Analysis of Flow and Cavitation Phenomena in Diesel Injection Nozzles and Its Effects on Spray and Mixture Formation

2003 ◽  
Author(s):  
M. Blessing ◽  
G. König ◽  
C. Krüger ◽  
U. Michels ◽  
V. Schwarz
Keyword(s):  
Mixture Formation ◽  
Diesel Injection

Characterization of the distribution-nozzle operation for mixture homogenization by a late-diesel-injection strategy

2011 ◽  
Vol 226 (4) ◽  
pp. 529-546 ◽  
Author(s):  
M Weclas ◽  
J Cypris
Keyword(s):  
Combustion Process ◽  
Injection Pressure ◽  
Ignition Timing ◽  
Mixture Formation ◽  
Penetration Length ◽  
Injection Strategy ◽  
Fuel Distribution ◽  
Diesel Injection ◽  
Fuel Vaporization ◽  
Homogeneous Combustion

In order to realize a homogeneous combustion process it is necessary to decouple this combustion process from fuel injection. This homogeneous combustion process requires the charge to be homogeneous prior to simultaneous volumetric ignition. This kind of ignition is a self-ignition process requiring control of the ignition timing. A late-injection strategy as used in a conventional diesel engine permits control of the ignition timing; however, the time available for mixture formation and the homogenization process is very limited. The present paper deals with a distribution-nozzle concept which combines both strategies: a late-injection strategy for controlling the ignition timing with significantly accelerated fuel distribution in space and corresponding mixture homogenization. The distribution-nozzle concept combines a conventional diesel nozzle with a porous element (ring) positioned in proximity to the nozzle outlet. Because of multi-jet splitting as a result of the diesel-jet interaction with a porous structure, the fuel leaving the porous ring spreads widely in space. Additionally, a very effective fuel vaporization process occurs within the porous structure, supporting quick mixture formation. The paper describes both the fuel distribution in space and its vaporization for different configurations of the distribution elements, the injection pressure, and the porous ring temperature. In comparison with a free diesel injection, the distribution nozzle results in a significantly increased fuel surface area, a reduced jet penetration length, a reduced jet velocity, and very quick fuel vaporization. This process is three dimensional in nature. Depending on the distribution-element structure, the geometry, and its temperature, as well as the injection pressure, the contributions of multi-jet splitting, and fuel vaporization, are different with respect to the surface area, penetration length, and exit velocity, as well as intensity distribution. Generally, at higher injection pressures these parameters are less temperature dependent, except for the fact that the intensity distribution is a function of the fuel vapour’s concentration.

A Computational Study of HCCI Engine With External Mixture Formation Technique

2014 ◽  
Author(s):  
T. Karthikeya Sharma ◽  
G. Amba Prasad Rao ◽  
Madhu Murthy Kotha
Keyword(s):  
Computational Study ◽  
Nox Emissions ◽  
Mixture Formation ◽  
Gasoline Engines ◽  
Hcci Engine ◽  
Velocity Magnitude ◽  
Hcci Combustion ◽  
Numerical Studies ◽  
Diesel Injection ◽  
Formation Technique

HCCI combustion is gaining increased attention amongst the research community to make it viable in both diesel and gasoline engines. Of late, technique of External mixture formation is being adopted to avoid the problems associated with the early injection and late injections of the direct injected diesel HCCI engine. This paper reports the numerical studies on the effect of External mixture formation using three-zone extended coherent flame (ECFM-3Z) CFD model of the STAR - CD package. Firstly, the results obtained through package were validated with the results available in the literature. Trade-off between HC, CO and NOx was clearly observed through simulation. The simulation results revealed decrease in in-cylinder pressures and NOx emissions with increase in EGR concentration. There is an under prediction of NOx emissions when compared with the experimental results. However, a significant reduction in NOx emissions was observed with external mixture formation, usage compared to direct diesel injection. In case of HC and CO emissions increasing trend was observed with increase in EGR concentration. Increase in HC and CO emissions was observed with external mixture formation when compared with a direct diesel injection. Also, reduction in turbulent kinetic energy and velocity magnitude levels were observed with increase in EGR concentration. Improved piston work is resulted at lower EGR concentrations. Studies revealed that for a given combustion bowl geometry, It is concluded that external mixture formation technique could be adopted to achieve HCCI combustion.

ANALYSIS OF THE POSSIBILITIES OF REGULATING THE PROCESS OF MIXTURE FORMATION IN MICROJET BURNERS WITH CYLINDRICAL FLAME STABILIZERS

2017 ◽  
Author(s):  
Nataliia Fialko ◽  
◽  
Viktor Prokopov ◽  
Julii Sherenkovskiy ◽  
Oleksandra Tymoshchenko ◽  
...  
Keyword(s):  
Mixture Formation
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