張 韋，陳朝輝，孔孟茜，趙羅峰，包廣元

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柴油機催化型顆粒捕集器噴油助燃再生特征

張 韋，陳朝輝※，孔孟茜，趙羅峰，包廣元

（昆明理工大學(xué)交通工程學(xué)院，云南省內(nèi)燃機重點實驗室，昆明 650500）

針對在用車輛的排放升級改造，以及滿足非道路移動源四階段排放標(biāo)準(zhǔn)限制要求，該文基于自主開發(fā)的噴油助燃主動再生系統(tǒng)，開展了加裝DPF（diesel particulate filter）和不同CDPF（catalyzed diesel particulate filter）后處理器的發(fā)動機外特性試驗和噴油助燃主動再生燃燒試驗。結(jié)果表明：催化劑負(fù)載量為530 g/m3的CDPF，對外特性下發(fā)動機的動力性和經(jīng)濟性影響較小，并為碳煙再生提供了充足的NO2組分，因而其最大排氣壓差比DPF低8.8 kPa。630 ℃時無二次供氣的CDPF其再生效率高達(dá)96.4%，載體最高溫度比DPF低31 ℃；采用二次供氣速率1.25 L/s、時長180 s，繼續(xù)供氣速率0.625 L/s、時長420 s的再生方案，600℃時CDPF的再生效率為83.2%，載體最高溫度比無二次供氣時降低了64 ℃；進(jìn)行停機再生與怠速再生時，催化劑負(fù)載量為530 g/m3的CDPF具有更好的再生特性，其停機再生效率為76.4%，怠速再生效率達(dá)到88.5%。本研究對開發(fā)安全、高效的主動再生系統(tǒng)具有借鑒意義，并可為催化條件下的主動再生策略研究提供數(shù)據(jù)支撐。

柴油機；燃燒；催化劑；再生； DPF；CDPF；噴油助燃；臺架試驗

0 引 言

柴油機具備動力性強、經(jīng)濟性好和熱效率高等優(yōu)點，被廣泛應(yīng)用于以農(nóng)業(yè)機械和工程機械為代表的非道路移動機械[1]。但由于柴油機的PM排放較高，且非道路移動機械的保有量逐年持續(xù)增加[2]，因此所產(chǎn)生的PM排放問題日益突出。而DPF（diesel particulate filter）可有效捕集與去除PM，但要維持捕集器的持續(xù)、高效捕集，需對捕集器內(nèi)的碳煙進(jìn)行適時再生，常用的再生方式包括基于熱管理的主動再生[3]，以及涂覆催化劑的被動再生[4]。Kazuhiro Yamamoto[5]、Bai Shuzhan[6]等對催化再生PM的研究結(jié)果表明，被動再生熱負(fù)荷小，無需額外耗能，但非道路柴油機的工作條件惡劣，且工況運行范圍較寬，排氣溫度及成分波動大[7]，難于保證各工況下都能實現(xiàn)較高的再生效率。主動再生則是通過氧化催化器或燃燒器氧化碳?xì)淙剂蟍8]，快速提升排氣溫度起燃再生PM。部分學(xué)者對PM的主動再生過程開展了試驗與仿真計算研究[9-12]，王建等[13]對DPF主動再生溫度需求的柴油機進(jìn)氣節(jié)流控制策略開展了試驗測試，Waldermar Karsten等[14]對噴油助燃再生燃燒器的結(jié)構(gòu)進(jìn)行了數(shù)值模擬，Eric Hein等[15-16]開展了發(fā)動機缸內(nèi)遠(yuǎn)后噴及排氣管后噴燃料的試驗研究。Meng Zhongwei等[17]的試驗結(jié)果發(fā)現(xiàn)，主動再生時在高溫燃?xì)獾淖饔孟?，將在載體內(nèi)形成大梯度溫度分布，局部最高溫甚至超過1 000 ℃。因此，需要將主、被動2種再生方式進(jìn)行相互融合、取長補短，才能實現(xiàn)安全可靠的高效率再生[18]。然而，目前對基于DPF和CDPF（catalyzed diesel particulate filter）的噴油助燃主動再生方面的臺架試驗還比較欠缺，本文基于自主開發(fā)的主動再生燃燒系統(tǒng)，開展DPF和CDPF的主動再生燃燒特性試驗研究，以期為在用車輛的排放升級改造及非道路移動機械實現(xiàn)第四階段排放標(biāo)準(zhǔn)提供參考。

1 試驗系統(tǒng)

