Mixture Formation Process Research Articles

(2-09) Analysis of Turbulent Combustion in Idealized Stratified Charge Conditions((SI-3)S. I. Engine Combustion 3-Flow and Combustion)

The stratified charge combustion system has been widely studied due to the significant potentials for low fuel consumption and low exhaust gas emissions. The mixture formation process for a direct-injection stratified charge engine is influenced by various parameters such as the atomization, the fuel evaporation, and the in-cylinder gas motion at high temperature and high pressure conditions. It is difficult to observe the in-cylinder phenomena in such conditions and also challenging to analyze the following stratified charge combustion. Therefore, the combustion phenomena in idealized stratified charge conditions aiming to analyze the fundamental stratified charge combustion are examined. That is, an experimental apparatus which can control the mixture distribution and the gas motion at ignition timing was developed, and the effects of turbulence intensity, mixture concentration distribution, and mixture composition on stratified charge combustion were examined. The schematic of experimental setup is shown in Fig. 1. Three volumes separated by two partitions were evacuated and then three premixtures were charged simultaneously through pressure regulators. After the charging was completed, the gas motion generator was operated to control turbulence at spark timing. After partitions were removed, ignition was made. As a result, it was found that in stratified charge combustion using propane-air mixture, when the overall equivalence ratio, φo, is unity, no advantages by charge stratification is found, but when φo is set at 0.8 combustion is enhanced by additive effects combining turbulence with charge stratification, and that combustion is enhanced by strong turbulence in slightly stratified charge fields using methane-air mixture, but extending stratification brings unfavorable results compared with the homogeneous condition.

1221 液化CO_2混合燃料の噴霧構造に関する研究(OS-3 新燃料システム)

In the diesel engines, the trade-off relations for reducing both Soot and NO emissions cannot be avoid. In this study, it is proposed that a concept on simultaneous reduction of NO and Soot emissions in Diesel engine exhaust by use of the Diesel fuel oil (n-Tridecane) mixed with liquefied CO_2. The combustion process inside the S.I. engines and diesel engines seems to be affected mixture formation process of the injected or charged fuels. In addition, the spray structure of the liquefied CO_2 mixed fuel is difference from the spray structure of the diesel fuel. Therefore, in this paper, to be clarified the mixture formation process of the liquefied CO_2 mixed fuel, the vapor concentration distribution of n-Tridecane in liquefied CO_2 mixed fuel were observed by exciplex fluorescence method. And vaporization process of CO_2 in liquefied CO_2 mixed fuel were evaluated by measuring spray momentum.

C107 直噴ガソリン噴霧の混合気形成過程に関する研究(オーガナイズドセッション16 : 新世代エンジンのための燃焼改善と排気低減技術)

A dual-wavelength laser absorption-scattering (LAS) technique was developed to analyze the mixture formation process in a D.I. gasoline spray. P-xylene was used as a test fuel and the second harmonic (532nm) and the fourth harmonic (266nm) of an Nd:YAG laser were simultaneously illuminated the spray, which was injected into a high temperature and high pressure constant volume vessel. The dual-wave length LAS images were acquired by two CCD cameras and processed by a computer. The distributions of droplets and vapor concentrations in a D.I. gasoline spray were quantitatively analyzed.

1107 予混合圧縮着火機関における混合気形成過程に及ぼす噴射条件の影響(オーガナイズドセッション : 環境問題とエネルギー)

The mixture formation process in a premixed compression ignition engine was numerically analyzed. This study aimed to find out effective injection conditions for lean mixture formation with high homogeneity, since the NOx and soot emissions in the engine are closely related to the mixture homogeneity. To calculate fuel spray behavior, a practical computer code GTT (Generalized Tank and Tube) was employed. The effects of injection parameters, such as injection timing, initial droplet size, spray cone angle, injection velocity, nozzle type (pintle and hole) and injection position / direction, on the mixture homogeneity near ignition timing (or TDC) were investigated. This study concludes that high homogeneity lean mixture could be achieved with a pintle type nozzle by combining an advanced injection and small initial droplets in a small spray cone angle. Furthermore, the side injection concept with hole type nozzles using spray-to-spray impingement is effective for the lean near-homogeneous mixture formation.

