中文摘要:       将甲醇、乙醇、正丁醇和2,5-二甲基呋喃（DMF）分别与市售编号为92号汽油按照体积比为1∶9的比例混合，连同纯汽油组成M10、E10、B10、F10、G100 5种燃料，在一辆缸内直喷（GDI）乘用车上研究不同燃料对整车性能的影响。试验结果表明，在新欧洲驾驶循环(NEDC)下，丁醇混合燃料的百公里体积油耗和去除热值影响的当量油耗均是被测5种燃料中最低的，其余3种含氧燃料掺混后的百公里体积油耗和当量油耗均高于纯汽油燃料；除M10的CO排放比汽油低外，含氧汽油的CO和THC排放均高于汽油；掺混3种醇类燃料均能够降低NOx排放，F10的NOx 排放与纯汽油相当；4种含氧汽油大幅降低了颗粒物质量和数量排放。向汽油中添加含氧燃料能够降低汽车在中高车速稳定运行时的油耗和排放，但添加含氧燃料后的汽油比纯汽油更加不适应低车速和起动工况。在动力性方面，4种含氧汽油均缩短了汽车的加速时间。 英文摘要:       An experiment of the effect of different fuels on engine performance and emissions was carried out on a gasoline direct injection(GDI) passenger car. The fuels used in the experiment were pure gasoline and four oxygenated gasoline fuels prepared by adding methanol, ethanol, n-butyl alcohol and 2,5dimethylfuran(DMF) in the pure gasoline respectively in 10% in volume, and coded as G100, M10, E10, B10 and F10. The results show that under new European driving cycle(NEDC), B10 is the lowest among the five tested fuels in terms of 100 kilometer of fuel consumption in volume and the equivalent fuel consumption after removing calorific value, and the other three oxygenated fuels are higher than G100. CO and THC emissions of the oxygenated fuels are higher than those of G100, except for the CO of M10 which is lower than that of G100. Adding methanol, ethanol or n-butyl alcohol in pure gasoline is beneficial to reducing NOx emissions, but the NOx emissions of F10 are almost equivalent to those of G100. The oxygenated fuels could significantly reduce the particulate mass(PM) and particulate number(PN). And all the oxygenated fuels can decrease fuel consumption and emissions when the car runs steadily at medium and high speeds, but they are poor at adapting to the working conditions of low speed and vehicle starting. They all could, however, shorten the vehicle acceleration time.

中文摘要:       基于便携式车载排放测试系统（portable emission measurement system, PEMS）,对某型号重型柴油车进行实际道路排放测试,分别利用车辆比功率（VSP）和车辆牵引力（VA）对NOx 排放值进行拟合。以这两个因子作为输入参数,应用自适应学习速率法改进后的双隐含层反向传播（BP）神经网络来训练和预测NOx 的排放情况。与原BP网络预测情况相比,预测值与实际值的皮尔逊相关系数提高了0.1136,相对误差降低了0.6621%,改进后的神经网络预测准确度有所提升,泛化能力较强,可以用于该款重型柴油车NOx排放的实时预测,具有一定的工程应用价值。 英文摘要:       Based on the portable emissions measurement system(PEMS), an actual road emissions test was performed on a certain type of heavy-duty diesel vehicle, and NOx emissions were fitted by the vehicle specific power(VSP) and vehicle traction force(VA) respectively. Using these two factors VSP and VA as input parameters, a double-hierarchical BP neural network improved by adaptive learning rate method was used to train and predict the NOx emissions. Compared with the original BP network prediction, the Pearson correlation coefficient between a predicted value and an actual value was increased by 0.1136, and the relative error was reduced by 0.6621%. The accuracy of the improved neural network prediction was promoted, and the generalization ability was strong. The improved neural network is applicable for the real-time prediction of the NOx emissions of this heavy-duty diesel vehicle, which has certain engineering application value.

