Matthew Oehlschlaeger - Academia.edu (original) (raw)

Papers by Matthew Oehlschlaeger

Combustion and Flame, 2006

The reaction of toluene with molecular oxygen to yield benzyl and hydroperoxyl radicals has been ... more The reaction of toluene with molecular oxygen to yield benzyl and hydroperoxyl radicals has been studied using ultraviolet laser absorption of benzyl radicals at 266 nm in shock-heated gases. Test gas mixtures of toluene with excess oxygen diluted in helium and argon were heated in reflected shock waves to temperatures ranging from 1117 to 1366 K at total pressures around 1.7 bar. The growth in benzyl absorbance was monitored at 266 nm, allowing determination of the rate coefficient for the C 6 H 5 CH 3 + O 2 → C 6 H 5 CH 2 + HO 2 , reaction (1). The high signalto-noise ratio provided by laser absorption provides rate coefficient determinations with an estimated uncertainty of ±20%. Fitting both these high-temperature shock tube results and the rate recommendation of Ingham et al. [Proc. Combust. Inst. 25 (1994) 767-774] at 773 K, the rate coefficient for reaction (1) can be described with a three-parameter Arrhenius expression by k 1 (T ) = 2.18 × 10 7 T 2.5 exp(−46,045 [cal/mol]/RT ) [cm 3 mol −1 s −1 ]. In addition, the measured benzyl time-histories can be used as experimental targets for the development and validation of detailed mechanisms for toluene oxidation.

The ignition of methylcyclohexane (MCH)/air and ethylcyclohexane (ECH)/air mix- tures has been st... more The ignition of methylcyclohexane (MCH)/air and ethylcyclohexane (ECH)/air mix- tures has been studied in a shock tube at temperatures and pressures ranging from 881 to 1319 K and 10.8 to 69.5 atm, respectively, for equivalence ratios of 0.25, 0.5, and 1.0. Endwall OH* emission and sidewall pressure measurements were used to determine ignition delay times. The influence of temperature, pressure,

37th Joint Propulsion Conference and Exhibit, 2001

Butanol, an alcohol which can be produced from biomass sources, has received recent interest as a... more Butanol, an alcohol which can be produced from biomass sources, has received recent interest as an alternative to gasoline for use in spark ignition engines and as a possible blending compound with fossil diesel or biodiesel. Therefore, the autoignition of the four isomers of butanol (1-butanol, 2-butanol, iso-butanol, and tert-butanol) has been experimentally studied at high temperatures in a shock

Volume 2: Heat Transfer Enhancement for Practical Applications; Heat and Mass Transfer in Fire and Combustion; Heat Transfer in Multiphase Systems; Heat and Mass Transfer in Biotechnology, 2013

ABSTRACT The autoignition of fatty-acid methyl ester biodiesels and methyl ester biodiesel compon... more ABSTRACT The autoignition of fatty-acid methyl ester biodiesels and methyl ester biodiesel components was studied in gas-phase shock tube experiments. Ignition delay times for two reference methyl ester biodiesel fuels, derived from methanol-based transesterification of soybean oil and animal fats, and four primary constituents of all methyl ester biodiesels, methyl palmitate, methyl stearate, methyl oleate, and methyl linoleate, were measured behind reflected shock waves for fuel/air mixtures at temperatures ranging from 900 to 1350 K and at pressures around 10 and 20 atm. Ignition delay times were determined by monitoring pressure and chemiluminescence from electronically-excited OH radicals around 310 nm. The results show similarity in ignition delay times for all methyl ester fuels considered, irrespective of the variations in organic structure, at the high-temperature conditions studied and also similarity in high-temperature ignition delay times for methyl esters and n-alkanes.

Journal of Thermal Science and Engineering Applications, 2013

Biofuels have the potential to be sustainable, secure, low carbon footprint transportation fuels.... more Biofuels have the potential to be sustainable, secure, low carbon footprint transportation fuels. Primarily due to government mandates, biofuels have become increasingly adopted as transportation fuels over the last decade and are projected to steadily increase in production. Here the prospects of biofuels are summarized in terms of several important performance measures, including: lifecycle greenhouse gas (GHG) emissions, energy return on investment (EROI), land and water requirements, and tailpipe emissions. A review of the literature leads to the conclusion that most first-generation biofuels, including corn ethanol and soybean biodiesel produced in the United States, reduce tailpipe pollutant emissions and GHG emissions-provided their feedstocks do not replace large quantities of fixed carbon. However, their production is perhaps unsustainable due to low EROI and significant land-use and water requirements. Second-generation biofuels; for example ethanol produced from lignocellulosic biomass, have the potential for larger reductions in GHG emissions and can provide sustainable EROI with reasonable land area usage; however, they require water inputs several orders-of-magnitude greater than required by petroleum fuels. Advanced biofuels from algal oils and synthetic biological processes are further from commercial reality and require more assessment but potentially offer better performance due to their orders-of-magnitude greater yields per land area and lower water requirements; at present, the energy costs of such biofuels are uncertain.

