Numerical simulation on directional solidification and heat treatment processes of turbine blades

Study on turbine blades is crucial due to their critical role in ensuring the efficient and reliable operation of aircraft engines.Nickel-based single crystal superalloys are extensively used in the hot manufacturing of turbine blades due to their exceptional high-temperature mechanical properties.The hot manufacturing of single crystal blades involves directional solidification and heat treatment.Experimental manufacturing of these blades is time-consuming,capital-intensive,and often insufficient to meet industrial demands.Numerical simulation techniques have gained widespread acceptance in blade manufacturing research due to their low energy consumption,high efficiency,and rapid turnaround time.This article introduces the modeling and simulation of hot manufacturing in single crystal blades.The discussion outlines the prevalent mathematical models employed in numerical simulations related to blade hot manufacturing.It encapsulates the advancements in research concerning macro to micro-level numerical simulation techniques for directional solidification and heat treatment processes.Furthermore,potential future trajectories for the numerical simulation of single crystal blade hot manufacturing are also discussed.

Foreign Object Damage to Fan Rotor Blades of Aeroengine Part II: Numerical Simulation of Bird Impact

Bird impact is one of the most dangerous threats to flight safety. The consequences of bird impact can be severe and, therefore, the aircraft components have to be certified for a proven level of bird impact resistance before being put into service. The fan rotor blades of aeroengine are the components being easily impacted by birds. It is necessary to ensure that the fan rotor blades should have adequate resistance against the bird impact, to reduce the flying accidents caused by bird impacts. Using the contacting-impacting algorithm, the numerical simulation is carded out to simulate bird impact. A three-blade computational model is set up for the fan rotor blade having shrouds. The transient response curves of the points corresponding to measured points in experiments, displacements and equivalent stresses on the blades are obtained during the simulation. From the comparison of the transient response curves obtained from numerical simulation with that obtained from experiments, it can be found that the variations in measured points and the corresponding points of simulation are basically the same. The deforming process, the maximum displacements and the maximum equivalent stresses on blades are analyzed. The numerical simulation verifies and complements the experiment results.

Experimental Study and Numerical Simulation of Directionally Solidified Turbine Blade Casting

The directional solidification process of turbine blade sample castings was investigated in the work. Variable withdrawal rates were used in one withdrawal process and compared with the other using uniform rate. A mathematical model for heat radiation transfer and microstructure simulation of directional solidification process was developed based on CA-FD method. The temperature distribution and microstructure w.ere simulated and compared with the experimental results. The stray grains were predicted and compared with the experimental results. The uneven temperature distribution of platform was the main reason of the formation of stray grains.

Numerical simulation of cavitation turbulence in Francis turbine runner with splitter blades

Cavitation will reduce the turbine performance and even damage the turbine components.To verify the effects of splitter blades on improving the cavitation performance,the cavitation flow inside a Francis turbine runner with splitter blades was numerically simulated by using the Singhal cavitation model and the standard k-ε turbulence model.The distributions of static pressure and gas volume fractions on the surface of the runner blades were predicated under different conditions,and the cavitation in the flow field of the runner was analyzed.The results show that the static pressure and gas volume fractions are more uniformly distributed on the short blades than those on the long blades in Francis turbines with splitter blades,and there is almost no cavitation on the short blades;their distributions are more uniform under small flow conditions than those under large flow conditions;and large gas volume fractions are concentrated at the outlet tip near the band on the suction side of the long blade.The installation of splitter blades can improve the cavitation performance of conventional Francis turbines.

Numerical simulation of a thixocasting process for AISI420 stainless steel air-turbine blade

A new technology,semi-solid casting(thixocasting) method,was used to replace the conventional hot forging process to form AISI420 stainless steel air-turbine blade.The power law cut-off(PLCO) material model in Procast software was used to simulate the thixocasting process.The thixocasting process was simulated.The results show that the reasonable technology parameters for air-turbine blade thixocasting process are obtained:billet temperature 1 483-1 485 °C,piston velocity 12-15 m/s and die temperature is about 400 °C.

Numerical Simulation of Water Droplets Deposition on the Last-Stage Stationary Blade of Steam Turbine

Based on the method of discrete phase, the law of droplets’ deposition in the last stage stationary blade of a supercritical 600 MW Steam Turbine is simulated in the first place of this paper by using the Wet-steam model in commercial software FLUENT, where the influence of inlet angle of water droplets of the stationary blades is also considered. Through the calculation, the relationship between the deposition and the diameter of water droplets is revealed. Then, the amount of droplets deposition in the suction and pressure surface is derived. The result is compared with experimental data and it proves that the numerical simulation result obtained in this paper is reasonable. Finally, a formula of the relationship between the diameter of water droplets and the inlet angle is fit, which could be used for approximate calculation in the engineering applications.