試驗測試的發(fā)動機為D30TCI型四缸直列高壓共軌柴油機，符合國Ⅳ排放標(biāo)準(zhǔn)，DPF與CDPF在發(fā)動機臺架中的安裝位置見圖1，發(fā)動機的主要技術(shù)參數(shù)見表1。測試用的DPF、CDPF1和CDPF2的具體參數(shù)見表2，其催化劑負(fù)載量分別為0、530和636 g/m3。DOC（diesel oxidation catalyst）的催化劑負(fù)載量為883 g/m3，DOC與CDPF的貴金屬催化劑Pt與Pd的配比均為5∶1。測試設(shè)備主要有WE31水力測功機、FCM油耗儀、Testo 350氣體分析儀、AVL4000煙度計、PTQ-A20精密電子稱、溫度及壓力傳感等。

本文首先對發(fā)動機原機、發(fā)動機分別加裝DOC+DPF、DOC+CDPF1和DOC+CDPF2開展了外特性穩(wěn)態(tài)試驗，測試轉(zhuǎn)速范圍為1 200～3 000 r/min，每200 r/min測試1次。每個工況運行5 min，待柴油機運行穩(wěn)定后測量其動力性、經(jīng)濟性參數(shù)，并分別采集DOC+DPF、DOC+CDPF和DOC+CDPF2前后端的排氣溫度、排氣壓力及排放參數(shù)。在外特性試驗基礎(chǔ)上，進(jìn)一步開展噴油助燃主動再生試驗，測試載體溫度、積碳量、再生碳煙量等參數(shù)。

1. 噴射控制單元 2. 空氣泵 3. 單向閥 4. 油泵 5. 油箱 6. 電源 7. 電磁油量閥 8. 點火棒 9. 燃燒器 10. DPF和CDPF

1. Dosing control unit 2. Air pump 3. Check valve 4. Oil pump 5. Oil tank 6. Power supply 7. Electromagnetic oil valve 8. Ignition stick 9. Burner 10. DPF and CDPF

注：P1、P2為DPF/CDPF的前、后端壓力，kPa；T1、T2為DPF/CDPF的前、后端溫度，℃。

Note: P1 and P2 are the pressure of before and after DPF/CDPF, kPa; T1 and T2 are the temperature of before and afte DPF/CDPF, ℃.

圖1 柴油機臺架測試系統(tǒng)

Fig.1 Diesel engine bench test system

表1 D30TCI柴油機的主要技術(shù)參數(shù)

表2 DPF、CDPF1和CDPF2的具體參數(shù)

2 發(fā)動機外特性對比

發(fā)動機原機、加裝后處理器的外特性試驗結(jié)果見圖2。從圖2a可知，CDPF2在1 200 r/min時發(fā)動機動力下降12.2%，燃油消耗率增加12.3%，而CDPF1的影響則較小，這是由于CDPF2比CDPF1的催化劑負(fù)載量高，加大了載體的壓力損失，導(dǎo)致缸內(nèi)燃燒變差。因此，隨著轉(zhuǎn)速上升，CDPF1和CDPF2對動力性與經(jīng)濟性的影響均變小，3 000 r/min時對2者的影響均小于1%。由圖2b可知，由于CDPF1和CDPF2均比DPF的再生速率高，2者壓差變化不大，與DPF相比載體內(nèi)殘余碳煙量較少，因而最大排氣壓差比DPF低8.8 kPa。

圖2 發(fā)動機的外特性對比

根據(jù)圖2c可知，發(fā)動機在1 200 r/min時不透光煙度較高，而在1 600～3 000 r/min時由于原機的不透光煙度較小，排氣流經(jīng)DPF、CDPF1和CDPF2后，不透光煙度幾乎都小于1。如圖2d，原機排放的NO2通過DPF后參與了碳煙氧化，因此DPF后端的NO2體積分?jǐn)?shù)低于原機。由于前端DOC負(fù)載有較大量的貴金屬催化劑，這提高了NO催化氧化為NO2的表面反應(yīng)速率[4,9]，因而也為CDPF提供了充足的NO2組分。3 000 r/min時CDPF1前端的NO2體積分?jǐn)?shù)為81×10-6，后端較前端增加了33×10-6，而CDPF2后端則較前端增加了32×10-6。這說明在DOC與CDPF內(nèi)，在Pt、Pd雙金屬催化劑的作用下，NO與排氣O2的結(jié)合速率高于NO2解離產(chǎn)生活性氧與碳煙活性位的結(jié)合速率。由此可見，在外特性工況下，采取DOC+CDPF1的方案，既對發(fā)動機動力性與經(jīng)濟性影響較小，還能為CDPF1內(nèi)碳煙的再生提供充足的NO2組分，不必采用具有較高貴金屬負(fù)載量的CDPF2。

