Fuel decomposition and boundary-layer combustion processes of hybrid rocket motors

Martin J. Chiaverini, George C. Harting, Yeu Cherng Lu, Kenneth K. Kuo, Nadir Serin, David K. Johnson

    Research output: Contribution to conferencePaperpeer-review

    22 Scopus citations


    Using a high-pressure, two-dimensional hybrid motor, an experimental investigation was conducted on fundamental processes involved in hybrid rocket combustion. HTPB (Hydroxyl-terminated Polybutadiene) fuel cross-linked with diisocyanate was burned with GOX under various operating conditions. Large-amplitude pressure oscillations were encountered in earlier test runs. After identifying the source of instability and decoupling the GOX feed-line system and combustion chamber, the pressure oscillations were drastically reduced from ±20% of the localized mean pressure to an acceptable range of ±1.5%. Embedded fine-wire thermocouples indicated that the surface temperature of the burning fuel was around 1000 K depending upon axial locations and operating conditions. Also, except near the leading-edge region, the subsurface thermal wave profiles in the upstream locations are thicker than those in the downstream locations since the solid-fuel regression rate, in general, increases with distance along the fuel slab. The recovered solid fuel slabs in the laminar portion of the boundary layer exhibited smooth surfaces, indicating the existence of a liquid melt layer on the burning fuel surface in the upstream region. After the transition section, which displayed distinct transverse striations, the surface roughness pattern became quite random and very pronounced in the downstream turbulent boundaiy-layer region. Both real-time X-ray radiography and ultrasonic pulse-echo techniques were used to determine the instantaneous web thickness burned and instantaneous solid-fuel regression rates over certain portions of the fuel slabs. Globally averaged and axially dependent but time-averaged regression rates were also obtained and presented.

    Original languageEnglish (US)
    StatePublished - 1995
    Event31st Joint Propulsion Conference and Exhibit, 1995 - San Diego, United States
    Duration: Jul 10 1995Jul 12 1995


    Other31st Joint Propulsion Conference and Exhibit, 1995
    Country/TerritoryUnited States
    CitySan Diego

    All Science Journal Classification (ASJC) codes

    • Energy Engineering and Power Technology
    • Electrical and Electronic Engineering
    • Mechanical Engineering
    • Control and Systems Engineering
    • Aerospace Engineering


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