DECOMPOSITION KINETICS OF THE ROCKET PROPELLANT RP-1 AND ITS CHEMICAL KINETIC SURROGATES ADISSERTATION SUBMITTED TO THE DEPARTMENT OF MECHANICAL ENGINEERING AND THE COMMITTEE ON GRADUATE STUDIES OF STANFORD UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Megan Edwards MacDonald January 2012 © 2012 by Megan Edwards MacDonald. All Rights Reserved. Re-distributed by Stanford University under license with the author. This work is licensed under a Creative Commons Attribution- Noncommercial 3.0 United States License. http://creativecommons.org/licenses/by-nc/3.0/us/ This dissertation is online at: http://purl.stanford.edu/ng820gf9574 ii I certify that I have read this dissertation and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy. Ronald Hanson, Primary Adviser I certify that I have read this dissertation and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy. Craig Bowman I certify that I have read this dissertation and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy. Reginald Mitchell Approved for the Stanford University Committee on Graduate Studies. Patricia J. Gumport, Vice Provost Graduate Education This signature page was generated electronically upon submission of this dissertation in electronic format. An original signed hard copy of the signature page is on file in University Archives. iii iv Abstract High-temperature fuel decomposition is an important aspect of fuel chemistry, and athoroughunderstandingofthisprocess is necessary in order to accurately de- scribe combustion chemistry. The study of kerosene rocket fuels is especially of interest today as the launch industry grows. Two major motivations drive the study of kerosene decomposition. First, it is a vital building block upon which ox- idation chemistry can be built, and second, it is used as a coolant in many rockets and high-speed aircraft. As state-of-the-art pushes combustor temperatures higher (requiring greater cooling capabilities), additional studies of the high-temperature decomposition of kerosene fuels will be necessary. Previous studies of the decom- position of rocket propellants are limited to temperatures below approximately 1100 K. Measurements of fuel and ethylene time histories during decomposition of RP- fuels and their possible surrogate components were carried out between 1000 and 1500 K in two shock tubes, the Aerosol Shock Tube (AST), for experiments between 4and8atm,andtheHighPressureShockTube(HPST),forexperimentsbetween 18 and 51 atm. Three diagnostics were utilized, a visible or near-infrared diode laser for aerosol scattering measurements in the AST, a 3.39 µmmid-infrared HeNe gas laser for measurements of fuel mole fractions, and a CO2 gas laser for measurements of ethylene mole fractions near 10.5 µm. Prior to shock tube studies of the decomposition of these fuels, their absorption cross sections were measured at 3.39 µmandatthetwoCO2 laser wavelengths utilized for this study. Low- temperature (300 to 800 K) absorption cross sections were measured in a Fourier Transform Infrared (FTIR) Spectrometer and high-temperature (800 to 1500 K) cross sections were measured in the shock tube. Measurements of the fuel time histories and overall fuel decomposition rates for six fuels (RP-1, RP-2, JP-7, n-dodecane, methylcyclohexane, and iso-cetane) v are reported. Similar measurements were also completed on mixtures of the poten- tial fuel additives 1,2,3,4-tetrahydroquinoline and benzyl alcohol with RP-1 and n-dodecane. A new method was developed for correcting the 3.39 µmHeNeab- sorbance measurement for interfering species. Measurements of the ethylene time histories and ethylene yields for four fuels (RP-1, n-dodecane, methylcyclohexane,andiso-cetane)arealsoreported.The ethylene diagnostic was improved to utilize two wavelengths as a means of ac- counting for interference in the ethylene measurement, and adapted for utilization at high temperatures. An RP-fuel surrogate was formulated based on three targets, or characteristics to be matched with the real fuel: compound class, overall fuel decomposition rate, and ethylene yield. This resulted in a surrogate containing 32% n-dodecane, 59% methylcyclohexane, and 9% iso-cetane. Modeling efforts with this surrogate have shown good agreement with experimental measurements of actual RP-1 fuel. vi Acknowledgements First, I would like to thank my advisor, Ron Hanson, for his guidance through this process and for teaching me to be an independent thinker. Thanks also to Dave Davidson, who has always been available to offer advice and guidance. The Hanson Lab is an incredible group of students who have been supportive and helpful through the times when nothing