| 1. |
- Brackmann, Christian, et al.
(author)
-
Strategies for formaldehyde detection in flames and engines using a single-mode Nd:YAG/OPO laser system
- 2005
-
In: Applied Spectroscopy. - : SAGE Publications. - 0003-7028 .- 1943-3530. ; 59:6, s. 763-768
-
Journal article (peer-reviewed)abstract
- This paper presents technical developments for the detection of formaldehyde (CH2O) using laser-induced fluorescence. The easily accessible third harmonic of the Nd:YAG laser at 355 nm was used for excitation of formaldehyde. In order to investigate potential background fluorescence, e.g., from large molecules such as polyaromatic hydrocarbons, special attention was paid to investigating the possibility of scanning the wavelength of a single-mode Nd: YAG laser under the gain profile, ∼3 cm-1, on and off resonance. Furthermore, a technique for simultaneous detection of formaldehyde and OH using one laser system is presented. The single-mode Nd: YAG laser at 355 nm in combination with an optical parametric oscillator (OPO) laser tuned to 283 nm was used for simultaneous two-dimensional imaging of both species using one charge-coupled device (CCD) detector equipped with a dual filter image separator. The techniques are demonstrated with measurements in laboratory flames and the combined measurements are also demonstrated in an engine.
|
|
| 2. |
- Brackmann, Christian, et al.
(author)
-
Strategies for formaldehyde engines using a single-mode detection in flames and Nd : YAG/OPO laser system
- 2005
-
In: Applied Spectroscopy. - 1943-3530. ; 59:6, s. 763-768
-
Journal article (peer-reviewed)abstract
- This paper presents technical developments for the detection of formaldehyde (CH2O) using laser-induced fluorescence. The easily accessible third harmonic of the Nd:YAG laser at 355 nm was used for excitation of formaldehyde. In order to investigate potential background fluorescence, e.g., from large molecules such as polyaromatic hydrocarbons, special attention was paid to investigating the possibility of scanning the wavelength of a single-mode Nd:YAG laser under the gain profile, similar to 3 cm(-1), on and off resonance. Furthermore, a technique for simultaneous detection of formaldehyde and 011 using one laser system is presented. The single-mode Nd:YAG laser at 355 nm in combination with an optical parametric oscillator (OPO) laser tuned to 283 nm was used for simultaneous two-dimensional imaging of both species using one charge-coupled device (CCD) detector equipped with a dual filter image separator. The techniques are demonstrated with measurements in laboratory flames and the combined measurements are also demonstrated in an engine.
|
|
| 3. |
- Franke, Axel, et al.
(author)
-
Application of advanced laser diagnostics for the investigation of the ionization sensor signal in a combustion bomb
- 2005
-
In: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 81:8, s. 1135-1142
-
Journal article (peer-reviewed)abstract
- The ionization sensor is an electrical probe for diagnostics in internal combustion engines. Laser-induced fluorescence (LIF) imaging of fuel, hydroxyl (OH), and nitric oxide (NO) distributions has been employed to extend our knowledge about the governing processes leading to its signal. By monitoring the flame propagation in quiescent and turbulent mixtures, the cycle-to-cycle variations in the early sensor signal was attributed to the stochastic contact between flame front and electrodes. An analysis of the relationship between gas temperature and sensor current in the post-flame gas suggests a dominant role of alkali traces in the ionization process at the conditions under study. Significant cooling of the burned gas in the vicinity of the electrodes was observed in quiescent mixtures. Imaging of the post-flame gas in turbulent combustion revealed moving structures with varying NO and OH concentrations, which were identified as sources of variation in the sensor current.
|
|
| 4. |
- Hildingsson, Leif, et al.
(author)
-
Optical Diagnostics of HCCI and UNIBUS Using 2-D PLIF of OH and Formaldehyde
- 2005
-
In: SAE technical paper series.
