Nominal Vane Research Articles

Effect of Nozzle Guide Vane Lean Under Influence of Inlet Temperature Traverse

One of the most widely studied parameters in turbine blade shaping is blade lean, i.e., the tangential displacement of spanwise sections. However, there is a lack of published research that investigates the effect of blade lean under nonuniform temperature conditions (commonly referred to as a “hot-streak”) that are present at the combustor exit. Of particular interest is the impact of such an inflow temperature profile on heat transfer when the nozzle guide vane (NGV) blades are shaped. In the present work, a computational study has been carried out for a transonic turbine stage using an efficient unsteady Navier–Stokes solver (HYDRA). The configurations with a nominal vane and a compound leaned vane under uniform and hot-streak inlet conditions are analyzed. After confirming the typical NGV loading and aeroloss redistributions as seen in previous literature on blade lean, the focus has been directed to the rotor aerothermal behavior. While the overall stage efficiencies for the configurations are largely comparable, the results show strikingly different rotor heat transfer characteristics. For a uniform inlet, a leaned NGV has a detrimental effect on the rotor heat transfer. However, once the hot-streak is introduced, the trend is reversed; the leaned NGV leads to favorable heat transfer characteristics in general and for the rotor tip region in particular. The possible causal links for the observed aerothermal features are discussed. The present findings also highlight the significance of evaluating NGV shaping designs under properly conditioned inflow profiles, rather than extrapolating the wisdom derived from uniform inlet cases. The results also underline the importance of including rotor heat transfer and coolability during the NGV design process.

Low-Heat-Load-Vane Profile Optimization, Part 2: Short-Duration Shock-Tunnel Experiments

Complete knowledge of the heat transfer over the surfaces of turbine components within their harsh operating environments is key to knowing the durability of a given airfoil design. Here, a nominal turbine inlet vane was tested for unsteady-heat-load measurements in a low-aspect-ratio linear cascade. A new airfoil called the low-heat-load vane, designed specifically for a reduced heat load, was tested experimentally and unsteady-heat-load trends were compared with the nominal vane counterpart. The tests were performed in a reflected-shock tunnel to validate the flow solver and turbomachinery design system used to generate the new airfoil shape, for which special attention was paid to leading-edge and suction-side heat-flux characteristics. Results indicate an appreciable reduction in heat load relative to the nominal vane. This work lends credibility to designing turbine airfoils for durability with the same emphasis normally given to designing for aeroperformance.

Low-Heat-Load-Vane Profile Optimization, Part 1: Code Validation and Airfoil Redesign

Historically, there has been a distinct difference between the design of turbomachinery airfoils for aerodynamic performance and that for durability. However, future aeroengine systems will require ever-increasing levels of turbine inlettemperature, causing the durability andreliability of components to be anever-more-important design concern. As a result, the need to incorporate heat-transfer predictions into traditional aerodynamic design and optimizationsystems presents itself.Thefollowing isaneffortto designaminimized-heat-load airfoilwith reputable aerodynamics. A Reynolds-averaged Navier–Stokes flow solver is validated over different flow regimes and various boundary conditions against extensive data available in literature. A nominal vane airfoil midspan profile is redesigned for minimum heat load by means of both design practice and two types of optimization algorithms. Resultsindicateanappreciablereductionintheoreticalheatloadrelativetotheoriginalvane;peakleading-edgeheat transfer was reduced and suction-surface transition onset was delayed significantly. A method for two-dimensional design optimization for aerodynamics and heat load is successfully demonstrated.

The Effect of Rotation Rate on Gel Strength and Dynamic Yield Strength of Thixotropic Oil Well Cements Measured Using a Shear Vane

A six‐bladed vane was used to measure the gel strength and dynamic yield strength of a thixotropic cement slurry of a type used in oil well cementing. It was established that when the combined parameters of rotation speed, measuring system stiffness, and gel strength give a time to maximum torque of less than 100 milliseconds, sophisticated data recording systems are necessary. It is shown that gel strength is only marginally affected by nominal vane rotation speed between 0.06 and 6 rpm whereas dynamic yield strength is sensitive to rotation rate in this speed range.