The velocity distribution method is a way to design the blade profile according to the average relative velocity in the impeller passage. Present research is aimed to investigate the effect of blade profile on the performance of a centrifugal fan with different velocity distribution functions through numerical simulations. The results show that compared with common arc blade, the centrifugal fan with new blade profile designed by velocity distribution method gets a higher efficiency, the relative velocity distribution along impeller passages of the new model is more uniform, and the boundary layer separation is delayed than that in the original model.

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This paper presents the numerical analysis on the aerodynamic flows and noise of serrated blades axial fan. Unsteady flow and noise analysis were simulated with an embedded SST k-ω turbulence model and Ffowcs-Williams Hawking's equation. Nine modified axial fan blades models are evaluated and compared with the original model. It was confirmed that the original models concord with the experimental results of the performance curve. The effectiveness of serration is investigated with different values and ratios of amplitude (h) as well as spanwise wavelength (λ). The results indicated that a large reverse flow vortex obtained in the original model compared to serrated models. Remarkably, the serration edges showed an efficient noise reduction achieved by models λ/h=0.25 and λ/h=1, which reduced the noise by 14 dB and 4.2 dB, respectively. Besides a noise reduction up to 11.4 dB was achieved using different values of λ and h at the same serration ratio.

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Geothermal-source heat pump technology can increase the production efficiency and reduce the energy consumption. However, the application performance of the control system for the geothermal-source heat pump is always poor; such as a larger system operation energy consumption, low efficiency, poor stability and time effectiveness. In order to solve this issue, two advanced control strategies based on the research object of the geothermal-source heat pump temperature control system with different modes are developed: one is a feedforward-feedback control based on the variable speed integral PID control algorithm ("FFC-VSIPC"), the other is a feedforward-feedback control based on the fuzzy control algorithm ("FFC-FC"). The simulation and experimental studies of the effects of temperature control system in a geothermal-source heat pump by different models are carried out. The results shows that: (1) The overshoot of FFC-VSIPC is slightly larger than the FFC-FC when the set value is abruptly changed, but the adjustment time of FFC-VSIPC is shorter and there is no static error after the stabilization; (2) Changing the rate of flow interference suddenly, both FFC-VSIPC and FFC-FC can effectively eliminate the effects of interference with adding a feedforward control, also the adjustment time of FFC-VSIPC is greatly shortened than FFC-FC, but the stability of the adjustment is worse; (3) When the frequency amplification factor is suddenly changed, FFC-FC shows a non-stable control state of divergence gradually, FFC-VSIPC shows good robustness. The further comparisons between simulations and experiments reveal that FFC-VSIPC is better than FFC-FC in terms of the energy regulation and controlling of the geothermal-source heat pump. Therefore, FFC-VSIPC is an advanced control strategy, which is worthy of research and application promotion.

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In most servo valve control systems, the flow force is a critical factor influencing the control precision of the servo valve, especially in the pilot stage. In this paper, the generating mechanism of the flow force in the pilot stage is analyzed, showing that it is mainly generated by the impacting jet. Then, a three-dimensional numerical model of the deflector servo valve is built, and the pressure distribution on the deflector is simulated under different offsets. Due to the complicated structure of the deflector jet valve, it is impossible to measure the flow force directly. Thus, an indirect method is proposed for the flow force measurement. Compared with the theoretical analysis and the simulation results, it is found that the indirect method can be an effective way to get a reliable relationship between the flow force and the deflector offsets. The experiment shows the flow force increases linearly with the deflector offsets and the growth rate is 7.32×10-4 N/μm. Meanwhile, the maximum flow force can reach 0.0366N in working condition.

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This paper aims at identifying the characteristics of the Savonius Wind Turbine using a guide vane, which functions as the steering mechanism and reduces the negative torsion on the returning blade. The addition of the guide vane did not influence the turbine’s capacity in receiving wind direction. The number of guide vanes varied from 4, 8, and 16 with an angle of 45°. The testing was conducted in a wind tunnel at the wind speeds of 4 m/s, 5 m/s and 6 m/s. The turbine with the additional 16 guide vanes gave the best result. The static torsion increased by 84%, dynamic torsion increased by 57%, and the coefficient of power increased by 58% at the speed of 4 m/s.

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The purpose of this study was to analyze the effect of waste valve and the delivery valve diameter on the 3-inch hydraulic ram efficiency. The waste valve is one important component of the hydraulic ram. The results showed that the diameter of the waste and delivery valves greatly affect the efficiency of hydraulic ram. The highest D'Aubuisson efficiency was 67.66% with the waste valve diameter of contained 2.75 inches and the in the waste valve variation of 2.75 inches diameter and delivery valve diameter of 2.2 inches. The lowest efficiency was 36.14% with the waste valve diameter of 2.25 inches and the delivery valve diameter of 0.6 inches.

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Recently, injection-type shaft seals (non-contact type seals) started replacing their counterparts called mechanical seals (contact-face type seals) in power plant feedwater pumps. Both of these seals have primary function of preventing the fluid inside the pump pressure casing from leaking to outside of the pump. Mechanical seals are reported to fail rapidly and abruptly in especially power plant feedwater pumps because of increased speeds and the feedwater temperatures. If mechanical seals fail, most often the pump must be shut-down immediately and put the pump reliability in question. Hence, the injection-type shaft seals were introduced in order to avoid reliability problems associated with mechanical seals and save maintenance costs of feedwater pumps. Therefore, in this paper we investigated the performance of injection-type shaft seals particularly with labyrinth and plain annuls designs. Research findings show that design parameters such as seal clearance and diameter play an important role in determining the injection-type shaft seal's leakage, while drain temperature was un-affected by these design parameters.

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The gas-liquid mass transfer has been studied for a single long bubble, which is kept stationary in the flow by a low and stable flow rate of liquid around it. This study was carried out for a downward flow in small diameter pipe. The mass transfer mechanism is quite complicated because it doesn't depend only on the physical properties of the gas; but also on the hydrodynamics of the bubble and the liquid film around it. Based on Hgbie's penetration theory a detailed numerical simulation of the hydrodynamic characteristics of the gas-liquid mass transfer in a vertical pipe is developed using the volume of fluid (VOF) method implemented in the commercial software ANSYS Fluent. The simulation is performed using three types of gas, which are nitrogen, oxygen, and carbon dioxide as the gas phase, and water as the liquid one. The results show that the mass transfer of gas increases as the length of the bubble does. For the three types of gas, the mass transfer coefficient increases with the decrease of the gas density. The numerical results are analogous with the experimental ones available in the literature.

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