| 1. |
- Ibron, Christian, et al.
(författare)
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Numerical simulation of a mixed-mode reaction front in a PPC engine
- 2021. - 4
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 38, s. 5703-5711
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Konferensbidrag (refereegranskat)abstract
- The ignition process, mode of combustion and reaction front propagation in a partially premixed combustion (PPC) engine running with a primary reference fuel (87 vol% iso-octane, 13 vol% n-heptane) were investigated numerically in a large eddy simulation (LES). A one-equation sub-grid scale model coupled to the partially stirred reactor model and a finite rate chemical model were used in LES. Different combustion modes, ignition front propagation, premixed flame and non-premixed flame, were observed simultaneously. Displacement speed of CO iso-surface propagation described the transition of premixed auto-ignition to non-premixed flame. High temporal resolution optical data of CH2O and chemiluminescence were compared with simulated results. A high-speed ignition front was found to expand through fuel-rich mixture and stabilize around stoichiometry in a non-premixed flame while lean premixed combustion occurs in the spray wake at a much slower pace. A good qualitative agreement of the distribution of chemiluminescence and CH2O formation and destruction indicated that the simulation approach sufficiently captures the driving physics of mixed-mode combustion in PPC engines. The transition from auto-ignition to flame occurs over a period of several crank angles and the reaction front propagation can be captured using the described model.
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| 2. |
- Lundgren, Marcus Olof, et al.
(författare)
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Effects of Post-Injections Strategies on UHC and CO at Gasoline PPC Conditions in a Heavy-Duty Optical Engine
- 2017
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2017:March
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Tidskriftsartikel (refereegranskat)abstract
- Gasoline partially premixed combustion (PPC) has shown potential in terms of high efficiency with low emissions of oxides of nitrogen (NOx) and soot. Despite these benefits, emissions of unburned hydrocarbons (UHC) and carbon monoxide (CO) are the main shortcomings of the concept. These are caused, among other things, by overlean zones near the injector tip and injector dribble. Previous diesel low temperature combustion (LTC) research has demonstrated post injections to be an effective strategy to mitigate these emissions. The main objective of this work is to investigate the impact of post injections on CO and UHC emissions in a quiescent (non-swirling) combustion system. A blend of primary reference fuels, PRF87, having properties similar to US pump gasoline was used at PPC conditions in a heavy duty optical engine. The start of the main injection was maintained constant. Dwell and mass repartition between the main and post injections were varied to evaluate their effect. All points were run at 7 bar IMEPg. High-speed imaging of the natural combustion luminescence was performed together with measurements of performance and engine out emissions. Results show reduction in both CO and UHC with close coupled injections. A large close coupled post injection show the largest reduction in UHC. Analysis show that a post injection prior to combustion reduces the dribble and increases the recirculation in the downstream region of the fuel jet, hence reaching more of the UHC in the area near the injector. General observations show that the partition of fuel between the injections have the largest impact on the CO while the dwell time affects UHC emissions. Injector dribble seems to be a significant contributor to the UHC emissions.
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| 3. |
- Lundgren, Marcus, et al.
(författare)
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Optical study on combustion transition from HCCI to PPC with gasoline compression ignition in a HD engine
- 2016. - April
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Ingår i: SAE 2016 World Congress and Exhibition. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. ; 2016-April
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Konferensbidrag (refereegranskat)abstract
- The partially premixed combustion (PPC) concept has shown high efficiency with low soot emissions. However, the in-cylinder phenomena are still to be explained and evaluated for further progress in the research. This work studies the start of combustion process during a transition from homogenous charge compression ignition (HCCI) to PPC. The process is visualized using a heavy-duty, non-swirling engine modified for optical access. High speed video was used to capture the natural luminosity of the combustion. The fuel used was PRF87. Single and double injection strategies were used at a load kept to the moderate level of 7.5 bar IMEPg. Single injections were swept from early HCCI to retarded PPC conditions whilst running a cycle to cycle temperature sweep, to capture the effect of injection timing and temperature differences simultaneously. Results show that retarded injections show less cycle-to-cycle variation due to temperature variations. Advanced in-bowl injections show a stochastic behavior in the location of the first combustion, due to large variations in local fuel rich zones. For the double injection case the main injection cools the bulk temperature and hence delays the start of combustion before igniting in the fuel rich zones.
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| 4. |
- Wang, Zhenkan, et al.
(författare)
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Simultaneous 36 kHz PLIF/chemiluminescence imaging of fuel, CH2O and combustion in a PPC engine
- 2019
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 37:4, s. 4751-4758
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Tidskriftsartikel (refereegranskat)abstract
- The requirements on high efficiency and low emissions of internal combustion engines (ICEs) raise the research focus on advanced combustion concepts, e.g., premixed-charge compression ignition (PCCI), partially premixed compression ignition (PPCI), reactivity controlled compression ignition (RCCI), partially premixed combustion (PPC), gasoline compression ignition (GCI) etc. In the present study, an optically accessible engine is operated in PPC mode, featuring compression ignition of a diluted, stratified charge of gasoline-like fuel injected directly into the cylinder. A high-speed, high-power burst-mode laser system in combination with a high-speed CMOS camera is employed for diagnostics of the autoignition process which is critical for the combustion phasing and efficiency of the engine. To the authors' best knowledge, this work demonstrates for the first time the application of the burst-system for simultaneous fuel tracer planar laser induced fluorescence (PLIF) and chemiluminescence imaging in an optical engine, at 36 kHz repetition rate. In addition, high-speed formaldehyde PLIF and chemiluminescence imaging are employed for investigation of autoignition events with a high temporal resolution (5 frames/CAD). The development of autoignition together with fuel or CH2O distribution are simultaneously visualized using a large number of consecutive images. Prior to the onset of combustion the majority of both fuel and CH2O are located in the recirculation zone, where the first autoignition also occurs. The ability to record, in excess of 100 PLIF images, in a single cycle brings unique possibilities to follow the in-cylinder processes without the averaging effects caused by cycle-to-cycle variations.
