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Technical Paper

Cross-Flow Effect on Behavior of Fuel Spray Injected by Hole-Type Nozzle for D.I. Gasoline Engine

2013-10-14
2013-01-2553
Spray characteristics are of great importance to achieve fuel economy and low emissions for a D.I. gasoline engine. In this study, the characteristics of the fuel spray as well as its interaction with a cross-flow were investigated. The fuel was injected by a VCO injector into an optically accessible rectangular wind tunnel under the normal temperature and pressure, in which the direction of the injection was perpendicular to the direction of the cross-flow. The velocity of the cross-flow varied from 0 to 10 m/s while the injection pressure was 5 and 10 MPa. With using the high speed video camera and the PIV system, the spray profile, velocity distribution and the penetration distance were measured. The lower penetration distance can be obtained with the lower injection pressure and the increased velocity of the cross-flow, however the injected fuel expands along the direction of the cross-flow, which indicates that spray atomization and mixing of fuel and air are enhanced.
Technical Paper

Effects of Nozzle Hole Diameter and Injection Pressure on Flame Lift-Off and Soot Formation in D.I. Diesel Combustion

2011-08-30
2011-01-1813
Previous research has shown that the reduced nozzle hole diameter and elevated injection pressure are effective for preparing a uniform fuel-air mixture in a direct injection (D.I.) Diesel engine. A micro-hole nozzle with a hole diameter of 0.08 mm and an ultra-high injection pressure of 300 MPa have been employed to investigate the mixture formation process under various conditions. The aim of the current work is to clarify the effect of nozzle hole diameter and injection pressure on flame lift-off and soot formation processes. The free sprays from the micro-hole and conventional nozzles were investigated at a high-temperature, high-pressure constant volume vessel. A high-speed video camera system was employed to record the non-vaporizing sprays and combustion. The direct photography of OH chemiluminescence was used to provide information about the high temperature combustion process and to measure the flame lift-off length.
Technical Paper

Effects of Injection Pressure and Ambient Gas Density on Fuel - Ambient Gas Mixing and Combustion Characteristics of D.I. Diesel Spray

2011-08-30
2011-01-1819
The fuel-ambient gas interaction process of the free diesel spray injected from the micro-hole nozzle (0.08 mm) into the quiescent and engine-like ambient gas condition was investigated by means of the laser-induced fluorescence - particle image velocimetry (LIF-PIV) technique in non-evaporating condition. Direct photography with high speed video camera and two color pyrometry were applied to analyze the evaporation spray and flame characteristics. Three injection pressures from 100, 200 to 300 MPa and two ambient gas densities of 11 and 15 kg/m₃ were selected as testing conditions. The entrained mass flow rate of the ambient gas through the whole spray boundary, the ratio of the total ambient gas entrainment rate to the fuel injection rate, etc., were calculated by using the ambient gas velocity data obtained by the LIF-PIV technique and used to correlate the combustion behavior.
Journal Article

Effect of Spray/Wall Interaction on Diesel Combustion and Soot Formation in Two-Dimensional Piston Cavity

2013-10-15
2013-32-9021
The effects of spray/wall interaction on diesel combustion and soot formation in a two-dimensional piston cavity were studied with a high speed color video camera in a constant volume combustion vessel. The two-dimensional piston cavity was applied to generate the impinging spray flame. In the cavity, the flat surface which plays a role as the cylinder head has a 13.5 degree angle with the injector axis and the impinging point was located 30 mm away from the nozzle tip. Three injection pressures of 100, 150, and 200 MPa and a single hole diesel injector (hole diameter: 0.133mm) were selected. The flame structure and combustion process were examined by using the color luminosity images. Two-color pyrometry was used to measure the line-of sight soot temperature and concentration by using the R and B channels of the color images. The soot mass generated by impinging spray flame is higher than that of the free spray flame.
Journal Article

Effect of Injection Pressure on Ignition, Flame Development and Soot Formation Processes of Biodiesel Fuel Spray

