Chemical mechanistic analysis of additive effects in homogeneous charge compression ignition of dimethyl ether

Yamada, Hiroyuki; Yoshii, Masataka; Tezaki, Atsumu

doi:10.1016/j.proci.2004.08.253

Cited by 78 publications

(33 citation statements)

References 27 publications

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“…Detailed chemical models of DME oxidation at low-temperature were proposed by Dagaut et al [8] and Curran et al [10,11], which have been validated by the experimental results of jet-stirred reactors [8], flow reactors [11], shock tubes [18] and Two-stage Ignition of DME/air Mixture at Low-temperature (<500K) under Atmospheric Pressure 6 others [13,19,20]. These models have been developed based on the typical two-stage oxidation mechanisms for long-chain hydrocarbons [21].…”

Section: Introductionmentioning

confidence: 88%

Two-stage ignition of DME/air mixture at low-temperature (<500 K) under atmospheric pressure

Gao

Nakamura

2013

Fuel

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Low-temperature ignition characteristics of dimethyl ether (DME)/air mixture were studied in an external heated, straight-shaped, plug-flow reactor under atmospheric pressure. Auto-ignition of the mixture was attained under a specific narrow range of temperature and equivalence ratio with relatively longer exposure time. Three kinds of ignition behaviors were identified accordingly as the equivalence ratio increased, such as (1) periodic hot flames, followed by (2) periodic two-stage ignitions (weak flame(s) and subsequent hot flame), lastly (3) chaotic weak flames. Time-sequential gas analyses were conducted for the case showing a typical periodic two-stage ignition in order to investigate the mechanism of the observed low-temperature auto-ignition under 500 K. The results revealed that the formation of CH 4 and C 2 H 2 was promoted prior to the hot flame ignition, suggesting that the chain-branching reaction pathway might exist.The transition from weak flame to hot flame was clearly observed as the mixture equivalence ratio decreased, implying the oxygen could be responsible to trigger this transition. It is suspected that the chain-branching precursor CH 2 OCH 2 OOH radicals should be relatively stable in the examined temperature range here, thus can gradually accumulate through a longer exposure time, and eventually give rise to the chainbranching explosion.* Corresponding author. Address: Hokkaido University, Kita13 Nishi8, Kita-ku, Sapporo 060-8628, Japan. Tel. & fax: +81-11-706-6386. E-mail address: yuji-mg@eng.hokudai.ac.jp Two-stage Ignition of DME/air Mixture at Low-temperature (<500K) under Atmospheric Pressure 2 Keywords: dimethyl ether, low-temperature oxidation, low-temperature auto-ignition, flames with repetitive extinction and ignition (FREI), two-stage ignition, cool flame.Two-stage Ignition of DME/air Mixture at Low-temperature (<500K) under Atmospheric Pressure 3 Highlights ► Auto-ignition of DME/air mixture was captured in a specific narrow range in temperature and equivalence ratio. ► Weak flame is transited to hot flame as equivalence ratio decreases.► CH 4 and C 2 H 2 formed due to the chain-branching reaction pathways.

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Section: Introductionmentioning

confidence: 88%

Two-stage ignition of DME/air mixture at low-temperature (<500 K) under atmospheric pressure

Gao

Nakamura

2013

Fuel

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“…Though the initiation reaction is the H abstraction from DME by oxygen, the largest part of CH 3 OCH 2 is produced by the following H abstraction reaction by OH in the low-temperature oxidation of DME [15]. [16]. When hydrogen and carbon monoxide are introduced to this low-temperature oxidation process of DME, they supposedly consume OH in the following reactions.…”

Section: Reaction Mechanism Of Ignition Controlmentioning

confidence: 99%

An HCCI combustion engine system using on-board reformed gases of methanol with waste heat recovery: ignition control by hydrogen

