M. Fikri - Academia.edu (original) (raw)

Papers by M. Fikri

Research paper thumbnail of Spiking of Hydrocarbon Fuels with Silanes-based Combustion Enhancers

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN, 2010

The concept of spiking hydrocarbon fuels such as kerosenes with liquid silicon hydrides in order ... more The concept of spiking hydrocarbon fuels such as kerosenes with liquid silicon hydrides in order to render the fuel combination hypergolic and to improve the combustion efficiency is presented and preliminarily analyzed. In view of scarcity of available data, various approaches are used, among them quantum-mechanical ab initio calculations for the thermodynamics and shock-tube measurements for the kinetics of higher, liquid silanes. Based on these results and other data, performance predictions indicate that miscible hydrocarbon/silicon hydride fuels (HC/SH) have the potential to be stored in a single tank, to be hypergolic with many oxidizers, and to yield similar, partly better specific impulses (and volume-specific impulses) than hydrocarbon fuels without silane additives. A variety of hybrid HC/SH fuel combinations seems to be accessible, which might offer the possibility to design a fuel combination with characteristics adjustable in a wide range. The current and future availability of larger amounts of liquid silanes is discussed.

Research paper thumbnail of Methodology for the investigation of ignition near hot surfaces in a high-pressure shock tube

Review of Scientific Instruments, 2018

Research paper thumbnail of A single-pulse shock tube coupled with high-repetition-rate time-of-flight mass spectrometry and gas chromatography for high-temperature gas-phase kinetics studies

The Review of scientific instruments, 2016

Shock tubes are frequently used to investigate the kinetics of chemical reactions in the gas phas... more Shock tubes are frequently used to investigate the kinetics of chemical reactions in the gas phase at high temperatures. Conventionally, two complementary arrangements are used where either time-resolved intermediate species measurements are conducted after the initiation of the reaction or where the product composition is determined after rapid initiation and quenching of the reaction through gas-dynamic processes. This paper presents a facility that combines both approaches to determine comprehensive information. A single-pulse shock tube is combined with high-sensitivity gas chromatography/mass spectrometry for product composition and concentration measurement as well as high-repetition-rate time-of-flight mass spectrometry for time-dependent intermediate concentration determination with 10 μs time resolution. Both methods can be applied simultaneously. The arrangement is validated with investigations of the well-documented thermal unimolecular decomposition of cyclohexene toward...

Research paper thumbnail of Experimental study of the kinetics of ethanol pyrolysis and oxidation behind reflected shock waves and in laminar flames

Proceedings of the Combustion Institute, 2015

ABSTRACT The pyrolysis and oxidation of ethanol mixtures at high temperature is studied in a shoc... more ABSTRACT The pyrolysis and oxidation of ethanol mixtures at high temperature is studied in a shock tube in the 1047-2518 K range at initial pressures of 1.06 and 2.07 bar. Pyrolysis and oxidation intermediates were investigated with high-repetition-rate time-of-flight mass spectrometry (TOF-MS). Ignition delay times were determined from chemiluminescence measurements and the OH concentration was determined with high time resolution from ring dye laser absorption measurements. Laminar flame speeds of ethanol in air were measured in a spherical bomb for initial temperatures between 318 and 473 K at 1, 2, and 5 bar and for equivalence ratios from 0.7 to 1.5. The measurements were compared to simulations based on various mechanisms from the literature. This comparison showed that the mechanism developed by Ranzi et al. (2012) provides the best agreement with the measured data for ethanol oxidation at high temperature.

Research paper thumbnail of The autoignition of practical fuels at HCCI conditions: High-pressure shock tube experiments and phenomenological modeling

Research paper thumbnail of Ignition delay times of ethanol-containing multi-component gasoline surrogates: Shock-tube experiments and detailed modeling

Research paper thumbnail of Zeitaufgelöste Cavity-Ringdown-Messungen der Druckabhängigkeit der Reaktionen von SiH 2-Radikalen mit O 2 und den Alkenen C 2 H 4, C 3 H 6 und trans-C 4 H 8

... der Christian–Albrechts–Universität zu Kiel vorgelegt von Mustapha Fikri Kiel 2004 Page 2. 2 ... more ... der Christian–Albrechts–Universität zu Kiel vorgelegt von Mustapha Fikri Kiel 2004 Page 2. 2 ... ßend die Druckabhängigkeit der Reaktionen von SiH2 mit ungesättigten Kohlenwasser-stoffen (Ethen, Propen und trans-Buten) untersucht. Die experimentellen Fall-Off-Kurven ...

