A large selection of one- and two-dimensional methods can be used to calculate the scroll geometries. This paper examines the consequences of different scroll geometry parameters under various flow configurations, including the influence of components in the scroll flow field.
A combination of arrangements of the various components was investigated, (scroll/nozzle/rotor, scroll/nozzle/stator, scroll/vane support/rotor, scroll/vane support/stator), to see how the flow varied. In this particular case a frictionless scroll was designed. The turbine operates with a gas fluid. Using a non-invasive laser two-focus technique and wall pressure drillings the flow field was measured over three scroll cross sections and over its extent at φ = 186° up to φ = 211°. The theoretical analysis was performed on a computer using a commercial 3D finite element programme. Using the programme enables the theoretical flow fields of various scroll geometries to be calculated. The validity of the calculations can be assessed by comparing the theoretical calculations with the above mentioned measurements.
The measurements show that by using a rotor the flow field inside the scroll remains uninfluenced by the vane support and nozzle. Measurable differences appear when the rotor is replaced by a stator, these results are confirmed by the computer program. The calculations also show that the scroll geometry has an important effect on the development of the flow field.