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A Potentiality of Dedicated EGR System for Improving Thermal Efficiency in Natural Gas SI Engines

Sejun Lee, Kyohei Ozaki, Takahiro Sako, Norimasa Iida

International Journal of Automotive Engineering （JSAE） 6 （ 1 ） 15 - 22 2015年03月

研究論文（国際会議プロシーディングス）, 共著, 査読有り, ISSN 2185-0984

Object of this study is to realize improving thermal efficiency and emission reduction with low temperature combustion. EGR is a solution to low temperature combustion, however it occurs burning velocity decrease. To prevent this phenomenon, Dedicated EGR was adjusted to SI engine run by natural gas. The entire exhaust gas of a single cylinder operated by the equivalence ratio varied from lean to rich was recirculated to the other cylinders. Due to H2 and CO included in EGR, slowed burning velocity problem was overcome with increasing degree of constant volume, thus thermal efficiency could be improved.

A study on the spray and engine combustion characteristics of diesel–dimethyl ether fuel blends

Ock Taeck Lim and Norimasa Iida

Proc IMechE Part D: J Automobile Engineering （IMechE） 229 （ 6 ） 782 - 792 2015年03月

査読有り

The purpose of this study was to compare the spray characteristics, the combustion characteristics and the emissions (nitrogen oxides, carbon monoxide, hydrocarbon and smoke) of typical fuels (100% diesel and 100% dimethyl ether) and diesel–dimethyl ether fuel blends in a constant-volume chamber and a single-cylinder direct-injection diesel engine. The spray characteristics were investigated by varying the ambient pressure and the fuel injection pressure using a commonrail fuel injection system with various fuel mixture ratios. The spray characteristic research parameters were the spray shape, the penetration length and the spray angle at the seven-hole injector. Common types of injector were used (Bosch). Two types of fuel blended by mass fraction were employed. Typical fuels (100% diesel and 100% dimethyl ether) and fuel blends with diesel:dimethyl ether mixture ratios of 95:5 and 90:10 were used. The injection pressure was fixed at 70 MPa while the ambient pressure was varied (0 MPa, 2.5 MPa and 5 MPa). The combustion experiments were conducted in a single-cylinder engine equipped with a common rail. The injection pressure was 700 bar at 1200 r/min. The amount of injected fuel was adjusted to obtain a fixed input calorific value of 972.2 J/cycle in order to make a comparison
between the fuel types. The results showed that the injection quantity was greater with diesel fuel but not for dimethyl ether fuel and for the fuel blend with the higher mixing ratio. The spray penetration length increased with increasing ambient pressure for diesel but decreased for dimethyl ether with a larger spray angle. The ignition delay and the heat release rate decreased with increasing dimethyl ether which led to a higher indicated mean effective pressure and higher thermal efficiency because there was less negative work in the expansion. The total hydrocarbon emissions and the carbon monoxide emissions decreased with increasing dimethyl ether, but the nitrogen oxide emissions generated were greater owing to the increased combustion temperature.

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Closed-loop control of HCCI combustion for DME using external EGR and rebreathed EGR to reduce pressure-rise rate with combustion-phasing retard

Dongwon Jung, Norimasa Iida

Applied Energy （Elsevier Inc.） 138 （ issue C ） 315 - 330 2015年02月

研究論文（学術雑誌）, 査読有り, ISSN 0306-2619

This study experimentally investigates the effects of the combustion phasing on the homogeneous charge compression ignition (HCCI) combustion, and implements a closed-loop control of HCCI combustion to reduce pressure-rise rate (PRR) with combustion-phasing retard. The experiments were conducted using dimethyl ether (DME) in a single-cylinder HCCI research engine equipped with an exhaust gas recirculation (EGR) loop for external EGR and a two-stage exhaust cam for rebreathed EGR. The results show that a maximum PRR (PRRmax) and a maximum in-cylinder charge temperature decreases with combustionphasing retard. However, excessive combustion-phasing retard leads to unacceptable coefficient of variation (COV) of CA50 and IMEP with partial-burn and/or misfire cycles. To dampen increasing cycleto-
cycle variations around the limit of combustion-phasing retard, the closed-loop control of HCCI
combustion was implemented using three feedback variables. Finally, stable stoichiometric HCCI
operation could be achieved with extensive combustion-phasing retard while maintaining acceptable PRRmax with the higher level of IMEP.

