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

Papers by M. Försth

This paper reports on the experimental investigation of the flame lift-off length for five differ... more This paper reports on the experimental investigation of the flame lift-off length for five different orifice diameters (∅0.100, ∅0.130, ∅0.160, ∅0.190, and ∅0.227 mm) of a diesel injector nozzle. The flame lift-off was determined from the measurement of 308 nm OH chemiluminescence for different fuel injection pressures using commercial diesel fuel and a Common Rail fuel injection equipment of passenger car size. The fuel injection pressures were 450, 900, and 1350 bar. The experiments were conducted at air pressures of 30, 50, 70, and 90 bar and at an air temperature of 750 K in a constant pressure spray chamber. It was observed that the flame lift-off length increases with increased injection pressure and increased orifice diameter.

SAE Technical Paper Series, 2003

Surface Science, 2003

The water formation reaction has been studied on a hot polycrystalline palladium catalyst and a t... more The water formation reaction has been studied on a hot polycrystalline palladium catalyst and a theoretical model has been derived with Chemkin in order to fit the experimental data. The results were compared with similar studies for platinum. The H 2 /O 2 reaction was measured with LIF and microcalorimetry on palladium at a temperature of 1300 K, pressures of 13 and 26 Pa and flows of 100 and 200 SCCM. The experiments were performed in a stagnation-point flow field, which was also the geometry modelled with Chemkin. The maximum in water production as a function of a H 2 (a H 2 ;H 2 Omax ), occurs at about 20% on platinum, while it occurs at about 40-45% on palladium; a H 2 is the hydrogen mixing ratio. However, the maximum in OH desorption (a H 2 ;OHmax ), occurs at about the same a H 2 for both palladium and platinum. In order that the theoretical model would match the experimental data for palladium it was necessary to assume a coverage dependent OH desorption energy, E d;OH a , according to E d;OH a ðhÞ ¼ E d;OH a ð0Þ À Bh, where B is a constant equal to 100 kJ/mol. The apparent desorption energy for OH on palladium was also measured at a H 2 ¼ 17% to 200 kJ/mol and a H 2 ¼ 45% to 220 kJ/mol. The main water-forming reaction on platinum is thought to be the hydrogen addition reaction H Ã + OH Ã () H 2 O Ã . For palladium, there are difficulties to determine the main water formation route because the OH desorption energy is believed to be coverage dependent. The reverse of reaction H Ã + OH Ã () H 2 O Ã seems to have greater importance for the OH formation on palladium than on platinum. The initial sticking coefficient of hydrogen and oxygen is found to be greater on palladium than on platinum by a factor of about 10.

Optics Letters, 2008

Sensitive and nonintrusive detection of HCl in reactive gas flows with high spatial and temporal ... more Sensitive and nonintrusive detection of HCl in reactive gas flows with high spatial and temporal resolution manner has for the first time (to our knowledge) been demonstrated using mid-infrared polarization spectroscopy (IRPS). Trace levels of HCl were prepared in an atmospheric pressure premixed CH4/O2/Ar flat flame by seeding a small amount of chloroform into the Ar flow. Detection of HCl with IRPS in the burnt region of the stoichiometric flame was performed by probing the fundamental ro-vibration transitions with a 3.2 microm tunable pulsed laser. The quantitative nature, the detection sensitivity, and the potential spectral interferences from water were investigated.

Fire and Materials, 2011

ABSTRACT Infrared polarization spectroscopy (IRPS) was used to detect HCl in an 800 mm long tube ... more ABSTRACT Infrared polarization spectroscopy (IRPS) was used to detect HCl in an 800 mm long tube furnace. Pieces of a polyvinyl chloride-carpet were continuously fed into the furnace producing a heavy smoke, which is exemplified by the fact that the smoke completely obscured a red laser beam from a He-Ne laser. This constitutes a very harsh environment from a diagnostic point of view due to the high smoke density and relatively long path through the furnace. Despite this it was still possible to measure HCl concentrations in the smoke down to a level of ∼50ppm using IRPS. The explanation for this success is twofold. First, the IRPS method is inherently almost noise free due to the use of crossed polarizers, creating a virtually zero background. Second, the laser beam attenuation due to non-resonant absorption and scattering in the smoke, especially with soot particles, decreases with increasing laser wavelength. Therefore, this type of measurements would have been much more difficult to perform in the visible regime (with wavelengths ∼0.5µm) than in the infrared regime (with wavelengths ∼3µm). Copyright © 2010 John Wiley & Sons, Ltd.