如圖2e，大部分外特性工況下，DPF后端溫度略低于前端，這是因為無催化劑時，柴油機的排溫難以達(dá)到碳煙的起燃溫度，且載體存在傳熱失所導(dǎo)致。1 200與1 400 r/min時，CDPF1和CDPF2的后端溫度均低于前端，而在1 600～3 000 r/min時，后端溫度略高于前端，這是由于在此轉(zhuǎn)速范圍時，雖然載體前端的排溫（約為498～520 ℃）已達(dá)到了碳煙的催化起燃溫度（約為450 ℃）[19]，但載體內(nèi)積累的碳煙量較少，導(dǎo)致放熱量較低。

3 噴油助燃主動再生特性試驗

3.1 噴油助燃主動再生試驗方案

課題組自主開發(fā)了一套噴油助燃主動再生燃燒系統(tǒng)，該系統(tǒng)主要由油箱、油泵、電磁油量閥、二次空氣泵、燃燒器、線束及噴射控制單元DCU（dosing control unit）、電瓶等組成，如圖3所示。試驗方案主要由2部分組成，第一部分試驗在燃燒試驗臺上進(jìn)行，試驗前將DPF和CDPF1分別加裝到發(fā)動機排氣管路進(jìn)行碳煙加載，碳載量為6 g/L。DPF和CDPF1的再生時長均為1 500 s，通過DCU控制燃燒試驗溫度分別為550 、600 和630 ℃。為防止再生時載體內(nèi)的峰值溫度與熱應(yīng)力過高，采取在噴油結(jié)束后進(jìn)行持續(xù)供氣（稱為二次供氣，噴油助燃再生時供給的空氣稱為一次供氣）?；诙喂饬康拇笮∨c測試發(fā)動機排量相匹配的原則，采取4種不同的二次供氣方案。方案1為無二次供氣；方案2為二次供氣速率0.625 L/s，時長300 s；方案3為二次供氣速率0.625 L/s，時長600 s；方案4為二次供氣速率1.25 L/s、時長180 s，繼續(xù)供氣速率0.625 L/s，時長420 s。試驗前使用精密電子稱稱取新鮮件的質(zhì)量記為，積碳和再生結(jié)束后，從排氣管取下DPF和CDPF1，稱取積碳后的載體質(zhì)量記為1，稱取再生后的載體質(zhì)量記為2，即可得到積碳量和再生碳煙量。定義再生效率為，計算公式如式（1）。

第二部分試驗在發(fā)動機測試臺架上進(jìn)行，仍采取在排氣系統(tǒng)進(jìn)行碳加載，加載工況為1 200 r/min、100%負(fù)荷，積碳時長1 200 s，然后開展噴油助燃再生試驗。由于在用車輛的排放升級改造和非道路移動機械實現(xiàn)第四階段排放標(biāo)準(zhǔn)，均會采用停機噴油再生和怠速再生2種方式，因此，本文測試了這2種方案的再生特性。停機噴油主動再生即發(fā)動機停機，依靠主動再生系統(tǒng)二次供氣燃燒產(chǎn)生的高溫，氧化再生碳煙（簡稱停機再生）。發(fā)動機怠速工況再生即發(fā)動機處于怠速工況，依靠發(fā)動機排氣結(jié)合二次供氣，進(jìn)行噴油助燃主動再生（簡稱怠速再生）。停機再生和怠速再生后，對DPF、CDPF1和CDPF2進(jìn)行3 000 r/min、100%負(fù)荷工況下的再生效果評價。

1. 噴射控制單元 2. 空氣泵 3. 單向閥 4. 油泵 5. 油箱 6. 電源 7. 電磁油量閥 8. 點火棒 9. 燃燒器 10. DPF/CDPF

1. Dosing control unit 2. Air pump 3. Check valve 4. Oil pump 5. Oil tank 6. Power supply 7. Electromagnetic oil valve 8. Ignition stick 9. Burner 10. DPF/CDPF

a. 噴油助燃主動再生試驗裝置示意圖

a. Schematic diagram of fuel injection combustion active regeneration system

1. DPF和CDPF 2. 燃燒器 3. 旁通管 4. DCU 5. 熱電偶 6. 數(shù)顯儀表

1. DPF and CDPF 2. Burner 3. Bypass pipe 4. DCU 5. Thermocouples 6. Digital display meter

b. 噴油助燃主動再生試驗臺

b. Fuel injection combustion active regeneration test bench

圖3 噴油助燃主動再生試驗系統(tǒng)

