ACOUSTICAL CHARACTERISTICS OF THE AIRESEARCH MODEL GTP331-30 GAS TURBINE ENGINE AND DEVELOPMENT OF HIGH-TEMPERATURE VIBRATION-DAMPING COATINGS FOR NOISE CONTROL
Abstract
Acoustical power level spectra and directivity indices in one-third octave bands were measured by the free-field method, with use of both a straight exhaust duct and a right-angle duct. One-third octave acoustic power level spectra were obtained for the cooling fan, accessory case, compressor inlet, and turbine plenum by use of the reverberant-room method. Tape recordings of each noise source were subjected to narrow-band analyses and local peaks correlated with engine processes. Three types of coatings were tested: vitreous enamels; high-manganese alloys; and aluminum-alumina cermets. All of the vitreous enamels, when applied in thin coatings, exhibited very good damping ability within their usable temperature range. The least efficient enamel had far more damping at high temperatures than the best low-temperature material at its optimum. This includes the enamels commonly used for corrosion resistance at elevated temperatures. Some of the high-manganese alloys and aluminum-alumina cermets produced a significant but lesser amount of damping. The nonlinear hysteresis loops generated at high stress levels were studied in attempts to learn the micromechanisms of fatigue failure.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 03, 1966
- Accession Number
- AD0482069
Entities
People
- D. Morrow
- L. S. Wirt
- R. W. Passage