共查询到19条相似文献,搜索用时 187 毫秒
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对置活塞二冲程缸内直喷汽油机混合气形成的数值研究 总被引:1,自引:0,他引:1
针对对置活塞二冲程汽油机缸径小、冲程长的特点,利用三维CFD软件AVL-Fire对缸内喷雾方向进行优化,实现全负荷工况下(6 000r/min)的缸内混合气均匀混合;并且基于优选的喷雾方向,研究部分负荷工况下(2 000r/min)二次喷射策略(不同喷油时刻和喷油比例)对缸内混合气分层分布的影响。结果显示,增大排气侧3束喷雾的中心线与气缸中心面夹角β会导致燃油蒸发率降低,而增大进气侧3束喷雾的中心线与气缸中心面夹角α有利于提高缸内混合气的均匀度;在部分负荷时,当第一次喷油时刻为内止点前140°曲轴转角,第二次喷射时刻为内止点前60°曲轴转角,第二次喷油量为总喷油量的33%时,缸内形成理想的混合气分层分布。 相似文献
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《汽车安全与节能学报》2014,(3)
试验研究了缸内直喷(GDI)汽油机的负荷、过量空气系数、点火时刻等参数对于三效催化器(TWC)后的颗粒(PM)排放特性的影响。试验在在2台GDI汽油机上进行,用气相质谱-色谱(GC-MS)联用方法,分析了TWC后微粒中可溶有机成分(SOF)。结果表明:随着负荷增加,微粒质量和数量排放增加,在满负荷工况下,微粒排放大幅增加;TWC后的SOF和核态微粒数量明显降低;随着过量空气系数的增加和点火时刻的推迟,微粒排放呈减少趋势;核态粒径峰值为10~20 nm,积聚态粒径峰值为50~70 nm。负荷、过量空气系数和点火提前角等参数和TWC对微粒粒径范围的影响小。 相似文献
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DISI甲醇发动机分层稀薄燃烧试验研究 总被引:1,自引:0,他引:1
研究了直喷火花塞点燃式(DISI)甲醇发动机1600 r/min和1200 r/min转速下整个负荷工况内分层稀薄燃烧对性能、燃烧及排放的影响。结果表明:DISI甲醇发动机在整个负荷工况内的一系列特征与柴油机和汽油机有很大不同,缸内混合气分层质量及燃油缸内空间分布对不同转速下的燃烧特性有显著影响;1200 r/min时热效率大、运转稳定,燃烧前期缸压和放热率优于1600 r/min时;大负荷时DISI甲醇发动机分层稀薄燃烧的经济性和排放性都比较好,但小负荷时的经济性和排放性较差,有待改善。 相似文献
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进气门晚关机构对高增压柴油机排放与热效率的影响 总被引:1,自引:0,他引:1
以某重型柴油机为研究对象,在低速中等负荷工况,通过对比进气门晚关机构开闭两种状态对两级增压系统匹配关系的影响,分析其对柴油机排放和热效率的影响。研究表明,喷油定时(上止点后-2.5°~8.5°)和EGR率(0%~21%)恒定时,使用进气门晚关(IVCA)机构后HC排放降低,有效热效率下降。当喷油定时不变,BNOxdif与BCOdif随着EGR率的增加而减少;当EGR率保持恒定时,随着喷油定时增加,BCOdif呈现先增加后减小的趋势,拐点在4.5°~6.5°(ATDC)之间;同时,开启IVCA机构后,EGR率在15.29%~21.16%,喷油定时在-2.5°~8.5°(ATDC)范围内,Bsootdif均小于0。在保证喷油定时恒定时,EGR率越大,Bsootdif越小。当量比在0.42~0.52范围内,保持喷油策略不变,使用IVCA机构致使进气流量减少,若当量比在原状态的基础上增加超过0.07,即可克服由于流量减少导致柴油机缸内平均温度和燃烧持续期增加对NOx生成的负面影响。 相似文献
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纳米燃油添加剂对柴油机颗粒物排放特性的影响 总被引:1,自引:0,他引:1
在186FA柴油机上对质量分数为50mg/kg和100mg/kg的CeO2或Co3O4纳米颗粒-柴油混合燃料进行颗粒物排放特性台架试验,采用扫描电镜和热重分析仪对采集到的颗粒物样品进行微观结构形貌及热重特性分析。结果表明:纳米CeO2和Co3O4颗粒均可改善柴油机颗粒物排放,与0号柴油相比,混合燃料颗粒物比排放量下降16.4%~35.9%;混合燃料颗粒物排放的粒径分布仍呈单峰分布的特点,峰值均在0.56~1.0μm区间内,微观形态下的粒径和孔隙率明显变小,团聚程度提高;混合燃料燃烧过程中颗粒物发生氧化反应的起燃温度、失重率峰值温度及燃尽温度均有所降低,最大失重率明显增加。 相似文献
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Bin Yang Wu Qiang Zhan Shun Kai Zhang Xiao Kun Nie Yu Han Li Wanhua Su 《International Journal of Automotive Technology》2018,19(4):623-633
Experiments and simulations were used to investigate the effect of a range of engine operating parameters and fuel characteristics on the particle size and particle number (PN) concentration at low speed and idle speed condition. The occurrence, size, and concentration of particles were tested against a range of parameters including start of injection (SOI), common rail pressure, exhaust gas recirculation (EGR) ratio and load. The results showed that the homogeneity of the mixture had the greatest impact on particle size and number concentration. The performance of particle is different at different levels of load. The particle were of nucleation mode at idle condition, and the cold idle particles had a slightly larger diameter than those produced at hot idle. By using the diesel and under high load, at EGR ratios of less than 20 %, most particles were of nucleation mode. At EGR ratios exceeding 20 %, nucleation-mode particles were gradually replaced by accumulation-mode particles. At EGR ratios above 30 %, most particles were of the accumulation mode. Under the same load, gasoline compression ignition produced particles of smaller size and reduced particulate mass (PM). The use of gasoline extended ignition delay, as the high volatility and octane number of the fuel improved the homogeneity of the mixture. Finally, a linear relationship was found between PM and PN. The relative contribution of the different factors to the formation of nucleationor accumulation-mode particles was investigated. 相似文献
