This paper presents an experimental investigation of the concept of using the combustor transition duct wall to shield the nozzle guide vane leading edge. The new vane is tested in a high-speed experimental facility, demonstrating the improved aerodynamic and thermal performance of the shielded vane. The new design is shown to have a lower average total pressure loss than the original vane, and the heat transfer on the vane surface is overall reduced. The peak heat transfer on the vane leading edge–endwall junction is moved further upstream, to a region that can be effectively cooled as shown in previously published numerical studies. Experimental results under engine-representative inlet conditions showed that the better performance of the shielded vane is maintained under a variety of inlet conditions.
In gas turbines with can combustors the trailing edge of the combustor transition duct wall is found upstream of ev- ery second vane. This paper presents an experimental and numerical investigation of the effect of the combustor wall trailing edge on the aerothermal performance of the nozzle guide vane. In the measurements carried out in a high speed experimental facility, the wake of this wall is shown to in- crease the aerodynamic loss of the vane. On the other hand, the wall alters secondary flow structures and has a protective effect on the heat transfer in the leading edge-endwall junc- tion, a critical region for component life. The different clock- ing positions of the vane relative to the combustor wall are tested experimentally and are shown to alter the aerothermal field. The experimental methods and processing techniques adopted in this work are used to highlight the differences be- tween the different cases studied.
The remarkable developments in gas turbine materials and cooling technologies haveallowed a steady increase in combustor outlet temperature and, hence, in gas turbine efficiencyover the last half century. However, the efficiency benefits of higher gas temperature,even at the current levels, are significantly offset by the increased losses associatedwith the required cooling. Additionally, the advancements in gas turbine cooling technologyhave introduced considerable complexities into turbine design and manufacture.Therefore, a reduction in coolant requirements for the current gas temperature levels isone possible way for gas turbine designers to achieve even higher efficiency levels. Theleading edges of the first turbine vane row are exposed to high heat loads. The high coolantrequirements and geometry constraints limit the possible arrangement of the multiplerows of film cooling holes in the so-called showerhead region. In the past, investigatorshave tested many different showerhead configurations by varying the number of rows, inclinationangle, and shape of the cooling holes. However, the current leading edge coolingstrategies using showerheads have not been shown to allow a further increase inturbine temperature without the excessive use of coolant air. Therefore, new coolingstrategies for the first vane have to be explored. In gas turbines with multiple combustorchambers around the annulus, the transition duct walls can be used to shield, i.e., to protect,the first vane leading edges from the high heat loads. In this way, the stagnationregion at the leading edge and the showerhead of film cooling holes can be completelyremoved, resulting in a significant reduction in the total amount of cooling air that is otherwiserequired. By eliminating the showerhead the shielding concept significantly simplifiesthe design and lowers the manufacturing costs. This paper numerically analyzes the potentialof the leading edge shielding concept for cooling air reduction. The vane shape wasmodified to allow for the implementation of the concept and nonrestrictive relative movementbetween the combustor and the vane. It has been demonstrated that the coolant flowthat was originally used for cooling the combustor wall trailing edge and a fraction of thecoolant air used for the vane showerhead cooling can be used to effectively cool both thesuction and the pressure surfaces of the vane.