Gas turbines play a crucial role in the aviation industry as they are primary sources of power for most aircraft. The combustion chamber is one of the three essential part of jet engines, together with compressor and turbine. Energy is generated when fuel is burned in the combustor. In the primary zone, the recirculation flow is of great importance to aerodynamic performance. Swirlers, fitted in the dome around the fuel injector, can alter the behavior of the recirculation flow and thus, impact combustion performance. The vortex behind a swirler can be easily controlled by changing the swirl angle. In addition, changing the vortex angle leads to a difference in mixing between fuel and air. This paper investigates the effects of swirler design, based on the swirl angle, on aerodynamic performance of an annular combustion chamber in cooling condition using three-dimensional Reynolds-averaged Navier-Stokes equations with the SST turbulence model.

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For general-use turbopumps with inducer, instability-free operation is required as well as high suction performance in a wide operating range from shut-off to over flow rates. Among the instabilities, the cavitation surge at low flow rates is a very vital phenomenon that is known to be strongly associated with the occurrence of inlet back flow. The low inlet blade angle would be favorable for the suppression of inlet backflow through the reduction of blade loading at the inlet, while the inlet throat area should be kept large for better suction performance to minimize the flow blockage due to cavitation. In the present study, a splitter blade inducer is designed on the basis of the knowledge acquired by our previous CFD study conducted for the 2-D cascade and 3-D straight-hub inducer. Then the effectiveness of the splitter inducer is investigated by experiments and CFD. As a result, the inlet backflow and the cavitation surge are found to be suppressed in the splitter inducer, which is achieved by reducing the blade loading with low inlet blade angle. The suction performance is improved at high flow rates by relaxing the low pressure region with high relative velocity.

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The most widely of hydraulic applications power employed source that including low manufacturing costs and good performance are defined as the external gear pumps. In this study, the using of unstandard gears and influence on the performance of gear pumps are studied. These influences include pulsation factor of flow rate, flow rate of pump and trapped volume between two meshing gears. Matlab software has been used to evaluate performance by modifying algorithm and deriving the equations of pump flow rate. The unstandard gear is used in the study undertaken with +0.3 Rack shift coefficient. Results indicated the using of unstandard gears increase flow rate and reduce the trapped volume and pulsation flow rate factor. It was concluded that the factor of pulsation flow rate reduces as increase of teeth number which leads to pulsation flow rate stabilization.

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In order to examine the fundamental characteristics of a corner separation in a decelerating cascade flow, an experimental apparatus was made and the three-dimensional separation around a NACA65 blade in a decelerating channel flow was investigated experimentally. Effect of stagger angle of 14 deg. and 10 deg. on the channel flow was focused on. The experimental investigation by the five-hole probe showed that the accumulations of the low energy fluid was seen around the corner part and the overturning flow due to the secondary flow existed for 14 deg. of stagger angle, whereas the accumulations of the low energy fluid were seen at around midspan for 10 deg. of stagger angle. PIV measurement showed that various focus-type separations were seen in the flow for 10 deg. of stagger angle and three-dimensional vortex structure was considered by using a vortex filament.

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The roller vane pumps are widely used in the automobile industry as steering pumps. However, the cavitation damage near the outlet relief groove could directly decrease serve life and efficiency of the roller vane pump. In this paper, the mechanism of the cavitation is discussed, especially the cavitation damage near the tip of the relief groove. The computational fluid dynamics simulation method (CFD) based on dynamic meshing technique and user defined function (UDF) is applied to calculate flow dynamics and multi-phase flow characteristics, especially the flows inside the fluid film between the stator and valve plate. The simulated results show that the cavitation region is the same with the experiment one, and the cavitation inside the fluid film is caused by the shear action of the stator and valve plate. The negative pressure region near the relief groove has an extreme low pressure at 0.08 MPa, and the maximum flow velocity is 99.3 m/s. Besides, the cavitation region near the relief groove has the highest gas volume fraction of 2.23% and the lowest density of 560 kg/m3. Furthermore, the reason why cavitation happened at this position in a roller vane pump is analyzed by theoretical analysis.

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To improve the quality of the gasket and reduce leakage, non-asbestos gasket composites reinforced by graphene oxide(GO) were prepared. The effect of GO on the microscopic physics and chemistry of slurry suspension and the macroscopic properties of gasket composites were investigated. The microstructure and morphology were analyzed by Fourier-transform infrared (FTIR) spectroscopy and Field emission scanning electron microscopy (FSEM). The results show that the addition of GO improves the microscopic interaction during the wet forming process, which improves the macro properties of the gasket material. The enhancement can be ascribe to the crumpled morphology of GO and the presence of many oxygen-containing functional groups, which enhance the microscopic mechanical interlocking and interfacial interactions of the composite gasket material.