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| 5. |
- Wang, Zhenkan, et al.
(författare)
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Ultra-High Speed Fuel Tracer PLIF Imaging in a Heavy-Duty Optical PPC Engine
- 2018
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2018-April
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Tidskriftsartikel (refereegranskat)abstract
- In order to meet the requirements in the stringent emission regulations, more and more research work has been focused on homogeneous charge compression ignition (HCCI) and partially premixed combustion (PPC) or partially premixed compression ignition (PCCI) as they have the potential to produce low NOx and soot emissions without adverse effects on engine efficiency. The mixture formation and charge stratification influence the combustion behavior and emissions for PPC/PCCI, significantly. An ultra-high speed burst-mode laser is used to capture the mixture formation process from the start of injection until several CADs after the start of combustion in a single cycle. To the authors' best knowledge, this is the first time that such a high temporal resolution, i.e. 0.2 CAD, PLIF could be accomplished for imaging of the in-cylinder mixing process. The capability of resolving single cycles allows for the influence of cycle-to-cycle variations to be eliminated. This ability to study individual cycles aids the understanding of the mixture formation process as well as the cycle-to-cycle variations. Strong air entrainment at the boundary layer can be clearly observed and followed as the mixing process progresses. The formation of eddies created by the shear force and their rotational motion can be continuously observed during the mixing process. The interaction between two adjacent spray plumes in the recirculation zone is well captured and studied. In addition, the mixing process resulting in the stratified fuel charge being located in the recirculation zone before the SOC while the areas along the original spray axis are leaned out after the end of injection, can be followed in one time sequence. Moreover, the auto-ignition position and early flame development can be studied, from the high-speed chemiluminescence imaging, together with the fuel distribution in the combustion chamber.
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| 6. |
- Abou Nada, Fahd Jouda, et al.
(författare)
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A first application of thermographic phosphors in a marine two-stroke diesel engine for surface temperature measurement
- 2014
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Ingår i: Proceedings of the ASME 2014 Internal Combustion Engine Division Fall Technical Conference (ICEF2014). ; , s. 001-001
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Konferensbidrag (refereegranskat)abstract
- Phosphor thermometry is applied for the first time in a large-bore two-stroke diesel engine. The work proves the practicality of phosphor thermometry in large-bore engines. The experiments were conducted on the MAN 4T50ME-X marine research engine equipped with an optical cylinder head. By employing a thin surface coating of CdWO4 phosphor, cycle resolved temperature measurements of the cylinder wall were obtained. Motored and fired engine operations were tested at engine loads covering the low and medium engine load range. Phosphor thermometry proved to be successful in retrieving the temperature with standard deviations ranging around 1-8 K. Experimental considerations like detector linearity, coating thickness and an automated phosphor calibration routine will be addressed.
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| 7. |
- Abou Nada, Fahd Jouda, et al.
(författare)
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Development of an automatic routine for calibration of thermographic phosphors
- 2014
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Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 25:2
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Tidskriftsartikel (refereegranskat)abstract
- An automated routine for the continuous calibration of thermographic phosphors was developed as a replacement for the conventional calibration scheme that relied on fixed temperature points. The automated calibration routine was validated using Mg 3 F 2 GeO 4 :Mn as a calibration phosphor. Hardware and software aspects of the calibration process were addressed in this development. The hardware aspect included a new substrate design using a high performance alloy, the Hastelloy-C alloy, whereas the software aspect included an automated acquisition system which was capable of acquiring simultaneous thermocouple temperatures and phosphor decay waveform in real time. The design of the calibration process eliminates the need for a system in thermal equilibrium during a phosphor calibration measurement. Temperature ramping rates of up to 4 K min −1 were employed in the oven without a delay in the temperature response being measured between the phosphor and the thermocouples involved. In addition, the automated calibration setup allowed for detailed investigations on the effect of heat being delivered to the phosphor coating by the laser. These findings were confirmed by a simple heat transfer model, based on lumped system analysis. In comparison to the data acquisition performed at several fixed points with the conventional calibration scheme, the experiment duration was shortened by a factor of 4 with the overall accuracy improved by 1–2 K.
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| 8. |
- Abou Nada, Fahd Jouda, et al.
