M. Fikri - Profile on Academia.edu (original) (raw)
Papers by M. Fikri
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.
Review of Scientific Instruments, 2018
The title cluster compound, [Ru 3 (C 19 H 17 PS)(CO) 11 ], comprises a triangle of Ru 0 atoms, tw... more The title cluster compound, [Ru 3 (C 19 H 17 PS)(CO) 11 ], comprises a triangle of Ru 0 atoms, two of which are bonded to four carbonyl ligands. The third metal atom is bound to three carbonyl ligands and the phosphane-P atom of a dissymmetric phosphane ligand, PPh 2 (C 6 H 4 SMe-4); no RuÁ Á ÁS interactions are observed. The phosphane occupies an equatorial position and its proximity to an Ru-Ru edge results in the elongation of this bond with respect to the others [2.8933 (2) A ˚cf. 2.8575 (2) and 2.8594 (3) A ˚]. In the crystal, phenyl-C-HÁ Á ÁO(carbonyl) and carbonyl-OÁ Á ÁO(carbonyl) [2.817 (2) A ˚] interactions combine to form a supramolecular chain propagating along [111]; the chains pack without directional interactions between them. The carbonyl-OÁ Á ÁO(carbonyl) and other weak contacts have an influence upon the Hirshfeld surfaces with OÁ Á ÁH contacts making the greatest contribution, i.e. 37.4% cf. 15.8% for OÁ Á ÁO and 15.6% for HÁ Á ÁH contacts.
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...
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.
Fuel, 2012
Delay times for first-and second-stage ignition of n-heptane and two practical kerosene-like fuel... more Delay times for first-and second-stage ignition of n-heptane and two practical kerosene-like fuels have been measured in a heated high-pressure shock tube at conditions similar to those found in homogeneous charge compression ignition (HCCI) engines. Initial reflected shock conditions covered temperatures from 700 to 1100 K, pressures from 20 to 65 bar, equivalence ratios of 0.5, 0.67, and 1, and exhaust gas recirculation rates (EGR) of 0%, 30%, and 50%. EGR is simulated by introducing additional N 2 in the test gas mixture. Because detailed chemical kinetics models are not available for practical fuels so far, we propose a global ignition time correlation that is fitted to the measured data. The empirical model describes both first-and second-stage ignition delay as a function of temperature, pressure, equivalence ratio and EGR. It is based on a three-stage Arrhenius approach, which has been extended to capture the first-stage ignition times and the influence of EGR. For each of the fuels, even for the fuels that contain cyclo-alkanes and aromatics, good agreement between model and experiment is observed, especially at lean and high-EGR conditions relevant for HCCI. Based on this extensive set of ignition data, interesting correlations between fuel composition and ignition behavior could be identified, which may prove useful in matching the fuel to the engine application.
Fuel, 2011
Ignition delay times for binary (ethanol/iso-octane, 25%/75% by liquid volume) and quinary (iso-o... more Ignition delay times for binary (ethanol/iso-octane, 25%/75% by liquid volume) and quinary (iso-octane/ toluene/n-heptane/diisobutylene/ethanol, 30%/25%/22%/13%/10%) gasoline surrogate fuels in air were measured under stoichiometric conditions behind reflected shock waves. The investigated post-shock temperature ranges from 720 to 1220 K at pressures of 10 bar for the binary mixture and 10 bar and 30 bar for the quinary mixture. Ignition delay times were evaluated using side-wall detection of CH* chemiluminescence (k = 431.5 nm). Multiple regression analysis of the data indicates global activation energy of 124kJ/molforthebinarymixtureand124 kJ/mol for the binary mixture and 124kJ/molforthebinarymixtureand101 kJ/mol for the quinary mixture and a pressure dependence exponent of À1.0 was obtained for the quinary mixture. The measurements were compared to predictions using a proposed detailed kinetics model for multicomponent mixtures that is based on the reference fuels (PRF) model as a kernel and incorporates sub-mechanisms to account for the chemistry of ethanol, toluene and diisobutylene. The model was tested using the measured ignition delay times for the surrogate fuels. Additional comparisons are based on literature data for other fuel combinations of the single constituents forming the quinary surrogate to insure that the modified mechanism still correctly predicts the behavior of simple fuels. The proposed model reproduces the trend of the experimental data for all pure fuels and blends investigated in this work, including the pressure dependence.
