| 1. |
- Andersson, Mats, 1963, et al.
(författare)
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Application of laser-induced fluorescence for imaging of model fuels emulating gasoline and gasoline/ethanol blends
- 2009
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Ingår i: Proceedings of ICLASS 2009, 11th International Congress on Liquid Atomization and Spray Systems. ; , s. ICLASS2009-189
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Konferensbidrag (refereegranskat)abstract
- The performance at cold start of spark-ignited car engines is still a challenge since slow and incomplete vaporization of the fuel causes high emissions of unburned hydrocarbons and may even cause difficulties to start at very low temperatures, in particular with alternative fuels such as ethanol. One approach to improve fuel evaporation is by direct injection into the cylinder late during the compression stroke. In this study the evaporation of fuel, including selective evaporation of fuel components of different volatility, has been studied, in sprays injected into air with a controlled pressure and temperature. Planar laser-induced fluorescence (PLIF) and Mie scattering were used to image the fuel distribution in vapor and liquid phase in a cross-section of sprays. A model fuel of non-fluorescent molecules was used and a fluorescent tracer molecule was added. To simulate a fuel with a distillation curve similar to gasoline a multi-component model fuel was selected. The fuel was composed of five iso- or cyclo-alkenes with boiling points that span the 30-190°C range. As fluorescence tracers ketones: acetone, 3-pentanone and methylcyclohexanone, were used to trace light, medium-heavy and heavy fuel fractions. Besides investigating the gasoline-like model fuel, ethanol and an etha-nol/multi-components fuel blend were investigated. Spray imaging was carried out in a pressurized chamber. The injector was an outward-opening piezo-actuated injector generating a hollow-cone spray. A cross-section of the spray was illuminated by laser light at a wavelength of 266 nm formed into a thin sheet. Two intensified CCD-cameras were used to detect fluorescence and scattered light. The presence and penetration of liquid was determined by detecting Mie-scattered light. The PLIF-images provided the total distribution of fuel in liquid and vapor phase, and by comparing with the Mie-images it could be determined when the vapor started to appear in areas with little or no drops present indicating the presence of fuel vapor. It was found that at 90°C the light fuel components evaporated quickly, the medium-heavy components slowly while the heavy ones remained in liquid phase. At 140°C also the medium-heavy components evaporate relatively rapidly.
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| 2. |
- Andersson, Mats, 1963, et al.
(författare)
-
Application of laser-induced fluorescence for imaging sprays of model fuels emulating gasoline and gasoline/ethanol blends
- 2009
-
Ingår i: 11th International Annual Conference on Liquid Atomization and Spray Systems 2009, ICLASS 2009. - 9781617826535
-
Konferensbidrag (refereegranskat)abstract
- The performance at cold start of spark-ignited car engines is still a challenge since slow and incomplete vaporization of the fuel causes high emissions of unburned hydrocarbons and may even cause difficulties to start at very low temperatures, in particular with alternative fuels such as ethanol. One approach to improve fuel evaporation is by direct injection into the cylinder late during the compression stroke. In this study the evaporation of fuel, including selective evaporation of fuel components of different volatility, has been studied, in sprays injected into air with a controlled pressure and temperature. Planar laser-induced fluorescence (PLIF) and Mie scattering were used to image the fuel distribution in vapor and liquid phase in a cross-section of sprays. A model fuel of non-fluorescent molecules was used and a fluorescent tracer molecule was added. To simulate a fuel with a distillation curve similar to gasoline a multi-component model fuel was selected. The fuel was composed of five iso- or cyclo-alkenes with boiling points that span the 30-190°C range. As fluorescence tracers ketones: acetone, 3-pentanone and methylcyclohexanone, were used to trace light, medium-heavy and heavy fuel fractions. Besides investigating the gasoline-like model fuel, ethanol and an ethanol/multi-components fuel blend were investigated. Spray imaging was carried out in a pressurized chamber. The injector was an outward-opening piezo-actuated injector generating a hollow-cone spray. A cross-section of the spray was illuminated by laser light at a wavelength of 266 nm formed into a thin sheet. Two intensified CCD-cameras were used to detect fluorescence and scattered light. The presence and penetration of liquid was determined by detecting Mie-scattered light. The PLIF-images provided the total distribution of fuel in liquid and vapor phase, and by comparing with the Mie-images it could be determined when the vapor started to appear in areas with little or no drops present indicating the presence of fuel vapor. It was found that at 90°C the light fuel components evaporated quickly, the medium-heavy components slowly while the heavy ones remained in liquid phase. At 140°C also the medium-heavy components evaporate relatively rapidly.
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| 3. |
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| 4. |
- Hemdal, Stina, 1974, et al.
