Applied Mechanics and Materials Vols. 229-231

Abstract: Most motorcycles in developing countries use carburetor systems as the fuel delivery method especially for models with the cubic capacity of less than 125cc. However, small gasoline fuelled engines operating using carburetor system suffer from low operating efficiency, waste of fuel and produce higher level of hazardous emissions to the environment. In this study, an electronic control unit (ECU) is designed and simulated for a retrofit fuel injection (FIS) system. The ECU is targeted to have a simple design, reliable and offers all of the necessary functions of the modern ECU. The simulation results shows that the designed ECU can determine the injection period as close to the proposed value and can drive the injector efficiently based on the generated PWM pulse.

Abstract: The main bearing dynamic characteristics of megawatt wind turbines are complex system with strong non-linearity, strong coupling and time-varying. The vibration signals are mixed with background noise, so it is difficult to extract the characteristics of week signals. Based on the dynamic characteristics, multi-fractal theory is put forward to detect and recognize the working status of the main bearing of megawatt wind turbines. Different working states are recognized intuitively by different dimensions of multi-fractural which are sensitive to variety of working state. The paper justifies the method can detect and recognize different working states of main bearings quickly and accurately through the experiments on the main bearings of 3 WM wind turbines.

Abstract: The purpose of this paper is to explore difference between the first thermal ignition and the secondary thermal ignition, and to reveal the variation rules of characteristic parameters and critical condition ignition for the secondary thermal ignition of gasoline-air mixture. In this paper, experimental investigation on the gasoline-air mixture secondary ignition induced by hot wall in model underground oil depots tunnel has been carried out. Compared to the first thermal ignition, the ignition intensity of the secondary thermal ignition is greater, while the ignition delay and duration are shorter. After the first thermal ignition extinguish, if the ambient temperature is in the range of 286K to 463K and hot wall’ temperature is in the range of 730 to 783K, then the relation between critical ignition temperature and the ambient temperature can be expressed by cubic polynomial. The critical ignition concentration of gasoline vapor is only 0.45% and that of oxygen is 10.4%.

Abstract: Energy scavenging device used for smart grid can achieve energy from electromagnetic field and convert it into electricity to power wireless sensors within substations. Due to the energy collected by the energy scavenging unit is unstable, a conditioning circuitry is essential. A conditioning circuitry is proposed, and modeling method is also established accordingly. Both large-signal model and dynamic disturbance model of the topology are presented as to analyze the static and dynamic characteristics. Remarkably, one duty cycle of the sensors is divided into the launch period and dormant period. At different period, their equivalent impedance is different, so the performance of conditioning circuit at different stages is analyzed. To realize it, a feedback control circuit should be considered in the design of the topology. Further, simulation based on PSIM is done to certify effectiveness of the proposed topology and optimized parameters.

Abstract: A capacitive energy harvesting device is proposed to harvest energy from electric field in substations. It can achieve electric energy from electromagnetic environment for wireless smart sensors. It’s obvious that the surface of it can generate charge when it’s put in the electric field. However, the output voltage of it is unstable and it cannot power directly the wireless sensors. So a conditioning circuit is essential for the device. With the purpose of designing and analyzing conditioning circuit, a simple model is used to equal the energy harvesting unit. In order to power the sensors steadily, the conditioning circuit should consist of some subcircuits such as AC-DC rectifier and DC-DC converter. At last, a simple digital temperature sensor is used to study the operating characteristics of the conditioning circuit in the stage of experiment.

Abstract: The Padé approximation is a very important description of thermodynamic properties of fully ionized hydrogen at high pressures and temperatures. By comparing of several reported Padé approximants via calculation of the ion-electron interaction contribution to the Helmholtz free energy of the fully ionized hydrogen plasma, we find that Padé approximant proposed by Stolzman gives an unphysical odd local minimal appears at low temperature( ), and gradually fade away with the increase of temperature, implying a prominent limit of low temperature. While Chabrier et al. developed a more reasonable Padé approximant for the contribution of ion-electron interaction on the Helmholtz free energy. Analyses on isotherm curves indicate that the thermodynamic properties of the ion-electron interaction contribution to the Helmholtz free energy described by the revised Padé approximant is very stable at all temperatures and pressures without any unphysical effects at low temperatures.

Abstract: Steam power system and production process are the important parts of the process industry. Steam power system provides the production process steam, electricity and other energy it needs, and the relationship between them is very close. In order to obtain the maximum benefit of the total plant, the integrated optimization of the production process and steam power system is very important. In this paper, the framework of the integrated optimization model is established. An iterative optimization method based on genetic algorithm is proposed to solve the integrated model. Simulation example shows the effectiveness of the proposed method.

Abstract: Based on a lot of tests, domestic based oil and additives were chosen according to the working characteristics of heavy duty and supercharged diesel in this paper. The nyctinasty of compound additive produced by American EXXON company and domestic CD-package to based oil was inspected respectively by tests[1]. Dealing with the datum of orthogonal test by computer, the three optimum formulates of 20w/40 heavy duty and supercharged diesel oil were presented.

Abstract: Based on the characteristics of high power diesel engines’ thermal balance analysis, a diesel engines’ thermal balance test and analysis system is developed through dealing a large number of test data. This system can real time monitor the temperature, pressure and flow rate of the components in cooling circuit, fuel circuit and gas circuit, can continuously record and store the state parameters, can realize theory computation, statistical analysis, query, and print data report. Also the system can realize remote operation. This system has already been operated in several enterprises. Results show that the system can estimate diesel engines’ thermal balance effectively. According to the analysis results, diesel engines’ designers can estimate the components that bearing excessively high thermal load and can solve the thermal balance problem of high power engines.

Abstract: To the oscillation and misjudgment problem of the traditional perturbation and observation algorithm, a novel three-point comparison method was proposed. This method applied Constant Voltage Tracking (CVT) method and variable-step perturbation method to solve the problem between tracking accuracy and speed, and applied double-direction perturbation method to make sure the reliability of action to avoid the misjudgment when external conditions fast changing. Restraining the oscillation near the maximum power point effectively was another merit of this proposed method. Finally, the experimental results demonstrate effectiveness of proposed method with PV experimental platform.