The aerodynamic characteristics of a variable area nozzleless volute (VAV) for small radial inflow turbines are studied with the aid of cold air tests in which flow parameters inside the volute channel and at the outlet of the nozzleless ring are measured for cases of various cross-sectional areas. The experimental investigation shows that the desired aerodynamic parameters, especially the outlet flow angle α1 as well as the mass flow rate range can be obtained by varying the croes-sectional area of the VAV. A reasonable approximate method for calculating the average outlet flow angle α1 is presented in which the variation of the circulation in the flow is taken into account.

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