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The fundamental behaviors of deep surge frequencies in axial-flow compressors have come to be described as a rather simple framework for low pressure-ratio compressors, in terms of two essential reduced frequencies concerning resonance frequencies and surge frequencies, on the basis of numerical-experimental results. For high-pressure-ratio multi-stage compressors, however, the frequency behaviors over a wide range of compressor speeds tend to give drastic deviations from the simple framework, including abrupt changes and apparent irregularities. The cause was investigated here by numerical simulations on a nine-stage axial flow compressor. Generally, deep surge frequencies of high-pressure ratio compressors tend to lower gradually, from low speeds toward higher ones. At somewhat below the design speed, the frequencies tend to decrease precipitously, settling to some very low levels of values. The discontinuous drops in the frequencies are shown to result from occurrences of short-term incomplete surge recoveries in the stalling phase of surge. The phenomenon tends to elongate the duration of the stalled phase and the whole surge duration, resulting in the lowered surge frequency. The phenomenon is caused by the flow reversal of high-temperature air in the stalling phase of surge and the re-suction of the hot air in the unstalling phase. The degree of the peak temperature and the intensity of the interferences between the hot-air re-suction phenomenon and the intrinsic surge appear to affect significantly the additional short-term premature stalling of the compressor. It could be strongly related with the high average temperature due to the hot air re-suction, and the duration time of the suction. The complicated behaviors thus become qualitatively explainable, though only by examinations on numerical-simulation results.

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The axial force balancing capacity of a balance drum is a key factor affecting the life of multi-stage centrifugal pumps. In this paper, a double shell segmental multistage pump is taken as the research object. The hydraulic performance and axial force performance are set as the optimization objectives, and the performance data are obtained by numerical simulation with FLUENT software. The BP neural network is used to establish the prediction model of structural parameters of the balance system, hydraulic performance and residual axial force performance, and it is used as the adaptive value evaluation model of genetic algorithm to solve the optimal value in the sample space. The results show that the radial clearance of the balance drum and the balance tube orifice flowmeter, the axial width of the balance cavity are the significant factors affecting the hydraulic performance and axial force performance of the multistage pump. When the radial clearance of the balance drum is 0.1mm, the clearance of the orifice flowmeter is 1.95mm, and the axial width of the balance cavity is 55mm, the multi-stage pump has the best hydraulic performance and the smallest residual axial force. The vortex band in the balance cavity can increase the amount of the fluid spin and enhance the axial force balancing capacity of the balance drum. The greater the area occupied by the negative high-rotation fluid in the balance cavity, the stronger the ability of the balance drum to balance the axial force. The test results show that compared with the prototype multistage pump, at nominal flow rate, the head and efficiency of the optimized model are increased by 0.71% and 1.63% respectively, and the bearing temperature and vibration speed of the multi-stage pump are significantly reduced.

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In the present study, a reduced model of the Francis-99 model turbine was investigated numerically at part load operating condition. The reduced model consists of a standalone draft tube domain of the Francis-99 model turbine. Numerical studies performed in the past on nearly complete hydro-turbine models (inclusive of the spiral casing, distributor domains, runner, and draft tube) reportedly consist of a large number of computational grids. This may increase the computational costs and data storage required to perform numerical analysis, which could be a setback for future research on new design concepts and optimization study of the draft tube domain. The reduced model was developed by mapping the phase averaged axial, radial, and tangential velocity profiles from the runner exit to the inlet of the standalone draft tube domain. Additionally, turbulent kinetic energy (k) and turbulent eddy dissipation (ε) variables were also considered for better flow prediction inside the draft tube domain. Two methods for mapping inlet boundary conditions were considered in the present study. In the first method, the entire planar profile of the runner-draft tube interface was considered. In the second method, the variables along a radial profile at the runner exit were considered with an axis-symmetric flow assumption over the entire draft tube inlet plane. The numerical results obtained from the Francis-99 reduced model turbine were validated against the numerical model of the NVKS Francis-99 model turbine (with available structured mesh) that was also analysed using the passage flow numerical technique and available experimental results. The results were found to be in reasonable agreement, with each other. The present study could be useful for the future mitigation study of rotating vortex rope by modifying the draft tube domain.

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This paper sets up both a force balance equation and a three-dimensional geometric model of a flexible side plate in an intra-vane type pump, after analyzing the structure and mechanical properties of the plate. The formulas for calculating deformation were obtained, and the theoretical curve of change in deformation was determined. Then, the contour of deformation was obtained using software simulation. The calculated and simulated values of deformation of the flexible side plate, in three positions under four working pressures, were found to be close to one another, the relative error between them being less than 2%. Next, the formula for the calculation of oil film thickness was obtained, and the curve of the change in oil film thickness relative to the distance along the radial direction of the side plate was determined, considering the flexible side plate deformation. The oil film thickness for three flexible side plate positions were then tested through experiment. The calculated values of oil film thickness were also close to the tested values. Although there was a small difference, the relative error between them was less than 5% for the oil film thickness measured at its lowest point, which indicates the accuracy of the results obtained by the theoretical calculation.

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There are many kinds of the fluid food transportation pumps depending on the characteristics of the fluid, i.e. a sanitary pump made from stainless steel, a screw pump and so on. A centrifugal pump was adopted as a fluid food pump in this research because it makes the stable continuous transportation of fluid food and the structure of the pump is simple compared to positive displacement pumps. The purpose of this research is to investigate the influence of the blade number on the pump performance and internal flow to enrich the pump design data for low viscous fluid food. The centrifugal pump with an open impeller was used and six impellers having the different blade number were prepared. Performance test using an experimental apparatus was conducted and the numerical analysis was also carried out. In the numerical analysis, the commercial software ANSYS-CFX16.2 was used. The head, shaft power and efficiency obtained by the numerical analysis, are almost the same with the experimental results. The head and shaft power increase with the increase of the blade number. The shear rate, which is concerned to fluid food quality, is high near the inlet region of the blade-to-blade passage for all types of blades. The shear rate of each type of the blade is discussed based on the numerical analysis results and relations between the blade number and shear rate are clarified.

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