2010-09-28
2010-32-0053
The effect of injection pressure ranging from 100 to 300MPa on the ignition, flame development and soot formation characteristics of biodiesel fuel spray using a common rail injection system for direct injection (D.I.) diesel engine was investigated. Experiments were carried out in a constant volume vessel under conditions similar to the real engine condition using a single hole nozzle. Biodiesel fuels from two sources namely; palm oil (BDFp) and cooked oil (BDFc) with the commercial JIS#2diesel fuel were utilized in this research. The OH chemiluminescence technique was used to determine the ignition and the lift-off length of the combusting flame. The natural luminosity technique was applied to study the flame development and the two color pyrometry was applied for the soot formation processes. Ignition delay decreased as the injection pressure progressed from 100 to 300MPa. This was as a result of the enhanced mixing achieved at higher injection pressures.
Technical Paper

Characteristics of Diesel Spray Flame under Flat Wall Impinging Condition --LAS, OH* Chemiluminescence and Two Color Pyrometry Results

2014-10-13
2014-01-2636
The effect of spray/wall interaction on diesel spray flame characteristics was investigated by applying LAS (Laser Absorption-Scattering) technique, OH* chemiluminescence and two color pyrometry in a constant volume vessel. To insure the precision of this investigation, following necessary verification experiments were carried out: (1) OH* chemiluminescence and two color pyrometry were synchronously employed to analyze the influence of soot incandescence on OH* chemiluminescence signal intensity; and (2) frontal view and side view OH* images of a linearly arranged three holes injector were concentrated on to investigate the effect of soot on optical intensity attenuation under line-of-sight image recording condition. And then the effect of impinging distance (30,40,50,60 mm and free) on diesel spray and combustion behaviors were studied. The results reveal that the impinging distance plays a significant role in mixture formation.
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.
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.
Technical Paper

Effects of Micro-Hole and Ultra-High Injection Pressure on Mixture Properties of D.I. Diesel Spray

2007-07-23
2007-01-1890
Experimental study has been carried out on the effects of the micro-hole nozzle injector and ultra-high injection pressure on the mixture properties of D.I. Diesel engine. A manually operated piston screw pump, High Pressure Generator, was used to obtain ultra-high injection pressures. Three kinds of injection pressures, 100MPa, 200MPa, and 300MPa, were applied to a specially designed injector. Four kinds of nozzle hole diameters, 0.16mm, 0.14mm, 0.10mm, and 0.08mm, were adopted in this study. The laser absorption-scattering (LAS) technique was used to analyze the equivalence ratio distributions, Sauter mean diameter, spray tip penetration length, and other spray characteristics. The analyses of the experimental results show that the micro-hole nozzle and ultra-high injection pressure are effective to increase the turbulent mixing rate and to form the uniform and lean fuel-air mixture.
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

Flame Propagation Characteristics in a Heterogeneous Concentration Distribution of a Fuel-Air Mixture

1998-10-19
982563
An experimental study was conducted to investigate the flame propagation characteristics in the presence of a heterogeneous concentration distribution of a fuel-air mixture in order to provide fundamental knowledge of the effects of gaseous mixture concentration heterogeneity on the combustion process. Different propane-air mixture distributions were produced by the reciprocating movements of a pair of perforated plates in a constant volume combustion chamber. The mean equivalence ratio of the fuel-air mixture was varied from 0.7 on the lean side to 1.6 on the rich side, the turbulence intensity in the combustion chamber was also varied at levels of 0.185 m/s, 0.130 m/s, 0.100 m/s, and 0.0 m/s. By an independent control of the mixture distribution and the turbulence intensity in the combustion chamber, the flame structure and flame propagation speed at various heterogeneous levels of the mixture distribution were investigated in detail.
Technical Paper

Characterization of Mixture Formation Processes in DI Gasoline Engine Sprays with Split Injection Strategy via Laser Absorption and Scattering (LAS) Technique

