中文摘要: 为了获取两种脂肪酸酯类燃料棕榈酸甲酯和棕榈酸乙酯的热物理性质，并为将其作为燃料和燃料添加剂提供理论和试验数据支持，利用表面光散射法、振动管法和全反射法在较宽温区下分别研究了两种棕榈酸酯类的表面张力、黏度、密度和折射率。密度和折射率数据分别关联成了温度的多项式和线性函数，棕榈酸甲酯和棕榈酸乙酯的密度试验值与方程计算值平均绝对偏差分别为0.033%和0.013%，折射率试验值与方程计算平均偏差均为0.004%；黏度数据关联成了温度倒数的多项式，棕榈酸甲酯和棕榈酸乙酯的试验值与方程计算值平均绝对偏差分别为1.76%和2.30%；表面张力数据利用了van der Waals方程进行关联，棕榈酸甲酯和棕榈酸乙酯的试验值与方程计算值平均绝对偏差分别为0.86%和1.70%。 英文摘要: To provide theoretical basis and test data support for methyl palmitate and ethyl palmitate, which are two fatty acid esters, to be used as fuels or fuel additives in diesel engine, their thermophysical properties including surface tension, viscosity, density and refractive index were investigated in a wide temperature range by the surface light scattering, vibration tube and total reflection. The test data of the density and refractive index of both palmitates were correlated respectively as polynomial and linear functions of temperature. The average absolute deviations of density values calculated with the polynomial functions from the test data were 0.033% and 0.013% respectively, and both the average absolute deviations of refractive index values calculated with the liner function from the test data were 0.004%. The test data of the viscosities of both palmitates were correlated as polynomial functions of the reciprocal of temperature, and the average absolute deviations of these values calculated with the polynomial functions from the test data were 1.76% and 2.30% respectively. The test data of the surface tension of both palmitates were correlated as the van der Waals type functions, and the average absolute deviations of these values calculated with the van der Waals type functions from the test data were 0.86% and 1.70% respectively.

中文摘要: 使用格子玻尔兹曼方法对二维不混溶、不可压缩流体的Kelvin-Helmholtz（K-H）不稳定性进行数值模拟。以卷起高度 H 作为参考值，研究了密度比、表面张力、切应力对流体K-H不稳定性内产生Rayleigh-Taylor（R-T）不稳定性的影响。研究结果显示，密度比对两种不稳定性耦合起决定性作用。密度比接近1时，K-H不稳定性中不会产生R-T不稳定性，随着密度比增大，K-H不稳定性中开始产生R-T不稳定性。表面张力系数的增大对流体产生K-H不稳定性及两种不稳定性的耦合的卷起高度变化没有影响,但会对流体向内运动起抑制作用，且卷起流体的厚度明显增加。切应力对两种流体不稳定性的耦合起抑制作用。 英文摘要: By using the lattice Boltzmann method, the Kelvin-Helmholtz instability of two dimensional immiscible and incompressible fluids was numerically simulated. Taking the rolling height H as a reference value, the effects of density ratio, surface tension and shear stress on the appearance of Rayleigh-Taylor (R-T) instability in Kelvin Helmholtz(K-H) instability was studied. The results show that the density ratio plays a decisive role in the coupling effect of the two instabilities. When the density ratio is close to 1, the R-T instability does not occur in the K-H instability. When the density ratio increases, the R-T instability begins to occur in the K-H instability. An increase in the surface tension coefficient has no effect either on the K-H instability, or on the coupling height variation of the two instabilities, but it has an inhibitory effect on the inward movements of the fluids, and the thickness of the rolled fluid is significantly increased. The shear stress has an inhibitory effect on the coupling of the K-H instability and R-T instability.