(författare)
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Improved measurement precision in decay time‑based phosphor thermometry
- 2016
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 1432-0649 .- 0946-2171. ; 122
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Tidskriftsartikel (refereegranskat)abstract
- This study comprises a continuation of the previous efforts of the authors to characterize different sources of errors in phosphor thermometry based on the determination of luminescence decays from thermographic phosphors. Whereas earlier investigations focused on point detectors utilizing different sensor technology, this work presents a comparison of four PMTs that are identical in terms of their product type. These detectors are supposedly identical, but the investigations revealed that their response is strictly individual. This study also shows a linear excitation energy dependence for the decay time of cadmium tungstate (CdWO4), the phosphor being used in this work. In addition, the potential influence of the intense and short fluorescence peak preceding the weaker and longer exponential decay in some phosphor materials, was investigated using the electrical signal gating capability of the PMT. Finally, the evaluated decay time also appeared to be affected by the oscilloscope settings used when recording the phosphorescence signals. The presented results indicate that all operating parameters from the calibration measurement need to be rigorously reproduced in order to avoid systematic temperature errors in phosphor thermometry experiments that are based on reproducible measurements of the decay time. These results should be of more general interest also outside the phosphor community as the findings, presented herein, in principal concern all kinds of measurements that are dependent on reproducible measurements of signal shapes or time-transients.
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| 9. |
- Abou Nada, Fahd Jouda, et al.
(författare)
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Investigation of the effect of engine lubricant oil on remote temperature sensing using thermographic phosphors
- 2016
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 179, s. 568-573
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Tidskriftsartikel (refereegranskat)abstract
- Phosphor thermometry, a remote temperature sensing technique, is widely implemented to measure the temperature of different combustion engines components. The presence of engine lubricant can influence the behavior of the applied sensor materials, known as thermographic phosphors, and thus leading to erroneous temperature measurements. The effect of two engine lubricants on decay times originating from six different thermographic phosphors was investigated. The decay time of each thermographic phosphor was investigated as a function of lubricant/phosphor mass ratio. Tests were conducted at temperatures around 293 K and 376 K for both lubricants. The investigations revealed that ZnO:Zn and ZnS:Ag are the only ones that exhibit a change of the decay time as function of the lubricant/phosphor mass ratio. While the remaining thermographic phosphors, namely BaMg2Al16O27:Eu (BAM), Al2O3-coated BaMg2Al16O27:Eu, La2O2S:Eu, Mg3F2GeO4:Mn, displayed no sensitivity of their characteristic decay time on to the presence of lubricant on the porous coating. Biases in the calculated temperature are to be expected if the utilized thermographic phosphor displays decay time sensitivity to the existence of the engine lubricant within the sensor. Such distortions are concealed and can occur undetected leading to false temperature readings for the probed engine component.
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| 10. |
- Abou Nada, Fahd Jouda, et al.
(författare)
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On the automation of thermographic phosphor calibration
- 2014
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Ingår i: Proceedings of the 60th International Instrumentation Symposium.
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Konferensbidrag (refereegranskat)abstract
- Thermographic phosphors can be robust temperature remote sensors. The accuracy of the temperature measured by the phosphor is highly dependent on the quality of the phosphor calibration used. Conventionally, thermographic phosphors are calibrated by measuring a series of decay curves at known stable oven temperatures. The process is then repeated covering the thermal sensitivity range of the phosphor chosen. Heating and cooling rates of high temperature ovens are usually low. Also, thermal equilibrium of the system is required at each calibration temperature before acquiring luminescence decay curves. Thus, the process is usually time consuming and the number of calibration points achieved is limited to a couple of dozen points. This study presents and validates the development of an automatic routine for the calibration of thermographic phosphors. It was designed to continuously and simultaneously acquire phosphor decay curves along with their corresponding thermocouple temperatures. The developed routine required software and hardware improvements. An updated design of the calibration substrate was implemented to improve the thermal conditions during calibration. Thermal gradients were further studied using a heat transfer model. The routine implemented a specially designed sparsing algorithm that reduced the sampling rate of the decaying luminescence curve without influencing the calculated decay time. The upper heating rate is set at 4 K.min-1 due to limitation imposed by the ceramic calibration oven. The phosphors CdWO4 and Mg3F2GeO4:Mn were chosen to validate the finalized routine. After the completion of the calibration process, a library-based calibration is created as the final product. The automated calibration routine delivered an overall accuracy improvement of 1-2 K, reduced calibration duration by factor of four and provided the possibility of deriving signal recognition algorithms. The condensed calibration dataset produced by the proposed calibration routine was further employed to develop a novel signal shape recognition algorithm for temperature evaluation.
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| 11. |
- Abou Nada, Fahd Jouda, et al.
(författare)
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Remote temperature sensing on and beneath atmospheric plasma sprayed thermal barrier coatings using thermographic phosphors
- 2016
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 302, s. 359-367
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Tidskriftsartikel (refereegranskat)abstract
- Investigations on remote temperature sensing of yttria stabilized zirconia (YSZ) thermal barrier coatings (TBCs) at the surface and at the bond-coat/top-coat interface were carried out. Using Y2O3:Eu thermographic phosphor as an embedded temperature sensing layer, sub-surface temperature probing through 300 μm of atmospheric plasma sprayed YSZ is demonstrated. The Y2O3:Eu thermographic phosphor displays a temperature sensitivity ranging between 400 °C up to a maximum of 900 °C when utilizing the luminescence originating from the 611 nm emission band. Dysprosium stabilized zirconia (10 wt.% DySZ), a TBC material, is also investigated and established as a temperature sensor from 400 °C up to a temperature of 1000 °C using both the intensity decay time and emission intensity ratio methods. In addition, the luminescence of presumed optically inactive YSZ materials was spectroscopically investigated in terms of optical interferences caused by impurities. A validation temperature probing measurement through 300 μm of YSZ top-coat was successfully performed in a SGT-800 Siemens burner running at six different operating conditions in an atmospheric combustion rig.
