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柴油机燃用柴油_甲醇混合燃料时的燃烧特性研究_英文_

第 21 卷 ( 2003) 第 6 期 Article ID: 1000 0909 ( 2003) 06 0401 10

内 燃 机 学 报 Transactions of CSICE

Vol. 21( 2003) No . 6

21 098

Study on Combustion Characteristics of a DI Diesel Engine Operating on Diesel/ Methanol Blends
HUANG Zuo hua, LU Hong bing, JIANG De ming, ZENG Ke, LIU Bing, ZHANG Jun qiang, WANG Xi bin
( Department of Automobile Engineer ing , Xi an Jiaotong U niv ersity, Xi an 710049, China)

Abstract : A stabilized diesel/ methanol blend w as r ealized and the combustion characteristics and heat release anal ysis of the diesel/ methanol blend w as car ried out in a DI diesel engine. T he study show ed that the increase of methano l mass fraction of diesel/ met hanol blends will result in the incr ease of heat release rate in premix ed burn ing phase and shorten t he combustion duration of diffusive bur ning phase. Ignition delay increases with the in crease o f methanol mass fraction and the behavior is more obviously at low eng ine load and high eng ine speed. Rapid burn duration varies less w ith methanol mass fract ion and the total combustion duration decreases w ith the incr ease of methanol mass fraction. A t a low engine speed, t he centre o f heat release cur ve tends to be close to the top dead centr e w ith the incr ease of methanol mass fr action at all engine loads and fuel deliv er y advance angles, and the maximum rate of pressure rise and the max imum r ate o f heat r elease increase wit h the increase of methano l mass fraction. A t a high eng ine speed, the centre of heat release curv e closes to the top dead centre with the increase o f methanol mass fraction at high eng ine load and will depart from the top dead centr e at low eng ine load, and the maximum rate of pr essure rise and the maximum rate of heat release gives an increasing trend with the increase of the methano l mass fr action and a slight decreasing trend with further increasing of methano l mass fractio n. M ax imum cylinder gas pressure increases w ith the increase of methano l mass fraction when ox ygen mass fraction is less than 6% , and then it remains a constant value or dr ops slightly with a further incr ease of oxy gen mass fract ion. M ax imum mean gas temper ature r emains almost unchang eable versus methanol mass fract ion. Keywords: Combustion; Heat release analysis; Diesel/ methanol blends; DI engine CLC number: T K464 Document code: A

Notation
A A T DC b e ( bsfc) p bm ep BT DC cp cV C dp d d QB d w all area after top dead centre brake specific fuel consumption brake mean effective pressure befor e top dead centre constant pressur e specific heat constant volume specific heat mass fr action of carbo n in fuel blend, % ( w t)
m ax

dQ B d dQ w d hc Hu H m O p

max

max imum rate of heat release rate of heat transfer

heat transfer coefficient lower heating value mass fraction of hydrogen in fuel blend, % ( w t) mass of cy linder gases mass fract ion of ox ygen in fuel blend, % ( w t) cylinder g as pressure

max imum rate of pressure rise rate of heat release

收稿日期 : 2003 07 02; 修订日期 : 2003 08 16。 基金项目 : 国家重点基础研究发展规划项目 ( 2001CB209208) ; 福特中 国研究与 发展基金 项目 ( 50122166 ) ; 国家自 然科学基 金重点项 目 ( 50136040) 。 作者简介 : 黄佐华 ( 1963- ) , 男 , 博士 , 教授 , 主要研究方向为内燃机燃烧与有害排污控制。

! 402 ! p max R T T m ax Tw T DC V
c

内 max imum cylinder gas pressure gas constant mean gas temperatur e max imum mean gas temperature wall temperature top dead centre cy linder volume






e ig rb s tb e fd e

报 crank ang le of heat r elease ending ignition delay rapid bur ning duration cr ank angle of heat release beginning total combustion dur atio n effective ther mal efficiency fuel delivery advance ang le effective ther mal efficiency

