Accession Number : AD0016564


Title :   ROTARY WING TIP-MOUNTED PULSE-JET ENGINE STRUCTURAL, NOISE REDUCTION, VALVE PHASING AND ELECTRICAL ANALOGY INVESTIGATIONS


Corporate Author : FAIRCHILD ENGINE AND AIRPLANE CORP COSTA MESA CA FAIRCHILD ELECTROTECHNICS DIV


Personal Author(s) : Stevens, G L ; Veneklasen, Paul S


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/016564.pdf


Report Date : 20 Feb 1953


Pagination or Media Count : 143


Abstract : Improvement of existing pulsejet engines resulted in engines having (1) a 425-fps design speed with a maximum over 500 fps, (2) a design-speed life exceeding 41 hr, (3) a 444-g design-acceleration loading with a maximum over 575 g, and (4) a specific thrust of 2.23. An analysis indicated that a 25% greater thrust is possible with a ducted engine at a 550-fps tip speed. Acoustic coupling of 2 engines with proximate tailpipes reduced the fundamental-frequency noise level. Exhaust-shroud design requirements were established for shrouds which enhance acoustic coupling and which do not adversely affect static performance. Opposed-engine configurations further reduced the noise level and favorably affected performance. The inlet noise level was not reduced by acoustically coupling /4 ducts. A capacitance-type pressure pickup with a 1.25- mc carrier frequency and a 50-psi maximum was used with a high-impedance probe to determine engine-pressure variations. Average inlet-valve operating temperatures of 145 deg F may permit the use of strain gages as inlet-valve position indicators. Inlet-valve natural frequency and damping characteristics could not be determined with commercial vibration equipment. Studies of electrical analogies for engine analysis provided (1) a basic circuit demonstrating the analogous behavior of electrical circuits and pulsejet engines, (2) a relaxation oscillator providing repetitive analogy operations and simulating combustion, (3) an artificial electrical line simulating acoustic resonant characteristics, and (4) a determination of engine-tube resonant modes.


Descriptors :   *JET HELICOPTER ROTORS , *PULSEJET ENGINES , PERFORMANCE(ENGINEERING) , DAMPING , COMBUSTION , RESONANCE , DUCTS , STRAIN GAGES , LEVEL(QUANTITY) , ACOUSTICS , NOISE REDUCTION , INLETS , STATIC TESTS , ACOUSTIC PROPERTIES , ANALOGIES , EXHAUST PIPES , JET ENGINE NOISE , RELAXATION OSCILLATORS , COUPLING(INTERACTION) , VIBRATION


Subject Categories : Noise Pollution and Control
      Helicopters
      Jet and Gas Turbine Engines


Distribution Statement : APPROVED FOR PUBLIC RELEASE