中文摘要:       在一台高压共轨重型柴油机上开展了气道喷水结合高压废气再循环（EGR）的试验研究。基于世界统一稳态测试循环（WHSC）各工况点探索引入高压EGR和气道喷水技术对柴油机排放和燃油经济性的影响；在此基础上对各工况的燃烧相位进行优化，得到WHSC各工况点下基于喷水和EGR的优化策略。结果表明：综合考虑排放和燃油经济性，低负荷工况宜单独引入高压EGR，并通过提前喷油时刻（start injection timing，SOI）优化燃烧相位；中高负荷工况宜少量喷水并引入适当EGR，满负荷则应单独采取气道喷水策略。WHSC加权结果表明，在保持较低的HC、CO和碳烟排放前提下，优化后的加权NOx比排放降低7.71 g/(kW·h)，降幅约45.2%，有效燃油消耗率降低约1.20 g/(kW·h)。 英文摘要:       An experimental study of inlet water injection combined with high pressure(HP) exhaust gas recirculation(EGR) was conducted on a high pressure common rail heavy-duty diesel engine. The effects of introducing HP EGR and inlet water injection on diesel engine emissions and fuel economy were investigated at all working points of the world harmonized steady-state cycle(WHSC). Based on that, the optimization of the combustion phase at each working point was carried out to obtain an optimal control strategy of coupling inlet water injection with EGR over the WHSC cycle. The results show that, considering both the emissions and fuel economy, the HP-EGR should be introduced at low load conditions and the fuel injection timing should be advanced to obtain a better combustion phase. A small amount of inlet water injection and a proper rate of EGR should be adopted at medium and high load conditions, while the inlet water injection strategy should be adopted at full load. The weighted WHSC results show that the optimized weighted NOx specific emissions can be reduced by 7.71 g/(kW·h), a reduction of about 45.2%, and the weighted brake specific fuel consumption(BSFC) can be decreased by 1.20 g/(kW·h), while still maintaining low HC, CO and soot emissions.

中文摘要:       对柴油机颗粒过滤器（diesel particulate filter, DPF）进行了颗粒物（particulate matter, PM）在线捕集试验。通过发动机废气排放颗粒物粒径谱仪EEPS-3090分析了DPF对不同粒径PM的捕集特性；通过扫描电镜仪和热重分析仪探究了DPF前后端PM的堆积形貌及氧化特性。研究结果表明：DPF对大粒径颗粒物的捕集效果优于小粒径颗粒物,聚集态颗粒物基本被DPF完全拦截；DPF孔道过滤壁面的深层碳烟减小了微孔孔径,随着采样时间的增加,DPF对PM的捕集率升高。柴油机排气流经DPF后,逃逸出少量PM,以核态颗粒物为主。与DPF前端相比,后端PM的挥发性组分含量升高，元素碳的含量下降,氧化活性增强。 英文摘要:       An on-line particle trapping test was carried out with a diesel particulate filter(DPF). The trapping characteristics of the DPF for different particle size were analyzed by using an exhaust particle size spectrometer. The stacking morphology and oxidation characteristics of the particles at the front and rear ends of the DPF were investigated by scanning electron microscope and thermo gravimetric analyzer. Results show that the DPF captures large size particles better than small size particles, and can almost completely intercept accumulation mode particles. Since the soot on the filter wall reduces the filter pore size, the trapping efficiency of the DPF increases with the rise of sampling time, with only a small amount of nucleation mode particles leaked off. Use of the DPF can lead to an increase in the content of volatile components coupled to the reduction of elemental carbon content, and eventually promotes the enhanced oxidation activity downstream of its outlet.

