David Frank Davidson

David Frank Davidson
Stanford University | SU · Department of Mechanical Engineering

Ph.D.

About

311
Publications
33,994
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11,779
Citations
Citations since 2017
65 Research Items
6031 Citations
201720182019202020212022202302004006008001,0001,200
201720182019202020212022202302004006008001,0001,200
201720182019202020212022202302004006008001,0001,200
201720182019202020212022202302004006008001,0001,200

Publications

Publications (311)
Article
Two novel laser absorption diagnostics for allene and propyne are presented. Through examination of the high temperature spectra of the two C3H4 isomers via two fast-wavelength-scanning, broadband external cavity quantum cascade lasers, 1930.38 cm⁻¹ and 1233.3 cm⁻¹ were chosen as the wavelengths for a two-species, two-wavelength diagnostic pair tha...
Article
We report the first shock tube measurements of formaldehyde (CH 2 O) during the first stage ignition of n-heptane, 2-methylhexane and 3,3-dimethylpentane, in highly diluted fuel/oxygen mixtures in the pressure range of 7-10 atm and temperature range of 700-880 K. Combined time histories of all carbonyl (-C = O) species, CO and fuel were also measur...
Article
This work presents a novel application of multi-wavelength, multi-species laser absorption methods in the pyrolysis of JP-10 fuel. Two different multi wavelength approaches are used to measure the species from JP-10 pyrolysis in a shock tube at pressures of 2.5–3 atm and temperatures of 1166–1522 K. A five wavelength (5λ) analysis combination produ...
Article
The development of renewable, alternative jet fuels presents an exigent challenge to the aviation community. In this work, a streamlined methodology for building computationally efficient kinetic models of real fuels from shock tube experiments is developed and applied to a low cetane-number, broad-boiling alternative jet fuel (termed C-4). A multi...
Article
The rate constant for the reaction CH3+C2H6→CH4+C2H5 was studied behind reflected shock waves at temperatures between 1369 and 1626 K and pressures from 8.6 to 47.4 atm in mixtures of methane, ethane and argon. Ethylene time-histories were measured using laser absorption of radiation from a carbon dioxide gas laser near 10.532 microns. The resultin...
Article
The average burning velocities S¯b of premixed, spherically expanding iso-octane flames are reported for flame radii from 0.75 to 1.75 cm between 400 and 900 K, near 1 atm. Measurements are performed in lean mixtures (0.9 equivalence ratio) using a helium-enriched oxidizer (18% oxygen, 41% nitrogen, and 41% helium) to inhibit thermodiffusive instab...
Article
Full-text available
The constrained reaction volume (CRV) method for shock-tube experiments makes it possible to conduct chemical kinetics studies at nearly constant pressure while inhibiting remote ignition. The application of end-wall imaging revealed, however, that CRV experiments are susceptible to vertical stratification at the interface of the test and buffer ga...
Conference Paper
The speed at which a laminar flame consumes an unburned, flammable mixture represents one of the mostimportant quantities in combustion science. Premixed flames appear in many of the combustion systems upon which society relies. One ubiquitous occurrence of these flames is in spark ignition (SI) engines, where an understanding of flame propagation...
Article
High-temperature methane and propane laminar flame speed measurements were conducted behind reflected shock waves in a shock tube. A high-power Nd:YAG laser was used to spark-ignite the shock-heated gas mixtures and initiate laminar flame propagation. High-speed, OH* endwall imaging was used to record the propagation of the spherically expanding fl...
Conference Paper
Full-text available
Laminar premixed n-heptane flames are recorded at various extents of reaction of the unburned gas, both prior to and following homogeneous 1st-stage ignition. A shock tube is used to heat n-heptane/oxidizer mixtures to near 715 K and 1.8 atm, conditions associated with two-stage, negative temperature coefficient ignition behavior. After a controlle...
