Search Results

To control the auto ignition in end-gas region and to achieve higher thermal efficiency in a natural gas dual fuel engine operated under PREMIER combustion mode where the end-gas auto ignition occurs without knocking-like oscillation, the EGR (exhaust gas recirculation) and supercharging were applied. The EGR rate and the intake air pressure as well as the pilot injection timing of diesel fuel were varied, and the profiles of the in-cylinder pressure, the exhaust emissions and the heat balance were examined at the indicated mean effective pressure around 680 kPa. The experimental results showed that higher thermal efficiency can be achieved with the combination of the PREMIER combustion and the EGR rate of 30% due to the improvements in the combustion efficiency and the degree of constant volume heat release while reducing the cooling loss.

The authors have reported significant smoke reduction in twin shaped semi-premixed diesel combustion with a newly designed combustion chamber to distribute the first and the second sprays into upper and lower layers. However, the first stage premixed combustion tends to advance far from the TDC, resulting in lowering of thermal efficiencies. In this report, improvement of thermal efficiency by optimizing the combustion phase with lower ignitability fuels was identified with the divided combustion chamber. The experiment was conducted with four fuels with different cetane numbers. The first stage premixed combustion can be retarded to the optimum phase with the fuel with cetane number 38, establishing high efficiencies.

Spark knock suppression with hydrogen addition was investigated at two engine speeds (2000 rpm and 4800 rpm). The experimental results showed that the spark knock is strongly suppressed with increasing hydrogen fraction at 2000 rpm while the effect is much smaller at 4800 rpm. To explain these results, chemical kinetic analyses with a two-zone combustion model were performed. The calculated results showed that the heat release in the end gas zone rises in two stages with a remarkable appearance of low temperature oxidation (LTO) at 2000 rpm, while a single stage heat release without apparent LTO process is presented at 4800 rpm due to the shorter residence time in the low temperature region.

Research on alternative fuels is necessary to reduce CO2 emissions. Hydrotreated Vegetable Oil (HVO) of light fuel physically improves spray and combustion characteristics. Fatty Acid Methyl Ester (FAME) is an oxygenated fuel and its combustion characteristics are chemically improved, although its spray characteristics such as penetration and atomization are deteriorated. The purpose of this study is to understand the effects of blending HVO, which has carbon neutral (CN) characteristics, with FAME, which also has CN characteristics, on spray and combustion characteristics, and to further improve emission such as THC and Smoke. This report presents the effect of the combination of improved spray characteristics and oxygenated fuel on emissions. Spray characteristics such as penetration, spray angle and spray volume were investigated by shadowgraph photography.

In a natural gas fueled engine ignited by diesel fuel, the addition of hydrogen to the engine could be a possible way to improve thermal efficiency and reduce unburned methane which has a warming potential many times that of carbon dioxide as it promotes a more rapid and complete combustion. This study carried out engine experiments using a single cylinder engine with natural gas and hydrogen delivered separately into the intake pipe, and with pilot-injection of diesel fuel. The percentages of hydrogen in the natural gas-hydrogen mixtures were varied from 0% to 50% of the heat value. The results showed that the hydrogen addition has an insignificant effect on the ignition delay of the diesel fuel and that it shortens the combustion duration. The increase in the hydrogen ratio decreased the unburned hydrocarbon emissions more than the reduction of the amount of natural gas that was replaced by the hydrogen.

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.

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.

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.

A spark assist system was installed in a gasoline direct-injection single-cylinder test engine with the aim of controlling the ignition timing and accomplishing combustion of gasoline fuel by auto/compression ignition. A primary reference fuel having an octane number of 90 (PRF 90) was used to evaluate experimentally the spark assist function for gasoline auto/compression ignition and to examine the feasibility of combustion with a short ignition delay equivalent to conventional diesel combustion using the engine system. An optically accessible single-cylinder test engine was also used to evaluate and investigate spark-assisted auto/compression ignition. Ignition timing controllability with combinations of spark and injection timings for gasoline auto/compression ignition was also investigated under different operating load conditions.

A comparative study was performed by use of blends of Jatropha oil-diesel fuel and Jatropha oil-kerosene in order to investigate the feasibility of direct utilization of Jatropha oil in a DI diesel engine. Experimental results at low load demonstrated that mixing 60 vol.% of Jatropha oil into both diesel fuel and kerosene gave less impact on indicated thermal efficiency, whereas further increase of Jatropha oil deteriorated it. Jatropha oil-kerosene decreased particulate matter compared to Jatropha oil-diesel fuel, although particulate matter increased with the increase of Jatropha oil fraction. At partial load where double injection was applied, mixing 80 vol.% of Jatropha oil gave no significant impact on indicated thermal efficiency, exhaust gas emissions and particulate matter and no significant difference was observed between diesel fuel blends and kerosene blends.

Effects of chemical reaction characteristics of premixed fuel were experimentally studied in a dual fuel compression ignition engine using port injection (PI) of gasoline-like component and direct injection (DI) of diesel fuel. Octane number of port injection fuels, direct injection timing and injection amount ratio between PI and DI were swept to assess the interaction between chemical reaction and mixture distribution in a combustion chamber. Chemical kinetic study using multi-zone modeling was also performed in order to explain experimental results under quiescent condition.

