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Observations of the scavenging flow field have been made in a modified poppet-valved two-stroke engine with a transparent cylinder. Four kinds of cylinder heads with different port configuration were created to analyze their effects on the scavenging flow and develop new scavenging concepts. A mineral oil fog discharge system was used to visualize the air flow during the scavenging process. All of the images were recorded by a high speed video camera which show the development of the scavenging processes and clearly indicate the scavenging jet structure, the tumble pattern and the location of re-circulation regions. The analyses allow us to judge the quality of the scavenging processes. The small changes in port geometry could significantly affect the scavenging flow. Tumble as well as swirl should be considered as main means to organize the scavenging flow in order to avoid short-circuiting losses and create condition favorable to combustion.

This study presents the possibility of realizing better thermal efficiency in a spark-ignition engine with over-expansion cycle. The test engine with the displacement volume of 649cc was used together with four kinds of expansion ratios (geometric compression ratio) from 10 to 25, and four sets of intake valve closure timings from 0 to 110 ° C.A. ABDC. In previous studies, the indicated thermal efficiency reached 48% However, there was a problem that the maximum output was reduced to almost half compared with the conventional engine, since the effective displacement volume was decreased with decreasing the substantial compression ratio (εc). As a method of solving this problem, supercharging was applied by using compressed air supplied from an external compressor.

Injection rate measurement of an automotive gaseous fuel injector was carried out by use of a one-dimensional pipe flow. A production gaseous fuel injector for an NGV (Natural gas vehicle) was used, which is for an intake port fuel injection. The injection pressure was set at 255 kPa(g), and the injection duration was varied from 3.4 to 20 msec. Nitrogen gas was used as the test gas. The test gas was injected into a pipe from the injector, and the static pressure history was acquired with a piezoelectric pressure transducer. One-dimensional, compressible, inviscid, adiabatic flow was assumed, and the instantaneous mass flow rate inside the pipe was estimated. By integrating the injection rate during the injection duration, the total amount of mass flow per one stroke was calculated. Calibration test was carried out by use of a pressure vessel, from which the total mass flow during one stroke was estimated.

To achieve power output and cooling performance in motorcycle air-cooled engines equivalent to those in water-cooled engines, an engine utilizing air-flow generated by the moving motorcycle and a new oil-cooling system for an air-cooled engine was studied. The engine temperature distribution was obtained based on a CFD (Computational Fluid Dynamics) analysis of cooling-air/oil behavior using an inline four-cylinder 900cm3 engine. As a result of this study, engine temperature was sufficiently decreased and the difference in temperature among cylinders was reduced; the engine was tested in a prototype motorcycle.

Performance of a CNG (Compressed natural gas) two stroke cycle S.I. engine using intermittent low pressure fuel injection from scavenging ports is investigated experimentally. The test engine is a two cylinder, 398 cm3, two stroke cycle spark ignition engine. Gaseous fuel injectors are attached at the engine block, and a CNG is injected into the scavenging passage through a fuel injection pipe. The fuel injection pressure is set at 0.255 MPa, and the fuel is injected intermittently during the scavenging process. The length and tip geometry of the fuel injection pipe are varied, and the effect on the engine performance is investigated. Using the scavenging port fuel injection, the BSFC is reduced by 25 %, and the lean burn limit extends from λ = 1.2 to 1.46, at the maximum. The peak of the NOx emission shifts to leaner side, and the THC emission is reduced by 47 % at the maximum.

An experimental study on a direct-injection gasoline spray initiated from a swirl injector was carried out in order to clarify the effects of ambient temperature and pressure. The sprays were formed in a pressure chamber where the maximum pressure and temperature reached 1.1 MPa and 423 K respectively. The spray-tip penetration for elevated ambient temperature is slightly longer than that for normal ambient temperature. From the measurement using phase Doppler anemometry, it was found that the Sauter mean diameter D32 is large under high ambient pressure condition. The effect of elevating the ambient temperature is to decrease D32 in the core region of the spray.

Recently, rider comfort at highway driving has become an important issue in the performance improvement of motorcycles. Comfort includes windbreak, pressure on the rider, wind noise, visibility, and steering characteristics. However, most of these factors cannot be analyzed conventionally. Therefore we used CFD (Computational Fluid Dynamics) to examine the rider’s airflow environment. The environment of a rider on a motorcycle is an open space, very different from the passenger environment in an automobile. There are many airflow paths in a motorcycle with a cowl and a windscreen; thus, airflow behavior is constituted with a delicate balance. Though wind tunnel tests can give us an outline of airflow, CFD is a useful way to visualize the airflow of the rider’s environment and clarify the details. As the results, a lot of helpful knowledge was obtained for the development of new motorcycles.

