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SCO2 Oxy-Combustion Working Group

SCO2 Oxy-Combustion Working Group
Meeting Minutes
July 9, 2019



  • Dr. Matthias Ihme – Stanford University
  • Title: “Thermostructural Analysis and Numerical Modeling for Scalar Mixing and Combustion at Supercritical Conditions”
  • Presentation highlights:
    • Showed P-T diagram for the Allam cycle
      • Two regions of interest
        • CO2 pumping/compression
        • Mixing and combustion at supercritical conditions
  • Part 1 of presentation: molecular structure and thermodynamic properties
    • Discussed thermodynamics of transcritical conditions
    • Macro-models – EOS and mixing rules
      • Limitations exist
    • Can represent fluids as binary mixtures
    • Phase behavior depends on mixture constituents
    • Mixing Type I
      • Type I: Miscible mixing between similar molecules - can be described by common mixing rules
      • single critical line in P-T diagram
    • Mixing Type III
      • More challenging
      • Behave as immiscible mixture between dissimilar molecules
      • 2 critical lines, 3-phase line on P-T diagram
      • Cannot be described by common mixing rules
      • H2O/CO2 falls here
    • Discussion on their molecular dynamic simulations
    • Ar + Kr representative of binary mixture of Type I mixing
      • Simulations transition from liquid-like to gas-like regime
      • Extract macroscopic properties:  Cp vs T at different pressures
      • Peng-Robinson EOS does a reasonable job of predicting Type I mixtures
    • Ne + Kr representative of Type III mixtures
      • In simulations, clusters form – phase separation
      • Qualitatively and quantitatively different mixing behavior vs. the Ar + Kr system
      • Showed Cp vs T at two pressures
      • PR EOS significantly overpredicts heat capacities
    • On-going work
      • Experimental work to examine phase behavior for sCO2
      • Relate scattering signal to thermodynamic response functions for EOS evaluations
    • Conclusions
      • Type I mixtures are well captured by PR and other EOS
      • Type III mixtures are not well captured by PR and other EOS
  • Part 2 of presentation:  turbulent combustion at supercritical conditions
    • Numerical modeling approaches: diffuse-interface method – includes EOS and transport properties
    • Challenges exist in modeling real fluids in supercritical state
    • Modeling results were shared
    • Complex combustion regimes - modeling approaches
      • Topology-based approach
      • Topology-free approach
      • Advantages/disadvantages to each
      • How to choose?
    • Evaluate performance of combustion models
      • Computation cost vs accuracy
      • Pareto-front: optimality between two competing conditions - cost and accuracy
    • Discussed evaluations of model compliance for different combustion models
    • Conclusions
      • Developed Pareto efficient combustion (PEC) framework for general description of complex flame configurations
      • Includes PEC input parameters and PEC model components
      • Application of PEC to a series of flame configurations
  • Q&A followed the presentation

Future Meeting

  • Next meeting will be in October 2019
  • If interested in presenting at a future meeting, contact Seth Lawson