Xiao Hua Li

Experimental Study on the DPF Regeneration Based on Non-Thermal Plasma Technology

Diesel particulate filter (DPF) are considered to be the most effective means to reduce particulate emissions, and the key of DPF lies in their regeneration. O3 and O which have strong oxidability can be produced by non-thermal plasma (NTP) reactor. PM can be decomposed by these active substances to generate CO and CO2. The results show that PM deposited in the DPF can be removed by NTP technology without any catalyst and DPF can be completely regenerated at a lower temperature.

Optimization of Biomass Vacuum Pyrolysis Process Based on GRNN

Biomass pyrolysis for preparing bio-oil was studied on the vacuum pyrolysis system, where rape straw was chosen as the raw material. The experiment was designed by orthogonal method. And pyrolysis temperature, system pressure, heating rate and holding time were chosen as input variables to establish the prediction models about bio-oil yields and energy transformation ratio based on Generalized Regression Neural Network. The parameters of vacuum pyrolysis system were optimized for maximizing bio-oil yields and energy transformation ratio, and the optimization result was verified by experiment. The results of research show that the predicted values are fit well with the experimental values, which verifies the effectiveness of the prediction models. When pyrolysis temperature is 486.8°C, system pressure is 5.0kPa, heating rate is 18.1°C/min and holding time is 55.0min, bio-oil yield is 43.6% and energy transformation ratio is 35.5%. Both are close to the maximum, and the result is accurate by experimental verification.

Thermo-Gravimetric Analysis and Kinetic Study of Biomass Pyrolysis

In order to realize the optimization of pyrolysis process, the pyrolysis characteristics and kinetics of common agriculture and forestry biomass were studied. Four kinds of biomass were chosen as experiment materials for thermo-gravimetric experiment. The Characteristics of biomass pyrolysis was studied by defining a new evaluation methodology. The method of Coats-Redfern was used to analyze pyrolysis kinetics of biomass pyrolysis process. The results of research show that the pyrolysis process of biomass can be divided into three stages, including drying and preheating, fast pyrolysis and slow decomposition of residue. The activation energy of pyrolysis reaction of biomass during the low temperature stage is higher than that of the high temperature stage. The values of the activation energy and pre-exponential factor are increasing with the increase of heating rate. The pyrolysis of biomass in the main pyrolysis zone can be effectively described by using the kinetic model n=2. The heating rate of 15K/min and temperature of 500°C can improve the reaction rate, and it helps to reduce energy consumption of the reaction.

Thermal Design of Automotive Headlamp with High Power LED

With an urgent need for energy conservation and pollution reduction, the trend of replacing traditional incandescent or fluorescent lamps with high-power LEDs is growing more and more popular. However, heat dissipation of high-power LED is the main bottleneck for its application. In this research, a kind of automotive headlamp low beam system model is designed with high power LED chips. Several different cooling devices are designed for headlamp cooling, the heat dissipation performances are simulated and analyzed both by the finite volume method (FVM) in FloEFD and experimental measurements. The obtained results indicate that loop heat pipe combined with fined heat sink is the most effective way for heat dissipation in the designed automotive low beam system, even in 80¡æ environmental temperature can ensure the LED headlamp system working stability. The research lays a theoretical basis for the follow-up study.

Removal of Carbonyl Compounds in Diesel Exhaust Gas by Direct Non-Thermal Plasma

The variation of carbonyl compounds in diesel exhaust at four loads before and after the treatment of Direct Non-thermal Plasma (DNTP) is studied with 2,4-dinitrophenylhydrazine (DNPH) derivatization method and high performance liquid chromatography (HPLC) analysis technique. The results show that the mass concentration of carbonyl compounds decreases firstly and then increases with the growing of diesel load before the treatment of DNTP. After the treatment of DNTP, the mass concentration of carbonyl compounds reduces remarkably. Maximum removal efficiency for total carbonyl compounds can reach 93.8% at 75% load. For acrolein, acetone, butyraldehyde and 2-butanone, removal efficiency can reach 100% at 25% load, 50% load and 100% load. At the same time, total ozone formation potential decrease dramatically.

