Title: Characterization of the Damping of a Free Vibrating Piezoelectric Motor Stator by Displacement Measurements

This report and addendum were issued separately, but are cataloged as unit. A meeting was held on April 17, 1958, at the Bettis Plant to review materials data for the slip-on statortype mechanism motor tubes. Results of this meeting are presented. )W.L.H.)

An experimental investigation of a free power turbine designed for a 112-kW, automotive, gas-turbine engine was made to determine the penalty in performance due to the stator-vane end clearances. Tests were made over a range of mean section stator-vane angles from 26/sup 0/ to 50/sup 0/ with the vane end clearances filled. These results are compared with test results of the same turbine with vane end clearances open. At design equivalent values of rotative speed and pressure ratio and at a vane angle of 35/sup 0/, the mass flow with the vane end clearances filled was about 8% lower thanmore » mass flow with vane end clearances open. This decrease in mass flow was mitigated by increasing the vane angle. This was as expected since vane loading and reaction decrease with increasing vane angle. With the vane end clearances filled, there was about a 66% reduction in mass flow when the vane angle was decreased from 40/sup 0/ to 26/sup 0/. For the same decrease in vane angle the stator throat area decreased by about 50%. This result indicates that the rotor losses were increasing with decreasing vane angle. At design equivalent values of speed and pressure ratio, there was a penalty of about 4 points in total efficiency due to the vane end clearances of 1.1 and 1.9% of the vane height for the hub and tip sections, respectively. This penalty remained about constant over the range of vane angles investigated. Significant increases in total efficiency were obtained for both stator-vane end configurations as the vane angle was increased from 26/sup 0/. A peak total efficiency of about 0.91 was obtained at the vane angle of 45/sup 0/ with the vane end clearances filled. Results of static-pressure measurements and rotor-exit surveys showed that the rotor reaction was positive from hub to shroud for the vane angle of 45/sup 0/. Although high negative rotor incidence angles were obtained, the high positive rotor reactions would be expected to minimize the effects of increased losses due to incidence.« less

The cold-air performance of the baseline power turbine designed for a 112-kW automotive gas-turbine engine was experimentally determined. Since this acial-flow power turbine has a variable stator for engine control and braking, performance data were taken at positive-power stator-vane-chord setting angles of 26/sup 0/, 30/sup 0/, 35/sup 0/ (design), 40/sup 0/, and 50/sup 0/ from the plane of ratation and at the nominal braking position of 107/sup 0/. The overall performance in terms of mass flow, torque, speed, and efficiency is presented. Overall diffuser performance and the results of rotor-exit radial surveys are also presented. Turbine efficiency varied significantly withmore » stator setting angle, increasing to a maximum as the setting angle increased. For equivalent design speed and a design work factor of 1.172, the maximum total efficiency was 0.87 at the 45/sup 0/ setting angle although the total efficiency at the design setting angle of 35/sup 0/ was 0.77. At equivalent design speed and a design static pressure ratio of 1.775, mass flow ranged from 48.5 to 133.5 percent of design and torque ranged from 33 to 142 percent of design as the stator was opened from the 26/sup 0/ to the 50/sup 0/ setting angle. The turbine braking power was determined at a nominal stator setting angle of 107/sup 0/. Turbine internal flow characteristics were determined from static-pressure measurements and rotor-exit radial surveys with probes. The rotor-hub reaction was negative for all conditions tested at stator setting angles below 40/sup 0/. Although the hub stage reaction was -0.160 at the 35/sup 0/ setting angle (design), it was 0.131 at the 45/sup 0/ setting angle (maximum efficiency). Overall diffuser total-pressure-loss coefficients that included both the diffuser and the exit collector were obtained over the range of diffuser-inlet critical velocity ratios tested. The loss coefficient varied from 0.2 to 0.4 as the inlet critical velocity ratio increased from 0.1 to 0.5.« less