Combustion and Flame, 1999

The OH concentration outside a Pt catalyst at 1300 K, in a stagnation flow of 90% O 2 and 10% H 2... more The OH concentration outside a Pt catalyst at 1300 K, in a stagnation flow of 90% O 2 and 10% H 2 , has been studied by planar laser-induced fluorescence (PLIF), and compared to measurements outside a heated glass surface. The total pressure in the system was varied from 0.2 to 120 torr. At low pressure, surface reactions were observed for the Pt surface, but not for the glass. At higher pressure, gas-phase ignition occurred for both systems, but not at the same pressure: ignition occurred at a lower pressure outside the inert glass surface. Computer modeling using CHEMKIN confirmed these results. The difference in gas-phase ignition is also seen in the modeling results, and it is due to the removal of atomic O and H from the gas by adsorption and reaction on the catalytic surface. The catalytic reaction mechanism on the surface plays an important role as it enhances the removal of radicals, compared to a surface where only radical recombination back to reactants is allowed.

Applied Optics, 2000

We present a method for compensating laser attenuation in optically dense sprays, in particular f... more We present a method for compensating laser attenuation in optically dense sprays, in particular for use in combustion engine research. Images of the fuel sprays are produced by planar laser imaging, where Mie scattered light from a cross section of the spray is imaged onto a CCD camera. The compensation scheme is based on the Beer-Lambert law, which is used here to sum up the loss of light along the path of the laser in the image, and to compensate iteratively, pixel by pixel, for this loss.

Measurement Science and Technology, 2013

ABSTRACT

This paper reports on the experimental investigation of the flame lift-off length for five differ... more This paper reports on the experimental investigation of the flame lift-off length for five different orifice diameters (∅0.100, ∅0.130, ∅0.160, ∅0.190, and ∅0.227 mm) of a diesel injector nozzle. The flame lift-off was determined from the measurement of 308 nm OH chemiluminescence for different fuel injection pressures using commercial diesel fuel and a Common Rail fuel injection equipment of passenger car size. The fuel injection pressures were 450, 900, and 1350 bar. The experiments were conducted at air pressures of 30, 50, 70, and 90 bar and at an air temperature of 750 K in a constant pressure spray chamber. It was observed that the flame lift-off length increases with increased injection pressure and increased orifice diameter.

SAE Technical Paper Series, 2003

Surface Science, 2003

The water formation reaction has been studied on a hot polycrystalline palladium catalyst and a t... more The water formation reaction has been studied on a hot polycrystalline palladium catalyst and a theoretical model has been derived with Chemkin in order to fit the experimental data. The results were compared with similar studies for platinum. The H 2 /O 2 reaction was measured with LIF and microcalorimetry on palladium at a temperature of 1300 K, pressures of 13 and 26 Pa and flows of 100 and 200 SCCM. The experiments were performed in a stagnation-point flow field, which was also the geometry modelled with Chemkin. The maximum in water production as a function of a H 2 (a H 2 ;H 2 Omax ), occurs at about 20% on platinum, while it occurs at about 40-45% on palladium; a H 2 is the hydrogen mixing ratio. However, the maximum in OH desorption (a H 2 ;OHmax ), occurs at about the same a H 2 for both palladium and platinum. In order that the theoretical model would match the experimental data for palladium it was necessary to assume a coverage dependent OH desorption energy, E d;OH a , according to E d;OH a ðhÞ ¼ E d;OH a ð0Þ À Bh, where B is a constant equal to 100 kJ/mol. The apparent desorption energy for OH on palladium was also measured at a H 2 ¼ 17% to 200 kJ/mol and a H 2 ¼ 45% to 220 kJ/mol. The main water-forming reaction on platinum is thought to be the hydrogen addition reaction H Ã + OH Ã () H 2 O Ã . For palladium, there are difficulties to determine the main water formation route because the OH desorption energy is believed to be coverage dependent. The reverse of reaction H Ã + OH Ã () H 2 O Ã seems to have greater importance for the OH formation on palladium than on platinum. The initial sticking coefficient of hydrogen and oxygen is found to be greater on palladium than on platinum by a factor of about 10.