中文摘要:       以一台国五发动机为基础设计了4-1和4-2-1两款集成排气歧管,通过一维仿真的方式探究两种形式的集成排气歧管对发动机动力性能的影响。结果表明：采用了集成排气歧管后,转速大于1600 r/min时转矩变化不明显,与原机转矩有2%的波动；但转速低于1600 r/min时,转矩下降较多,其中4-1方案低速下转矩下降更加明显,1200r/min时转矩下降11.1 N·m，比原机下降5.9%。继而以1200 r/min为例探究了低速情况下,采用集成排气歧管造成转矩下降的原因。结果表明,采用了4-2-1与4-1集成排气歧管后,涡轮增压器前压力状态产生差异,影响了增压器效率；气门叠开期期间,由于排气背压增大,导致废气回流增加和缸内残余废气量增加,降低了充量系数。最后通过试验验证,采用了4-1集成排气歧管后的低速转矩确实低于原机,验证了仿真的准确性。 英文摘要:       Based on a CN Ⅴ gasoline engine, two integrated exhaust manifolds of Type 4-1 and 4-2-1 were designed, and the effect of these two different structures on engine dynamics was studied by one dimensional simulation. Results show that with the integrated exhaust manifold, the engine torque does not change obviously at the speed greater than 1600 r/min, with a fluctuation of 2% relative to the original exhaust manifold. However, at the speed less than 1600 r/min, the engine torque drops significantly. Especially for the use of Type 4-1 exhaust manifold, the engine torque drops by 11.1 N·m at the speed of 1200 r/min, which is more than 6% torque of using original exhaust manifold. Therefore, the reason for the reduction of low speed torque caused by the integrated exhaust manifold was studied at the speed of 1200 r/min. Results show that the use of integrated exhaust manifold changes the intake pressure before the turbocharger, which affects the turbocharger efficiency. At the same time, an increase in the exhaust back pressure during the overlap of intake and exhaust valves causes an increase in the exhaust reflux and residual gas in the cylinder, thus reducing the inflation coefficient of the engine. The final test indicates that the use of Type 4-1 integrated exhaust manifold is indeed to make the low speed torque lower than with the original exhaust manifold, which verifies the accuracy of the simulation calculation.

中文摘要:       为明确汽油单液滴撞壁特性，设计了单液滴撞壁系统，分析了汽油液滴撞壁现象及不同壁面对汽油液滴撞壁结果转捩的影响。研究表明：汽油液滴撞击干壁面时在壁面粘附铺展成一层附壁油膜，附壁油膜促使液滴再次撞壁时发生皇冠射流飞溅现象。附壁油膜越薄，飞溅越剧烈，飞溅持续时间越短。相比硅油膜动力黏度，硅油膜厚度对汽油液滴撞壁后形态演变过程影响更大。汽油液滴撞击硅油膜会稀释硅油膜，稀释前后射流分别为碗状射流、皇冠状射流。随着稀释程度增加，皇冠状射流的二次液滴数量增加，二次液滴中含有壁面硅油组分。无量纲时间 τ<1时，Rioboo模型能较好地预测铺展因子变化规律，但若超过此时间则Rioboo模型预测不准。 英文摘要:       In order to clarify the characteristics of single gasoline droplet impacting on different substrates, a single droplet impingement system was designed, and the effects of different substrates on impingement results were compared and studied. The results show that single gasoline droplet impacting on a dry wall is easy to deposit to form a gasoline film. The presence of the attached gasoline film will promote a crown jet splash phenomenon when the droplet hits the wall again, causing secondary droplets. The thinner the gasoline film is, the more violent the splash is and the shorter the duration of the splash is. Compared with the viscosity of a silicone oil film, the thickness has a greater influence on the morphological evolution of the gasoline droplet and silicone oil film after collision. When single gasoline droplet impacts on pure silicone oil films of different thicknesses and viscosities, there is no secondary droplets splash. However, the gasoline droplet will deposit and penetrate any silicone oil film and diluts the silicone oil. There is bowl splash before the dilution and crown jet splash after the dilution. The number of secondary droplets increases with the increase of the amount of gasoline in any silicone oil film. The secondary droplets contain silicone oil. The Rioboo model can better predict the variation law of the spreading factor when the dimensionless time is less than 1, but it can not predict accurately when the dimensionless time exceeds 1.