第 21 卷第 6 期

crank angle of the centre of heat release curve

Introduction
Reduct ion of eng ine emissions is a m ajor research aspect in engine development w it h t he more concern in environmental protect ion and t he st ringent exhaust g as regulat ion, it is difficult to simult aneously reduce NO x and smoke in a normal diesel eng ine due t o the trade of f curve betw een NO x and smoke. One prospect ive method t o solve t his problem is to use the ox ygenat ed alt ernat ive f uels or to add t he oxyg enated fuels in diesel fuel t o provide more ox ygen during the combust ion. In t he ut ilization of pure oxygenated f u els, F leisch et al , Kapus et al al
[ 3] [ 1] [ 2]

et al[ 9] st udied the diesel/ et hanol blends for emission reduct ion and Bert oli et al[ 10] , M iy amoto et al[ 11] and Akasaka et al[ 12] also conducted research on diesel combustion improvement and emission reduct ion by using various t ypes of the ox ygenat ed fuel blends. Methanol is regarded as one of the promising al ternative fuel or an ox ygen addit ive in diesel engine w it h its advantages of low price and high ox ygen frac t ion, how ever, due to the dif ficult y in forming a st a bilized diesel/ met hanol blend, f ew work w as found in such aspect , and t he previous work w as m ainly con centrated on t he applicat ion of diesel/ et hanol blend in t he compression ignit ion engine
[ 13, 14]

and Sorenson et

. T herefore,

have studied the dimet hyl et her ( DME) in the

much work is needed in the utilizat ion of diesel/ methanol blend in the com pression ignit ion engine for clarif ying the basic combust ion and emission charac terist ics and providing an approach for at t aining t he st abilized diesel/ methanol blend w it h some solvent, and the study is expect ed to supply more informat ion on eng ine combustion operating on the oxygenated fu els and provide more practical measures f or t he im provement of combust ion and reduct ion of emissions. Based on t he authors previous study, the objec t ive of t his study is to form a st abilized diesel/ methanol blend by adding a specific solvent and then t o invest igate the combustion characterist ics and heat release process of a compression ignition engine oper at ing on t he diesel/ met hanol blends.

modif ied diesel eng ine, and t heir result s showed t hat the engine could achieve an ult ra low emission prospect w ithout a f undament al change in combustion syst ems. Huang et al
[ 4]

invest ig at ed t he combustion

and emission charact eristics in a com pression ig nition eng ine w it h DME and found t hat DM E engine had a high t herm al ef ficiency, a short premixed combustion phase and a fast dif fusive combustion phase, and t heir advant age is low no ise, smoke free combustion. Kaji t ani et al
[ 5]

studied the DME engine w ith retarding

the inject ion t im ing t o reduce bot h smoke and NO x . Pract ically, adding some ox ygenat ed compounds in diesel fuel to reduce engine em issions w ithout the eng ine modif icat ion seems to be more at t ract ive, Huang et al t est ed t he g asoline ox ygenat e blends in a spark ignited engine and got a sat isfactory result s on emission reduct ion[ 6] and invest igated the combustion and em ission characterist ics of diesel/ dimet hyl car bonat e ( DMC ) in a compression ignit ion eng ine . M urayama et al
[ 8] [ 7]

1

Test Engine and Fuel Properties
T he specif icat ions of t he t est engine are listed in

t able 1. T hree kinds of diesel/ met hanol blends w ere designat ed f or st udy. Due to the low solubilit y of methanol in t he diesel fuel, a solvent was added int o t he diesel/ met hanol blends t o form t he stabilized

st udied the em issions and combus

t ion w ith EGR and dimet hyl carbonate ( DM C) . Ajav

2003 年 11 月

黄佐华等 : 柴油机燃用柴油 / 甲醇混合燃料时的燃烧特性研究 ( 英文 )

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diesel/ met hanol blends. F uel propert ies and t he con st it ut ions of three blends are given in t able 2, t able 3 and figure 1, and t he ox ygen fract ion in t he f uel blends ranges from 5 87 t o 11 1 as shown in F ig. 2. It can be seen t hat t he oxygen in the fuel blends is mainly come f rom the addit ion of methanol alt houg h the mass fract ion of methanol and solvent has the same level, so it is reasonable to regard the inf luence of oxygen in the fuel blends as to be the inf luence of ox ygen from t he addit ion of met hanol. T he f uel prop erties show that met hanol has hig h oxyg en cont ent w hile t he heat value is less and cetane number is low comparing to t he diesel fuel. In t he ex periment, the above t hree fuel blends w it h diff erent met hanol pro port ion were operated on t he eng ine, meanwhile com bustion characterist ics and exhaust emissions were
Tab 2

measured and analysed at the same brake mean ef fec t ive pressure ( bmep) , f urt hermore, t hese paramet ers w ere made a comparison w it h those of pure diesel combustion in order to clarif y t he ef fect of oxygenate additive on combust ion. A Horiba exhaust gas analy z er was used t o measure t he combustion product s.
Tab 1
Bore St rok e Displacem ent Com pression ratio Combust ion chamber Rat ed pow er/ speed N ozzle hole diameter Number of nozzle hole