Fig.3 Fuel injection combustion active regeneration testing system

3.2 測試結(jié)果與分析

圖4為不同再生溫度時DPF和CDPF1的主動再生效率及載體的最高溫度。分析圖4a可知，隨著再生溫度升高，DPF與CDPF1的再生效率都有所上升。DPF在550 ℃的再生效率僅為43.8%，630 ℃的再生效率達(dá)到84.3%。CDPF1在600 ℃時的再生效率為89.7%，而630 ℃的再生效率達(dá)到96.4%。CDPF1在3個溫度下的再生效率都較DPF高，這是由于在Pt、Pd雙金屬催化劑的作用下，不但提高了碳煙的起燃活性，還提升了O2的吸附量與遷移到碳煙表面的速率[20-22]。從圖4b可以看出，由于CDPF1內(nèi)的碳煙起燃溫度較低[23-25]，載體內(nèi)的溫度上升速率較快，但載體的最高溫度卻較DPF低。再生溫度為600 ℃時，CDPF1載體的最高溫度比DPF低約35 ℃，630 ℃時的最高溫比DPF低約31 ℃。由此可見，CDPF1不僅能提高再生效率，還能降低載體內(nèi)的最高溫度。

圖4 不同再生溫度時的再生效率及載體的最高溫度

圖5為不同二次供氣條件下DPF和CDPF1的再生效率及載體的最高溫度對比。分析圖5a可知，DPF采用二次供氣方案2比方案1的再生效率低2.8個百分點，而方案4比方案1低5.5個百分點。CDPF1采用方案2的再生效率為85.4%，比方案1的再生效率低4.3個百分點，而采用方案4的再生效率為83.2%，比方案1低6.5個百分點。分析圖5b可知，DPF和CDPF1采用方案4時，載體最高溫度降低幅度最大，DPF最高溫度降低約53 ℃，CDPF1降低約64℃。由此可見，先采用短時長、大流量的二次供氣，能加快載體的散熱速率，雖然初始階段溫度降低迅速，但O2組分的傳質(zhì)速率增加；繼而再采用較小流量、較長時長的二次供氣策略，確保了載體再生所需溫度，因此對再生效率的影響較小。所以采用方案4的二次供氣策略，CDPF1的再生效果較好，再生效率下降幅度較小，載體最高溫度降低幅度較大，這將有助于提高載體在實車應(yīng)用中的安全性與可靠性。

圖5 不同二次供氣方案的再生效率及載體的最高溫度

3.3 停機與怠速噴油再生試驗結(jié)果與分析

3.3.1 停機再生與怠速再生的溫度對比

圖6為停機與怠速再生時，載體的入口與出口排氣溫度。從圖6a可知，噴油助燃再生開始后，通過DCU控制燃油噴射，燃燒器點火燃燒，入口溫度迅速上升到600 ℃并持續(xù)保持480 s，DCU切斷燃油噴射，采用二次供氣方案4直到1 100 s再生結(jié)束。由于本文試驗用碳化硅載體的導(dǎo)熱系數(shù)較高，并且考慮到再生過程中載體的安全性，DPF碳載量為4.6 g/L，CDPF1和CDPF2的碳載量均為2.2 g/L。當(dāng)600 ℃的高溫燃?xì)膺M(jìn)入載體后，雖然會燃燒碳煙釋放熱量，但由于傳熱過程損失了部分熱能[26-28]，第600 s時CDPF1的出口溫度比入口溫度低約199 ℃。怠速再生時，由于具有較高溫度的發(fā)動機排氣進(jìn)入燃燒器，高溫廢氣與二次空氣配合，在載體內(nèi)會蓄積更多熱量的燃?xì)?，引發(fā)了碳煙的快速再生并釋放了更多的熱量。因此，怠速再生時載體出口溫度都較停機再生的高。此外，CDPF1較CDPF2將碳煙燃燒的速率快，因而其載體出口的溫升速率也較CDPF2上升迅速，CDPF1在600 s時出口溫度約為445 ℃，而CDPF2在750 s時才上升到相同溫度。