2003-10-27
2003-01-3161
In order to investigate the effect of split injections on mixture formation processes in Direct Injection (DI) gasoline engine sprays, an experimental study was conducted applying the laser absorption and scattering (LAS) technique to the sprays using double pulse injections with various dwells and mass ratios. The effects of various dwells and mass ratios between the pulsed injections on the spatial concentration distributions in the spray, the penetration of vapor and liquid phases, and the mean equivalence ratios of the vapor phase and overall spray, were clarified. It was found that the phenomenon of high concentration liquid spray piling up at the leading edge of the spray is avoided by the double injections with enough dwell or appropriate mass ratio. The maximum penetration length of the spray significantly decreases, especially for the liquid phase with high concentration.
Technical Paper

Breakup Process of an Initial Spray Injected by a D.I. Gasoline Injector-Simultaneous Measurement of Droplet Size and Velocity by Laser Sheet Image Processing and Particle Tracking Technique

2003-10-27
2003-01-3107
The breakup and atomization processes of the pre-swirl spray, which is produced before the hollow-cone spray from a high-pressure swirl-type D.I. gasoline injector, were investigated under different ambient pressure conditions. The injector has a press-fitted swirl tip, in which six tangential slots giving the injecting fuel an angular momentum are perforated at an equal space interval. A microscopic imaging technique was applied to get the spatially high-resolution LIF tomograms of the pre-swirl spray. The sprays were illuminated by an Nd:YAG laser light sheet and imaged using a high resolution CCD camera, fixed with a micro lens and coupled with an optical low-pass filter. The droplet size and the individual droplet's velocity were obtained by applying the image processing and the particle tracking techniques, respectively.
Technical Paper

An Insight Into Effect of Split Injection on Mixture Formation and Combustion of DI Gasoline Engines

2004-06-08
2004-01-1949
In the previous study of the authors, it was found that some benefits for the mixture preparation of DI gasoline engines can be offered by splitting the fuel injection, such as the phenomenon of high density liquid phase fuel piling up at the leading edge of the spray can be circumvented. In a further analysis, the vapor quantity in the “stable operating” range (equivalence ratio of vapor ϕv in a range of 0.7≤ϕv≤1.3) was significantly increased by the split injection compared to the single injection. In this work, the mechanism of the effect of the split injection on the mixture formation process was studied by combining the laser-sheet imaging, LIF-PIV and the LAS (Laser Absorption Scattering) technique. As a result, it is found that the spray-induced ambient air motion can help the formation of the more combustible mixture of the split injection whereas it played a minus role of diluting the spray by the single injection.
Technical Paper

Quantitative Measurement of Liquid and Vapor Phase Concentration Distributions in a D.I. Gasoline Spray by the Laser Absorption Scattering (LAS) Technique

2002-05-06
2002-01-1644
To get quantitative measurements of liquid and vapor phase concentration distributions in a gasoline spray, a laser-based absorption and scattering (LAS) technique was developed. The LAS technique adopts ultraviolet and visible lasers as light sources and a test fuel, which absorbs the ultraviolet light but does not absorb the visible light, instead of gasoline. The LAS principle is based on the incident light extinction in the ultraviolet band due to both vapor absorption and droplets scattering, whereas in the visible band, the incident light extinction is due only to the droplet scattering. The absorption spectra and molar absorption coefficients of the candidate test fuels including p-xylene, benzene and toluene, all of which have physical properties similar to gasoline, were investigated, and p-xylene was finally selected as a test fuel. Measurement accuracy of the LAS technique was discussed.
Technical Paper

An Analysis of Droplets and Ambient Air Interaction in a D.I. Gasoline Spray Using LIF-PIV Technique

2002-03-04
2002-01-0743
Measurements of the droplet and ambient air velocities in and around a D.I. gasoline spray were made by combining the laser induced fluorescence (LIF) and the particle image velocimetry (PIV) techniques. Before the fuel spray was injected into a constant volume vessel, rhodamine B-water solution was injected into the ambient air by a swirl-type injector for dispersing the fine fluorescent liquid particles as tracers for the ambient air motion. The fuel spray was injected into the fluorescent tracer clouds by a D.I. gasoline injector and was illuminated by an Nd:YAG laser light sheet (wave length: 532 nm). The light scattered by the droplets in the fuel spray was the same as the Nd:YAG laser wavelength, whereas the light emitted by the fluorescent tracer clouds was at a longer wavelength.
Technical Paper