Mixture Formation Process near Cavity Wall in a DI Diesel Engine with Transparent Cylinder and Piston.

The mixing of a diesel spray with air is generally determined by the injection parameters and characteristic of the air movement in the combustion chamber. The combustion chamber design can also help to form better mixtures. In this study, improvements in mixture formation was attempted by changing the combustion chamber geometry, injection pressure, and intake gas pressure in an actual diesel engine with transparent cylinder and piston arrangement. With this engine the front view and the side view photographs of the spray impinging on the wall and flowing over the bottom surface of combustion chamber were taken. From these results the overall air and fuel mass distributions were estimated.

シュリーレン像の画像処理によるエンジン筒内混合気分布の解析

A single cylinder visualization engine with the TCC (transparent collimating cylinder) was applied to the study of a direct-injection gasoline engine. Fuel sprays, mixture forma-tion and combustion process in the cylinder were observed using the schlieren method. The schlieren images were analyzed by image analysis technique. The shapes of the fuel spray are drastically changed with the injection timing ; namely oval shaped when in-jecting during the suction stroke, conical shaped when injecting near BDC, and bell shaped when injecting during the compression stroke. The fuel/air mixture formations also change with the injection timing. When the injection timing is late, the mixing of fuel and air is also late and the luminous region in the schlieren image of the mixture be-comes clear. In the case of the injection timing of 60 deg. before TDC, the injected fuel spray impinges on the top of the piston and the fuel/air mixture exists around the top of the piston, so that miss fire and abnormal combustion occur.

706 予混合圧縮着火機関における混合気形成過程の数値解析(OS-6 数値解析・シミュレーション)

706 予混合圧縮着火機関における混合気形成過程の数値解析(OS-6 数値解析・シミュレーション)

Investigation of the mixture formation inside a gasoline direct injection engine by means of linear Raman spectroscopy

Linear Raman scattering has been used for the investigation of the mixture formation inside an optically accessible gasoline direct injection spark ignition engine. The concentrations of O 2 , N 2 , H 2 O, and isooctane have been measured simultaneously and cycle resolved along a line of nearly 1 cm at three different locations inside the combustion chamber. By means of polarization-resolved detection optics, it was possible to separate the highly polarized Raman signals from unpolarized contributions from light emissions by stray light from surfaces, background luminescence, or laser-induced fluorescence. A separation between pure air and air/fuel mixture spectra was possible, indicating the influence of air entrainment on mixture formation. As all droplet influences on the taken spectra could be suppressed successfully, only pure gasphase spectra enter the air/fuel ratios evaluated. At the three selected locations (underneath the spark plug and displaced about 1.6 cm toward the intake and toward the outlet valve), the concentrations of all major species have been detected with high spatial and temporal resolution to observe the mixture formation process in a wide area inside the cylinder starting at fuel injection until shortly before ignition. Comparison with two-dimensional laser-induced exciplex fluorescence (LIEF) images allows improved interpretation of the phenomena taking place during mixture formation.

2206 スワールインジェクタによる混合気形成過程の数値解析

2206 スワールインジェクタによる混合気形成過程の数値解析

Effects of mixture formation on WOT output of a direct-injection gasoline engine

Abstract The effects of in-cylinder charge motion, fuel spray characteristics and piston crown geometry on WOT output of a direct-injection gasoline engine were investigated. The mixture formation process in the cylinder was analyzed by computer simulation and LIF visualization. The results made clear the technical factors for achieving sufficient fuel–air mixing in a DI gasoline engine with a bowl-in-piston geometry optimized for stratified charge combustion.

