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Technical Paper

Effect of Initial Fuel Temperature on Spray Characteristics of Multicomponent Fuel

Fuel design concept has been proposed for low emission and combustion control in engine systems. In this concept, the multicomponent fuels, which are mixed with a high volatility fuel (gasoline or gaseous fuel components) and a low volatility fuel (gas oil or fuel oil components), are used for artificial control of fuel properties. In addition, these multicomponent fuels can easily lead to flash boiling which promote atomization and vaporization in the spray process. In order to understand atomization and vaporization process of multicomponent fuels in detail, the model for flash boiling spray of multicomponent fuel have been constructed and implemented into KIVA3V rel.2. This model considers the detailed physical properties and evaporation process of multicomponent fuel and the bubble nucleation, growth and disruption in a nozzle orifice and injected fuel droplets.
Technical Paper

Effects of Spray Internal EGR Using CO2 Gas Dissolved Fuel on Combustion Characteristics and Emissions in Diesel Engine

We have proposed the application of Exhaust Gas Recirculation (EGR) gas dissolved fuel which might improve spray atomization through effervescent atomization instead of high injection pressure. Since EGR gas is included in the spray of EGR gas dissolved fuel, it directly contributes to combustion, and the further reduction of NOx emissions is expected rather than the conventional external EGR. In our research, since highly contained in the exhaust gas and highly soluble in the fuel, CO2 was selected as the dissolved gas to simulate EGR gas dissolved. In this paper, the purpose is to evaluate the influence of the application of CO2 gas dissolved fuel on the combustion characteristics and emission characteristics inside the single cylinder, direct injection diesel engine. As a result, by use of the fuel, smoke was reduced by about 50 to 70%, but NOx reduction does not have enough effect.
Technical Paper

The Experimental Investigation of the Performance and Emissions Characteristics of Direct Injection Diesel Engine by Bio-Hydro Fined Diesel Oil and Diesel Oil in Different EGR

Bio-hydro fined diesel (BHD) oil is known as a second generation oil made from bio hydro finning process. Biodiesel in the first generation is made from transesterification process and it has several disadvantages such as high density and increased the viscosity that can cause operational problems because can make some deposits in the engine. To overcome this, the second generation process of biodiesel has been modified from the first generation oil. BHD is made from the waste cooking oil by using the hydro finning process without the trans-esterification process. The results of BHD oil has nearly the same with diesel oil. BHD oil has low viscosity and high oxidation stability. Therefore, BHD oil can be used in the diesel engine without making any modifications in the engine. In this study, the comparison of performance and emissions characteristics from BHD oil, waste cooking oil, and diesel oil are investigated.
Technical Paper

Study for Higher Efficiency and Lower Emissions in Turbo Charged Small Gas Engine Using Low Caloric Biomass Model Gas

In recent years, depletion of energy resources and increasing CO2 emission have been concerned. As this solution, the use of biofuels from garbage is focused. In this research, higher efficiency and lower emissions in the gas engine for power generation using biomass gas are aimed. However, the biomass gas is low caloric value and the output is low and the combustion is unstable. Therefore, a turbocharged spark ignition gas engine is used as the test institution. As a result, it is found that combustion stability and high efficiency of biomass gas can be realized.
Technical Paper

Improvement of Combustion Characteristics and Emissions by Applying CO2 Gas Dissolved Fuel in Diesel Engine

We have proposed the application of EGR gas dissolved fuel which might improve spray atomization through effervescent atomization instead of high injection pressure. In this paper, the purpose is to evaluate the influence of the application of CO2 gas dissolved fuel on the combustion characteristics and emissions inside the single cylinder, direct injection diesel engine. As a result, by use of the fuel, smoke was reduced by about 50 to 70%. The amount of NOx was reduced at IMEP=0.3 MPa, but it was increased at IMEP=0.9 MPa.
Technical Paper

