The Experts below are selected from a list of 402 Experts worldwide ranked by ideXlab platform

Ingemar Denbratt - One of the best experts on this subject based on the ideXlab platform.

  • ignitability of hollow cone gasoline gasoline ethanol sprays
    18. Aachener Kolloquium Fahrzeug- und Motorentechnik, 2009
    Co-Authors: Jonas Warnberg, Stina Hemdal, Mats Andersson, Petter Dahlander, Ingemar Denbratt
    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.

  • operation of a di diesel engine with variable effective compression ratio in hcci and conventional diesel mode
    SAE transactions, 2005
    Co-Authors: Arjan Helmantel, Jonas Gustavsson, Ingemar Denbratt
    Abstract:

    An experimental investigation was carried out in which an HSDI Common Rail Diesel engine was operated in both HCCI and conventional Diesel combustion modes, using conventional Diesel fuel in both cases. The engine used in the experiments was a single cylinder version of a modem passenger car engine with a displacement of 480 cc. In HCCI mode, the fuel was injected in multiple stages during the compression stroke, using a nozzle with a 60° included angle. To control the phasing and rate of combustion, the elective compression ratio was reduced by retarded intake valve closing. In addition, increased amounts of EGR were used. HCCI operation reduced soot and NO, emissions significantly. The use of a narrow included angle for conventional Diesel operation increased emissions significantly. The effect of a wider included angle and modifications to the piston were investigated experimentally and numerically. HCCI operation was also possible with a Piezo Injector with a 140° included angle. Because of the more accurate, shorter injections allowed by the Piezo Injector, interaction of the spray with the cylinder liner could be avoided, despite the wide included angle.

  • Exploration of the Load Range of HCCI Operation of a DI Diesel Engine
    2005
    Co-Authors: Arjan Helmantel, Ingemar Denbratt
    Abstract:

    A passenger car type DI Common Rail Diesel engine was operated in HCCI mode in a load range from 0.1 to 0.5 MPa IMEP and an engine speed range from 1000 to 2500 rpm. Conventional Diesel fuel was injected in up to six subsequent injections during the compression stroke by a Piezo Injector. For most load cases, soot and NOx emissions were reduced to near zero levels, but HC and CO emissions were significantly higher, when compared to conventional Diesel operation. The improved accuracy of the Piezo Injector enabled short injections and consequently short spray penetration lengths, which made it possible to use a nozzle with a wide included angle, without excessive cylinder liner wetting. Maintaining the wide included angle meant that operation of the same engine in Diesel operation was not compromised by the Injector geometry. EGR and the intake valve closing angle were used as control parameters to properly phase the combustion. Delaying the intake valve closing angle to 90 CAD BTDC reduced the effective compression ratio which allowed the EGR rate to be reduced.

N Peters - One of the best experts on this subject based on the ideXlab platform.

  • simulation of combustion in direct injection diesel engines using a eulerian particle flamelet model
    Proceedings of the Combustion Institute, 2000
    Co-Authors: H Barths, Christian Hasse, Georgios Bikas, N Peters
    Abstract:

    An overview of flamelet modeling for turbulent non-premixed combustion is given. A short review of previous contributions to simulations of direct injection (DI) diesel engine combustion using the representative interactive flamelet concept is presented. A surrogate fuel consisting of 70% (liquid volume) n -decane and 30% α -methylnaphthalene is experimentally compared to real diesel fuel. The similarity of their physical and chemical properties is shown to result in a very similar combustion process for both fuels. The mathematical derivation for the Eulerian particle flamelet model is outlined. A strategy based on physical arguments is described for subdividing the computational domain and assigning these domains to different flamelet histories associated with Eulerian marker particles. For each of these marker particles, a transport equation has to be solved. Experiments conducted with an Audi DI diesel engine equipped with a Piezo Injector and running with diesel fuel are compared to simulations using the surrogate fuel. The use of multiple flamelets, each having a different history, significantly improves the description of the ignition phase, leading to a better prediction of pressure, heat release, and exhaust emissions such as soot and NO x . The effect of the number of flamelet particles on the predictions is discussed.

Denbratt Ingemar - One of the best experts on this subject based on the ideXlab platform.

  • Stratified cold start sprays of gasoline-ethanol blends
    2009
    Co-Authors: Hemdal Stina, Dahlander Petter, Denbratt Ingemar, Wärnberg Jonas
    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

  • Ignitability of hollow cone gasoline/gasoline-ethanol sprays
    2009
    Co-Authors: Wärnberg Jonas, Dahlander Petter, Hemdal Stina, Andersson Mats, Denbratt Ingemar
    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

Wärnberg Jonas - One of the best experts on this subject based on the ideXlab platform.

  • Stratified cold start sprays of gasoline-ethanol blends
    2009
    Co-Authors: Hemdal Stina, Dahlander Petter, Denbratt Ingemar, Wärnberg Jonas
    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

  • Ignitability of hollow cone gasoline/gasoline-ethanol sprays
    2009
    Co-Authors: Wärnberg Jonas, Dahlander Petter, Hemdal Stina, Andersson Mats, Denbratt Ingemar
    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

H Barths - One of the best experts on this subject based on the ideXlab platform.

  • simulation of combustion in direct injection diesel engines using a eulerian particle flamelet model
    Proceedings of the Combustion Institute, 2000
    Co-Authors: H Barths, Christian Hasse, Georgios Bikas, N Peters
    Abstract:

    An overview of flamelet modeling for turbulent non-premixed combustion is given. A short review of previous contributions to simulations of direct injection (DI) diesel engine combustion using the representative interactive flamelet concept is presented. A surrogate fuel consisting of 70% (liquid volume) n -decane and 30% α -methylnaphthalene is experimentally compared to real diesel fuel. The similarity of their physical and chemical properties is shown to result in a very similar combustion process for both fuels. The mathematical derivation for the Eulerian particle flamelet model is outlined. A strategy based on physical arguments is described for subdividing the computational domain and assigning these domains to different flamelet histories associated with Eulerian marker particles. For each of these marker particles, a transport equation has to be solved. Experiments conducted with an Audi DI diesel engine equipped with a Piezo Injector and running with diesel fuel are compared to simulations using the surrogate fuel. The use of multiple flamelets, each having a different history, significantly improves the description of the ignition phase, leading to a better prediction of pressure, heat release, and exhaust emissions such as soot and NO x . The effect of the number of flamelet particles on the predictions is discussed.