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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

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.
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

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.
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 Fumigated Fuel on the Ignition and Initial Combustion Stages in a D.I. Diesel Engine

1989-09-01
891880
Effects of fumigated fuel on the initial combustion stage of a diesel spray were studied by measuring an ignition delay period and rate of heat release, clarifying a self-ignition limit of a fumigated fuel. Combustion experiments on both fumigated diesel fuel and methanol in a direct injection diesel engine gave the following results; a rapid combustion occurs with the methanol fumigation, while, the diesel fuel fumigation slightly changes the combustion of the main spray of diesel fuel injected directly into the combustion chamber. Regarding the rate of heat release, the maximum rate in the initial combustion stage increases rapidly with an increase in methanol fumigation, while for the fumigated diesel fuel, the maximum rate changes only slightly. The ignition delay period affected by fumigated diesel fuel is shorter than that affected by methanol at the same fumigation equivalence ratio and intake temperature.
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

Effects of Mixture Heterogeneity on Flame Propagation in a Constant Volume Combustion Chamber

1997-10-01
972943
Although mixture formation is considered important in actual spark ignition engines, A full understanding of the combustion characteristics of a heterogeneous mixture has not yet been achieved. In this study, in order to clarify the effects of a heterogeneous concentration distribution of the fuel-air mixture on the flame propagation process, different degrees of heterogeneously distributed mixtures were created by the motion of a pair of perforated plates in a constant volume combustion chamber. The laser Rayleigh scattering method was applied for quantitative visualizations of these mixture distributions. To control the distribution of the mixture concentration and the turbulence intensity independently, the flow in the chamber and its turbulence intensity were also measured by a laser sheet method and the LDV technique.
Journal Article

Experimental Study on Mixture Formation and Ignition Processes of Spray Injected by Hole-Type Nozzle for DISI Engine

2011-11-08
2011-32-0523
The purpose of this study is to investigate the spray characteristics and ignition stability of gasoline sprays injected from a hole-type nozzle. Using a single-hole VCO (Valve-Covered-Orifice) nozzle, the spray characteristics were studied with LAS (Laser Absorption Scattering) technique, and then flame propagation and ignition stability were investigated inside a high temperature high pressure constant volume vessel using a high speed video camera. The spatial ignition stability of the spray at different locations was tested by adjusting the position of the electrodes. By adjusting the ignition timings, the stable ignition windows for 3 determined locations where the ignition stability was high at a fixed ignition timing were studied. The flame propagation process was examined using high speed shadowgraph method. Experimental results show that when the ignition points are located on the spray axis, the ignition probability is low.
Technical Paper

Experiments and Modeling on Spray Distributions in the Combustion Chamber of a Direct Injection Diesel Engine

1996-08-01
961820
Distributions of non-evaporating diesel sprays impinging on a simulated combustion chamber wall were observed from various directions while changing some of the experimental parameters, such as nozzle projection and top-clearance. High-speed photography was used in this study to examine the effects of these parameters on the spray distributions. Moreover, the spray distributions were predicted by using a spray model based on a multi-package model. The calculated distributions were displayed three-dimensionally using a volume rendering application developed by the authors. The predicted spray distributions were compared with the experimental results observed from various directions in order to evaluate the spray model.
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

Fuel Spray Simulation of High-Pressure Swirl-Injector for DISI Engines and Comparison with Laser Diagnostic Measurements

2003-03-03
2003-01-0007
A comprehensive model for sprays emerging from high-pressure swirl injectors in DISI engines has been developed accounting for both primary and secondary atomization. The model considers the transient behavior of the pre-spray and the steady-state behavior of the main spray. The pre-spray modeling is based on an empirical solid cone approach with varying cone angle. The main spray modeling is based on the Liquid Instability Sheet Atomization (LISA) approach, which is extended here to include the effects of swirl. Mie Scattering, LIF, PIV and Laser Droplet Size Analyzer techniques have been used to produce a set of experimental data for model validation. Both qualitative comparisons of the evolution of the spray structure, as well as quantitative comparisons of spray tip penetration and droplet sizes have been made. It is concluded that the model compares favorably with data under atmospheric conditions.
Technical Paper

Fuel Spray Trajectory and Dispersion in a D.I. Diesel Combustion Chamber

1989-02-01
890462
Experiments and modeling of the fuel spray trajectory and dispersion influenced by both a swirling gas flow and wall impingement were performed under simulated direct injection (D.I.) diesel engine conditions at a high pressure and high temperature. A spray was injected into the steady swirling gas flow and impinged on the simulated piston cavity wall in a constant-volume bomb. High-speed Schlieren photographs provided the informative data on the behavior of the spray vaporizing in such diesel-like circumstances. A simplified computational model was developed to describe the spray trajectory and the fuel vapor dispersion in the D.I. diesel combustion chamber. The model includes the effects of the breakup on the trajectory and the vaporization of the spray, and the effects of the swirling gas flow and the wall impingement on the dispersion of the fuel vapor.
Technical Paper