Article
Species time-history measurements provide important kinetics targets for the development and validation of detailed reaction models. Here, a multi-wavelength, multi-species laser absorption strategy is demonstrated that provides high-bandwidth species time-histories during 1-butene pyrolysis behind reflected shock waves. Measured shock tube absorba...
Article
Ignition delay times (IDT) of n-heptane, iso-octane, n-dodecane, and iso-octane/n-dodecane blends, in stoichiometric mixtures with air, were measured behind reflected shock waves in a heated, high-pressure shock tube. Measurements were taken at temperatures of 665–1250 K, pressures of 28–70 atm, and equivalence ratios near unity. Pressure time-hist...
Article
The reaction rate of H + O2+M = HO2+M in the low-pressure limit was determined in the temperature range of 1450– 2000 K, with Argon, Nitrogen, and Carbon Dioxide as the third-body collision partners, by measuring the OH time-history after the induction time during lean oxidation of Hydrogen. Test conditions were optimized to suppress the sensitivit...
Article
A new spectroscopic predictor for estimating ignition characteristics including derived cetane number is proposed for hydrocarbon fuels. This spectroscopic predictor is the ratio of room temperature absorbance of unreacted fuel vapor at 3.41 and 3.39 μm, termed here as the “3.41/3.39 absorption ratio.” Its wide availability and applicability are de...
Conference Paper
Full-text available
Laminar flame speed, temperature, and species (CO2 and H2O) measurements were conducted in high-temperature, spherically expanding ethane flames. The experiments were conducted in a shock tube, which allows access to a high-temperature regime previously unexplored for premixed ethane-air flames. The stoichiometric ethane-air mixtures were initially...
Preprint
Full-text available
Pyrolysis of ethanol was studied behind reflected shock waves at 10 atm in the Stanford High-Pressure Shock Tube (HPST) facility, in the temperature range of 1200 K-1600 K. Laser absorption spectroscopy was used to measure the time history of CO, C2H4, and C2H5OH during these experiments. Significant disagreements were found between these measureme...
Conference Paper
Full-text available
Recent advances in experimental methods facilitating measurements of first-stage ignition products of iso-octane in a shock tube are reported. A novel mixture composition consisting of very lean fuel equivalence ratios (φ= 0.1) in pure oxygen was selected to increase the effective pressure of experiments by nearly a factor of five compared to stand...
Conference Paper
Laminar burning velocities (SL) of n-heptane and iso-octane are measured between 400 and 900 K at 1 atm and 0.9 equivalence ratio. A shock tube is used to heat the unburned gas to temperatures at which it would auto-ignite, while limiting the time for ignition chemistry to occur ahead of the flame to much less than the ignition delay time. In air (...
Chapter
In engine applications, small concentrations of very reactive chemical species such as nitric oxide (NO) can have a very important impact on the onset of combustion. The small amount of NO can come from various sources including EGR, residual gas, and vitiated oxidizer streams. Combustion of distillate fuels and their surrogates with NO addition af...
Chapter
As part of the effort to understand oxy-fuel combustion with large CO2 dilution, we have measured shock tube ignition delay times for methane/O2/CO2 mixtures and hydrogen/O2/CO2 mixtures. Ignition delay times (IDT) were measured using sidewall pressure and OH* emission near 306 nm. IDT measurements were performed near 80 atm for 3.91% methane/9.92%...
Article
The rate constant for the reaction C2H4+H⇒C2H3+H2 was studied behind reflected shock waves at temperatures between 1619 and 1948 K and pressures near 10 atm in a mixture of C2H4, CH4, H2, and argon. C2H4 time-histories were measured using laser absorption of a CO2 gas laser near 10.53 microns. Experimental mixtures were designed to optimize sensiti...
Article
A framework for the study of high-temperature hydrocarbon pyrolysis is presented. The proposed framework details a multi-wavelength speciation method using convex optimization, a review of complementary fixed-wavelength laser diagnostics, and a database of high-temperature absorption cross-sections to enable use of the framework for 11 different sp...