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 ChristianAlbrechtsUniversität zu Kiel vorgelegt von Mustapha Fikri Kiel 2004 Page 2. 2 ... more ... der ChristianAlbrechtsUniversität 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 ...
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.
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.
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.
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
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
Reaction-time-resolved measurements of laser-induced fluorescence in a shock tube with a single laser pulse
Review of Scientific Instruments
High-temperature gas-phase kinetics of the thermal decomposition of tetramethoxysilane
Proceedings of the Combustion Institute
Shock-tube study of methane pyrolysis in the context of energy-storage processes
Proceedings of the Combustion Institute
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
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].
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.
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.
Experimental and modeling study of carbon suboxide decomposition behind reflected shock waves
Physical Chemistry Chemical Physics, 2012
At temperatures between 1150 and 2000 K and pressures between 0.1 and 0.2 MPa, the thermal decomp... more At temperatures between 1150 and 2000 K and pressures between 0.1 and 0.2 MPa, the thermal decomposition of carbon suboxide (C(3)O(2)) behind reflected shock waves was investigated with a high-repetition-rate time-of-flight mass spectrometer (HRR-TOF-MS) connected to the end flange of a shock tube enabling rapid repetitive (100 kHz) measurements of the gas-phase composition. Concentration-time profiles for C(3)O(2) and CO were measured and compared to simulations based on an improved mechanism for C(3)O(2) decomposition and carbon cluster growth. In addition, relative concentrations of C atoms and C(2) molecules were detected and related to model predictions. For temperatures up to 1800 K, satisfactory agreement between experimental data and calculations was obtained. At higher temperatures, measurements and simulations differed noticeably. The importance of C(2) for the growth of carbon clusters was confirmed.
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.
Review of Scientific Instruments, 2018
The title cluster compound, [Ru 3 (C 19 H 17 PS)(CO) 11 ], comprises a triangle of Ru 0 atoms, tw... more The title cluster compound, [Ru 3 (C 19 H 17 PS)(CO) 11 ], comprises a triangle of Ru 0 atoms, two of which are bonded to four carbonyl ligands. The third metal atom is bound to three carbonyl ligands and the phosphane-P atom of a dissymmetric phosphane ligand, PPh 2 (C 6 H 4 SMe-4); no RuÁ Á ÁS interactions are observed. The phosphane occupies an equatorial position and its proximity to an Ru-Ru edge results in the elongation of this bond with respect to the others [2.8933 (2) A ˚cf. 2.8575 (2) and 2.8594 (3) A ˚]. In the crystal, phenyl-C-HÁ Á ÁO(carbonyl) and carbonyl-OÁ Á ÁO(carbonyl) [2.817 (2) A ˚] interactions combine to form a supramolecular chain propagating along [111]; the chains pack without directional interactions between them. The carbonyl-OÁ Á ÁO(carbonyl) and other weak contacts have an influence upon the Hirshfeld surfaces with OÁ Á ÁH contacts making the greatest contribution, i.e. 37.4% cf. 15.8% for OÁ Á ÁO and 15.6% for HÁ Á ÁH contacts.
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...
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.
