Directional solidification casting technology of heavy-duty gas turbine blade with liquid metal cooling(LMC) process

In this work, some important factors such as ceramic shell strength, heat preservation temperature, standing time and withdrawal rate, which influence the formability of directionally solidified large-size blades of heavy-duty gas turbine with the liquid metal cooling(LMC) process, were studied through the method of microstructure analysis combining. The results show that the ceramic shell with medium strength(the high temperature flexural strength is 8 MPa, the flexural strength after thermal shock resistance is 12 MPa and the residual flexural strength is 20 MPa) can prevent the rupture and runout of the blade. The appropriate temperature(1,520 ℃ for upper region and 1,500 ℃ for lower region) of the heating furnace can eliminate the wide-angle grain boundary, the deviation of grain and the run-out caused by the shell crack. The holding time after pouring(3-5 min) can promote the growth of competitive grains and avoid a great deviation of columnar grains along the crystal orientation <001>, resulting in a straight and uniform grain structure. In addition, to avoid the formation of wrinkles and to ensure a smooth blade surface, the withdrawal rate should be no greater than the growth rate of grain. It is also found that the dendritic space of the blade decreases with the rise of solidification rate, and increases with the enlarging distance between the solidification position and the chill plate.

Study on Rotational Effects of Modern Turbine Blade on Coolant Injecting Nozzle Position with Film Cooling and Vortex Composite Performance

The flow structure of the vortex cooling is asymmetrical compared to the traditional gas turbine leading edge cooling,such as the impingement cooling and the axial flow cooling.This asymmetrical property will affect the cooling performance in the blade leading edge,whereas such effects are not found in most of the studies on vortex cooling due to the neglect of the mainstream flow in the airfoil channel.This study involves the mainstream flow field and the rotational effects based on the profile of the GE E3 blade to reveal the mechanism of the asymmetrical flow structure effects.The nozzle position on the characteristics of the vortex and film composite cooling in the turbine rotating blade leading edge is numerically investigated.The cool-ant injecting nozzles are set at the side of the pressure surface(PS-side-in)vs.that is set at the side of the suction surface(SS-side-in)to compare the cooling characteristics at the rotating speed range of 0–4000 rpm with fluid and thermal conjugate approach.Results show that the nozzle position presents different influences under low and higher rotational speeds.As for the mainstream flow,rotation makes the stagnation line move from the pressure surface side to the suction surface side,which changes the coolant film attachment on the blade leading edge surface.The position of nozzles,however,indicates limited influence on the coolant film flow.As for the internal channel vortex flow characteristics,the coolant injected from the nozzles forms a high-velocity region near the target wall,which brings about enhancing convective heat transfer.The flow direction of the vortex flow near the internal channel wall is opposite and aligns with the direction of Coriolis force in both the PS-side-in and SS-side-in,respectively.Therefore,the Coriolis force augments the convective heat transfer intensity of the vortex cooling in the internal channel in SS-side-in while weakening the internal heat transfer in PS-side-in.Such effects become more intense with higher rotational speed.The blade surface temperature decreases as the Coriolis force increases the internal heat transfer intensity.The SS-side-in suggests a superior composite cooling performance under the relatively higher rotating speed.The SS-side-in structure is recommended in the gas turbine blade leading edge running at a higher rotating speed.

A review of recent studies on rotating internal cooling for gas turbine blades

Gas turbines have been used extensively for aircraft and marine propulsions as well as land-based power generation because of their high thermal efficiency and large power to weight ratios.To further increase the thermal efficiency,numerous prior researches on gas turbine blade internal cooling have been intensively carried out,majorly under stationary conditions.However,the stationary studies neglect the effects of Coriolis and buoyancy forces,which should change the velocity,turbulence and temperature distribution under rotating conditions.To elucidate the rotational effects on gas turbine internal cooling,the extensive results collected from recent investigations are discussed,which include the rotation and buoyancy effects on the rib turbulated cooling,pin fin cooling,jet impingement cooling,dimple/protrusion cooling,latticework cooling as well as swirl cooling.The rotational effects on the friction factors and the most employed experimental and numerical methods are also presented.Moreover,recommendations for future research are outlined.Therefore,this review article provides extensive literature information for the design of the next-generation high-efficiency internal cooling for rotating turbine blades.