Article
Full-text available
Shock tube ignition delay times and species time history measurements for Primary Reference Fuels (PRFs) such as normal heptane provide targets for the validation of combustion models, which in turn are used to develop more fuel-efficient engines that have smaller environmental footprints. However, a review of the literature has revealed that most...
Article
Full-text available
Homogeneous and inhomogeneous ignition of real and surrogate fuels were imaged in two Stanford shock tubes, revealing the influence of small particle fragmentation. n-Heptane, iso-octane, and Jet A were studied, each mixed in an oxidizer containing 21% oxygen and ignited at low temperatures (900–1000 K), low pressures (1–2 atm), with an equivalence...
Article
The Hybrid Chemistry (HyChem) approach has been proposed previously for combustion chemistry modeling of real, liquid fuels of a distillate origin. In this work, the applicability of the HyChem approach is tested for single-component fuels using JP10 as the model fuel. The method remains the same: an experimentally constrained, lumped single-fuel m...
Article
The development of compact HyChem hybrid models for jet fuels requires datasets of pyrolysis product yields to constrain the model and of kinetic targets to evaluate the model. To this end, we have measured selected species time-histories during fuel pyrolysis using laser absorption, and ignition delay times using multiple methods behind reflected...
Article
Ignition delay times (IDT) of small hydrocarbons at elevated pressures provide a valuable constraint for the refinement of the core small-hydrocarbon sub-mechanisms used in all combustion kinetics. Current knowledge of these core mechanisms is based largely on low-pressure data, with only limited high-pressure data available. To remedy this, the pr...
Article
A Hybrid Chemistry (HyChem) approach has been recently developed for the modeling of real fuels; it incorporates a basic understanding about the combustion chemistry of multicomponent liquid fuels that overcomes some of the limitations of the conventional surrogate fuel approach. The present work extends this approach to modeling the combustion beh...
Article
The need for more efficient power cycles has attracted interest in super-critical CO2 (sCO2) cycles. However, the effects of high CO2 dilution on auto-ignition at extremely high pressures has not been studied in depth. As part of the effort to understand oxy-fuel combustion with massive CO2 dilution, we have measured shock tube ignition delay times...
Article
Ignition delay times (IDT) for high-octane-number gasolines and gasoline surrogates were measured at very high pressures behind reflected shock waves. Fuels tested include gasoline, gasoline with oxygenates, and two surrogate fuels, one dominated by iso-octane and one by toluene. RON/MON for the fuels varied from 101/94 to 106.5/91.5. Measurements...
Article
A novel, multi-species, combined laser absorption/gas chromatography (GC) speciation diagnostic was used to quantify intermediate species present in the low-temperature oxidation of 1.0% n-heptane in 20.8% O2/Ar and 20.8% O2/0.21% CO2/Ar (equivalence ratio 0.53) at 760 K, 4.9 atm. Laser absorption techniques were used to measure initial fuel and ti...
Article
The rate constants for the reaction H + O2 + M→HO2 + M were investigated at elevated pressures from 12 to 33 atm using ignition delay time (IDT) measurements behind reflected shock waves in H2/O2/M mixtures with different collision partners M = Ar, H2O, N2 and CO2. The temperature and pressure ranges where the rate constants of the reactions H + O2...
Article
Full-text available
Microsecond-resolved measurements of OH concentrations time-histories were performed during the oxidation of four common monocyclic aromatic hydrocarbons, namely benzene, toluene, ethylbenzene and o-xylene, behind reflected shock waves. Ar-diluted mixtures of 200 ppm aromatics in stoichiometric O2 were shock-heated to temperatures of 1513-1877 K an...
Article
The first implementation of a combined laser absorption diagnostic/gas chromatography (GC) sampling system for the measurement of combustion-relevant species in a conventional shock tube configuration is reported, with ethylene pyrolysis as an example application. A heated, endwall sampling system is used to extract a post-shock sample for GC analy...
