10 12 14 16 18 20 0 40 80 120 160 t-Butanol/O2/N2, =1.0, PC = 15 bar 800 K 811 K 822 K 828 K 838 K 853 K Non- Reactive Pressure, bar Time, ms TC Validation of Kinetic Models of the Butanol Isomers at High Pressure using a Rapid Compression Machine Bryan W. Weber*, Chih-Jen Sung Department of Mechanical Engineering University of Connecticut Storrs, CT, 06269, USA Introduction and Objectives: Rapid Compression Machine: • Single, retractable, piston • Piston is pneumatically driven and hydraulically stopped • Piston is machined with crevices to control the roll-up vortex effect • Pressure and temperature from TDC reported as compressed conditions • The RCM has the ability to vary compressed temperature and compressed pressure independently • Compressed Temperature Range: 680-860 K • Compressed Pressure Range: 15 and 30 bar • Equivalence Ratio: 𝜙= 1.0, 𝑂2: 𝑁2 = 1 ∶3.76 Experimental Conditions: Experimental Analysis: • Ignition is defined by the local maximum of the time derivative of the post-compression pressure • Compressed temperature is computed using a non-reactive run, where oxygen in the mixture is replaced by nitrogen to eliminate reactions while maintaining a similar specific heat ratio Modeling Results: References: [1] Hansen, N., Harper, M.R., and Green, W.H., 7th US National Combustion Meeting, Georgia Institute of Technology, Atlanta, GA, March 20-23, 2011, paper 1B09 [2] Weber, B.W., Kumar, K., Zhang, Y., and Sung, C.J., Combustion and Flame, Volume 158, Issue 5, Pages 809- 819 doi:10.1016/j.combustflame.2011.02.005 [3] Weber, B.W. and Sung, C.J., 7th US National Combustion Meeting, Georgia Institute of Technology, Atlanta, GA, March 20-23, 2011, paper RK13 * bryan.weber@uconn.edu • Energy security and climate change are driving development of fuels from many new sources, particularly renewable bio-sources • Accurate kinetic models are required to enable design of new engine technologies to optimize operation towards emerging non-petroleum derived fuels • The butanol system is the smallest system with primary, secondary, and tertiary alcohols groups • Goal is to provide validation data using a heated rapid compression machine (RCM) at high pressures and low to intermediate temperatures Acknowledgements: This material is based upon work supported as part of the Combustion Energy Frontier Research Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award Number DE-SC0001198 0 10 20 30 40 0 20 40 60 s-Butanol/O2/N2, =1.0, PC=15 bar, TC=827 K P(t), bar P'(t), bar/ms P(t), Non-Reactive Pressure, bar Time Derivative of Pressure, bar/ms Time, ms Ignition Delay,  End of Compression Maximum of P'(t) P'(t) P(t) -10 P(t), Non-Reactive 10 100 1.15 1.2 1.25 1.3 1.35 1.4 Butanol/O2/N2, PC = 15 bar,  = 1.0 s-Butanol i-Butanol n-Butanol t-Butanol Ignition Delay, ms 1000/TC, 1/K O2 : N2 = 1 : 3.76 10 100 1.15 1.2 1.25 1.3 1.35 1.4 1.45 1.5 Butanol/O2/N2, PC = 30 bar,  = 1.0 n-Butanol s-Butanol t-Butanol i-Butanol Ignition Delay, ms 1000/TC, 1/K O2 : N2 = 1 : 3.76 Experimental Results: • Arrhenius plots of the ignition delay show a clear dependence on compressed pressure • The order of reactivity of the isomers changes at higher pressure, from 𝑛−BuOH > 𝑠−BuOH ≈𝑖−BuOH > 𝑡−BuOH at 15 bar to 𝑛−BuOH > 𝑡−BuOH > 𝑠−BuOH > 𝑖−BuOH at 30 bar • There does not appear to be a negative temperature dependence region in these data • Pressure traces from the RCM do not show two-stage ignition for any of the isomers, in either pressure range • However, there is significant pre-ignition heat release for 𝑡−butanol and 𝑛−butanol, but not as much for the other isomers • Constant volume, adiabatic simulations were performed using one recent mechanism from Hansen et al.1 • Simulations do not capture the pressure dependence of 𝑛−butanol ignition delays, under predicting at lower pressure and over predicting at higher pressure • The deviations from experiments for 𝑖−