Study on Multicomponent Fuel Spray with High Injection Pressure

In previous study, the model for flash-boiling spray of multicomponent fuel was constructed and was implemented into KIVA code. This model considered the detailed physical properties and evaporation process of multicomponent fuel and the bubble nucleation, growth and disruption in a nozzle orifice and injected fuel droplets. These numerical results using this model were compared with experimental data which were obtained in the previous study using a constant volume vessel. The spray characteristics from numerical simulation qualitatively showed good agreement with the experimental results. Especially, it was confirmed from both the numerical and experimental data that flash-boiling effectively accelerated the atomization and vaporization of fuel droplets. However, in this previous study, injection pressure was very low (up to 15 MPa), and the spray characteristics of high pressure injection could not be analyzed.
Technical Paper

A Study on Higher Thermal Efficiency and Lower Cooling Loss in Diesel Engine

The purpose of this study is to achieve thermal efficiency improvement and cooling loss reduction of a diesel engine with a combustion concept of earlier evaporation, higher entrainment, and compact spray flame. In order to realize this concept, the paper focused on two-component fuel (nC5H12/nC10H22) with high evaporation. In this paper, the effects of two-component fuel on thermal efficiency and exhaust characteristics are examined by using single cylinder diesel engine. In addition, spray characteristics are revealed in an optically accessible chamber and combustion characteristics are revealed by using RCEM.
Technical Paper

Improvement of Spray and Combustion Process by Applying CO2 Gas Dissolved Fuel

The CO2 gas dissolved fuel for the diesel combustion is effective to reduce the NOx emissions to achieve the internal EGR (Exhaust Gas Recirculation) effect by fuel. This method has supplied EGR gas to the fuel side instead of supply EGR gas to the intake gas side. The fuel has followed specific characteristics for the diesel combustion. When the fuel is injected into the chamber in low pressure, this CO2 gas is separated from the fuel spray. The distribution characteristics of the spray are improved and the improvement of the thermal efficiency by reduction heat loss in the combustion chamber wall, and reduce soot emissions by the lean combustion is expected. Furthermore, this CO2 gas decreases the flame temperature. Further, it is anticipated to reduce NOx emissions by the spray internal EGR effect.
Technical Paper

Reduction of Reaction Mechanism for n-Tridecane Based on Knowledge of Detailed Reaction Paths

n-Tridecane is a low boiling point component of gas oil, and has been used as a single-component fuel for diesel spray and combustion experiments. However, no reduced chemical kinetic mechanisms for n-tridecane have been presented for three-dimensional modeling. A detailed mechanism developed by KUCRS (Knowledge-basing Utilities for Complex Reaction Systems), contains 1493 chemical species and 3641 reactions. Reaction paths during ignition process for n-tridecane in air computed using the detailed mechanism, were analyzed with the equivalence ratio of 0.75 and the initial temperatures of 650 K, 850 K, and 1100 K, which are located in the cool-flame dominant, negative-temperature coefficient, and blue-flame dominant regions, respectively.
Technical Paper

Artificial Control of Diesel Spray and Flame Feature by using Dual-component Fuel

Fuel design approach has been proposed as the control technique of spray and combustion processes in diesel engine to improve thermal efficiency and reduce exhaust emissions. In order to kwow if this approach is capable of controlling spray flame structure and interaction between the flame and a combustion chamber wall, the present study investigated ignition and flame characteristics of dual-component fuels, while varying mixing fraction, fuel temperature and ambient conditions. Those characteristics were evaluated through chemiluminescence photography and luminous flame photography. OH radical images and visible luminous flame images were analyzed to reveal flame shape aspect ratio and its fractal dimension.
Journal Article

Simultaneous Reduction of Pressure Rise Rate and Emissions in a Compression Ignition Engine by Use of Dual-Component Fuel Spray

Ignition, combustion and emissions characteristics of dual-component fuel spray were examined for ranges of injection timing and intake-air oxygen concentration. Fuels used were binary mixtures of gasoline-like component i-octane (cetane number 12, boiling point 372 K) and diesel fuel-like component n-tridecane (cetane number 88, boiling point 510 K). Mass fraction of i-octane was also changed as the experimental variable. The experimental study was carried out in a single cylinder compression ignition engine equipped with a common-rail injection system and an exhaust gas recirculation system. The results demonstrated that the increase of the i-octane mass fraction with optimizations of injection timing and intake oxygen concentration reduced pressure rise rate and soot and NOx emissions without deterioration of indicated thermal efficiency.
Technical Paper

