Yunxi Shi

Influence of PM Size Distribution and Ingredients on DPF Regeneration by Non-thermal Plasma Technology

Experimentation was conducted to analyze the diesel particulate filters (DPF) trap under four different engine loads with particle size analysis and thermo-gravimetric analysis introduced to characterize particulate matter (PM) samples. DPF regeneration was achieved utilizing an oxygen-fed non-thermal plasma (NTP) injection system. Results indicated that accompanying the increase of engine load, the concentration of nucleation mode particles decrease while that of accumulation mode particles and the total concentration number increase at first and then decrease with the total concentration number of PM peaking at 50% load. H2O and soluable organic fraction in PM demonstrate a downward trend while dry soot exhibits an upward trend in mass fraction with the increasing load. NTP may then separate PM into CO and CO2. Size distribution and ingredients of PM trapped by DPF under different loads vary, thus the intensity of reaction between PM and radical gases produced by NTP is different. C1 (C in CO) exhibited a declining trend with the increasing of engine load, while C2 (C in CO2) and C12 (sum of C1 and C2) increase first and decrease after. Mass of PM removal maximizes at 50% load while DPF regeneration effect is the most remarkable.

Experimental study on optical-thermal associated characteristics of LED car lamps under the action of ionic wind

Abstract The working temperature of a LED chip has a great influence on its photoelectric properties. This paper is concerned with the application of ionic wind produced by corona discharge to cool a LED car headlamp. Both theoretical and experimental procedures are studied. A DC ‘needles-to-mesh’ ionic wind generator was designed for the experimental study. The mechanism of the association between optical and thermal properties was explored. The results indicated that the ionic wind could weaken the red shifting of the chromaticity coordinates and reduce the radiant power. It also showed a better working performance when the corona discharge power increased, but it only changed slightly as the corona power continued increasing. Ultimately, it would result in more symmetrical and uniform light distribution and the illumination gradient varied gently, which was more suitable for the driving beam lighting. The luminous flux was 1957.6 lm and the junction temperature was 29.8 °C after 6 min working of the ionic wind generator under a corona discharge power of 3 W. All the test values complied with the regulatory requirements.

Effect of polyoxymethylene dimethyl ethers on particle properties and diesel particulate filter regeneration

The emission tests were performed on a light-duty direct injection diesel engine. A polyoxymethylene dimethyl ethers (PODE) mixture was blended with diesel at a volume ratio of 0, 10, 20 and 30%, denoted as P0, P10, P20 and P30, respectively. The particle size distribution before and after the diesel particulate filter (DPF) was measured to evaluate the DPF filtering efficiency of various modal particles. The oxidation activity of the particles on the DPF intake end plane was analyzed by the Arrhenius method. The regeneration of the DPF was conducted using a non-thermal plasma (NTP) injection system. The results showed that blending PODE with diesel contributed to reducing the particle number concentrations. PODE adversely affected the improvement of the DPF filtering efficiency, especially that of P30. However, the DPF filtering efficiency of all fuels was still higher than 94%. Blending PODE with diesel increased the mass fraction of volatile substances (VS) and decreased the mass fraction of dry soot. Particles of P20 showed a better oxidation activity with lower apparent activation energy. In addition, PODE increased the DPF regeneration effect by NTP technology. The deposit removal mass of the DPF rose to the peak level and then decreased as the PODE blending ratio increased. The better DPF regeneration effect was observed when P20 was employed.