The Effects of Stack Parameters on the Performances of Acoustic-Refrigeration Thermoacoustic Conversion System

In this research, the acoustic-refrigeration thermoacoustic conversion system numerical model was constructed, the combined influences of structural and positional parameters of stack on the temperature difference at two ends (DT) and the coefficient of performance (COP) were analyzed. Besides, the acoustic-refrigeration thermoacoustic conversion test system was built up. Finally, experiments were performed to testify the calculation results of the conversion system. The results showed that within the common ranges of the parameters values, the porosity of stack affected the COP slightly while the temperature difference seriously, the temperature difference at the two ends of stack increased with the increase of the porosity of stack; for stacks which have the same porosity and gaps between each parallel plate, two values for the center position of stack were exist of which one could make the temperature difference get to the best value, the other one made the COP achieve the maximum value; when the porosity and the center position of stack remained constant, the temperature difference increased first and decreased afterwards with the increase of the gaps height between each parallel plate. In the selected model, the temperature difference at the ends of stack got an ideal value when 2y0=0.45 mm (the gaps height between each parallel plate was nearly about 2.4 times than thermal penetration depth). The results provided the theoretical basis and experimental evidences for improving the performance of acoustic-refrigeration thermoacoustic conversion system.

Experimental Analysis on Characteristics of a Water-Cooled Non-Thermal Plasma Reactor

Characteristics of a water-cooled non-thermal plasma (NTP) reactor used to reduce diesel emissions were experimentally studied. The effects of working voltage, operating frequency and air flow rate on discharge power and concentrations of O3 and NO2 generated by NTP system were investigated at different surface temperatures of discharge zone. The experimental results show that, the discharge power of the reactor would increase with the increasing of working voltage, operating frequency and surface temperatures; air flow rate had little influence on discharge power; variation of O3 and NO2 concentration were different with the increasing of working voltage and operating frequency at different surface temperatures of discharge zone; when the surface temperature of discharge zone was constant, concentrations of O3 and NO2 increased firstly and then declined with the increasing of air flow rate; and concentrations of O3 and NO2 were higher at lower temperature.

Experimental Investigation on Effect of Stack on Thermoacoustic Conversion System Performance

The thermoacoustic conversion system is designed, while the position and structure parameter of stack are calculated and analysed. At the same time, the parameters of stack and the input working frequency which influence the system are researched by experiment. The results show that the center position of stack in the standing-wave tube and the length of stack have great influence on the system, and exists a best value in the same input power and frequency; Meanwhile, the pore diameter and wall thickness of stack are also exist the best values, the temperature difference at both ends of stack will be reduced if the value is too big or too small; The best working frequency of the system is migrated due to the stack, working fluid and so on.

Optimal Design of Cooling Device for High Power LED Headlamp

The aim of this study is to optimize the cooling device for high power LED headlamp. The feasibility of using SMD (Surface Mounted Devices) resistor instead of LED chips has been analyzed by FloEFD and the relationship between temperature and total input power has been found. In order to evaluate the cooling performance of the heat pipe, two different arrangement forms has been used. Based on the simulation, heat pipe arranged in rectangle can satisfy the requirement of high-power LED headlamp. These results also laid a theoretical foundation for later experiments.

Free Modal Experiment and Analysis of 4105 Diesel Engine Crankshaft Torsional-Bending Coupling Vibration

In order to research the principle of crankshaft horizontal-bending vibration, free modal experiments of 4105 diesel engine crankshaft vibration was designed and done. Vibration parameters of free vibration, torsional vibration, vertical-bending vibration and horizontal-bending vibration were obtained respectively through different measurements points setting and motivation techniques. Through analysis of frequencies and models, a conclusion was drawn:the torsional vibration was just coupling with the horizontal-bending vibration.