The aim of the experiment is to observe the exhaust gas flow starting from the exhaust manifold to the catalytic converter at the 4 stroke engine of the passenger car to enhance the system's improvement. The manifold connects each exhaust pipe from the engine cylinders to the catalytic converter. The velocity pattern inside the exhaust manifold is measured using particle image velocimetry (PIV) meanwhile the time series velocity data is measured by Laser Doppler Anemometer (LDA). In the experiment, flow conditions with four pipes working simultaneously or single pipe working independently are tested. The initial velocity condition shown in the next is set at the upstream where the flow is inside the circular pipe. The initial velocity is 28m/s for the all pipes acting and 14m/s for each pipes acting. There are also 3 conditions of measurement: with catalytic converter, without catalytic converter and with hollow catalytic converter.

The lubrication mechanism is discussed by measuring the oil film behavior. The oil film behavior is evaluated by the oil film thickness and oil film velocity map. The combination method of laser induced fluorescence method (LIF) and particle image velocimetry (PIV) is applied to measure the oil film behavior. The oil film thickness is measured by LIF and its velocity distributions are measured by PIV. The combination method can provide both of the film thickness and velocities simultaneously. The first trial is performed in the model engine for checking the dynamics measurement of the oil film thickness by the LIF. The results show a difference of the oil film thickness distribution with crank angle. The combination method is tested in the engine with 4-cycle and 2-cylinder optical access engine with motoring condition. One cylinder of the engine is sapphire cylinder for observing oil film behavior on the piston skirt. Two clearances of the piston skirt of 30 µm and 100 µm is tested.

Air velocities in the cylinder of motored engine were measured by laser Doppler anemometer (LDA) and particle image velocimetry (PIV) to make the standard database that will be used for verification of the numerical simulation. A 4-stroke, 4-valve test engine with transparent cylinder was operated with engine speed of 600rpm. The velocities on that condition were measured individually in vertical- and swirl-direction. The distributions of mean- and RMS- velocities are obtained from the measured data. Flow velocity through the intake valve was also measured at the top of the cylinder. As the results, the flow structure by each crank angle can be clarified. The present data can be commonly used for some numerical research group of RC238 in JSME for verification of numerical simulation results. The effect of the tumble generation valve (TGV) is evaluated by velocity distributions.

Atomization characteristics of an ultrasonic fuel injector using a micro nozzle array were improved by change of horn geometries. Micro nozzles whose exit diameter d = 3 µm are mounted on a thin metal film, and the number of micro nozzles was varied from 2.0 × 104 to 1.2 × 105. Gasoline is periodically pushed out from the micro nozzles at frequencies from 62 to 65 kHz. A disk type PZT (Lead zirconium titanate) is used as an ultrasonic oscillator, and the oscillation is amplified by an axi-symmetric step-type horn. The oscillation amplitude is proportional to the area ratio of the horn. The number of micro nozzles increases with the increase in the small end diameter of the horn, while the oscillation amplitude decreases at the same time. In order to increase the fuel flow rate, the horn small end diameter Ds was varied from 10.5 to 25 mm, while the large end diameter is fixed at 30 mm.

A high-pressure swirl type fuel spray has been experimentally analyzed by using a phase Doppler anemometer (PDA). The experiments were mainly made under the injection pressure of 5MPa and injection frequency of about 46Hz. The PDA data was obtained in a two-dimensional plane and arranged by the ensemble-averaged method along the injection phase angle. The arranged data of mean velocity and Sauter mean diameter were visualized for demonstration. Time-dependent centerline velocity at the injection pipe was also measured by means of laser Doppler anemometer (LDA). Swirl injector operating at injection frequencies of 22 and 46 Hz generates oscillating flow in the pipe under injection pressure from 4 to 7 MPa. The time-series of centerline velocity was used to reconstruct the time-series of instantaneous pressure gradient and flow rate in the pipe.

This paper presents two factors for improving the performance and emissions characteristics in HCCI diesel combustion, one is reducing compression ratio and another is changing the injector position. In a previous study, it was shown that HCCI diesel combustion could be realized by utilizing a hollow-cone spray with normal injection pressure. However there remained two major problems of engine instability and increase in BSFC (decrease in brake thermal efficiency). By reducing the compression ratio from 18.8 to 16.8, the engine stability was much improved to the level of conventional diesel combustion and the increase in BSFC became almost half, which was mainly due to the change of combustion phasing. In addition to this, application of 5 mm inside position of the injector realized almost no penalty of BSFC at higher load condition.