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| 12. |
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| 13. |
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| 14. |
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| 15. |
- Aldén, Marcus, et al.
(författare)
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Application of Cars Spectroscopy To the Detection of So2
- 1988
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Ingår i: Applied Spectroscopy. - : SAGE Publications. - 1943-3530 .- 0003-7028. ; 42:8, s. 1421-1427
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Tidskriftsartikel (refereegranskat)abstract
- Experiments have been performed to investigate the possibility of detecting low concentrations of SO2 using CARS spectroscopy. The experiments were also aimed at high-temperature investigations both in a heated cell and in a flame. During the cell measurements it was clearly revealed that the temperature has a dramatic influence on the shape of the CARS spectra, indicating a good potential for thermometry using SO2 and CARS spectroscopy.
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| 16. |
- Aldén, Marcus, et al.
(författare)
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Application of laser-induced fluorescence and CARS for combustion diagnostics
- 1993
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Ingår i: Berichte der Bunsengesellschaft für Physikalische Chemie. - 0005-9021. ; 97:12, s. 1643-1649
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Tidskriftsartikel (refereegranskat)abstract
- Laser diagnostic techniques have during the last decade been successfully applied for diagnostics of combustion processes. The main advantages with these techniques are that they are inherently non-intrusive and that spatially as well as temporally resolved information can be achieved. The current paper will exemplify two different laser spectroscopic techniques. Laser-Induced Fluorescence (LIF), and Coherent anti-Stokes Roman Scattering (CARS), which are currently the most used laser techniques for temperature and species concentration measurements in combustion systems.
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| 17. |
- Aldén, Marcus
(författare)
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Application of Laser Techniques for Combustion Studies
- 1983
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim for this work has been to increase the applicability of laser spectroscopy techniques for studies of combustion processes, both what regards in-flame experiments, exhaust-gas analysis and remote sensing of the atmosphere. Raman spectroscopy has been used for analysis of exhaust gases from flames, model fires of wood and for inflame measurements. Coherent anti-Stokes Raman Spectroscopy CARS, has been used for detection of several flame constituents e.g. o2 , CO, H2o, CH4 and H2 . Flame temperatures are measured using CARS spectra from N2 molecules. The CARS technique has also been used for simultaneous detection of several species e.g. N2/CO, co2;o2 and CO/H2 . The applications of broadband rotational CARS have also been demonstrated in non-flame gases, whereas scanning rotational CARS has been used for flame experiments. Laser-induced fluorescence LIF is especially attractive for radical detection, and LIF spectra for several flame radicals are presented, e.g. OH, CN, CH and c2 as well as relative concentration profiles for different radicals as a function of height above the burner. Special emphasis has been paid to space-resolved detection of radicals in flames, e.g. OH using a diode array detector. In a refined experiment, both c2 and OH were spatially detected using two laser systems. Two-photon excitation is a rather new and fascinating approach for detection of flame species that absorb in spectral regions not accessible for laser sources. In this way oxygen atoms have been detected in an acetylene/oxygen flame. Closely connected to combustion studies using laser methods is remote sensing of pollutants in the atmosphere using laser 7 techniques. These techniques have been used for laboratory experiments and in real-world measurements. E.g., NO has been detected using long-path absorption, whereas remote detection of Hg atoms has been performed using the dial technique.
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| 18. |
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| 19. |
- Aldén, Marcus, et al.
(författare)
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Applications of two-photon absorption for detection of CO in combustion gases
- 1984
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Ingår i: Applied Physics B. - 0946-2171. ; 33:4, s. 205-208
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Tidskriftsartikel (refereegranskat)abstract
- Laser-induced fluorescence has been used for detection of CO in different environments. The fluorescence light was obtained by using a two-photon transition between theX1?- and theB1?- electronical states around 230 nm. Cell measurements indicate a detection limit lower than 0.1 ppm. Measurements in a CH4/air flame and in a low pressure dc discharge were realized with a diode-array detector, which was used in an imaging mode, permitting single-shot CO distributions to be captured.
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| 20. |
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| 21. |
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| 22. |
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| 23. |
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| 24. |
- Aldén, Marcus, et al.
(författare)
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Development and application of high-speed laser visualization techniques in combustion research
- 2017
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Ingår i: The Micro-World Observed by Ultra High-Speed Cameras : We See What You Don't See - We See What You Don't See. - Cham : Springer International Publishing. - 9783319614908 - 9783319614915 ; , s. 241-259
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Bokkapitel (refereegranskat)abstract
- In order to fulfil the requirements of available energy resources, there is a great need to obtain a sustainable and environmentally friendly energy utilization using combustion processes. In order to do this, it is of utmost importance to utilize non-intrusive diagnostic techniques with high spatial and temporal resolution which can characterize the combustion process and also validate combustion models. During the last decades different laser techniques have proven to fulfil these requirements. A special requirement in practical applications when highly turbulent flames are to be investigated, is to be able to follow the phenomena in time, i.e. it is important to develop and apply high speed laser diagnostics. In the present chapter we are describing the use of high speed lasers together with high speed detectors which make it possible to probe in two dimensions even the fastest combustion phenomena in real time. The chapter is describing the use of a so called Multi YAG laser which together with a framing camera is able to record up to eight images. Also the use of a high repetition rate laser and a high power burst laser together with CMOS cameras and their application for studies of turbulent combustion phenomena are described. The examples are mainly taken from the author's laboratory and include more academic studies of turbulent flames but also practical applications in engines.