圖6 停機再生與怠速再生的載體入口與出口溫度

3.3.2 停機再生與怠速再生的碳煙量對比

圖7為停機再生與怠速再生時，DPF、CDPF1和CDPF2的2次積碳量及再生效率對比。從圖7可知，當(dāng)積碳溫度為427 ℃時，DPF第1次積碳量為19 g，停機再生效率為48.9%，經(jīng)過第2次積碳后進(jìn)行怠速主動再生的效率為73.3%。CDPF1和CDPF2的停機與怠速再生效率都較DPF高，CDPF1的停機再生效率為76.4%，而怠速再生效率增加到88.5%。CDPF2的2次再生效率較CDPF1低，其停機再生效率為71%，怠速再生效率為83.8%。通過以上分析可知，載體的怠速主動再生效率均高于停機再生，這是由于停機再生是冷態(tài)二次空氣進(jìn)入燃燒器，而怠速再生是將具有較高溫度的發(fā)動機廢氣引入燃燒器，在二次空氣的配合下，既提高了燃油在燃燒器內(nèi)的燃燒速率，同時高溫燃?xì)鈺愿斓乃俾嗜紵嗟奶紵?，從而提高了怠速主動再生的燃燒效率?；趪娪驮偕脑囼灲Y(jié)果，說明通過DCU控制燃燒器的溫度為600 ℃，采取方案4的二次供氣策略，能確保載體的安全可靠再生，使用貴金屬負(fù)載量較低的CDPF1，在停機與怠速再生時，都能具有較高的再生效率。

3.3.3 停機再生與怠速再生后壓差與溫度的評價對比

圖8是開展停機再生和怠速再生結(jié)束后，在3 000 r/min、100%負(fù)荷工況下DPF、CDPF1和CDPF2的壓差對比。結(jié)合圖6～8可知，由于更多的高溫燃?xì)猱a(chǎn)生了較高的再生效率，怠速再生后載體內(nèi)殘余的碳煙量更少，因而怠速再生后的壓差都較停機再生低。DPF停機再生后的壓差在32 kPa上下波動，怠速再生后壓差下降到28 kPa左右。CDPF1停機再生后的壓差約為27 kPa，怠速再生后的最終壓差降低到25 kPa。CDPF2停機再生后最終壓差約為24.5 kPa，怠速再生后的壓差下降到22 kPa。

圖7 停機再生與怠速再生效果

圖8 停機再生和怠速再生后的壓差對比

圖9為停機再生和怠速再生后，在3 000 r/min、100%負(fù)荷工況下，DPF、CDPF1和CDPF2的溫度對比。在初始時刻，停機再生后CDPF1的入口溫度為466 ℃，CDPF2的溫度為405 ℃，怠速再生后CDPF1入口溫度上升到469 ℃，CDPF2的則增加到441 ℃，DPF也具有同樣的變化規(guī)律。這是由于怠速再生后載體的排氣壓差較小，引起發(fā)動機缸內(nèi)燃燒壓力和燃燒溫度增加[29]，排氣溫度上升，因此怠速再生后載體入口端的溫度較高，但入口溫度都達(dá)到了碳煙被動再生的起燃溫度。由此說明，采取催化型CDPF進(jìn)行主、被動相結(jié)合的再生方式，能將2者的優(yōu)點進(jìn)行相互融合，在未來的研究中，通過進(jìn)一步優(yōu)化催化負(fù)載量、再生時機，同時結(jié)合排氣熱管理等技術(shù)[30]，將有助于形成基于催化條件下的主動再生策略。

圖9 停機再生和怠速再生后的溫度對比

4 結(jié) 論

1）外特性試驗中，采用催化劑負(fù)載量為530 g/m3的CDPF，在Pt、Pd雙金屬催化劑的作用下，能為被動再生提供充足的NO2組分，因此，CDPF的最大排氣壓差比DPF低8.8 kPa。加裝CDPF對發(fā)動機的動力性與經(jīng)濟性影響較小，3 000 r/min時對動力性與經(jīng)濟性的影響均小于1%。

2）基于自主開發(fā)的主動再生燃燒系統(tǒng)，開展噴油助燃再生燃燒試驗。通過ECU控制燃燒溫度為600 ℃，采取4種不同的二次供氣方案，催化劑負(fù)載量為530 g/m3的CDPF，采用二次供氣速率1.25 L/s、時長180 s，繼續(xù)供氣速率0.625 L/s、時長420 s的方案時，再生效率達(dá)到83.2%，比無二次供氣時載體的最高溫度降低了64 ℃。說明采用上述二次供氣方案再生效果較好，這將有助于實現(xiàn)載體在實車應(yīng)用中進(jìn)行安全、可靠的高效率再生。

3）在停機與怠速再生試驗中，采取二次供氣速率1.25 L/s、時長180 s，繼續(xù)供氣速率0.625 L/s、時長420 s的方案，再生時長為1 100 s。試驗結(jié)果表明，催化劑負(fù)載量為530 g/m3的CDPF具有較好的再生效果，其停機再生效率為76.4%，怠速再生效率達(dá)到88.5%。