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The effects of key parameters on the transition from SI combustion to HCCI combustion in a two-stroke free piston linear engine

Nguyen Ba Hung, Ocktaeck Lim, Norimasa Iida

Applied Energy （Elsevier Ltd.） 137 （ issue C ） 385 - 401 2015年01月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 0306-2619

An investigation was conducted to examine the effects of key parameters such as intake temperature, equivalence ratio, engine load, intake pressure, spark timing and spring stiffness on the transition from SI combustion to HCCI combustion in a two-stroke free piston linear engine. Operation of the free piston engine was simulated based on the combination of three mathematical models including a dynamic model, a linear alternator model and a thermodynamic model. These mathematical models were combined and solved by a program written in Fortran. To validate the mathematical models, the simulation results were compared with experimental data in the SI mode. For the transition from SI combustion to HCCI combustion, the simulation results show that if the equivalence ratio is decreased, the intake temperature and engine load should be increased to get a successful SI-HCCI transition. However, the simulation results also show that the in-cylinder pressure is decreased, while the peak in-cylinder temperature in HCCI mode is increased significantly if the intake temperature is increased so much.
Beside the successful SI-HCCI transition, the increase of intake pressure from Pin = 1.1 bar to Pin = 1.6 bar is one of solutions to reduce peak in-cylinder temperature in HCCI mode. However, the simulation results also indicate that if the intake pressure is increased so much (Pin = 1.6 bar), the engine knocking problem is occurred. Adjusting spring stiffness from k = 2.9 N/mm to k = 14.7 N/mm is also considered one of useful solutions for reducing the peak in-cylinder temperature in HCCI mode as well as avoiding engine knock. Besides, the change of spark timing is suggested as a benefic method to help the control of the SI-HCCI transition to be more convenient. To get a successful SI-HCCI transition with reducing of peak temperature in HCCI mode as well as avoiding engine knock, the simulation results show that the engine should be operated with following conditions: equivalence ratio / = 0.7, engine load RL = 180 X, intake temperature Tin = 400 K, intake pressure Pin = 1.2 bar, spark timing in SI mode xig = 3 mm and spring stiffness k = 14.7 N/mm.

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A Potentiality of Dedicated EGR in SI Engines Fueled by Natural Gas for Improving Thermal Efficiency and Reducing NOx Emission

Sejun Lee, Kyohei Ozaki, Norimasa Iida, Takakiro Sako

SAE Int. J. Engines （SAE International） SAE 2014-32-0108 /JSAE 2014901 （ 8(1) ） 230 - 237 2014年11月

研究論文（国際会議プロシーディングス）, 共著, 査読有り, ISSN 1946-3936

Recently, a potentiality of Dedicated EGR (D-EGR) concept SI engine has been studied. This concept engine had four
cylinders and operated with exhaust gas supplied from the single cylinder to the intake manifold. Compared with
conventional SI engines, it was able to increase thermal efficiency and decrease CO, HC, and NOx emission by the high
D-EGR ratio 0.25.
In this study, numerical analysis of a SI engine with D-EGR system with various D-EGR ratios was conducted for detailed
understanding the potentiality of this concept in terms of thermal efficiency and NOx emission. #1 cylinder of assumed
engine was used as D-EGR cylinder that equivalence ratio varied from 0.6 to 3.4. Entire exhaust gas from #1 cylinder was recirculated to the other cylinders. The other cylinders run with this exhaust gas and new premixed air and fuel with
various equivalence ratios from 0.6-1.0. To study the effect of D-EGR ratio, the number of engine cylinders was considered from 3 to 6, same meaning with D-EGR ratio 0.5-0.2. A Laminar burning velocity and a flame temperature were considered to analyze thermal efficiency and NOx emission.
The results show that D-EGR system is able to make a similar level of thermal efficiency to that of conventional SI
engines. NOx emission were reduced by decreasing flame temperature while the laminar burning velocity was increased
without flame temperature rising due to the influence of H2 and CO that were included in EGR gas as intermediates.

