The Development of Highly Loaded Turbine Rotating Blades by Using 3D Optimization Design Method of Turbomachinery Blades Based on Artificial Neural Network & Genetic Algorithm

In order to improve turbine internal efficiency and lower manufacturing cost, a new highly loaded rotating blade has been developed. The 3D optimization design method based on artificial neural network and genetic algorithm is adopted to construct the blade shape. The blade is stacked by the center of gravity in radial direction with five sections. For each blade section, independent suction and pressure sides are constructed from the camber line using Bezier curves. Three-dimensional flow analysis is carried out to verify the performance of the new blade. It is found that the new blade has improved the blade performance by 0.5%. Consequently, it is verified that the new blade is effective to improve the turbine internal efficiency and to lower the turbine weight and manufacturing cost by reducing the blade number by about 15%.

Nonlinear dynamic behavior of rotating blade with breathing crack

This study aims at investigating the nonlinear dynamic behavior of rotating blade with transverse crack.A novel nonlinear rotating cracked blade model(NRCBM),which contains the spinning softening,centrifugal stiffening,Coriolis force,and crack closing effects,is developed based on continuous beam theory and strain energy release rate method.The rotating blade is considered as a cantilever beam fixed on the rigid hub with high rotating speed,and the crack is deemed to be open and close continuously in a trigonometric function way with the blade vibration.It is verified by the comparison with a finite element-based contact crack model and bilinear model that the proposed NRCBM can well capture the dynamic characteristics of the rotating blade with breathing crack.The dynamic behavior of rotating cracked blade is then investigated with NRCBM,and the nonlinear damage indicator(NDI)is introduced to characterize the nonlinearity caused by blade crack.The results show that NDI is a distinguishable indicator for the severity level estimation of the crack in rotating blade.It is found that severe crack(i.e.,a closer crack position to blade root as well as larger crack depth)is expected to heavily reduce the stiffness of rotating blade and apparently result in a lower resonant frequency.Meanwhile,the super-harmonic resonances are verified to be distinguishable indicators for diagnosing the crack existence,and the third-order super-harmonic resonances can serve as an indicator for the presence of severe crack since it only distinctly appears when the crack is severe.

Subharmonic and Combination Resonance of Rotating Pre-deformed Blades Subjected to High Gas Pressure

The present paper deals with the investigation of dynamic responses of a rotating pre-deformed blade in four cases of resonance,including two subharmonic resonances and two combination resonances.The dimensionless gas excitation amplitude is assumed to share the same order with the dimensionless vibration displacement.Four cases of resonance are confirmed by examining the secular terms.The theoretical analysis framework is established for each resonance case based on the method of multiple scales.The original dynamic system is integrated numerically by the Runge–Kutta method.The frequency components and phases obtained from fast Fourier transform of the numerical response are used to verify the theoretical results.For the purpose of contrast,modulation equations are also integrated numerically.In all four resonance cases,the theoretical results agree well with the numerical simulation.Parameter studies are conducted to clarify the effects of system parameters on the perturbation curves.Various results are obtained for the rotating blade.A quasi-saturation phenomenon occurs in both combination resonances of summed type and difference type,and the corresponding limit value of the second-mode response can be reduced by decreasing the external detuning parameter.The quasi-saturation phenomenon of rotating blade only appears with high gas pressure.The subharmonic resonance of second mode and the combination resonance of summed type are hard to excite in practice compared with the other two cases.

Featureless Zone in Rapidly Solidified Aluminum Alloy Splats

The microstructures of rapidly solidified (RS) Al-Fe-Ce-Ti and Al-Fe-V-Si alloys obtained by means of rotating blade quenching were studied with optical microscopy,transmission electron microscopy (TEM).The featureless zone observed in the two alloys reveals that the new technique offers a higher solidification rate than the inert-gas-atomized method.Under TEM observation the featureless zone presents virtually a micropartition or partitionless feature,and the solute contents in it are almost the same as the chemical composition of alloys.

