Applied Mechanics and Materials Vols. 672-674

Abstract: Reasons for boiler economizer tube corrosion were discussed based on results of macroscopic inspection, metallurgical microstructure examination, SEM and EDS fracture analysis. Results showed that the tube corrosion was due to sulfur corrosion that resulted in matrix exposure and led to further oxygen corrosion.

Abstract: Using water-source heat pump for recovering waste heat of thermal power plant circulating water, mining of low grade heat energy. It can improve the power efficiency of comprehensive energy, but also can reduce the evaporation cooling water, the heat and moisture discharge to the environment. It has the economic, social and environmental benefits are very remarkable. Through the analysis of 600MW thermal power unit circulating water waste heat and calculation of water source heat pump heating, the feasibility of the water source heat pump technology in the recovery of power plant circulating water waste heat can be obtained.

Abstract: This paper presents the circular-arc tooth profile that has no trapped-oil feature and flow fluctuations. The mathematical model of tooth profile and helical surface is obtained by gear engagement theory. The examination of helical surface is by coordinate measuring machining (CMM). The sections that perpendicular to the axis direction of gear are selected to obtain the trajectory of measuring ball by the starting points and end points of measuring ball. The examination process of CMM is simulated by Matlab in this paper.

Abstract: The rudder and steering gear is the most widely used ship maneuvering equipment. It consists of the maneuvering device, transmission mechanism, steering gear, steering mechanism and the rudder blade. MV "TANSUO HAO" is a scientific research ship of 30 years old. The scientific exploration missions require a very high accuracy of the ship’s course, so the ship has to constantly adjust her course and steer frequently. On that day, the duty officer found the steering gear failure to turn left in the rough sea condition. The engineering crew members had to make an emergency repair. It took plenty of time to locate the trouble of the steering gear in the repair process, because the valve plate deformation problem on the solenoid reversing valve was very hard to find out. By exploring the obscure steering gear failure reason and special troubleshooting process on MV "TANSUO HAO", this thesis provides some repair experience for the hydraulic system management and proposes flexible and patient failure analysis as well as some preventive maintenance measures against the problem.

Abstract: The nonlinear model of hydro turbine considering the elastic water column was proposed, and the improved biogeography-based optimization (IBBO) algorithm was applied to identify parameters of this model. The cosine species migration model and the elitist reservation strategy were introduced into the algorithm to improve operating efficiency. Based on measured data, comparison of the effects of different identification methods was presented, including the IBBO algorithm, genetic algorithm (GA) and particle swarm optimization (PSO). The results demonstrated that the IBBO algorithm can be applied in parameters identification of hydro turbine nonlinear model, and it has the advantages of faster convergence and higher precision.

Abstract: The Eulerian-Eulerian model and species transport method were used for the residence time distribution (RTD) predictions of the short-contact cyclone reactor. A video camera and colored particle tracer were employed in the experiment. The component concentration distribution and RTD characteristics were analyzed. The results indicate that the vacuum gas oil (VGO) and catalysts flow down spirally along the wall and the gasoline and dry gas are mostly in the central part, so the VGO has more contact time with catalysts than other gas components. The RTDs indicate that there exists vortex, backflow and other secondary flow in the reactor. The simulated results show a good agreement with the experimental data.

Abstract: The model of coupled exhaust hood with condenser throat and the model of coupled exhaust hood, condenser throat with last stage were simulated based on the turbulence model Realizable k-ε. Calculated results show that due to the ignoring of the inlet swirl in the model coupled exhaust hood with condenser throat, the flow field is symmetrical and the pressure loss is small. Due to the influence of last stage, in the model of coupled exhaust hood, condenser throat with last stage, the flow field of the inlet of the exhaust hood is uneven, and the vortexes changed more complex, resulting in the increase of the pressure loss of each part and a greater influence in the diffuser pipe. The proportion of pressure loss of diffuser pipe in total pressure loss increases from 0.086 to 0.358, and there is a 70% decline of proportion of pressure loss in volute and condenser throat. In addition, the proportion of the pressure loss in volute is the largest one in these two coupled models. So more attention should be paid in the influence of the last stage, and weaken the vortexes in the volute when designing or optimizing the exhaust passage of steam turbine.

Abstract: In PWM controlled variable rate spraying system, spraying quantities were regulated by fast switching solenoid valves. However, hydraulic impacts were generated by these fast switching solenoid valves in pipe system, which affected stabilities of spraying quantities and atomization characteristics. In order to study pressure changing regularities when solenoid valves operated, then to design a pressure controller to improve spraying qualities in PWM controlled variable rate spraying system, Fluent was used to simulate pressure characteristics in the pipe system and pressure curves were drawn under the following 3 working conditions, solenoid valve opening, closing, and switching continuously with 5 Hz frequency and 50% duty ratio. Related experiments were carried out to test real pressure signals in the pipe based on a PWM controlled variable rate spraying system. Relative errors between simulation results and experiment results were below 10%. Thus, this simulation model of PWM controlled variable rate spraying system in Fluent was reliable to simulate pressure characteristics in the pipe in other common working conditions, and which contributed to design pressure controller and to optimize the whole PWM controlled variable rate spraying system.

Abstract: An externally pressurized deep/shallow pockets hybrid journal floating ring bearing compensated by flat capillary restrictor which can meet the need of high speed rotating machinery is presented in this paper. Bases on turbulent flow theory, the equations governing the flow of inner and outer fluid film in the journal floating ring bearing are established. The control equations together with the pressure boundary condition and the restrictor flow equation are solved by using the Finite Element Method. The balance of floating ring is achieved by adjusting ring-to-shaft speed ratio, inner film radial clearance and inner film eccentricity ratio. It can be seen from simulation results that the ring-to-shaft speed ratio and inner film clearance vary slightly and the floating ring can keep balance under different speed and eccentricity ratio. The variation of static and dynamic performance with eccentricity and rotational speed are calculated and analyzed based on floating ring balance.

Abstract: The flow passage including supply hole of externally pressurized gas was investigated. The outlet velocity of supply hole, bearing number and supply pressure’s relationship were built. According to supply hole’s speed, supersonic or subsonic model was chosen to calculate bearing clearance’s pressure distribution. Bearing number’s effects on pressure’s distribution was also studied. The calculation result shows that at larger bearing number, supply hole’s speed is harder to be chocked. Both in supersonic and subsonic condition, larger bearing number produces lower pressure loss.