At present, wind power is widely used, especially in near-residential areas, and blade noise has become an important factor affecting the installation and operation of the unit. Vortex Generator is a new technology that has been used by wind turbine blade manufacturers in recent years. At present, there are few studies on the changes of blade aerodynamic noise after the installation of vortex generators in China. In order to study the influence of vortex generators on aerodynamic noise, the flow field is simulated by numerical calculation method before and after the blade is installed with vortex generators. The visualization results are output and compared, and the parameters such as vorticity and pressure are analyzed. Secondly, based on the detailed parameters of the flow field, FW-H equation is used to calculate the sound source propagation, and the sound pressure level spectrum of the blade before and after the vortex generators added is obtained. The research shows that the vorticity increases in the vicinity of vortex generators and the downstream region, which promotes the mass and energy exchange between the upper fluid and fluid in the boundary layer, so the boundary layer separation is delayed, and the wake vortex subsides. The aerodynamic noise is low frequency noise, and the addition of vortex generators can significantly reduce the aerodynamic noise of the blade.
Stimulated reservoir volume is an effective stimulation measure and creates a complex fracture network, but the description and characterization of fracture network are very difficult. Well test analysis is a common method to describe the fracture network, and it is the key to build a proper interpretation model. However, most published works only consider the shape of the fractured area or the stress sensitivity effect, and few works take both factors into account. In this paper, based on reservoir properties and flow law after a stimulated reservoir volume, an interpretation model is established with an arbitrary shape of the fractured area and stress sensitivity effect of different flow areas. The model is solved to conduct the pressure response using Laplace transform, point source function, and boundary element theory. The influence of fractures’ parameters and stress sensitivity effect is analyzed on the pressure behavior. Results from this study show that the special flow regimes for a horizontal well with a stimulated reservoir volume are (1) bilinear flow dominated by hydraulic fractures, (2) linear flow dominated by formation around the hydraulic fractures, (3) crossflow from a matrix system to the fractured area, and (4) radial flow control by properties of the fractured area. Parameters of hydraulic fractures mainly affect the early stage of pressure behavior. On the contrary, the stress-sensitive effect mainly affects the middle and late stages; the stronger the stress sensitivity effect is, the more obvious the effect is. The findings of this study can help for better understanding of the fracture network in a tight oil reservoir with a stimulated reservoir volume.
CFD was employed to simulate the steam flow in 1.5-stage cascades with three different seal clearances. When the seal clearance is 0, there is no steam seal leakage, no obvious secondary flow in the cascade, and the stage efficiency reaches 88.27%. When the clearance of diaphragm seal and rotor tip seal is 1mm, the leakage of diaphragm seal strongly interferes with the flow in the cascade, which promotes the formation and development of the end-wall secondary flow near rotor hub, and the rotor tip leakage flow has little effect on next stage, and the stage efficiency drops by about 2 percentage points. When the seal clearance is 4mm, the end-wall secondary flow near rotor hub and next stator casing is strengthened significantly, and the attack angle loss increases, so the stage efficiency decreases by about 13 percentage points.
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