Ignition and Flame Propagation of Spray Compound Mixture

1993-10-01
932711
The ignition and flame propagation processes of a propane-air mixture compounded with a kerosene spray were investigated in order to allow a better understanding of the multi-phase combustion process of the spray compound mixture in a direct injection stratified charge (DISC) engine. The ignition probability and the flame propagation velocity, as functions of the overall equivalence ratio, fraction of propane in the fuel, ignition energy and the Sauter mean diameter of the spray, were measured under atmospheric conditions. The development of the flame kernel and the propagating flame were observed by a high-speed video camera combined with a schlieren system. Adding small amounts of the kerosene spray to the lean propane-air mixture improved the ignition probability. However, the ignition probability depended strongly on the Sauter mean diameter and the ignition energy. Replacing the propane with the kerosene spray in a rich propane-air mixture increased the flame propagation velocity.
Technical Paper

Influence of Mixture Stratification Patter non Combustion Characteristics in a Constant-Volume Combustion Chamber

1995-10-01
952412
A pancake-type constant-volume combustion chamber was used to investigate the combustion and NOx emission characteristics of propane-air and hydrogen-air mixtures under various charge stratification patterns, which were obtained by variations of the initial charge and injected mixture concentrations and the ignition spark timing. A planar laser-induced fluorescence from nitrogen dioxide as gas fuel tracer was applied to measure the mixture distribution in the test chamber. The second harmonic output of pulsed Nd; YAG laser was used as a light source for fluorescence excitation. The fluorescence images were corrected by a gated image-intensified CCD camera. The quantitative analysis of fuel concentration was made possible by the application of linearity between fluorescence intensity and NO2 concentration at low trace level.
Technical Paper

Injection Strategy to Enhance Mixture Formation and Combustion of Fuel Spray in Diesel Engine

2018-04-03
2018-01-0241
Increasing the injection pressure and splitting the injection stage are the major approaches for a diesel engine to facilitate the fuel-air mixture formation process, which determines the subsequent combustion and emission formation. In this study, the free spray was injected by a single-hole nozzle with a hole-diameter of 0.111 mm. The impinging spray, formed by a two-dimensional (2D) piston cavity having the same shape as a small-bore diesel engine, was also investigated. The injection process was performed by both with and without pre-injection. The main injection was carried out either as a single main injection with injection pressure of 100 MPa (Pre + S100) or a split main injection with 160 MPa defined by the mass fraction ratio of 3:1 (Pre + D160_3-1). The tracer Laser Absorption Scattering (LAS) technique was adopted to observe the spray mixture formation process. The ignition delay/location and the soot formation in the spray flame were analyzed by the two-color method.
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

Internal Fuel Flow, Near-Field and Far-Field Spray Evolution, and Mixture Formation Characteristics of Diesel Injectors - A Comparison between Multi- and Single-Hole Injectors

2019-04-02
2019-01-0273
A comparison of spray characteristics was conducted between single- and multi-hole injectors. A commercial software (AVL FIRE) was used to investigate the internal flow inside the sac volume, as well as the initial spray behavior at 1 mm downstream of the nozzle exit. Microscopic imaging was applied to observe the spray dispersion angle (spray cone angle) at the vicinity of the nozzle. Laser absorption scattering (LAS) technique was implemented for measuring the mixture concentration. Three injection quantities, namely 0.5, 2.5, and 5.0 mg/hole, were selected to observe the differences between transient and quasi-steady spray. The vapor penetration at the initial stage of the injection was greater for single-hole than that of multi-hole injector due to faster fuel pressure build-up process inside the sac volume.
Technical Paper

Measurement of Turbulent Flow in the Combustion Chamber of a D.I. Diesel Engine

1990-02-01
900061
This paper presents the experimental analysis for the turbulence in the combustion chamber of a direct injection (D.I.) diesel engine. A dual beam mode, forward-scattering laser doppler velocimeter was applied to the flow measurement in a four-stroke, single-cylinder direct injection diesel engine of 110 mm bore and 125 mm stroke. The turbulence component was separated from instantaneous velocity using a high-pass filter. As a result, the difference in turbulent intensity between the intake and compression processes was discussed. Also, the effect of intake port and piston cavity shapes, the compression ratio and the engine speed on the turbulent intensity were clarified. In addition, the empirical equation for the decay of turbulent intensity in the compression process was expressed by a function of the Reynolds number based on the mean swirling flow.
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.
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