中文摘要:       研究不同喷油策略对自由活塞发动机燃烧排放性能的影响,探索了适合自由活塞发动机柴油燃烧系统的喷油策略。基于AVL FIRE仿真平台,搭建三维动网格计算模型,通过台架试验数据,对试验喷油策略为矩形的缸压数据进行标定,验证了模型的准确性。然后对4种不同曲线形状喷油策略（普通三角形、等腰三角形、矩形和梯形）下的发动机燃烧放热及排放性能进行了仿真计算。研究结果表明：压缩上止点前采用矩形喷油策略缸内油气混合速率最快,压缩上止点后采用等腰三角形喷油策略更有利于油气混合；等腰三角形喷油策略下发动机峰值燃烧压力最大,最接近上止点,而且指示热效率最大,达到0.371；等腰三角形喷油策略下,缸内峰值燃烧压力和温度最大,NO排放最高而碳烟排放最低。 英文摘要:       The effect of different fuel injection strategies on the combustion and emissions of a free-piston linear engine was researched, and diesel fuel injection patterns suitable for the engine were explored. A three dimensional moving mesh model was established based on the AVL FIRE platform, and the accuracy of the simulation model was validated by the experimental in-cylinder pressure under a rectangle-shaped injection strategy. The engine combustion and emissions under four different injection strategies(normal triangle-shaped, isosceles triangle-shaped, rectangle-shaped and trapezoid-shaped) were simulated. The results indicated that the mixing rate in cylinder was the greatest when adopting the rectangle-shaped injection strategy before the top dead center(TDC), and the mixture homogeneity was better when employing the isosceles triangle-shaped injection strategy after TDC. The peak pressure in cylinder was the greatest and nearest to TDC when adopting the isosceles triangle-shaped injection strategy, with which the indicated thermal efficiency was the highest, reaching 0.371. Besides, the NO mass fraction under the isosceles triangle-shaped injection strategy was the largest while the soot emission was the least among the four injection strategies.

中文摘要:       对一台增压直喷汽油机进行低速早燃（low speed pre ignition, LSPI）试验研究，在转速为1750 r/min和转矩为320 N·m这一典型的低速早燃工况下，早燃的着火时刻越早，爆震发生倾向越高，并且强度也越大。试验同时研究了发动机运行参数和机油物理化学性质对早燃的影响，研究结果表明随着中冷温度和冷却液温度的提高，早燃频次增加；高黏度的机油可以抑制超级爆震频次和发生倾向；机油添加剂中钙元素对超级爆震的发生起极大促进作用，磷元素起较大抑制作用，镁元素的抑制作用最小。 英文摘要:       A low speed pre-ignition characteristics was studied on a turbocharged direct injection gasoline engine. Results show that under low speed pre-ignition conditions at the speed of 1750 r/min and with a torque of 320 N·m, the earlier the ignition timing of pre ignition, the greater the knocking tendency and its intensity. Moreover, studying the influence of engine operating parameters and lubricating oil physicochemical properties on pre-ignition also shows that the frequency of pre-ignition increases with the rise of inter-cooler temperature and coolant temperature. High viscosity lubricating oil can suppress the frequency and tendency of superknock. Moreover, calcium element in the oil additive greatly promotes the occurrence of superknock, while phosphorus element plays a greater inhibitory role, and magnesium element has the least inhibitory effect.