Research paper thumbnail of Autoignition of surrogate biodiesel fuel (B30) at high pressures: Experimental and modeling kinetic study

Combustion and Flame, 2012

Ignition delay times of surrogate biodiesel fuels were measured in a high-pressure shock tube ove... more Ignition delay times of surrogate biodiesel fuels were measured in a high-pressure shock tube over a wide range of experimental conditions (pressures of 20 and 40 bar, equivalence ratios in the range 0.5-1.5, and temperatures ranging from 700 to 1200 K). A detailed chemical kinetic mechanism developed for the oxidation of a biodiesel fuel and a B30 biodiesel surrogate (49% n-decane, 21% 1-methylnaphthalene, and 30% methyloctanoate in mol%) was used to simulate the present experiments. Cross reactions between radicals from the three fuel components and reactions of methylnaphthalene oxidation recently proposed in the literature were introduced into the model in order to improve ignition delay time predictions at low temperatures. The new scheme (7865 reversible reactions and 1975 species) yields improved model predictions of concentration profiles measured earlier in a jet-stirred reactor, and also represents fairly well the present experimental data over the entire range of conditions of this study. Sensitivity analyses and reaction path analyses were used to rationalize the results.

Research paper thumbnail of Ignition delay times of shock-heated tetraethoxysilane, hexamethyldisiloxane, and titanium tetraisopropoxide

Chemical Physics Letters, 2014

ABSTRACT Ignition delay times of tetraethoxysilane (TEOS), hexamethyldisiloxane (HMDSO) and titan... more ABSTRACT Ignition delay times of tetraethoxysilane (TEOS), hexamethyldisiloxane (HMDSO) and titanium tetraisopropoxide (TTIP) were determined from the onset of chemiluminescence in shock-tube experiments behind reflected shock waves in dry as well as in humid gas mixtures. Additionally, the ignition delay times of TEOS and HMDSO have been investigated in humid air and as a function of water vapor concentration in the initial gas mixture.

Research paper thumbnail of Measurement of the absorption cross sections of SiCl4, SiCl3, SiCl2 and Cl at H Lyman- wavelength

Chemical Physics Letters, 2013

ABSTRACT Atomic resonance absorption spectroscopy coupled with a shock tube is a powerful techniq... more ABSTRACT Atomic resonance absorption spectroscopy coupled with a shock tube is a powerful technique for studying high temperature dynamics of reactive systems. Presently, high temperature pyrolysis of SiCl4–Ar mixtures has been studied behind reflected shock waves. Using time-resolved absorption profiles at 121.6 nm and a detailed reaction model, the absorption cross sections of SiCl4SiCl4, SiCl3SiCl3, SiCl2SiCl2 and Cl have been measured. Results agree well with available data for SiCl4SiCl4 and constitute, to our knowledge, the first measurements for SiCl3SiCl3, SiCl2SiCl2 and Cl at the Lyman-αα wavelength. These data are relevant to silica particle production from SiCl4SiCl4-oxidant mixtures combustion synthesis.

Research paper thumbnail of Investigation of the kinetics of OH∗ and CH∗ chemiluminescence in hydrocarbon oxidation behind reflected shock waves

Applied Physics B, 2012

The temporal variation of chemiluminescence emission from OH * (A 2 Σ +) and CH * (A 2 Δ) in reac... more The temporal variation of chemiluminescence emission from OH * (A 2 Σ +) and CH * (A 2 Δ) in reacting Ar-diluted H 2 /O 2 /CH 4 , C 2 H 2 /O 2 and C 2 H 2 /N 2 O mixtures was studied in a shock tube for a wide temperature range at atmospheric pressures and various equivalence ratios. Time-resolved emission measurements were used to evaluate the relative importance of different reaction pathways. The main formation channel for OH * in hydrocarbon combustion was studied with CH 4 as benchmark fuel. Three reaction pathways leading to CH * were studied with C 2 H 2 as fuel. Based on well-validated groundstate chemistry models from literature, sub-mechanisms for OH * and CH * were developed. For the main OH *forming reaction CH + O 2 = OH * + CO, a rate coefficient of k 2 = (8.0 ± 2.6) × 10 10 cm 3 mol −1 s −1 was determined. For CH * formation, best agreement was achieved when incorporating reactions C 2 + OH = CH * + CO (k 5 = 2.0 × 10 14 cm 3 mol −1 s −1) and C 2 H + O = CH * + CO (k 6 = 3.6 × 10 12 exp(−10.9 kJ mol −1 /RT) cm 3 mol −1 s −1) and neglecting the C 2 H + O 2 = CH * + CO 2 reaction. 1 Introduction Spontaneous light emission from chemically excited species in combustion processes is frequently used for detecting

