High resolution gamma ray tomography of a rotating hydrodynamic coupling

Hydrodynamic couplings are being used for torque transfer in heavy duty systems, such as naval vessels, power plants, locomotives or other transport vehicles. A hydrodynamic coupling essentially consists of two rotating bladed wheels, the pump and the turbine wheel, which are placed inside a metal enclosure. In operation the coupling is partially filled with a fluid and this fluid realises the momentum transfer from the driving side (pump) to the load side (turbine). The flow conditions in the coupling determine its operational behaviour. A known problem of such devices is the sudden change of slip during a continuous increase or decrease of either load or angular velocity of the pump. To investigate the behaviour of a hydrodynamic coupling the flow structure inside the coupling must be disclosed. But there only few measurement techniques which are applicable. Thus, the flow inside the pump is a heavily turbulent two-phase flow that is hardly accessible to optical or other measurement techniques. Gamma ray tomography provides a convenient method to measure the time integrated phase distribution within such a coupling. We performed such measurements in the past with the help of a low resolution gamma ray tomography system. Now we continued to use a high resolution gamma ray tomograph for that purpose. The measurements were carried out using a Cs-137 isotopic source and a detector arc with 2 mm spatial resolution. The test coupling mostly consists of aluminium and has an outer diameter of approximately 500 mm. For the measurement we employed the angle resolved data acquisition scheme that allows us to image rotating distributions with a fixed tomography setup. In the paper we will discuss the application of gamma ray tomography to this particular industrial problem.