Engine specifications
100 mm 115 mm 903 cm 3 18 ! type 11 kW/ ( 2 300 r/ min) 0. 3 mm 4

Fuel properties of diesel, methanol, solvents and blended fuel constitutions
Base f uel D iesel Blen ded f uel M ethanol CH 3O H 32 0 0. 796 0 19. 678 1 110 470 5 37. 5 12. 5 50. 0 8. 96 13. 33 17. 66 Solvent s Solvent 1 C x Hy O z 282 0 0. 890 5 38. 650 200 335 40 76. 6 12. 0 11. 4 10. 10 14. 47 16. 60 S olvent 2 C aH bO c 74 0 0. 802 0 34. 000 580 385 10 64. 8 13. 5 21. 7 1. 08 0. 92 1. 80

C hemical formula M ole w eight / g Densit y/ ( g/ cm ) Low er heat ing value / ( M J / kg) Heat of evaporat ion / ( kJ/ kg) Self ignit ion t emperat ure / ? Cet ane number C / % ( w t) H / % ( w t) O / % ( w t) Blended fuel 1 / % ( w t ) Blended fuel 2 / % ( w t ) Blended fuel 3 / % ( w t )
3

C 10. 8 H 18. 7 148. 3 0. 860 0 44. 000 260 200~ 220 45 86. 0 14. 0 0. 0 79. 86 71. 28 63. 94

Tab 3

Fuel properties of the diesel/ methanol blended fuel
Blended f uel 1 Blended fuel 2 39. 89 367. 57 38. 43 77. 98 13. 50 8. 52 Blen ded f uel 3 38. 64 405. 94 6. 21 75. 50 13. 40 11. 10

Low er heat ing value / ( M J / kg) Heat of evaporat ion / ( kJ/ kg) Cet ane number C / % (w t) H / % ( w t) O / % ( w t)

41. 73 333. 53 40. 41 80. 47 13. 66 5. 87

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第 21 卷第 6 期

In w hich ning and

s e

is t he crank angle of heat release begin is t he crank ang le of heat release ending.

F igure 3 illustrates t he heat release rate of diesel/ methanol blends d Q B/ d at t he eng ine speed of 1 500 r/ min, t hose at the engine speed of 2 000 r/ min are show n in Fig. 4. T he results show that t he increase in methanol mass fraction ( or oxyg en mass f ract ion) w ill result in t he increase of t he heat release rat e and t he f ract ion of fuel burned in t he premixed
Fig. 1 Constitution of the fuel blends

combustion phase, and the behavior is more obviously at a high engine load. T he f igure also indicat es a de lay of the heat release initiat ing t im ing in t he case of diesel/ methanol blends compared wit h that of pure diesel fuel, and this delay w ill increase w ith t he in crease of met hanol mass fract ion in fuel blends, more over, this delay phenomenon t ends to be more obvi ously at t he low engine load or at t he high engine speed. An increase in met hanol m ass fraction ( ox ygen mass fract ion) w ill cause a decrease in cetane number