Research paper thumbnail of Study of the H+O+M reaction forming OH∗: Kinetics of OH∗ chemiluminescence in hydrogen combustion systems

Combustion and Flame, 2010

The temporal variation of OH* (A 2  +) chemiluminescence in hydrogen oxidation chemistry has bee... more The temporal variation of OH* (A 2  +) chemiluminescence in hydrogen oxidation chemistry has been studied in a shock tube behind reflected shock waves at temperatures of 1400-3300 K and at a pressure of 1 bar. The aim of the present work is to obtain a validated reaction scheme to describe OH* formation in the H 2 /O 2 system. Temporal OH* emission profiles and ignition delay times for lean and stoichiometric H 2 /O 2 mixtures diluted in 97-98% argon were obtained from the shock-tube experiments. Based on a literature review for the hydrogen combustion system, the key reaction considered was H + O + M = OH* + M (R1). The temperature dependence of the measured peak OH* emission from the shock-tube and the peak OH* concentration from a homogeneous closed reactor model are compared. Based on these results a reaction rate coefficient of k 1 = (1.5±0.4)×10 13 exp(-25 kJmol −1 /RT) cm 6 mol-2 s-1 was found for the forward reaction (R1) which is slightly higher than the rate coefficient suggested by Hidaka et al. (1982).The comparison of measured and simulated absolute concentrations shows good agreement. Additionally, a one-dimensional laminar premixed low-pressure flame calculation was performed for where absolute OH* concentration measurements have been reported by Smith et al. (2005). The absolute peak OH* concentration is fairly well reproduced if the above mentioned

Research paper thumbnail of Plug-flow reactor and shock-tube study of the oxidation of very fuel-rich natural gas/DME/O2 mixtures

Research paper thumbnail of Reaction-time-resolved measurements of laser-induced fluorescence in a shock tube with a single laser pulse

Review of Scientific Instruments

Research paper thumbnail of High-temperature gas-phase kinetics of the thermal decomposition of tetramethoxysilane

Proceedings of the Combustion Institute

Research paper thumbnail of Shock-tube study of methane pyrolysis in the context of energy-storage processes

Proceedings of the Combustion Institute

Research paper thumbnail of Experimental and numerical investigation of OH * chemiluminescence in shock tubes: Reactions of highly diluted H 2/O 2 mixtures with various diluents

The temporal variation of OH * chemiluminescence in hydrogen oxidation chemistry has been studied... more The temporal variation of OH * chemiluminescence in hydrogen oxidation chemistry has been studied behind re- flected shock waves at temperatures of 1100-3000 K, at a pressure of 1 bar. The aim of the present wor k was to obtain a validated reaction scheme to describe OH * formation. The main pathway of OH * formation in hydrogen oxidation at

Research paper thumbnail of Ignition delay times of diethyl ether measured in a high-pressure shock tube and a rapid compression machine

Proceedings of the Combustion Institute, 2015

ABSTRACT Ignition delay times of diethyl ether (DEE)/air/argon mixtures were studied in a shock t... more ABSTRACT Ignition delay times of diethyl ether (DEE)/air/argon mixtures were studied in a shock tube in the temperature range from 900 to 1300 K at pressures of 10, 20, and 40 bar and in a rapid compression machine (RCM) at various equivalence ratios between 500 and 1060 K at pressures between 2.5 and 13 bar. Between 2.5 and 5.5 bar, the RCM results show that ignition delay times of DEE exhibit a region (between 590 and 800 K) where ignition delay times are weakly temperature dependent only, while above 833 K and below 590 K, the ignition delay times are strongly temperature dependent. Two-stage ignition was observed in the temperature range from 500 to 665 K in the RCM measurements. At the conditions of the shock tube, a strong pressure and temperature dependence of the ignition delay times was observed, but no non-thermal (NTC) behavior was found in the investigated temperature range. Simulations based on detailed chemistry using the mechanism of Yasunaga et al. (2010) [15] indicate that at high pressures ignition delay times show a high sensitivity towards the two H-atom abstraction reactions by HO2 from diethyl ether. By increasing the rate coefficients of these two reactions relative to the original values by a factor of five, the mechanism well describes our measurements and still well reproduces the original data of Yasunaga et al. (2010) [15].

