Published papers

日本では，LPGを燃料とする大型車両（バスやトラックなど）の実用化は不可能とされている．しかし，世界中で見てみると，LPG大型エンジンによる車両，特にバスに使用される例があることを知り，日本での導入可能性を探ることにした．その結果，世界各地でLPG大型バスの存在を確認した．今回は，そのうち，韓国の大型LPGバスを日本に導入することの可能性を調査してきた経過を踏まえ，世界のLPGバスの普及状況について報告する．

In this study, the exhaust gas composition was clarified by using a gas chromatography, and combustion completion was considered in 2-stroke HCCI engine. In exhaust gas composition, n-Butane was high concentration as opposed to calculation results and intermediate products (CO, C2H4, C3H6, CH4, C2H6) also exhausted. Increasing maximum in-cylinder gas temperature until 1600K, combustion efficiency became higher and HC emissions became lower, but over 1600K, combustion efficiency kept constant 82±3% and HC emissions became higher again. In actual engine, it was considered that mixture near cylinder wall couldn’t be ignited because of heat loss to wall. This region was almost 0.83-1.01mm from wall by calculated from exhaust gas composition and concentration by 2 models. And the ratio of exhaust n-butane from heat loss to wall in exhaust n-butane is about 79%, from crevice is about 1%, from leak is about 20%.

In HCCI engine, inhomogeneity of fuel distribution and temperature in pre-mixture has possibilities to affect ignition and combustion. An experimental study has been carried out to investigate the influence of inhomogeneity of fuel distribution on auto-ignition and combustion by using 4 stroke optical access engine. DME was used as the test fuel. Pressure profiles and two-dimensional luminescence image from chemical species have been measured and analyzed. Changing the fuel injection point and fuel injection duration in the intake chamber, inhomogenity was changed. Combustion duration in inhomogeneous condition was longer than homogeneous condition. Fluctuation of maximum pressure of cycles in inhomogeneous condition was larger than homogeneous condition. Luminescence started and stopped uniformly whole the combustion chamber in homogeneous condition, but in inhomogenous condition, luminance had variety in space and time.

In the HCCI (Homogeneous Charge Compression Ignition) engine, a mixture of fuel and air is supplied to the cylinder and auto-ignition occurs resulting from compression. This method can expand the lean flammability limit, realizing smokeless combustion and also having the potential for realizing low NOx and high efficiency. The optimal ignition timing is necessary in order to keep high thermal efficiency. The Ignition in the HCCI engine largely depends on the chemical reaction between the fuel and the oxidizer. Physical methods in conventional engines cannot control it, so a chemical method is demanded. Combustion duration is maintained properly to avoid knocking. In addition, the amount of HC and CO emissions must be reduced. The objective of this study is to clarify the following through calculations with detailed chemical reactions and through experiment with the 2-stroke HCCI engine: the chemical reaction mechanism, and HC and CO emission mechanisms. Ignition and combustion mechanisms and the effect of pre-mixture heterogeneity on ignition and combustion are also clarified. This is done by using an optically accessible engine and measuring the luminescence at auto-ignition and during the combustion process.

ディーゼル機関から排出される微粒子の性状を採取後直ちに超低温で凍結するという手法を開発し，微粒子の補集状況および性状への影響を体系的に調べた。走査顕微鏡でその物理的性状を観察し，また質量分析により化学的特性を調べた。これ等の結果，機関からの微粒子の補集においては，液状排出物質が大きい影響を与えるため，補集までの温度履歴，補集面上温度，排気の希釈濃度の管理が大切であることがわかった。

Reduction of particulate emissions from diesel engine is an important theme from the viewpoint of air pollution. Experiments were carried out using a four-stroke single cylinder direct-injection diesel engine. A new method to measure diesel particulates has been developed. Particulates were sampled with a freezing method just behind an exhaust valve and examined through a scanning electron microscope. Shape and structure of particulates and the size distributions were measured under wide operating conditions obtained with above method. The total mass of particulate emissions was measured using a dilution tunnel sampling system. The heat release processes were analyzed using indicator diagrams and the relation between burning condition and particulate emissions were discussed, after systematic experiments under constant revolution speed of 2000 r/min for several load and injection timing conditions.

流路内を高速で進む火炎の挙動を考察するためにシュリーレン写真による火炎の観察と流路に沿って時間を追ったイオン電流および光学的手法による温度の測定を行なった。その結果，前報で報告した流路内における火炎の不通過あるいは一時的な停滞現象は，流路入口部における未燃焼ガスとの乱流混合および壁への熱伝達による火炎の冷却と，流路内における熱発生との相対的な大小関係により説明されることを見出した。

火炎が外部へ噴出する以前の，流動を伴う狭い流路内での火炎伝播の特性を明らかにすることを目的として，火炎伝播経路に狭い流路を設置した装置を使用して実験を行った。その結果，流路に進入した火炎は，ａ.通過，ｂ.停滞後通過，ｃ.不通過，の３つの挙動を示すことを明らかにした。また，ｂ.について流路内火炎伝ぱ特性と，当量比・流路幅・流路内ガス流速・流路入口形状などがおよぼす影響を明らかにした。

急速圧縮機内に実現した高温・高圧の雰囲気で噴霧燃焼を行ない，雰囲気のガス組成，温度，圧力が噴霧の燃焼過程および微粒子の生成・消滅過程に及ぼす影響を実験的に検討した調べた。

直接噴射式ディーゼル機関を対象に，吸気中の酸素濃度，ＥＧＲガスの濃度などいわゆる給気のガス組成が燃焼と微粒子排出の特性に及ぼす影響を実験的に明らかにした。指圧線図の３領域モデルによる熱力学的解析により，熱発生率と火炎温度履歴を求め，これらと酸素および二酸化炭素富化時の排気特性との関連について報告した。

ディーゼル噴霧周囲気体の流動速度に関する報告につづき，流動方向の時間経過及び流入時間，定常流入速度到達時間等の特性値を定義し，噴霧軸方向と半径方向へ詳細分布を表わした。