SCO2 Oxy-Combustion Working Group

Presentation

• 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