Multidimensional Modeling of Impinging Sprays on the Wall in Diesel Engines

This article summarizes model analysis of the dispersion process of a Diesel spray on the wall surface in order to simulate the spray-wall interaction process in Diesel engines. The mixture formation process near the wall of the piston cavity affects the combustion process and the hydrocarbon or soot formation process through the quenching of the mixture and flame at the wall surface. In particular, mixture burning occurs mainly near the cavity wall through the whole combustion period in the case of high pressure fuel injection. In this article, representative modeling approaches on spray-wall interaction process including the film flow formation are summarized briefly. Then, our models of spray impingement for low/high-temperature models including the process of fuel film formation, film breakup, wall-drop/film heat transfer, and droplet breakup owing to the solid-liquid interface boiling are introduced with the comparison of experimental results. This review article includes 83 references.

C502 Exciplex蛍光法を用いた非定常蒸発ディーゼル噴霧の解析

The characteristics of combustion process in an internal combustion engine are affected by the mixing process between injected fuel and ambient gas. Therefore, it is necessary to understand the mixture formation process of diesel spray. In this study, the spray structure was visualized by the exciplex fluorescence method, which provides the simultaneous 2-D images of vapor and liquid phase in the spray, in order to discuss the mixture formation process of diesel spray. In addition, the vapor concentration using Lambert-Beer's law was quantitatively obtained from the fluorescence intensity measured in the spray. The fractal analysis to 2-D images measured by exciplex fluorescence method was carried out for turbulence analysis.

Quantitative 2-D Fuel Distribution Measurements in a Direct-Injection Gasoline Engine Using Laser-Induced Fluorescence Technique.

To improve the accuracy of fuel concentration measurements in a direct-injection gasoline engine by LIF (laser-induced fluorescence) technique, two approaches have been couducted. The combination of acetone as the fluorescence tracer of fuel and 266 nm as the excitation wavelength was used for the first approach in order to minimize the error caused by the temperature dependence of the LIF intensity. The second approach was the correction of the equivalence ratio obtained from the raw LIF image for the severe temperature distribution caused by evaporation and superheating of the injected fuel. The temperature distribution in the mixture was calculated ; then the equivalence ratio was corrected for the effects of air density variation and the remaining LIF temperature dependence. This improved techanique was applied to the quantitative analysis of the mixture formation process in a visualized direct-injection gasoline engine both under early and late injection conditions.

Numerical Analysis and Vapor Concentration Measurement on the Evaporation Process of Multi-component Fuel.

In previous multi-dimensional modeling on spray dynamics and vapor formation, single component fuel with pure substrance has been analyzed to assess the mixture formation process. Then it shold be expected that the evaporation process could be performed for the multi-component fuel such as actual Gasoline and Diesel gas oil. In this study, vapor liquid equilibrium prediction was conducted for multi component fuels such as 3 and 10 components mixed solution with ideal solution analysis and non ideal solution analysis. And the computation of distillation characteristics was conducted for the steady state fuel conditions to understand the evaporation process. As a result, calculated distillation characteristics is consistent well with experiment results. Further the vapor concentration was measured for the analysis of the binary fuel spray using IR absorption measurement method.

Development of instrument for measurement of fuel–air ratio in vicinity of spark plug: application to DI gasoline engine

An instrument to measure time-resolved fuel–air ratio in the vicinity of a spark plug was developed. Properties of absorption and scattering at the wavelengths of visible and infrared rays were utilized to determine the fuel–air ratio in the mixture including liquid and vaporized fuel. The measurement error of the instrument was within 10% as a result of comparison between the overall and the measured fuel–air ratio at the vicinity of the spark plug under the inlet port injection, which forms a relatively homogeneous mixture. The instrument was applied to a direct injection gasoline engine and the mixture formation process was clarified.

Development of Instrument for Measurement of Fuel-Air Ratio in the Vicinity of Spark Plug. Application to DI Gasoline Engines.