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| 25. |
- Aldén, Marcus
(författare)
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Development and applications of laser spectroscopic techniques related to combustion diagnostics
- 2006
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Ingår i: Second International Conference on Optical and Laser Diagnostics. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 45, s. 18-18
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Konferensbidrag (refereegranskat)abstract
- Thanks to features as non-intrusiveness combined with high spatial and temporal resolution, various laser diagnostic techniques have during the last decades become of utmost importance for characterization of combustion related phenomena. In the following presentation some further development of the techniques will be highlighted aiming at a) surface temperatures using Thermographic Phosphors, TP, b) species specific, spatially and temporally resolved detection of species absorbing in the IR spectral region using polarization spectroscopy and Laser-induced fluorescence, and finally c) high speed visualization using a special designed laser system in combination with a framing camera. In terms of surface thermometry, Thermographic Phosphors have been used for many years for temperature measurements on solid surfaces. We have during the last years further developed and applied this technique for temperature measurements on burning surfaces and on materials going through phase shifts, e.g. pyrolysis and droplets. The basic principle behind this technique is to apply micron size particles to the surface of interest. By exciting the TP with a short pulse UV laser (ns), the phosphorescence will exhibit a behaviour where the spectral emission as well as the temporal decay are dependent on the temperature. It is thus possible to measure the temperature both in one and two dimensions. The presentation will include basic description of the technique as well as various applications, e.g in fire science, IC engines and gasturbines. Several of the species of interest for combustion/flow diagnostics exhibit a molecular structure which inhibits the use of conventional laser-induced fluorescence for spatially and spectrally resolved measurements. We have during the last years investigated the use of excitation and detection in the infrared region of the spectrum. Here, it is possible to detect both carbonmono/dioxide, water as well as species specific hydrocarbons. The techniques which have been investigated are laser-induced fluorescence and polarization spectroscopy. In the latter case several species have been detected both in free flows as well as flames, e.g in addition to water and carbondioxide also the hydroxyl radical and different hydrocarbons including methane, acetylene, ethane and the methyl radical. One parameter of utmost importance for visualization combustion/flow phenomena is the possibility to make this visualization in real time with adequate time resolution. We have for several years developed and applied a special designed laser/detector system for high repetition rate measurements which has been applied for several real-world applications, e.g internal combustion engines. The system can also be used for three dimensional visualization by sweeping the laser pulses through the region of interest and consequent detection with the framing camera. Also in this case experiment from industrial applications will be exemplified.
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| 26. |
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| 27. |
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| 28. |
- Aldén, Marcus, et al.
(författare)
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Laser-induced phosphorescence spectroscopy: development and application of thermographic phosphors (TP) for thermometry in combustion environments
- 2014
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Ingår i: Laser Spectroscopy for Sensing Fundamentals, Techniques and Applications. - : Elsevier. - 2050-1501. - 9780857092731 - 9780857098733 ; , s. 258-291
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Bokkapitel (refereegranskat)abstract
- In this chapter a temperature probing technique based on the spectroscopy of inorganic luminescent materials is described and exemplified in experiments related to combustion. The basic features of thermographic phosphors which enable remote temperature diagnostics to be performed with a high degree of sensitivity and accuracy, are outlined. This technique is superior to those based on thermocouples and pyrometry, particularly in the vicinity of flames and when the measured surface is subjected to random movements. Many thermographic phosphors have the property of being insensitive to variations in pressure up to 1 GPa. This property extends the use and development of thermographic thermometry to such domains as internal combustion engines and gas turbines, for which examples are also provided.
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| 29. |
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| 30. |
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| 31. |
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| 32. |
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| 33. |
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| 34. |
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| 35. |
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| 36. |
- Aldén, Marcus
(författare)
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Spatially and temporally resolved laser/optical diagnostics of combustion processes : From fundamentals to practical applications
- 2023
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 39:1, s. 1185-1228
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Tidskriftsartikel (refereegranskat)abstract
- Laser diagnostic techniques have for more than five decades been used for gaining a deepened understanding of various combustion processes. The main reason for this is the possibility of non-intrusive measurements of key combustion parameters, e.g. species concentrations, temperatures and velocities, with high spatial and temporal resolution. The present paper will describe some development of the techniques themselves, followed by applications of relevant diagnostic techniques for studies of combustion phenomena and then more applied activities often related to challenges in an industrial environment. The paper is not meant to be a complete review of the entire research field but rather a survey with a majority of the contributions from the author's laboratory. After a short introduction and background (including some historical remarks), some common laser diagnostic techniques will be briefly described. Then some emerging techniques will be described. The first such area to be covered will highlight the use and application of structured illumination through Frequency Recognition Algorithm for Multiple Exposures, FRAME, enabling high speed visualization, 3D imaging and multiple species detection using one standard laser/detector. Furthermore, single ended diagnostics using Scheimpflug LIDAR and backward lasing using short pulse Stimulated Emission will be described and exemplified. In the category of studies of combustion phenomena, the paper will focus on diagnostic challenges and applications when studying combustion of some renewable fuels; solid biomass, ammonia and metals. When studying these fuels, often species not so commonly encountered when using fossil fuels are of interest, e.g. alkali containing species, e.g. KOH, KCl as well as nitrogen bound species, e.g. NH, NH2. In the field of applied diagnostics, preferably in an industrial environment, examples will be given from IC engines, gas turbines as well as full-scale industrial furnaces. In these phenomenological and industrial applications laser-induced fluorescence, Raman scattering and thermographic phosphorescence were mainly utilized, with some examples of photo-fragmentation LIF as well as non-liner techniques, IR-DFWM and CARS. The paper is concluded with a summary and some thoughts about the future.