Fig. 2

Oxygen mass fraction in fuel blends

of the fuel blends, w hich in t urn result s in a long ig nit ion delay, and event ually brings about an increase of the heat release rat e and the f ract ion of f uel burned in the premixed combust ion phase. M ore fuel is need ed in the case of diesel/ methanol blends for get ting t he same brake mean effect ive pressure ( bm ep) and t his cause an increase in durat ion of f uel inject ion, furthermore, the oxygen enrichment by inject ing t he oxygen contained fuel blends w ill im prove the com bust ion in t he diff usive burning phase and can short en t he combust ion durat ion of the dif fusive burning phase as being clearly show n in F ig . 3 and F ig. 4. Heat release process almost com pleted at the same crank angle and this in anot her aspect prov ided an ev idence to support the fast diffusive burning phase in t he case of diesel/ methanol blend operation. Since low eng ine load result s in low gas t emperat ure in t he cy linder, and the ignit ion delay w ould be largely af fected by cetane number under such circumst ance, t hus, relat ive a large ignition delay w ill occur at t he low eng ine load. As the ignit ion delay represents t he preparation of the physical and chem ical pre flame ( 3) processes and it varies litt le in the time scale ( ms) , how ever, it w ill increase w it h an increase of engine speed in the scale of crank angle. At t he low engine

2

Results and Discussions
Heat release rat e ( d Q B/ d ) is calculated by us

ing t he follow ing formula: dQ B cp d V c V V d p dcV dQ w = p! + + mT + ( 1) d R d R d d d Where heat t ransfer rat e is given by dQ w/ d = hcA ( T - T w) transfer coef ficient .
[ 15]

( 2)

Heat transfer coeff icient h c uses the Woschni s heat T he ignit ion delay is t he t ime int erval f rom the beginning t im ing of nozzle valve lif t t o t he beginning timing of rapid pressure rising; t he rapid combustion durat ion is t he t ime int erval from the beginning tim ing of rapid pressure rising t o the ending t iming of rapid pressure rising, the t otal combust ion durat ion is the t ime interval f rom t he beginning timing of heat release to t he ending t iming of heat release. T he crank angle of the cent re of heat release curve is de t ermined by the f ollow ing formula:

c=

# #
e s

dQ B ! !d d e dQ B d d s

2003 年 11 月

黄佐华等 : 柴油机燃用柴油 / 甲醇混合燃料时的燃烧特性研究 ( 英文 )

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load, the heat release curves also revealed a sharp and short premixed burning patt ern at low engine speed ( 1 500 r/ min) and a flat and long prem ixed burning pat tern at high engine speed ( 2 000 r/ min) , and t his

can also be ex plained by t he influence of ignit ion delay in the scale of crank angle, as long ig nit ion delay w ill make t he combust ion prolong to a lat e st age as being show n in F ig . 4.

Fig. 3

Heat release rate of the fuel blends at 1 500 r/ min

Fig. 4

Heat release rate of the fuel blends at 2 000 r/ min

Figure 5 g ives t he ignit ion delay of diesel/ met hanol blends at fuel delivery advance ang le of 21?CA BT DC. Generally speaking, the ignit ion delay
ig

engine load t han that at high eng ine load. T he long ignit ion delay ( in crank angle scale) at high engine speed is due t o t he reason t hat high engine speed w ill correspond t o a larg e crank angle under t he same t ime scale ( ms) . In respect to t he rapid burn duration rb ( show n in F ig . 6) , it was found t hat methanol mass f ract ion had litt le influence on t he rapid burn dura t ion, alt houg h more fuel is needed in the case of oxy gen cont ained fuel blends, t he improvement of mix ing and combust ion due t o oxygen enrichment w ould also ensure a fast premixed combust ion. For a specif ic fuel, t he increase in the rapid burn durat ion is result f rom t he increase of t he cyclic f uel and a long heat re lease process. T he t otal combust ion durat ion
tb

show ed an increase w it h t he increase of methanol

mass fraction ( oxygen mass f ract ion ) in the f uel blends and t he behavior is more obviously at low en g ine load and high engine speed. As being explained above, the lowering of cetane number w it h t he in crease of methanol addit ion is responsible for t he in crease of ig nition delay ; moreover, an increase in the heat of evaporat ion of the blends w ill cause a t empera t ure drop of t he cylinder g ases, w hich also cause the increase of t he ignit ion delay. For a specific f uel, t he ignition delay increases w it h the decrease of eng ine load ( bmep) , and t his would be due to the inf luence from t he cylinder g as t em perature w ithin t he ig nition delay period as t he g as temperature is low er at low

de

creases w ith t he increase of met hanol mass fraction in t he diesel/ met hanol blends at all engine loads and en gine speeds ( F ig. 7) , and t his indicat ed t hat t he addi

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第 21 卷第 6 期

t ion of met hanol in diesel fuel w ould promote the combust ion and short en the combust ion durat ion. As being ex plained in t he above heat release analysis sec t ion, the f ast combustion rate in t he premix ed com

bust ion phase as w ell as in t he subsequent ly diffusive combustion phase results in t he decrease of the total combustion durat ion f or diesel/ met hanol fuel blends.

