Research On Flow And Heat Transfer Performance Of Special-shaped Column Pin-fin On The Trailing Edge Of Turbine Blades

The geometric structure at the trailing edge of the turbine blade is relatively special,so pin-fin cooling and split flow has become the first choice for the current advanced blade cooling structure.The cooling fluid comes from the inter-stage extraction of the compressor,for improve the overall turbine efficiency.At present,people have been committed to using a smaller amount of cooling fluid to provide better heat transfer,which means that the cooling structure is facing greater challenges.It is extremely important to find a balance between improving the heat transfer enhancement effect and reducing the resistance loss,as an important research direction.From the perspective of the flow method,the cooling of pin-fin has a complicated flow and heat transfer mechanism,and it has the characteristics of both external flow and internal flow.The existence of pin-fin causes the fluid to disintegrate during the turbulence process,forming a complex detachment vortex system behind the pin-fin.The front edge of the pin-fin is directly impacted by the cooling fluid,which significantly enhances heat transfer.At this moment,it appears as external flow,the existence of pin-fin in the channel also increases the degree of turbulence in the flow field,causing the flow boundary layer on the end wall to break and reattach.The thermal boundary layer also undergoes a re-establishment process to enhance heat transfer.Heat transfer enhancement and resistance loss increase are two common contradictions in the field of heat transfer.The study of the flow mechanism has the significance of tracing the origin.Therefore,this paper carried out the following research.First,the flow characteristics of the cylindrical pin-fin with different cross-sectional shapes(drop-shaped,circular,elliptical)were studied,and the flow characteristics and the vortex composition behind the cylindrical pin-fin were explored to understand the resistance loss mechanism of the spoiler pin-fin and the periodic changes between the pin-fin rows.When the water-drop-shaped pin-fin are found to be turbulent,the boundary layer separation point is more rearward than the other two shapes of pin-fin,which means that the resistance loss is in progress.The viscosity loss rather than the differential pressure loss accounts for a larger part,which points out the direction for greatly reducing the resistance loss.From the perspective of heat transfer performance,in the inner surface of the channel,the front edge surface of the pin-fin is directly impacted by the cooling fluid.The number is the highest.Starting from the principle of field synergy of heat transfer,not only the velocity field and the heat flow vector field at the front edge of the pin-fin have a more higher degree of synergy,but the modes of the two vectors are larger here,so good heat transfer can be formed.Based on the great advantages of drop-shaped pin-fin in terms of resistance loss,resulting in higher overall thermal efficiency,we continue to seek reasonable geometric arrangements to make the heat transfer enhancement more significant,so the next three single factors(windward angle,spread The law of flow and heat transfer under the influence of vertical spacing and pin-fin height)was studied,and it was found that the change of the windward angle and pin-fin height increased the effective heat transfer enhancement area on the pin-fin surface,and the reduction of spanwise spacing also increased the exchange rate.Thermal strength,but at the same time,it also brings an increase in resistance loss,mainly due to the drastic change of the flow cross-sectional area,which makes the fluid mixing violently in the spanwise direction.Finally,the response surface method is used to optimize the flow and heat transfer laws under various influencing factors,and the best geometrical arrangement form of the balance point of heat transfer enhancement,resistance loss,and comprehensive thermal efficiency is obtained.Considering the geometric structure and flow mode of the real turbine blades,the flow model considering the lateral outflow in the wedge-shaped channel is re-established,and the best geometrical arrangement obtained above is adopted to explore the application of the new drop-shaped pin-fin to the actual blades.,The results show that,compared with the circular pin-fin under the same arrangement,the drop-shaped pin-fin still have greater advantages in terms of overall thermal efficiency.The specific performance is that the resistance loss is significantly reduced when the heat transfer is increased.When the inlet Reynolds number is20,000,the ratio of the dimensionless Nusselt number is increased by 1.4%,the resistance loss is reduced by 22.1%,and the overall thermal efficiency is also increased by 10.3%.