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| 37. |
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| 38. |
- Aldén, Marcus, et al.
(författare)
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Thermographic phosphors for thermometry: A survey of combustion applications
- 2011
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Ingår i: Progress in Energy and Combustion Science. - : Elsevier BV. - 0360-1285. ; 37:4, s. 422-461
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Forskningsöversikt (refereegranskat)abstract
- Temperature is a fundamental thermodynamic parameter used to describe physical, chemical and biological processes. In combustion as in many other applications, knowledge about temperature plays a substantial role in helping to maintain an efficient and clean environment Being able to measure temperature accurately in combustion and in fire-related applications is important for giving a better understanding of heat transfer phenomena and improving existing models. In the present review paper a method based on the spectroscopy of inorganic luminescent materials is described and exemplified in experiments related to combustion. The method involves the use of thermographic phosphors which enable remote temperature diagnostics to be performed with a high degree of sensitivity and accuracy. The technique is superior to those based on thermocouples and pyrometry, particularly in the vicinity of flames and when the measured surface is subjected to random movements. Several phosphor materials suitable for temperature probing are described. The application of thermographic phosphors to temperature measurements in one-point and in two-dimensions in flame spread scenarios, and in pyrolysis experiments involving different construction materials and polymers are described. Many thermographic phosphors have the property of being insensitive to variations in pressure up to 1 GPa. This property extends the use and development of thermographic thermometry to other domains, such as internal combustion engines. The temperature has been measured in a point and in two-dimensions inside the combustion chamber. The complex procedures required to implement the use of thermocouples on moving objects inside an engine make thermocouples an expensive choice. It also limits the possibilities of altering the measurement locations and thereby also complicating the investigation of different engine geometries and components. Thermographic phosphors have also been employed in gas turbine applications. Temperature probing in the afterburner of a full-size aircraft engine is described with the aim to study the effects of various engine loads on the wall temperature. Furthermore, the application of thermographic phosphors to study the temperature of droplets in relation to sprays is described. In spray dynamics, temperature is a crucial parameter for gaining an understanding of atomisation, evaporation and heat convection from the surrounding gases. Finally the application of thermographic phosphors for gas temperature measurement by seeding the particles into a gas flow is described together with the challenges associated with seeding the particles for in-situ flame measurements. (C) 2010 Published by Elsevier Ltd.
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| 39. |
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| 40. |
- Aldén, Marcus, et al.
(författare)
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Two-photon excitation of atomic oxygen in a flame
- 1982
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Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018. ; 42:4, s. 244-246
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Tidskriftsartikel (refereegranskat)abstract
- Atomic oxygen has been detected in a lean acetylene/oxygen flame using the 2p43P2-2p33p3P two-photon transition at 226 nm and fluorescence detection at 845 nm.
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| 41. |
- Aldén, Marcus, et al.
(författare)
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Visualization and understanding of combustion processes using spatially and temporally resolved laser diagnostic techniques
- 2011
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 33, s. 69-97
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Forskningsöversikt (refereegranskat)abstract
- Laser diagnostic techniques have for more than 30 years added very valuable input for a deepened understanding of combustion processes. The present paper will focus on techniques developed for visualization of important parameters with the ability to get detailed information in space and time. The paper is not meant to be a complete review of the entire research field but rather a survey with a majority of the contributions from the authors' laboratory. After a short introduction and background, essentially three techniques will be highlighted. Planar Laser-Induced Fluorescence, PLIF, will be described in terms of further development directed towards the use of a high-power Alexandrite laser, in some cases yielding a substantially increased sensitivity as compared to the more conventional Nd:YAG and Excimer lasers. There will also be a description of possibilities for high-speed visualization, 3D imaging and the potential to visualize species requiring a two-photon excitation process. Regarding thermometry, the paper will describe and exemplify the use of Thermographic Phosphors, mainly for surface measurements but also in droplets and gas flows. The third area to be described is the use of Polarization Spectroscopy, PS, for spatially and temporally resolved measurements in the IR spectral region, e. g. CO2 and H2O, various hydrocarbons, HCl and HCN. The last chapter focuses on present challenges and future applications. A major challenge is diagnostics in environments with limited optical access. Two methods that are applicable under such conditions are discussed, namely endoscopic approaches and picosecond LIDAR. Another challenging area addressed is application of diagnostics in optically dense environments, e. g. sprays, where a new technique, Structured Laser Illumination Planar Imaging, SLIPI, has been developed for suppressing the influence of multiple scattering. Finally, approaches for measurements of "new" species, challenges associated with LIF quantification, as well as measurements in environments possessing strong background radiation are discussed. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 42. |
- Algotsson, Martin, et al.