Fig. 5

Ignition delay of the fuel blends

Fig. 6

Rapid combustion duration of the fuel blends

Fig. 7

Total combustion durations of the fuel blends

F ig ure 8 show s the crank ang le posit ion of the centre of heat release curve c of diesel/ methanol blends at f uel delivery advance angle fd = - 21?CA BT DC. T he behavior of
c versus

min) , w here the centre of heat release curve shows a decrease w it h t he increase of methanol m ass f ract ion at all engine loads and f uel delivery advance angles, t he f ast combust ion rat e at t he prem ix ed burning phase and t he subsequent ly dif fusive burning phase make t he cent re of heat release curve to be more close

met hanol mass frac

t ion ( ox ygen mass fract ion) can be classif ied int o t wo types, one is t he case at low eng ine speed ( 1 500 r/

2003 年 11 月

黄佐华等 : 柴油机燃用柴油 / 甲醇混合燃料时的燃烧特性研究 ( 英文 )

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to t he top dead cent re ( T DC) . Anot her is t he case at high engine speed ( 2 000 r/ min) , w here
c

heat release curve w ould be ex tended t o a late phase ( as show n in F ig. 4) and make the cent re of heat re lease curve ext end to a lat e phase. However, at high engine load, the ignit ion delay gives less variat ion versus t he met hanol addit ion, in t his case, t he f ast premix ed combustion and diffusive combust ion w ould make t he cent re of heat release curve t o be close t o T DC.

show s a

decrease w it h the increase of t he methanol mass frac t ion at high eng ine load ( p bm ep = 0 608 M Pa) , an in crease at low engine load ( p bmep = 0 208 M Pa) and less variat ion at m iddle eng ine load ( p bmep = 0. 392 M Pa) . Since t he increase of ignit ion delay is more ob viously in the case of hig h engine speed ( 2 000 r/ min) and low engine load ( p bmep = 0. 208 MP a) , the

Fig. 8

Centre of heat release curve of the fuel blends

F ig ure 9 shows t he m ax imum cylinder gas pres sure of diesel/ methanol blends p max and t he calculated max imum m ean gas temperature T max versus oxygen mass f ract ion is shown in F ig . 10. Except at low en g ine load, p max show s an increase w ith t he increase of met hanol m ass fract ion in diesel/ met hanol blends w hen t he oxygen mass f ract ion is less t han 6% , and then it remains less variable or drops slightly wit h furt her increasing of ox ygen mass fract ion, and the behavior can be observed at middle/ high loads and tw o engine speeds. Since p max is strongly relat ed to the amount of prepared fuel w ithin the ignit ion delay period ( premixed burning phase) and t he dropping of g as t emperat ure due to f uel evaporation, an increase in methanol mass fract ion will make more fuel to be burned in t he premixed com bust ion phase, and t hen causes an increase in p m ax . How ever, furt her increas ing of met hanol mass fract ion w ill bring drop t he tem perat ure due to t he increase of heat evaporat ion and the increase of cyclic fuel w ill increase t he const ant volume specif ic heat c V of mix ture that w ill rest rict furt her increasing of p max or even decrease p m ax at large met hanol mass fraction. T he calculat ed mean

gas temperature remains almost unchang eable versus methanol mass f ract ion, and t his sug gest s lit t le inf lu ence of m et hanol addition on the max imum mean gas t emperat ure under the same bmep condit ion. T
max

w ill reach it s peak value at a late phase than t hat of p m ax , and T max ref lect s t he combust ion of both pre mixed burning phase and t he subsequent ly diffusive burning phase. T w o fact ors af fect the value of T m ax , one is t he heat of evaporat ion and c V , and the other is combustion improvement of t he dif fusive burning phase. An increase of methanol m ass f ract ion w ill in crease the heat of evaporat ion and c V , which may lead t o the decrease of T max , how ever, t he combus t ion improvement in t he dif fusive burning phase due t o an oxygen enrichment favors to t he increase of T max , and the comprehensive result shows litt le inf lu ence of met hanol addit ion on T max for diesel/ met hanol blends. F igure 11 and 12 give t he max imum rat e of pres sure rise ( d p / d ) max and t he max imum rat e of heat release ( d Q B/ d ) m ax . At low engine speed ( 1 500 r/ min) , ( d Q B/ d ) max and ( d p / d ) max increase w ith t he increase of met hanol mass f ract ion and t he behav

