An extensive experimental investigation was made to determine the effect of varying the rotor tip clearance of a 12.77-cm-tip diameter, single-stage, axial-flow reaction turbine. In this investigation, the rotor tip clearance was obtained by use of a recess in the casing above the rotor blades and also by use of a reduced blade height. For the recessed casing configuration, the optimum rotor blade height was found to be the one where the rotor tip diameter was equal to the stator tip diameter. The tip clearance loss associated with this optimum recessed casing configuration was less than that for the reduced blade height configuration.
principal 'results indicated that the performance level was substantially higher than that assumed in the design. As part of the program to reduce . manufacturing costs, the first stage blading was reduced in thickness for ease in coining. Tests of the modified blades indicated that the aerodynamic o ITI .
The high efficiencies of small radial turbines have led to their application in space power systems and numerous APU and shaft power engines. Experimental and analytical work associated with these systems has included examination of blade shroud clearance, blade loading, and exit diffuser design. Results indicate high efficiency over a wide range of specific speed and also insensitivity to clearance and blade loading in the radial part of the rotor. The exit diffuser investigation indicated that a conventional conical outer wall may not provide the velocity variation consistent with minimum overall diffuser loss. A list of recently published NASA radial turbine reports is included.
1 The limited time allotted for the preparation of the written discussion prevented me from obtaining reference material dealing with the subject problem. Hence, I cannot adequately compare the authors' approach with others that have been developed.2 The use of the dynamometer for power measurement and the location of the flow measuring device upstream of the rotary valve demonstrated a good research approach in obtaining valid measurements of the two turbine parameters.3 The paper essentially presents a check on the old quasisteady flow assumption using an "equivalent amplitude" approach instead of a "pulse frequency" approach. The authors do not present a real comparison of their approach with that obtained by other investigators. The conclusions should make a stronger statement with regard to the approach developed by the authors. The major conclusion should be stated that the quasi-steady flow analysis is still not satisfactory in view of the large errors that approach 40 percent.4 The relevance of the exhaust pipe studies is not clearly stated with regard to the quasi-steady flow assumption with respect to the equivalent amplitude approach.The authors have presented very interesting results on the comparison between the predicted quasi-steady flow and the measured nonsteady performance of a radial turbine. The nonsteady flow performance of a turbine depends on the mean pressure and temperature levels at entry, and the shape, amplitude, and frequency of the pressure pulses. The concept of an equivalent amplitude (A7r*Ar) is very useful as it can take into account the amplitude of the pressure ratio variations and the pulse shape. However, the comparison between the performance of the turbine evaluated on the basis of the quasi-steady flow assumption and that measured directly under the nonsteady flow conditions is not as good as might be expected. A major cause of the discrepancies is probably the rotary valve which the authors used to generate the desired pressure pulses.The pulsating flow can be of two types: (i) nonsteady continuous flow; and (ii) nonsteady discontinuous flow. Usually the ports of the rotary valve housing can be designed to achieve the desired shape of the pressure pulses, but the flow would be discontinuous because of its geometry. From the sketch, it can be seen that the valve would remain closed for 180 -(8 +
This paper presents the results of an analytical study of turbomachinery requirements and configurations for Brayton-cycle space-power systems. Basic turbomachinery requirements are defined and typical effects of such system design parameters as power, temperature, pressure and working fluid on turbomachinery geometry and performance are explored. Typical turbomachinery configurations are then presented for systems with power outputs of 10, 100 and 1000 kw.
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