High-Fidelity Computational Fluid Dynamics Analysis of In-Serviced Shrouded High-Pressure Turbine Rotor Blades

Abstract

In_service deterioration can lead to undesired shape variations on high-pressure turbine rotor blades. This can have a significant impact on efficiency, power generation and component life. Loss of power production from the high_pressure turbine rotor causes engine over_throttling to compensate for the lower performance. This will in turn worsen the operating conditions and ultimately reduce the life of the component. The aim of this study is to provide a high_fidelity flow simulation of in_serviced shrouded High_Pressure Turbine (HPT) blades of a modern Jet Engine. Shape variations effects on the aerodynamic performance of several shrouded HPT blades with different number of in_service hours have been investigated. In order to establish a digital model of the shape variation, a novel reverse engineering procedure is carried out, to come up with a parametrized definition of each blade's variations from nominal including any observable damage. The investigation is conducted by means of an in_house, full 3D steady_state RANS simulation of the flow around a series of damaged rotor blade geometries, which are obtained through high_resolution GOM scans. The analysis shows that the aerodynamic performance of the HPT rotor blades under investigation is primarily sensitive to shroud damage, which is found to account for efficiency losses often greater than 3%, and for more than 80% of the total performance loss. A secondary role on efficiency is found to be played by the blade shape deviation. A highly linear correlation is found between HPT stage efficiency and a combination of shroud damage parameters.

Heat Transfer Analysis of Damaged Shrouded High-Pressure Turbine Rotor Blades

“…the inter-platform shroud gap, which is severely detrimental to aerodynamic performance. A more detailed description of this loss mechanism can be found in [9]. The trailing edge elongation, R3, and rear fin tip gap are also associated with a relatively high impact on efficiency for this set of blades.…”

“…This creates a large amount of leakage through the inter-platform shroud gap, which is severely detrimental to aerodynamic performance. A more detailed description of this loss mechanism can be found in [9]. the inter-platform shroud gap, which is severely detrimental to aerodynamic performance.…”

“…The relative orientation of the shroud fins in Figure 2B also indicates that the typical scan displays a twist of the platform with respect to the design intent geometry. This counter-clockwise twist was, in part, responsible for the increase in shroud gap, as discussed in a previous study [9]. To quantify this, a parameter called the "shroud angle" was measured on all the blades as the angle formed by the shroud gap mean line with the axial direction.…”

“…The complete multi-row CFD domain mesh has an average of approximately 40 million elements. A verification study for this modelling technique was carried out previously [9], and as such is omitted here.…”

“…This three-point non-linear fitting process requires three CFD simulations of the flow around the same blade geometry, with prescribed wall temperatures. Previous work [9] has focused on studying the correlation between aerodynamic efficiency loss and parametrized geometric deviation, and understanding the main loss mechanisms that characterize the flow field around in-service HP turbine blades. The objective of this analysis was to determine whether in-service deterioration, by virtue of inducing a modification in the geometry of the blades and the flow conditions, can cause an increase in the heat transfer coefficient in critical areas such as the blade shroud, leading the blades to experience a consequential acceleration of their degradation process.…”