Services

Energy Technology Centre is working with a range of stakeholders on a number of research, development and testing projects to:

• Develop advanced modelling techniques for rain erosion

• Undertake feasibility studies into new erosion measurement methods for the laboratory environment

• Develop erosion sensor technology

• Appraise erosion test techniques

• Assess LEE protection products

Test Facility

The whirling arm rain erosion test rig was developed in-house to deliver industry-leading accuracy, control and repeatability in the test environment.

The ETC rain erosion test facility has recently been upgraded to improve its operating envelope and is now capable of striking test samples with water droplets at up to 150 m/s with water droplets between 1.8 mm and 2.5 mm in diameter, in controllable increments of 0.1 mm.

The test rig is highly characterised with data for droplet sizing, droplet rates, strike rates and strike locations on the test sample, making the test rig ideally suited to cutting-edge research where high levels of control and repeatability are essential.

Challenge

Assessing the materials under test currently involves stopping at discrete time intervals for visual inspection and making mass loss measurements. While these methods are current state-of-the-art, they have several limitations:

• The erosion test has to be stopped at discrete time intervals to remove the sample, weigh it and photograph it

• Stopping the tests at discrete time intervals offers poor resolution of the rate of erosion, especially if the rate is non-linear

• The method is very time consuming and labour intensive

• The visual inspection only provides a qualitative assessment of the erosion and it is difficult to assign a quantitative value by this method

• The measurement of change in mass only provides an overall assessment of the erosion but erosion can be highly concentrated in one area or spread across the sample

ETC wanted to improve its testing beyond the current state-of-the-art, by developing a system that could monitor erosion throughout testing, and make assessments based on more reliable indicators. This was no small challenge, since it required detecting micrometre level changes in blades moving at up to 150 m/s.

Solution

NPL saw potential in a technique it had developed for evaluating high temperature particle erosion monitoring in power stations. This used optical measurement methods to measure material loss by volume as the material was being bombarded by particles.

NPL made small modifications to the measurement technique to adapt it to wind turbine blade measurements. This was combined with a high speed camera, and software was created to interrogate the vast amounts of data generated by the camera images.

The instrument was tested in ETC’s rig using blade sections with well understood introduced defects. The technology was shown to measure the known defects correctly, down to a few micrometres. This successfully demonstrated the possibility of making measurements of the size and shape of damage caused by erosion during testing.

The initial feasibility study proved the concept, but more work is needed to adapt measurements for the range of turbine blade surface shapes and finishes. ETC is now looking for partners and funders to take this project forward.