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Technical Paper

Effects of Group-hole Nozzle Specifications on Fuel Atomization and Evaporation of Direct Injection Diesel Sprays

2007-07-23
2007-01-1889
The group-hole nozzle concept is regarded as a promising approach to facilitate better fuel atomization and evaporation for direct injection diesel engine applications. In the present work, the spray and mixture properties of group-hole nozzle with close, parallel or a small included angle orifices were investigated experimentally by means of the ultraviolet-visible laser absorption-scattering (LAS) imaging technique, in comparison with the conventional single-hole nozzle. Three series of group-hole nozzles were designed to investigate the effect of group-hole nozzle specification while varying the included angle and interval between the orifices. The results suggested that: 1) Group-hole nozzle with very close, parallel orifices presents the similar spray characteristics with those of the single-hole nozzle.
Technical Paper

Group-Hole Nozzle Effects on Mixture Formation and In-cylinder Combustion Processes in Direct-Injection Diesel Engines

2007-10-29
2007-01-4050
The group-hole (GH) nozzle concept that uses two closely spaced micro-orifices to substitute the conventional single orifice has the potential to facilitate better fuel atomization and evaporation, consequently attenuate the soot emission formed in direct-injection (D.I.) diesel engines. Studies of quantitative mixture properties of the transient fuel spray injected by the group-hole nozzles were conducted in a constant volume chamber via the laser absorption-scattering (LAS) technique, in comparison with conventional single-hole nozzles. Specific areas investigated involved: the non-evaporating and the evaporating ambient conditions, the free spray and the spray impinging on a flat wall conditions. The particular emphasis was on the effect of one of key parameters, the interval between orifices, of the group-hole (SH) nozzle structure.
Technical Paper

Mixture Formation and Combustion Processes of Multi-Hole Nozzle with Micro Orifices for D.I. Diesel Engines

2007-10-29
2007-01-4049
In order to investigate effects of the multi-hole nozzle with micro orifices on mixture formation processes in Direct-Injection Diesel engines, mixture characteristics were examined via an ultraviolet-visible laser absorption scattering (LAS) technique under various injectors. The injection quantity per orifice per cycle was reduced by nozzle hole sizes. The LAS technique can provide the quantitative and simultaneous measurements of liquid and vapor phases concentration distributions inside of the fuel spray. Mass of ambient gas entrained into the spray, liquid/ vapor mass and mean equivalence ratio of total fuel were obtained based on Lambert Beer's law. As a result, the leaner and more homogeneous fuel-gas mixture can be achieved by reducing the nozzle hole diameter, in the meanwhile more ambient gas were entrained into the spray. Moreover, relationships between mixture formation and D.I.
Technical Paper

An Experimental Study on Mixture Formation Process of Flat Wall Impinging Spray Injected by Micro-Hole Nozzle under Ultra-High Injection Pressures

2008-06-23
2008-01-1601
Increasing injection pressure and decreasing nozzle hole diameter have been proved to be two effective approaches to reduce the exhaust emissions and to improve the fuel economy. Recently, the micro-hole nozzles and ultra-high injection pressures are applicable in commercial Diesel engines. But the mechanism of these two latest technologies is still unclear. The current research aims at providing information on the spray and mixture formation processes of the micro-hole nozzle (d=0.08mm) under the ultra-high injection pressure (Pinj=300MPa). The flat wall impinging sprays were focused on and the laser absorption-scattering (LAS) technique was employed to obtain the qualitative and quantitative information at both atmospheric and elevated conditions. The spray parameters were collected, the mixing rate was discussed, and the effects of various parameters on mixture formation were clarified.
Technical Paper

Characteristics of Nozzle Internal Flow and Near-Field Spray of Multi-Hole Injectors for Diesel Engines

2015-09-01
2015-01-1920
The combustion process, emission formation and the resulting engine performance in a diesel engine are well known to be governed mainly by spray behaviors and the consequent mixture formation quality. One of the most important factors that affect the spray development is the nozzle configuration. Originally, single-hole diesel injector is usually applied in fundamental research to provide insights into the spray characteristics. However, the spray emerging from a realistic multi-hole injector approaches the practical engine operation situation better. Meanwhile, previous research has shown that the reduced nozzle hole diameter is effective for preparing more uniform mixture. In the current paper, a study about the effects of nozzle configuration and hole diameter on the internal flow and spray properties was conducted in conjunction with a series of experimental and computational methods.
Journal Article

Ignition and Combustion Characteristics of Wall-Impinging Sprays Injected by Group-Hole Nozzles for Direct-Injection Diesel Engines

2008-10-06
2008-01-2469
The concept of two closely spaced micro-orifices (group hole nozzle) has been studied as a promising technology for the reduction of soot emission from direct injection (DI) diesel engines by improving the fuel atomization and evaporation. One of the main issues on group hole nozzle is the arrangement of orifices with various distances and angles. In this study, the ignition and combustion characteristics of wall-impinging diesel sprays from group-hole nozzles were investigated with various angles between two micro-orifices (included angles). A laser absorption scattering (LAS) technique for non-axisymmetric sprays, developed based on a LAS technique for axisymmetric spray, was applied to investigate the liquid/vapor mass distribution of wall-impinging sprays. The direct flame images and OH radical images inside a high pressure constant volume vessel were captured to analyze the effect of included angle on spray ignition and combustion characteristics.
Journal Article

Characteristics of Evaporating Diesel Spray: A Comparison of Laser Measurements and Empirical/Theoretical Predictions

2009-04-20
2009-01-0854
The objective of the paper is to characterize the diesel spray under the ambient conditions relevant for direct injection (D.I.) diesel engines. The particular emphasis is on the comparisons between laser measurements and predictions by empirical correlations and theoretical analyses. The ultraviolet-visible laser absorption-scattering (LAS) imaging technique is employed to quantitively determine the spray/mixture properties of the diesel spray injected by a hole-type injector, in terms of spray tip penetration and spatial concentration distributions of liquid and vapor phase. The structure of evaporating spray is obtained and analyzed. Based on the penetration correlations in the literature, a non-dimensional analysis of the spray tip penetration data is carried out. The results indicate that a self-similar state of the evaporating fuel spray is achieved.
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