Research paper thumbnail of Discrepancies between shock-tube and rapid compression machine ignition at low temperatures and high pressures

Shock Waves, Vol 1, Proceedings, 2009

Ignition delay time data at elevated pressures and low-to-intermediate temperatures continue to b... more Ignition delay time data at elevated pressures and low-to-intermediate temperatures continue to be of interest because of their importance for the validation of chemical kinetics models at practical engine conditions. However, it has been noticed recently that shock-tube ignition data can disagree significantly with rapid compression machine (RCM) data at higher pressures and temperatures below about 1100 K. The basic trend is that the ignition delay times obtained from shock-tube experiments are faster than model predictions and data obtained in RCM’s over this lower-temperature region, sometimes by an order of magnitude or more.

Research paper thumbnail of Experimental investigation and modeling of the kinetics of CCl4 pyrolysis behind reflected shock waves using high-repetition-rate time-of-flight mass spectrometry

Physical Chemistry Chemical Physics, 2013

The pyrolysis kinetics of CCl 4 behind reflected shock waves was studied with high-repetition-rat... more The pyrolysis kinetics of CCl 4 behind reflected shock waves was studied with high-repetition-rate timeof-flight mass spectrometry. For modeling, quantum mechanical calculations were performed to evaluate the dissociation energies of CCl bonds for the different CCl x (x = 1 to 4) radicals. Good agreement with the JANAF thermochemical table was found. With the reaction mechanism developed for CCl 4 decomposition satisfactory agreement with experimental results was obtained. The investigations show the importance of C 2 Cl 2 formation for understanding the processes of carbon cluster growth leading to carbonaceous particle formation.

Research paper thumbnail of Spiking of Hydrocarbon Fuels with Silanes-based Combustion Enhancers

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN, 2010

The concept of spiking hydrocarbon fuels such as kerosenes with liquid silicon hydrides in order ... more The concept of spiking hydrocarbon fuels such as kerosenes with liquid silicon hydrides in order to render the fuel combination hypergolic and to improve the combustion efficiency is presented and preliminarily analyzed. In view of scarcity of available data, various approaches are used, among them quantum-mechanical ab initio calculations for the thermodynamics and shock-tube measurements for the kinetics of higher, liquid silanes. Based on these results and other data, performance predictions indicate that miscible hydrocarbon/silicon hydride fuels (HC/SH) have the potential to be stored in a single tank, to be hypergolic with many oxidizers, and to yield similar, partly better specific impulses (and volume-specific impulses) than hydrocarbon fuels without silane additives. A variety of hybrid HC/SH fuel combinations seems to be accessible, which might offer the possibility to design a fuel combination with characteristics adjustable in a wide range. The current and future availability of larger amounts of liquid silanes is discussed.

Research paper thumbnail of Methodology for the investigation of ignition near hot surfaces in a high-pressure shock tube

Review of Scientific Instruments, 2018

Research paper thumbnail of A single-pulse shock tube coupled with high-repetition-rate time-of-flight mass spectrometry and gas chromatography for high-temperature gas-phase kinetics studies

The Review of scientific instruments, 2016

Shock tubes are frequently used to investigate the kinetics of chemical reactions in the gas phas... more Shock tubes are frequently used to investigate the kinetics of chemical reactions in the gas phase at high temperatures. Conventionally, two complementary arrangements are used where either time-resolved intermediate species measurements are conducted after the initiation of the reaction or where the product composition is determined after rapid initiation and quenching of the reaction through gas-dynamic processes. This paper presents a facility that combines both approaches to determine comprehensive information. A single-pulse shock tube is combined with high-sensitivity gas chromatography/mass spectrometry for product composition and concentration measurement as well as high-repetition-rate time-of-flight mass spectrometry for time-dependent intermediate concentration determination with 10 μs time resolution. Both methods can be applied simultaneously. The arrangement is validated with investigations of the well-documented thermal unimolecular decomposition of cyclohexene toward...

