The Study Of High Load Ow-pressure-tuibine Lade Suction Boudary Layer Flow

Aero-engine is a key component of the aircraft, known as the aircraft’s "heart", is toprovide power, and its performance directly affects the overall performance of theaircraft and even determines the level. Low-pressure turbine is one of the corecomponents of aero-engine which is used to drive the fan and booster stage, the hightemperature and pressure which come from combustor in turn impact high and lowpressure turbine acting, internal flow field organization directly affects thelow-pressure turbine aerodynamic efficiency, while the aerodynamic and engineperformance and efficiency is directly related. The study found that when thelow-pressure turbine efficiency improve by1%is equivalent to0.5-1.0%loss on oil;Furthermore, since the low-pressure turbine stages and the number of compostion partsare more, which can account for20-30%of the total weight of the engine weight. Dueto the relative rotation between the blade rows, the flow inside the low pressure turbineblade surface is in a very complex environment, including their own unsteady effects,upstream wake and flow turbulence. Practical applications, some of the smaller size ofthe aircraft itself, the small size of its engine, coupled with the high-flying air sparse,resulting in very low Reynolds number flow, so the blade surface flow is laminar statewhich can not resistant the strong adverse pressure gradient,it will lead extremeaerodynamic loss, so that the sharp decline in the efficiency of the engine in addition toaffect the life of turbine components. So it is neccessary to improve the internal flow ofthe low-pressure turbine blade surface whether in order to improve engine efficiency orfurther reduced the engine size.Evolution under different boundary conditions boundary layer flow are not thesame mechanism, in which the simplest and most common is the open boundary layerflow around objects,such flows without obstacles’ constraint, while the low-pressureturbine is typical internal flow without constraint. This paper use the self-developed"multi-block parallel Large Eddy Simulation Program"(MPLES) which has feature ofhigh computational efficiency and high accuracy to compute the external flow forairfoil and low-pressure turbine,from shallow into the deep, to better reveal theevolution of the low pressure turbine internal flow mechanism.Start with a simple text NACA-0025airfoil analysis of flow, the purpose is tobetter comparison, but also to a deeper understanding of the flow within the LPT flow mechanism to prepare. Through the coparison between large eddy simulation resultsand experimental data, indicating that the large eddy simulation results are credible.And to capture the flow field by more detailed data, time-averaged, higher orderstatistics, two-dimensional, transient flow analysis and spectrum analysis, such as vividthree-dimensional display of the flow of the entire evolutionary process andrecognizing airfoil mechanism of flow: the KH instability after the free shear layerseparation has a significant impact on the flow of development, small perturbationsgradually enlarge due to the KH instability, and then evolved into a three-dimensionalfluctuations, which will lead to spanwise vortex deformation along the spanwise vortexflow growth, adjacent vortex structure and the pairing interaction until fused togetherto form a new vortex structure, the structure of the final vortex is unstable, and theentire flow instability transition into a turbulent flow at the end.The model of research on the low-pressure turbine blade model flow suctionsurface of a turbine blade surface boundary layer is simplied blade model by professorHodson at the University of Cambridge Hodson model.A large eddy simulation (LES)were calculated and analyzed on two different boundary layer conditions: uniform flowand turbulence intensity flow. The results showed that the uniform flow has poorability to resist separation of the boundary layer, forming a large open separation zoneand momentum losses. And the flow with turbulent flow will transition in advance sothat the separation zone will be greatly reduced,at same time the smaller loss ofmomentum. In a word which will greatly improve the efficiency of the engine.