中文摘要: 针对船用低速柴油机各缸和各循环间燃烧不平衡性问题，以6EX340EF型船用低速柴油机为研究对象，使用AVL Cruise M软件开发了具有各缸和各循环间的压力波动功能且满足准确性和实时性要求的仿真模型；结合NI CompactRIO硬件和NI LabVIEW软件，开发了缸压闭环控制快速原型，通过位置管理模块和缸压采集分析处理模块，从缸压数据中提取平均指示压力和50%燃烧放热量相位作为反馈变量，以喷油正时和喷油脉宽为控制变量，对缸压进行闭环控制；集成实时仿真模型、硬件在环仿真系统和快速控制原型，构成闭环系统。试验验证表明：开发的缸压闭环控制策略能够使燃烧特性参数波动减少50%左右，对各缸和各循环间的燃烧不平衡性均有改善效果。 英文摘要: Taking a 6EX340EF low-speed marine diesel engine as the research object, the issue of the combustion imbalance between the cylinders and working cycles of low-speed marine diesel engines was studied using the in-cylinder pressure feedback control technology. A simulation model with pressure fluctuations between the cylinders and working cycles was developed using the AVL Cruise M software to meet accuracy and real-time requirements, and a rapid control prototype was also developed based on the NI CompactRIO hardware and NI LabVIEW software. The closed-loop adjustment of the in-cylinder pressure was accomplished by using combustion characteristic parameters as feedback variables, such as indicated mean effective pressure and 50% combustion heat release phase extracted from the pressure in cylinder through position management module and cylinder pressure acquisition analysis processing module, and injection timing and injection pulse width as control variables. Then the real-time simulation model, hardware-in-loop simulation system and control prototype were integrated to form a closed-loop system. The test results show that the proposed in-cylinder pressure feedback control strategy can reduce the pressure fluctuation by about 50%, and it has an improvement effect on the reduction of the combustion imbalance between the cylinders and working cycles.

中文摘要: 以某3缸增压直喷汽油机正时皮带怠速低频噪声为研究对象，通过试验锁定噪声源和噪声频段，并对该噪声产生机理进行分析。针对该噪声源和噪声频段，通过一维动力学仿真的方法来优化正时皮带系统的布置参数，寻找到降低该噪声的方法，并最终通过噪声-振动-平顺性（NVH）试验验证了提高皮带刚度和增加小惰轮的方案能够有效降低该噪声。 英文摘要: The low-frequency noise of the timing belt of a three-cylinder turbocharged direct injection gasoline engine at idle speed was studied. The noise source and noise frequency spectrum were derived by test. The mechanism of noise generation was also analyzed. According to the obtained noise source and spectrum, the layout parameters of the timing belt system were optimized by the one-dimensional dynamic simulation. The method to reduce the noise was worked out and verified by noise vibration and harshness test. It is to increase the stiffness of the timing belt and add an idler.

《内燃机工程》2019年第5期目次

通过分析内冷油腔的振荡流动与传热相关物理过程以及对该过程进行的假设，基于相对位移法，提出了一种把内冷油腔看作刚体，采用随曲轴转角变化的边界条件和适当的初始条件的内冷油腔机油振荡流动与传热的仿真方法。以一款满足国V排放限值的高压共轨柴油机作为范例，建立了内冷油腔振荡流动与传热的计算流体力学仿真模型，详细阐述了以该方法建模的思路与过程，并对其计算结果进行了流动与传热分析。分析结果表明，该内冷油腔机油振荡流动与传热的仿真方法可以得到较稳定准确的结果；在相同发动机转速下，活塞的瞬时加速度和机油相对速度对机油的瞬态流动、机油分布以及瞬时充油率有直接影响，且内冷油腔各表面的瞬时面积平均换热系数有较大的差异，其出现峰谷值的数值与峰谷值对应的曲轴角度都有所差异；随着发动机转速增加，内冷油腔的瞬时充油率降低，但各壁面瞬时换热系数以相似的规律逐渐增加。