BSFC Improvement and NOx Reduction by Sequential Turbo System in a Heavy Duty Diesel Engine

Reduction of exhaust emissions and BSFC has been studied using a high boost, a wide range and high-rate EGR in a Super Clean Diesel, six-cylinder heavy duty engine. In the previous single-turbocharging system, the turbocharger was selected to yield maximum torque and power. The selected turbocharger was designed for high boosting, with maximum pressure of about twice that of the current one, using a titanium compressor. However, an important issue arose in this system: avoidance of high boosting at low engine speed. A sequential and series turbo system was proposed to improve the torque at low engine speeds. This turbo system has two turbochargers of different sizes with variable geometry turbines. At low engine speed, the small turbocharger performs most of the work. At medium engine speed, the small turbocharger and large turbocharger mainly work in series.
Journal Article

Modeling of Auto-Ignition and Combustion Processes for Dual-Component Fuel Spray

Auto-ignition and combustion processes of dual-component fuel spray were numerically studied. A source code of SUPERTRAPP (developed by NIST), which is capable of predicting thermodynamic and transportation properties of pure fluids and fluid mixtures containing up to 20 components, was incorporated into KIVA3V to provide physical fuel properties and vapor-liquid equilibrium calculations. Low temperature oxidation reaction, which is of importance in ignition process of hydrocarbon fuels, as well as negative temperature coefficient behavior was taken into account using the multistep kinetics ignition prediction based on Shell model, while a global single-step mechanism was employed to account for high temperature oxidation reaction. Computational results with the present multi-component fuel model were validated by comparing with experimental data of spray combustion obtained in a constant volume vessel.
Technical Paper

Effects of Mixedness and Ignition Timings on PCCI Combustion with a Dual Fuel Operation

A dual fuel operation with different reactivity fuels has the possibility of optimizing performance and emissions in premixed charge compression ignition engines by controlling the spatial concentration and distribution of both fuels. In the present study, n-heptane and i-octane were independently injected through two different injectors. In-cylinder pressure analysis and emissions measurement were performed in a compression ignition engine. Injection timings, fuel quantity ratio between the injections were changed for the two cases, in which one fuel was injected using a port fuel injection system while the other was directly injected into the cylinder, in order to drastically vary mixture distributions and ignition timings. In addition, an optical diagnostic was performed in a rapid compression and expansion machine to develop an understanding of the ignition processes of the two mixtures.
Technical Paper

Effect of Fuel Properties of Biodiesel on Its Combustion and Emission Characteristics

The use of biofuel is essential for the reduction of greenhouse gas emission. This paper highlights the use of biodiesel as a means of reducing greenhouse gas emission from the diesel engine of heavy-duty vehicles. Biodiesel is fatty acid methyl ester (FAME) obtained through ester exchange reaction by adding methanol to oil, such as rapeseed oil, soybean oil, palm oil, etc. The CO₂ emission from combustion of biodiesel is defined to be equivalent to the CO₂ volume absorbed by its raw materials or plants in their course of growth. On the other hand, however, biodiesel is known to increase the NOx emission when compared with operating with conventional diesel fuel, then suppressing this increase is regarded as a critical issue. This study is intended to identify the fuel properties of biodiesel free from increase in the NOx emission.
Technical Paper

Development of High Pressure H2 Gas Injectors, Capable of Injection at Large Injection Rate and High Response Using a Common-rail Type Actuating System for a 4-cylinder, 4.7-liter Total Displacement, Spark Ignition Hydrogen Engine

Key requirements of engines for vehicles are large output power and high efficiency, low emission as well as small size and light weight. Hydrogen combustion engines with direct injection have the characteristics to meet these factors. Tokyo City University, former Musashi Institute of Technology, has studied hydrogen fueled engines with direct injection since 1971. The key technology in the development of hydrogen fueled engines is the hydrogen injector for direct injection with the features such as high injection rate, high response and no hydrogen gas leakage from the needle valve of the hydrogen injector. A common-rail type system to actuate the needle valves of the high pressure hydrogen injectors was intentionally applied to fulfill good performances such as large injection rate, high response and no hydrogen gas leakage.
Technical Paper

