| 1. |
|
|
| 2. |
- Gallo, Yann, et al.
(författare)
-
A Study of In-Cylinder Soot Oxidation by Laser Extinction Measurements During an EGR-Sweep in an Optical Diesel Engine
- 2015
-
Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
-
Tidskriftsartikel (refereegranskat)abstract
- Two competing in-cylinder processes, soot formation and soot oxidation, govern soot emissions from diesel engines. Previous studies have shown a lack of correlation between the soot formation rate and soot emissions. The current experiment focuses on the correlation between soot oxidation rates and soot emissions. Laser extinction is measured using a red (690nm) laser beam, which is sent vertically through the cylinder. This wavelength is long enough to minimize absorption interference from poly-aromatic hydrocarbons, while still in the visible regime. It is modulated at 72 kHz in order to produce 10 pulses per crank angle degree at an engine speed of 1200 rpm. The intake oxygen concentration is varied between 9% and 21%. The time resolved extinction measurements are used to estimate soot oxidation rates during expansion. High-speed video imaging is used in conjunction with the laser-extinction technique to indicate the location of the sooting regions, and to assess beam steering effects. The oxidation processes are described using single exponential decay fits and an attempt to correlate them with the late cycle rate of heat release was made.
|
|
| 3. |
- Li, Zheming, et al.
(författare)
-
Comparison of Laser-Extinction and Natural Luminosity Measurements for Soot Probing in Diesel Optical Engines
- 2016
-
Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
-
Tidskriftsartikel (refereegranskat)abstract
- Soot emissions from diesel internal combustion engines are strictly regulated nowadays. Laser extinction measurement (LEM) and natural luminosity (NL) of sooty flames are commonly applied to study soot. LEM measures soot along the laser beam path and it can probe soot regardless of temperature. NL integrates the whole field of view and relies on soot temperature. In this work, a comparison of simultaneously recorded LEM and NL data has been performed in a heavy-duty optical engine. A 685 nm laser beam is used for LEM. The laser was modulated at 63 kHz, which facilitated subtraction of the background NL signal from the raw LEM data. By Beer-Lambert’s law, KL factor can be calculated and used as a metric to describe soot measurements. A compensation of transmitted laser intensity fluctuation and soot deposits on optical windows has been performed in this work. The data compensation successfully reduced the transmitted laser intensity fluctuation and made it possible to study in-cylinder low temperature soot residual. The KL curves were compared with NL curve in this work. In the late cycle the KL curve can successfully show the low temperature soot which is not detected by NL. The KL curve is found to rise about 2 CAD ahead of the corresponding NL curve due to liquid fuel spray disturbance. In this case, LEM is not a suitable method to calculate KL for analyzing the early soot formation if there are liquid phase fuel droplets crossing the probing laser beam.
|
|
| 4. |
- Li, Zheming, et al.
(författare)
-
Comparison of the Lift-Off Lengths Obtained by Simultaneous OH-LIF and OH∗ Chemiluminescence Imaging in an Optical Heavy-Duty Diesel Engine
- 2015. - September
-
Ingår i: 12th International Conference on Engines and Vehicles, ICE 2015. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. ; 2015-September
-
Konferensbidrag (refereegranskat)abstract
- The presence of OH radicals as a marker of the high temperature reaction region usually has been used to determine the lift-off length (LOL) in diesel engines. Both OH Laser Induced Fluorescence (LIF) and OH∗ chemiluminescence diagnostics have been widely used in optical engines for measuring the LOL. OH∗ chemiluminescence is radiation from OH being formed in the exited states (OH∗). As a consequence OH∗ chemiluminescence imaging provides line-of-sight information across the imaged volume. In contrast, OH-LIF provides information on the distribution of radicals present in the energy ground state. The OH-LIF images only show OH distribution in the thin cross-section illuminated by the laser. When both these techniques have been applied in earlier work, it has often been reported that the chemiluminescence measurements result in shorter lift-off lengths than the LIF approach. In order to investigate this discrepancy this work presents a dedicated comparison of the LOL obtained from these two diagnostic techniques. In diesel engines, the cycle-to-cycle variations in lift-off region are usually significant. To avoid misinterpretations caused by these variations simultaneous measurements are needed. The statistical analysis based on our simultaneous data can conclude that the OH-LIF method yields longer LOL than the OH∗ chemiluminescence method by a smaller sample size and more precisely than non-simultaneous data. This can be partially explained by the 3D geometry and flame axis asymmetry effects. A numerical simulation with OH and OH∗ distribution was performed for the comparison. It shows a great agreement with the experimental results in this study.
|
|
| 5. |
- Lind, Hans, 1950-, et al.
