Physics-Based Simulation in Support of a Through-Life Gas Turbine Service Business Model

The overall aim of the work reported in this paper is to explore whether a physics-based simulation approach has the potential to reduce the uncertainty & variability associated with both predicting & managing maintenance costs and improving engine design to optimise through-life economic performance. The main novelty in the paper is to demonstrate how an innovative Digital Geometry model can represent typical in-service component degradation and then support appropriate simulation meshes to permit degraded performance to be predicted. Two examples are given: blade erosion from particulates; and a simulated cooled blade burn-through event.

Experimental measurements of the flow field around a film-cooled blade leading edge using particle image velocimetry

In this article, particle image velocimetry studies were conducted in a low-speed wind tunnel to investigate the effects of blowing ratio and blade span in terms of the characteristics of the flow field around a film-cooled blade leading edge. The measurements were performed at 20%, 40%, 60%, and 80% of blade span and blowing ratios of M = 0.5, M = 0.75, M = 1, M = 1.5, and M = 2. Velocity, turbulence intensity, and structure of vortices during the interaction between cooling flow and mainstream were analyzed in detail. The analysis shows a significant increase in mainstream velocity at low blowing ratios, M < 1. Peaks of turbulence were observed at low- and high-span locations. Aerodynamical losses are expected at higher blowing ratios due to the formation of secondary vortices near the outgoing jet. These vortices were a consequence of velocity gradients at this zone.

Unsteady Heat Transfer and Pressure Measurements on the Airfoils of a Rotating Transonic Turbine With Multiple Cooling Configurations

Measurements are presented for a high-pressure transonic turbine stage operating at design-corrected conditions with forward and aft purge flow and blade film cooling in a short-duration blowdown facility. Four different film-cooling configurations are investigated: simple cylindrical-shaped holes, diffusing fan-shaped holes, an advanced-shaped hole, and uncooled blades. A rainbow turbine approach is used so each of the four blade types comprises a wedge of the overall bladed disk and is investigated simultaneously at identical speed and vane exit conditions. Double-sided Kapton heat-flux gauges are installed at midspan on all three film-cooled blade types, and single-sided Pyrex heat-flux gauges are installed on the uncooled blades. Kulite pressure transducers are installed at midspan on cooled blades with round and fan-shaped cooling holes. Experimental results are presented both as time-averaged values and as time-accurate ensemble-averages. In addition, the results of a steady Reynolds-averaged Navier–Stokes computational fluid dynamics (RANS CFD) computation are compared to the time-averaged data. The computational and experimental results show that the cooled blades reduce heat transfer into the blade significantly from the uncooled case, but the overall differences in heat transfer among the three cooling configurations are small. This challenges previous conclusions for simplified geometries that show shaped cooling holes outperforming cylindrical holes by a great margin. It suggests that the more complicated flow physics associated with an airfoil operating in an engine-representative environment reduces the effectiveness of the shaped cooling holes. Time-accurate comparisons provide some insight into the complicated interactions that are driving these flows and make it difficult to characterize cooling benefits.

Convective cooling model for aero-thermal coupled through-flow method

The aero-thermal coupled phenomenon is significant in the modern cooled turbine, and it is necessary to consider the cooling effect and predict the coolant requirement in the through-flow design. A new cooling model was developed for the aero-thermal coupled through-flow method in this paper to predict the temperatures of both the pressure and suction surfaces of the blade. Based on the given blade temperature limitation rather than the mean blade surface temperature in the formal cooling model, the coolant requirement prediction can be more accurate. The equivalent blade thickness and heat exchange area estimation methods were further developed for blades with different cooling structures, and the estimations were carried out for each calculation station instead of the whole blade. The cooled blade was divided into a few calculation stations, and the heat transfer was studied for each station. Three operating conditions for the NASA-Mark II vane were selected for the verification. The predicted temperatures of both the pressure and suction surfaces agree with the experimental data, and the calculation results for the subsonic conditions are more accurate than the one for the transonic conditions.