Advanced Materials Research Vols. 383-390

Abstract: An attempt was made to study the hot corrosion behavior on gas tungeten arc welded Austenitic stainless steel AISI 304 and Nickel-copper alloy Monel 400. These materials are widely used in power plant, petro-chemical and marine applications where the weldments are usually subjected to aggressive corrosion environment. GTA welding was carried out using ENiCu-7 and E308L filler wires. Various regions of the weldment of AISI 304, Monel 400 were exposed to the air oxidation as well as in the molten salt environment consist of K₂SO₄ + NaCl (60%) at 700°C. Mechanical properties of the weldments were also studied. The corrosion products of the weldments were analyzed using SEM/EDAX, XRD analysis.

Abstract: Monel 400 is nickel-copper alloy being widely in thermal and nuclear power plants, marine environments because to its outstanding properties include high ductility, good weldability and good corrosion resistance. In the present investigation, an attempt was made to evaluate the mechanical properties of gas tungsten arc welded Monel 400 weldments. Also Monel 400 weldment was studied for the pitting corrosion behavior.

Abstract: Bimetallic welds (BMWs) have been a necessity within the steam generators of nuclear power plants, where the heavy section low alloy steel components are usually connected to stainless steel primary piping systems. These welds represent zones with metallurgical discontinuities, which tend to localize the strains and cause failures. The other critical issues which must be taken care of while welding of bimetallic joints include solidification cracking, thermal fatigue and residual stresses in welds. The occurrence and severity of all these problems associated with bimetallic welds depend upon the type of welding process used along with the other variables like welding consumables, heat input etc. In shielded metal arc welding (SMAW), welding electrode consumables/coatings play an important role in deciding the weld metal quality. The development of welding electrode coatings is quite difficult due to very rapid complex reactions taking place during welding and the involvement of many controlled process variables. The present paper is an effort to highlight the general issues and challenges for the systematic and scientific development of welding electrode coatings for bimetallic welds. The experimental procedure contains three sets of coated electrodes having varying ferro-alloys, silica and carbon content. In the first set of electrodes, non-ferrous elements are also introduced into the weld metal through flux addition. Further, the welded joints are subjected to various tests and then evaluated to ascertain their mechanical as well as metallurgical behaviour.

Abstract: Hydrogenated amorphous silicon (a-Si:H) thin film has nowadays attracted much attention in a wide range of electronic applications as in image sensors and in solar cells because of its merits and compatibility with semiconductor technology. In this paper, the background of a-Si:H thin film technology and microbolometer technology has been described in details. According to optical admittance matrix method, the multilayer film system based on a-Si:H thin film was simulated by MatLab software, mainly for the simulation of infrared absorption layers and the simulation of microbolometer. The results show that the combination of TiN film and a-Si:H film is suitable for the design of microbolometer within the middle and far infrared wave band (8-14µm), and the infrared absorptivity of the modified microbolometer can reach over 90%.

Abstract: his paper is concerned with the fuel economy of a mini car with power split automatic transmission (PSAT) by means of simulation. Firstly, a PSAT prototype is developed featured with high efficiency by power split. Secondly, mathematic models of PSAT, based on the PSAT scheme and experiment on the prototype, is established and embedded into the simulation software NREL’s Advanced Vehicle Simulator (ADVISOR) to carry out the whole vehicle fuel economy simulation. Thirdly, fuel economy comparison between vehicle with PSAT and traditional mechanical transmission is present, after fuel economy simulation under different driving cycle. Finally, approach to the energy save scheme of PSAT and matching between PSAT and the whole vehicle is discussed which builds up a good foundation for future optimization on control strategy of PSAT.

Abstract: In order to ensure the reliable and safe operation of the electric driving motor of the articulated dump truck, water cooling system is installed for each motor. For the best performance of the water cooling system, not only the heat transfer should be enhanced to maintain the motor in relatively low temperature, but also the pressure drop in the water cooling system should be reduced to save energy by reducing the power consumption of the pump. In this paper, the numerical simulation of the cooling progress is completed and the temperature and pressure field distribution are obtained. The multi-objective optimization model is established which involves the cooling system structure, temperature field distribution and pressure field distribution. To improve the computational efficiency, the surrogate model of the simulation about the cooling process is established based on the Response Surface Methodology (RSM). After the multi-objective optimization, the Pareto optimal set is obtained. The proper design point, which could make the average temperature and pressure drop of the cooling system relative desirable, is chosen from the Pareto optimal set.

Abstract: With the target of voltage quality, an improved PSO algorithm is proposed in reactive power optimization(RPO) of power system. The algorithm adopts some way of chaos theory and flexible inertia weight based on basic PSO and suitable penalty factor on function constraint, which can overcome limitations of partial constringency in basic PSO and improve the efficiency in global optimizing. The simulation of IEEE-14-buse shows this algorithm has better convergence than basic PSO algorithm.

Abstract: For a give air flux, the higher speed the fanner is running, the smaller the fanner’s size is. It is also well known that for a given power, the higher the machine’s running speed, the smaller the machine’s size has. If the fanner is geared to a high speed machine directly, the fan set’s volume will be sharply decreased. However, the heat dissipation of the high speed machine becomes a serious problem also due to the small size and high power loss density. Therefore, how to estimate accurately the power losses and temperature rise is a key issue for the high speed machine design. In this paper, the power losses and temperature of high speed PM machine for a fanner application are thoroughly investigated. And the test results of a prototype fan set partly shown the validity of the calculation method.

Abstract: Power system load shedding has been used as an emergency control method to prevent possible power system instability problems. In this paper, a new multi-stage model predictive control based load shedding scheme is proposed to enhance long term voltage stability of a power system. The main advantage of this new method is the capability of the scheme to handle multi-stage control actions, which may also be disturbances to a power system at a critical status toward instability. A new cost function is defined for the model predictive control scheme. The proposed scheme is tested on the New England 39-bus system to validate its efficiency and effectiveness in preventing system long term voltage stability problems.

Abstract: This article mainly presents the method of carrying out Manchester’s coding, transmitting and surface decoding for the downhole data based on complex programming language device EPM1270T144I5 chip (CPLD). It also presents the main components of new intelligent layered water injection regulating and testing system, the overall scheme design on data transmission, and the software simulation in QuartusⅡ for ManchesterⅡ encoding as well decoding. The actual application shows that the technology features stable and reliable for data transmission and acceptance, thus it is greatly simplifying the system’s circuit, improving its whole performance.