-
Journal article (peer-reviewed)abstract
- Simultaneous OH- and formaldehyde planar-LIF measurements have been performed in an optical engine using two laser sources working on 283 and 355 nm, respectively. The measurements were performed in a light- duty diesel engine, using n-heptane as fuel, converted to single- cylinder operation and modified for optical access. It was also equipped with a direct-injection, common-rail system as well as an EGR system. The engine was operated in both HCCI mode, using a single fuel injection, and UNIBUS (Uniform Bulky Combustion System) mode, using two injections of fuel with one of the injections at 50 CAD before TDC and the other one just before TDC. The OH and formaldehyde LIF images were compared with the heat- release calculated from the pressure-traces. Analyses of the emissions, for example NOx and HC, were also performed for the different operating conditions.
|
|
| 5. |
- Kohse-Hoinghaus, K, et al.
(author)
-
Combustion at the focus: laser diagnostics and control
- 2005
-
In: Symposium (International) on Combustion. - : Elsevier BV. - 0082-0784. ; 30:1, s. 89-123
-
Journal article (peer-reviewed)abstract
- Fifty years after the foundation of the Combustion Institute and almost 150 years after Michael Faraday's famous lectures on the combustion of a candle, combustion diagnostics have come a long way from visual inspection of a flame to detailed analysis of a combustion process with a multitude of sophisticated techniques, often using lasers. The extended knowledge on combustion phenomena gained by application of these diagnostic techniques, combined with equally advanced numerical simulation of the process, has been instrumental in designing modern combustion devices with efficient performance and reduced pollutant emission. Also, similar diagnostic techniques are now employed to develop sensors for process control in combustion. This article intends to give a perspective on the potential of combustion diagnostics by highlighting selected application examples and by guiding the reader to recent literature. In particular, techniques are emphasized, which permit measurement of important features of the chemical composition, sometimes in conjunction with flow field parameters. Although a complete image of present research and applications in combustion diagnostics and control is beyond the scope of this article, this overview may be a starting place where ideas may be found to solve specific combustion problems with the aid of diagnostics.
|
|
| 6. |
- Li, Zhongshan, et al.
(author)
-
Mid-infrared polarization spectroscopy of polyatomic molecules: Detection of nascent CO2 and H2O in atmospheric pressure flames
- 2005
-
In: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 407:4-6, s. 243-248
-
Journal article (peer-reviewed)abstract
- We report the application of mid-infrared polarization spectroscopy (IRPS) for detection of nascent CO2 and H2O in atmospheric pressure flames. The recorded IRPS spectra demonstrated both the quantitative nature of the method and the suppression of strong infrared emission from flames. In spite of the high line-density of the hot polyatomic ro-vibrational spectrum, lines belonging to different CO2 and H2O hot bands were recognized in the chosen spectral region, which ensures the species-selective application of IRPS.
|
|
| 7. |
- Li, Zhongshan, et al.
(author)
-
Mid-infrared PS and LIF detection of CH4 and C2H 6 in cold flows and flames at atmospheric pressure
- 2005
-
In: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 30:1, s. 1629-1636
-
Journal article (peer-reviewed)abstract
- Mid-infrared polarization spectroscopy (IRPS) and laser-induced fluorescence (IRLIF) have been applied for detection of methane and ethane in atmospheric pressure cold flows and flames. Lines belonging to the asymmetric C-H stretching vibration bands v3 and v7 for methane and ethane, respectively, were probed with a tunable infrared laser beam at about 3.4 μm, which was obtained from difference frequency generation in a LiNbO3 crystal pumped by a dye-laser beam and a Nd:YAG fundamental laser beam. The dependence of IRPS and IRLIF signal of CH4 on different buffer gases, including He, Ar, N2, and CO2 was investigated. Simultaneous measurements of IRPS and IRLIF signals allowed a direct comparison of the two techniques, and IRPS was found to be superior in detection sensitivity and background discrimination. IRPS excitation scans of a methane and ethane mixture diluted in Ar were also performed in a jet at ambient pressure and temperature. Lines in the spectrum belonging to methane and ethane were fully recognized and assigned. From the ethane lines in the IRPS excitation spectrum, a detection limit of 50 ppm was conservatively estimated, and this indicates that IRPS is a promising sensitive technique for hydrocarbon identification and detection. Finally, CH4 IRPS detection in a CH4/H2/air premixed flat flame was demonstrated, with spatially resolved IRPS CH4 measurements along different heights in the flame.
|
|
| 8. |
- Omrane, Alaa, et al.
