Stiffening Heat-Exchanger Tubes Against Vibrations
Midsection clamps reduce harmful effects of crossflow. Clamp bolts onto four tubes, increasing stiffness and natural frequency. Unstable vibrations suppressed.
Rao, G. V. R.↗
Engineering topics
Rao, G. V. R.
Publications and source records attributed to Rao, G. V. R..
Experimental evaluation of an advanced Space Shuttle main engine hot-gas manifold design concept
This study, using an extensively modified, full-scale space shuttle main engine (SSME) hot-gas manifold (HGM), established a detailed aerodynamic data base to support development of an advanced, three-dimensional, fluid-dynamic analysis computer model. In addition, the advanced SSME hot-gas manifold design used in this study demonstrated improved flow environment (uniformity) in the fuel side turbine exit and transfer duct exit regions. Major modifications were incorporated in the full-scale HGM flow test article model using two large transfer ducts on the fuel turbine side of the HGM in place of the three small transfer ducts in the present design. Other model features included an increases in the flow areas downstream of the 180-degree turn and in the fishbowl regions.
Pelaccio, D. G.↗
Experimental evaluation of an advanced Space Shuttle Main Engine hot-gas manifold design concept
The Space Shuttle Main Engine's hot gas manifold (HGM) has been the subject of an experimental study aimed at the establishment of an aerodynamic data base to support the development of an advanced, three-dimensional, fluid dynamic analysis computer model. The advanced HGM design used in the study demonstrated improved flow uniformity in the fuel-side turbine exit and transfer duct exit regions. Major modifications were incorporated in the HGM flow test article model, using two large transfer ducts on the fuel turbine side in place of the three small transfer ducts of the present design. The HGM flow field data were found to be essentially independent of Reynolds number over the range examined.
Pelaccio, D. G.↗
Nozzle Modification Suppresses Flow Transients
Proposal for steadying flow from rocket nozzle on Space Shuttle main engine could be applied to other large-area-ratio contoured nozzles. Oscillations and pulsations in boundary-layer flow would be reduced by flaring nozzle exit. Transient side loads on nozzle would be suppressed. Large pressure gradients and eddies that can lead to fluctuations are suppressed. Exact radius of curvature of corner would depend on shear-layer thickness.
Rao, G. V. R.↗
Use of leaning vanes in a two stage fan
The use of leaning vanes for tone noise reduction was examined in terms of their application in a typical two-stage high pressure ratio fan. In particular for stages designed with outlet guide vanes and zero swirl between stages, leaning the vanes of the first stage stator was studied, since increasing the number of vanes and the gap between stages do not provide the desired advantage. It was shown that noise reduction at higher harmonics of blade passing frequency can be obtained by leaning the vanes.
Rao, G. V. R.↗
Theoretical studies of tone noise from a fan rotor
An analytical study was made of some possible rotor alone noise sources of dipole, quadrapole and monopole characters which generate discrete tone noise. Particular emphasis is given to the tone noise caused by fan inlet flow distortion and turbulence. Analytical models are developed to allow prediction of absolute levels. Experimental data measured on a small scale fan is presented which indicates inlet turbulence interaction with a fan rotor can be a source of tone noise. Predicted and measured tone noise for the small scale rotor are shown to be in reasonable agreement.
Rao, G. V. R.↗
Analytical Lift Fan Noise Study
Based on reasonable estimates of flow conditions occurring in an axial fan, acoustic radiation from various noise sources is evaluated. Results of computations on two specific fans are presented, and relative significance of the various sources is examined.
Rao, G. V. R.↗
Rotor noise due to inflow turbulence.
The interaction of turbulent velocity fluctuations of the inflow with rotor blades and the resulting acoustic radiation is examined in terms of: dipole sources due to blade loading, monopole sources due to thickness of the rotating blades, and quadrupole sources due to velocity fluctuations in the flow region. Depending upon the length and time scales of the turbulence, sufficient number of blades may interact with a coherent eddy to radiate noise with discrete peaks at blade passing frequency and its harmonics. Theoretical estimates of acoustic radiation to on-axis points from a typical subsonic rotor are presented, and it is noted that the discrete tone noise is primarily from dipole radiation. Discrete tone noise levels observed in narrow band analysis of test data show reasonable agreement with analytical predictions.
Rao, G. V. R.↗
Use of leaning vanes for fan noise reduction.
The obliquity of blade-vane interactions in an axial fan and its influence on noise generation are examined. Analysis indicates that leaning vanes decrease the amplitudes of the fluctuating pressures at the rotor-stator plane and modify the radial distribution. These changes lead to considerable cancellation in the near field and consequent reduction in radiated acoustic power. Acoustic measurements on a small scale fan with radial and leaning vanes compare favorably with analytical predictions.
Rao, G. V. R.↗
Computer programs for determination of transonic flow parameters in a convergent-divergent nozzle
Programs based on equations that include functions for boundary values along nozzle axis yield different types of flow field configurations. Program's documentation details method of calculating subsonic flow field and sonic line, and describes modified method of characteristics for calculating supersonic flow downstream of sonic line.
Jaffe, B.↗