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Technical Paper

A Practical Calculation Method for Injection Pressure and Spray Penetration in Diesel Engines

1992-02-01
920624
Spray penetration for Diesel injectors, where injection pressure varies with time during the injection period, was calculated. In order to carry out this calculation, the discharge coefficients of the needle-seat opening passage and discharge hole in orifice-type Diesel nozzles were investigated separately. Simple empirical correlations were obtained between these coefficients and needle lift. Then, by introducing these correlations, the injection pressure, which is defined as the pressure in the sac chamber just upstream of the discharge hole, was either derived from measured fuel supply line pressure, or predicted by means of an injection system simulation. Finally, based on the transient injection pressure, spray tip penetration was calculated by taking the overall line which covers the trajectories of all fuel elements ejected during the injection period.
Technical Paper

A Visual Study of D.I. Diesel Combustion from the Under and Lateral Sides of an Engine

1986-09-01
861182
A high-speed photographic study is presented illustrating the influence of engine variables such as an introduced air swirl, the number of nozzle holes and the piston cavity diameter, on the combustion process in a small direct-injection (D.I.) diesel engine. The engine was modified for optical access from the under and lateral sides of the combustion chamber. This modification enabled a three-dimensional analysis of the flame motion in the engine. The swirling velocity of a flame in a combustion chamber was highest in the piston cavity, and outside the piston cavity it became lower at the piston top and at the cylinder head in that order. The swirl ratio of the flame inside the cavity radius attenuated gradually with piston descent and approached the swirl ratio outside the cavity radius, which remained approximately constant during the expansion stroke. Engine performance was improved by retarding the attenuation of the swirl motion inside the cavity radius.
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

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

Approach to Low NOx and Smoke Emission Engines by Using Phenomenological Simulation

1993-03-01
930612
A phenomenological spray-combustion model of a D.I. Diesel engine was applied to study the engine parameters with potential for reducing NOx and smoke emissions. The spray-combustion model, first developed at the University of Hiroshima in 1976, has been sophisticated by incorporating new knowledge of diesel combustion. The model was verified using data from an experimental, single cylinder, D.I. diesel engine with a bore of 135mm and a stroke of 130mm. After the verification process, calculations were made under a wide range of the engine parameters, such as intake air temperature, intake air pressure, intake swirl ratio, nozzle hole diameter, injection pressure, air entrainment rate into the spray, and injection rate profile. These calculations estimated the effects of the engine parameters on NOx, smoke and specific fuel consumption. As a result of the calculations, an approach for the low NOx and smoke emission engine was found.
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.
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.
Technical Paper

Characteristics of Flat-Wall Impinging Spray Flame and Its Heat Transfer under Small Diesel Engine-Like Condition

2017-11-05
2017-32-0032
Heat loss is more critical for the thermal efficiency improvement in small size diesel engines than large-size diesel engines. More than half of total heat energy in the internal-combustion engine is lost by cooling through the cylinder walls to the atmosphere and the exhaust gas. Therefore, the new combustion concept is needed to reduce losses in the cylinder wall. In a Direct Injection (DI) diesel engine, the spray behavior, including spray-wall impingement has an important role in the combustion development to reduce heat loss. The aim of this study is to understand the mechanism of the heat transfer from the spray and flame to the impinging wall. Experiments were performed in a constant volume vessel (CVV) at high pressures and high temperatures. Fuel was injected using a single-hole injector with a 0.133 mm diameter nozzle. Under these conditions, spray evaporates, then burns near the wall. Spray/flame behavior was investigated with a high-speed video camera.
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.
Technical Paper

Characterization of Combustion Processes in the Prechamber and Main Chamber of an Indirect Injection Diesel Engine by High-Speed Photography

1986-09-01
861181
The combustion processes in the prechamber and the main chamber of a small indirect injection (I.D.I.) diesel engine were observed simultaneously by high-speed photography. These observations made it possible to characterize the behavior of flames in both chambers, that is, ignition of fuel, developing and rotating flames in the prechamber, and a flame jet spouting into the main chamber. The effect of engine variables, such as fuel injection timing, cross-sectional area of a throat, fuel injector location, and a recess in a piston top, on the combustion process as well as the engine performance were considered. A flame jet spouting into the main chamber separated into two directions and induced two vortexes. Brown sooty flames appeared along the prechamber wall and inside the flame jet which struck on the piston top. The higher-velocity flame jet and the two Intense vortexes induced by the flame jet realized superior fuel consumption and lower smoke emission.
Technical Paper

Characterization of Flows in the Sac Chamber and the Discharge Hole of a D.I. Diesel Injection Nozzle by Using a Transparent Model Nozzle