(author)
-
Surface temperature of decomposing construction materials studied by laser-induced phosphorescence
- 2005
-
In: Fire and Materials. - : Wiley. - 0308-0501 .- 1099-1018. ; 29:1, s. 39-51
-
Journal article (peer-reviewed)abstract
- Measurements of surface temperature and mass loss of decomposing construction materials during rapid pyrolysis are presented. Experiments have been performed With samples of low-density fiberboard. medium-density fiberboard,. particleboard and poly(methyl methacrylate) in a single particle reactor at temperatures between 300degrees and 600degreesC. Ultraviolet laser light was used to excite micrometer-Sized thermographic phosphor particles that Were deposited on the investigated materials. and the temperature was obtained from temporally resolved measurements of the laser-induced emission. The wood-based materials show a similar behavior, with small differences being attributed to differences in material properties. The surface temperature rapidly increases to about 400degreesC When a particle is introduced to the hot reactor. The initial phase is followed by rapid decomposition during Which the surface temperature is 380degrees-540degreesC. The heating rate is slowed down during the rapid pyrolysis. and again increases as the remaining char is heated to the reactor temperature. The poly (methyl methacrylate), however. melts and at high temperatures can be characterized as a liquid with a boiling point of about 40degreesC. Thermographic phosphors are concluded to be suitable for high precision remote measurements of the surface temperature of decomposing construction materials, and possibilities for further studies and developments of the technique are discussed. Copyright paired right arrows 2004 John Wiley Sons. Ltd.
|
|
| 9. |
- Richter, Mattias, et al.
(author)
-
Studies of the combustion process with simultaneous formaldehyde and OHPLIF in a direct-injected HCCI engine
- 2005
-
In: JSME International Journal. Series B: Fluids and Thermal Engineering. - : Japan Society of Mechanical Engineers. - 1340-8054. ; 48:4, s. 701-707
-
Journal article (peer-reviewed)abstract
- This paper presents simultaneous laser based measurements of formaldehyde and OH-radical distributions in a 0.5 liter optical HCCI engine with direct injection. Formaldehyde is formed as an intermediate species when combusting hydrocarbons. The formation occurs through low temperature reactions in an early phase of the combustion process. Later in the process formaldehyde is being consumed. Formaldehyde is, therefore, used as indicator of the first stage of combustion and a marker of zones with low-lemperature reactions. The OH radical is formed as an intermediate during the high temperature reactions, and is used as a marker of zones where the combustion is ongoing. The purpose of the investigation was to study how the combustion process is affected by the change in homogeneity that arises from early and late injection, respectively. The measurement technique used was planar laser-induced fluorescence where formaldehyde was excited at 355 nm and OH at 283 nm.
|
|
| 10. |
- Särner, Gustaf, et al.
(author)
-
Cycle Resolved Wall Temperature Measurements Using Laser-Induced Phosphorescence in an HCCI Engine
- 2005
-
In: SAE technical paper series.
-
Journal article (peer-reviewed)abstract
- Cycle-resolved wall temperature measurements have been performed in a one-cylinder, port-injected optical Scania D12 truck engine run in HCCI mode. Point measurements at various locations were made using Laser-Induced Phosphorescence (LIP). Single point measurements with thermographic phosphors utilize the temperature dependency of the phosphorescence decay time. The phosphorescence peak at 538 nm from the thermographic phosphor La2O2S:Eu was used to determine temperature. A frequency tripled 10 Hz pulsed Nd:YAG laser delivering ultraviolet (UV) radiation at 355 nm was used for excitation of the phosphor. Detection in the spectral region 535 - 545 nm was performed every cycle with a photo multiplier tube connected to a 3 GHz oscilloscope. Measurements were made at four points on the cylinder head surface and two points on the outlet and inlet valves respectively. For each location measurements were made at different loads and at different crank angle degrees (CAD). The aim of the presented work was to study the feasibility of using LIP for single-shot, cycle-resolved wall temperature measurements.
|
|
