为了探究环境属性与燃油属性对单组分液滴蒸发特性的影响，建立了高温高压单液滴蒸发试验装置，系统研究了正庚烷、正十二烷和正十六烷单液滴在高温高压下的蒸发特性．结果表明：当环境温度超过燃油的临界温度且环境压力接近燃油的临界压力时，液滴周围就会出现“可见蒸气”，且随着压力的升高，“可见蒸气”的量逐渐增多．此外，随着环境温度的升高，环境压力的升高对 3 种燃油液滴蒸发速率的影响由抑制转变为促进，在某一温度下，环境压力的变化对燃油液滴的蒸发速率影响很小，该环境温度接近燃油的临界温度．在当前研究的压力范围内，正庚烷、正十二烷和正十六烷燃油液滴蒸发速率的变化率均随环境温度的升高而增加，且环境压力越高，蒸发速率随环境温度的增加幅度越大．

采用光学电子显微镜分析了某型柴油机喷油器喷孔积碳的分布区域、形状和大小．采用扫描电子显微镜和能谱仪分析了积碳的微观形貌和元素组成．结果表明：按照分布区域划分，喷孔积碳可分为出口积碳、孔内大颗粒积碳和孔内壁面积碳 3 类，出口积碳比较明显，积碳量最多，大致呈圆弧状均匀分布在出口周围，孔内大颗粒积碳较少，形状不规则，孔内壁面积碳大致在壁面均匀分布，但积碳量不显著，导致壁面粗糙度增大；从微观形貌发现，底层积碳呈球状，球状颗粒之间排列紧密，结构复杂，表层积碳整体连成一片，结构紧实，无明显的颗粒状，表面相对整齐平坦；积碳主要由 C 和 O 元素组成，另外还有少量的 Si、Fe、K、Mo、Cl 和 Cr 元素，Fe、Mo 和 Cr 元素可能是由缸套活塞磨损产生的颗粒随润滑油吸附在积碳中，Si、K 和 Cl 元素可能来自机油和机油添加剂．

基于小型 Wankel 发动机的混合润滑情况，首先分别建立转子端面与端盖之间、径向密封片与气缸之间以及轴承的摩擦损失功率预测模型；然后利用倒拖法测试转子端面、径向密封片和轴承的摩擦损失功率，并验证上述模型的正确性；最后利用模型研究了工作状态下小型 Wankel 发动机的摩擦损失功率．结果表明：工作状态下，小型 Wankel 发动机的摩擦损失功率主要由转子端面、径向密封片和轴承的摩擦损失功率组成．其中转子端面引起的摩擦损失功率最大，占整机摩擦损失功率的 60%左右，此比例随转速的上升变化不大．转子端面和径向密封片的摩擦损失功率主要是由微凸体相互接触引起的．

根据燃油一次破碎后形成的油滴运动特点，建立了与实际更加相符的二次雾化模型，通过 N-S 方程和线性化分析方法导出各参数之间的本征关系，并给出本征方程的解，基于方程的解，分别研究 Ma 数、 Bond 数、Oh 数和气/液密度比 κ 对油滴二次破碎的影响，结果表明：气体可压缩性对油滴的二次破碎具有促进作用，但效果不明显，一般情况下可以忽略气体可压缩性的影响，油滴的黏性可以抑制油滴的破碎，而油滴受到气动作用力是油滴破碎的直接原因，因而提高 Bond 数可得到更好的雾化效果．