(författare)
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In-cylinder Surface Thermometry using Laser Induced Phosphorescence
- 2012
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Ingår i: [Host publication title missing]. ; , s. 482-487
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Konferensbidrag (refereegranskat)abstract
- Surface temperature in internal combustion engines is of high interest when studying heat losses. Two approaches for retrieving the surface temperatures are thermocouples and Laser Induced Phosphorescence, LIP. This study aims to analyze LIP as a technique for measuring surface temperature in internal combustion engines. The motivation for this study is the need for accurate surface temperatures which can be used by predictive models and increase knowledge about heat transfer. In this work LIP measurements have been carried out in two optical engines. In the first engine a thermographic phosphor was applied on top of a metal piston. The second engine was fitted with a quartz liner which was coated with phosphor material. Several coating thicknesses have been tested and the LIP temperature was extracted from both opposing sides of the phosphor. Both engines were run in HCCI mode with reference fuels and electrically heated air. In a previous publication, the authors showed that a layer of phosphor can show different temperatures i.e. a higher temperature on the side facing the cylinder gas than on the side facing the wall. In this study it is shown which thickness is needed to accurately present the temperature for typical engine combustion. With an increasing thickness of the phosphor material, the surface gets gradually insulated and the phosphor temperature reading becomes inaccurate. LIP measurements from a quartz ring and a metal piston have been compared and the temperature increase during combustion is similar although the heat conductivity of quartz is 40-200 times smaller than the metal piston. Measurements with thermocouples often show a lower temperature increase than what is seen in the LIP results. The difference in heat conductivity between the phosphor coating and the underlying surface is of importance for understanding what temperature is actually measured.
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| 43. |
- Alwahabi, ZT, et al.
(författare)
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Infrared polarization spectroscopy of CO2 at atmospheric pressure
- 2004
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Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018. ; 233:4-6, s. 373-381
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Tidskriftsartikel (refereegranskat)abstract
- Polarisation spectroscopy (PS) was used to probe CO2 gas concentration in a CO2/N-2 binary mixture at atmospheric pressure and ambient temperature. The CO2 molecules were probed by a direct laser excitation to an overtone and combination vibrational state. The tuneable narrow linewidth infrared laser radiation at 2 mum was obtained by Raman shifting of the output from a single-longitudinal-mode pulsed alexandrite laser-system to the second Stokes component in a H, gas cell. Infrared polarisation spectroscopy (IRPS) and time-resolved infrared laser-induced fluorescence (IRLIF) spectra were collected. A linear dependence of the IRPS signal on the CO2 mole fraction has been found. This indicates that the IRPS signal is only weakly affected by the molecular collisions and that the inter- and intra- molecular energy transfer processes do not strongly influence the molecular alignment at the time scale of the measurements. Thus IRPS holds great potential for quantitative instantaneous gas concentration diagnostics in general. This is especially important for molecules which do not posses an accessible optical transition such as CO, CO2 and N2O. In addition, an accurate experimental method to measure the extinction ratio of the IR polarisers employed in this study has been developed and applied. With its obvious merits as simplicity, easy alignment and high accuracy, the method can be generalized to all spectral regions, different polarisers and high extinction ratios.
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| 44. |
- Alwahabi, Z. T., et al.
(författare)
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High resolution polarization spectroscopy and laser induced fluorescence of CO2 around 2 mu m
- 2007
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Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060. ; 42:1, s. 41-47
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Tidskriftsartikel (refereegranskat)abstract
- High resolution Infrared Polarisation Spectroscopy (IRPS) and Infrared Laser Induced Fluorescence (IRLIF) techniques were used to probe CO2/N-2 binary gas mixture at atmospheric pressure and ambient temperature. The probed CO2 molecules were prepared by laser excitation to an overtone and combination ro-vibrational state (12(0)1, J = 15) of CO2, centred at 4988.6612 cm(-1). IRPS and IRLIF line profiles were recorded for several CO2/N-2 binary mixtures. The observed IRLIF line shapes have the expected Lorentzian form while the observed IRPS line shapes are narrower by a factor of two than those recorded with the IRLIF and appear to have a Lorentzian-cubed profile. The recorded line profiles provide measurements of the pressure-broadening coefficient directly at atmospheric pressure. The Full-Width-Half-Maxima (FWHM) pressure broadening coefficients are measured, based on IRLIF, to be 0.2174 0.0092 cm(-1) atm(-1) and 0.1327 +/- 0.0077 cm(-1) atm(-1) for self- and N-2 collision broadening, respectively. The broadening coefficients obtained based on IRPS were measured to be similar to 8% larger than those obtained with IRLIF.
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| 45. |
- Alwahabi, Z. T., et al.
(författare)
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Measurements of collisional broadening coefficients by infrared polarization spectroscopy
- 2007
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Ingår i: Applied Spectroscopy. - : SAGE Publications. - 1943-3530 .- 0003-7028. ; 61:4, s. 424-427
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of collisional broadening coefficients, obtained at atmospheric pressure, by polarization spectroscopy. Using tunable single mode laser radiation at similar to 2 pro, high-resolution infrared polarization spectra were recorded for CO2-Ar and CO2-He binary mixtures. The recorded polarization spectra were fitted with a Lorentzian cubed function form to obtain the broadening coefficients. The full-width at half-maxima (FWHM) collisional broadening rates of CO2 by Ar and He, for the R14 (12(0)1 <- 00(0)0) line, have been determined to be 0.161 +/- 0.018 cm(-1) atm(-1) and 0.1823 +/- 0.0032 cm(-1) atm(-1), respectively.