is working and then excited to hear when experiments are finally going well. Thanks to all. I would especially like to thank Dan Haylett, Matt Campbell, Genny Pang, Adela Bardos, and Greg Rieker for the many conversations about both lab and life. Icouldnothaveaskedforabettergroupoffriendsfromwhichtodrawsupport during this work. Thanks to Todd White, Brandon Oliver, and Ariane Chepko for the many thoughtful conversations and fun times throughout the years, both before and during my time at Stanford. Thanks to Emily Sayles for being a fantastic listener and for encouraging me to push myself beyond my self-perceived limits. And thanks to all my friends who have been integral in maintaining my mental health over the last few years. Lastly, and most importantly, I would like to thank my mom, dad, and sister Abby (who beat me to doctor), who have been a constant anchor and support in times of trouble and with whom I am blessed to share times of joy. vii Contents Abstract v Acknowledgements vii 1Introduction 1 1.1 Motivation................................ 1 1.2 Objectives................................ 4 1.3 Organization .............................. 4 2LiteratureReview 5 2.1 Kerosenes ................................ 5 2.2 n-Dodecane ............................... 7 2.3 Methylcyclohexane(MCH). .. .. 8 2.4 2,2,4,4,6,8,8-Heptamethylnonane (iso-Cetane) . 9 2.5 Additives ................................ 9 2.6 Summary of Historic Decomposition Rates . 10 3TheoreticalBackground 12 3.1 SpectroscopicandKineticTheory . 12 3.2 SelectionofLaserLines......................... 13 3.3 CorrectionsforInterferingSpecies . 15 3.4 Soot ................................... 20 4ExperimentalSetup 22 4.1 AerosolShockTube........................... 23 4.2 High-PressureShockTube . 25 4.3 HPSTWindowDesign ......................... 28 viii 4.4 Fuels................................... 30 5AbsorptionCrossSections 34 5.1 n-Dodecane ............................... 35 5.2 RP-1................................... 36 5.3 RP-2................................... 38 5.4 JP-7 ................................... 39 5.5 JP-8 ................................... 41 5.6 THQ................................... 41 5.7 MCH................................... 43 5.8 iso-Cetane................................ 43 5.9 SmallAlkenes.............................. 45 5.10Summary ................................ 47 6ShockExperimentsonSixFuels 50 6.1 RP-1................................... 50 6.1.1 Facilities and Diagnostics .................... 50 6.1.2 FuelMeasurements ....................... 51 6.1.3 EthyleneMeasurements . 54 6.1.4 Discussion of Findings . 55 6.2 RP-2................................... 58 6.2.1 Facilities and Diagnostics .................... 58 6.2.2 FuelMeasurements ....................... 58 6.2.3 Discussion of Findings . 59 6.3 JP-7 ................................... 61 6.3.1 Facilities and Diagnostics .................... 61 6.3.2 FuelMeasurements ....................... 61 6.3.3 Discussion of Findings . 62 6.4 n-Dodecane ............................... 63 6.4.1 Facilities and Diagnostics .................... 63 6.4.2 FuelMeasurements ....................... 64 6.4.3 EthyleneMeasurements . 65 6.4.4 Discussion of Findings . 66 6.5 Methylcyclohexane(MCH). 72 6.5.1 Facilities and Diagnostics .................... 72 ix 6.5.2 FuelMeasurements ....................... 72 6.5.3 EthyleneMeasurements . 73 6.5.4 Discussion of Findings . 74 6.6 2,2,4,4,6,8,8-Heptamethylnonane (iso-Cetane) . 77 6.6.1 Facilities and Diagnostics .................... 77 6.6.2 FuelMeasurements ....................... 77 6.6.3 EthyleneMeasurements . 78 6.6.4 Discussion of Findings . 78 6.7 Summary ................................ 82 7ShockExperimentswithFuelAdditives 86 7.1 1,2,3,4-Tetrahydroquinoline (THQ) . 86 7.2 BenzylAlcohol(BzOH)......................... 89 7.3 Summary ................................ 91 8FormulationofanRP-1PyrolysisSurrogate 92 8.1 CompoundClass ............................ 93 8.2 OverallFuelDecompositionRate . 95 8.3 Ethylene Yield . 96 8.4 Determination of Surrogate Component Mole Fractions . ..... 96 8.5 MechanismPredictions . 100 9SummaryandFutureWork 103 9.1 Summary ................................103 9.2 FutureWork...............................104 AFuelTimeHistoryCorrection 107 A.1 OverallFuelDecompositionRate . 109 A.2 FuelMoleFraction ...........................110 A.3 Comparison of Simple Model with Detailed Mechanism Method . 112 BShockData 115 CSupercriticalFluidvs.Gas-PhaseKinetics 126 Bibliography 129 x List of Tables 2.1 Multi-component RP-1 surrogate #1 . ................ 6 2.2 Multi-component RP-1 surrogate #2 . ...............