Nonlinear transient responses of rotating twisted FGM cylindrical panels

This paper develops a new structure dynamic model to investigate nonlinear transient responses of the rotating blade made of functionally graded material(FGM). The rotating blade is simplified as a rotating FGM cylindrical panel with a presetting angle and a twist angle. The geometric nonlinearity effects are taken into account in the strain-displacement relationships, which are derived by Green strain tensor. Based on the first-order piston theory and the first-order shear deformation theory, the equations of motion for the rotating twisted FGM cylindrical panel are acquired by means of Hamilton principle and Galerkin method.Backward Differentiation Formula(BDF) and Runge-Kutta Algorithm are used to solve the nonlinear equations of motion for the system. The effects of four pulse load conditions on the system subjected to the internal pulse load or the external pulse load are fully discussed. A detailed parametric analysis is performed by considering the effects of the rotating speed, volume fraction index and temperature.

Effects of blade rotation angle deviations on mixed-flow pump hydraulic performance

By model test and numerical simulation, this paper analyzed the effects of different blades with varying rotation angle deviations on the hydraulic performance of a mixed-flow pump. It was found that when some blades had rotation angle deviations, the hydraulic performance curves of the mixed-flow pump would move. With a positive deviation, the curves moved towards the large flow rate; with a negative deviation, the curves moved towards the small flow rate. When some blades had rotation angle deviations, the symmetry and uniformity of the pressure distribution inside the mixed-flow pump flow passage both decreased; the larger the deviation, the greater the decrease. When a single blade had a large rotation angle deviation, a rather clear low pressure area was formed, lowering the cavitation performance. When two adjacent blades changed simultaneously, under the small flow rate condition, adverse pressure gradient and flow separation occurred in the flow field, and a hump appeared in the head curve and the operation stability of the mixed-flow pump dropped significantly. Near the best efficiency point（BEP）, the simultaneous change of two alternate blades produced a more significant change of pressure in the flow passage, with an even larger area. Compared to the effect of two adjacent blades, two alternate blades, when changed simultaneously, made the mixed-flow pump slightly less efficient, but with a flatter efficiency curve and relatively wider high efficiency area. By fitting the test results, a functional relation among the BEP of the mixed-flow pump QBEP, the number of deviated blades N, and blade rotation angle deviation α was established, thus realizing an effective prediction of the BEP of the mixed-flow pump when blade rotation angles have deviations.

Effect of the Uneven Circumferential Blade Space on the Performance of Small Axial Flow Fan

Effects of the uneven circumferential blade space on static characteristics and aerodynamic noise of a small axial flow fan are studied in this work.The blade angle modulation is adopted to design a series of unequally spaced fans,which have different maximum of modulation angular displacement.The steady flow is simulated by the calculations of Navier-Stokes equations coupled with RNG k-epsilon turbulence model,while the unsteady flow is computed with large eddy simulation.According to theoretical analysis,a fan with a maximum of modulation angular displacement of 6° is regarded as the optimal unequally spaced fan.The experiment of static characteristic is carried out in a standard wind tunnel and the aerodynamic noise of both fans is tested in a semi-anechoic room.Then,performances of the optimal unequally spaced fan are compared with those of the prototype fan.The results show that there is reasonable agreement between the simulation results and the experimental data.It is found that the discrete noise of the optimal unequally spaced fan is lower than that of the prototype fan at the near field monitoring point.This can be explained that the total pressure fluctuation of the optimal unequally spaced fan is much more regular than that of the prototype fan.

Numerical Investigation of Effect of Inlet Swirl and Total-pressure Distortion on Performance and Stability of an Axial Transonic Compressor

This paper represents numerical simulation of flow inside an axial transonic compressor subject to inlet flow distortion,to evaluate its effect on compressor performance and stability.Two types of inlet distortion,namely inlet swirl and total pressure distortion are investigated.To study the effect of combined distortion patterns,different combinations of inlet swirl and total pressure distortion are also studied.Results for cases with total pressure distortion indicate that hub radial distortion improves stability range of the compressor while tip radial distortion deteriorates it.An explanation for this observation is presented based on redistribution of flow parameters caused by distortion and the way it interacts with stall inception mechanisms in a transonic axial compressor.Results also show that while co-swirl patterns slightly improve stability range of the compressor,counter-swirl patterns diminish it.Study of combined distortion cases reveals that superimposition of effects of each individual pattern could predict the effect of a combined pattern on compressor's performance within an accuracy of 1%.However,it is unable to predict the associated effect on compressor's stability.