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In order to measure the droplets and vapor concentration inside a fuel spray, a dual-wavelength laser absorption-scattering technique was developed using the second harmonic (532nm) and the fourth harmonic (266nm) of a Nd:YAG laser and using dimethylnaphthalene as the test fuel. The investigation results show that dimethylnaphthalene, which has physical properties similar to diesel fuel, is almost transparent to visible light near 532nm and is a strong absorber of ultraviolet light near 266nm. Based on this result, the vapor concentration in a fuel spray can be determined by the two separate measurements: a transmission measurement at a non-absorbing wavelength to detect the droplets optical thickness and a transmission measurement at an absorbing wavelength to detect the joint vapor and droplets optical thickness. The droplets density can be determined by extinction imaging through the transmission at the non-absorbing wavelength.

Quantitative imaging of the fuel concentration distribution was made in the combustion chamber of a propane-fueled spark ignition (SI) engine with the employment of laser-sheet-induced Rayleigh scattering technique for realizing the remote, nonintrusive and highly space- and time-resolved measurement. The original engine was modified to introduce YAG laser-induced sheet light into the combustion chamber and the scattered light was captured by a CCD camera fitted with a gated double-micro- channel plate image intensifier. The measurements were done at the crank angle of 270°ATDC in the combustion chamber of the engine motored at 200rpm with an air fuel ratio of 13 for various injection timing, injection direction and intake flow. The results show that with an appropriate matching of fuel injection timing, injection direction and intake flow, a stratified distribution of the fuel concentration can be realized.

The power output performance of the rotary engine can be improved when the dynamic effects of intake and exhaust systems are utilized. Previous studies have shown that one-dimensional gas exchange process simulations are effective in developing these systems. However, this type of simulation is difficult to apply to the peripheral port type rotary engine because of the simultaneous gas exchange between one port and two combustion chambers. To account for this, a boundary model connecting the pipe and plenum chambers was developed. This study shows the validity of this new model and the successful application of the simulation to the engine.

The two-dimensional distributions of the liquid phase temperatures in diesel sprays injected into high-pressure and high-temperature environments were measured using the laser-induced fluorescence technique. The liquid fuel (n-hexadecane) was doped with pyrene(C16H10). The fuel spray doped with pyrene was injected under a high-pressure of 3.1MPa and a high-Temperature of 773K. The evaporating diesel spray was excited by laser radiation at 266nm, and the resulting fluorescence was imaged by an intensified CCD camera. The fluorescence intensity ratios of the pyrene monomer and excimer emissions have temperature dependence, and were used to determine the liquid phase temperatures in the diesel sprays. The cross-sectional distribution of the liquid phase temperature was estimated from the fluorescence images by the temperature dependence of the intensity ratio.

To investigate NO formation in a combustion flame, PLIF (Planar Laser-Induced-Fluorescence) technique was applied to measure the NO fluorescence distribution in a constant-volume combustion chamber and in a sparkignition engine. The NO fluorescence distribution was taken by an image intensified CCD camera. In the constant-volume combustion chamber, the high NO fluorescence intensity was concentrically observed in the thin flame zone along the flame front. In postflame gas behind the flame zone, the NO fluorescence was widely distributed with weak intensity. In the case of the engine, the fluorescence was distributed in the broad flame zone. The fluorescence intensity had high value near the flame front, and decreased from the flame front to the postflame gas. As the equivalence ratio was changed, the fluorescence intensity reached maximum value at slightly lean condition.

Planar laser-induced fluorescence (PLIF) technique was employed to perform the quantitative measurements of the cyclic variation of mixture concentration in the combustion chamber of a spark ignition (SI) engine. Nitrogen dioxide was used as the fluorescence tracer to simulate the fuel vapor. A Nd:YAG laser operated at its second harmonic wavelength was employed as the light source. The original engine was modified to introduce laser sheet light into the combustion chamber and the induced fluorescence was captured by a CCD camera fitted with a gated image intensifier. The measurements were done at the engine crank angles of 180° ∼ 300° ATDC with the engine speeds of 200 ∼ 400 rpm and the injection timings of -70 °, 50° and 100° ATDC. A theoretical analysis was made to describe the cyclically varying characteristics of the mixture concentration.