Tests and numerical simulation on curved blade of super-critical adjust stage

Tests and numerical simulations of super-critical adjust stage blade were carried out and the effect of bowed blade on flow characteristics and the secondary flow were analyzed. The simulation and test results show that the adjust stage blade with aft-loading and big front-edge radius has good flow characteristics by meridian shrink. The numerical studies were carried out with software of NUMECA in order to investigate the aerodynamic characteristics of adjust stage blades,which include prototype blade(tested blade) ,positive curved blade (15°) and negative curved blade(-15°) . The simulation results show that the positive curved blade forms a negative static pressure gradient in the lower region of the cascade along the blade height and a positive static pressure gradient in the upper region. This leads to the reduction of the streamwise vortices intensity and the aerodynamic load on both sides of the blade and the endwall. Therefore,the crosswise secondary flow losses of endwall can be decreased considerably.

Influence of Blade Wrap Angle on Centrifugal Pump Performance by Numerical and Experimental Study

The existing research on improving the hydraulic performance of centrifugal pumps mainly focuses on the design method and the parameter optimization. The traditional design method for centrifugal impellers relies more on experience of engineers that typically only satisfies the continuity equation of the fluid. In this study, on the basis of the direct and inverse iteration design method which simultaneously solves the continuity and motion equations of the fluid and shapes the blade geometry by controlling the wrap angle, three centrifugal pump impellers are designed by altering blade wrap angles while keeping other parameters constant. The three-dimensional flow fields in three centrifugal pumps are numerically simulated, and the simulation results illustrate that the blade with larger wrap angle has more powerful control ability on the flow pattern in impeller. The three pumps have nearly the same pressure distributions at the small flow rate, but the pressure gradient increase in the pump with the largest wrap angle is smoother than the other two pumps at the design and large flow rates. The pump head and efficiency are also influenced by the blade wrap angle. The highest head and efficiency are also observed for the largest angle. An experiment rig is designed and built to test the performance of the pump with the largest wrap angle. The test results show that the wide space of its efficiency area and the stability of its operation ensure the excellent performance of the design method and verify the numerical analysis. The analysis on influence of the blade wrap angle for centrifugal pump performance in this paper can be beneficial to the optimization design of the centrifugal pump.

Numerical investigation on bowed blades of large meridional expansion Turbine

To improve the performance of the Turbofan engine,several measures should be considered during design process.Such measures,relating to aerodynamic characteristic design,include the maximum enthalpy per stage,the shortest axial length,the minimum blade rows and the highest efficient in design and off design condition.To satisfy theses design characters,the meridian geometry of the engine will be excurvature at a high degree transition part between HP and LP turbines.The study is to investigate the effect of blade bowing on flow loss at blade tip and root of the type of turbine.Such turbine,tending towards separation,with severe secondary flow at the tip and strong radial flow at exit,was simulated by the 3D N-S solver Numerca,and there were several different stacking line bowing schemes in all.The results show that tip negative bowing and root positive bowing is able to weaken radial flow,consequently reduce the flow loss at the tip and root.

Numerical modelling and simulation analysis of wind blades:a critical review

Wind energy has emerged as a promising renewable energy source and wind turbine technology has developed rapidly in recent years.Improved wind turbine performance depends heavily on the design and optimization of wind blades.This work offers a critical evaluation of the state of the art in the field of numerical modelling and simulation analysis,which have become crucial for the design and optimization of wind blades.The evaluation of the literature includes considerable research on the application of numerical methods for the structural and aerodynamic performance of wind blades under various operating situations,as well as for analysis and optimization of wind blades.The article illustrates how numerical techniques can be used to analyse wind blade performance and maximize design efficiency.The study of blade performance under various wind conditions has also been made possible through the use of simulation analysis,thus enhancing the efficiency and dependability of wind turbines.Improvements in wind turbine efficiency and dependability,and ultimately the move towards a more sustainable energy future,will be greatly helpful for the development of numerical modelling and simulation techniques.