An instrument to measure time-resolved fuel-air ratios in the vicinity of a spark plug was developed. Absorption and scattering at the wavelengths of visible and infrared rays were utilized to determine the fuel-air ratios in the mixture including liquid and vaporized fuel. The measurement error of the instrument was estimated within 10% from comparison between the overall and the measured fuel-air ratios at the vicinity of the spark plug with inlet port injection which froms homogeneous mixture. The instrument was applied to direct injection gasoline engines and the mixture formation process was discussed.

Mixture of triethylamine (TEA) and benzene as a new seeding material for the quantitative two-dimensional laser-induced exciplex fluorescence imaging of vapor and liquid fuel inside SI engines

A mixture of triethylamine (TEA) and benzene in iso-octane has been proven to be a suitable seeding material for the study of the gasoline fuel mixture and evaporation processes under engine-like conditions. Laser-induced fluorescence (LIF) of the exciplex-forming mixtures of TEA and benzene has been investigated using a KrF-excimer laser at 248 nm as an excitation source. The dopants have physical and chemical properties that match well with the model fuel iso-octaine and show only low absorption at the excitation wavelength. These are important criteria for materials to be used as tracer substances for the study of evaporation and mixture formation processes in SI engines. In the liquid phase, the mixture of the two tracer substances with iso-octane shows a broadband fluorescence spectrum which is red-shifted with respect to the vapor-phase fluorescence. This allows a spectrally separated detection of the local distributions of the liquid and the vapor phases by using appropriate bandpass filters. Vapor-phase fluorescence in the presence of synthetic air, oxygen, nitrogen, carbon dioxide, and water vapor under variation of pressure, concentration, and temperature was measured in a heatable high-pressure chamber. It has been found that oxygen is the only molecular species which induces collisional quenching of the fluorescence emissions. Hence, using the described tracer system, a quantitative detection of vapor-phase concentrations and fuel/air-ratios under engine like conditions is possible. It is demonstrated that the fluorescence intensity is directly proportional to the fuel/air-ratio and independent of pressure for pressures higher than 3 bar. The temperature dependence of the fluorescence intensity has been studied in a temperature range from 398 to 523 K. With increasing temperature, a systematic decrease of the fluorescence intensity has been detected, which, however, is still directly proportional to the fuel/air ratio. An application of the newly developed tracer combination for the quantitative two-dimensional imaging of the fuel/air-ratios in the vapor-phase and the simultaneous, spectrally separated detection of the liquid phase inside an SI engine is presented.

Mixture formation process and combustion process of direct injection S.I. engine Souichi Matsushita, Kiyoshi Nakanishi, Takeshi Gohno, Daisaku Sawada (Toyota Motor Corp.)

Mixture formation process and combustion process of direct injection S.I. engine Souichi Matsushita, Kiyoshi Nakanishi, Takeshi Gohno, Daisaku Sawada (Toyota Motor Corp.)

Simultaneous Reduction of NOx and Soot in Diesel Engines Using a New Mixture Preparation Method.

We describe an experimental study on the simultaneous reduction of NO x and soot in diesel engines achieved using a new mixture preparation method. To produce a lean uniform mixture, a new type of injection equipment was used with various injection timings. Between the late and very early injection timings, there was an injection timing range at which the amount of NO x produced was extremely low and soot was not emitted. NO x production was suppressed to a level one hundredth that of conventional DI diesel engines. However, with increasing load, NO x production increased sharply and strong diesel knocking occurred. This indicated that NO x production was strongly influenced by the process of mixture formation.

Simultaneous Reduction of NOx and Soot in Diesel Engines Using a New Mixture Preparation Method.

We describe an experimental study on the simultaneous reduction of NO x and soot in diesel engines achieved using a new mixture preparation method. To produce a lean uniform mixture, a new type of injection equipment was used with various injection timings. Between the late and very early injection timings, there was an injection timing range at which the amount of NO x produced was extremely low and soot was not emitted. NO x production was suppressed to a level one hundredth that of conventional DI diesel engines. However, with increasing load, NO x production increased sharply and strong diesel knocking occurred. This indicated that NO x production was strongly influenced by the process of mixture formation.