Hidenori Tasaka

ANALYSIS OF GAS EXCHANGE PROCESS OF S.I. ENGINES UNDER CITY-DRIVING CONDITIONS

A precise and simplified prediction method of volumetric efficiency and burned gas fraction in the cylinder charge, which are closely related to the power output, emissions, and fuel economy, has been required for the most frequent conditions of city-driving. A fixed volume plenum model for the intake and exhaust manifold was used as an analytical model of the gas exchange process, because of the very small effects of pulsation under these conditions. The application limit and the close examination of this model were investigated by experiments and calculations on the volumetric efficiency and burned gas fractions in the cylinder charge. Furthermore the IMEP, ISNO, ISFC were predicted for the changes in the valve timings. As a result, it was clarified that a wide range of operating conditions would fall within limits of this prediction model, and this model was valid in predicting the gas exchange process under city-driving conditions.

Extraction Method and Evaluation of Shape for Flame Cross Section of Premixed Turbulent Combustion in Constant Volume Combustion Chamber by Image Measurement

To clarify the mechanism of turbulent combustion from a view point of physical data, premixed turbulent combustion in a constant volume combustion chamber was researched. Flame shape was measured as cross sectional image by laser sheet method. The most suitable method for extraction of flame front was examined and flame shape was evaluated as complexity of flame outline by fractal dimension. The results showed that the image processing method using frequency filter was suitable for extraction of correct flame front. Fractal dimension of flame shape was increased by turbulence intensity. Furthermore it was kept constant value at each turbulence intensity during growth of flame.

Capability of In-Cylinder Flow Measurements by Backward Scattered LDV Using Low Power Laser.

Many pepers have been published on the measurements of in-cylinder flow of an engine, because flow velocity affects to heat transfer to the cylinder walls, and the turbulence intensity also affects the combustibility of the fuel air mixture. Backward scattered LDV is considered to be suitable for measuring the in-cylinder flow on account of its flexibility in application to the engine. However, the demerit of this method is the weak scattered light from the scattering particles. Hence a high powered laser and normal optics are needed and the system is to be so complexed. One of the revisions for the backward scatterd LDV is to use optical fiber to simplify the optics, but this method has demerits of slight scattered light and poor spatial resolution. If it is possible to measure using backward scattered LDV of a low power laser, the measuring system can be more simplified and useful. Therefore, in this paper, the capability of using a low power laser for LDV is studied with revised optics, a signal processor, and scattering particles, and finally the system is applied to an engine and reasonable velocity was measured. Thus the capability of backward scattered LDV using a low power laser is confirmed.

簡易モデルによるシリンダ内スワールの予測計算 : 第4報,弁時期の評価

Improving combustion of the spark ignition engines contributes largely to decreasing fuel consumption, especially under the conditions of medium or low speed and low load. In this paper, valve timing is evaluated from the viewpoints of swirl velocity as well as the volumetric efficiency, burned gas fraction in a fresh mixture charge, and pumping loss at intake stroke by using the predictions of the simplified simulation model. As a result, the timing of intake valve opening and closing is considerably affected by the swirl velocity. It is also confirmed that the mean swirl velocity controlled by the valve timing is higher than that controlled by the conventional throttling system under the same volumetric efficiency condition.

Flow visualization measurement of in-cylinder flow by high speed photographs using an electro-optical shutter.

The flow visualization technique was used to measure the in-cylinder flow of an internal combustion engine. In this paper, metaldehyde was used as a tracer of the gas flow and the PLZT was adopted as the shutter on the basis of its merit of electrical controllability. First, the flow velocity obtained by this measuring system and that from LDV were compared and found to be in agreement ; this demonstrated the validity of the measuring system. Two examples of the measured velocity were also shown. One is that cyclic variation of the in-cylinder flow and differences in the velocity on each radius at one moment existed. The other is that the rotational centers of the flow traces were calculated and found to distribute around the cylinder center at the compression stroke, gather near the cylinder center at the compression end, and distribute widely around the cylinder center at the expansion stroke.

PREDICTIONS OF COMBUSTION, FUEL ECONOMY, AND EMISSION CHARACTERISTICS INFLUENCED BY THE GAS EXCHANGE PROCESS OF S.I. ENGINES

The conflicting problems of fuel economy and NOx emissions in a spark ignition engines are discussed in relationship to the residual gas, volumetric efficiency and pumping loss as predicted by gas exchange analysis. Applications of the gas exchange calculations indicate the importance of the simulation model in evaluating combustibility, fuel economy, and emission characteristics.