中文摘要: 为了改善重型柴油机低速高负荷的燃油经济性，在一台两级可变截面涡轮增压重型柴油机上开展了空气系统与喷油参数优化策略研究。试验结果表明：对于缸内最高燃烧压力受限工况，获得最低有效燃油消耗率(BSFC)的可变截面涡轮增压器(VGT)关度应该使泵吸功基本为零；选取合适的喷油压力可提高机械效率，在改善燃油经济性的同时使 NOx 排放有一定降低，而碳烟排放也能保持在较低水平。基于该优化策略，研究了缸内最高燃烧压力限值对不同工况点燃油经济性的影响，进而研究了提高缸内最高燃烧压力对改善燃油经济性的潜力。结果表明：随着转速与负荷的升高，提高最高燃烧压力限值对燃油经济性的改善作用更加明显；但缸内最高燃烧压力提高到一定程度以后，其对燃油经济性的改善作用逐渐减小。 英文摘要: In order to improve the fuel economy of a heavy duty diesel engine at low speed and high load, study on the optimization strategy of intake air system and fuel injection parameters was carried out on a two-stage variable geometry turbocharged heavy duty diesel engine. Results show that in the case of limiting the maximum burst pressure in the cylinder, the turbocharger vane can be adjusted to achieve the lowest fuel consumption only when the pumping loss is substantially zero. Moreover, choosing a right injection pressure can increase mechanical efficiency and improve fuel economy, while reducing NOx emissions and keeping soot emissions low. Based on the optimization strategy proposed in the above study, the influence of maximum burst pressure in the cylinder on the fuel economy under different operating conditions was studied, and the potential of increasing maximum burst pressure in the cylinder to improve fuel economy was further explored. Results show that as speed and load increase, the advantage of increasing the maximum burst pressure limit is more obvious for improving fuel economy. However, after the maximum burst pressure is increased to a certain extent, its effect on improving fuel economy will gradually decrease.

中文摘要: 为提高航空煤油在点然式发动机中的燃烧热效率，改善发动机爆震及拓宽发动机负荷范围，以3号航空煤油（RP-3）为基础燃料，基于一台单缸水冷、压缩比可调、4冲程点燃式发动机结合高压共轨缸内直喷技术，开展了单双点火、不同负荷、压缩比、喷射压力、喷射时刻和两次喷射策略下航空煤油燃烧特性的试验研究。结果表明，在原机压缩比为10的条件下，将直喷汽油改为直喷航空煤油后，由于航空煤油的抗爆性差、雾化困难、燃烧速率慢等理化特性，发动机的动力性损失约50.0%，油耗增加约60.0%，循环波动也大幅增加；相比于单点火，双点火可使缸内平均有效压力提高，燃烧相位提前，循环波动降低；为了抑制高压缩比下的爆震倾向，可通过降低压缩比来拓宽负荷范围，恢复原机功率。随着压缩比的降低，有效平均压力（BMEP）持续增大，当压缩比为6时，最大转矩可达39.5 N·m，功率恢复至原机的88.0%。同时耦合高压及两次喷射策略，随着喷射压力的增大，有效燃油消耗率（BSFC）减小约30.0%，经济性有所提高。相比于单次喷射，采用两次喷射策略可降低油耗，提升缸内有效平均压力，提升燃烧效率，最终可实现发动机燃用航空煤油的性能接近原机水平，最大负荷达原机的90.0%且油耗增加量不超过15.0%。 英文摘要: In order to improve the combustion thermal efficiency of aviation kerosene in spark ignition engine, suppress knock and broaden engine load range, a single-cylinder water-cooled, four-stroke gasoline engine of adjustable compression ratio was used together with high pressure common rail direct injection technology to study the effects of single and twin sparks, different loads, different compression ratios, different injection pressures, different injection timings, and split injection on the combustion performance of aviation kerosene. The results show that, when the compression ratio of 10 of the base engine is kept and the direct injection of gasoline is replaced by the direct injection of RP-3, the engine power loss is by about 50%, the fuel consumption rises by about 60%, and the cycle fluctuation increases greatly due to the low octane number, poor atomization and slow combustion rate of the aviation kerosene. Compared with the single-spark, the twin-spark can enhance the mean effective pressure in cylinder and combustion phase. In order to avoid the knock tendency at high compression ratios and widen the load range, the compression ratio is reduced, raising the engine power close to the base engine level. With the decrease of the compression ratio, the brake mean effective pressure continues to increase. When the compression ratio is reduced to 6, the optimal torque can reach 39.5 N·m, restoring 88% of the base engine power. Meanwhile, the effective fuel consumption can be reduced by about 30% by coupling high pressure and split injection strategy, improving fuel economy. Compared with the single-injection, the split injection strategy can reduce the fuel consumption, increase the mean effective pressure in cylinder, and promote the combustion efficiency, which enables the engine using aviation kerosene to achieve the performance close to the base engine level.