(författare)
-
Real estate management in the Swedish public sector
- 2005
-
Ingår i: Journal of Corporate Real Estate. - : Emerald. - 1463-001X .- 1479-1048. ; 7:2, s. 178-190
-
Tidskriftsartikel (refereegranskat)abstract
- The Swedish central government has implemented a radical market-oriented reform of its real estate management. Authorities are free to rent premises from private firms, and stateowned properties have been allocated to a number of entities that lease their properties to authorities on conditions similar to those on the open market. The background and experience from these reforms are described in this paper. Local authorities and county councils have also reformed their real estate management systems in the same direction, but not as radically. There were many unexpected problems with implementing these systems, related for example to difficulties in writing good contracts for special purpose buildings, conflicts about rent setting and differences in bargaining power between the property-owning units and the tenants/authorities. The general view is, however, that the reform created necessary economic incentives for the authorities in the public sector to economise on premises, but that it is very important to think through the details and to adjust the system to changing circumstances. An example is that the introduction of school vouchers created problems for some systems of setting internal asset rents.
|
|
| 6. |
- Lind, Ted
(författare)
-
Application and Development of Optical Soot Diagnostic Techniques
- 2018. - 1
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Internal combustion engines (ICE) have been a vital part of society ever since their inception more than a hundred years ago. While initially it seemed as if the replacement of horse and carriage had solved the issue with pollutant emissions, it became evident in the 60’s that emission from ICEs is a major concern. The first emissions in focus were the nitrogen oxides (NOx). Lately, however, focus has shifted towards emissions which affect the global warming trends. The two worst pollutants, with respect to global warming, are carbon dioxide and soot. The main focus of this thesis is the study of soot processes in optical diesel engines as well as development of optical soot diagnostics. While the diesel engine is favoured due to its high fuel efficiency, and therefore low CO2 emissions, it does suffer from higher soot emissions than the spark ignition engine. Soot emission is the net result of two competing processes; soot formation and soot oxidation. Soot oxidation processes have previously been shown to determine the trends of soot emissions for conventional diesel combustion and for that reason this thesis puts more focus on these. Another known fact is that injections of fuel after the main injection, so called post injections, have been shown to reduce soot emissions. However, exactly how this works is not clear. In this thesis we elucidate the mechanisms of post injection soot reduction with the use of a novel soot diagnostic technique called diffuse back-illumination extinction imaging. Using this technique it is revealed that one of the reasons behind the soot reduction of post injections is that most or all of the soot that is formed by a short post injection is also oxidized, thus leading to no net emissions. The oxidation process is especially enhanced due to the increased mixing which occurs in the jet as the injector closes. Lastly, a new soot thermometry technique based on the DBI technique is developed. By directly measuring the amount of soot within a flame with an active technique such as DBI, many of the uncertainties associated with conventional optical thermometry techniques such as two color pyrometry can be avoided.
|
|
| 7. |
- Lind, Ted, et al.
(författare)
-
Diffuse back-illumination temperature imaging (DBI-TI), a novel soot thermometry technique
- 2022
-
Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 240
-
Tidskriftsartikel (refereegranskat)abstract
- To meet stringent emissions regulations on soot emissions, it is critical to further advance the fundamental understanding of in-cylinder soot formation and oxidation processes. Among several optical techniques for soot quantification, diffuse back-illumination extinction imaging (DBI-EI) has recently gained traction mainly due to its ability to compensate for beam steering, which if not addressed, can cause unacceptably high measurement uncertainty. Until now, DBI-EI has only been used to measure the amount of soot along the line of sight, and in this work, we extend the capabilities of a DBI-EI setup to also measure in-cylinder soot temperature. This proof of concept of diffuse back-illumination temperature imaging (DBI-TI) as a soot thermometry technique is presented by implementing DBI-TI in a single cylinder, heavy-duty, optical diesel engine to provide 2-D line-of-sight integrated soot temperature maps. The potential of DBI-TI to be an accurate thermometry technique for use in optical engines is analyzed. The achievable accuracy is due in part to simultaneous measurement of the soot extinction, which circumvents the uncertainty in dispersion coefficients that depend on the optical properties of soot and the wavelength of light utilized. Analysis shows that DBI-TI provides temperature estimates that are closer to the mass-averaged soot temperature when compared to other thermometry techniques that are more sensitive to soot temperature closer to the detector. Furthermore, uncertainty analysis and Monte Carlo (MC) simulations provide estimates of the temperature measurement errors associated with this technique. The MC simulations reveal that for the light intensities and optical densities encountered in these experiments, the accuracy of the DBI-TI technique is comparable or even better than other established optical thermometry techniques. Thus, DBI-TI promises to be an easily implementable extension to the existing DBI-EI technique, thereby extending its ability to provide comprehensive line-of-sight integrated information on soot.
