To restrain the formation of stall, the internal flow structure of a high-specific-speed axial flow pump is predicted by transient numerical simulation. The calculated results are validated by test data. The mathematical statistical theory of standard deviation is introduced to analyze and compare the pressure fluctuation intensity (Pflu) under the design and stall operation points. The results indicate that influenced by the large-scale vortices structure within stall region, Pflu inside different flow passage components increases. In terms of the spatial distribution, the Pflu near the inflow pipe wall of the outlet increases from the enhancement of the impeller pre-rotation effect. In the impeller channel, the flow separation vortices near the leading edge of the blade and the reflux vortices at the outlet hinder the mainstream flow and cause P_flu to increase. In the guide vane channel, there are high-intensity vortices near the suction side and leading edge, resulting in an increase in P_flu.

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When GVF in the inlet of the oil-gas mixed transmission twin-screw pump is high, the temperature difference between the inlet and outlet of the screw pump will rise significantly, and rotor expansion jam will occur. To prevent the expansion jam caused by the overheating of the screw pump, the cooling water jacket is designed for gas-liquid mixed screw pump with high GVF to continuously cool. Using the theory of fluid-structure interaction heat transfer, the cooling effect of the cooling water jacket of the equal pitch screw pump and the variable pitch screw pump is numerically calculated, and after comparison with the experiment, it finds that the maximum deviation of the outlet temperature of the variable pitch screw pump does not exceed 4K and the average deviation is about 6 %. When GVF is 96%, the calculation of the cooling water cavity shows that the average temperature drop of the liner after the cooling of the equal pitch screw pump and the variable pitch screw pump is about 4K and 3K, respectively. When GVF rises from 90% to 99%, the average temperature drop is about 3.5K. Cooling water jacket has obvious cooling effect on screw pump with high GVF.

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In order to increase turbine efficiency while retaining structural integrity, modern jet engines need an effective cooling system. Pin-fin arrays play a significant role in the internal cooling system of the turbine blade. In examining the efficacy of cooling techniques using pin-fins, the other papers focus on pin-fin configurations. In contrast, the current study is a step toward optimizing cooling cascade endwalls for better maneuvering and reservation of vortices, which leads to more considerable heat transfer near the endwalls. This study examines the flow field and heat transfer of roughed endwall in the pin-fin channel, including varieties with flat endwall and extruded endwall. The heat transfer of the channel and pressure drop properties of the extruded endwall case are quantitatively assessed to contrast with those of the flat endwalls scenario for an intake Reynolds number range of 7400 to 36000. The leading and trailing surfaces of the channel are divided into five streamwise regions to understand better how well the pin-fins and endwalls transmit heat. The results show that the new endwall construction significantly increases the high heat transfer zones around the pin-fins compared to the flat endwall scenario. In the meantime, the heat transfer of the channel to the pin-fins is enhanced by the modified endwall configuration. The redesigned endwall outperformed the basic case regarding the HTEI, rising by 15.9%. It is found that the friction factor of the new design is increased due to the narrowing channel. However, due to their much higher heat transfer capacity, the HTEI of extruded endwall is up to 41.5% higher than the HTEI of the channel with flat endwalls. These results demonstrate that the heat transfer properties of pin-fins can be significantly improved by optimizing endwall design.

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The wire arc additive manufacturing (WAAM) is one of the metal additive manufacturing technologies. WAAM can be additive manufactured to existing parts, and when combined with machining, has a high affinity for the fabrication of blades, which are important parts of turbomachinery. However, almost all related research has been limited to the fabrication of parts such as turbine blade or propeller while investigations have not been conducted by incorporating the fabricated parts into turbomachinery. In this study, a fan type inducer made of stainless steel was developed using WAAM and machining. The developed inducer was installed to a centrifugal pump, and pump performance tests were conducted to investigate the advantage of this fabrication process to turbomachinery.