Conjugate Heat Transfer Investigation on the Cooling Performance of Air Cooled Turbine Blade with Thermal Barrier Coating

A hot wind tunnel of annular cascade test rig is established for measuring temperature distribution on a real gas turbine blade surface with infrared camera.Besides,conjugate heat transfer numerical simulation is performed to obtain cooling efficiency distribution on both blade substrate surface and coating surface for comparison.The effect of thermal barrier coating on the overall cooling performance for blades is compared under varied mass flow rate of coolant,and spatial difference is also discussed.Results indicate that the cooling efficiency in the leading edge and trailing edge areas of the blade is the lowest.The cooling performance is not only influenced by the internal cooling structures layout inside the blade but also by the flow condition of the mainstream in the external cascade path.Thermal barrier effects of the coating vary at different regions of the blade surface,where higher internal cooling performance exists,more effective the thermal barrier will be,which means the thermal protection effect of coatings is remarkable in these regions.At the designed mass flow ratio condition,the cooling efficiency on the pressure side varies by 0.13 for the coating surface and substrate surface,while this value is 0.09 on the suction side.

A review of cooling technologies for high temperature rotating components in gas turbine

Modern gas turbines work under demanding high temperatures, high pressures, andhigh rotational speeds. In order to ensure durable and reliable operation, effective cooling mea-sures must be applied to the high-temperature rotating components, including turbine bladesand turbine disks. Cooling technology, however, is one of the most challenging problems inthis field. The present work reviews the current state of cooling technology research, at boththe fundamental science and engineering implementation levels, including modeling and simu-lation, experiments and diagnostics, and cooling technologies for blades and disks. In numericalsimulation, the RANS approach remains the most commonly used technique for flow-dynamicsand heat-transfer simulations. Much attention has been given to the development of improvedturbulence modeling for flows under rotation. For measurement and diagnostics, advancedinstrumentation and rotating-flow test facilities have been developed and valuable experimentaldata obtained. Detailed velocity and temperature distributions in rotating boundary layers havebeen obtained at scales sufficient to resolve various underlying mechanisms. Both isothermaland non-isothermal conditions have been considered, and the effects of Coriolis and buoyancyforces on flow evolution and heat transfer quantitatively identified. Cooling technologies havebeen improved by optimizing cooling passage dsigns, especially for curved configurations un-der rotation. Novel methods such as lamellar cooling and micro-scale cooling were proposed,and their effectiveness evaluated. For disk/cavity cooling, efforts were mainly focused on rotor-stator systems, with special attention given to the position of air injection into disks.

带扰流片的矩形直通道内的流动与换热

建立了矩形直通道内三维可压缩流动与换热模型 ,对来流雷诺数Re在 1× 10 5～ 3× 10 5范围内 ,带顺排和错排扰流片的通道内部对流换热过程进行了模拟计算。计算结果表明 ,矩形扰流片具有明显的强化冷却效果 ,扰流片表面的对流换热系数明显高于光滑表面的值 ,有扰流片区域的壁面温度明显降低 ;错排扰流片与顺排扰流片相比 ,对流换热系数增大 4 %左右。计算结果归纳了传热和流动压降关系式。

涡轮叶片通道内部V型间断肋的传热特性研究

通过模拟仿真的方法研究了涡轮叶片通道内部V型间断肋的传热特性。主要探究了各结构参数(间断位置,分离肋长度,分离肋后置距离)对通道的传热性能影响。结果表明:相对于传统的扰流肋结构(直肋,60°斜肋,60°V型肋),V型间断肋在壁面平均相对努塞尔数,综合传热系数以及温度分布均匀性上更具优势。通过改变间断参数,能大幅提高V型间断肋的综合传热系数。在研究的参数范围内,当间断位置为2.5 mm,分离肋长度为10.0 mm,分离肋后置距离为9.6 mm时,通道具有最佳的传热性能。在雷诺数为30000下,与带有直肋的通道相比,优化后的V型间断肋的平均努塞尔数提高了35.75%,综合传热系数上升了28.95%。