Numerical study on hydraulic performance of submerged propellers in oxidation ditch

The submerged propeller is an efficient diving mix device,which is applicable for oxidation ditch treatment in industry,city and village wastewater-treatment plant. The impeller structure and reasonable rotating speed are important factors that determine flow field distribution and energy conversion efficiency. So it is necessary to use modern design methods to develop new kinds of high efficiency submerged propellers,and research the flow field characteristics of submerged propellers. On the basis of the existing form drawing,three-dimensional model of submerged propellers and unstructured tetrahedral mesh were generated. Based on Navier- Stokes equations and standard k- ε turbulence model,the flow was simulated by using a simple algorithm. Through changing some design parameters of propellers,the corresponding numerical simulation results reveal that for the same impeller diameter and service area of submerged propellers,the power consumption could be reduced effectively by optimizing blade mounting angle,which can determine the best blade mounting angle and most suitable rotational speed under given conditions. The study can provide theoretical and project guidance for submerged propellers design.

Numerical simulation of microstructure evolution during directional solidification process in directional solidified (DS) turbine blades

Directional solidified(DS) turbine blades are widely used in advanced gas turbine engine. The size and orientation of columnar grains have great influence on the high temperature property and performance of the turbine blade. Numerical simulation of the directional solidification process is an effective way to investigate the grain's growth and morphology,and hence to optimize the process. In this paper,a mathematical model was presented to study the directional solidified microstructures at different withdrawal rates. Ray-tracing method was applied to calculate the temperature variation of the blade. By using a Modified Cellular Automation(MCA) method and a simple linear interpolation method,the mushy zone and the microstructure evolution were studied in detail. Experimental validations were carried out at different withdrawal rates. The calculated cooling curves and microstructure agreed well with those experimental. It is indicated that the withdrawal rate affects the temperature distribution and growth rate of the grain directly,which determines the final size and morphology of the columnar grain. A moderate withdrawal rate can lead to high quality DS turbine blades for industrial application.

Numerical simulation of icing effects on static flow field around blade airfoil for vertical axis wind turbine

Icing on blade surface of the straight-bladed vertical axis wind turbine(SB-VAWT)set in cold regions is a serious problem.To study the performance effects of icing on SB-VAWT,numerical simulations were carried out on the ice accretion on NACA 0015 airfoil which was always used for blade airfoil of SB-VAWT by CFD methods based on 2D steady incompressible N-S Equation.The morphology and procedure of icing on blade airfoil were obtained under different wind speeds,attack angles of blade and water flow flux in wind.The static flow fields,especially the static pressure fields around blade airfoil with or without icing on it were computed.The aerodynamic characteristics including the lift and drag force coefficients of blade airfoil were also calculated.The results indicated that icing caused the static pressure field changed greatly and led to the increasing of drag force and reducing the aerodynamic performance.

Determination of wax pattern die profile for investment casting of turbine blades

In order to conform to dimensional tolerances, an efficient numerical method, displacement iterative compensation method, based on finite element methodology （FEM） was presented for the wax pattern die profile design of turbine blades. Casting shrinkages at different positions of the blade which was considered nonlinear thermo-mechanical casting deformations were calculated. Based on the displacement iterative compensation method proposed, the optimized wax pattern die profile can be established. For a A356 alloy blade, substantial reduction in dimensional and shape tolerances was achieved with the developed die shape optimization system. Numerical simulation result obtained by the proposed method shows a good agreement with the result measured experimentally. After four times iterations, compared with the CAD model of turbine blade, the total form error decreases to 0.001 978 mm from the orevious 0.515 815 mm.

CFX-BladeGen在涡轮叶片造型中的应用

涡轮钻具中的主要元件是由定子和转子组成的涡轮,它的作用是把液体能变为主轴上的机械能.将CFX-BladeGen应用于涡轮钻具叶片的造型,并对生成的模型进行数值模拟计算.计算结果与同类型涡轮钻具台架实验的数据比较表明,CFX-BladeGen可以比较方便、快捷地满足涡轮叶片造型要求.

Effect of blade tilt angle on fluid flow characteristics in spray-blowing agitation composite process:a simulation

Aiming at the paddle tilt angle of the spray-blowing agitation composite process,the four-blade stirring and blowing composite desulfurization agitator was chosen as the research object,and the computational fluid dynamics numerical simulation was used to investigate the changes in flow field velocity,turbulent kinetic energy magnitude,and distribution caused by the blade tilt angle.Furthermore,the impact of blade tilt angle on the flow fragmentation behavior of individual bubbles and the coalescence process of multiple bubbles at different positions was studied.Under the same stirring and blowing process parameters,with the increase in the blade tilt angle of the agitator,the velocity of the flow field and the average turbulent kinetic energy inside the agitator decreased,and the bubble fragmentation speed decreased while the merging speed accelerated.The turbulent kinetic energy at the agitator bottom was greater when the blade tilt angle was 3.2°compared to when it was 13.2°,while the turbulent kinetic energy at the agitator upper part was relatively smaller.The results for single bubbles represented the state and trajectory of the bubble fragmentation process,and the results for multiple bubbles illustrated the state and trajectory of the bubble aggregation process.