Article
We propose and test an alternative approach to modeling high-temperature combustion chemistry of multicomponent real fuels. The hybrid chemistry (HyChem) approach decouples fuel pyrolysis from the oxidation of fuel pyrolysis products. The pyrolysis (or oxidative pyrolysis) process is modeled by seven lumped reaction steps in which the stoichiometri...
Article
Real distillate fuels usually contain thousands of hydrocarbon components. Over a wide range of combustion conditions, large hydrocarbon molecules undergo thermal decomposition to form a small set of low molecular weight fragments. In the case of conventional petroleum-derived fuels, the composition variation of the decomposition products is washed...
Article
A two-wavelength infrared laser absorption diagnostic for non-intrusive, simultaneous quantitative measurement of propene and ethylene was developed. To this end, measurements of absorption cross sections of propene and potential interfering species at 10.958 μ m were acquired at high-temperatures. When used in conjunction with existing absorption...
Article
The oxidation of Ar-diluted stoichiometric CH2O-O2 mixtures was studied behind reflected shock waves over temperatures of 1332 - 1685 K, at pressures of about 1.5 atm and initial CH2O mole fractions of 500ppm, 1500ppm, and 5000ppm. Quantitative and time-resolved concentration histories of OH and CO (at both v” = 0 and v” = 1) were measured by narro...
Article
In view of a desired transition from fossil fuels to sustainably produced biofuels that should contribute to a net reduction of CO2 emissions, promising fuel candidates have been identified including 2-butanone (methyl ethyl ketone, MEK) that is qualified for use in spark-ignition (SI) engines. To support a potential, rapid integration of such biof...
Chapter
Intrinsic to the development of CFD models for jet engines are embedded chemical kinetics reaction mechanisms for the pyrolysis and oxidation of jet fuels. The development and refinement of these reaction mechanisms require an experimental kinetic target database for mechanism constraint and validation. Here, shock tube/laser absorption species tim...
Chapter
Current shock tube combustion experiments generally assume that the test environment behind a reflected shock wave is quiescent and that ignition processes progress uniformly over the entire test volume. However, various past investigations, including those based on schlieren data and sidewall imaging [1, 2], have observed nonuniform ignition in ce...
Chapter
Chemical kinetics plays a crucial role in many high-temperature flows of engineering and scientific interest, particularly including combustion and propulsion systems. Despite significant progress in the fundamental theories associated with chemical kinetics, this field still relies very heavily on experimentation and shock tubes have become a prim...
Article
Full-text available
The potential energy surfaces (PESs) and reaction rate constants of the unimolecular decomposition of ethyl formate (EF) were investigated using high-precision theoretical methods at the CCSD(T)/CBS(T-Q)//M06-2x/6-311++G(d,p) level of theory. The calculated PESs of EF dissociation and molecular decomposition reactions prove that the intramolecular...
Article
We report the development of a novel laser absorption diagnostic for accurate, time-resolved and in situ measurement of various hydrocarbon fuels in combustion systems. This diagnostic method utilized a wavelength-tunable interband cascade laser operated near 3.41 μm, providing improved performance in several aspects over the conventional 3.39-μm H...
Article
Full-text available
The unimolecular decomposition kinetics of methyl propanoate (MP), including the direct C−O/C−C bond fissions and molecular reaction channels, were studied by using high-level ab initio calculations and Rice–Ramsperger–Kassel–Marcus/master equation (RRKM/ME) theory. Four homolytic bond-fission and ten hydrogen transfer reactions of the MP unimolecu...
Conference Paper
Full-text available
Real fuels may contain thousands of hydrocarbon components. This paper examines how nature simplifies the problem. We will discuss the internal structure of the fuel oxidation process at high temperatures. Over a wide range of conditions, large hydrocarbon molecules undergo thermal decomposition to form a small set of low-molecular weight fragments...
