DME/甲醇组合燃料HCCI燃烧和排放特性的试验研究
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摘要
随着能源和环境问题的日益严峻,人们越来越重视非石油基的代用燃料开发。二甲醚(DME)和甲醇都是含氧的清洁燃料,其来源广泛,有优越的燃烧和排放性能,被认为是最有发展前景的两种发动机代用燃料。
均质充量压缩燃烧(HCCI)相比传统的燃烧方式,具有潜在的更低的NOX排放性能和更高的热效率。但HCCI燃烧受失火和爆震的限制,稳定运行的工况负荷范围较窄,且着火点难以精确控制。采用调节不同着火性质的燃料混合比来控制HCCI的着火过程是一个行之有效的方法。基于这一学术思想,本文采用DME/甲醇双燃料组合燃烧的方法来控制HCCI的着火,拓宽HCCI的工况范围。
本文以ZS195直喷式柴油机为原型机,将其改造为双燃料进气道喷射发动机,并自行研发了一套甲醇电控喷油装置,搭建了DME/甲醇双燃料HCCI燃烧的专用试验台架。通过调节甲醇、DME的喷油量和采取进气加温措施,解决了进气道喷射的甲醇难以全部蒸发气化的问题,实现了HCCI发动机不同燃料混合比均质混合气的制备。在此基础上,开展了不同DME/甲醇燃料混合比、不同进气温度下,变转速和变负荷工况DME/甲醇组合燃料HCCI发动机燃烧性能和常规排放特性的试验,并利用气相色谱和傅里叶红外光谱分析技术对其非常规排放物,如甲醛、乙醛、甲醇、甲酸甲酯等进行了检测分析。为了加深对DME/甲醇双燃料HCCI燃烧特性的理解,利用自编的DME/甲醇组合燃料HCCI发动机的放热率计算程序,对试验结果进行了计算分析。
研究结果表明,采用DME/甲醇组合燃烧的方式可以有效拓宽HCCI的工况范围,随着甲醇喷油量的增加,发动机的最大输出功率增大,HC、CO的排放增加,NOX的排放减少,甲醛、乙醛、甲醇、甲酸甲酯和DME的排放都有所增加;随着发动机负荷的增加,HC、CO的排放降低,NOX的排放略微增加,甲醛的排放增加,乙醛、甲醇、和DME的排放减少,甲酸甲酯的排放先减少后增加;随着进气温度的提高,HC和CO的排放降低,NO_X和甲醛的排放增加,乙醛、甲醇、甲酸甲酯和DME的排放均降低。
With ever growing concerns on energy crises and environmental issues, people pay more attention to seek non-petroleum based alternative fuels. As clean and oxygen-containing fuels, both DME (dimethyl ether) and methanol have been considered to be the most promising alternative fuels due to the broad resources of its feed stocks and excellent performance of economics and emissions.
Compared with conventional combustion mode, Homogeneous charge compression ignition (HCCI) combustion enables lower NO_X emissions and higher thermal efficiency. However, the operating range in the HCCI engine is limited to low load because of misfiring and knocking, and it is hard to control the ignition timing. Adjusting the proportion of two fuels with different ignition properties is an effective technique for controlling ignition timing in HCCI combustion. In this paper, a method to control the ignition timing and expand the operating range of HCCI engine by fueling with dimethyl ether (DME) and methanol dual fuel has been proposed.
The test bed of DME/methanol dual fueled HCCI engine is modified and established on a ZS195 prototype diesel engine. By adjusting the amount of DME/methanol supply and the intake temperature, the experimental study on engine’s performance of combustion and exhaust emissions were carried out. With the use of Gas Chromatography (GC) and Fourier Transform Infrared Spectrometry (FTIR), some unregulated emissions such as formaldehyde, acetaldehyde, methanol, methyl formate from the DME/methanol duel fueled HCCI engine are specially analyzed.
The result shows that the operating region of HCCI engine can be extended effectively with DME/methanol dual fueled mode. With the increase of methanol, the peak power output of the engine, the formaldehyde, acetaldehyde, methanol, methyl formate and DME emissions and the HC and CO emissions are increased, while the NO_X emissions are reduced. And with the increase of engine load, the acetaldehyde, methanol and DME emissions and the HC and CO emissions are reduced while the NO_X emissions are increased slightly, the methyl formate emissions are declined first and then climbed up. When the intake air temperature is increased, emissions of the acetaldehyde, methanol, methyl formate, DME, HC and CO are reduced. However, the NO_X emissions and formaldehyde emissions are increased.
