Exploring Topology Optimisation of High Pressure Turbine Blade Tips

This work presents the aerodynamic topology optimisation of high pressure turbine rotor blade tips. Before carrying out the topology optimisation on the blade tip, some initial tip design studies were carried out. The winglet shape was optimised using two different design space setups and parameter limits. The optimum winglet design features the largest overhangs and in the case of unconstrained optimisation proved to have 1.40% greater aerodynamic efficiency. Secondly, a radial basis function based parametrisation was set up to allow the creation of single squealer line using the flat tip blade as a baseline geometry. The optimum case proved to increase efficiency 0.46% compared to the flat tip. After that, a combination of winglet and topology free squealer tips was investigated for topology optimisation. The winglet tip was parametrized as in the winglet only optimisation cases and topology free squealer walls were created using mapping of radial basis function surfaces of different complexities. It is shown that by combining both winglet and novel squealer topology optimisation, better designs of different topologies can be produced.

Single-Coil Eddy Current Sensors and Their Application for Monitoring the Dangerous States of Gas-Turbine Engines

The creation and exploitation of gas turbine engines (GTE) often involve two mutually exclusive tasks related to ensuring the highest reliability while achieving a good economic and environmental performance of the power plant. The value of the radial clearance between the blade tips of the compressor or turbine and the stator is a parameter that has a significant impact on the efficiency and safety of the GTE. However, the radial displacements that form tip clearances are only one of the components of the displacements made by GTE elements due to the action of power loads and thermal deformations during engines’ operation. The impact of loads in conjunction with natural aging is also the reason for the wear of the GTE’s structural elements (for example, bearing assemblies) and the loss of their mechanical strength. The article provides an overview of the methods and tools for monitoring the dangerous states of the GTE (blade tips clearances, impellers and shafts displacements, debris detecting in lubrication system) based on the single-coil eddy current sensor, which remains operational at the temperatures above 1200 °C. The examples of practical application of the systems with such sensors in bench tests of the GTE are given.

Controlling Leakage Flows Over a Rotor Blade Tip Using Air-Curtain Injection: Part I — Aero-Thermal Performance of Rotor Tips

The rotor casing of gas turbine engines is generally cooled with cooling air from compressors and then the cooling air is discharged into the passage flow of the rotor. In this paper, a novel design both for the blade tip leakage flow control and for the rotor casing and tip cooling is proposed. Cooling air is injected through a pair of inclined rows of discrete holes positioned between 30% and 50% axial chord downstream of the blade leading edge in the casing. The casing injection forms as air-curtain within the blade tip gap, and inhibits the development of the tip leakage flows and provides secondary-order cooling for the rotor tip. Air injection from the rotor casing onto flat and recessed blade tips is investigated using numerical simulations that is validated by extensive aerodynamic and heat transfer experimental data. Flow and film cooling over the blade tip and turbine overall aerodynamic performance are examined in detail for two casing injection rates. Comparisons between flat tip without casing injection (baseline) case and the casing injection cases show that the air-curtain injection significantly alters the flow structures near the casing by modifying the development and migration of the tip leakage flow. The air-curtain injection over the flat and recessed tips both generates turbine stage overall aerodynamic efficiency improvement due to the sealing effects of the casing injection, but the efficiency gain depends on the competing results between the sealing effects and the “over-blown” effects of the air-curtain injection. Applying a recess to the blade tip is generally detrimental to the efficiency improvement by the air-curtain injection. In addition to efficiency improvement, secondary-order cooling effects from the casing injection are found to provide considerable thermal protection for the blade tips. However, increasing injection rate reduces the film cooling performance over the rotor tip surfaces. The recessed tip could present better film cooling effectiveness than the flat tip in the presence of the air-curtain.

BTT & RFLB - THE OPTIMUM SET FOR STEAM TURBINE BLADES MONITORING

BTT, Blade Tip Timing system, is a commercially available system generating files of precise times of blade tips when passing sensors attached in a machine stator. RFLB, Residual Fatigue Life of Blades, is a postprocessor of those files evaluating estimates of fatigue lives of all blades fitted to the wheel. The set reduces a danger of unexpected blade failures.

An Experimental Study of Using Vortex Generators As Tip Leakage Flow Interrupters in an Axial Flow Turbine Stage

The flow leaking through the gap between rotor blade tips and casing surface in a turbine stage is an important source of energy loss. The current study uses a new concept named as Tip Leakage Interrupters (TLI) to mitigate some of the adverse effects of the tip leakage flows and improve the efficiency of an axial turbine stage. The TLIs are a system of vortex generators attached onto the suction side of the turbine blade tip. The TLI design was developed in a proof of concept effort and they operate by inducing controlled vortical structures originating from strategically shaped/oriented multiple and sub-miniature vortex generators. These induced vortical structures, when properly interact with the tip leakage vortex reduce the damaging aerodynamic effects of the leakage flow. The TLIs in this investigation were mounted near the suction side corner of turbine blade tips rotating in a single-stage cold-flow turbine facility. In this investigation, three different parameters such as the mounting location of TLI on the airfoil tip region, the number of TLIs mounted and the specific orientation of TLI were varied. The TLI mounted near the minimum pressure point on the suction side of the blade generated the largest vortical structure that is counter rotating to the leakage vortex system and hence had the greatest effect in reducing the strength of the leakage vortex. Adding more TLIs on the blade suction surface was found to improve the tip leakage mitigation effort. The study showed that changing the specific orientation of the TLI with respect to the incoming flow drastically changes the rotational direction of the vortex it generates and its nature of interaction with the leakage vortex.