The International Lubricant Standardization and Approval Committee (ILSAC) ATF subcommittee members have compared the two oxidation bench test methods, Aluminum Beaker Oxidation Test (ABOT) and Indiana Stirring Oxidation Stability Test (ISOT), using a number of factory-fill and service-fill ATFs obtained in Japan and in the US. In many cases, the ATFs were more severely oxidized after the ABOT procedure than after the same duration of the ISOT procedure. The relative severity of these two tests was influenced by the composition of the ATFs. The bench test oxidation data were compared with the transmission and the vehicle oxidation test data.

The effects of engine parameters, such as spray characteristics and combustion chamber geometry on performance and exhaust emissions in a small D.I. diesel engine were investigated to find out the optimum way of improving the engine. Diesel spray injected into a high-pressure vessel was photographically analyzed to guess the spray behavior in a firing diesel engine. The ratio of hole length to the diameter of a nozzle (L/D) was varied from 3 to 7 as the main parameter of the nozzle. Piston cavity diameter and intake swirl were chosen as the other parameters. The effect of the above parameters was investigated in terms of brake specific fuel consumption (BSFC), exhaust smoke, nitric oxides (NOx) and total hydrocarbon (THC). The L/D of the nozzle is concluded to be of major importance in terms of BSFC and THC emission. Smaller piston cavity diameters lead to lower exhaust smoke, but to a higher level of NOx emission.

Spray combustion processes of palm oil biodiesel (PO) and conventional diesel fuels were simulated using the CONVERGE CFD code. Thermochemical and reaction kinetic data (115 species and 460 reactions) by Luo et al. (2012) and Lu et al. (2009) (68 species and 283 reactions) were implemented in the CONVERGE CFD to simulate the spray and combustion processes of the two fuels. Tetradecane (C14H30) and n- heptane (C7H16) were used as surrogates for diesel. For the palm biodiesel, the mixture of methyl decanoate (C11H20O2), methyl-9-decenoate (C11H19O2) and n-heptane was used as surrogate. The palm biodiesel surrogates were combined in proportions based on the previous GC-MS results for the five major biodiesel components namely methyl palmitate, methyl stearate, methyl oleate, methyl linoleate and methyl linolenate.

A mathematical model was developed for predicting the concentration of exhaust nitric oxide, soot and other emissions in a direct injection diesel engine. In the model, it was emphasized to describe the phenomena occurring in the combustion chamber from the microscopic point of view. The prediction was based on the knowledges concerning a single droplet as well as the droplet size distribution in a fuel spray and the spatial and temporal distribution histories of fuel in a combustion chamber. The heterogeneous field of temperature and equivalence ratio, and uniform pressure in the cylinder were postulated. The heat release model gives the burning rate of injected fuel and pressure and temperature history in the cylinder. The concentration of nitric oxide and soot in the cylinder was predicted by the emission formation model.

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.

This paper presents the experimental analysis for the turbulence in the combustion chamber of a direct injection (D.I.) diesel engine. A dual beam mode, forward-scattering laser doppler velocimeter was applied to the flow measurement in a four-stroke, single-cylinder direct injection diesel engine of 110 mm bore and 125 mm stroke. The turbulence component was separated from instantaneous velocity using a high-pass filter. As a result, the difference in turbulent intensity between the intake and compression processes was discussed. Also, the effect of intake port and piston cavity shapes, the compression ratio and the engine speed on the turbulent intensity were clarified. In addition, the empirical equation for the decay of turbulent intensity in the compression process was expressed by a function of the Reynolds number based on the mean swirling flow.

In-cylinder flow and fuel behaviors in the piston cavity of a direct injection SI engine were measured by using PIV and LIF. The effect of the cavity wall on the mixing process was the focus in this study. The optical prism was installed inside piston to observe air flow and fuel behavior on a horizontal plane of the cavity combustion chamber in the piston. The fuel spray mainly impinged on the cavity bottom surface and rolled up along the cavity wall near the spark plug by it's own momentum. Then it was evaporated and diffused by swirl flow. The effect of fuel injection timing on the mixing process was also investigated. Earlier injection timing made fuel momentum small up to the time of impingement. Therefore, the fuel vapor was considerably diffused by swirl flow in the piston cavity and fuel vapor concentration near the spark plug was low.

The sequential fuel injection, in which fuel is injected into swirl being generated for mixture stratification, was used to pursue the potential of a lean burn engine for its performance improvement. As a result, it has been found that the most effective method to increase thermal efficiency while reducing NOx emission level is to combine a high-compression compact combustion chamber located on exhaust valve side in cylinder head with DICS (Dual induction Control System). This method was used to build a high-compression lean burn concept vehicle, which was evaluated for compliance to various emission standards. Testing showed that the concept vehicle can improve fuel economy by 10.5% on the Japanese 10-mode cycle, by 8.3% on the ECE mode cycle, and by 6.3% on the U.S. EPA test mode cycle while meeting respective emission standards.