均质充量压缩燃烧(HCCI)相比传统的燃烧方式,具有潜在的更低的NOX排放性能和更高的热效率。但HCCI燃烧受失火和爆震的限制,稳定运行的工况负荷范围较窄,且着火点难以精确控制。采用调节不同着火性质的燃料混合比来控制HCCI的着火过程是一个行之有效的方法。基于这一学术思想,本文采用DME/甲醇双燃料组合燃烧的方法来控制HCCI的着火,拓宽HCCI的工况范围。
本文以ZS195直喷式柴油机为原型机,将其改造为双燃料进气道喷射发动机,并自行研发了一套甲醇电控喷油装置,搭建了DME/甲醇双燃料HCCI燃烧的专用试验台架。通过调节甲醇、DME的喷油量和采取进气加温措施,解决了进气道喷射的甲醇难以全部蒸发气化的问题,实现了HCCI发动机不同燃料混合比均质混合气的制备。在此基础上,开展了不同DME/甲醇燃料混合比、不同进气温度下,变转速和变负荷工况DME/甲醇组合燃料HCCI发动机燃烧性能和常规排放特性的试验,并利用气相色谱和傅里叶红外光谱分析技术对其非常规排放物,如甲醛、乙醛、甲醇、甲酸甲酯等进行了检测分析。为了加深对DME/甲醇双燃料HCCI燃烧特性的理解,利用自编的DME/甲醇组合燃料HCCI发动机的放热率计算程序,对试验结果进行了计算分析。
研究结果表明,采用DME/甲醇组合燃烧的方式可以有效拓宽HCCI的工况范围,随着甲醇喷油量的增加,发动机的最大输出功率增大,HC、CO的排放增加,NOX的排放减少,甲醛、乙醛、甲醇、甲酸甲酯和DME的排放都有所增加;随着发动机负荷的增加,HC、CO的排放降低,NOX的排放略微增加,甲醛的排放增加,乙醛、甲醇、和DME的排放减少,甲酸甲酯的排放先减少后增加;随着进气温度的提高,HC和CO的排放降低,NO_X和甲醛的排放增加,乙醛、甲醇、甲酸甲酯和DME的排放均降低。
With ever growing concerns on energy crises and environmental issues, people pay more attention to seek non-petroleum based alternative fuels. As clean and oxygen-containing fuels, both DME (dimethyl ether) and methanol have been considered to be the most promising alternative fuels due to the broad resources of its feed stocks and excellent performance of economics and emissions.
Compared with conventional combustion mode, Homogeneous charge compression ignition (HCCI) combustion enables lower NO_X emissions and higher thermal efficiency. However, the operating range in the HCCI engine is limited to low load because of misfiring and knocking, and it is hard to control the ignition timing. Adjusting the proportion of two fuels with different ignition properties is an effective technique for controlling ignition timing in HCCI combustion. In this paper, a method to control the ignition timing and expand the operating range of HCCI engine by fueling with dimethyl ether (DME) and methanol dual fuel has been proposed.
The test bed of DME/methanol dual fueled HCCI engine is modified and established on a ZS195 prototype diesel engine. By adjusting the amount of DME/methanol supply and the intake temperature, the experimental study on engine’s performance of combustion and exhaust emissions were carried out. With the use of Gas Chromatography (GC) and Fourier Transform Infrared Spectrometry (FTIR), some unregulated emissions such as formaldehyde, acetaldehyde, methanol, methyl formate from the DME/methanol duel fueled HCCI engine are specially analyzed.
The result shows that the operating region of HCCI engine can be extended effectively with DME/methanol dual fueled mode. With the increase of methanol, the peak power output of the engine, the formaldehyde, acetaldehyde, methanol, methyl formate and DME emissions and the HC and CO emissions are increased, while the NO_X emissions are reduced. And with the increase of engine load, the acetaldehyde, methanol and DME emissions and the HC and CO emissions are reduced while the NO_X emissions are increased slightly, the methyl formate emissions are declined first and then climbed up. When the intake air temperature is increased, emissions of the acetaldehyde, methanol, methyl formate, DME, HC and CO are reduced. However, the NO_X emissions and formaldehyde emissions are increased.
