Previous studies have shown that increase compression ratio (CR) is an effective way to improve thermal efficiency of gasoline engine without changing the mechanical structure and working cycle, however, it is limited by engine knock when increasing the intake boosting under high load operation. This study aimed to solve the knock problem of gasoline engine with higher CR by application of Miller cycle, which can be implemented by either early or late intake valve closing (EIVC or LIVC). Therefore, in this paper, based on the engine with CR of 13.5 and electromagnetic valves train (EMVT), a comparative study was carried out to investigate the effects of EIVC and LIVC on engine performance, by theoretical modeling and calculation. The results show that, at high load, EIVC strategy is more preferred than LIVC owing to its lower total power consumption, which can improve the indicated mean effective pressure (IMEP) by 0.0371 bar, while enhance turbulence intensity and improve combustion. And at part load, the advantage for EIVC declines gradually, nevertheless, it can still sensitively adjust the EGR rate and thus reduce NOx. This results of quantitative analysis about two Miller cycles can provide valuable reference for engine designers and researchers.

No abstract

In this article, a drum type of transmission device has been developed, which is a double-layer cylinder structure. The working clearance between the inner and the external layers of the device has been filled with intelligent material named magneto-rheological fluid. To use it for tension regulation, theoretical model of its output torque has been constructed based on Bingham's theory, and the coupling relationship between mechanical structure, electromagnetic circuit, and magneto-rheological fluid is analyzed and simulated using finite element analysis. Higher flux is directed onto the magneto-rheological fluid and greater shear frictions are generated subsequently. The design is practical, and a special seal mechanism which is a combination of magnetic seals and labyrinthine seals is applied in this research to improve sensitivity and to reduce leakage of the device. Then, experiments on prototype indicate that this device has significant advantages of quicker response, larger output, and less heat compared to traditional magnetic particle clutch and some existing disk-type magneto-rheological brakes which were recently reported. The new device may be applied widely in the related winding tension control field in the future.

This paper aims to solve the problem of incomplete cleaning for blind hole remanufacturing blanks and damaging the matrix material in the cleaning process, a novel cleaning method by supercritical n-butanol is proposed. The feasibility of cleaning blind hole remanufacturing blanks is verified, and the mechanism of supercritical n-butanol cleaning is analyzed. The surface cleanliness of matrix structure, the properties change of matrix material and the environmental impact of the cleaning process are explored. The results indicated that there were no contaminants on the surface of cleaned matrix structure under the temperature 300°C, pressure 5.5 MPa, and cleaning time 10 min. Hardness, yield strength and tensile strength of matrix material after cleaning could increase by approximately 14%, 8%, and 5%, respectively. Compared with subcritical water, the oxidation degree of matrix structure cleaned by supercritical n-butanol was lower. Compared with high-temperature cleaning, seven environmental indexes of supercritical n-butanol cleaning process decreased significantly. Supercritical n-butanol cleaning is an ideal choice for blind hole remanufacturing blanks.