中文摘要: 采用试验的方法，利用重整器和发动机台架研究了正庚烷和异辛烷体积比1∶1的PRF50燃料在不同重整温度下的低温重整产物及其对压燃发动机中等负荷下燃烧和排放特性的影响。研究结果表明，PRF50燃料在450 K~750K的重整温度下低温反应放热量较少，重整器内温度基本不变。重整产物中的轻烃分子对发动机燃烧具有促进作用，可以使燃料重心（CA50）提前，而产物中的CO、CO2 对燃烧具有抑制作用；随着重整温度的提升，重整产物促进作用逐渐增强，达到最高值后逐渐减弱；在相同喷油时刻下，随着重整温度的增加，指示热效率先逐渐升高后降低，最多提高2%。 英文摘要: The low temperature reformed products of PRF50 operation at different reforming temperature and their effects on engine combustion and emission characteristics under medium load were investigated by using a reformer and an engine test bed. Results show that the use of PRF50 fuel releases a small amount of heat in the low temperature reaction at the reforming temperature of 450 K to 750 K, while the temperature inside the reformer remains essentially unchanged. The light hydrocarbon molecules in the reformed products can promote the engine combustion to advance the angle of 50% mass fraction burned(CA50), and the CO and CO2 in the reformed products have an inhibitory effect on combustion. As the reforming temperature increases, the promoting effect of the reformed products increases first and then decreases gradually after reaching the highest value. Moreover, at the same injection timing, as the reforming temperature increases, the indicated thermal efficiency increases first and then begins to decrease after reaching a peak of 2%.

中文摘要: 针对乙醇与汽油固定掺混比例下使用不能充分发挥乙醇燃料优势的问题，开发出了乙醇汽油双燃料-双直喷系统，并在一台点燃式单缸试验机上进行试验，研究了稀薄燃烧下3种不同的喷射策略对发动机燃烧和性能的影响。研究发现：在稀薄燃烧的情况下，随喷射时刻的推迟，不同喷射策略下动力性呈现先增长后降低的趋势。在保证喷油量不变时，有效热效率随过量空气系数增大而明显提高，当量燃油消耗率逐渐降低。随喷射时刻的推迟，热效率呈现先升高后降低的趋势。在过量空气系数为1.2，汽油喷射时刻为上止点前180°，乙醇喷射时刻为上止点前300°时，有效热效率达到最高值40.5%。此外，相比于汽油，添加乙醇燃料使得稀薄燃烧更稳定，循环波动更小。 英文摘要: The advantages of ethanol cannot be fully utilized when ethanol is mixed with gasoline in a fixed proportion. To solve this problem, a system which can inject both ethanol and gasoline directly into cylinder was developed. With this system, the effects of three different injection strategies on combustion characteristics and engine performance under lean-burn condition were experimentally conducted on a spark ignition gasoline engine. The three injection strategies were: injecting gasoline and ethanol at the same time; fixing gasoline injection timing and delaying ethanol injection timing gradually; fixing ethanol injection timing and delaying gasoline injection timing gradually. The results show that with the three injection strategies engine power output and thermal efficiency increase first and then decrease with the delay of the injection timings under lean-burn condition. When the amount of injected fuel is kept constant, the effective thermal efficiency increases remarkably with the excess air coefficient, while the equivalent fuel consumption decreases gradually. The optimal combustion is obtained at the excess air coefficient of 1.2 and with the gasoline injection timing of 180° in crank angle before the top dead center and ethanol injection timing of 300° in crank angle before the top dead center. In this case, the effective thermal efficiency peaks to 40.5%. Besides, adding ethanol into gasoline makes lean-burn combustion more stable with less cycle variation.