引文
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[5]王丹,朱向荣.车用代用燃料研究及发展趋势.汽车工艺与材料. 2005(10): 1-5.
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[10] S.G.Poulopoulos, D.P.Samaras, C.J.Philippopoulos. Regulated and unregulated emissions from an internal combustion engine operating on ethanol-containing fuels. Atmospheric Environment, 2001,35,4399-4406.
[11] Chunlan Mo, Haiying Sun, Shaoren Zhou. Study on formaldehyde emission in a DME-fueled, direct-injection diesel engine. SAE Paper 01-1909,2007.
[12] Troy A. Semelsberger, Rodney L. Borup, Howard L. Greene. Dimethyl ether (DME) as an alternative fuel. Journal of Power Sources 156(2006):497-511
[13] Constantine Arcoumanis, Choongsik Bae, Roy Crookes,et.al. The potential of di-methyl ether (DME) as an alternative fuel for compression-ignition engines: A review. Fuel,87(2008),1014-1030.
[14]杨逸民,陈运根.发展煤基醇醚燃料势在必行.农业工程学报,2006,22(supp1).
[15]刘海峰,张全长,黄华.甲醇和二甲醚燃料在发动机中的应用现状.节能,2006(4):13-16.
[16]饶四平.柴油机燃用乙醇/柴油混合燃料的性能与排放特性研究[D].华中科技大学,2008.6.
[17]郑尊清,尧命发,许斯都,等.柴油机燃用二甲基醚的现状和发展.小型内燃机,1998, 27(5):12-16.
[18]黄震,乔信起,张武高,等.二甲醚发动机与汽车研究.内燃机学报,2008, 26:115-125.
[19]王谦,吴小勇.均质充量压缩燃烧发动机的特点与研究现状.华东船舶工业研究院学报(自然科学版),2005(3): 75-79.
[20]郑尊清,朱坚,尧命发,等.二甲醚/甲醇均质压燃的燃烧特性[J].天津大学学报.2006,39(1):63-67.
[21] Wanhua Su, Tiejian Lin, Yiqiang Pei. A Compound Technology for HCCI Combustion in a DI Diesel Engine Based on the Multi-Pulse Injection and the BUMP Combustion Chamber[C]. SAE Paper 2003-01-0741.
[22] Toshio Shudo, Yoshitaka Ono. Hcci Combustion of Hydrogen, Carbon Monoxide and Dimethyl Ether. SAE Paper 2002, 01-0112.
[23] Green C J, Cockshutt N A, King L. Dimethyl ether as an ignition improver[C]. SAE Paper 922212,1992.
[24] Green Chris J, Cockshutt Neal A. Dimethyl ether as a methanol ignition improver-- Substitution requirements and exhaust emissions impact. SAE Paper 902155, 1990.
[25] Murayama Tadashi,Chikahisa Takemi,Guo Jianwei,et al. A study of a compression ignition methanol engine with converted dimethyl ether as an ignition improver. SAE Paper 922212,1992.
[26] Michael E.Karpuk, John D.Wright, James L.Dippo, et al. Dimethyl Ether as An Ignition Enhancer for Methanol-Fueled Diesel Engines. SAE Paper 912420,1991.
[27] Hiroyuki,Y, Masataka, Y, Atsumu,T.Chemical mechanistic analysis of additive effects in homogeneous charge compression ignition of dimethyl ether. Proceedings of the Combustion Institute, Thirtieth International Symposium on Combustion, 2005, 30(2): 2773-2780.
[28] Yamada,Hiroyuki, Tono,Manabu, Tezaki,Atsumu. Validation of retarding mechanism in ignition timing of HCCI engine by adding methanol to DME. Transactions of the Japan Society of Mechanical Engineers Part B,(Japan),2004,16(9):2455-2461.
[29] Hideyuki Ogawa, Noboru Miyamoto, Naoya Kaneko,et.al. Combustion control and operating range expansion with direct injection of reaction suppressors in a premixed DME HCCI engine. SAE Paper 2003-01-0746.
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