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第 21 卷第 6 期

ior is more obv iously at high eng ine load. An increase of ignit ion delay w ith t he increase of met hanol mass fraction w ould make more f uel to be burned in the premixed burning phase and then increase ( d Q B / d ) max and ( d p / d ) max . H owever, at high eng ine speed ( 2 000 r/ min) , ( d Q B/ d ) max and ( d p / d ) max shows a relatively hig h increasing trend w ith t he in crease of methanol mass fract ion ( ox ygen mass frac t ion) at high engine load ( p bmep = 0 608 MP a) , a relat ively low increasing t rend w ith t he increase of

methanol mass fract ion at middle engine load ( p bmep = 0. 392 M Pa) and a slight decreasing trend w ith t he increase of met hanol mass fraction at low engine load ( p bm ep = 0. 208 M Pa) . A large increase of t he ignit ion delay w it h the increase of methanol mass f ract ion at low engine load and hig h engine speed ( 2 000 r/ min) is considered to the reason for t he de crease of ( d Q B/ d ) max and ( d p / d ) m ax at low en gine load.

Fig. 9

Maximum cylinder gas pressure of the f uel blends

Fig. 10

Maximum mean gas temperature of the fuel blends

Fig. 11

Maximum rate of pressure rise of the fuel blends

2003 年 11 月

黄佐华等 : 柴油机燃用柴油 / 甲醇混合燃料时的燃烧特性研究 ( 英文 )

! 409 !

Fig. 12

Maximum heat release rate of the f uel blends

3

Conclusions
A st abilized diesel/ met hanol blend was realized

( 4)

M ax imum cylinder g as pressure increases

w it h t he increase of met hanol mass fract ion w hen t he oxygen mass fraction is less t han 6% , and t hen it re mains less variable or drops slight ly w ith further in creasing of oxyg en m ass fraction. M ax imum mean gas t emperat ure remains almost unchangeable versus methanol mass f ract ion. References:
[ 1] F leisch T , M cCar thy C, Basu A. A N ew Clean Diesel T echnology: Demonstration of U LEV Emissions on a N avistar Diesel Eng ine Fueled wit h Dimethy l Ether [ J] . SAE T ransactions, 1995, 104( 4) : 42~ 53. [ 2] Kapus P , Ofner H. Development of F uel Injection Equip ment and Combustion System for DI Diesels O perated on Dimet hyl ether [ J] . SA E T r ansact ions, 1995, 104( 4) : 54~ 69, 1995. [ 3] Sorenson S C, M ikkelsen S E. Performance and Emis sions of a 0 273 Liter Direct I njection Diesel Engine F u eled w ith N eat Dimethy l Ether [ J] . SA E T ransactions, 1995, 104( 4) : 80~ 90. [ 4] Huang Z H, Wang H W, Chen H Y . Study on Combus tion Characteristics of a Compression I gnition Engine F u eled w ith Dimethyl Ether [ J] . P roceedings of the I nstitu tion of M echanical Eng ineers, Part D, Jour nal of A uto mobile Engineering , 1999, 213 ( D6) : 647~ 652. [ 5] K ajitani Z, Chen L, Konno M . Engine P erformance and Ex haust Characteristics of Direct Injection Diesel Engine O perated with DM E[ J] . SA E T ransactions, 1997, 106 ( 4) : 1568~ 1577. [ 6] Huang Z, M iao H, Zhou L , Jiang D. Combustion Char acter istics and Hydrocarbon Emissions of a Spark Ignition Engine F uelled with Gasoline Ox ygenate Blends[ J] . Pro ceedings of t he Institution of M echanical Engineers, P ar t D, Journal of Automobile Engineer ing , 2000, 214