Conference Paper
In this work we introduce an unconventional approach to modeling the high-temperature combustion chemistry of multicomponent real fuels. The hybrid chemistry (HyChem) approach decouples fuel pyrolysis from the oxidation of fuel decomposition intermediates. The thermal decomposition and oxidative thermal decomposition processes are modeled by seven...
Conference Paper
Full-text available
We report the development of a novel laser absorption diagnostic for accurate, time-resolved and in situ measurement of various hydrocarbon fuels in combustion systems. This diagnostic method utilized a wavelength-tunable interband cascade laser operated near 3.41 µm, providing improved performance over the conventional 3.39-µm He-Ne gas laser diag...
Conference Paper
Full-text available
The development of a compact HyChem reaction mechanisms for jet fuels requires datasets both for pyrolysis products yields to constrain the model and for kinetic targets to evaluate the model. To this end, we have measured selected species time-histories during fuel pyrolysis using laser absorption, and ignition delay times using multiple methods b...
Conference Paper
With increasing use of alternative fuels, approaches that can efficiently model their combustion chemistry are essential to facilitate their utilization. The hybrid chemistry (HyChem) method incorporates a basic understanding about the combustion chemistry of multicomponent liquid fuels that overcomes some of the limitations of the surrogate fuel a...
Conference Paper
The hybrid chemistry modeling approach, termed HyChem, was used to explore the combustion chemistry of blended petroleum and bio-derived jet fuels. The pyrolysis products of conventional petroleum derived-fuels, such as Jet A, are dominated by ethylene and propene, whereas in many bio-derived fuels, such as alcohol to jet (ATJ) fuels, the fuel comp...
Conference Paper
The first implementation of a combined laser absorption diagnostic/gas chromatography (GC) sampling system for the measurement of combustion-relevant species in a conventional shock tube configuration is reported. A heated, sidewall sampling system is used to extract a post-shock sample for GC analysis. Analysis of the gas sample yields a measureme...
Article
The purpose of this article is to explore the dependence of calculated postshock thermodynamic properties in shock tube experiments upon the vibrational state of the test gas and upon the uncertainties inherent to calculation inputs. This paper first offers a comparison between state variables calculated according to a Rankine–Hugoniot–equation-bas...
Article
Ignition delay times were measured behind reflected shock waves in a shock tube for a wide variety of distillate fuels over a range of temperatures, pressures and mixtures. The fuels studied include: jet fuels (JP-5, JP-8, and Jet A), rocket propellants (RP-2), diesel fuels (F-76 and DF-2) and gasoline. A simple correlation was found to describe th...
Article
A novel three-color, three-species laser absorption sensor for measurement of small (C2–C4) alkenes is introduced. This scheme, combined with an existing two-color CH4 ICL laser sensor and an existing one-color HeNe laser fuel sensor, was applied to the study of the decomposition of a bio-derived, highly-branched alcohol-to-jet (ATJ) test fuel in a...
Article
The formation of electronically excited atomic oxygen was studied behind reflected shock waves using cavity-enhanced absorption spectroscopy. Mixtures of 1% O2/Ar were shock-heated to 5400-7500 K and two distributed-feedback diode lasers near 777.2 and 844.6 nm were used to measure time-resolved populations of atomic oxygen's (5)S° and (3)S° electr...
Article
In this study we report a novel UV laser absorption diagnostic for sensitive and time-resolved measurement of methyl radicals (CH3) in shock tube kinetics studies, utilizing a frequency-quadrupled, high-repetition-rate (78 MHz) ps-pulsed Ti-sapphire laser targeted at the strong rovibronic transition of CH3 at 216.62 nm. This diagnostic employs a ca...
Article
The rate constant of acetaldehyde thermal dissociation, CH3CHO = CH3 + HCO, was measured behind reflected shock waves at temperatures of 1273 - 1618 K and pressures near 1.6 atm and 0.34 atm. The current measurement utilized sensitive CO diagnostics to track the dissociation of CH3CHO via oxygen atom balance, and inferred the title rate constant (k...