基于微型均质充量压燃(HCCI)自由活塞动力装置内自由活塞单次冲击过程，通过试验与数值模拟的方法，对比分析了甲烷掺混不同比例的CO2 时，混合气着火时刻、微燃烧室内的温度、压力以及装置做功能力的变化．结果表明：在初始当量比为0.5 时，甲烷中CO2的掺混使混合气着火时刻延迟、燃烧速率变慢，微燃烧室内的压力与温度峰值后移且降低，混合气体的爆燃现象得到改善．随着甲烷中CO2 掺混比的增加，混合气的着火与燃烧不断恶化，装置的做功能力不断减弱，同时装置所需的启动能量不断增加；当CO2掺混比达到40%时，自由活塞的速度增量减少2.67 m/s，平均有效指示压力减少0.584 MPa，同时装置所需的启动能量增加至0.182 4 J．当CO2 掺混比达到58%时，混合气无法被压燃，微动力装置不对外做功．在保证装置做功能力的基础上，甲烷掺混一定比例的CO2，微燃烧室内平均温度能够降低30～100 K，微动力装置可以降低对微燃烧室材料的依赖，实现低温燃烧．

为改善车用柴油机高海拔下瞬态工况涡轮迟滞、进气流量响应慢及油耗和碳烟排放增加等问题，利用GTPower建立高海拔单可变截面增压(VGT)二级可调增压柴油机仿真模型，研究了0、3.5 和5.5 km 海拔下等速加载和恒载加速两种瞬态工况VGT 叶片的调节特性，比较VGT 叶片3 种控制策略对柴油机瞬态特性的影响．结果表明：等速加载工况下，VGT 最优控制策略为加载初期保持VGT 叶片开度不变至加载中段，之后开度线性增加至加载后稳态工况对应开度；恒载加速工况下，加速初期开始增大VGT 叶片开度，至加载中段开度增加至最大转速对应开度，之后VGT 开度保持不变持续至加速结束的调节策略加速性能最好．二级可调增压柴油机高海拔加载、加速性能明显优于原机，5.5 km 海拔加载过程转矩平均提高了6.2%，加速过程达到最终稳定转速时间缩短了44.8%，体现了二级可调增压系统改善柴油机瞬态特性的优越性．

为了研究诱导激波对喷雾特性的影响，采用纹影法和仿真模拟的方法对不同喷射压力、不同环境介质条件下的喷雾和激波特性进行研究．结果表明：在相同喷射压力和环境密度下，在燃油喷射初期，存在激波条件下的喷雾贯穿距小于无激波条件下喷雾贯穿距，从仿真结果来看，在燃油喷射初期激波为附体激波，激波后环境气体密度和压力均大于激波前，激波后具有更大密度和压力的环境气体会阻碍喷雾的发展，从而导致贯穿距变小．在燃油喷射中后期激波与喷雾分离之后，存在激波条件的喷雾贯穿距则要高于无激波条件下的喷雾贯穿距．激波还可以增强燃油与空气混合程度，对增大喷雾体积有一定的促进作用，且促进效果会随着激波强度的增大而更加明显，有利于油、气混合气的形成．超高压喷射仿真结果表明，当喷射压力达到240 MPa 和320 MPa 时，喷射初期斜激波的末端会产生弓形激波，可以加剧湍流运动促进油、气混合，此外激波的产生使激波处环境气体温度升高，当喷射压力达到320 MPa时，激波处温度最多可升高16%，这有利于燃油的雾化蒸发．

提出了一种在复杂背景下燃油喷雾图像中前景油束轮廓提取的新算法，该算法包括油束前景区域预提取、油束轮廓细提取和油束轮廓修补3 个步骤．在油束前景区域预提取阶段，利用具有自适应阈值的帧间差分法和形态学填充处理提取出完全覆盖真实油束的前景区域．在油束轮廓细提取阶段，结合像素点在时间维度和空间维度上的信息对预提取获得的油束前景区域内的每个像素点进行多重判断，得到油束轮廓．在油束轮廓修补阶段，结合前景点修补阈值和油束横向、纵向位置边界条件对在视窗污染位置处的油束轮廓进行预测，结果表明：该算法能够精确地提取出处于复杂动态背景下的前景油束轮廓．