1997-10-01
972942
The internal flow of a diesel injection nozzle was studied by using transparent model nozzles to clarify the effects of the flows in the sac chamber and the discharge hole on the spray behaviors. The geometry of the model nozzle was scaled up 10 times the actual nozzle and the injection pressure for the model nozzle was adjusted so as to achieve a Reynolds number at the discharge hole which was the same as an actual nozzle. Aluminium oxide (Al2O3) tracers were used to visualize the flow patterns in the sac chamber. Sequential photographs of the internal flow and the issuing spray plume during the opening process of the needle valve were taken by a high-speed video camera. By locating the discharge hole on the upper side of the sac chamber, the turbulence intensity in the sac chamber increases and the spread angle of the spray plume becomes large.
Journal Article

Characterization of Internal Flow and Spray Behaviors of Hole-Type Nozzle under Tiny and Normal Injection Quantity Conditions for Diesel Engine

2016-04-05
2016-01-0862
The tiny and normal injection quantity instances usually happen under the multi-injection strategy condition to restrain the uncontrollability of the ignition timing of the homogeneous charge compression ignition (HCCI) combustion concept. Meanwhile, instead of the traditional and fundamental single-hole diesel injector, the axisymmetric multi-hole injectors are usually applied to couple with the combustion chamber under most practical operating conditions. In the current paper, the internal flow and spray characteristics generated by single-hole and multi-hole (10 holes) nozzles under normal (2 mm3/hole) and tiny (0.3 mm3/hole) injection quantity conditions were investigated in conjunction with a series of experimental and computational methods. High-speed video observation was conducted at 10000 and 100000 fps under the condition of 120 MPa rail pressure, 1.5 MPa ambient pressure, room temperature, and nitrogen environment to visualize different spray properties.
Technical Paper

Characterization of Mixture Formation in Split-Injection Diesel Sprays via Laser Absorption-Scattering (LAS) Technique

2001-09-24
2001-01-3498
Experimental results of a diesel engine have shown that using split-injection can reduce the NOx and particulate emissions. For understanding the mechanism of emissions reduction, mixture formation in split-injection diesel sprays was characterized in the present paper. A dual-wavelength laser absorption-scattering (LAS) technique was developed by use of the second harmonic (532nm) and the fourth harmonic (266nm) of a pulsed Nd:YAG laser as the incident light and dimethylnaphthalene (DMN) as the test fuel. By applying this technique, imaging was made of DMN sprays injected into a high-temperature and high-pressure constant volume vessel by a single-hole nozzle incorporated in a common rail injection system for D.I. diesel engine. The line-of-sight optical thickness of both fuel vapor and droplets in the sprays was yielded from the sprays images.
Technical Paper

Combustion Characteristics of Diesel Spray with Temporally-Splitting High-Pressure Injection

2015-11-17
2015-32-0825
The effect of temporally-splitting high pressure injection on Diesel spray combustion and soot formation processes was studied by using the high-speed video camera. The spray was injected by the single-hole nozzle with a hole diameter of 0.11mm into the high-pressure and high-temperature constant volume vessel. The free spray and the spray impingement on the two dimensional (2D) piston cavity wall were examined. Injection pressures of 100 and 160 MPa for the single injection and 160 MPa for the split injection were selected. The flame structure and soot formation process were examined by using the two-color pyrometry. The soot generated in the flame under the split injection under 160 MPa becomes higher than that of the single injection under 160 MPa.
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.
Journal Article

Effect of Ethanol Ratio on Ignition and Combustion of Ethanol-Gasoline Blend Spray in DISI Engine-Like Condition

2015-04-14
2015-01-0774
To reduce carbon dioxide emission and to relieve the demand of fossil fuels, ethanol is regarded as one of the most promising alternative fuels for gasoline. Recently, using ethanol in the state-of-the-art gasoline engine, direct-injection spark-ignition (DISI) engine, has become more attention by researchers due to less knowledge of the ignition and combustion processes in that engine. In this study, different ethanol-gasoline blended fuels, E0 (100% gasoline), E85 (85% ethanol and 15% gasoline mixed in volume basis) and E100 (100% ethanol) were injected by a valve-covered-orifice (VCO) hole-type nozzle. The experimental environment was set to the condition similar with the near top dead center (TDC) in DISI engine. The high-speed imaging of shadowgraph, OH* chemiluminescence and flame natural luminosity were used to clarify the characteristics of the ignition process, flame development and propagation.
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.
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.
Technical Paper

Effects of Droplet Behaviors on Fuel Adhesion of Flat Wall Impinging Spray Injected by a DISI Injector

2019-09-09
2019-24-0034
Owing to the short impingement distance and high injection pressure, it is difficult to avoid the fuel spray impingement on the combustion cylinder wall and piston head in Direct Injection Spark Ignition (DISI) engine, which is a possible source of hydrocarbons and soot emission. For better understanding of the mechanisms behind the spray-wall impingement, the fuel spray and adhesion on a flat wall using a mini-sac injector with a single-hole was examined. The microscopic characteristics of impinging spray were investigated through Particle Image Analysis (PIA). The droplet size and velocity were compared before impingement. The adhered fuel on the wall was measured by Refractive Index Matching (RIM). The fuel adhesion mass and area were discussed. Moreover, the relationships between droplets behaviors and fuel adhesion on the wall were discussed.
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.
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