研究発表

HCCI機関は高負荷時には筒内の急峻な圧力上昇によってノッキングが生じ，運転領域が制限されてしまう事が課題となっている．圧力上昇を緩慢にしてノッキングを回避する手法としては，燃焼室内局所ごとの着火時期を離散化させる方法が挙げられる．そこで本研究は可視化エンジンを用いて燃焼室内の活性化学種の化学発光を観測することにより予混合気中の燃料濃度の不均質性がHCCI燃焼の圧力上昇率に及ぼす影響を実験的に調査した．実験には光電子増倍管とハイスピードカメラによる計測により発光強度，発光期間の分布を調査した．またHCCI燃焼のロバスト性との関係も考察する．

HCCI燃焼時の圧力上昇率を低減する手法として膨張行程の初期に燃焼を実現する手法に着目し，詳細な素反応を考慮した数値計算および寄与度行列により回転速度がHCCI燃焼特性に与える影響を調査した．膨張行程の同位相においてCA50に到達するよう初期条件を設定した場合，回転速度が上昇しても熱発生における主要な反応経路は変化せず，各素反応が活発になる温度域が上昇し，各素反応の反応速度は上昇する．

HCCI燃焼時の圧力上昇率を低減する手法としてEGRガスの層状給気に着目し，DMEを燃料として，残留ガスや流動の影響を排除でき，ガス組成の把握が可能な急速圧縮装置を用いた燃焼実験，およびマルチゾーンの素反応数値計算により調査した．EGRガスの層状給気を行った場合，燃焼室内局所の比熱比の違いおよびLTHR時の温度上昇量の違いから，HTHR開始時期にばらつきが生まれ，初期のEGR率差の拡大につれて，圧力上昇率が低減する．

--continued-- And concerning to both vehicles, simultaneously vehicle position by GPS, vehicle dynamics, engine dynamics, driver’s operation and road environment were measured. Adopting for transient mode regulation, Japanese JE05 mode, average NOx emission rates became lower by 57.4%, average distance based NOx emission became lower by 46%. And frequency of spot of distance based NOx emission was also lower. But concerning to Vehicle adopted for New Long Term Regulation, Hot-spots occupied 0.70% of route, this is high compared to 0.19% of Vehicle adopted for Long Term Regulation, so that 46% reduction of averaged distance based NOx emissions are not directly leads to 46% reduction of area of Hot-spots.

The purpose of the research is to investigate of diesel spray combustion for simultaneously reduce way NOx and PM．The pressure diesel injection were done into intermediates that are generated by very lean DME HCCI combustion using a RCM. The concentration of intermediate could not be directly measured; we estimated it by CHEMKIN calculation. DME HCCI characteristic is surveyed. Validations of the CHEMKIN calculation were confirmed pressure rise of an experiment and pressure rise of a calculation．Using a framing streak camera captured two dimensional spontaneous luminescence images from chemical species at low temperature reaction(LTR) and high temperature reaction (HTR). Also, the combustion events were observed by high-speed direct photography， the ignition and combustion were analyzed the combustion chamber pressure profiles

It is widespread knowledge that deliberately creating fuel inhomogeneities in HCCI combustion brings about a reduction in the maximum PRR. Investigating this phenomenon with an optical accessible engine, fueled with DME and equipped with Photomultiplier and Image Intensifier.

実路を走行する貨物車を対象に、車載型排出ガス計測システムを用いて排出ガスの排出履歴を計測するとともに、エンジンおよび車両の挙動を計測し、沿道汚染に影響を及ぼすパラメータを抽出した。沿道住民に被害をもたらす局所汚染を、必要最小限のパラメータから把握する手段として、排出量を推計するモデルを提示する。

CNG/Diesel dual-fuel engine is using CNG as a main fuel, and injects diesel only a little as a ignition priming. In this study, remodeling a existing diesel engine into dual-fuel engine that can injects diesel with high pressure by CRDi(Common Rail Direct injection), and injecting CNG at intake port for premixing. The results show that CNG/Diesel dual-fuel engine satisfied coordinate torque and power with conventional diesel engine. And CNG alternation rate is over 89% in all operating range of CNG/diesel dual-fuel engine. PM emission is lower 94% than diesel engine, but NOx emission is higher than diesel engine.

ホットスポット発生の機構は，交差点などの道路インフラ，対向車などの道路状況，運転者の運転操作，それに伴うエンジン出力の挙動および車両速度などの車両挙動の複合的な要因からなる．本研究では，車載型排出ガス計測装置を搭載した３トン積貨物自動車を用いた路上走行試験を行い，ホットスポット発生の実態調査および原因の解析を行った．この車両は新長期規制適合車であり，EGR，DPFなどの排出ガス低減装置により，モード試験時の排出ガス量が低減している．その低減効果がホットスポットの発生にも低減効果があるかどうか調べるために，長期規制適合車の路上走行試験結果と比較することで検証した．

Cooled exhaust-gas recirculation (Cooled EGR) is known as the effective way to mitigate knock in HCCI engines, which helps to extend operating range to high-load limits. However, the misfire is caused easily in low-load limits with high CO. Fuel stratification is combined with EGR to compensate those problems. CO2 is used in order to simulate the effects of cooled EGR in numerical analysis. A combination of cooled EGR and fuel stratification shows extended operating ranges to high-load limits. However, high CO is produced in operating point due to the low combustion temperature with significantly low NOx.