Stator Blade Surface Research Articles

Experimental Investigation of Steady and Unsteady Flow Field Downstream of an Automotive Torque Converter Turbine and Inside the Stator: Part II—Unsteady Pressure on the Stator Blade Surface

The stator flow field of an automotive torque converter is highly unsteady due to potential and viscous interactions with upstream and downstream rotors. The objective of this investigation is to understand the influence of potential and viscous interactions of the upstream rotor on the stator surface pressure field with a view toward improvement of the stator design. Five miniature fast-response pressure transducers were embedded on the stator blade. The measurements were conducted at three locations near the leading edge and two locations near the trailing edge at the midspan location. The upstream flow field was measured using a fast response five-hole probe and is described in Part I of this paper. The experimental data were processed in the frequency domain by spectrum analysis and in the temporal-spatial domain by the ensemble-averaging technique. The flow properties were resolved into mean, periodic, aperiodic, and unresolved components. The unsteady amplitudes agreed well with the pressure envelope predicted by panel methods. The aperiodic component was found to be significant due to the rotor–rotor and rotor–stator interactions observed in multistage, multispool environment.

Rotor-wake influence on axial-compressor-stator boundary layers

The boundary-layer development on blades in an axial-flow compressor is an important design consideration. The influence of upstream-blade wake segments on downstream-blade boundary layers is not yet satisfactorily modeled for design purposes. To clarify the effects of wake segments on boundary layers, we used surface hot-film gages to sense the influence of rotor-wake segments on stator-surfac e boundary layers at midspan in a low-speed, axial-flow compressor stage. It was clear that rotor-wake segments moved along the stator-blade pressure and suction surfaces much like a turbulent spot would; the region of influence of each wake segment became larger further downstream. Boundary-layer transition was not expected on the low-speed, stator-blade surface until about midchord. Nevertheless, the laminar boundary-layer flow on the forward portion of the stator blade appeared to be turbulent when a rotor-wake segment was present. This periodic alternating of the stator boundary-layer flow was observed further aft on the blade also.

A Note on Blade Wake Interaction Influence on Compressor Stator Row Aerodynamic Performance

Attention is given to the effect of blade wake interactions on the performance of an axial flow compressor's stator row, for the case of compressor and fan stator flows without shocks. The measured midspan loss of total pressure can be related to stator surface boundary layers, the chopped rotor wakes passing through the stator row, and the interaction between these flows. The interaction between rotor blade wake segments and stator blade surface boundary layers generates much higher losses than expected in both the stator wake and in the region of flow between stator boundary layers/wakes, if interaction effects are ignored.

The Influence of Blade Number Ratio and Blade Row Spacing on Axial-Flow Compressor Stator Blade Dynamic Load and Stage Sound Pressure Level

In axial-flow turbomachines considerable dynamic blade loads and noise production occur as a result of the unsteady blade row interaction between rotor and stator blades. This paper presents results of midspan measurements of the dynamic pressure distribution on the stator blade surface (fixed number of blades) for various rotor-blade numbers and various axial clearances between rotor and stator. For this purpose, one stator blade had been provided with eleven semiconductor pressure transducers in the midspan section. Simultaneously, the sound pressure level was measured at two axial distances downstream of the stator by four condensator microphones distributed along the circumference in each of the two sections and mounted flush with the wall surface. The wake-flow distribution downstream of the rotor could be obtained by a rotating three-hole pressure probe. The results of the corresponding dynamic pressure-measurements and noise measurements are discussed and compared with results from theory.