Research paper thumbnail of Experimental study of the kinetics of ethanol pyrolysis and oxidation behind reflected shock waves and in laminar flames

Proceedings of the Combustion Institute, 2015

ABSTRACT The pyrolysis and oxidation of ethanol mixtures at high temperature is studied in a shoc... more ABSTRACT The pyrolysis and oxidation of ethanol mixtures at high temperature is studied in a shock tube in the 1047-2518 K range at initial pressures of 1.06 and 2.07 bar. Pyrolysis and oxidation intermediates were investigated with high-repetition-rate time-of-flight mass spectrometry (TOF-MS). Ignition delay times were determined from chemiluminescence measurements and the OH concentration was determined with high time resolution from ring dye laser absorption measurements. Laminar flame speeds of ethanol in air were measured in a spherical bomb for initial temperatures between 318 and 473 K at 1, 2, and 5 bar and for equivalence ratios from 0.7 to 1.5. The measurements were compared to simulations based on various mechanisms from the literature. This comparison showed that the mechanism developed by Ranzi et al. (2012) provides the best agreement with the measured data for ethanol oxidation at high temperature.

Research paper thumbnail of The autoignition of practical fuels at HCCI conditions: High-pressure shock tube experiments and phenomenological modeling

Research paper thumbnail of Ignition delay times of ethanol-containing multi-component gasoline surrogates: Shock-tube experiments and detailed modeling

Research paper thumbnail of Zeitaufgelöste Cavity-Ringdown-Messungen der Druckabhängigkeit der Reaktionen von SiH 2-Radikalen mit O 2 und den Alkenen C 2 H 4, C 3 H 6 und trans-C 4 H 8

... der Christian–Albrechts–Universität zu Kiel vorgelegt von Mustapha Fikri Kiel 2004 Page 2. 2 ... more ... der Christian–Albrechts–Universität zu Kiel vorgelegt von Mustapha Fikri Kiel 2004 Page 2. 2 ... ßend die Druckabhängigkeit der Reaktionen von SiH2 mit ungesättigten Kohlenwasser-stoffen (Ethen, Propen und trans-Buten) untersucht. Die experimentellen Fall-Off-Kurven ...

Research paper thumbnail of Autoignition of surrogate biodiesel fuel (B30) at high pressures: Experimental and modeling kinetic study

Combustion and Flame, 2012

Ignition delay times of surrogate biodiesel fuels were measured in a high-pressure shock tube ove... more Ignition delay times of surrogate biodiesel fuels were measured in a high-pressure shock tube over a wide range of experimental conditions (pressures of 20 and 40 bar, equivalence ratios in the range 0.5-1.5, and temperatures ranging from 700 to 1200 K). A detailed chemical kinetic mechanism developed for the oxidation of a biodiesel fuel and a B30 biodiesel surrogate (49% n-decane, 21% 1-methylnaphthalene, and 30% methyloctanoate in mol%) was used to simulate the present experiments. Cross reactions between radicals from the three fuel components and reactions of methylnaphthalene oxidation recently proposed in the literature were introduced into the model in order to improve ignition delay time predictions at low temperatures. The new scheme (7865 reversible reactions and 1975 species) yields improved model predictions of concentration profiles measured earlier in a jet-stirred reactor, and also represents fairly well the present experimental data over the entire range of conditions of this study. Sensitivity analyses and reaction path analyses were used to rationalize the results.

Research paper thumbnail of Ignition delay times of shock-heated tetraethoxysilane, hexamethyldisiloxane, and titanium tetraisopropoxide

Chemical Physics Letters, 2014

ABSTRACT Ignition delay times of tetraethoxysilane (TEOS), hexamethyldisiloxane (HMDSO) and titan... more ABSTRACT Ignition delay times of tetraethoxysilane (TEOS), hexamethyldisiloxane (HMDSO) and titanium tetraisopropoxide (TTIP) were determined from the onset of chemiluminescence in shock-tube experiments behind reflected shock waves in dry as well as in humid gas mixtures. Additionally, the ignition delay times of TEOS and HMDSO have been investigated in humid air and as a function of water vapor concentration in the initial gas mixture.