Article
We report an improved measurement for the rate constant of methane dissociation in argon (CH4 + Ar = CH3 + H + Ar) behind reflected shock waves. The experiment was conducted using a sub-ppm sensitivity CH3 diagnostic recently developed in our laboratory based on ultra-violet cavity-enhanced absorption spectroscopy (CEAS). The high sensitivity of th...
Article
High-temperature methyl acetate (MA) pyrolysis and oxidation were studied behind reflected shock waves using laser-absorption species time-history measurements of CO, CO2, OH and H2O. The shock tube experiments with very dilute fuel mixtures covered a temperature range of 1401–1605 K for MA pyrolysis (0.2% MA/Ar) and 1423–1674 K for MA oxidation (0...
Article
The overall rate constants for the H-abstraction reactions of a series of aldehydes, namely isobutyraldehyde (i-C3H7CHO), n-valeraldehyde (n-C4H9CHO), isovaleraldehyde (i-C4H9CHO), trans-2-pentenal (C2H5CH=CHCHO), trimethylacetaldehyde ((CH3)3CCHO) and benzaldehyde (C6H5CHO), by hydroxyl radicals (OH), were studied behind reflected shock waves at t...
Article
Full-text available
A high-speed OH* chemiluminescence imaging diagnostic was developed to image the structure and homogeneity of combustion events behind reflected shock waves in the Stanford Constrained Reaction Volume Shock Tube. An intensified high-repetition-rate imaging system was used to acquire images of OH* chemiluminescence (near 308 nm) through a fused quar...
Article
The dissociation rate coefficient for oxygen in argon, O2 + Ar ⇌ O + O + Ar, was measured using laser absorption near 216 nm in the Schumann-Runge system in a shock tube. A mixture of 2% oxygen in argon was studied behind reflected shocks at initial equilibrium temperatures from 4400 to 7900 K and pressures from 0.2 to 1 atm. The dissociation was m...
Article
High-temperature Arrhenius ignition delay time correlations are useful for revealing the underlying parameter dependencies of combustion models, for simplifying and optimizing combustion mechanisms for use in engine simulations, for scaling experimental data to new conditions for comparison purposes, and for guiding in experimental design. We have...
Article
We report the first application of cavity-enhanced absorption spectroscopy (CEAS) with a ps-pulsed UV laser for sensitive and rapid gaseous species time-history measurements in a transient environment (in this study, a shock tube). The broadband nature of the ps pulses enabled instantaneous coupling of the laser beam into roughly a thousand cavity...
Conference Paper
Full-text available
Thermal cracking of the long-chained hydrocarbons present in liquid fuels produces low-molecular weight species such as hydrogen, methane, ethylene, ethane and propylene. These hydrocarbons crack due to an oxidation process or during endothermic cooling of a high-speed propulsion system. In this work, experiments and chemical kinetic modeling were...
Article
The rate coefficient for the reaction of methanol (CH3OH) with the hydroxyl (OH) radical was determined in reflected shock wave experiments at temperatures of 961-1231 K and pressures of 1.18-1.48 atm. Pseudo-first order reaction conditions were achieved with mixtures of CH3OH and tert-butyl hydroperoxide (TBHP) diluted in argon. Rapid thermal deco...
Article
The vibrational relaxation times of oxygen were measured using laser absorption spectroscopy behind incident and reflected shocks in a shock tube. The Bethe–Teller equation was used to model the vibrational relaxation, which (along with the shock jump relations) was used to model the gas dynamics conditions throughout the nonequilibrium relaxation...
Article
Full-text available
Several techniques have been developed for obtaining long, constant-pressure test times in reflected shock wave experiments in a shock tube, including the use of driver inserts, driver gas tailoring, helium gas diaphragm interfaces, driver extensions, and staged driver gas filling. These techniques are detailed here, including discussion on the mos...