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| 46. |
- Alwahabi, Z. T., et al.
(författare)
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Vibrational relaxation of CO2 (12(0)1) by argon
- 2009
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Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104. ; 359:1-3, s. 71-76
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Tidskriftsartikel (refereegranskat)abstract
- We present experimental measurements of the vibrational relaxation of CO2 (12(0)1) by argon, at ambient temperature (295 +/- 2 K). The CO2 molecules were directly excited to the (12(0)1, J = 14) ro-vibrational state by a tunable laser radiation at similar to 2 mu m. Time-resolved infrared fluorescence technique was used to study the collisional relaxation process. The bimolecular deactivation rate constant of CO2 (12(0)1) by argon was found to be (825 +/- 43 Torr(-1) s(-1)) while the self-deactivation by CO2 (00(0)0) was determined to be (3357 +/- 135 Torr(-1) s(-1)). The radiative life-time of the vibrational combination band (12(0)1), tau[CO2 (12(0)1)], was found to be (5.55 +/- 0.27) mu s. Modern angular momentum theory was used to explain values of the deactivation rate measured. It is concluded that the presence of the (08(0)0) state acts like an angular momentum sink leading to a fast deactivation rate of the CO2 (12(0)1) by argon. (C) 2009 Elsevier B.V. All rights reserved.
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| 47. |
- Andersson, Öivind, et al.
(författare)
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Crank Angle Resolved HC Detection Using LIF in the Exhausts of Small Two-Stroke Engines Running at High Engine Speed
- 1996
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Ingår i: SAE Transactions, Journal of Engines. - 0096-736X. ; 105:961927
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Tidskriftsartikel (refereegranskat)abstract
- In order to separate the HC-emissions from two-stroke engines into short-circuit losses and emissions due to incomplete combustion, Laser Induced Fluorescence (LIF) measurements were performed on the exhaust gases just outside the exhaust ports of two engines of different designs. The difference between the two engines was the design of the transfer channels. One engine had "finger" transfer channels and one had "cup handle" transfer channels. Apart from that they were similar. The engine with "finger" transfer channels was earlier known to give more short-circuiting losses than the other engine, and that behavior was confirmed by these measurements. Generally, the results show that the emission of hydrocarbons has two peaks, one just after exhaust port opening and one late in the scavenging phase. The spectral information shows differences between the two peaks and it can be concluded that the latter peak is due to short-circuiting and the earlier due to incomplete combustion. The flow outside the exhaust port was measured with Laser Doppler Velocimetry (LDV). These measurements confirm the occurrence of two emission peaks.
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| 48. |
- Andersson, Öivind, et al.
(författare)
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Laser-Rayleigh Imaging of DME Sprays in an Optically Accessible DI Diesel Truck Engine
- 2001
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Ingår i: SAE Technical Paper 2001-01-0915. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
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Konferensbidrag (refereegranskat)abstract
- Laser-Rayleigh imaging has been employed to measure the relative fuel concentration in the gaseous jet region of DME sprays. The measurements were performed in an optically accessible diesel truck engine equipped with a common rail injection system. A one-hole nozzle was used to guarantee that the recorded pressure history was associated with the heat release in the imaged spray. To compensate for the low compression ratio in the modified engine the inlet air was preheated. Spray development was studied for two levels of preheating, from the start of injection to the point where all fuel was consumed. The results indicate that there is a strong correlation between the amount of unburned fuel present in the cylinder and the rate of heat release at a given time. The combustion can not be described as purely premixed or purely mixing-controlled at any time, but always has an element of both. After all fuel appears to have vanished there is still an extended period of heat release. This indicates a rich combustion yielding combustible products.
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| 49. |
- Andersson, Öivind, et al.
(författare)
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Quantitative Imaging of Equivalence Ratios in DME Sprays Using a Chemically Preheated Combustion Vessel
- 2000
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Ingår i: SAE technical paper series, paper 2000-01-5785. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
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Konferensbidrag (refereegranskat)abstract
- Dimethyl Ether (DME) has proved to be a promising fuel for diesel engines. It virtually eliminates particulate emissions and reduces the formation of nitrogenous oxides, without negatively affecting engine efficiency. Obtaining a deeper understanding of the mechanisms behind these properties is thus highly desirable. Various authors have suggested that the low NO emissions associated with DME are an effect of the mixing conditions, which are thought to differ from those of diesel sprays. To examine this, laser-Rayleigh imaging was employed for quantitative measurement of the local equivalence ratios in DME sprays. The quantitative images were analyzed using a statistical approach, in which probability distributions of ϕ -values for burning and for non-reacting sprays were compared. It was concluded that the diffusion flame is established in the stoichiometeric or slightly lean regions of the spray. Measurements were performed in an isochoric combustion vessel chemically preheated by igniting a lean mixture of CO and oxygen-enriched air. A multizone combustion model was used to analyze the DME combustion and the effects of preheating on the vessel atmosphere. The benefits and drawbacks of this set-up are discussed.
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| 50. |
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