Fuel, 2012
Delay times for first-and second-stage ignition of n-heptane and two practical kerosene-like fuel... more Delay times for first-and second-stage ignition of n-heptane and two practical kerosene-like fuels have been measured in a heated high-pressure shock tube at conditions similar to those found in homogeneous charge compression ignition (HCCI) engines. Initial reflected shock conditions covered temperatures from 700 to 1100 K, pressures from 20 to 65 bar, equivalence ratios of 0.5, 0.67, and 1, and exhaust gas recirculation rates (EGR) of 0%, 30%, and 50%. EGR is simulated by introducing additional N 2 in the test gas mixture. Because detailed chemical kinetics models are not available for practical fuels so far, we propose a global ignition time correlation that is fitted to the measured data. The empirical model describes both first-and second-stage ignition delay as a function of temperature, pressure, equivalence ratio and EGR. It is based on a three-stage Arrhenius approach, which has been extended to capture the first-stage ignition times and the influence of EGR. For each of the fuels, even for the fuels that contain cyclo-alkanes and aromatics, good agreement between model and experiment is observed, especially at lean and high-EGR conditions relevant for HCCI. Based on this extensive set of ignition data, interesting correlations between fuel composition and ignition behavior could be identified, which may prove useful in matching the fuel to the engine application.
Fuel, 2011
Ignition delay times for binary (ethanol/iso-octane, 25%/75% by liquid volume) and quinary (iso-o... more Ignition delay times for binary (ethanol/iso-octane, 25%/75% by liquid volume) and quinary (iso-octane/ toluene/n-heptane/diisobutylene/ethanol, 30%/25%/22%/13%/10%) gasoline surrogate fuels in air were measured under stoichiometric conditions behind reflected shock waves. The investigated post-shock temperature ranges from 720 to 1220 K at pressures of 10 bar for the binary mixture and 10 bar and 30 bar for the quinary mixture. Ignition delay times were evaluated using side-wall detection of CH* chemiluminescence (k = 431.5 nm). Multiple regression analysis of the data indicates global activation energy of 124kJ/molforthebinarymixtureand124 kJ/mol for the binary mixture and 124kJ/molforthebinarymixtureand101 kJ/mol for the quinary mixture and a pressure dependence exponent of À1.0 was obtained for the quinary mixture. The measurements were compared to predictions using a proposed detailed kinetics model for multicomponent mixtures that is based on the reference fuels (PRF) model as a kernel and incorporates sub-mechanisms to account for the chemistry of ethanol, toluene and diisobutylene. The model was tested using the measured ignition delay times for the surrogate fuels. Additional comparisons are based on literature data for other fuel combinations of the single constituents forming the quinary surrogate to insure that the modified mechanism still correctly predicts the behavior of simple fuels. The proposed model reproduces the trend of the experimental data for all pure fuels and blends investigated in this work, including the pressure dependence.
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 ChristianAlbrechtsUniversität zu Kiel vorgelegt von Mustapha Fikri Kiel 2004 Page 2. 2 ... more ... der ChristianAlbrechtsUniversität 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 ...
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.
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.
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.
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
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
Reaction-time-resolved measurements of laser-induced fluorescence in a shock tube with a single laser pulse
Review of Scientific Instruments
High-temperature gas-phase kinetics of the thermal decomposition of tetramethoxysilane
Proceedings of the Combustion Institute
Shock-tube study of methane pyrolysis in the context of energy-storage processes
Proceedings of the Combustion Institute
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
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].
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.
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.
Experimental and modeling study of carbon suboxide decomposition behind reflected shock waves
Physical Chemistry Chemical Physics, 2012
At temperatures between 1150 and 2000 K and pressures between 0.1 and 0.2 MPa, the thermal decomp... more At temperatures between 1150 and 2000 K and pressures between 0.1 and 0.2 MPa, the thermal decomposition of carbon suboxide (C(3)O(2)) behind reflected shock waves was investigated with a high-repetition-rate time-of-flight mass spectrometer (HRR-TOF-MS) connected to the end flange of a shock tube enabling rapid repetitive (100 kHz) measurements of the gas-phase composition. Concentration-time profiles for C(3)O(2) and CO were measured and compared to simulations based on an improved mechanism for C(3)O(2) decomposition and carbon cluster growth. In addition, relative concentrations of C atoms and C(2) molecules were detected and related to model predictions. For temperatures up to 1800 K, satisfactory agreement between experimental data and calculations was obtained. At higher temperatures, measurements and simulations differed noticeably. The importance of C(2) for the growth of carbon clusters was confirmed.