Hybrid LES/RANS Simulations of Compressible Flow in a Linear Cascade of Flat Blade Profiles

The paper reports on 3D numerical simulations of unsteady compressible airflow in a blade cascade consisting of flat profiles using a hybrid LES/RANS approach including a transition model.As a first step towards simulation of blade flutter in turbomachinery,various incidence angle offsets of the middle blade were modeled.All simulations were run for the flow regime characterized by outlet isentropic Mach number M_(is)=0.5and zero incidence.The results of the LES/RANS simulations(pressure and Mach number distributions)were compared to a baseline RANS model,and to experimental data measured in a high-speed wind tunnel.The numerical results show that both methods overpredict flow separation taking place at the leading edge.In this regard,the hybrid LES/RANS method does not provide superior results compared to the traditional RANS simulations.Nevertheless,the LES/RANS results also capture vortex shedding from the blunt trailing edge.The frequency of the trailing edge vortex shedding in CFD simulations matches perfectly the spectral peak recorded during wind tunnel measurements.

Unsteady Numerical Simulation of Steam-Solid Two-Phase Flow in the Governing Stage of a Steam Turbine

Solid particle erosion (SPE) in an ultra-supercritical steam turbine control stage with block configuration is investigatednumerically, based on the finite volume method and the fluid-particle coupling solver. We apply the particlediscrete phase model to model the solid particles flow, and use the Euler conservation equations to solve thecontinuous phase. The investigation is focused on the influence of the solid particle parameters (such as particlediameter, particle velocity and particle trajectory) on the erosion rate of the stator and rotor blade surface in unsteadycondition. The distributions of the highly eroded zone on the stator and rotor blade surfaces are shown anddiscussed in detail according to the mechanism of solid particle/blade wall interaction. We obtain that the erosionrate of the vane blade is sensitive to the fluctuation of the potential flow field, and the smaller particle has agreater impact on the erosion distribution of rotor blade. The erosion rate does not entirely depend on the diametersize of the solid particle.

Numerical simulation of a rotary engine primary compressor impacted by bird

In order to examine the process of a rotary engine primary compressor impacted by bird, a finite element model of a bird impacted on plate is developed with the explicit code PAM-CRASH. The smooth particles hydrodynamic （SPH） method is used to simulate the bird because of the SPH method showing no signs of instability and correctly modeling the breaking-up of the bird into particles. Good agreement between the simulation results and experimental results indicates that the numerical method of bird strike used in the present paper is reasonable. Then a rotary engine primary compressor impacted by three different configurations bird named straight-ended cylinder bird, quadrangular bird, hemispherical-ended bird are investigated using the numerical simulation method. It is found that the whole process of bird strike sustained about 3.5 ms and the bird is slashed by blade during the strike. The geometry configuration of bird affected the displacement and von Mises stress of some blades severely, just because the breaking bird＇s mass is affected by the bird＇s configuration. In the event of bird striking on the site of＂up＂some blades may develop plastic deformation and it is very adverse for the safety work of the engine.

Analysis of the Influence of the Blade Deformation on Wind Turbine Output Power in the Framework of a Bidirectional Fluid-Structure Interaction Model

The blades of large-scale wind turbines can obviously deform during operation,and such a deformation can affect the wind turbine’s output power to a certain extent.In order to shed some light on this phenomenon,for which limited information is available in the literature,a bidirectional fluid-structure interaction(FSI)numerical model is employed in this work.In particular,a 5 MW large-scale wind turbine designed by the National Renewable Energy Laboratory(NREL)of the United States is considered as a testbed.The research results show that blades’deformation can increase the wind turbine’s output power by 135 kW at rated working conditions.Compared with the outcomes of the simulations conducted using the model with no blade deformation,the results obtained with the FSI model are closer to the experimental data.It is concluded that the bidirectional FSI model can replicate the working conditions of wind turbines with great fidelity,thereby providing an effective method for wind turbine design and optimization.