The swirl and axial components of gas velocity in the disk type combustion chamber of a fired and motored spark ignition engine were measured using a fiber-optic laser Doppler Anemometer (LDA). The engine was operated at a speed of 1500 rpm, a volumetric efficiency of ηυ = 0.5, an equivalence ratio ϕ = 1.4 and with an ignition timing of θig = 30°BTDC (MBT condition). The gas velocities at 9 points on a diameter at mid-height of the combustion chamber were processed by the cycle-resolved frequency discrimination method. The bulk (mean) velocity was determined by frequency components lower than a cut-off frequency of 667Hz. The flame propagation pattern was detected by ionization probes set at 17 points on the piston. The results indicate significant differences in flow characteristics between motored and fired conditions during the combustion period.

In CFD (Computational Fluid Dynamics) verification of vehicle aerodynamics, detailed velocity measurements are required. The conventional 2D-PIV (Two Dimensional Particle Image Velocimetry) needs at least twice the number of operations to measure the three components of velocity ( u,v,w ), thus it is difficult to set up precise measurement positions. Furthermore, there are some areas where measurements are rendered impossible due to the relative position of the object and the optical system. That is why the acquisition of detailed velocity data around a vehicle has not yet been attained. In this study, a detailed velocity measurement was conducted using a 3D-PIV measurement system. The measurement target was a quarter scale SAE standard vehicle model. The wind tunnel system which was also designed for a quarter scale car model was utilized. It consisted of a moving belt and a boundary suction system.

There have been many experiments to characterize Diesel fuel spray under steady-state conditions. However, the best number and position of holes on the sac to be used in the experiment are not clear. To address these question, we investigate Diesel type spray flows using a laser Doppler anemometer (LDA) and a phase Doppler anemometer (PDA). Spray flow characteristics, such as mean and fluctuating two component velocities, the two dimensional distribution of particle diameter and the three parameter variation at the log-hyperbolic fitting according to particle size distribution, are given from measured data. Spray jets from four varieties of Diesel nozzle are compared with each other to identify the differences in spray characteristics between them. The results show that the spray from the original single-hole nozzle on the top of the sac is distinct from the other types of nozzle.

To study the characteristics of flow velocity and particle diameters in large angle conical spray proposed for hot-premixed combustion type Diesel engines, steady and unsteady conical sprays have been analyzed using laser Doppler anemometry (LDA), and phase Doppler anemometry (PDA). Three injection pressures were used in steady experiments. In unsteady experiments, the frequency of injection was 20.7 Hz and the amount of injection fuel was 10.3 mg or 25.6 mg in each cycle. Distributions of bulk velocity, fluctuation intensity of the velocity, air entrainment rate, Sauter mean diameter of particles and correlation between particle diameter and velocity of the spray were obtained.

A modified drop drag (MOD) model based on the droplet deformation and breakup (DDB) model has been developed and implemented in the KIVA II code for describing fuel spray impingement against the walls of the combustion chamber in D.I. diesel engines. The model accounts for the effects of both the drop's frontal area and its drag coefficient as a function of its distortion. In the MDD model, the stochastic rotation of drops that have impacted and bounced off the wall is considered. This makes it possible to model the highly distorted drop's frontal area variation and its effect on the drag coefficient in sprays. At the same time, the distribution of sizes of drops formed from parent drops after their breakups is modeled by using a stochastic model. A modified RNG κ - ε model is also included in the present computations. The details of fuel spray impingement against a wall were investigated by using the present models.

Characteristics of premixed charge compression ignition (PCCI) Diesel combustion were investigated experimentally. In a PCCI engine, the operatable range is limited by the cyclic variation at low loads and the intensive knock at high loads. In the present study, effects of compression ratio on the characteristics of the PCCI combustion are investigated experimentally. The compression ratio was varied from 18.8 to 14.8. For the early injection timing, the high load operation limit is extended from BMEP = 0.22 MPa to 0.40 MPa. At the same time, the minimum BSFC for the early injection timing decreases from 330 g/kWh to 230 g/kWh.

High-pressure fuel spray proposed for direct injection gasoline engine was evaluated by means of a phase Doppler anemometer (PDA) and flow visualization. The intermittent fuel spray from a swirl type injector was injected in a constant volume chamber under various conditions of backpressure and ambient temperature. The backpressures were set to 0, 0.5 and 1 MPa in gauge pressure. The ambient temperatures were set to 293, 373, 423 and 473K. Normal-heptane was used as a fuel with injection pressure of 10MPa and injection frequency of 10Hz. Spray characteristics of the temporal and spatial distributions of the mean velocity and the mean diameter were measured by the PDA. Visualizations of spray were also made by a particle image velocimetry (PIV). The experimental results show the effects of backpressure and ambient temperature on the spray shape and characteristics of droplet size and velocity distributions.