Abrasive flow machining process for a meridionally divided turbine housing, and a masking fixture used in said process

An assembly comprising:

• a turbine housing comprising an inlet pipe partitioned by a center wall into a first inlet conduit and a second inlet conduit for conducting two separate fluid streams into the turbine housing, a volute connected to the inlet and extending from the inlet pipe circumferentially about a center axis of the turbine housing, an annular nozzle passage connected to the volute and extending radially inwardly therefrom with respect to the center axis, and an axial bore connected to the nozzle passage and extending axially to a discharge opening, the turbine housing further comprising a divider disposed within the volute so as to divide the volute into a first scroll and a second scroll, the first scroll being connected to the first inlet conduit and the second scroll being connected to the second inlet conduit, the turbine housing further comprising a tongue;
• and
• a fixture mounted within the axial bore of the turbine housing, the fixture comprising:
• a tubular side wall and an end wall joined to one end thereof to form a cup comprising a closed end and an open end;
• wherein the tubular side wall defines a first slot and a second slot each extending from a radially outer surface to a radially inner surface of the tubular side wall, the first and second slots being proximate the end wall and being axially spaced apart, the first and second slots being circumferentially coextensive and extending circumferentially over an angular sector occupying between 300° and 330° of a circumference of the tubular side wall such that there remains a slot-free blocking area occupying between 30° and 60° of the circumference;
• wherein the fixture is axially oriented such that the first and second slots are aligned with the nozzle passage, and is circumferentially oriented such that one circumferential side of the blocking area is circumferentially adjacent the tongue.