Advanced Materials Research Vols. 694-697

Abstract: According to requirements of fire service, turbopump is used to supply water from low-level water resources. The efficiency of agricultural irrigation turbopump is too low to provide sufficient water to fire control, so a fire turbopump is designed in this paper. It is common to design a turbopump by empirical methods, but this causes turbopump not to operate at best efficiency point. Therefore, three design concepts of new turbopump model, existing hydraulic match model and turbopump conversion model are discussed. Their theories and application conditions are also listed. After design of fire turbopump by new turbopump model, numerical simulation is conducted to analyze the pressure field to predict operating status. The open rig experiment is also presented to confirm its performance characteristics. The pump head and flow rate of the designed turbopump meets the requirements of fire ground and it is proved that the efficiency of fire turbopump is much higher than irrigation turbopump, which indicates the new turbopump model is an effective strategy to design turbopump.

Abstract: Many offshore and harbor structures are composed of cylindrical members. In this paper, the special case of shoaling breaking wave loads on a vertical cylinder is investigated in a tank. A segmented cylinder model with outer diameter of 0.204m and total height of 1m was built and tested. Also a 1:20 slope ramp was constructed in the tank to provide the shoaling effect. During the experiments the total force on each segment of the cylinder was measured and the water surface elevations at the cylinder and in deep water were also recorded. Studies on wave shapes and wave loads are presented here.

Abstract: The paper presents the methodologies and approaches used in a Cavitation Tunnel or any other circulation channel to investigate the power extraction performance of a marine stream turbine. The paper first introduced model test similarity laws used in the Emerson Cavitation Tunnel (ECT) of Newcastle University to test a marine turbine in marine propeller cavitation tunnel; then based on these similarity laws to investigate the power extraction performance of a marine turbine in different approaches to control the rotation speed, namely: Torque Control and Rotation-speed control. A comparison was made by the tested experimental results. Torque Control is referred to the speed control strategy of using a generator to absorb the torque building up from the stream, on the other hand Rotation-speed control is to use motor to control rotation speed of the turbine. It indicates that both methods can be employed to investigate the hydro performance of marine stream turbine, with wider range of TSR can Rotation-speed Control test.

Abstract: In this paper, the open water performance of a pod propeller in the viscous flow fields is numerically simulated by the Computational Fluid Dynamics (CFD) method. Based on the coordinate transformation formula for transforming the local to the global coordinate, mathematical model of a propeller is created. Thrust and torque coefficients corresponding to different advance coefficients of the model are calculated by ANSYS-CFX with three different turbulence models. The pressure distributions on the blade surface are also presented. Comparisons show that experimental results and numerical results agree well, with SST k-ω and RNG k-ε more accurate than the standard k-ε.

Abstract: Load-sensing hydraulic steering system is universally used in wheeled machinery for good steering regulation performance and obviously saving energy effect. The load-sensing hydraulic steering system is present, and it is considered to be a mechanical and hydraulic position control system. The flow continuity equation and force balance equation of steering system is established, the transfer function of load-sensing hydraulic steering system is obtained, the system steady-state error caused by the typical input signal and load input signal on the basis of transfer function. The main parameters affecting the steady-state error are got, and it provides theoretical support for designing and improvement of load-sensing hydraulic steering system.

Abstract: Efficiency of the tidal stream turbine with thin-wall axisymmetric ducts was numerically simulated. The ducts design parameters of diffuser curves, expansion ratio and duct length were simply optimized. The results showed that the duct of second order diffuser curve, expansion ratio of 2.25 and a length-diameter ratio of 1.2 has the best performance. By comparison of different ducts flow, it revealed that flow separation at the duct outlet and the ejection influenced ducted turbine efficiency. The separation caused blockage and flow rate decreasing, and so performance deteriorated. The ejection caused lower pressure at the outlet of the duct, which allowed higher pressure drop through turbine impeller, and so improved turbine efficiency.

Abstract: The engine cooling water jacket has a major impact on the efficiency of the engine. In this paper the flow in the cooling water jacket of the six-cylinder four stroke water-cooled diesel engine was studied with the commercial software of STAR CCM+. Results of the simulation reveals that velocity has little effect on the flow field distributions. Dead zone in engine cylinder head appeared far away from the inlet of the flow. But it could be avoided or improved effectively by arranging the inlet and outlet at opposite side of the cooling water jacket. Further study suggests that a good flow field distribution can be achieved near the entrance if one inlet was put at the same side of the outlet and the other the opposite side, while the wall was impacted fierce due to the strong turbulence and eddy existed. Finally some advices were given to solve the problem.

Abstract: Based on the thermal network method and heat transfer theory, a temperature field simulation model of complicated thermal analysis system was established by Matlab Simulink. Based on the model, a steady-state temperature field of a helicopter tail reducer was calculated in the normal lubrication. The model is more accurate and reliable than the traditional algorithm. Meanwhile, the model can calculate the time-varying process of the temperature field, corresponding to the transient temperature field.

Abstract: In this paper, a semi-linear heat equation with nonlocal boundary condition and variable exponents is studied. The results to existence of global solutions or blow-up of solutions are obtained.

Abstract: Air side heat transfer coefficient is a key problem to study thermal regime of air-cooled units. Five commonly used equations for calculating the heat transfer coefficient of wavy finand tube heat exchanger of air source heat pump and scope of application were analyzed. According to the typical example, all the solutions of equation are calculated for the five methods. Comparing between theoretical data and experimental data, the experimental results are basically consistent with the theoretical solution J factor method and McQuiston method is recommended as the optimal method for calculating the heat transfer coefficient of wavy fin and tube heat exchanger. It is provided theoretical basis on optimal design and thermal characteristics.