RadSci Consultancy

The first reported neutron video imaging tests of an operating aero-engine (the Gem helicopter engine) were carried out on the cold neutron beam of the  DIDO 26MW Material Testing Reactor at AERE Harwell in 1975.

The two images shown of the oil scavenge system were obtained using high resolution film and Gd converter foil. In fig. 1, the static engine radiograph shows the oil level and the centre shaft half-filled . The area below the centre shaft and the oil is clear indicating that no oil was present. The density  of the oil in the return pipe was high indicating normal oil. A bubble is visible in the return pipe. Immediately after the engine was started (fig. 2 engine at ground idle speed), an oil mist fell from the bearing to the left of the centre shaft. A few seconds later, the centre pipe filled with oil and the jet of lubricating oil flowed  back into the sump on the right hand side, droplets are visible and are estimated to be ~ 0.5mm in diameter. Due to rotation of the gears, a depression can be seen on the surface of the oil in the sump caused by windage. The jet of oil should have been lubricating the gear train but windage was deflecting it.

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Reference: "Aero-engine Applications of Cold Neutron Fluoroscopy at Rolls-Royce Ltd" , PAE Stewart, Rolls-Royce Ltd, Bristol, U.K.
Editors: JP Barton and P Von der Hardt, Neutron Radiography Proceedings of the First World Conference, San Diego, California, U.S.A., Reidel Publishing Co., Holland, 1982.