未來的研究可通過進(jìn)一步優(yōu)化催化負(fù)載量、再生時機，同時結(jié)合排氣熱管理等技術(shù)，形成基于催化條件下的主動再生策略，為在用車輛的排放升級改造及非道路移動機械實現(xiàn)第四階段排放標(biāo)準(zhǔn)提供參考。

[1] 譚丕強，王德源，樓狄明，等.農(nóng)業(yè)機械污染排放控制技術(shù)的現(xiàn)狀與展望[J]. 農(nóng)業(yè)工程學(xué)報，2018，34(7)：1－14. Tan Piqiang, Wang Deyuan, Lou Diming, et al. Progress of control technologies on exhaust emissions for agricultural machinery[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2018, 34(7): 1－14.(in Chinese with English abstract)

[2] Fu Mingliang, Ge Yunshan, Tan Jianwei, et al.Characteristics of typical non-road machinery emissions in China by using portable emission measurement system[J]. Science of the Total Environment, 2012 , 437(20): 255－261.

[3] Bai Shuzhan, Chen Guobin, Sun Qiang, et al. Influence of active control strategies on exhaust thermal management for diesel particular filter active regeneration[J]. Applied Thermal Engineering, 2017(119): 297－303.

[4] 黃河，孫平，劉軍恒，等. 納米CeO2催化劑對柴油機碳煙顆粒和NO降低效果[J]. 農(nóng)業(yè)工程學(xué)報，2017，33(2)：54－59. Huang He, Sun Ping, Liu Junheng, et al. Reducing soot and NO emission from diesel engine exhaust catalyzed by nano- CeO2[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2017, 33(2): 54－59. (in Chinese with English abstract)

[5] Kazuhiro Yamamoto, Tatsuya Sakai. Simulation of continuously regenerating trap with catalyzed DPF[J].Catalysis Today, 2015(242): 357－362.

[6] Bai Shuzhan, Tang Jiao, Wang Guihua, et al. Soot loading estimation model and passive regeneration characteristics of DPF system for heavy-duty engine[J]. Applied Thermal Engineering, 2016(100): 1292－1298.

[7] E Jiaqiang, Zuo Wei, Gao Junxu, et al. Effect analysis on pressure drop of the continuous regeneration-diesel particulate filter based on NO2assisted regeneration[J]. Applied Thermal Engineering, 2016(100): 356－366.

[8] Dieter Rothe, Markus Knauer, Gerhard Emmerling, et al. Emissions during active regeneration of a diesel particulate filter on a heavy duty diesel engine: Stationary tests[J]. Journal of Aerosol Science, 2015(90): 14－25.

[9] Chen Pingen, Wang Junmin. Air-fraction modeling for simultaneous Diesel engine NOx and PM emissions control during active DPF regenerations[J]. Applied Energy, 2014, 122(5): 310－320.

[10] Deng Yuanwang, Zheng Wenping, E Jiaqiang, et al. Influence of geometric characteristics of a diesel particulate filter on its behavior in equilibrium state[J]. Applied Thermal Engineering, 2017(123) :61－73.

[11] 伏軍，龔金科，左青松，等. 微粒捕集器噴油助燃再生噴油與補氣的優(yōu)化控制[J]. 農(nóng)業(yè)工程學(xué)報，2012，28(17)： 11－18. Fu Jun, Gong Jinke, Zuo Qingsong, et a1. Optimum control of fuel injection and air supply for burner-type diesel particulate filter regeneration[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2012, 28(17): 11－18. (in Chinese with English abstract)

[12] Hiroyuki Yamada, Satoshi Inomat, Hiroshi Tanimoto. Mechanisms of increased particle and VOC emissions during DPF active regeneration and practical emissions considering regeneration[J]. Environmental Science & Technology, 2017, 51(5): 2914－2923.

[13] 王建，曹政，張多軍，等. 基于DPF主動再生溫度需求的柴油機進(jìn)氣節(jié)流控制策略[J]. 農(nóng)業(yè)工程學(xué)報，2018，34(2)：32－37. Wang Jian, Cao Zheng, Zhang Duojun, et al.Intake throttling control strategy based on DPF active regeneration temperature for diesel[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2018, 34(2): 32－37.(in Chinese with English abstract)

[14] Waldemar Karsten, Martina Goy, Heide Vom Schloss, et al. Diesel burner for particle filter regeneration at mobile machinery[J]. Mtz Worldwide, 2013, 74 (7/8): 18－22.