Proceedings of the Combustion Institute, 2009

... Permissions & Reprints. A shock tube study of the auto-ignition of toluene/air mi... more ... Permissions & Reprints. A shock tube study of the auto-ignition of toluene/air mixtures at high pressures. Hsi-Ping S. Shen a , Jeremy Vanderover a and Matthew A. Oehlschlaeger Corresponding Author Contact Information , a , E-mail The Corresponding Author. ...

Volume 1: Heat Transfer in Energy Systems; Thermophysical Properties; Theory and Fundamental Research in Heat Transfer, 2013

ABSTRACT Nanofluids, stable colloidal suspensions of nanoparticles in a base fluid, have potentia... more ABSTRACT Nanofluids, stable colloidal suspensions of nanoparticles in a base fluid, have potential applications in the heat transfer, combustion and propulsion, manufacturing, and medical fields. Experiments were conducted to determine the evaporation rate of room temperature, millimeter-sized pendant droplets of ethanol laden with varying (0–3%) weight percentages of 40–60 nm aluminum nanoparticles (nAl). High-resolution droplet images were collected as a function of time for the determination of D-square law evaporation rates. Results show an asymptotic decrease in droplet evaporation rate with increasing nAl loading. The evaporation rate decreases by approximately 15% at around 1% to 3% nAl loading relative to the evaporation rate of pure ethanol, a reduction greater than can be explained by reduction in the vapor pressure of an ideal nanofluid mixture by Raoult’s law. It is hypothesized that the reduction in evaporation rate could be due to two phenomena: 1) the reduction in the ethanol volume fraction available for evaporation due to an interfacial layer on the immersed nanoparticle surface and 2) the aggregation of nanoparticles within the droplet and at the droplet surface, reducing the liquid diffusion rate to the surface and the liquid volume fraction at the surface available for evaporation.

Propellants, Explosives, Pyrotechnics, 2014

50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2012

Journal of Quantitative Spectroscopy & Radiative Transfer, 2005

The absorption of ultraviolet narrow-line laser radiation by methyl radicals (CH3) in the B2A1′←X... more The absorption of ultraviolet narrow-line laser radiation by methyl radicals (CH3) in the B2A1′←X2A2″ electronic system has been studied at high temperatures behind shock waves. Methyl radicals at high temperatures were generated by the shock heating of methyl precursors: azomethane, methyl iodide, and ethane. The spectral shape and intensity of the broadband B2A1′←X2A2″CH3 absorption feature from 211.5 to 220nm at

ABSTRACT A global reduced model for the autoignition of conventional petroleum-derived and altern... more ABSTRACT A global reduced model for the autoignition of conventional petroleum-derived and alternative, hydroprocessed and Fischer–Tropsch, jet and diesel fuels is presented. The model is based on a seven-step model from the literature (Zheng, J.; Miller, D. L.; Cernansky, N. P. A Global Reaction Model for the HCCI Combustion Process, SAE Paper 2004-01-2950, 2004) and includes steps to predict oxidation and autoignition in the three temperature regimes of interest to engine applications, the high-, low-, and negative-temperature-coefficient (NTC) regimes. Here we have included dependence of reaction rate parameters on the derived cetane number (DCN) to predict the influence of fuel variability on autoignition and optimized the reduced model to best fit target shock tube ignition delay time data for jet and diesel fuels. The standard deviation between model predictions for ignition delay and the target shock tube data set is ±21% and the model captures all experimental trends for ignition delay variation with DCN, temperature, pressure, and fuel–air equivalence ratio in all temperature regimes. Comparisons to experimental ignition delay time data not contained in the target data set show model–experiment deviation similar to the comparisons with the target data, with global standard deviation of ±20–30% and differences of at most a factor of 2. The model comparisons with shock tube data suggest that the model is suitable for autoignition prediction for fuels containing large quantities of aliphatic compounds with DCN = 30–80 for 650–1300 K, 8–80 atm, and fuel–air equivalence ratios of 0.25–1.5.