and t he combustion charact eristics based on t he heat release analysis w ere analysed, and main result s are summarized as follow s: ( 1) Increasing met hanol mass fract ion of diesel/ met hanol blends w ill result in t he increase of heat release rat e in t he premixed burning phase and shorten t he combust ion durat ion of t he dif fusive burn ing phase. ( 2) Ignit ion delay increases w ith t he increase of met hanol mass fract ion and t he behavior is more obv iously at low engine load and high engine speed. Rapid burn durat ion varies litt le w it h met hanol mass fraction and t he t otal combust ion durat ion decreases w it h the increase of methanol mass f ract ion. ( 3) At low engine speed, the cent re of heat re lease curve t ends to be close t o the t op dead cent re w it h the increase of m et hanol mass fract ion at all en g ine loads and fuel delivery advance angles, and the max imum rate of pressure rise and t he maximum rat e of heat release increase w it h t he increase of methanol mass f ract ion. At high eng ine speed, the cent re of heat release curve closes t o t he t op dead cent re wit h the increase of met hanol mass fract ion at high eng ine load and departs f rom t he top dead centre at low en g ine load. Maximum rat e of pressure rise and maxi mum rate of heat release give an increasing t rend wit h the increase of met hanol mass fract ion and a slight de creasing trend w it h t he increase of met hanol mass fraction.

! 410 ! ( D3) : 341~ 346. [ 7]







学 [ 11]



第 21 卷第 6 期 M iyamoto N , O gawa H , Obata K . Improv ements of Diesel Combust ion and Emissions by Addition of Ox y genated Agents to Diesel Fuels: I nfluence o f Propert ies of Diesel Fuels and K inds of Ox ygenated A gents [ J] . JSAE Review, 1998, 19( 2) : 154~ 156.

Huang Z H, Jiang D M , Zeng K, Liu B, Y ang Z L . Combustion Char acteristics and Heat Release Analysis of a DI Compression Ignition Eng ine Fueled w ith Diesel Dimethyl Carbonate Blends[ J] . Proceedings of the Insti tution of M echanical Engineers, Part D, Jour nal of Auto mobile Engineering , 2003, 217( 7) : 595~ 606. [ 12]

Akasaka Y, Sakurai Y . Effect of Oxy genated Fuel on Exhaust Emission from DI Diesel Engines[ J] . T ransac tions of JSM E, 1996, Ser ies B, 63( 609) : 1833~ 1839.

[ 8]

M urayama T , Zheng M , Chikahisa T . Simultaneous Re duction of Smoke and N Ox fr om a D I Diesel Engine with EGR and Dimethyl Carbonate[ C] . SA E Paper 952518, 1995.

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柴油机燃用柴油 / 甲醇混合燃料时的燃烧特性研究
黄佐华, 卢红兵, 蒋德明, 曾 科, 刘 兵, 张俊强, 王锡斌
( 西安交通大学 汽车工程系 , 陕西 西安 710049) 摘要 : 通过添加助溶剂形成一种稳定的柴油 / 甲醇混 合燃料 , 并 开展了 柴油机燃 用此混 合燃料 的燃烧 特性 研究。研究结果表明 : 随着混合燃料中甲醇含量的增加 , 预混燃烧阶段的放 热率增加 , 扩散燃 烧时间缩短 。 滞燃期随甲醇含量的增加而增加 , 此现象在 低负荷 和高转速 下更为 明显。甲醇 含量对 快燃期 长短影 响较 小 , 总燃烧期随甲醇含量的增加而缩短。低转速下放热率曲线中心随甲 醇含量的 增加而移近 上止点 , 最大 压力升高率和最高放热 率随甲醇含量的增加而增加。高转速高负荷下放热率 曲线中心随 甲醇含量 的增加 而移近上止点 , 高转速低负荷下放热率曲线中心随甲醇含量的增加偏离 上止点 ; 高转速下 最大压力 升高率 和最高放热率随甲醇含量的增加 而增加 , 而进一 步增加 甲醇含 量反而 使最大压 力升高 率和最 高放热 率降 低。当混合燃料中含氧量小于 6% 时 , 缸内最高压力随甲醇含 量的增加而 增加 ; 进一步 增加含 氧量时 缸内 最高压力保持不变或略 有降低。缸内最高平均气体温度基本上不随甲醇含量而变化。 关键词 : 燃烧 ; 放热率 ; 柴油 / 甲醇混合燃料 ; 柴油机