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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.

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.

A simplified turbulence model for predicating the in-cylinder turbulence parameters during combustion in a spark-ignition engine is investigated in this study. It is based on the standard k - ε model with the assumptions that no influence of squish and swirl is considered and that turbulence is in equilibrium. Hence it has a simplified form that meets the requirements for a two-zone quasi-dimensional combustion model. The proposed sub-model is implemented in a quasi-dimensional entrainment combustion model for spark-ignition engines. With this combustion model as the core system, a complete thermodynamics simulation system for a turbo-charged spark-ignition engine is programmed to simulate the working process and engine performance characteristics.

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.

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.

This paper describes the evaluation of flow characteristics inside a model engine cylinder using particle image velocimetry (PIV), laser Doppler anemometry (LDA), and numerical simulation by Partial Cells in Cartesian coordinate (PCC) method. The main goal of the study is to clarify the differences in the velocity characteristics obtained by these methods. The model engine head has a four-valve system. Single- and dual- valve opening conditions of the model engine head were tested by a steady flow test rig. The flow structures were completely different for these valve opening conditions. The mean velocities and their distributions obtained by the three methods show satisfactory agreement. However, there were differences in the turbulence intensities under several conditions and measuring positions. Taylor's hypothesis in the integral length scale of turbulence was also compared with single LDA and PIV measurements.

This paper presents the effect of application of scavenging-port injection to a two-stroke two-cylinder boat engine fueled with a compressed natural gas (CNG). Experiments were carried out at a constant speed of 3000 rpm and WOT condition with varying excess air ratio in lean region. A CNG injector for a production automobile engine was utilized and installed into the scavenging ports. Comparison was made with homogeneous charge operation using a gas mixer. By applying the scavenging-port injection, unburned-fuel in the exhaust gas was reduced close to half which must be due to the reduction of fuel short-cutting during the gas exchange process. The lean-burn limit was extended from the excess air ratio of 1.21 to 1.57. The maximum decrease of BSFC reached to 25 %. This suggests that stratified-combustion could be realized in its lean-burn region.

This paper presents basic combustion behavior of a compressed natural gas directly injected into a cylinder with spark-ignition. Experiments were conducted in a rapid-compression machine (RCM) with the cylinder bore of 80 mm, the stroke of 180 mm and the compression ratio of 10 at TDC. A CNG was injected through specially designed injectors which were installed at the side of combustion chamber with three modes, twin injectors in parallel, twin injectors in opposed and single injector. Combustion products were also measured with an infra-red gas analyzer. Direct photographs were taken with a high-speed video for observation. Effect of fuel injection timing was examined at constant spark timing together with the influence of injection mode. Results show several beneficial combustion characteristics of direct injection combustion using CNG. Combining with the results of combustion products and photographic observation, the combustion mechanism is discussed.

Characteristics of compressed natural gas (CNG) direct injection auto-ignition were investigated experimentally. A rapid compression machine (RCM) with the compression ratio of 10 was used. The diameter and thickness of the combustion chamber are 80 mm and 20 mm, respectively. After the compression start, fuel was directly injected with a single hole injector at the injection pressure of 7.0 MPa, and auto-ignition takes place. The fuel injection timing was varied from 50 ms to 60 ms from the compression start. Two kinds of natural gasses were tested; 12A (CH4: 99.1 %) and 13A (CH4: 86.3 %, C2H6: 5.2 %, C3H8: 1.9 % and others). A glow plug was installed in the cylinder in order to assist the ignition, which was set at 30 mm downstream from the fuel injector nozzle exit. Two kinds of auto-ignition processes were observed. For CNG 12A, auto-ignition always takes place after the end of the fuel injection. The ignition delay is relatively long (40 to 80 ms) and the fluctuation is large.

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.

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.

To model sprays from pintle type nozzles with large hollow cone angle and high injection pressure, the correct flow field in the near region must be predicted. A new model was implemented in KIVA-3V code, which adopts the theory of steady gas jet to correct the relative velocities between the drop and gas phases, based on the existence of quasi-steady part of the conical spray and an assumption of equivalent gas jet. Accordingly, the structure of the sprays is defined into three parts: 1. initial part that the gas phase velocity is set to the assumed gas injection velocity; 2. quasi-steady part where the component of velocity in the symmetric line direction of the spray is corrected; 3. stagnation part which is left unchanged. This new model is referred to as the Relative Velocity Correction (RVC) model, and is a set of empirical equations that calculate the sectional distribution of the gas-phase velocity along the symmetric line of the sprays.

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.

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.

The most serious problem in a 2-stroke spark-ignition engine is poor trapping of fresh charge. To solve this problem, a scavenging-port injection was applied, and a fuel injection pipe (FIP) was installed at the injector tip. In a previous study, it was shown that the BSFC and emission characteristics were drastically improved. In the present study, effect of increase in the fuel injection rate was investigated. It is shown that the BSFC and the THC emissions improved at high engine speeds, while they slightly deteriorate at low engine speeds. The increase in the fuel injection rate is effective particularly at high engine speeds, where the scavenging duration becomes shorter.

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.

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.

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.

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.

A laser Doppler velocimeter is used to measure in real time the velocities of pipe flows in a crankcase-scavenged small two-cycle engine with piston and reed valves. Consequently the optical windows in each pipe must be exchanged instantly by using rotary window systems. The flows in both the inlet and exhaust pipes show different patterns in the motored and firing conditions, but the flows in the scavenging pipe are in a similar pattern regardless of the operating conditions.