Effective BSFC and NOx Reduction on Super Clean Diesel of Heavy Duty Diesel Engine by High Boosting and High EGR Rate

Reduction of exhaust emissions and BSFC was studied for high pressure, wide range, and high EGR rates in a Super-clean Diesel six-cylinder heavy duty engine. The GVW 25-ton vehicle has 10.52 L engine displacement, with maximum power of 300 kW and maximum torque of 1842 Nm. The engine is equipped with high-pressure fuel injection of a 200 MPa level common-rail system. A variable geometry turbocharger (VGT) was newly designed. The maximum pressure ratio of the compressor is about twice that of the previous design: 2.5. Additionally, wide range and a high EGR rate are achieved by high pressure-loop EGR (HP-EGR) and low pressure-loop EGR (LP-EGR) with described VGT and high-pressure fuel injection. The HP-EGR can reduce NOx concentrations in the exhaust pipe, but the high EGR rate worsens smoke. The HP-EGR system layout has an important shortcoming: it has great differences of the intake EGR gas amount into each cylinder, worsens smoke.
Technical Paper

Exhaust Emission Characteristics of Commercial Vehicles Fuelled with Biodiesel

The application of biodiesel as an alternative fuel for petroleum diesel fuel is very effective for the reduction of CO₂ emission, because biodiesel is produced from renewable biomass resources. In Japan, neat biodiesel derived from waste cooking oil has often been applied to commercial vehicles. However, it is possible that the difference of fuel properties between conventional diesel fuel and biodiesel causes the problems on exhaust emission characteristics of diesel engine. Therefore, it is necessary to clarify the effect of biodiesel fuelling on exhaust emissions from commercial vehicles. Light-duty garbage trucks and heavy-duty diesel buses which were actually fueled with biodiesel in Kyoto, Japan, were used for test vehicles in this study. The exhaust emissions from these vehicles during JE05 mode tests were compared between biodiesel derived from waste cooking oil and conventional diesel fuel.
Technical Paper

Effective Usage of LNT in High Boosted and High EGR Rate of Heavy Duty Diesel Engine

Lean NOx trap (LNT) and Urea-SCR system are effective aftertreatment systems as NOx reduction device in diesel engines. On the other hand, DPF has already been developed as PM reduction device and it has been used in various vehicles. LNT can absorb and reduce NOx emission in wide range exhaust temperatures, from 150°C to 400°C, and the size of LNT component can be compact in comparison with Urea-SCR system because LNT uses the diesel fuel as a reducing agent and it is needless to install the reducing agent tank in the vehicle. In this study, authors have shown that the NOx conversion rate of LNT is high in the case of extremely low NOx concentration from the engine. Also, the effects of LNT and DPF were examined using the Super Clean Diesel (SCD) Engine, which has low NOx level before aftertreatment and has been finished as Japanese national project.
Technical Paper

Reduction of NOx and PM for a Heavy Duty Diesel Using 50% EGR Rate in Single Cylinder Engine

For reducing NOx emissions, EGR is effective, but an excessive EGR rate causes the deterioration of smoke emission. Here, we have defined the EGR rate before the smoke emission deterioration while the EGR rate is increasing as the limiting EGR rate. In this study, the high rate of EGR is demonstrated to reduce BSNOx. The adapted methods are a high fuel injection pressure such as 200 MPa, a high boost pressure as 451.3 kPa at 2 MPa BMEP, and the air intake port that maintains a high air flow rate so as to achieve low exhaust emissions. Furthermore, for withstanding 2 MPa BMEP of engine load and high boosting, a ductile cast iron (FCD) piston was used. As the final effect, the installations of the new air intake port increased the limiting EGR rate by 5%, and fuel injection pressure of 200 MPa raised the limiting EGR rate by an additional 5%. By the demonstration of increasing boost pressure to 450 kPa from 400 kPa, the limiting EGR rate was achieved to 50%.