1. University of Wisconsin -- Engine Research Center slide 1 Using Rapid Compression Machines for Chemical Kinetic studies A Paper by Chih-Jen Sung and Henry J. Curran Reviewed by Michael Groendyk For: ME 769 2/24/15 S.S. Goldsborough (PI), S.A. Ciatti (PI), C.K. Banyon, M.V. Johnson, Argonne National Labs

2. University of Wisconsin -- Engine Research Center slide 2 Topic Overview Rapid Compression machine basics and history Practical limitations on RCM operation Mitigation steps and the characterization of the “Facility Effect”  Heat loss induced pressure drop  The Adiabatic Core Hypothesis  Vortex roll-up Measurement Techniques and analysis Conclusions and recommendations

3. University of Wisconsin -- Engine Research Center slide 3 The Rapid Compression Machine (RCM) Simulates a single compression stroke of an engine High degree of control over initial reactor conditions Variable stroke length allows highly variable compression ratio  Wide operating space in terms of P and T during reaction Studies kinetics under “engine relevant” conditions M.T. Donovan, X. He, B.T. Zigler, T.R. Palmer, M.S. Wooldridge, A. Atreya, Combustion and Flame, May 2004

4. University of Wisconsin -- Engine Research Center slide 4 Practical RCM operation Spatial non-uniformity Finite time compression  Rapid compression is not so rapid vis-à-vis kinetic processes under scrutiny Heat Transfer  Both during compression and reaction phases Vortex roll-up  Exacerbates heat transfer at the walls  Introduces flow in the reactor, leads to non-uniformity Piston momentum transfer  Stopping time  vibrations  etc… Piston asynchronicity

5. University of Wisconsin -- Engine Research Center slide 5 The Facility Effect A combination of factors leads to characteristic compression-relaxation behavior in an RCM Primarily driven by heat loss Quantification and mitigation of the facility effect is of primary importance to understanding RCM Data Once quantified in non- reacting compressions, can be applied to complex reacting events

6. University of Wisconsin -- Engine Research Center slide 6 Direct T measurements not possible. Facility effect produces large deviations from ideal systems: T can be calculated by modifying the compression ratio to account for facility effect. Assuming an “Adiabatic Core” i.e. that heat transfer occurs ONLY at the walls The Adiabatic Core Hypothesis

7. University of Wisconsin -- Engine Research Center slide 7 Preserving the Adiabatic Core Facility effect is reduced by reducing heat transfer Limiting the flow velocity and turbulence in the chamber Heat transfer remains local to the wall

8. University of Wisconsin -- Engine Research Center slide 8 Preserving the Adiabatic Core

9. University of Wisconsin -- Engine Research Center slide 9 RCM Measurement Techniques Traditional Pressure transducer  Assumes uniform reactor pressure  Temperature data acquired from adiabatic core assumption Non-invasive optical measurements  Spatially resolved temperature  Scattering, PLIF, and IR absorption spectroscopy for detailed species time histories Ex-situ gas analysis  Currently in development  Rapid gas sampling from the reactor core removed, quenched and analyzed in detail later RCMs have the potential to provide detailed pressure, temperature and compositional data with high temporal resolution  Furthermore, they can do it with high precision under engine relevant conditions

10. University of Wisconsin -- Engine Research Center slide 10 Conclusions and Recommendations RCM data compliments shock tube and engine chemical kinetic data Highly flexible, precise operation is possible Highly accessible for measurement, both optically and otherwise RCM design can be optimized to reduce deviations from ideal behavior, and to include optical/rapid gas sampling access for detailed measurements Show great promise as tools for combustion kinetics research.