Shudo¹

2006

IJVD

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Adjusting a proportion of two fuels with different ignition properties is an effective technique for controlling the ignition timing in HCCI combustion. This research newly proposes an HCCI combustion engine system fuelled with dimethyl ether (DME) having a high cetane number and methanol-reformed gas (MRG) having a high anti-knock property. In the system, both DME and MRG are to be produced from methanol by onboard reformers utilising the exhaust heat from the engine. Because the reactions producing DME and MRG are endothermic, a part of exhaust heat energy can be recovered during the fuel reforming process. This research experimentally investigated characteristics of combustion, exhaust emissions, engine efficiency and overall thermal efficiency including the waste heat recovery through the fuel reforming in the HCCI combustion engine system. Because MRG consists of hydrogen and carbon monoxide, effects of the two on the autoignition of DME were also analysed.Keywords: DME; HCCI; hydrogen; ignition control; methanol; on-board reforming; waste heat recovery.Reference to this paper should be made as follows: Shudo, T. IntroductionIt is expected that the use of homogeneous charge compression ignition (HCCI) combustion in internal combustion engines will result in the higher thermal efficiency and the lower NOx emission as compared with conventional combustion systems. However, the difficulty in controlling the ignition timing in accordance with the engine load is preventing the HCCI combustion from its practical application to vehicles. Adjusting the proportion of two fuels with different ignition properties has been reported as a technique to control the ignition timing and load in HCCI combustion [1,2]. However, this technique has not been practically used for vehicles because of the obvious inconvenience of carrying two kinds of fuels onboard. On the other hand, dimethyl ether (DME) has been studied as a clean alternative to the diesel fuel due to its high cetane number and smokeless combustion [3][4][5]. DME can be easily produced from methanol by the dehydration reaction [6]. There has been reported an idea to use a small amount of DME that was produced from methanol as an ignition improving agent in a methanol direct-injection diesel engine [3]. Methanol also can be thermally decomposed to methanol-reformed gas (MRG) that consists of hydrogen and carbon monoxide. Since both hydrogen and carbon monoxide have high anti-knock properties [7], MRG has been studied as a fuel for spark-ignition engines [8,9]. For this background, the author newly proposes an HCCI combustion engine system that is fuelled with DME and MRG. Because the ignition properties of DME and MRG are largely different, adjusting the proportion of the two fuels could control the ignition timing in the HCCI combustion engine fuelled with them. In addition to the ignition control, the author also proposes productions of DME and MRG by onboard methanol reformers utilising the exhaust gas heat of the HCCI engine as shown in Figure 1. Bec...

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“…Other groups investigated the behavior of alcohols in HCCI engines, including neat butanol [20] and ethanol [20,[24][25][26]; wet ethanol also received significant attention as a neat fuel due to the potential for increased overall energy efficiency by avoiding or reducing distillation and dehydration [27][28][29]. The low reactivity of alcohols such as ethanol and methanol motivated additional research into operating HCCI engines using blends with more reactive fuels/additives such as n-heptane [30], diethyl ether [31,32], dimethyl ether [33][34][35][36], and di-tertiary butyl peroxide [37]. In the opposite direction, other efforts studied injecting water into the engine cylinder to temper the reactivity of highly reactive fuels [33,[38][39][40][41].…”

Section: Introductionmentioning

confidence: 99%

Investigation of the LTC fuel performance index for oxygenated reference fuel blends

Niemeyer

Daly

Cannella

et al. 2015

Fuel

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A new metric for ranking the suitability of fuels in LTC engines was recently introduced, based on the fraction of potential fuel savings achieved in the FTP-75 light-duty vehicle driving cycle. In the current study, this LTC fuel performance index was calculated computationally and analyzed for a number of fuel blends comprised of n-heptane, isooctane, toluene, and ethanol in various combinations and ratios corresponding to octane numbers from 0 to 100. In order to calculate the LTC index for each fuel, computational driving cycle simulations were first performed using a typical light-duty passenger vehicle, providing pairs of engine speed and load points. Separately, for each fuel blend considered, single-zone naturally aspirated HCCI engine simulations with a compression ratio of 9.5 were performed in order to determine the operating envelopes. These results were combined to determine the varying improvement in fuel economy offered by fuels, forming the basis for the LTC fuel index. The resulting fuel performance indices ranged from 36.4 for neat n-heptane (PRF0) to 9.20 for a three-component blend of n-heptane, isooctane, and ethanol (ERF1). For the chosen engine and chosen conditions, in general lower-octane fuels performed better, resulting in higher LTC fuel index values; however, the fuel performance index correlated poorly with octane rating for less-reactive, higher-octane fuels.

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Chemical mechanistic analysis of additive effects in homogeneous charge compression ignition of dimethyl ether

Cited by 78 publications

References 27 publications

Two-stage ignition of DME/air mixture at low-temperature (<500 K) under atmospheric pressure

Two-stage ignition of DME/air mixture at low-temperature (<500 K) under atmospheric pressure

An HCCI combustion engine system using on-board reformed gases of methanol with waste heat recovery: ignition control by hydrogen

Investigation of the LTC fuel performance index for oxygenated reference fuel blends

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