Subjective evaluation tests of “Acceleration Performance Feeling” with a driving simulator have been carried out on a rotary engine sports car. Additionally, although the test condition is limited, a test on an in-line four-cylinder engine sedan has been carried out. Influencing factors were analyzed through the experimental design and the influences of acceleration, gas pedal controllability, engine sound and their interactions were quantified. As the result, it has been found that the interactions must be considered in addition to main effect of each factor to improve users' evaluation especially on a rotary engine sports car. Furthermore, it is concluded that influencing factors are different between a rotary engine sports car and an in-line four-cylinder engine sedan.

A comparison of spray characteristics was conducted between single- and multi-hole injectors. A commercial software (AVL FIRE) was used to investigate the internal flow inside the sac volume, as well as the initial spray behavior at 1 mm downstream of the nozzle exit. Microscopic imaging was applied to observe the spray dispersion angle (spray cone angle) at the vicinity of the nozzle. Laser absorption scattering (LAS) technique was implemented for measuring the mixture concentration. Three injection quantities, namely 0.5, 2.5, and 5.0 mg/hole, were selected to observe the differences between transient and quasi-steady spray. The vapor penetration at the initial stage of the injection was greater for single-hole than that of multi-hole injector due to faster fuel pressure build-up process inside the sac volume.

An early formation process of the spray, which was injected by a high-pressure swirl-type injector that is widely used in direct injection spark ignition (DISI) gasoline engines, was investigated through image analyzing techniques. The sprays were illuminated both by an Nd:YAG laser light sheet for getting the spray tomograms and by a tungsten lamp for getting the scattered back light shadow images of the sprays. The sprays were imaged by using a high-resolution CCD camera and a high-speed digital imaging system. The early development aspects of the spray were investigated in detail through the measurement of the tip penetration, cone angle and width of the early spray. At the start of injection, the liquid column emerges first, and it forms the “pre-swirl spray” without the swirl component. Following the liquid column, the liquid sheet emerges, however its radial velocity component is weak to form the complete hollow-cone spray. This spray changes into the “weak-swirl spray”.

Increasing the injection pressure and splitting the injection stage are the major approaches for a diesel engine to facilitate the fuel-air mixture formation process, which determines the subsequent combustion and emission formation. In this study, the free spray was injected by a single-hole nozzle with a hole-diameter of 0.111 mm. The impinging spray, formed by a two-dimensional (2D) piston cavity having the same shape as a small-bore diesel engine, was also investigated. The injection process was performed by both with and without pre-injection. The main injection was carried out either as a single main injection with injection pressure of 100 MPa (Pre + S100) or a split main injection with 160 MPa defined by the mass fraction ratio of 3:1 (Pre + D160_3-1). The tracer Laser Absorption Scattering (LAS) technique was adopted to observe the spray mixture formation process. The ignition delay/location and the soot formation in the spray flame were analyzed by the two-color method.

A pancake-type constant-volume combustion chamber was used to investigate the combustion and NOx emission characteristics of propane-air and hydrogen-air mixtures under various charge stratification patterns, which were obtained by variations of the initial charge and injected mixture concentrations and the ignition spark timing. A planar laser-induced fluorescence from nitrogen dioxide as gas fuel tracer was applied to measure the mixture distribution in the test chamber. The second harmonic output of pulsed Nd; YAG laser was used as a light source for fluorescence excitation. The fluorescence images were corrected by a gated image-intensified CCD camera. The quantitative analysis of fuel concentration was made possible by the application of linearity between fluorescence intensity and NO2 concentration at low trace level.

As a technology to reduce the heat loss of engines, heat insulation coating to the surface of combustion chamber has been received a lot of attention. In order to maximize the thermal efficiency improvements by the technology, it is important to clarify the location where heat insulation coating can reduce heat loss more effectively, considering the impact on abnormal combustion etc. In this study, transient behavior of wall heat flux distribution on the piston was analyzed using 3D Computational Fluid Dynamics (CFD) for three combustion modes (spark ignition combustion (SI), homogenous charge compression Ignition (HCCI) and spark controlled compression ignition (SPCCI)).