Octahedral media made of MgO–5%Cr2O3, with edge lengths of 18, 14, and 10 mm are used as pressure cells in experiments in a multi-anvil solid media apparatus at pressures of 4 to 27 GPa and temperatures to > 2700 °C. Calibrations of press-load versus sample pressure are based on room-temperature and high-temperature phase transitions, and are accurate to within ± 0.5 GPa. Calibrations of the temperature distribution were made in the central portion of the furnaces (graphite or LaCrO3) in the various sample assemblies used routinely in this laboratory. The following gradients away from the furnace midlines were observed: 18 mm: high-T straight graphite (−100 °C mm−1), high-T stepped graphite (+ 25 °C mm−1), low-T stepped graphite (−20 °C mm−1), high-T stepped LaCrO3 (−50 °C mm−1); 14 mm: high-T stepped LaCrO3 (−70 °C mm−1); 10 mm: straight LaCrO3 (−200 °C mm−1). The effect of increasing the wall thickness of the central segment of the furnace ("stepping") is to reduce the temperature gradient relative to a straight design. The relative effect of pressure on W3Re–W25Re and Pt–Pt13Rh thermocouples was measured by comparison of apparent temperatures recorded by each type in a given experiment. Corrections for the effect of pressure on thermocouple emf depend on the temperature distribution in the gasket regions surrounding the pressure cell, where pressure is reduced to ambient conditions. The temperature of this pressure seal controls the magnitude of the effect of pressure on thermocouple emf. Because this temperature will vary depending on the assembly, no universal pressure correction can be derived.

In this article, a mathematical fluid–structure–thermal model for fuel leakage of piston couples was developed, with consideration of the physical properties of fuel, elastic deformation, and temperature distribution along the seal length. The calculated results were compared with experimental static fuel leakage data. Based on this model, the effects of various factors on the fuel leakage were investigated. The results showed, at pressures under 100 MPa, the most dominant influence on the fuel leakage of a piston couple was the initial clearance; however, as the pressure increased from 100 to 200 MPa, the influence of the initial clearance gradually weakened, while the effects of the piston diameter, elastic modulus, and diameter of the piston sleeve increased and became more significant; in this case, the piston diameter replaced the initial clearance as the most dominant factor. At a pressure range of 200–300 MPa, the effects of the elastic modulus exceeded the effects of the initial clearance and became the second most important factor. Therefore, simply adjusting the initial clearance is not an effective method to reduce fuel leakage. An increase in the seal length significantly influences the fuel leakage only under relatively low-pressure conditions, as the effect weakens with increasing pressure. As a result, under high-pressure conditions, it is necessary to consider both the diameter of the piston and the elastic modulus to reduce the fuel leakage.

A high-speed solenoid valve (HSV) with high dynamic responses is a key component of the common rail injector, where it provides accurate and flexible control of the injection. In this study, finite element methods were used to investigate the eddy current inside an HSV. The results demonstrated that the appearance and change in the eddy current were related to the driving current, and significantly influenced the HSV dynamics, particularly the opening response. By considering the eddy current effect, the calculations were seen to match the experimental data effectively during the opening response, but did not match them strongly during the closing response. During the HSV opening process, the eddy current at the surface of the magnetic materials impeded the magnetization; during the closing stage, it prevented the magnetic flux inside the magnetic material from spreading out and delayed demagnetization. An eddy current was proven to always block the magnetic field change and worsen the HSV dynamic response. Slotting on the yoke can significantly reduce the open response time, while hardly influence the close response. It was deemed necessary to optimize the HSV structure to weaken the eddy current effect on the opening and closing response.

No abstract

In our study, the B–H magnetization curves at temperatures between 16 and [Formula: see text] and frequencies between 50 Hz and 1000 Hz were measured to analyse the effect of temperature and frequency on the magnetization characteristics of electrical iron DT4C. By researching a high-speed solenoid valve (HSV) for a common rail injector, the temperature and frequency dependence of DT4C and their effects on the electromagnetic force and dynamic response of a HSV were obtained. The research results showed that an increase in temperature could decrease the magnetic flux density; however, the decrease was not apparent. The effect of temperature on the relative permeability depended on the range of magnetic flux density B. The temperature dependence of DT4C was weak in the temperature range of 16--150[Formula: see text]. This stability of magnetic characteristic of DT4C ensures that the dynamic response of a HSV could be maintained well for a common rail injector. Magnetization frequencies had a significant influence on the magnetization of DT4C. An increase in the frequency would delay the transition to the saturation magnetic flux density Bs. The effect of frequency on the electromagnetic force became increasingly significant as the driving current increased. In a frequency range of 50–200 Hz, the opening response time of a HSV could be maintained well. When the frequency was higher than 200 Hz, the opening time increased significantly with the frequency raised from 200 Hz to 1000 Hz, furthermore, the HSV was out of control and closed ahead of time.