Research paper thumbnail of Measurement of the absorption cross sections of SiCl4, SiCl3, SiCl2 and Cl at H Lyman- wavelength

Chemical Physics Letters, 2013

ABSTRACT Atomic resonance absorption spectroscopy coupled with a shock tube is a powerful techniq... more ABSTRACT Atomic resonance absorption spectroscopy coupled with a shock tube is a powerful technique for studying high temperature dynamics of reactive systems. Presently, high temperature pyrolysis of SiCl4–Ar mixtures has been studied behind reflected shock waves. Using time-resolved absorption profiles at 121.6 nm and a detailed reaction model, the absorption cross sections of SiCl4SiCl4, SiCl3SiCl3, SiCl2SiCl2 and Cl have been measured. Results agree well with available data for SiCl4SiCl4 and constitute, to our knowledge, the first measurements for SiCl3SiCl3, SiCl2SiCl2 and Cl at the Lyman-αα wavelength. These data are relevant to silica particle production from SiCl4SiCl4-oxidant mixtures combustion synthesis.

Research paper thumbnail of Investigation of the kinetics of OH∗ and CH∗ chemiluminescence in hydrocarbon oxidation behind reflected shock waves

Applied Physics B, 2012

The temporal variation of chemiluminescence emission from OH * (A 2 Σ +) and CH * (A 2 Δ) in reac... more The temporal variation of chemiluminescence emission from OH * (A 2 Σ +) and CH * (A 2 Δ) in reacting Ar-diluted H 2 /O 2 /CH 4 , C 2 H 2 /O 2 and C 2 H 2 /N 2 O mixtures was studied in a shock tube for a wide temperature range at atmospheric pressures and various equivalence ratios. Time-resolved emission measurements were used to evaluate the relative importance of different reaction pathways. The main formation channel for OH * in hydrocarbon combustion was studied with CH 4 as benchmark fuel. Three reaction pathways leading to CH * were studied with C 2 H 2 as fuel. Based on well-validated groundstate chemistry models from literature, sub-mechanisms for OH * and CH * were developed. For the main OH *forming reaction CH + O 2 = OH * + CO, a rate coefficient of k 2 = (8.0 ± 2.6) × 10 10 cm 3 mol −1 s −1 was determined. For CH * formation, best agreement was achieved when incorporating reactions C 2 + OH = CH * + CO (k 5 = 2.0 × 10 14 cm 3 mol −1 s −1) and C 2 H + O = CH * + CO (k 6 = 3.6 × 10 12 exp(−10.9 kJ mol −1 /RT) cm 3 mol −1 s −1) and neglecting the C 2 H + O 2 = CH * + CO 2 reaction. 1 Introduction Spontaneous light emission from chemically excited species in combustion processes is frequently used for detecting

Research paper thumbnail of Study of the H+O+M reaction forming OH∗: Kinetics of OH∗ chemiluminescence in hydrogen combustion systems

Combustion and Flame, 2010

The temporal variation of OH* (A 2  +) chemiluminescence in hydrogen oxidation chemistry has bee... more The temporal variation of OH* (A 2  +) chemiluminescence in hydrogen oxidation chemistry has been studied in a shock tube behind reflected shock waves at temperatures of 1400-3300 K and at a pressure of 1 bar. The aim of the present work is to obtain a validated reaction scheme to describe OH* formation in the H 2 /O 2 system. Temporal OH* emission profiles and ignition delay times for lean and stoichiometric H 2 /O 2 mixtures diluted in 97-98% argon were obtained from the shock-tube experiments. Based on a literature review for the hydrogen combustion system, the key reaction considered was H + O + M = OH* + M (R1). The temperature dependence of the measured peak OH* emission from the shock-tube and the peak OH* concentration from a homogeneous closed reactor model are compared. Based on these results a reaction rate coefficient of k 1 = (1.5±0.4)×10 13 exp(-25 kJmol −1 /RT) cm 6 mol-2 s-1 was found for the forward reaction (R1) which is slightly higher than the rate coefficient suggested by Hidaka et al. (1982).The comparison of measured and simulated absolute concentrations shows good agreement. Additionally, a one-dimensional laminar premixed low-pressure flame calculation was performed for where absolute OH* concentration measurements have been reported by Smith et al. (2005). The absolute peak OH* concentration is fairly well reproduced if the above mentioned