ABSTRACT Measurements of ignition delay, CO and NO emissions, and fuel consumption were carried o... more ABSTRACT Measurements of ignition delay, CO and NO emissions, and fuel consumption were carried out in a light-duty single-cylinder direct-injection diesel engine for operation with petroleum and alternative hydroprocessed and Fischer–Tropsch diesel and jet fuels. Ignition measurements carried out for a fixed engine speed and injection timing quantify the decrease in in-cylinder ignition delay with increasing derived cetane number (DCN) over a range of DCN relevant to diesel engine operation (DCN = 40–80) and show no discernible dependence of ignition delay on other fuel properties. Brake specific fuel consumption (BSFC) was found to decrease with increasing DCN with strong correlation due to a reduction in ignition time for fixed-injection-timed operation. Brake specific CO emissions were also found to decrease with increasing DCN due to increased time provided for CO burn out due to earlier ignition. Brake specific NO emissions were found to decrease with increasing hydrogen-to-carbon (H/C) ratio, due to the lower peak combustion temperatures and thermal NOx occurring for fuels with higher H/C.

ABSTRACT Nanofluids, stable colloidal suspensions of nanoparticles in a base fluid, have potentia... more ABSTRACT Nanofluids, stable colloidal suspensions of nanoparticles in a base fluid, have potential applications in the heat transfer, combustion and propulsion, manufacturing, and medical fields. Experiments were conducted to determine the evaporation rate of room temperature, millimeter-sized pendant droplets of ethanol laden with varying amounts (0–3% by weight) of 40–60 nm aluminum nanoparticles (nAl). Time-resolved high-resolution droplet images were collected for the determination of early-time evaporation rate (D 2/D02 > 0.75), shown to exhibit D-square law behavior, and surface tension. Results show an asymptotic decrease in droplet evaporation rate with increasing nAl loading. The evaporation rate decreases by approximately 15% at around 1–3% nAl loading relative to the evaporation rate of pure ethanol. Surface tension was observed to be unaffected by nAl loading up to 3% by weight. A model was developed to describe the evaporation of the nanofluid pendant droplets based on D-square law analysis for the gas domain and a description of the reduction in liquid fraction available for evaporation due to nanoparticle agglomerate packing near the evaporating droplet surface. Model predictions are in relatively good agreement with experiment, within a few percent of measured nanofluid evaporation rate.

Combustion and Flame, 2006

The reaction of toluene with molecular oxygen to yield benzyl and hydroperoxyl radicals has been ... more The reaction of toluene with molecular oxygen to yield benzyl and hydroperoxyl radicals has been studied using ultraviolet laser absorption of benzyl radicals at 266 nm in shock-heated gases. Test gas mixtures of toluene with excess oxygen diluted in helium and argon were heated in reflected shock waves to temperatures ranging from 1117 to 1366 K at total pressures around 1.7 bar. The growth in benzyl absorbance was monitored at 266 nm, allowing determination of the rate coefficient for the C 6 H 5 CH 3 + O 2 → C 6 H 5 CH 2 + HO 2 , reaction (1). The high signalto-noise ratio provided by laser absorption provides rate coefficient determinations with an estimated uncertainty of ±20%. Fitting both these high-temperature shock tube results and the rate recommendation of Ingham et al. [Proc. Combust. Inst. 25 (1994) 767-774] at 773 K, the rate coefficient for reaction (1) can be described with a three-parameter Arrhenius expression by k 1 (T ) = 2.18 × 10 7 T 2.5 exp(−46,045 [cal/mol]/RT ) [cm 3 mol −1 s −1 ]. In addition, the measured benzyl time-histories can be used as experimental targets for the development and validation of detailed mechanisms for toluene oxidation.

The ignition of methylcyclohexane (MCH)/air and ethylcyclohexane (ECH)/air mix- tures has been st... more The ignition of methylcyclohexane (MCH)/air and ethylcyclohexane (ECH)/air mix- tures has been studied in a shock tube at temperatures and pressures ranging from 881 to 1319 K and 10.8 to 69.5 atm, respectively, for equivalence ratios of 0.25, 0.5, and 1.0. Endwall OH* emission and sidewall pressure measurements were used to determine ignition delay times. The influence of temperature, pressure,

37th Joint Propulsion Conference and Exhibit, 2001

Butanol, an alcohol which can be produced from biomass sources, has received recent interest as a... more Butanol, an alcohol which can be produced from biomass sources, has received recent interest as an alternative to gasoline for use in spark ignition engines and as a possible blending compound with fossil diesel or biodiesel. Therefore, the autoignition of the four isomers of butanol (1-butanol, 2-butanol, iso-butanol, and tert-butanol) has been experimentally studied at high temperatures in a shock

