Refine Your Search


Search Results

Technical Paper

Development of a High Sensitivity and High Response Portable Smoke Meter

The filtration efficiency of a DPF drops when it suffers a failure such as melting and cracks during regeneration. And then, on-board diagnostics (OBD) device has become needed worldwide to detect a DPF failure. In the development of an OBD soot sensor, evaluation of the sensor demands a portable instrument which can measure the soot concentration for on-board and in-field use. Some of the emission regulations require the in-field emission measurements under normal in-use operation of a vehicle. This study is intended to develop a high sensitivity and high response portable smoke meter for on-board soot measurements and a reference to OBD soot sensors under development. The smoke meter accommodates a 650 nm laser diode, and its principle is based on light extinction in high soot concentration range and backward light scattering for low soot concentration measurement.
Technical Paper

Comprehensive Characterization of Particulate Emissions from Advanced Diesel Combustion

The applicability of several popular diesel particulate matter (PM) measurement techniques to low temperature combustion is examined. The instruments' performance in measuring low levels of PM from advanced diesel combustion is evaluated. Preliminary emissions optimization of a high-speed light-duty diesel engine was performed for two conventional and two advanced low temperature combustion engine cases. A low PM (<0.2 g/kg_fuel) and NOx (<0.07 g/kg_fuel) advanced low temperature combustion (LTC) condition with high levels of exhaust gas recirculation (EGR) and early injection timing was chosen as a baseline. The three other cases were selected by varying engine load, injection timing, injection pressure, and EGR mass fraction. All engine conditions were run with ultra-low sulfur diesel fuel. An extensive characterization of PM from these engine operating conditions is presented.
Technical Paper

A Numerical Simulation of Ignition Delay in Diesel Engines

To investigate the ignition process in a diesel spray, the ignition in a transient fuel spray is analyzed numerically by a simple quasi-steady spray model coupled with the Shell kinetics model at various operating conditions and validity of this model is assessed by a comparison with existing experimental data. The calculated results indicate that the competition between the heat absorption of fuel and the hot air entrainment determines the equivalence ratio of mixtures favorable for the ignition to occur in the shortest time.
Technical Paper

Ignition, Combustion and Emissions in a DI Diesel Engine Equipped with a Micro-Hole Nozzle

In an attempt to achieve lean combustion in Diesel engines which has a potential for simultaneous reduction in no and soot, the authors developed a micro-hole nozzle which has orifices with a diameter as small as 0.06 mm. Combustion tests were carried out using a rapid compression-expansion machine which has a DI Diesel type combustion chamber equipped with the micro-hole nozzle. A comparison with the result of a conventional nozzle experiment revealed that the ignition delay was shortened by 30 %, and in spite of that, both peaks of initial premixed combustion and diffusion combustion increased significantly. The combustion in the case of the micro-hole nozzle experiment was accompanied with a decrease in soot emission, whereas an increase in NO emission.
Technical Paper

A Study on Ignition Delay of Diesel Fuel Spray via Numerical Simulation

To investigate the ignition process in a diesel spray, the ignition in a transient fuel spray is analyzed numerically by a discrete droplet spray model (DDM) coupled with the Shell kinetics model at various operating conditions. Predicted results show that the fuel mixture injected at the start of injection, which travels along midway between the spray axis and the spray periphery, contributes heavily to the first ignition in a spray. The equivalence ratio and temperature of the first ignited mixture are kept nearly constant until the start of hot ignition. The temperature of the first ignited mixture is kept at a constant value of higher temperature than the thermodynamic equilibrium temperature of the mixture before the hot ignition starts. The equivalence ratio of the first ignited mixture is around 1.6 at initial gas temperatures between 750 K and 850 K.
Technical Paper

Measurement of Rate of Multiple-Injection in CDI Diesel Engines

The injection rate meter based on W. Zeuch's method was improved to meet the recent requirement for precise measurement of the multiple injection rate and amount in CDI (Common rail Direct Injection) diesel engines. A pressure sensor with a high sensitivity was added to measure the small pressure increase due to the pilot injection and after injection. At the same time a flow meter having a high accuracy was installed in the discharge pipe line to obtain a correction factor to the modulus of elasticity of volume. As a result it became possible to measure the multiple injection amount at an accuracy of ±0.2mm3/stroke in a range up to 40mm3/stroke.
Technical Paper