Research paper thumbnail of Plug-flow reactor and shock-tube study of the oxidation of very fuel-rich natural gas/DME/O2 mixtures

Research paper thumbnail of Reaction-time-resolved measurements of laser-induced fluorescence in a shock tube with a single laser pulse

Review of Scientific Instruments

Research paper thumbnail of High-temperature gas-phase kinetics of the thermal decomposition of tetramethoxysilane

Proceedings of the Combustion Institute

Research paper thumbnail of Shock-tube study of methane pyrolysis in the context of energy-storage processes

Proceedings of the Combustion Institute

Research paper thumbnail of Experimental and numerical investigation of OH * chemiluminescence in shock tubes: Reactions of highly diluted H 2/O 2 mixtures with various diluents

The temporal variation of OH * chemiluminescence in hydrogen oxidation chemistry has been studied... more The temporal variation of OH * chemiluminescence in hydrogen oxidation chemistry has been studied behind re- flected shock waves at temperatures of 1100-3000 K, at a pressure of 1 bar. The aim of the present wor k was to obtain a validated reaction scheme to describe OH * formation. The main pathway of OH * formation in hydrogen oxidation at

Research paper thumbnail of Ignition delay times of diethyl ether measured in a high-pressure shock tube and a rapid compression machine

Proceedings of the Combustion Institute, 2015

ABSTRACT Ignition delay times of diethyl ether (DEE)/air/argon mixtures were studied in a shock t... more ABSTRACT Ignition delay times of diethyl ether (DEE)/air/argon mixtures were studied in a shock tube in the temperature range from 900 to 1300 K at pressures of 10, 20, and 40 bar and in a rapid compression machine (RCM) at various equivalence ratios between 500 and 1060 K at pressures between 2.5 and 13 bar. Between 2.5 and 5.5 bar, the RCM results show that ignition delay times of DEE exhibit a region (between 590 and 800 K) where ignition delay times are weakly temperature dependent only, while above 833 K and below 590 K, the ignition delay times are strongly temperature dependent. Two-stage ignition was observed in the temperature range from 500 to 665 K in the RCM measurements. At the conditions of the shock tube, a strong pressure and temperature dependence of the ignition delay times was observed, but no non-thermal (NTC) behavior was found in the investigated temperature range. Simulations based on detailed chemistry using the mechanism of Yasunaga et al. (2010) [15] indicate that at high pressures ignition delay times show a high sensitivity towards the two H-atom abstraction reactions by HO2 from diethyl ether. By increasing the rate coefficients of these two reactions relative to the original values by a factor of five, the mechanism well describes our measurements and still well reproduces the original data of Yasunaga et al. (2010) [15].

Research paper thumbnail of Discrepancies between shock-tube and rapid compression machine ignition at low temperatures and high pressures

Shock Waves, Vol 1, Proceedings, 2009

Ignition delay time data at elevated pressures and low-to-intermediate temperatures continue to b... more Ignition delay time data at elevated pressures and low-to-intermediate temperatures continue to be of interest because of their importance for the validation of chemical kinetics models at practical engine conditions. However, it has been noticed recently that shock-tube ignition data can disagree significantly with rapid compression machine (RCM) data at higher pressures and temperatures below about 1100 K. The basic trend is that the ignition delay times obtained from shock-tube experiments are faster than model predictions and data obtained in RCM’s over this lower-temperature region, sometimes by an order of magnitude or more.

Research paper thumbnail of Experimental investigation and modeling of the kinetics of CCl4 pyrolysis behind reflected shock waves using high-repetition-rate time-of-flight mass spectrometry

Physical Chemistry Chemical Physics, 2013

The pyrolysis kinetics of CCl 4 behind reflected shock waves was studied with high-repetition-rat... more The pyrolysis kinetics of CCl 4 behind reflected shock waves was studied with high-repetition-rate timeof-flight mass spectrometry. For modeling, quantum mechanical calculations were performed to evaluate the dissociation energies of CCl bonds for the different CCl x (x = 1 to 4) radicals. Good agreement with the JANAF thermochemical table was found. With the reaction mechanism developed for CCl 4 decomposition satisfactory agreement with experimental results was obtained. The investigations show the importance of C 2 Cl 2 formation for understanding the processes of carbon cluster growth leading to carbonaceous particle formation.