Advanced Materials Research Vols. 614-615

Abstract: For diesel particulate filter (DPF) drop-to-idle uncontrolled regeneration, a regular regeneration is initiated following a vehicle stop while the engine switches to idle. The increase in oxygen concentration and the decrease in exhaust flow rate can result in a sharp exotherm in the filter and high temperature to damage the substrate. In this paper, control solutions for the idle thermal protection of the filter was proposed and validated experimentally. At high idle speed of 2200rpm, increasing exhaust gas recirculation (EGR) combined with intake throttling was a practical way to reduce available oxygen content to control the exothermal reaction rate. A much lower peak temperature was obtained for safe DPF regeneration during idle. The research would provide based information for optimizing the regeneration management strategy in order to avoid DPF failure in real world operation.

Abstract: The efficiency of engine-pump units and fuel supply capacity are related closely, which drop strongly in the plateau. In order to find out the relationship between engine-pump units performance parameters and natural conditions in the plateau, this research dealt with the specific forms of engine-pump units efficiency descend, analyzed the influence factors of engine-pump units efficiency, found out the decline rules of engine-pump units power, emission and reliability. The result shows that atmospheric pressure, temperature and altitude are the most important influence factors, based on the conclusion, some methods were put forward to improve the engine-pump units efficiency.

Abstract: Three-dimension transient numerical simulation of flow field in the transfer ports , exhaust port, intake port, crankcase and cylinder system of two-stroke gasoline engine was studied by using CFD software Fire, and the situations of airflow movement and exhaust gas distribution were presented dynamically in the scavenging process. The results show that flow field structure of the upper cylinder is mainly comprised of a pair of toroidal vortex and tumble vortex, while flow field structure of the lower cylinder is mainly comprised of four radial swirls and "short-circuiting" fuel losses. Along with the progress of scavenging process, the area of fresh charge and mixture increase while the exhaust gas area decreases accordingly. When the piston reaches to the BDC (bottom dead center), the exhaust gas area almost disappears.

Abstract: According to the detailed chemical kinetic mechanism of ethanol proposed by the U．S．Lawrence Livermore Laboratory, this paper analyzes the main approach of ethanol oxidation. Based on the detailed chemical kinetics mechanism, a skeletal chemical reaction mechanism is presented by reaction path analysis．Thus a simplified model is constructed, which consists of 26 species and 26 reactions．And then the comparative studies were given between the simplified model and the detailed model．The simulation results show that simplified model and detailed model have good consistency.

Abstract: Based on the equation that the heat conduction from the bubble underlying layer is balanced with the heat convection of bubble cooling and the latent heat of evaporation, with the help of zhao model a new bubble growth model for the forced convective subcooled boiling in the engine cooling system is developed with the consideration of the thermal boundary layer impact on the bubble growth. And an experiment is designed to verify the theoretical model. Then the Klausner model for predicting the bubble lift-off diameters is amended with the built bubble growth model. In addition, the bubble lift-off diameters at the different velocity are predicted, which is verified with the experimental data.

Abstract: On the base of analyzing the parametric design model of the screw feeder with variable diameter and screw pitches, a parametric design model of screw shaft was given in this paper. By choosing biomass material in a pocket between adjacent flights as the study object, the force between bulk material and five contact surfaces were analyzed during the conveying process, and a mechanical model for biomass screw feeders was built up. Meanwhile, a theoretical method to calculate torque of screw shaft with variable diameter and screw pitch was provided. The theoretical method could be also used in calculating torque for screw shaft with unchangeable pitch and diameter.

Abstract: Improvement of no-load voltage waveform is a important problems for designing hydro-generators and ensuring operation reliability of the generators and electric network. The no-load voltage waveforms of a 335MW hydro-generator are optimized with the design scheme which shift damper winding and skew stator slots, and the computations are implemented and analyzed by the multi-slice moving electromagnetic field-circuit coupling model of the hydro-generator The results show that the waveforms of the no-load voltage are improved observably when reasonable shift damper winding and skewing stator slots. The calculation results are coincident well with the test data. The research is helpful for improving design standard and enhancing the operation reliability of the large hydro-generator and electric network.

Abstract: A double ω-combustion chamber matched with a double-row nozzle combustion system was proposed to improve the spray space distribution and the mixture formation quality for diesel engines. The cylinder spray, mixture formation and combustion process of a double ω-combustion chamber were simulated by using AVL FIRE software. With different nozzle angles, the effect of which on air velocity, concentration and temperature fields as well as combustion and emission characteristics in the combustion chamber was analyzed. The results show that the spray angle of the nozzle has a great influence on combustion and emission performance. Using the double-row nozzle injector can effectively improve the quality of the mixture, moreover, compared with single-row nozzle injector, the max soot emission was reduced by 57.8% and the ultimate formation was also lower.

Abstract: In order to solve the blindness of the parameter selection in the Support Vector Regression (SVR) algorithm, we use the Fruit Fly Optimization Algorithm (FOA) to optimize the parameters in SVR, and then propose the optimization algorithm on the parameters in SVR based on FOA to fitting and simulate the experimental data of the turbine’s failures. This algorithm could optimize the parameters in SVR automatically, and achieve ideal global optimal solution. By comparing with the commonly used methods such as Support Vector Regression and Radial Basis Function neural network, it can be shown that the forecast results of FOA_SVR more accurate and the forecast speed is the fastest.

Abstract: Cam signals, crankshaft signals and angle signals were simulated by analogue crankshaft position sensors developed by C8051F series micro processors to emulate the operational environment of motorcycle engine. In the software development platform of gasoline engine, software running status of control system was tested. MP424 high-speed sampling card was applied to actually observe properties of ignition advance angle and fuel injection advance angle. The experiment suggested that practically observed fuel injection pulse width, ignition pulse width, properties of ignition advance angle and fuel injection advance angle were the same as those of models of control system software. This proved that the analogue crankshaft position sensor that has been developed is practical and feasible.