Michihiko Tabata

Ion current measurement in a homogeneous charge compression ignition engine

Abstract An ion current probe using a spark plug was applied to gasoline-fuelled homogeneous charge compression ignition (HCCI) combustion with hot residual gas in order to verify the possibility of using it as a combustion sensor. The ion current signal for single-cycle HCCI combustion had a simple profile and effectively one maximum value. There is a possibility that a similar ion current signal corresponding to the completed reaction can be obtained, depending on the location of the probe during HCCI combustion. The ionization reaction for HCCI combustion is affected by the chemical ionization reaction with heat release, and there is a possibility that the ion current can be used to detect heat release corresponding to the chemical ionization reaction. A strong correlation between the timing of the integrated ion current and the timing of the mass fraction burned is observed. The timing of the mass fraction burned is assumed from the timing of the integrated ion current, and the mass fraction burned (up to 70 per cent) can be determined, even if the engine driving condition changes within the scope of the test. There is a correlation between the timing of the maximum ion-current and the maximum rate of heat release, and there is a possibility that the maximum value of the rate of heat release can be inferred by detecting the timing of the maximum ion current. There is a correlation between the timing of the maximum ion current and the timing of the maximum pressure at each cycle. Therefore, it may be possible to monitor the variation of the HCCI combustion phasing.

Effect of combustion chamber shape on tumble flow, squish-generated flow and burn rate

Abstract Effects of squish area location on tumble and squish flow were investigated to control the knock in an SI engine. For the exhaust squish piston, tumble flow is collapsed by the exhaust squish clearance during the compression stroke, so that the compression-squish flow is strong. For the intake squish piston, tumble flow impinges on the edge of squish area and the induction of it into the squish area is controlled. The compression-squish flow is weakened and reverse-squish flow grows strong. This led to realization of a high heat release at late stage combustion. Simultaneously, the decrease of cycle-by-cycle variation of initial burn is realized. Consequently, knocking is controlled compared with a flat piston.

Atomization of high viscosity liquid by a diesel nozzle.

ディーゼル機関での燃料の粗悪化,高粘度化に対処するため,噴射燃料の基礎となる噴射に及ぼす粘度の影響について,レーザ回折による粒径測定および噴射角の測定を行った。ふん囲気圧力,噴射力,液体の粘度を変化させて,その影響を調べ,粘度に及ぼす微粒化の限界を示した。高圧噴射を行うと粘度が高いほど平均粒径は増加するが,噴霧角はその影響を受けないことなどがわかった。