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“Dedicated EGR”による高効率天然ガスSI エンジンの可能性

尾崎恭平, 佐古孝弘, 李世埈, 飯田訓正

自動車技術会論文集（公益社団法人自動車技術会） 45 （ 5 ） 769 - 774 2014年09月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

High thermal efficiency with low emission can be realized by low-temperature combustion using EGR. Alger,T in SwRI proposed "Dedicated EGR" (a single sylinder run under rich condition and 100% of exhaust gas from this cylinder recirculated into the other cylinders.) to improve burning velocity by CO and H2 that included in EGR gas under high EGR ratio. This study investigates the dependence of burning velocity and flame temperature on equivalence ratio and EGR ratio by the combustion of premixed methane-air. Finally, it confirmed that "Dedicated EGR" had a potentiality of improving both thermal efficiency and NO emission.

二段噴射PCCI機関における燃焼騒音低減のための熱発生率制御に関する研究－素反応計算による0次元数値解析－

池田宏樹, 伊藤星太, 飯田訓正, 葛山裕史, 梅原努, 冬頭孝之

自動車技術会論文集（公益社団法人自動車技術会） 45 （ 5 ） 811 - 816 2014年09月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

A combustion method called Noise Cancelling Spike (NC-Spike) Combustion has been reported in the co-author’s previous paper, which reduces combustion noise in pre-mixed charge compression ignition with split injection. The overall combustion noise was reduced by lowering the maximum frequency component of the noise spectrum. In this paper, we investigates feasibility and controllability of the two-peak heat release rate during high temperature heat release by adding fuel in the adiabatic compression process of pre-mixed gas. The results show that the certain fuel addition timing generates the second heat release, and the interval of peak heat release rate could be controlled.

4.3 燃焼の化学反応 -エンジン高効率化のための低温燃焼のポテンシャルと課題- "Dedicated EGR"による高効率天然ガスSIエンジンの可能性

飯田訓正，尾崎恭平，李世埈

日本機械学会　イノベーションセンター研究協力事業委員会 RC255 先進的な計測技術と解析手法による燃焼現象の解明と技術進展に関する国際協力研究分科会　研究報告書（最終）（一般社団法人日本機械学会） 102-109 2014年03月

研究論文（その他学術会議資料等）, 共著

自動車と環境問題

飯田訓正

神奈川県「ガソリンベーパーを考えるシンポジウム」 2014年01月

研究論文（その他学術会議資料等）, 単著

特集・地球環境に向き合う <座談会> 3・11後、環境問題にいかに取り組むか

早見均，飯田訓正，厳網林，六車明，細田衛士

三田評論１２月号（ No.1174 （2014年1月号）） 10-25 2013年12月

研究論文（大学，研究機関等紀要）, 共著

1990年代から高まってきた地球環境問題への関心は、3・11以降新たなステージを迎えています。世界中で喫緊となっている代替エネルギーの問題、ＰＭ2.5に代表される越境汚染の問題など、その解決のために専門分野を横断する知の集結が求められています。慶應義塾では2011年から大学院博士課程でのグローバル環境システムリーダープログラムによる教育・研究を始めていますが、さらなる学部横断的な教育の取り組みの必要性が高まる中、環境問題の現在を考えていく特集です。

21世紀はサプライヤの時代

飯田訓正

ケーヒン技報（発行人：岩田毅編集：ケーヒン論文委員会，発行所：株式会社ケーヒン） 2 3-4 2013年11月

研究論文（学術雑誌）, 単著, ISSN 2187-3291

HCCI機関における燃焼時の圧力上昇率低減手法としての層状給気の効果

伊藤星太，池田宏樹，鄭棟元，飯田訓正

自動車技術会論文集（公益社団法人自動車技術会） 44 （ 5 ） 1205-1210 2013年10月

研究論文（研究会，シンポジウム資料等）, 共著, 査読有り

Closed-Loop Combustion Control of a HCCI Engine with Re-breathing EGR System

Yusuke Nakamura, Dong-Won Jung, Norimasa Iida

SAE Transaction （SAE International） SAE 2013-32-9069 /JSAE 20139069 2013年10月

研究論文（研究会，シンポジウム資料等）, 共著, 査読有り

(cont).... Due to the cycle-to-cycle variation, the change of total mass of fuel in cylinder has a big effect on IMEP. After misfire, unburned fuel and intermediates remain in exhaust gas, which is re-breathed as hot EGR gas, and unburned fuel and intermediates are supplied to next cycle. This leads to the total mass of fuel changes cycle-to-cycle. As a result of feedback control, transient performance is realized but high sensitivity of response cannot be achieved under the constant engine speed.

