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Diesel engine has fuel combustion capability in various high density oil such as residual fuels or biofuels derived from fossil or living matter. But for commercial use, these fuels except bio diesel fuel (BDF) should be heated, separated and filtered by equipment and dosed or mixed with additive or distillate oil etc. before being supplied to the engine in order to improve combustibility. This study aims to illuminate fuel characteristic of blend contained woody pyrolysis oil (WPO) which is high viscosity and incombustible, and dimethyl ether (DME) whose emission of combustion has no soot particle. This paper describes thermo-physical property of neat WPO and the blend on the basis of the evaluation of fuel fluidity by measurement and calculation of viscosity. According to the result, it was confirmed that the fluidity of WPO was improved by mixing DME and the approximate viscosity expressions at any temperature of WPO and the blend were good accuracy.

Fossil fuels are the dominant source of energy today with the problem of their supply depletion becoming a global issue. Since stable energy supplies are necessary in order to sustain the activities of mankind, conservation of petroleum fuel and finding an appropriate substitute are critical. Additionally, solutions to global environmental pollution problems are simultaneously needed, such as the Kyoto protocol for global warming. The aim of this study is to investigate whether the combustion state of bunker oil can be improved by the mixing of DME (dimethyl ether), which is considered as a possible alternative fuel. The kinematic viscosity of DME blended fuel, as well as the engine performance characteristics of single cylinder direct injection diesel engine, was measured experimentally. In the kinematic viscosity measurement, a pressure cell type viscosity measurement system was established in order to apply the volatile DME blended fuel.

Diesel engine has been used as a power source in many fields, because of its high thermal efficiency and durability. But its exhaust gas emissions, such as NOx or Particulate Matter, are considered as the matter which brought the air pollution. Thus, it is needed to reduce such harmful matters to agree with the level set by the legislation. In this study, the engine performance of the mixed fuel comprised of DME (Dimethyl Ether) and marine diesel oil was experimentally examined. Because of the molecule properties of DME, it emits no soot in combustion. At the atmospheric condition, DME can be liquefied with rising in its pressure. When liquefied DME is injected in combustion chambers, the flashing energy is supposed to be useful as the atomization of other liquid fuels. A small high-speed direct injection diesel engine was used as the test engine. Its bore and stroke were 92mm and 96mm, and the compression ratio was 17.7.

Some volumes of gas oil and ethanol were mixed to the rape-seed oil to examine the engine performance characteristics. A 4-cycle indirect injection diesel engine was used as the test engine, and exhaust emissions were measured together with cylinder pressure history in variation of the engine loads. The single droplet combustion test was also carried out. Combustion processes in the heated constant volume vessel were observed by using of a high-speed video camera. From the experiments, it is obtained that rape-seed oils take longer combustion duration compared with gas oils. And addition of ethanol promotes the micro explosion of fuel droplets. These features affect to the properties of exhaust emissions from the engine.

This study proposes a hybrid model which consists of modified TAB(Taylor Analogy Breakup) model and DVM(Discrete Vortex Method). In this study, the simulation process is divided into three steps. The first step is to analyze the breakup of droplet of injected fuel by using modified TAB model. The second step based on the theory of Siebers' liquid length is analysis of spray evaporation. The liquid length analysis of injected fuel is used for connecting both modified TAB model and DVM. The final step is to reproduce the ambient gas flow and inner vortex flow injected fuel by using DVM. In order to examine the hybrid model, an experiment of a free evaporating fuel spray at early injection stage of in-cylinder like conditions had been executed. The numerical results calculated by using the present hybrid model are compared with the experimental ones.

This paper studies the effect of nozzle geometry on the flow characteristics inside a diesel fuel injection nozzle and correlates to the subsequent atomization process under different operating conditions, using simple turbulent breakup model. Two kinds of nozzles, valve covered orifice (VCO) and mini-SAC nozzle, with various nozzle design parameters were studied. The internal flow inside the nozzle was simulated using 3-D computational fluid dynamics software with k-ε turbulence model. The flow field at the nozzle exit was characterized by two parameters: the fuel discharge coefficient Cd and the initial amplitude parameter amp0. The latter parameter represents the turbulence characteristics of the exit flow. The effects of nozzle geometry on the mean velocity and turbulent energy distribution of the exit flow were also studied. The characteristics of the exit flow were then incorporated into the spray model in KIVA-II to study the effect of nozzle design on diesel spray behavior.

This paper deals with the particle distribution in Diesel spray under the non-evaporating condition from the analytical aspect based on our experimental results. In the analysis, TAB method of KIVA II code and the k-ε turbulent model were used, and the mono-disperse distribution of the initial parcel's diameter, whose size equals to the nozzle hole diameter, was utilized in conjunction with the breakup model. The size distribution of atomized droplets (i.e. the χ-squared distribution function) is justified with the degree of freedom. It is shown that the ambient gas, which is initially quiescent, is induced and led to a turbulent gas jet. The turbulent gas jet which has a equivalent momentum with the Diesel spray was also examined by Discrete Vortex method. The quantitative jet growth was shown to be possible for the estimation and determination in its initial boundary values at the nozzle.

The spray structure under the pressurized atmosphere at a room temperature was examined by the various photographic methods. The fuel flow inside the nozzle was investigated by the transparent model nozzles. The experimental analysis of sprays yielded the spray dispersing angle, the distribution of fuel droplets inside the spray and the jet intact core length. The obtained results of those spray characteristics showed that the spray structure is divided into two spatial regimes due to their formation mechanisms. Within 10 mm from the nozzle, the spray dispersion is dominated by the turbulent states of fuel which are initiated inside the nozzle. At distance from the nozzle z > 20 - 40 mm, the spray consists of an induced gas vortex street whose length is about half of the spray width. It is proposed that the kinematic viscosity of ambient gas is a important factor which rules the process of momentum exchange form the fuel jet to the ambient gas.

In this paper, spray characteristics were examined to deduce the effect of ambient gas properties. Considered ambient properties were the viscosity μa and density ρa, and thus the kinematic viscosity νa. The objective of this paper is to reveal the effect of compressibility of the ambient gas to spray formation. In the experiments, the changed ranges were And a standard-sac volume nozzle of hole diameter dn =0.25 mm (ln/dn=3.0) was used at constant injection pressure difference (Δp=16.2 MPa). Also the injection pressure was varied in the range of 55 to 120 MPa with a mini-sac volume nozzle of hole diameter dn =0.20 mm (ln/dn =5.5). Several different gases were used to change the ambient viscosity at a room temperature. From the experiments, it is obtained that larger the viscosity, the more the spray spreads in the radial direction, thus the spray angle gets larger and the tip penetration became shorter.