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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.

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.

Fuel spray impingement on the combustion chamber wall cannot be avoid in direct injection gasoline engines, resulting in insufficient combustion and unburned hydrocarbon/soot emissions from the engines. And the microscopic characteristics of the impinging spray have a close relation with the fuel film formation, which has a direct effect on the engine performance and emissions. Therefore, figuring out the droplet behaviors of the impinging spray is significantly important for improving the engine performance and reducing emissions. However, the microscopic characteristics of the impinging spray have not been deeply understood and the differences between the impinging and free spray are seldom mentioned in previous study. Therefore, particle image analysis (PIA) technique was applied to detect the microscopic characteristics at the capture location in order to track the droplet behaviors of the spray tip during the propagation process.

Owing to the small size of engines and high injection pressures, 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. As a result, the droplets size and distribution are significantly important to evaluate the atomization and predict the impingement behaviors, such as stick, spread or splash. However, the microscopic behaviors of droplets are seldom reported due to the high density of small droplets, especially under high pressure conditions. In order to solve this problem, a “spray slicer” was designed to cut the spray before impingement as a sheet one to observe the droplets clearly. The experiment was performed in a constant volume chamber under non-evaporation condition, and a mini-sac injector with single hole was used.

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.

The effects of combining premixed, low temperature combustion (LTC) with biodiesel are relatively unknown to this point. This mode allows simultaneously low soot and NOx emissions by using high rates of EGR and increasing ignition delay. This paper compares engine performance and emissions of neat, soy-based methyl ester biodiesel (B100), B20, B50, pure ultra low sulfur diesel (ULSD) and a Swedish, low aromatic diesel in a multi-cylinder diesel engine operating in a late-injection premixed LTC mode. Using heat release analysis, the progression of LTC combustion was explored by comparing fuel mass fraction burned. B100 had a comparatively long ignition delay compared with Swedish diesel when measured by start of ignition (SOI) to 10% fuel mass fraction burned (CA10). Differences were not as apparent when measured by SOI to start of combustion (SOC) even though their cetane numbers are comparable.

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.

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.

Premixed low temperature combustion (LTC) in diesel engines simultaneously reduces soot and NOx at the expense of increased hydrocarbon (HC) and CO emissions. The use of biodiesel in the LTC regime has been shown to produce lower HC emissions than petroleum diesel; however, unburned methyl esters from biodiesel are more susceptible to particulate matter (PM) formation following atmospheric dilution due to their low volatility. In this study, the efficacy of a production-type diesel oxidation catalyst (DOC) for the conversion of light hydrocarbons species and heavier, semi-volatile species like those in unburned fuel is examined. Experimental data were taken from a high speed direct-injection diesel engine operating in a mid-load, late injection partially premixed LTC mode on ultra-low sulfur diesel (ULSD) and neat soy-based biodiesel (B100). Gaseous emissions were recorded using a conventional suite of analyzers and individual light HCs were measured using an FT-IR analyzer.

Ethanol is regarded as the promising alternative fuel for gasoline to meet the strict low emission standard for spark ignition engines. In this study, the spray mixture formation process for different ethanol blended fuels, including E0 (gasoline), E85 (85% volume of ethanol and 15% volume of gasoline) and E100 (ethanol), has been evaluated using hole-type nozzle by the measurement of Laser Absorption Scattering (LAS) technique in a constant volume vessel. Based on the principle of LAS, the quantitative vapor and liquid phase distribution from different ethanol blended fuel can be obtained by the light extinction regime. Aiming to analyze the effect of mixture formation and evaporation for different components of blended fuel or pure gasoline and ethanol, the vapor distribution of gasoline was determined by using p-xylene, which had similar physical properties to gasoline, especially higher boiling temperature components, and higher absorption for ultraviolet.

A quasi-dimensional computer simulation of the turbocharged spark-ignition engine has been developed in order to study system performance as various design parameters and operating conditions are varied. The simulation is of the “filling and emptying” type. Quasi-steady flow models of the compressor, intercooler, manifolds, turbine, wastegate, and ducting are coupled with a multi-cylinder engine model where each cylinder undergoes the same thermodynamic cycle. A turbulent entrainment model of the combustion process is used, thus allowing for studies of the effects of various combustion chamber shapes and turbulence parameters on cylinder pressure, temperature, NOx emissions and overall engine performance. Valve open areas are determined either based on user supplied valve lift data or using polydyne-generated cam profiles which allow for variable valve timing studies.

The combustion process in a diesel engine was simulated using KIVA-II, a multi-dimensional computer code. The original combustion model in KIVA-II is based on chemical kinetics, and thus fails to capture the effects of turbulence on combustion. A mixing-controlled, eddy break-up combustion model was implemented into the code. Realistic diesel fuel data were also compiled. Subsequently, the sensitivity of the code to a number of parameters related to fuel injection, mixing, and combustion was studied. Spray injection parameters were found to have a strong influence on the model's predictions. Higher injection velocity and shorter injection duration result in a higher combustion rate and peak pressure and temperature. The droplet size specified at injection significantly affects the rate of spray penetration and evaporation, and thus the combustion rate. Contrary to expectation, the level of turbulence at the beginning of the calculation did not affect fuel burning rate.

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.

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.

Three-Dimensional visualization technique based on volume rendering method has been developed in order to translate a calculated result of diesel combustion simulation into an realistically spray and flame image. This paper presents an overview of diesel combustion model which has been developed at Hiroshima University, a description of the three-dimensional visualization technique, and some examples of spray and flame image generated by this visualization technique.

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.

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.

Direct injection of natural gas under high pressure conditions has emerged as a promising option for improving engine fuel economy and emissions. However, since the gaseous injection technology is new, limited experience exists as to the optimum configuration of the injection system and associated combustion chamber design. The present study uses KIVA-3 based, multidimensional modeling to improve the understanding and assist the optimization of the gaseous injection process. Compared to standard k-ε models, a Renormalization Group Theory (RNG) based k-ε model [1] has been found to be in better agreement with experiments in predicting gaseous penetration histories for both free and confined jet configurations. Hence, this validated RNG model is adopted here to perform computations in realistic engine geometries.

A detailed chemical kinetic mechanism, consisting of 22 species and 104 elementary reactions, has been used in conjunction with the multi-dimensional reactive flow code KIVA-3 to study autoignition of natural gas injected under compression ignition conditions. Calculations for three different blends of natural gas are performed on a three-dimensional computational grid by modeling both the injection and ignition processes. Ignition delay predictions at pressures and temperatures typical of top-dead-center conditions in compression ignition engines compare well with the measurements of Naber et al. [1] in a combustion bomb. Two different criteria, based on pressure rise and mass of fuel burned, are used to detect the onset of ignition. Parametric studies are conducted to show the effect of additives like ethane and hydrogen peroxide in increasing the fuel consumption rate.

An experimental and numerical study was conducted on the spray and mixture properties of a hole-type injector for direct injection (D. I.) gasoline engines. The Laser Absorption Scattering (LAS) technique was adopted to simultaneously measure the spatial concentration distributions and the mass of the liquid and vapor phases in the fuel spray injected into a high-pressure and high-temperature constant volume vessel. The experimental results were compared to the numerical calculation results using three-dimensional CFD and the multi-objective optimization. In the numerical simulation, the design variable of the spray model was optimized by choosing spray tip penetration, and mass of liquid and vapor phases as objective functions.