An experimental investigation of a hydrogen oxygen flame steam generator
Supercritical steam is used in a wide range of applications such as stationary power generation, locomotive and space propulsion, and chemical processing including coal and biomass gasification. Subject to availability of hydrogen and oxygen, steam generation using direct H2-O2 combustion offers advantages such as zero pollutant emissions, high thermodynamic efficiency and high specific thermal power output. Direct but staged addition of high pressure liquid water to the combustor allows a broad range of process temperatures. This thesis describes a design and an experimental study of a 40 kW steam generator adapted from the aerospace field for application to coal and biomass gasification. The experimental steam generator includes a spark augmented torch igniter and a near stoichiometric H2-O2 combustion chamber capable of operating at design pressure of 1.5 MPa and a maximum flame zone design temperature of 3450 K. Additional steam is generated by direct injection of liquid water into the post-combustion zone to achieve gasification process temperatures in the 1100-1400 K range. The successful design of the present steam generator includes appropriate igniter location and timing and staging and mixing of the H2, O2, and H2O streams. Experimental results of the steam generator are presented at varying equivalence ratios and compared with equilibrium calculations. The characteristic frequencies and magnitudes of unsteadiness are quantified using power spectral density functions of measured pressure fluctuations at select location throughout the steam generator. The development of the design of the steam generator is also tracked through to its present form. Integration of the steam generator to an optically accessible entrained flow coal and biomass gasifier is discussed. Recommendations for future work including computational verification of experimental results and design improvements are discussed.
Gore, Purdue University.
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