Search

In order to obtain the effect of endwall secondary flow on the swirling film cooling, a geometric model of cascade is established to research the endwall swirling film cooling and swirling flow induced by prismatic jet impingement configurations. Numerical simulation is applied to investigate three jet flow configurations on the endwall film cooling performance at the compound angles of film hole γ = 0° and 30° and blowing ratios M = 0.5–2.0. The influence of complex vortex structures near endwall for jet flow is analyzed in detail; the strong transverse cross flow near the endwall is the main reason affecting the film cooling effectiveness. The variation laws of endwall film cooling effectiveness with the compound angle of film hole, jet flow configuration, and the blowing ratio are obtained. As the blowing ratio increases, the spanwise average film cooling effectiveness increases first and then decreases. While the blowing ratio is M =1.0, the endwall film cooling effectiveness is the best. Increasing the compound angle of the film hole leads to a decrease in the endwall cooling effectiveness. The spanwise average cooling effectiveness of γ = 30° decreases by 35% compared to the γ = 0°. [ABSTRACT FROM AUTHOR]

In this study, the thickness of water film, which is frequently formed on compressor blade surface, was investigated. Simultaneously, its movement and extra torque demand were provided by a simulation model of the code. Having taken into account the transformation in blade's profile and the thickness feature of the films, the working medium characteristic transformation in compressor stage was analyzed. In addition, formation, development and movement of the water film on a compressor stage were simulated by using unsteady numerical methods in various water injected conditions. Movement characteristics of water droplets in cascade were investigated to understand the flow mechanisms responsible for water film formation process. The forming and the tearing process of water films, which formed on the blade surface, were analyzed at different injection conditions. In consideration of the "Scoop effect" in actual situation, the maximum quantity of injected water can reach 12 %. Results indicated that continuity and region of the film would be developed with the increment of droplet size and injection rate. It was also found that water film's tearing process brought about flow losses near blade surface due to the increment of surface roughness. [ABSTRACT FROM AUTHOR]

Summary: Modular high‐temperature gas‐cooled reactor power station (MHTGR) is the most promising configurations for fourth‐generation nuclear technology. Aiming at the low accuracy of the performance prediction of MHTGR compressor, the paper intends to provide an experimental basis to have deep comprehension about the nexus of loss, passage structure and working conditions, including surface flow visualization, five‐hole probe measurement at the outlet section and surface pressure measurements under different conditions (blade camber angle, incidence angle). The experimentally measured data and images give a deep insight into the influence of blade camber and incidence on the flow structure, loss and blade loading. The vortex system is mainly shaped by the action of the pressure field. When the flow turning angle is large, the effect of the working fluid properties may be inconspicuous on the overall loss of the flow, rather than the tremendous impact on the boundary layer friction loss of attached flow as in the small blade chamber angle passage. For different vortices, the effect of each factor, which may cause losses, is also wax and wane. [ABSTRACT FROM AUTHOR]

The part-load performance of gas turbine is of great importance due to the consideration of running time spent at part power, and Variable Geometry Turbine (VGT) is an important way to meet the requirements. Effect of variable geometry guide-vane with cylindrical endwalls on part-load turbine stage performance is quantified by detailed analysis of aerodynamic characteristics. The turbine stage characteristics of corrected mass flow, corrected output power and efficiency are presented to investigate the VGT performance under the condition of four off-design rotating angles. In addition, the flow field, the loss distribution and the leakage flow are analyzed for different rotating angles. Results show that both the corrected mass flow and the corrected output power increase as the vane throat area is increased, the total leakage area and the shroud area are increased with the increase of rotating angle, whereas the hub leakage area is decreased, and the total pressure loss and the entropy change of variable geometry vane are both increased with the decrease of vane throat area. [ABSTRACT FROM AUTHOR]

The variable geometry turbine (VGT) has been widely used in different fields due to its higher efficiency and lower fuel consumption at part-load. However, the flow field in a VGT is characterized by the leakage flow through the radial clearance of rotational vane compared with a general fixed vane turbine. Numerical simulations are conducted on a linear turbine cascade to reduce the leakage flow based on passive control method. The aerodynamic performances and flow fields are compared for four kinds of tip configuration firstly. Then, the effect of variable geometry on the linear turbine cascade aerodynamic performance is investigated for five installation angles ranging from –5 to 5 deg. In addition, the development patterns and trends of the tip leakage vortex and the passage vortex are analyzed. The results show that the squealer tip and the rotating axis have a significant impact on suppressing leakage flow. The leakage flow rate has a tendency to decrease, and the total pressure coefficient is gradually increased when installation angle ranges from –5 to 5 deg. The interactions between tip leakage vortex and passage vortex leads to the different trends on leakage flow at various installation angles and axial sections. [ABSTRACT FROM AUTHOR]

The crack growth rate (CGR) tests of austenitic steel TP347HFG were conducted under <10‐8000 ppb dissolved oxygen (DO) in steam, the alternating environment of air and steam and supercritical water (SCW) at 600–650 °C. A constant stress intensity factor (K) method and direct current potential drop technique were used in the tests to evaluate its environmentally assisted cracking (EAC) properties as superheater and reheater boiler tubes in ultra‐supercritical power plants. CGR increases monotonically with temperature and DO content. CGR in SCW is greater than that in the high‐temperature steam which indicates that exposure pressure has an obvious effect on crack propagation. The varying CGR in different experimental environments show that exposure medium participates in the cracking process. Fracture surface and cross‐sectional surface of compact tension specimen were analyzed by scanning electron microscope. The mechanism of crack propagation in different exposure environment is further discussed. [ABSTRACT FROM AUTHOR]