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This paper presents a numerical simulation of a leaking pipeline and verifies the method's applicability using existing experimental data. The method involves generating reflected waves at the leak point by using pressure waves generated by fast valve closure, which causes aberrations in the pressure signal at the valve. The different times of aberration at different leak locations can be used to determine the location of the leak. Furthermore, the time domain information of the pressure signal is refined using the wavelet transform method to capture sudden changes in the pressure signal, which improves the accuracy of the leakage position. This method was tested for different leak locations, sizes, and pipeline wave speed conditions, resulting in accurate detection with an error of less than 1%. When there are multiple leak locations in the pipeline system, the method has a high degree of recognition of the existence of multiple leak locations and can accurately detect the location of each leak. Additionally, the effect of different valve closing times on the pressure waveform of pipeline leaks was studied, demonstrating that slow valve closure can detect the occurrence of a leak in the pipeline, while fast valve closure can be used to locate the leak.

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The swirling flow under the part-load (PL) operation of hydraulic turbines causes the formation of a rotating vortex rope (RVR) inside the draft tube. The RVR precession induces pressure fluctuations and periodic loadings that can jeopardize the hydraulic machine's structure and performance. The behavior of these fluctuations is closely related to the characteristics of the RVR, which can vary for different PL conditions. A series of experiments have been performed to characterize the periodic behavior and stability of the RVR under various PL operating conditions. For this purpose, wall pressure measurements were conducted at two sections along the draft tube axis of a scaled-down model of the U9 Kaplan turbine. Spectral analyses were performed, and the periodic stability of the RVR was investigated based on the statistical analyses of the amplitude and frequency of the pressure oscillations. The results showed that the amplitude of the pressure oscillations increases with the decrease of the discharge while the stability of the RVR decreases. Upstream, the behavior and stability of the RVR asynchronous mode pressure oscillations are highly dependent on the flow conditions at the draft tube entrance. However, due to the downstream RVR dissipation, the effects imposed by the elbow become the dominant factor in the RVR behavior close to the elbow. The statistical method proposed in this study provided an in-depth view of the RVR instantaneous behavior, allowing a more accurate characterization of the phenomenon than only studying its spectral content.

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The contra-rotating small hydroturbine can be applied to pipelines of agricultural water and for farming river fishes. In the previous research, the advantages of the contra-rotating small hydroturbine were verified by the numerical analysis and experimental apparatus of our lab. The diameter of our test model was small as 58mm and it have to be scaled up to apply it to the actual case of a pipeline for farming river fishes. Therefore, we made the diameter of our test model larger, which is suitable for the pipeline for farming river fishes. The numerical analysis was conducted to check the power of the large-scale model for the pipeline. Furthermore, the parameter study related to the solidity, blade number and setting angle, was conducted to increase the power of the hydroturbine using the numerical analysis. After that, the suitable impeller for the field test was chosen and an experimental apparatus for the field test was established. The power generation at different flow rate conditions was measured by the experiment and the stability of the experimental apparatus; leakage flow from the mechanical seal, vibration, noise of the turbine, was checked in the field test. In this paper, our developing process of the contra-rotating small hydroturbine is shown and the prospect to apply our test turbine for the pipelines is discussed based on the numerical analysis and field test results.

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The recent trend is harvesting more efficient radial piston pumps for industrial applications. The valve plate geometry of the pump plays a crucial role in yielding the pump pressure and flow as a whole generated output power of the pump. The generated output power of the pump is dependent on pump pressure and flow rate, the required input power of the pump is liable to rotational torque and speed. This simulation study designed the valve plate geometry with and without silencing groove and analysed the pump performance, forces, required input mechanical power and generated output fluid power. The silencing groove valve plate plays a vital role in pump performance. The silencing groove is a gradual notch shape volume, contact surface area, and volume slowly increasing toward the manifold. The present study finds out the pump's efficiencies based on output fluid power and inputs mechanical energy for with and without silencing groove model. The simulation results manifest the silencing groove valve plate model is more efficient than the without silencing groove valve plate model of the pump.

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