Optics Letters, 2008

Sensitive and nonintrusive detection of HCl in reactive gas flows with high spatial and temporal ... more Sensitive and nonintrusive detection of HCl in reactive gas flows with high spatial and temporal resolution manner has for the first time (to our knowledge) been demonstrated using mid-infrared polarization spectroscopy (IRPS). Trace levels of HCl were prepared in an atmospheric pressure premixed CH4/O2/Ar flat flame by seeding a small amount of chloroform into the Ar flow. Detection of HCl with IRPS in the burnt region of the stoichiometric flame was performed by probing the fundamental ro-vibration transitions with a 3.2 microm tunable pulsed laser. The quantitative nature, the detection sensitivity, and the potential spectral interferences from water were investigated.

Fire and Materials, 2011

ABSTRACT Infrared polarization spectroscopy (IRPS) was used to detect HCl in an 800 mm long tube ... more ABSTRACT Infrared polarization spectroscopy (IRPS) was used to detect HCl in an 800 mm long tube furnace. Pieces of a polyvinyl chloride-carpet were continuously fed into the furnace producing a heavy smoke, which is exemplified by the fact that the smoke completely obscured a red laser beam from a He-Ne laser. This constitutes a very harsh environment from a diagnostic point of view due to the high smoke density and relatively long path through the furnace. Despite this it was still possible to measure HCl concentrations in the smoke down to a level of ∼50ppm using IRPS. The explanation for this success is twofold. First, the IRPS method is inherently almost noise free due to the use of crossed polarizers, creating a virtually zero background. Second, the laser beam attenuation due to non-resonant absorption and scattering in the smoke, especially with soot particles, decreases with increasing laser wavelength. Therefore, this type of measurements would have been much more difficult to perform in the visible regime (with wavelengths ∼0.5µm) than in the infrared regime (with wavelengths ∼3µm). Copyright © 2010 John Wiley & Sons, Ltd.

Combustion and Flame, 1999

The OH concentration outside a Pt catalyst at 1300 K, in a stagnation flow of 90% O 2 and 10% H 2... more The OH concentration outside a Pt catalyst at 1300 K, in a stagnation flow of 90% O 2 and 10% H 2 , has been studied by planar laser-induced fluorescence (PLIF), and compared to measurements outside a heated glass surface. The total pressure in the system was varied from 0.2 to 120 torr. At low pressure, surface reactions were observed for the Pt surface, but not for the glass. At higher pressure, gas-phase ignition occurred for both systems, but not at the same pressure: ignition occurred at a lower pressure outside the inert glass surface. Computer modeling using CHEMKIN confirmed these results. The difference in gas-phase ignition is also seen in the modeling results, and it is due to the removal of atomic O and H from the gas by adsorption and reaction on the catalytic surface. The catalytic reaction mechanism on the surface plays an important role as it enhances the removal of radicals, compared to a surface where only radical recombination back to reactants is allowed.

Applied Optics, 2000

We present a method for compensating laser attenuation in optically dense sprays, in particular f... more We present a method for compensating laser attenuation in optically dense sprays, in particular for use in combustion engine research. Images of the fuel sprays are produced by planar laser imaging, where Mie scattered light from a cross section of the spray is imaged onto a CCD camera. The compensation scheme is based on the Beer-Lambert law, which is used here to sum up the loss of light along the path of the laser in the image, and to compensate iteratively, pixel by pixel, for this loss.

Measurement Science and Technology, 2013

ABSTRACT