Simultaneous Flow Field Measurement of D.I. Gasoline Spray and Entrained Ambient Air by LIF-PIV Technique

2003-03-03
2003-01-1115
The spray and the entrained ambient air motions produced by a swirl-type D.I. gasoline injector were simultaneously measured by combining the laser induced fluorescence (LIF) and the particle image velocimetry (PIV) techniques. For the simultaneous measurement of the spray and the ambient air velocities, the succeeding two image pairs of the fuel spray and the ambient air tracer particles were captured by using a Nd:YAG laser light sheet (wave length: 532 nm) and two high-resolution CCD cameras. The light emitted from the fluorescent tracer clouds was discriminated from the light scattered from the droplets in the fuel spray by an optical low-pass filter (>560 nm), and the Mie scattering signals from the spray particles were screened by a band-pass filter ranging from 520 to 545 nm. The spray and the tracer particle images were analyzed by the double frame cross-correlation PIV technique to obtain the droplets and ambient air velocity distributions.
Technical Paper

Vapor/Liquid Behaviors in Split-Injection D.I. Diesel Sprays in a 2-D Model Combustion Chamber

2003-05-19
2003-01-1837
Some experimental investigations have shown that the trade-off curve of NOx vs. particulate of a D.I. diesel engine with split-injection strategies can be shifted closer to the origin than those with a single-pulse injection, thus reducing both particulate and NOx emissions significantly. It is clear that the injection mass ratios and the dwell(s) between injection pulses have significant effects on the combustion and emissions formation processes in the D.I. diesel engine. However, how and why these parameters significantly affect the engine performances remains unexplained. The effects of both injection mass ratios and dwell between injections on vapor/liquid distributions in the split-injection diesel sprays impinging on a flat wall have been examined in our previous work.
Technical Paper

Insight on Early Spray Formation Process of a High-Pressure Swirl Injector for DISI Engines

2003-05-19
2003-01-1809
An early formation process of the spray, which was injected by a high-pressure swirl-type injector that is widely used in direct injection spark ignition (DISI) gasoline engines, was investigated through image analyzing techniques. The sprays were illuminated both by an Nd:YAG laser light sheet for getting the spray tomograms and by a tungsten lamp for getting the scattered back light shadow images of the sprays. The sprays were imaged by using a high-resolution CCD camera and a high-speed digital imaging system. The early development aspects of the spray were investigated in detail through the measurement of the tip penetration, cone angle and width of the early spray. At the start of injection, the liquid column emerges first, and it forms the “pre-swirl spray” without the swirl component. Following the liquid column, the liquid sheet emerges, however its radial velocity component is weak to form the complete hollow-cone spray. This spray changes into the “weak-swirl spray”.
Technical Paper

Characterization of Mixture Formation Processes in D.I. Gasoline Sprays by the Laser Absorption Scattering (LAS) Technique - Effect of Injection Conditions

2003-05-19
2003-01-1811
Mixture formation processes play a vital role on the performance of a D.I. Gasoline engine. Quantitative measurement of liquid and vapor phase concentration distribution in a D.I. gasoline spray is very important in understanding the mixture formation processes. In this paper, an unique laser absorption scattering (LAS) technique was employed to investigate the mixture formation processes of a fuel spray injected by a D.I. gasoline injector into a high pressure and temperature constant volume vessel. P-xylene, which is quite suitable for the application of the LAS technique, was selected as the test fuel. The temporal variations of the concentration distribution of both the liquid and vapor phases in the spray were quantitatively clarified. Then the effects of injection pressure and quantity on the concentration distributions of both the liquid and vapor phases in the spray were analyzed.
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