Tetsuya Ohira

Exhaust Gas Flow Behavior in a Two-Stroke Engine

The velocity variations in an exhaust pipe of small two-stroke engines have been measured using the FLDV technique. The relationship between the velocity variation and the pressure wave propagation of the burnt gas was investigated. The measured results show that large velocity gradient and spiky velocity peaks were formed due to the burnt gas pressure propagation after EO, and the velocity peak positions could be estimated from the exhaust pipe pressure. The flow profiles indicate pulsative pipe flow. The measured data could be used to understand fresh air short circuit.

COMBUSTION ANALYSIS AND ITS OPTIMIZATION IN TWO-STROKE ENGINES

The purpose of this study is to show cycle-to-cycle combustion variation in transient conditions of quick throttle opening and to control the combustion fluctuation and improve acceleration in a two-stroke motorcycle engine. Two phases of engine operation were focused on: the low-load condition before quick throttle opening, and the transient condition after quick throttle opening. The time-series variation of the heat release rate based on the in-cylinder pressure, the engine-speed and the exhaust pressure variation were measured simultaneously, in an engine with a new multiple-timing-ignition-system, and in an engine with a modified exhaust port. Stable ignition performance and fast burning velocity were the keys to attaining smooth acceleration.

Cyclic Variation of CO and C02 Emission in a Small Two Stroke Engine.

Cyclic variations of CO and CO2 emission were investigated in relation to in-cylinder pressure in a small two-stroke engine. High-speed exhaust gas sampling of 200 Hz was carried out at the exhaust port. The results obtained show that the time resolution of gas sampling was insufficient to account for the cycle-resolved fluctuations observed, but was sufficient to show cyclic variation of emissions. The concentrations of CO and CO2 were measured with regard to the in-cylinder pressure and IMEP. The misfiring effect was examined from the time variations of CO and CO2 concentrations. The cyclic variation of the ratio of CO to CO2 and IMEP showed the same periodic pattern under light load condition.

A study on intake flow characteristics in a two-cycle engine by a fiber laser Doppler Velocimeter.

This paper describes measurement and analysis of intake flow characteristics in a two-cycle engine which have an important effect on engine performance. For a two-cycle engine, there is close correlation between gas flow velocity and pressure. Therefore, it is necessary to elucidate these relations. The gas flows in the intake pipe were measured with a fiber laser Doppler velocimeter (FLDV) which has excellent optical properties. Furthermore, we measured the intake pipe pressure, the exhaust pipe pressure and the scavenging port pressure as well as the intake flow velocity using a developed simultaneous measurement system to clarify their mutual relations. From these measurements, the relations between gas flow velocity and pressure became obvious. In addition, the flow characteristics in the intake pipe were investigated by measuring the velocity at several measurement positions for various operating conditions.