Measurement of the Rate of Multiple Fuel Injection with Diesel Fuel and DME

The accuracy of the injection rate meter based on W. Zeuch's method in the measurement of multiple injection rate and amount was calibrated using a small cam driven piston that is driven by an electric motor. For the pre- or early-injection, a sensor with a high sensitivity can be applied to measure the small pressure increase due to the small injection amount. In case of the multiple injection that has the post and/or late injection, a pressure sensor with a low sensitivity must cover not only the large pressure increase due to the main injection but also the small pressure increase due to the post and/or late injection because the output of the high sensitivity sensor is saturated after the main injection. So the linearity of the low sensitivity pressure sensor was calibrated with the cam driven piston prior to the experiment with the actual injection system.
Technical Paper

An Air Cell DI Diesel Engine and Its Soot Emission Characteristics

A DI diesel engine with an air cell was developed as one of the combustion systems for reducing soot emission from diesel engines: The air is accumulated in the air cell during the compression stroke and is injected into the main chamber during a period after the end of injection. The air jet stirs the stagnant flame and promotes soot oxidation. A comparative experiments with the conventional system made it clear that the air-cell system effectively reduces soot emission at a medium and high load condition.
Technical Paper

Measurement of Droplet Diameter and Fuel Concentration in a Non-Evaporating Diesel Spray by Means of an image Analysis of Shadow Photographs

A new method was developed which measures the atomization characteristics of a non-evaporating, axisymmetric diesel spray: The film image density of the high speed focused shadow photographs of a spray was analyzed based on the incident light extinction principle, and the Sauter mean diameter and the fuel concentration distribution were calculated from the image data and the measured injection rate with the help of the onion peeling model. The measured Sauter mean diameter showed good agreement with the diameter measured by the conventional immersion method, and also the measured fuel concentration distribution along the spray axis was proved to coincide well with the predicted result by Che one dimentional quasi-steady jet model except at a region near the spray tip.
Technical Paper

A Photographic and Thermodynamic Study of Diesel Combustion in a Rapid Compression Machine

A diesel spray and flame in a quiescent atmosphere were realized without interference with combustion chamber walls in a newly constructed rapid compression machine. High speed shadow photography and pressure measurement were employed to obtain data for calculating the amount of air entrainment into the the flame and spray. From a comparison of air entrainment between the flame and spray, it turned out that when ignition delay becomes longer air entrainment into flames is promoted by the thermal expansion of multi-points ignition sources in the central region of the spray.
Technical Paper

Two–Dimensional Imaging of Formaldehyde Formed During the Ignition Process of a Diesel Fuel Spray

The time of, and location where ignition first occurs in a diesel fuel spray were investigated in a rapid compression machine (RCM) using the two–dimensional techniques of silicone oil particle scattering imaging (SSI), and the planar laser induced fluorescence (LIF) of formaldehyde. Formaldehyde has been hypothesized to be one of the stable intermediate species marking the start of oxidation reactions in a transient spray under compression ignition conditions. In this study, the LIF images of the formaldehyde formed in a diesel fuel spray during ignition process have been successfully obtained for the first time by exciting formaldehyde with the 3rd harmonic of the Nd:YAG laser. SSI images of the vaporizing spray, and the LIF images of formaldehyde were obtained together with the corresponding time record of combustion chamber pressures at initial ambient temperatures ranging from 580 K to 790 K.
Technical Paper

LDA Measurement and a Theoretical Analysis of the In-Cylinder Air Motion in a DI Diesel Engine

The swirl velocity in the combustion bowl of a DI diesel engine was measured by means of laser doppler anemometry, varying the swirl intensity and engine speed. At the same time an axisymmetrical two dimensional laminar model for simulating the in-cylinder air motion was presented. The boundary condition of the flow near the wall was investigated by a comparison of predicted and measured swirl velocity, and as a result the free slip condition was found to be suitable for the present model. A comparison between measured and theoretical swirl velocity revealed that the secondary flow in the combustion bowl induced by an interaction between the squish and swirl flow transfers swirl velocities from points to points, causing a complex time variation of the swirl velocity at an observing point.
Technical Paper

Rate of Heat Release and Its Prediction of a Diesel Flame in a Rapid Compression Machine

The rate of heat release of a free diesel flame was measured with a rapid compression machine which has a compression ratio of 14.7 and a combustion chamber with a diameter of 196 mm and a thickness of 40 mm. Basing on the experimental observations of the high speed photographs of the spray and flame, the authors proposed a phenomenological model for predicting the rate of heat release of the flame. The model consists of three basic models; air entrainment, mixing and combustion model. It was confirmed that the model could successively simulate the rate of heat release of a diesel flame in the quiescent chamber of the rapid compression machine.
Technical Paper

A Study on the Influnce of Intel Angel and Reynolds Number on the Flow-Pattern of Uniflow Scavenging Air

