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Characteristics of knock in hydrogen-oxygen-argon SI engine March 23 rd 2010

Performance Measures x.x, x.x, and x.x. Characteristics of knock in hydrogen-oxygen-argon SI engine March 23 rd 2010. Nick Killingsworth 1 , Daniel Flowers 1 , Salvador Aceves 1 , Vi Rapp 2 , J.-Y. Chen 2 , Robert Dibble 2 1 Lawrence Livermore National Laboratory

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Characteristics of knock in hydrogen-oxygen-argon SI engine March 23 rd 2010

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  1. Performance Measures x.x, x.x, and x.x Characteristics of knock inhydrogen-oxygen-argon SI engineMarch 23rd 2010 Nick Killingsworth1, Daniel Flowers1, Salvador Aceves1, Vi Rapp2, J.-Y. Chen2, Robert Dibble2 1Lawrence Livermore National Laboratory 2University of California, Berkeley 2010 Spring Technical Meeting of the Western States Section of the Combustion Institute, University of Colorado at Boulder LLNL-PRES-408939

  2. Ideal engine efficiency is determined by the compression ratio and specific heat ratio of the fuel-air mixture diesel g =1.4 g =1.3 gasoline engines • = cp/cv, specific heat ratio

  3. Argon’s high specific heat ratio makes it a better working fluid, promoting higher ideal efficiency g =1.67 H2-O2-Ar engines diesel g =1.4 g =1.3 gasoline engines • = cp/cv, specific heat ratio

  4. Absence of carbon and nitrogen in the in-cylinder mixture results in no formation of harmful emissions • H20 and argon are the only emissions • H20 can be condensed out and argon can be recycled • ~1% of the atmosphere is argon • Hydrogen has a high auto ignition temperature Lawrence Livermore National Laboratory

  5. Single-cylinder SI engine with closed intake system used to test H2-O2-Ar operation, allowing control of concentrations of each gas H2 H2 SONIC ORIFICE Ar Ar CFR Engine ArO2 ArO2 N2

  6. We conducted experiments with high levels of argon dilution to maximize g of in-cylinder mixture • Compression ratio varied from 4.5 to 7 • 900 RPM • Stoichiometric H2-O2 mixtures • Tests conducted for the following blends

  7. Initially efficiency increases with compression ratio, however knock limits spark timing past a compression ratio of 4.5 Lawrence Livermore National Laboratory

  8. Auto ignition of the end-gases results in high amplitude pressure waves inside the cylinder *Courtesy Prof. Yuji Ikeda, Kobe University

  9. Indicated thermal efficiency increases with spark advanced, however knock limits how much the spark can be advanced Increasing the spark advanced without knock would allow further increases in the efficiency at a fixed compression ratio

  10. High specific heat ratio of argon also results in high in-cylinder temperatures leading to knock Knock

  11. Knock of gasoline fueled engines is common so we compare knock of H2-O2-Ar mixtures with gasoline-air mixtures H2-O2-Ar, 86% Ar, f = 1, CR = 5.5, 900 rpm 91 octane gasoline-air, f = 1, CR = 8, 900 rpm

  12. Fast Fourier Transforms of single cycle pressure traces of knocking cases of gasoline-air and H2-O2-Ar operation look similar H2-O2-Ar, 86% Ar, f = 1, CR = 5.5, 900 rpm 91 octane gasoline-air, f = 1, CR = 8, 900 rpm 5.1 kHz 5.4 kHz Predicted 1st circumferential vibrational mode ~ 5.6 kHz Sound Speed

  13. The magnitude of knock intensity of both gasoline-air and H2-O2-Ar operation has a similar magnitude for knocking cases of about 2 bar • Knock intensity is defined as the absolute value of the maximum high pass filtered in-cylinder pressure H2-O2-Ar, 86% Ar, f = 1, CR = 5.5, 900 rpm 91 octane gasoline-air, f = 1, CR = 8, 900 rpm

  14. Histograms show that as the spark timing is advanced the number occurrences of knock at higher knock intensities increases H2-O2-Ar, 86% Ar, f = 1, CR = 5.5, 900 rpm 91 octane gasoline-air, f = 1, CR = 8, 900 rpm

  15. As the spark timing is advanced the number occurrences of knock at higher knock intensities increases H2-O2-Ar, 86% Ar, f = 1, CR = 5.5, 900 rpm 91 octane gasoline-air, f = 1, CR = 8, 900 rpm Spark Timing [CAD BTDC] Spark Timing [CAD BTDC]

  16. Knock for H2-O2-Ar mixtures is less stable than for 91 octane gasoline fueled operation • Efficiency of the H2-O2-Ar engine is limited by knock • Important to understand knock at the different conditions of operation with H2-O2-Ar • The CFR engine was designed to knock • Knock limit for H2-O2-Ar will likely be higher in a more modern engine • Higher engine speeds will also reduce the likely hood of knock

  17. Thank you so much for your attention! • Questions ? This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344

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