An inlet housing for a partial-admission turbine has been designed to cause the inlet airflow to make a smooth transition from an open circular inlet to an inlet slot. The smooth flow is required for purposes of measuring inlet flow characteristics and maximizing the efficiency of the turbine.

A partial-admission turbine is a turbine in which the inlet slot occupies less than a complete circle around the rotor axis. In this case, the inlet slot occupies a 90° arc. The present special inlet-housing design is needed because the "bull nose" shape of a conventional turbine inlet housing fails to provide the required smooth transition in a partial-admission configuration and thereby gives rise to a loss of turbine efficiency and inaccuracies in inlet flow measurements.

Upon entering the inlet housing through the circular opening, the flow encounters a "tongue"-shaped passageway, which serves as a ramp that diverts the flow to the first of two straight passages. This first passageway occupies a 90° arc and has a length equal to two passage heights. Instrumentation rakes for measuring the characteristics of the inlet flow are installed in this passageway.

Just past the first straight passageway is the second one, which is narrower and leads to the 90° turbine inlet slot. This passageway is used to smooth the flow immediately prior to its passage through the turbine inlet slot. The length of this second passageway equals the length of the chord of a turbine vane.

The inlet housing incorporates small ports for measuring static pressures at various locations of the flow, and incorporates bosses for the installation of the instrumentation rakes. The inlet housing also includes a flange at its inlet end for attachment to a circular inlet duct and a flange at its outlet end for attachment to the outer casing of the turbine.

This work was done by Ralph Moye, William Myers, and Kevin Baker of Marshall Space Flight Center. MFS-31971.

NASA Tech Briefs Magazine

This article first appeared in the July, 2004 issue of NASA Tech Briefs Magazine.

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