中文摘要:       基于计算流体力学（CFD）软件CONVERGE建立了大型低速2冲程柴油引燃缸内直喷天然气船用发动机燃烧仿真模型。首先通过试验结果对模型进行了验证，进而开展了天然气高压喷射模式（high pressure direct injection，HPDI）下米勒循环和天然气两次喷射策略对发动机压力振荡的抑制效果研究。结果表明，推迟排气门关闭时刻，整体燃烧压力降低，燃烧相位推迟，发生剧烈压力振荡的时刻也推迟。排气门关闭时刻推迟较小时压力振荡强度降低，但过度推迟反而提高缸内压力振荡的强度，这主要是缸内热力学状态变化和燃料自燃特性相互作用的结果。通过调整预喷射量，可以降低燃烧前形成的可燃混合气量，从而影响燃烧过程中预混合燃烧比例，可以有效抑制压力振荡.但会导致输出功率降低及能耗增大。相比预喷射量，喷射间隔对缸内压力振荡的影响较小，但过大喷射间隔会影响燃烧相位，导致功率损失严重。合理的喷射策略可以在抑制压力振荡的同时保证功率输出。 英文摘要:       Based on the computational fluid dynamics(CFD) software(CONVERGE), the simulation model of a large low-speed two-stroke marine engine in which pilot diesel and natural gas are injected directly in cylinder was established. Validated by the experimental data from the literature, the model was then applied to studying the suppression effect of the Miller cycle and natural gas two-stage injection strategy on the pressure oscillation in high pressure direct injection mode. The calculation results indicated that when the exhaust valve was closed later, the overall combustion pressure was lower, both the combustion phase and the moment of severe pressure oscillation were delayed. The intensity of pressure oscillation was reduced with smaller delay of exhaust valve closing, while it was increased instead with an excessive delay. This was primarily attributed to the competitive relation between in-cylinder thermodynamic state and auto-ignition characteristics of fuel. Adjusting the pre-injection quantity of natural gas would reduce the formation of premixed combustible mixture before combustion, thus reducing the proportion of premixed combustion in the combustion phase, which could effectively suppress pressure oscillation, but could also reduce the output power and increase the fuel consumption. Compared with the pre-injection quantity, varying injection interval has less effect on the pressure oscillation, but the excessive injection interval would affect the combustion phase, resulting in considerable power loss. A reasonable injection strategy can ensure the power output while suppressing intense pressure oscillation.

中文摘要:       基于CONVERGE建立了高压直喷（high pressure direct injection, HPDI）天然气低速船机三维仿真模型,并基于该模型研究了米勒循环和废气再循环（exhaust gas recirculation, EGR）对发动机燃烧特性及污染物排放的影响规律,探究了米勒循环耦合EGR路线满足Tier Ⅲ排放法规的可行性。研究结果表明,单独使用30%EGR率可满足Tier Ⅲ排放标准,但指示油耗和碳烟排放增加显著；应用米勒循环降低NOx 排放的潜力低于EGR；过大的排气门晚关角度会增大压气机工作负荷,且降低等量NOx 排放情况下油耗牺牲较大；采用25%EGR率耦合小程度米勒循环（排气门关闭时刻推迟5°曲轴转角）并适当提前天然气喷射正时（提前2°曲轴转角）,可在指示油耗仅增加158%的前提下降低77%的NOx 排放,是满足Tier Ⅲ排放法规可行的技术路线。 英文摘要:       Based on a three-dimensional simulation model established using CONVERGE, the effects of exhaust gas recirculation and the Miller cycle on the combustion characteristics and emissions were studied to explore the feasibility of the Miller cycle coupled with EGR to meet Tier Ⅲ emission regulations for low-speed high-pressure direct injection natural gas marine engines. The results show that using 30% of EGR rate alone can meet Tier Ⅲ emission standards, but with a significant increase in the indicated fuel consumption and soot emissions; the Miller cycle is not as effective as EGR in the potential to reduce NOx emissions; excessive exhaust valve closing delay will cause increase in compressor workload, and lead to a considerable increase in fuel consumption when the same amount of NOx emissions is reduced. Coupling mild Miller cycle(delaying exhaust valve closing by 5° in crank angle) with 25% of EGR rate and the proper natural gas injection timing(advancing 2° in crank angle) can reduce NOx emissions by 77% with only a slight increase in the fuel consumption by 1.58%, which is a feasible way to meet Tier Ⅲ emission regulations.