Volume 2: Heat Transfer Enhancement for Practical Applications; Heat and Mass Transfer in Fire and Combustion; Heat Transfer in Multiphase Systems; Heat and Mass Transfer in Biotechnology, 2013

ABSTRACT The autoignition of fatty-acid methyl ester biodiesels and methyl ester biodiesel compon... more ABSTRACT The autoignition of fatty-acid methyl ester biodiesels and methyl ester biodiesel components was studied in gas-phase shock tube experiments. Ignition delay times for two reference methyl ester biodiesel fuels, derived from methanol-based transesterification of soybean oil and animal fats, and four primary constituents of all methyl ester biodiesels, methyl palmitate, methyl stearate, methyl oleate, and methyl linoleate, were measured behind reflected shock waves for fuel/air mixtures at temperatures ranging from 900 to 1350 K and at pressures around 10 and 20 atm. Ignition delay times were determined by monitoring pressure and chemiluminescence from electronically-excited OH radicals around 310 nm. The results show similarity in ignition delay times for all methyl ester fuels considered, irrespective of the variations in organic structure, at the high-temperature conditions studied and also similarity in high-temperature ignition delay times for methyl esters and n-alkanes.

Journal of Thermal Science and Engineering Applications, 2013

Biofuels have the potential to be sustainable, secure, low carbon footprint transportation fuels.... more Biofuels have the potential to be sustainable, secure, low carbon footprint transportation fuels. Primarily due to government mandates, biofuels have become increasingly adopted as transportation fuels over the last decade and are projected to steadily increase in production. Here the prospects of biofuels are summarized in terms of several important performance measures, including: lifecycle greenhouse gas (GHG) emissions, energy return on investment (EROI), land and water requirements, and tailpipe emissions. A review of the literature leads to the conclusion that most first-generation biofuels, including corn ethanol and soybean biodiesel produced in the United States, reduce tailpipe pollutant emissions and GHG emissions-provided their feedstocks do not replace large quantities of fixed carbon. However, their production is perhaps unsustainable due to low EROI and significant land-use and water requirements. Second-generation biofuels; for example ethanol produced from lignocellulosic biomass, have the potential for larger reductions in GHG emissions and can provide sustainable EROI with reasonable land area usage; however, they require water inputs several orders-of-magnitude greater than required by petroleum fuels. Advanced biofuels from algal oils and synthetic biological processes are further from commercial reality and require more assessment but potentially offer better performance due to their orders-of-magnitude greater yields per land area and lower water requirements; at present, the energy costs of such biofuels are uncertain.

Proceedings of the Combustion Institute, 2009

... Permissions & Reprints. A shock tube study of the auto-ignition of toluene/air mi... more ... Permissions & Reprints. A shock tube study of the auto-ignition of toluene/air mixtures at high pressures. Hsi-Ping S. Shen a , Jeremy Vanderover a and Matthew A. Oehlschlaeger Corresponding Author Contact Information , a , E-mail The Corresponding Author. ...

Volume 1: Heat Transfer in Energy Systems; Thermophysical Properties; Theory and Fundamental Research in Heat Transfer, 2013

ABSTRACT Nanofluids, stable colloidal suspensions of nanoparticles in a base fluid, have potentia... more ABSTRACT Nanofluids, stable colloidal suspensions of nanoparticles in a base fluid, have potential applications in the heat transfer, combustion and propulsion, manufacturing, and medical fields. Experiments were conducted to determine the evaporation rate of room temperature, millimeter-sized pendant droplets of ethanol laden with varying (0–3%) weight percentages of 40–60 nm aluminum nanoparticles (nAl). High-resolution droplet images were collected as a function of time for the determination of D-square law evaporation rates. Results show an asymptotic decrease in droplet evaporation rate with increasing nAl loading. The evaporation rate decreases by approximately 15% at around 1% to 3% nAl loading relative to the evaporation rate of pure ethanol, a reduction greater than can be explained by reduction in the vapor pressure of an ideal nanofluid mixture by Raoult’s law. It is hypothesized that the reduction in evaporation rate could be due to two phenomena: 1) the reduction in the ethanol volume fraction available for evaporation due to an interfacial layer on the immersed nanoparticle surface and 2) the aggregation of nanoparticles within the droplet and at the droplet surface, reducing the liquid diffusion rate to the surface and the liquid volume fraction at the surface available for evaporation.