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为了提高某增压汽油机的性能,将其压缩比提高到11.5,并加装一套EGR循环系统。通过台架试验,在低速小负荷和中速中负荷工况下,研究了理论空燃比下废气再循环率对改造后汽油机性能的影响。结果表明:当EGR率小于20%时,采用合适的EGR率配合优化的点火时刻,可以使该发动机燃烧稳定,在保证发动机动力性的同时,指示热效率随着EGR率的增加不断升高;与无EGR时相比,EGR率为20%时,有效燃油消耗率在低速小负荷工况下降低了约4.5%,中速中负荷工况下降低了9.7%;随着EGR率的增加,THC排放增加,而NOx排放显著降低,CO排放在低速小负荷时出现上下波动的现象,而在中速中负荷工况时,随着EGR率的增加不断降低。 相似文献
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基于柴油机排气热管理的喷油策略控制试验研究 总被引:3,自引:0,他引:3
为有效满足柴油机中低转速、中小负荷工况下颗粒捕集器(DPF)主动再生时的工作温度需求,利用发动机台架试验研究了中低负荷稳态工况下主喷正时、近后喷及次后喷参数等排气热管理主动控制措施对缸内燃烧过程、排气热状态及排放性能的影响规律。稳态试验结果表明:推迟主喷提前角缩短了滞燃期,燃烧持续期延长,缸内最高燃烧压力及峰值温度下降,瞬时放热率峰值减小且燃烧重心后移,同时燃油消耗率及烟度略有增加,DOC入口温度提升也不明显;引入近后喷使得缸内最高燃烧压力降低,但放热率第二峰值及后燃期有所增加,近后喷油量与主-近后喷间隔角的合理匹配能适当提高DOC入口温度,最高增幅可达19.3%,同时也能有效改善NOx排放和烟度;次后喷油量的增加能显著提升DPF入口温度,最大增幅达70%,但会导致燃油消耗率及HC逃逸量增加。依据样机全工况排温分布状态提出各区域升温喷油控制策略:低负荷区域采用"近后喷+次后喷"的喷油组合,并且采用较大喷油量;中大负荷区域逐渐减少近后喷,直至无近后喷,同时将主喷适当提前。 相似文献
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Miaomiao Zhang Wei Hong Fangxi Xie Yan Su Liwei Han Bin Wu 《International Journal of Automotive Technology》2018,19(3):393-404
A detailed investigation of the impact of injection timing and injection pressure on combustion and particles of a spray-guided GDI engine was conducted, under different engine operating conditions. The results indicated that, more proportion of large particles were emitted when increasing engine load, and the peak of accumulation mode particles moved toward smaller size when rising engine speed. With retarding the injection timing, the in-cylinder pressure and heat release rate rose first and then dropped at 2000 rpm, but they continuously rose at lower or higher speed conditions. The total particles concentration curves at all cases showed a trend of U-shape, and the corresponding timing of the lowest particles concentration advanced as the engine speed or load increased. The minimum value of emitted particles first rose and then fell when increasing load at 2000 rpm conditions, and it continuously rose when increasing speed at 40 Nm conditions. Generally, injection pressure did no sensitively affect combustion process except that it showed a relatively strong impact at low load conditions. However, particulate matter could be effectively inhibited by elevating fuel pressure from 5.5 to 11.5 MPa at all cases. In detail, the total particles concentration continuously fell at low speed and mid speed-high load cases, but it showed a rose trend when further increase fuel injection pressure at mid speed-low load and high-speed conditions. 相似文献
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柴油微引燃乙醇发动机采用进气道喷射乙醇、缸内直喷微量柴油引燃的方式进行燃料供给。基于单缸四冲程柴油机,对其燃烧、性能及排放特性进行研究,固定引燃柴油喷射量为发动机能实现压燃着火的最小值,在进气压力为0.15 MPa时比较不同乙醇喷射量的工况组,通过改变柴油喷射时刻进行工况扫描。结果表明,引燃柴油的喷射时刻对发动机的燃烧、性能和排放影响显著。柴油微引燃乙醇发动机在中高负荷能够稳定运行,指示热效率可达34%以上,通过适当调节柴油喷射时刻,可以有效控制未燃碳氢(UHC)、NO_x与CO排放,同时可以实现极低的炭烟排放。柴油微引燃乙醇发动机燃烧模式为预混合或部分预混合燃烧,燃烧有两阶段放热特征,改变引燃柴油喷射时刻,可以有效控制燃烧相位。 相似文献