(författare)
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Stratified cold start sprays of gasoline-ethanol blends
- 2009
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Ingår i: SAE International Journal of Fuels and Lubricants. - : SAE International. - 1946-3952 .- 1946-3960. ; 2:1, s. 683-696
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Tidskriftsartikel (refereegranskat)abstract
- Gasoline and gasoline-ethanol sprays from an outward-opening piezo-injector were studied in a constant volume/pressure chamber using high-speed imaging and phase doppler anemometry (PDA) under stratified cold start conditions corresponding to a vehicle ambient temperature of 243 K (-30 °C/-22 °F); in-cylinder air pressure of 5 bar, air temperature of 350 K (-30 °C/-22 °F) and fuel temperature of 243 K. The effects of varying in-cylinder pressure and temperature, fuel injection pressure and fuel temperature on the formation of gasoline, E75 and pure ethanol sprays were investigated. The results indicate that fuel composition affects spray behaviour, but less than expected. Furthermore, varying the temperature of the fuel or the air surrounding the spray also had minor effects. As expected, the fuel injection pressure was found to have the strongest influence on spray formation under stratified conditions.
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| 5. |
- Wärnberg, Jonas, 1978
(författare)
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Hollow cone gasoline/ethanol sprays under cold start conditions
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To decrease the release of CO2 from fossil fuels into the atmosphere, within the transportation sector the efficiency of vehicles and their engines must be increased. Additionally renewable fuels may be used to further decrease our reliance on fossil fuels. One such fuel is ethanol which presently, in low quantities, is mixed into all gasoline presently sold in Europe. In higher quantity mix-in it is sold under the name E85 (85% ethanol, 15% gasoline) and vehicles able to run on this fuel are subject to lower tax in Sweden. The E85 vehicles do suffer from poor startability in cold conditions even though winter grade E85 contains 25% gasoline to improve starting performance.To improve the thermal efficiency of Otto-engines, direct injection can be applied. By injecting the fuel directly into the cylinder all fuel will evaporate inside the combustion chamber and thereby lower combustion chamber temperatures. This allows for higher compression ratio, bigger spark advance and/or higher boost levels. Furthermore, by stratifying the charge at low and medium load, the efficiency of the engine can be further increased due to lower throttling losses and less heat losses.By applying a stratified starting strategy the aim to start with high levels of ethanol in the fuel even at very low temperatures may be accomplished. In this thesis the performance of outward-opening, piezo-controlled direct injectors is investigated in constant pressure gas chambers using different fuels. The influence of different chambers conditions, fuel pressure and temperature as well as different injection strategies is evaluated.From these investigations, the injection pressure was found to be the most important factor influencing the structure of the spray. A spray injected at a high pressure into a moderately high pressure environment will break up into a compact fuel cloud which entrains air from outside through vortices shaped by the break-up. At the same time the mentioned vortices keep the fuel droplets and vapour from propagating outside of the cloud structure.A comparison between gasoline and ethanol gave that while the lightest compounds of gasoline evaporates quickly already at 90°C chamber air temperature, the temperature of the air needs to be increased to 200°C at constant gas density for ethanol to evaporate at a similar rate. Hence, to achieve a stratified cold start on neat ethanol under otherwise similar conditions to gasoline the compression ratio must be increased to gain more in temperature during the compression.As a final test, laser ignition was successfully applied on neat ethanol sprays under conditions similar to those valid for a -30°C arctic cold start.
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| 6. |
- Wärnberg, Jonas, 1978, et al.
(författare)
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Ignitability of hollow cone gasoline/gasoline-ethanol sprays
- 2009
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Ingår i: 18. Aachener Kolloquium, Fahrzeug- und Motorentechnik. ; 1, s. 413-450
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Powering vehicles by a fuel-blend of ethanol and gasoline (E85) is being considered as one of various possible ways to decrease fossil carbon dioxide emissions. There is great potential to both improve power and increase energy conversion efficiency using such blends in combination with direct injection by modern outward-opening piezo-actuated injectors. However, cold starts when using mixtures with high ethanol contents are problematic. This report presents results of ongoing observations of sprays from a piezo-injector under conditions similar to those that would be encountered in-cylinder during cold starts at -30°C (243 K) ambient temperatures.Sprays of several fuels (gasoline, E75 and neat ethanol) have been monitored in a constant pressure, constant temperature spray chamber by both laser-induced fluorescence, to obtain understanding of the fuel vaporization process, and particle image velocimetry to map flow velocities and vortex formation inside the sprays and fuel clouds formed by their atomisation. In addition, the ignitability of the ethanol fuel sprays has been evaluated using focused laser light to obtain indications of the likelihood that similar sprays could be ignited in a real engine.As expected, under the test conditions ethanol evaporates more slowly than the lighter components of gasoline. In experiments at various temperatures, with constant air density, the vortex structure inside ethanol fuel clouds varied substantially between cycles, but remained similar. The clouds consistently formed toroid shapes in which two counter-rotating vortices developed, and the first traces of vapour appeared at the centres of these vortices. In addition, the laser ignition tests showed that under possible in-cylinder conditions with a fairly high compression ratio (~12:1) it would be possible to ignite a stratified neat ethanol spray.
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