A cylinder of a model uniflow scavenging engine filled with air at room temperature was scavenged with hot air, and arrival time of the scavenging air was detected with a thermocouple at 20 positions in the cylinder. And shape of front surface of the scavenging air was obtained from these data: The front surface with medium intensity swirl port has a peak in the central part at low running speed, but as the speed increases, it becomes flat causing scavenging efficiency the highest. And finally, a depression appears at its center at very high running speed. Assuming this phenomenon to be analogous to “vortex breakdown” investigated by T.Sarpkaya and others, the authors have proposed a method to determine a geometry of scavenging port that gives the highest scavenging efficiency at a desired Reynolds number, and verified its availability.
Technical Paper

Prediction of the Rate of Heat Release of an Axisymmetrical Diesel Flame in a Rapid Compression Machine

A phenomenological model for predicting the rate of heat release of an axisymmetrical diesel flame which was achieved in a rapid compression machine has been proposed: Basing on the experimental observations, authors have introduced a new expression about the effects of abrupt thermal expansion due to the initial combustion on the air entrainment. A simple probability density function was also employed to express the distribution of the local equivalence ratio in the flame. The predicted rate of heat release showed good agreement with the experimental results in the diffusion combustion phase.
Technical Paper

Photographic And Image Analysis Studies Of Diesel Spray And Flame With A Rapid Compression Machine And A D. I. Diesel Engine (Interpretation And Conceptual Image)

Some conceptual image of a diesel spray flame and its combustion promotion is shown based on the various interpretations of the enormous data obtained in our laboratory in these several years, on the flame temperature measurement by the two color method, the composition analysis by gas sampling, as well as the focus shadow photography, back illuminated photography and luminous photography by a high speed camera, on the diesel spray flame created in a large scale Rapid Compression Machine (diameter ϕ 200 mm thickness 40 mm) and a D-I engine (diameter (ϕ 95 mm)
Technical Paper

Measurement of Flame Temperature Distribution in a D.I. Diesel Engine by Means of Image Analysis of Nega-Color Photographs

A new technique was proposed for measuring instantaneous distributions of flame temperature and KL factor of luminous flames. Here the principle of the two-color method was used to calculate flame temperature and KL factor from the two-color densities of a film image taken on a nega-color film. We applied this technique to the high speed nega-color photographs of flames in a D. I. diesel engine operated with varying swirl ratios, and discussed the measured results of instantaneous distributions of flame temperature and KL factors.
Technical Paper

Development of a Rapid Compression-Expansion Machine to Simulate Combustion in Diesel Engines

A rapid compression-expansion machine which can simulate the combustion processes in diesel engines is developed. The configuration of the combustion chamber is a 100 mm bore and a 90 mm stroke, and the compression ratio is 15. The piston is driven by an electro-hydraulic system with a thrust of 90 kN and the maximum frequency of 20 Hz. The whole system composed of a hydraulic actuator, a fuel injection system, and a valve driving unit is sequentially controlled by a computer. The reproducibility of the stop position of the piston at the end of compression is achieved with an accuracy of ±0.1 mm by employing a hydraulic-mechanical brake mechanism. The experiment shows that the combustion in the expansion stroke is achieved, and that the combustion characteristics such as the rate of heat release and indicated output as well as the exhaust emission can be measured.
Technical Paper

Stratification of Swirl Intensity in the Axial Direction for Control of Turbulence Generation During the Compression Stroke

Control of turbulence during the compression stroke is suggested by both theoretical calculations and experimental results obtained with an LDV measurement in a motored engine. The authors have found experimentally that when an axial distribution of swirl intensity exists, a large-scale annular vortex is formed inside the cylinder during the compression stroke and this vortex generates and transports turbulence energy. A numerical calculation is adopted to elucidate this phenomenon. Then, an axial stratification of swirl intensity is found to generate a large-scale annular vortex during the compression stroke by an interaction between the piston motion and the axial pressure gradient. The initial swirl profile is parametrically varied to assess its effect on the turbulence parameters. Among calculated results, turbulence energy is enhanced strongest when the swirl intensity is highest at the piston top surface and lowest at the bottom surface of the cylinder head.
Technical Paper

Numerical Simulation of Turbulent Mixing in a Transient Jet

To understand further the mixing process between the injected fuel and air in the combustion chamber of a diesel engine, the turbulent mixing process in a one-phase, two-dimensional transient jet was theoretically studied using the discrete vortex simulation. First, the simulation model was evaluated by comparisons between calculated and experimental data on two-dimensional turbulent jets. Second, the trajectories of the injected fluid elements marked with different colors were graphically demonstrated. Also the process of entrainment of the surrounding fluid into the jet was visually presented using colored tracers.