Ethanol is a promising alternative to fossil fuels because it can be made from biomass resources that are renewable. In the most cases, however, ethanol is blended with conventional fuels because of the limited amount of production. Ethanol-fuel blends are typically azeotropic and have a unique characteristic in vapor pressure and phase equilibrium, which is different from that of blends composed of simple aliphatic hydrocarbons. The current studies by the authors have developed a numerical vaporization model for ethanol-gasoline blends, which takes into account vapor-liquid equilibrium of azeotrope and high latent heat of vaporization of ethanol, in order to update the authors' multicomponent fuel spray model and to investigate effects of blending ethanol on droplet vaporization processes. In this paper, the developed vaporization model was validated through a comparison with experimentally-observed vaporization rate for single droplets of ethanol-n-heptane blends.

Jatropha biofuel is promising renewal oil to produce biodiesel fuel through transesterification method which is shown in many papers. The ideal diesel alternative fuel obtained considering Jatropha as materials is Fatty Acid Methyl Ester (FAME). It is more desirable than the viewpoint of economical efficiency and CO2 control to operate a diesel engine with Jatropha crude (JC) oil. It is the purpose of this research to examine a possibility of using advantageous JC oil direct use as diesel engine fuel, in consideration of the sustainable production of the Jatropha biofuel in Mozambique. The adaptability to the diesel engine of diesel oil and the mixed fuel of JC was examined. Jatropha crude oil contains phorbol ester (PEs) which is a promoter of cancer. Measurement of the concentration of PEs in an exhaust gas was performed using High Performance Liquid Chromatography (HPLC).

Ethanol is a promising alternative to fossil fuels because it can be produced from biomass resources that are renewable. Due to the amount of production, however, the usage would be limited to blends with other conventional fuels. Ethanol-fuel blends are azeotropic and have unique vaporization characteristics different from blends composed of aliphatic hydrocarbons, so that the present study developed a numerical scheme which takes into account the vapor-liquid equilibrium of azeotrope in order to update the author's original version of the multi-component fuel CFD model and to evaluate the effect of mixing ethanol into gasoline on the evaporation process. The numerical simulation was implemented for evaporating sprays of ethanol-n-heptane blends, which are injected through a single hole nozzle. In addition to the vapor-liquid equilibrium, the effect of the latent heat of vaporization was investigated.

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.

In this study, it is purpose to make clear the effect of cavitation phenomenon on the spray atomization. In this report, the cavitation phenomenon inside the nozzle hole was visualized and the pressure measurements along the wall of the nozzle hole were carried out by use of 25-times enlarged acrylic nozzle. For the representatives of regular gasoline, single and two-component fuels were used as a test fuel. In addition, various cavitating flow patterns same as experimental conditions were simulated by use of Barotropic model incorporated in commercial code of Star-CD scheme, and compared with experimental results.

Methyl butanoate (MB) and methyl decanoate (MD) are surrogates for biodiesel fuels. According to computational results with their detailed reaction mechanisms, MB and MD indicate shorter ignition delays than long alkanes such as n-heptane and n-dodecane do at an initial temperature over 1000 K. The high ignitability of these methyl esters was computationally analyzed by means of contribution matrices proposed by some of the authors. Due to the high acidity of an α-H atom in a carbonyl compound, hydroperoxy radicals are generated out of the equilibrium between forward and backward reactions of O₂ addition to methyl ester radicals by the internal transfer of an α-H atom in the initial stage of an ignition process. Some of the hydroperoxy methyl ester radicals can generate OH to activate initial reactions. MB has an efficient CH₃O formation path via CH₃ generated by the β-scission of an MB radical which has a radical site on the α-C atom to the carbonyl group.

LES of non-evaporative diesel spray have been performed to investigate the effects of breakup models of Modified TAB, WAVE and KHRT model on computational results. KIVALES that is LES version of KIVA code was used for base code. In our KIVALES, CIP scheme was incorporated in order to suppress the numerical diffusion. Results showed that the breakup model is significantly affected on the calculated spray shape, because the droplet diameter determined by breakup models affects on the transmittance of the droplet momentum into the ambient gas, the evolution of the vortex structure in the gas phase and the droplet dispersion by the vortex structure.

Authors propose the reformulation technique of physical properties of Biodiesel Fuel (BDF) by mixing lower boiling point fuels. In this study, waste cooking oil methyl ester (B100), which have been produced in Kyoto city, is used in behalf of BDF. N-Heptane (C7H16) and n-Dodecane (C12H26) are used as low and medium boiling point fuel. Mixed fuel of BDF with lower boiling point fuels have lighter quality as compared with neat BDF. This result is based on the chemical-thermo dynamical liquid-vapor equilibrium theory. This paper describes fundamental spray and combustion characteristics of mixed fuel of B100 with lower boiling point fuels as well as the reformulation technique. By mixing lower boiling point fuel, lighter quality fuels can be refined. Thus, mixed fuels have higher volatility and lower viscosity. Therefore, vaporization of mixed fuel spray is promoted and liquid phase penetration of mixed fuel shortens as compared with that of neat BDF.

It is thought that the synthetic gas, including hydrogen and carbon monoxide, has a potential to be an alternative fuel for internal combustion engines, because a heating value of the synthetic gas is higher than one of hydrogen or natural gas. A purpose of this study is to acquire stable auto-ignition and combustion of the synthetic gas which is supposed to be applied into a direct-injection compression ignition engine. In this study, the effects of ambient gas temperatures and oxygen concentrations on auto-ignition characteristics of the synthetic gas with changing percentage of hydrogen (H2) or carbon monoxide (CO) concentrations in the synthetic gas. An electronically-controlled, hydraulically-actuated gas injector was used to control a precise injection timing and period of gaseous fuels, and the experiments were conducted in an optically accessible, constant-volume combustion chamber under simulated quiescent diesel engine conditions.