[15] Eric Hein, Adam Kotrba, Tobias Inclan, et al. Secondary fuel injection characterization of a diesel vaporizer for active DPF regeneration[J]. SAE Int. J. Engines, 2014, 7(3): 1228－1234.

[16] Chen Pingen, Umar Ibrahim, Wang Junmin. Experimental investigation of diesel and biodiesel post injections during active diesel particulate filter regenerations[J]. Fuel, 2014, 130(7): 286－295.

[17] Meng Zhongwei, Zhang Jing, Chen Chao, et al. A numerical investigation of the diesel particle filter regeneration process under temperature pulse conditions[J]. Heat and Mass Transfer, 2017, 53(5): 1589－1602.

[18] Kuwahara T, Nishii S, Kuroki T, et al. Complete regeneration characteristics of diesel particulate filter using ozone injection[J].Applied Energy, 2013, 111(11): 652－656.

[19] Keld Johansen. Multi-catalytic soot filtration in automotive and marine applications[J].Catalysis Today, 2015(258): 2－10.

[20] Herreros J M, Gill S S, Lefort I, et al.Enhancing the low temperature oxidation performance over a Pt and a Pt–Pd diesel oxidation catalyst[J].Applied Catalysis B Environmental, 2014 , 147(7): 835－841.

[21] Verónica Rico Pérez, Agustín Bueno-López. Catalytic regeneration of diesel particulate filters: Comparison of Pt and CePr active phases[J]. Chemical Engineering Journal, 2015(279): 79－85.

[22] Zdeněk Vít, Daniela Gulková, Luděk Kalu?, et al. Effect of catalyst precursor and its pretreatment on the amount of-Pd hydride phase and HDS activity of Pd-Pt/silica-alumina[J]. Applied Catalysis B: Environmental, 2014(146): 213－220.

[23] Zhou Qiuhong, Zhong Kunhua, Fu Weiling, et al. Nanostructured platinum catalyst coating on diesel particulate filter with a low-cost electroless deposition approach[J]. Chemical Engineering Journal, 2015(270): 320－326.

[24] Qi Guolu, Zhang Yexin, Chen Aibing, et al. Potassium- activated wire mesh: A stable monolithic catalyst for diesel soot combustion[J]. Chemical Engineering & Technology, 2016, 40(1): 50－54.

[25] Valeria Di Sarli, Gianluca Landi, Luciana Lisi, et al. Catalytic diesel particulate filters with highly dispersed ceria: Effect of the soot-catalyst contact on the regeneration performance[J]. Applied Catalysis B Environmental, 2016(197): 116－124.

[26] Galindo J, Serrano J R, Piqueras P, et al. Heat transfer modelling in honeycomb wall-flow diesel particulate filters [J]. Energy, 2012, 43(1): 201－213.

[27] Nepal C Roy, Akter Hossain, Yuji Nakamura. A universal model of opposed flow combustion of solid fuel over an inert porous medium[J]. Combustion & Flame, 2014, 161(6): 1645－1658.

[28] Chen Tao, Wu Zhixin, Gong Jinke, et al. Numerical simulation of diesel particulate filter regeneration considering ash deposit[J]. Flow Turbulence Combust, 2016, 97(3): 1－16.

[29] Yu Mengting, Dan Luss, Vemuri Balakotaiah. Analysis of flow distribution and heat transfer in a diesel particulate filter[J]. Chemical Engineering Journal, 2013, 226(24): 68－78.

[30] Eid S Mohamed. Experimental study on the effect of active engine thermal management on a bi-fuel engine performance, combustion and exhaust emissions[J]. Applied Thermal Engineering, 2016(106): 1352－1365.

Bench test of regeneration characteristics of catalyzed diesel particulate filter based on fuel injection combustion system

Zhang Wei, Chen Zhaohui※, Kong Mengxi, Zhao Luofeng, Bao Guangyuan

(650500,)