中文摘要: 利用直径0.22 mm的单孔喷嘴高压共轨喷油器，以喷油器油量标定数据及控制参数为基础,采用高速相机成像技术在定容燃烧室内在等喷油量变喷油压力的前提下测量了着火点、着火滞燃期、燃烧持续期、火焰面积(AF)和火焰自然发光强度(SINL)的变化规律，对比研究了RP-3航空煤油、柴油碰壁喷雾的着火和燃烧特性。结果表明：在低喷油压力下着火点分布在离壁面较远的区域，在较高喷油压力下着火点位于壁面上，距喷油器中心线的距离随喷油压力的增加而增加，且RP-3航空煤油着火点距喷油器的距离比柴油更远。随着喷油压力的增加，RP-3航空煤油碰壁喷雾火焰的着火滞燃期先降低后增加，柴油碰壁喷雾火焰的着火滞燃期不断降低，且RP-3航空煤油具有更短的着火滞燃期。燃烧持续期随喷油压力的增加而降低，RP-3航空煤油的燃烧持续期比柴油短。喷油压力越高，火焰面积（AF）和自然发光强度（SINL）的变化速率越高，而AF和SINL的最大值及达到最大值所需的时间越小。与柴油相比，RP-3航空煤油的AF、SINL具有更高的变化速率，且AF、SINL的峰值更高，达到峰值的时间更短。 英文摘要: The ignition and combustion characteristics of wall-impinged kerosene(RP-3) and diesel spray were comparatively investigated under the condition of a fixed injection mass and different injection pressures and based on calibrated fuel injection quantity data and corresponding control parameters. Adopting a common rail nozzle with single-hole of 0.22 mm, the experiments were conducted in a constant volume combustion vessel to simulate diesel engine condition. Flame images were captured using a high-speed camera, and then the behaviors of ignition and combustion were processed. The variation laws of ignition position, ignition delay time, combustion duration, flame area(AF) and spatially integrated natural luminosity(SINL) of both wall-impinged fuel sprays were determined by analyzing the flame images. The results show that at low injection pressures, the ignition positions of both fuels are in the region that is far from the wall surface. At high injection pressures, the ignition positions of both sprays are on the wall surface, and are pushed farther away from the injector center-line with the increase of the injection pressures. The ignition positions of the kerosene spray are farther away from the injector center-line than those of the diesel spray. The ignition delay of the wall-impinged kerosene flames shortens first and then prolongs with the increase in the injection pressure, and that of the diesel flames reduces with the increased injection pressure. The kerosene RP-3 spray has a shorter ignition delay than the diesel spray. The combustion durations of both sprays are shortened with the increased injection pressures, but that of the kerosene RP-3 spray is shorter. Increasing the injection pressures enhances the variation rates of AF and SINL of both sprays, but the maximum values of AF and SINL and the time to reach them decreases. The kerosene RP-3 spray has higher variation rates of AF and SINL, greater values of the maximum AF and SINL, and shorter time to reach the maximum AF and SINL compared to the diesel spray.

中文摘要: 运用激光诱导荧光法（LIF）定量分析了缸内直喷汽油机单孔喷油器喷雾撞壁的二维油膜特性。研究发现：燃油在壁面上向油膜铺展的方向聚集，并在边缘形成较厚的油膜。高喷射压力有助于形成质量较小且厚度较薄的油膜，同时减小喷射脉宽能进一步降低燃油附壁率。增加撞壁距离能同时减小油膜质量和油膜面积，然而油膜的平均厚度并未减小，对油膜蒸发并没有明显的促进作用。将喷射角度从15°增加到45°能够显著减少油膜质量和平均厚度。 英文摘要: The two-dimensional oil film characteristics of the single-hole injector spray wall impingements in a direct injection gasoline engine were quantitatively analyzed by the laser induced fluorescence method. Results show that the fuel accumulates on the wall in the direction of oil film expansion and forms a thicker oil film on the edge. High injection pressure helps to form an oil film with a lower mass and a thinner thickness, while reducing the jet pulse width can further reduce the fuel adherence rate. Increasing the wall impingement distance can simultaneously reduce the oil film quality and the oil film area, but can not reduce the average thickness of the oil film, so there is no obvious promotion effect on the oil film evaporation. Increasing the spray angle from 15° to 45° can significantly reduce the oil film quality and average thickness.