【作者】 张文杰；

【导师】 刘忠长；

【作者基本信息】 吉林大学 ， 动力工程及工程热物理， 2015， 硕士

【摘要】 柴油发动机以其动力性强、经济性好和可靠性高等优点而备受重视。然而能源与环境形势的日益严峻以及排放法规的日趋严格，再加上当今雾霾问题的严重影响，这些都对柴油机的性能提出了更加苛刻的要求。车用柴油机大部分的工作时间处于瞬态工况，且瞬态工况时柴油机的性能存在明显的恶化现象。在当今出现的众多改善柴油机性能的技术中，二级涡轮增压技术以其增压压力大、响应性高等特点对柴油机瞬态性能的改善有着巨大的潜力。本研究以高压共轨增压柴油机为试验样机，开展了供气策略对柴油机瞬态性能影响的研究，研究内容分为两部分。第一部分，为了能够得出柴油机瞬态过程中性能恶化的主要原因，对试验原机进行了瞬态试验。试验选取1650r/min转速不同起始负荷的恒转速加载过程，具体研究结果如下：1）通过原机稳态与瞬态工况的试验对比得出：瞬态过程中由于涡轮增压器的迟滞现象使得进气存在明显的滞后，这使得缸内的燃烧环境变差、燃烧恶化，碳烟排放急剧增加、燃油经济性变差，而NOx的排放由于缸内氧浓度下降而降低。2）与稳态工况相比，增压柴油机固有的进气迟滞现象对其瞬态性能的影响明显高于不同加载起始工况对柴油机瞬态性能的影响。第二部分，研究二级涡轮增压系统对柴油机性能的影响。首先对二级涡轮增压系统中重要的部件进行选取，然后为验证二级涡轮增压系统的有效性，研究二级涡轮增压柴油机稳态工况下其外特性、负荷特性以及不同涡轮旁通阀开度对此系统下柴油机性能的影响，最后研究二级涡轮增压系统对柴油机瞬态性能的影响。具体研究结果如下：1）外特性试验通过与原机对比得出：进气量在全工况范围内都有较大幅度的上升，最大增幅约为31%；柴油机工作在低转速时其性能有明显改善，比油耗、烟度排放明显下降，同时扭矩也明显增大，比油耗最大降幅约为原机的12%，烟度由原机的9.96不透光度降低到1.19不透光度；高转速时，由于排气背压增大、进排气过程流动造成的能量损失对柴油机性能的影响占主导地位，所以二级涡轮增压柴油机的性能劣于原机。2）负荷特性试验通过与原机对比得出：1330r/min转速低负荷时由于柴油机缸内燃烧环境处于富氧状态，此时排气背压及进排气过程流动造成的能量损失对柴油机的性能影响程度更大，所以二级涡轮增压柴油机的性能劣于原机；随负荷的增加，进气量对柴油机的性能影响程度逐渐增大，大负荷时二级涡轮增压柴油机的性能相对比于原机有很大改善。转速增大，高负荷时二级涡轮增压柴油机表现出优于原机的性能逐渐减弱，甚至劣于原机。3）不同涡轮旁通阀开度对二级涡轮增压柴油机性能影响的试验表明：不同工况下，柴油机最佳性能所对应的涡轮旁通阀开度不同，且涡轮旁通阀的有效调节范围为0-40%开度。最佳涡轮旁通阀开度时柴油机的负荷特性相比于涡轮旁通阀全关时有了明显的改善。4）通过对涡轮旁通阀全关时二级涡轮增压柴油机与原机瞬态性能进行对比得出：加载过程中由于二级涡轮增压系统所具有增压压力大且响应性高等特点，二级涡轮增压柴油机的瞬态性能明显优于原机的瞬态性能。5）不同涡轮旁通阀开度对二级涡轮增压柴油机瞬态性能影响的试验表明：1650r/min转速负荷从10%加载到90%的瞬态过程中，涡轮旁通阀10%开度相比于涡轮旁通阀全关，柴油机瞬态过程中比油耗有所改善，但烟度有所增加；而涡轮旁通阀开度进一步增大到20%时，柴油机比油耗相较于10%开度有所增加，且烟度排放进一步恶化。6）不同加载时间对二级涡轮增压柴油机瞬态性能影响的试验表明：随着加载时间的缩短，柴油机的瞬态性能呈逐渐恶化趋势。更多还原

【Abstract】 Diesel engine with good performance、fuel economy and high reliability has beenconcerned. But face with the situation that energy and environment are growing deteriorationand haze arose, we have to improve the performance of diesel engine. Diesel engine work attransient condition in lots of time, and performance get worsen. In many technologies, twostage turbocharging system has huge potential to improve diesel engine’s transientperformance with higher intake air pressure and faster responsiveness.Base on high pressure common rail–turbocharged diesel engine, to research theinfluence of gas supply strategy on diesel engine transient performance. The study includestwo parts. The first part, through the transient experiment on diesel engine, to find out thereason why performance of diesel engine get worse under the transient operating condition.Test point selection for constant engine speed and increasing torque process. The specificresearch results as follows:1) Through the test comparison of steady-state and transient operating condition, resultsshow that combustion process of diesel engine get worse at transient operating condition,smoke opacity increase and NOx emission decrease.2) Compared with steady-state condition, the influence of inherent turbo lag characteristic ofturbocharged engine on diesel engine transient performance more important than differentinitial load under constant engine speed and increasing torque process.The second part, study the effect of two stage turbocharging system on diesel engineperformance. Including the selection of important component of two stage turbochargingsystem、system validity verification and influence on diesel engine transient performance.The specific research results as follows:1) Through the test of diesel engine work at full-load operating condition, compared withoriginal engine, air-fuel ratio has obvious increase within the range of condition, thebiggest increase is about31percent; when diesel engine work at low speed condition, theperformance has obvious improvement, such as fuel economy、smoke opacity. BSFC decreased12percent, smoke opacity decrease from9.96to1.19; work at high speed, dueto increased exhaust back pressure, the performance of diesel engine with two stageturbocharging system is deteriorated.2) Through the test of load characteristic, the performance of diesel engine with two stageturbocharging system is worse than original engine when load is low. With the increaseof load, BSFC and smoke opacity are improved, reaching full-load condition, it betterthan original engine. Increasing engine speed, the advantage will be weakened.3) Study about different valve opening of turbo bypass valve, different operating conditionhave different best opening, effective adjusting range, at the same time, is0-40percentopening.4) Compared with original engine transient performance, two stage turbocharging systemcan enhance diesel engine transient performance obvious.5) Study about different turbo bypass valve opening at constant speed and increasingoperation condition, the results show that BSFC is improved, compared with originalengine, but the emission of soot is increased, when turbo bypass valve opening at10percent. Increasing to20percent, both BSFC and smoke opacity get worse than10percent opening.6) Study about different loading time at constant speed and increasing operation condition,the results show that diesel engine transient performance is deteriorative with loadingtime shortening.更多还原