|
|
| 8. |
- Lind, Ted, et al.
(författare)
-
Mechanisms of Post-Injection Soot-Reduction Revealed by Visible and Diffused Back-Illumination Soot Extinction Imaging
- 2018
-
Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2018-April
-
Tidskriftsartikel (refereegranskat)abstract
- Small closely-coupled post injections of fuel in diesel engines are known to reduce engine-out soot emissions, but the relative roles of various underlying in-cylinder mechanisms have not been established. Furthermore, the efficacy of soot reduction is not universal, and depends in unclear ways on operating conditions and injection schedule, among other factors. Consequently, designing engine hardware and operating strategies to fully realize the potential of post-injections is limited by this lack of understanding. Following previous work, several different post-injection schedules are investigated using a single-cylinder 2.34 L heavy-duty optical engine equipped with a Delphi DFI 1.5 light-duty injector. In this configuration, adding a closely-coupled post injection with sufficiently short injection duration can increase the load without increasing soot emissions. With increasing post-injection duration, the plateau in soot emissions eventually turns upward until the post-injection increases engine-out soot above that for a single-injection strategy at the same load and main injection timing. To gain more insight into in-cylinder processes affecting soot with post-injections, a new optical diagnostic technique is utilized. Diffused back-illumination imaging (DBI) of soot extinction has previously been used in a high-pressure constant volume vessel, but has not yet been reported in the literature for heavy-duty engines. The DBI setup developed for this experiment enables quantitative 2-dimensional (2D) line-of-sight optical thickness (KL) measurements from soot extinction with a temporal resolution of 42 kHz. The high temporal resolution and relatively large field of view (FoV) quantifies the evolution of in-cylinder soot for roughly the downstream half of one diesel jet of the multi-hole injector throughout each cycle. The DBI imaging reveals that at these operating conditions, when the post injection is sufficiently short, the majority of the soot in the post injection is oxidized, thus allowing for increased load with similar soot emissions compared to a single-injection condition. A transient increase in entrainment that occurs after the end of injection (the "entrainment wave") is a candidate explanation for the observed completeness of post-injection soot oxidation. Additionally, semi-quantitative comparisons of soot KL and natural luminosity (NL) trends reveal decreasing KL accompanied by increasing NL. This observation is consistent with an increase in post-injection soot temperature after the end of the post injection, which may further aid oxidation.
|
|
| 9. |
- Lind, Ted, et al.
(författare)
-
Simultaneous PLIF Imaging of OH and PLII Imaging of Soot for Studying the Late-Cycle Soot Oxidation in an Optical Heavy-Duty Diesel Engine
- 2016
-
Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 9:2, s. 849-858
-
Tidskriftsartikel (refereegranskat)abstract
- The effects of injection pressure and swirl ratio on the in-cylinder soot oxidation are studied using simultaneous PLIF imaging of OH and LII imaging of soot in an optical diesel engine. Images are acquired after the end of injection in the recirculation zone between two adjacent diesel jets. Scalars are extracted from the images and compared with trends in engine-out soot emissions. The soot emissions decrease monotonically with increasing injection pressure but show a non-linear dependence on swirl ratio. The total amount of OH in the images is negatively correlated with the soot emissions, as is the spatial proximity between the OH and soot regions. This indicates that OH is an important soot oxidizer and that it needs to be located close to the soot to perform this function. The total amount of soot in the images shows no apparent correlation with the soot emissions, indicating that the amount of soot formed is a poor predictor of the emission trends.
|
|
| 10. |
|
|