Propellants, Explosives, Pyrotechnics, 2014

50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2012

Journal of Quantitative Spectroscopy & Radiative Transfer, 2005

The absorption of ultraviolet narrow-line laser radiation by methyl radicals (CH3) in the B2A1′←X... more The absorption of ultraviolet narrow-line laser radiation by methyl radicals (CH3) in the B2A1′←X2A2″ electronic system has been studied at high temperatures behind shock waves. Methyl radicals at high temperatures were generated by the shock heating of methyl precursors: azomethane, methyl iodide, and ethane. The spectral shape and intensity of the broadband B2A1′←X2A2″CH3 absorption feature from 211.5 to 220nm at

ABSTRACT A global reduced model for the autoignition of conventional petroleum-derived and altern... more ABSTRACT A global reduced model for the autoignition of conventional petroleum-derived and alternative, hydroprocessed and Fischer–Tropsch, jet and diesel fuels is presented. The model is based on a seven-step model from the literature (Zheng, J.; Miller, D. L.; Cernansky, N. P. A Global Reaction Model for the HCCI Combustion Process, SAE Paper 2004-01-2950, 2004) and includes steps to predict oxidation and autoignition in the three temperature regimes of interest to engine applications, the high-, low-, and negative-temperature-coefficient (NTC) regimes. Here we have included dependence of reaction rate parameters on the derived cetane number (DCN) to predict the influence of fuel variability on autoignition and optimized the reduced model to best fit target shock tube ignition delay time data for jet and diesel fuels. The standard deviation between model predictions for ignition delay and the target shock tube data set is ±21% and the model captures all experimental trends for ignition delay variation with DCN, temperature, pressure, and fuel–air equivalence ratio in all temperature regimes. Comparisons to experimental ignition delay time data not contained in the target data set show model–experiment deviation similar to the comparisons with the target data, with global standard deviation of ±20–30% and differences of at most a factor of 2. The model comparisons with shock tube data suggest that the model is suitable for autoignition prediction for fuels containing large quantities of aliphatic compounds with DCN = 30–80 for 650–1300 K, 8–80 atm, and fuel–air equivalence ratios of 0.25–1.5.

ABSTRACT Measurements of ignition delay, CO and NO emissions, and fuel consumption were carried o... more ABSTRACT Measurements of ignition delay, CO and NO emissions, and fuel consumption were carried out in a light-duty single-cylinder direct-injection diesel engine for operation with petroleum and alternative hydroprocessed and Fischer–Tropsch diesel and jet fuels. Ignition measurements carried out for a fixed engine speed and injection timing quantify the decrease in in-cylinder ignition delay with increasing derived cetane number (DCN) over a range of DCN relevant to diesel engine operation (DCN = 40–80) and show no discernible dependence of ignition delay on other fuel properties. Brake specific fuel consumption (BSFC) was found to decrease with increasing DCN with strong correlation due to a reduction in ignition time for fixed-injection-timed operation. Brake specific CO emissions were also found to decrease with increasing DCN due to increased time provided for CO burn out due to earlier ignition. Brake specific NO emissions were found to decrease with increasing hydrogen-to-carbon (H/C) ratio, due to the lower peak combustion temperatures and thermal NOx occurring for fuels with higher H/C.

ABSTRACT Nanofluids, stable colloidal suspensions of nanoparticles in a base fluid, have potentia... more ABSTRACT Nanofluids, stable colloidal suspensions of nanoparticles in a base fluid, have potential applications in the heat transfer, combustion and propulsion, manufacturing, and medical fields. Experiments were conducted to determine the evaporation rate of room temperature, millimeter-sized pendant droplets of ethanol laden with varying amounts (0–3% by weight) of 40–60 nm aluminum nanoparticles (nAl). Time-resolved high-resolution droplet images were collected for the determination of early-time evaporation rate (D 2/D02 > 0.75), shown to exhibit D-square law behavior, and surface tension. Results show an asymptotic decrease in droplet evaporation rate with increasing nAl loading. The evaporation rate decreases by approximately 15% at around 1–3% nAl loading relative to the evaporation rate of pure ethanol. Surface tension was observed to be unaffected by nAl loading up to 3% by weight. A model was developed to describe the evaporation of the nanofluid pendant droplets based on D-square law analysis for the gas domain and a description of the reduction in liquid fraction available for evaporation due to nanoparticle agglomerate packing near the evaporating droplet surface. Model predictions are in relatively good agreement with experiment, within a few percent of measured nanofluid evaporation rate.