In order to provide technical references for upgrading emissions of existing vehicles, to meet the four-stage emission limitation requirements of non-road mobile machineries, based on the self-developed fuel injection combustion active regeneration system, the external characteristic tests of diesel engine with diesel particulate filter(DPF) and the active regeneration combustion tests were carried out in this paper. The results showed that the catalyzed diesel particulate filter (CDPF) with 530 g/m3catalysts loading, name as CDPF1, has little effect on the power and economy performances of the engine under external characteristic conditions. At 3 000 r/min, the volume fraction of NO2is 81×10-6at front end of CDPF1, while it is increased by 33×10-6at rear end of that. This indicates that with the action of Pt and Pd bimetallic catalysts, the binding rate of NO to exhaust O2is higher than the rate of active oxygen dissociated from NO2binding to the soot active sites. Adequate NO2content promotes regeneration efficient of soot in the CDPF, therefore the maximum exhaust pressure difference of CDPF1 was 8.8 kPa which lower than that of DPF. On the basis of external characteristic tests, the active regeneration tests of fuel injection combustion was further carried out. The first part of the regeneration tests were carried on the combustion test bench, the combustion temperatures were controlled by dosing control unit (DCU) to be 550, 600 and 630 ℃, respectively. In order to prevent the peak temperature and thermal stress in the carrier from being too high during regeneration, secondary gas supply was carried out after fuel injection. Based on the principle that the amount of the secondary gas supply matches with displacement of the test engine, 4 different secondary gas supply schemes were adopted. The experimental results showed that when the regeneration temperature was 630 ℃, the regeneration efficiency of CDPF1 reached 96.4% in the absence of secondary gas supply, however, the regeneration efficiency of DPF was only 84.3%. In addition, the maximum temperature of CDPF1 carrier was also lower than that of DPF during regeneration, and the highest temperature of CDPF1 was about 31 ℃which lower than that of DPF at 630 ℃. It can be seen that CDPF1 could not only improve the regeneration efficiency, but also reduce the maximum temperature in the carrier. When regeneration temperature was 600 ℃, the secondary gas supply scheme 4 was adopted, i.e. the secondary gas supply rate was 1.25 L/s for 180 s, then the gas supply rate was 0.625 L/s for 420 s, and the regeneration efficiency of CDPF1 was 83.2%, the maximum temperature was reduced by about 64 ℃ compared to the absence of secondary gas supply. The second part of regeneration tests were carried out on engine test bench, and the regeneration temperature was still 600 ℃. The regeneration characteristics of DPF, CDPF1, CDPF2 and the CDPF2 with 636 g/m3catalysts loading were tested under engine stop and idle speed regeneration conditions. The test results showed that CDPF1 had a good regeneration performance, with regeneration efficiency was 76.4% for engine stop regeneration, the idle regeneration efficiency was increased to 88.5%. This was because that the secondary air into the combustion chamber was cold for engine stop regeneration, and the engine exhaust with higher temperature was introduced into the burner for the idle regeneration, the secondary air was combined to improve the burning rate of the fuel in the burner, at the same time, high temperature gas would burn more soot at a faster rate, and the combustion efficiency of the idle condition regeneration was improved. The pressure difference of DPF, CDPF1 and CDPF2 was tesed under 3 000 r/min speed and 100% load conditions. Since the amount of residual soot in the carrier was less after the idle regeneration, the pressure difference of DPF, CDPF1 and CDPF2 after idle regeneration were lower than that of engine stop regeneration. The pressure difference of CDPF1 was about 27 kPa after engine stop regeneration, and the final pressure difference was reduced to 25 kPa after idle regeneration. This study showed that the combination of active and passive regeneration of catalytic CDPF can integrate the advantages of the both, in future research, the active regeneration strategy based on catalytic conditions can be formed by further optimizing the catalytic load and regeneration timing, combining with exhaust heat management technology, and provide a reference for the upgrading and transformation of exhaust emissions of vehicles in use and the realization of the fourth stage emission standards of non-road mobile machinery.

diesel engine; combustion; catalysts; regeneration; DPF; CDPF; fuel injection assisted combustion; bench test

2018-10-06

2019-01-18

國家自然科學(xué)基金資助項目（51666007；51665023）

張韋，博士，教授，主要從事內(nèi)燃機燃燒與排放控制研究，Email：koko_575@aliyun.com

陳朝輝，博士，副教授，主要從事內(nèi)燃機燃燒與排放控制研究。Email：chenzhaohuiok@sina.com

10.11975/j.issn.1002-6819.2019.08.011

TK411+.5

A

1002-6819(2019)-08-0092-08

張 韋，陳朝輝，孔孟茜，趙羅峰，包廣元. 柴油機催化型顆粒捕集器噴油助燃再生特征[J]. 農(nóng)業(yè)工程學(xué)報，2019，35(8)：92－99. doi：10.11975/j.issn.1002-6819.2019.08.011 http://www.tcsae.org

Zhang Wei, Chen Zhaohui, Kong Mengxi, Zhao Luofeng, Bao Guangyuan. Bench test of regeneration characteristics of catalyzed diesel particulate filter based on fuel injection combustion system[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2019, 35(8): 92－99. (in Chinese with English abstract) doi：10.11975/j.issn.1002-6819.2019.08.011 http://www.tcsae.org