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Scientists at the von Karman Institute in Belgium have contracted Layerwise to produce a scaled turbine inlet guide vane model for a turbine research project.

Layerwise built the metal vane specimen as a single part, complete with internal cooling cavity and fine instrumentation channels.

Research based on detailed simulation and testing concludes that turbine cooling could be improved by ejecting a pulsating stream through the trailing edge, instead of a continuous stream.

At the same time, the pulsed cooling significantly reduces the intensity of the shock waves.

This opens up opportunities for jet engine and power-plant turbine manufacturers to achieve higher turbine expansions, resulting in more compact engines and reduced development costs.

Turbine blades in jet engines and power plants are internally cooled because of their exposition to high-temperature gas flow, directly discharged from the combustion chamber.

Shock waves formed at the trailing vane edge generate strong stator/rotor interactions that reduce turbine efficiency and add additional mechanical challenges.

The current research at the von Karman Institute focuses on pulsated cooling versus continuous cooling.

Scientists selected and characterised the different building blocks needed to acquire detailed insight into this new concept of pulsated turbine cooling.

A mechanical pulsating valve delivering an adequate margin of frequencies and amplitudes generate the pulsating cooling air.

The air flow travels through a model of a high-pressure inlet guide vane produced by Layerwise, circulating all along its length before being ejected through a slot at the trailing edge.

It concerns a simplified and scaled turbine inlet guide vane model that is derived from a real geometry.

Prof Paniagua and his team studied numerically the entire setup using fluid-dynamics simulation software.

The complete experimental setup was modelled, including piping, pulsating valve and blade cavity.

The fluid-dynamics model was used to extend the experimental investigation beyond the limits of the current setup, mainly in the upper frequency provided by the valve.

Subsequently, experiments were carried out to verify the numerical results.

Layerwise, a company focusing on selective laser melting (SLM), produced the vane according to the von Karman Institute’s specifications.

Layerwise manufactured the vane as one unit in a single production step, including all internal cooling cavities and instrumentation channels.

The heavily instrumented vane is designed to allow high density in the measurements.

The pressure sensors include both pressure tabs and kulite’s unsteady pressure sensors.

During the wind-tunnel tests, the sensors in the vane as well as in the upper and lower wind-tunnel flow channels collected all the experimental data.

The coolant vane air flow is generated using a rotating valve operating with a perforated rotating disc, delivering a pulsated high-pressure air flow up to 200Hz.

Wind-tunnel test results, including time-averaged and time-resolved results, helped the aerodynamicists to understand and prove the complex physics involved.

Computed fluid dynamics simulation predicts a 70 per cent reduction in shock intensity, with experimental data conforming the heavy reduction tendency.

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