Numerical study of the effects of exhaust gas recirculation stratification on reducing the rate of pressure rise in dimethyl ether homogeneous charge compression ignition combustion

Narankhuu Jamsran, Ock Taeck Lim and Norimasa Iida

Proc IMechE Part D:J Automobile Engineering （IMechE） 227 （ 10 ） 1398-1397 2013年10月

研究論文（研究会，シンポジウム資料等）, 単著, 査読有り

This work investigates the potential of in-cylinder exhaust gas recirculation stratification for reducing the rate of pressure rise in dimethyl ether homogeneous charge compression ignition engines and its coupling with both thermal stratification and fuel stratification. Numerical analyses were performed using a five-zone version of the CHEMKIN-II kinetics rate code and the kinetic mechanics of dimethyl ether. The effects of inert components were used to represent the presence of exhaust gas recirculation in calculations. Three cases of exhaust gas recirculation stratification were tested in terms of both thermal stratification and fuel stratification at a fixed initial temperature, fixed initial pressure and fixed fuelling rate at bottom dead centre. In order to explore the appropriate stratification of exhaust gas recirculation, the exhaust gas recirculation width (defined as the difference between the exhaust gas recirculation ratios in zone 1 and zone 5 in the five-zone model) which we employed was from 0% to 30%. The case of exhaust gas recirculation homogeneity (called case 1), in which the exhaust gas recirculation width is 0%, was examined. In case 2, exhaust gas recirculation is located densely in a hot zone for combination with thermal stratification or in a fuel-rich zone for combination with fuel stratification. The last case (case 3) was the inverse of case 2. Ringing was reduced to an acceptable level in the case of fuel stratification with an appropriate exhaust gas recirculation distribution, which slowed the rapid burning during the compression stroke.

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会員サービス

飯田訓正

自動車技術（公益社団法人自動車技術会） 67 （ 7 ） 11 2013年07月

研究論文（学術雑誌）, 単著

1.4 希薄・希釈予混合気の化学反応過程 -EGR率がHCCI機関の着火燃焼過程に及ぼす影響-

飯田訓正，鄭棟元

日本機械学会　イノベーションセンター研究協力事業委員会 RC252 低炭素社会実現に資する高効率ディーゼル機関の燃焼の最適化および高度化に関する研究分科会　研究報告書（最終）（一般社団法人日本機械学会） 41-46 2013年06月

研究論文（その他学術会議資料等）, 共著

リブレッシングEGR型HCCI機関における燃焼のサイクル変動 ‐圧縮開始時質量平均ガス温度および化学種が燃焼位相に与える影響‐

中村祐介，山下和彦，鄭棟元，飯田訓正

自動車技術会論文集（公益社団法人自動車技術会） 44 （ 3 ） 795-800 2013年05月

研究論文（研究会，シンポジウム資料等）, 共著, 査読有り

本研究はHCCI機関について，圧縮開始時質量平均ガス温度およびEGR率が燃焼位相に与える影響を調査した．HCCI機関に供給する３種のガス(空気と燃料の予混合気・高温EGRガス・低温EGRガス)の比率は，吸排気系に設けたスロットルバルブによって制御した．また，燃焼位相が過度に遅延したときに起きる燃焼変動のメカニズムの解析を行い，得られた知見をもとに燃焼変動低減のための制御アルゴリズムを構築しその性能の評価を行なった．

A Computational Study of the Combined Effects of EGR and Boost Pressure on HCCI Autoignition

Dong Won Jung, Norimasa Iida

SAE Transaction （SAE Intenational） SAE 2012-32-0076 /JSAE 20129076 2012年10月

研究論文（研究会，シンポジウム資料等）, 共著, 査読有り

エコドライブ時のCO2削減効果の検証とリアルワールドエミッションの解析 - ディーゼル貨物車運転時のエコドライブ運転技術とCO2，NOx排出特性との関係 -

佐藤進，鈴木央一，宮雅芳，飯田訓正

自動車技術会論文集（公益社団法人自動車技術会） 43 （ 05 ） 1145-1150 2012年09月

研究論文（研究会，シンポジウム資料等）, 共著, 査読有り

講座テキスト：近未来ディーゼルエンジンの燃焼研究

飯田訓正

第8回自動車工学中級講座「環境規制とディーゼル技術の振り返り・これから」講座テキスト（公益法人自動車技術会） 2012年07月

研究論文（研究会，シンポジウム資料等）, 単著

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