2Tm_0.2)₂Zr₂O₇, (Gd_0.2Dy_0.2Ho_0.2Er_0.2Tm_0.2)₂Zr₂O₇ and (Gd_0.2Dy_0.2Ho_0.2Er_0.2Yb_0.2)₂Zr₂O₇, with single-phase fluorite structure were successfully synthesized. All compositions exhibited enhanced mechanical properties, with Vickers hardness and fracture toughness increasing as the grain size decreased. (Gd_0.2Dy_0.2Ho_0.2Er_0.2Yb_0.2)₂Zr₂O₇ demonstrated superior mechanical performance, achieving values of 11.41 ± 0.40 GPa and 1.78 ± 0.12 MPa·m^1/2, respectively. The thermal expansion coefficients at 1000 °C ranged from 10.80 × 10⁻⁶ K⁻¹ to 11.39 × 10⁻⁶ K⁻¹, which is proportional to the average ionic bond length. Notably, (Sm_0.2Gd_0.2Dy_0.2Er_0.2Tm_0.2)₂Zr₂O₇ exhibited low room-temperature thermal conductivity (1.58 W·m⁻¹·K⁻¹) due to pronounced size and mass disorder, without compromising structural stiffness. These findings highlight the potential of high-entropy design for advanced thermal barrier coatings.

The temperature of lubricating oil plays a pivotal role in determining the performance of engines and other machinery, underscoring the importance of studying its temperature distribution for optimizing engine efficiency. In this study, a custom experimental setup was developed to measure the transmittance of lubricating oil across a wavelength range of 380 nm to 1040 nm at various temperatures. A novel method was proposed to compute the temperature distribution along the light path using transmission spectra. By formulating a mathematical model that correlates the temperature distribution with light intensity, the optical characteristics of lubricating oil undergoing a phase change at a single interface in low-temperature environments were thoroughly investigated. A comparative analysis between the experimentally measured temperatures and those obtained from temperature sensors revealed that the temperature distribution trends predicted by the proposed method closely aligned with the experimental data, exhibiting an average deviation of only 2.87 °C. These results demonstrate the robustness and accuracy of the method, validating its potential for reliable temperature distribution estimation in lubricating oil.

In order to solve the problems of the method involving the optimization of the traditional combustion chamber structure, which has a long computation cycle, high computation cost, and can easily fall into the local optimal solution, this paper refers to the concept of a fuzzy neural network in machine learning. This study proposes a method of combustion chamber structure optimization that uses a fuzzy neural network to prejudge the results of the fitness function before calculating it in order to reduce the periodicity of computation and improve computational accuracy. The validation results show that the combustion chamber structure optimization method proposed in this paper can effectively reduce the computational cost under the premise of guaranteeing optimization accuracy. Using the test function, compared with the traditional genetic algorithm, the average number of iterations at convergence is reduced by 28.59%, and the average number of calculations of the fitness function is reduced by 25.59%. When optimizing the combustion chamber structure, the peak pressure of the optimal combustion chamber structure is increased by 10.32%, the computational count is reduced by 23.33%, and the time consumed is reduced by 23.91% compared with the traditional genetic algorithm.

In this paper, the macroscopic and microscopic characteristics of diesel spray with elliptical and circular nozzles were investigated under an ambient density of 65.6 kg/m³ by combining an optical test and numerical simulation method of VOF-Spray One-Way Coupling and Large Eddy Simulation. Two elliptical nozzles with varying aspect ratios (1.25 and 1.5) and a circular nozzle were employed for comparison, with the same cross-sectional area. The results demonstrated that the spray tip penetration (STP) of elliptical nozzles was significantly diminished in comparison to that of the circular nozzle and that STP for the elliptical nozzle with a larger aspect ratio was observed to be smaller, primarily due to the elevated aerodynamic drag and accelerated kinetic energy dissipation. The spray cone angle (SCA) of elliptical nozzles was greater than that of the circular nozzle. The average SCA of the elliptical nozzle with a larger aspect ratio was the greatest in both planes. The spray asymmetry with elliptical nozzles resulted in the instability of the spray boundary, leading to the earlier fragmentation and atomization of the spray and faster radial diffusion. For the same STP, the elliptical nozzle with a larger aspect ratio exhibited the greatest spray area in both planes. Elliptical nozzles are subject to a greater degree of inhomogeneous shear than circular nozzles, which results in an accelerated rate of droplet breakage and a concomitant decrease in Sauter Mean Diameter.

Common rail injector response characteristics depend on the control chamber pressure change rate, the outlet throttle diameter by manufacturing errors, or wear-induced deviations that affect the rate of pressure change in the control chamber, so the accuracy of the outlet throttle diameter directly affects the control valve response consistency. This paper presents a computational fluid dynamics (CFD) simulation of the effect of the deviation of the outlet throttle diameter on the average mass flow rate of the outlet throttle during the opening of the spherical valve in order to reduce this difference and ensure uniform injection characteristics. The results illustrate that with the increase in outlet throttle diameter deviation, the volume of gas phase in the control valve increases and the rate of pressure reduction in the control chamber accelerates, and the sensitivity coefficient of the average mass flow rate of the outlet throttle to the outlet throttle diameter deviation remains unchanged at 24.77. Cavitation occurs in the area of the outlet throttle when the spherical valve lift is 0.045 mm. The increase in rail pressure not only leads to an increase in the low-pressure area on the inner wall of the outlet throttle, an increase in the volume share of the gas phase, and an increase in the hydraulic impact on the sealing wall but also makes the average mass flow rate of the outlet throttle and the rate of change of the control chamber pressure during the opening of the spherical valve more sensitive to the deviation of the outlet throttle diameter.

Fuel cavitation can cause damage to the structure of an injector control valve, which can further affect the service life of the injector. Therefore, it is of great importance to carry out research on the mechanism of cavitation in injector control valves. In this study, the dynamic evolution of the cavitation and fuel flow characteristics during the opening of a ball valve in a high‐pressure common rail injector control valve were studied. First, a transient CFD simulation of the cavitation during the opening of the control valve was performed using dynamic mesh technology to analyze the evolution and formation mechanism of the cavitation. The cavitation was influenced by the fuel flow velocity, which was affected by the sealing cone angle and the ball valve movement. Additionally, the fuel reflux could effectively inhibit the development of cavitation. By comparing with the pressure, velocity, and mass flow rate of the fuel under conditions without cavitation, it was found that the cavitation had a remarkable effect on reducing the hydraulic shock to the ball valve and sealing cone as well as stabilizing the fluctuation of the fuel velocity in the control chamber. In addition, the cavitation noticeably decreased the fuel mass flow rate (by up to 32% at 0.015 ms) and increased the average pressure in the chamber (by up to 29.1% at 0.01 ms), ultimately leading to a slower response of the control valve. The analysis of different inlet pressures of the control valve indicated that the increase in the inlet pressure caused the cavitation to extend upward along the sealing cone, and that the cavitation ring area and the cavitation strength increased.

Based on the introduction of opposed-piston two-stroke (OP2S) gasoline direct injection (GDI) engines, the OP2S-GDI engine working principle and scavenging process were analyzed. GT-Power software was employed to model the working process based on the structural style and principle of OP2S-GDI engine. The tracer gas method and OP2S-GDI engine experiment were employed for model validation at full load of 6000 rpm. The OP2S-GDI engine scavenging system parameters were optimized, including intake port height stroke ratio, intake port circumference ratio, exhaust port height stroke ratio, exhaust port circumference ratio, and opposed-piston motion phase difference. At the same time, the effect of the port height stroke ratio and opposed-piston motion phase difference on effective compression ratio and expansion ratio were considered, and the indicated work was employed as the optimization objective. A three-level orthogonal experiment was applied in the calculation process to reduce the calculation work. The influence and correlation coefficient on the scavenging efficiency and delivery ratio were investigated by the orthogonal experiment analysis of intake and exhaust port height stroke ratio and circular utilization. The effect of the scavenging system parameters on delivery ratio, scavenging efficiency and indicated work were calculated to obtain the best parameters. The results show that intake port height stroke ratio is the main factor for the delivery ratio, while exhaust port height stroke ratio is the main factor to engine delivery ratio and scavenging efficiency.

The scavenging process for opposed-piston folded-cranktrain (OPFC) diesel engines can be described by the time evolution of the in-cylinder and exhaust chamber residual gas rates. The relation curve of in-cylinder and exhaust chamber residual gas rate is called scavenging profile, which is calculated through the changes of in-cylinder and exhaust chamber gas compositions determined by computational fluid dynamics (CFD) simulation. The scavenging profile is used to calculate the scavenging process by mono-dimensional (1D) simulation. The tracer gas method (TGM) is employed to validate the accuracy of the scavenging profile. At the same time, the gas exchange performance under different intake and exhaust state parameters was examined based on the TGM. The results show that the scavenging process from 1D simulation and experiment match well, which means the scavenging model obtained by CFD simulation performs well and validation of its effectiveness by TGM is possible. The difference between intake and exhaust pressure has a significant positive effect on the gas exchange performance and trapped gas mass, but the pressure difference has little effect on the scavenging efficiency and the trapped air mass if the delivery ratio exceeds 1.4.

This paper presents a simulator model of a diesel engine with a turbocharger for hardware-in-the-loop (HIL) applications, which is used to obtain engine performance data to study the engine performance under faulty conditions, to assist engineers in diagnosis and estimation, and to assist engineers in model-based calibration (MBC). The whole diesel engine system is divided into several functional blocks: air block, injection block, cylinder block, crankshaft block, cooling block, lubrication block, and accessory block. The diesel engine model is based on physical level, semi-physical level and mathematical level concepts, and developed by Matlab/Simulink. All the model parameters are estimated using weighted least-squares optimization and the tuning process details are presented. Since the sub-model coupling may cause errors, the validation process is then given to make the model more accurate. The results show that the tuning process is important for the functional blocks and the validation process is useful for the accuracy of the whole engine model. Subsequently, this program could be used as a plant model for MBC, to develop and test engine control units (ECUs) on HIL equipment for the purpose of improving ECU performance.

In opposed-piston, opposed-cylinder (OPOC) two-stroke diesel engines, the relative movement rules of opposed-pistons, combustion chamber components and injector position are different from those of conventional diesel engines. In this study, the combustion and emission characteristics of the OPOC which is equipped with a common-rail injection system are investigated by experimental and numerical simulation. Different split injection strategies involving different pilot injection/fuel mass ratios and injection intervals were compared with a single injection strategy. The numerical simulation was applied to calculate and analyze the effect of split injection strategies on the combustion and emission after validation with the same experimental result (single injection strategy). Results showed that using split injection had a significant beneficial effect on the combustion process, because of the acceleration effect that enhances the air-fuel mixture. Additionally, the temperature of the split injection strategies was higher than that of single strategy, leading to the nitrogen oxides (NO_x) increasing and soot decreasing. In addition, it has been found that the split injection condition with a smaller pilot injection/fuel mass ratio and a medium injection interval performed better than the single injection condition in terms of the thermo-atmosphere utilization and space utilization.