中文摘要: 基于台架试验和完整工作循环数值模拟，开展了汽油机活塞头部形貌特征对爆震的敏感性研究。以台架试验数据为基准校正了汽油机性能仿真模型，通过开展压缩比为9~16区间的外特性仿真模拟，得出压缩比为12时外特性最优。在压缩比为12的3500 r/min全负荷工况，采用化学反应动力学离子分析法，通过数值模拟分析3类基于活塞头部形貌方案的燃烧室，得出具有点火驻涡区域、气门避障区域、驻涡与避障区域之间的连通区域、后部连通区域的SABCD方案抗爆性最优，并指出活塞头部形貌特征中的连通区域对爆震敏感性具有显著影响。通过对方案SABCD的连通区域关键参数进行优化得出，当区域连通宽度和连通台阶高度均为4 mm时爆震敏感性最低。研究结果表明，通过对活塞头部形貌特征的合理设计，能实现提升汽油机压缩比的同时有效抑制燃烧室对爆震的敏感性。 英文摘要: Based on the bench test and the numerical simulation over a complete working cycle, the effect of the piston head shape of a gasoline engine on detonation sensitivity was studied. By using the bench test data as the benchmark to correct the performance model of the gasoline engine, the mapping simulation for the compression of 9 to 16 was used to obtain an optimal engine map with a compression ratio of 12. The combustion characteristics of three different piston head shaped combustion chambers was analyzed by numerical simulation using the chemical reaction kinetics ion analysis method at the speed of 3500 r/min and full load with a compression ratio of 12, which shows that the SABCD scheme with rear-connected standing vortex connection channel on the piston head has the best anti-detonation properties, and the connection channel between the ignition standing vortex region and valve obstacle avoidance region has a significant impact on detonation sensitivity. By optimizing the key parameters of connection channel of the SABCD scheme, the detonation sensitivity of the piston head is the lowest when the width and depth of the connection channel are both 4 mm. Research results show that a reasonable design of the piston head shape can effectively suppress the combustion chamber's sensitivity to detonation,while increasing the compression ratio of the gasoline engine.

中文摘要: 为解决柴油发动机在高转速、低负荷工况下难以准确判断出发生失火故障的气缸的问题，提出了通过检测曲轴转速信号中的扭振信号起始点来判定失火气缸的故障诊断方法。该方法首先通过分析单缸失火时的转速信号以确定曲轴扭振的自由频率，然后基于该频率构造正弦检测信号，将该检测信号与各缸做功转角范围内的转速信号做内积运算，并得到的内积值作为失火气缸的指示特征。在6缸柴油机上的失火试验证明该方法能够在高转速低负荷情况下准确识别发动机的单缸失火和两缸失火，弥补了传统失火诊断方法工况覆盖率低的不足。 英文摘要: To handle the difficulty of judging fault cylinders in diesel engine misfire failure under high speed and low load conditions, a method that locates fault cylinders by detecting the start of crankshaft torsional vibration in rotation speed signal was proposed. With analyzing the rotation speed signal pattern in single-cylinder misfire, this method first determined the natural frequency of crankshaft torsional vibration, through which a sine vibration detecting signal was built. Then, the inner product of the detecting signal and speed signal during the working stroke of each cylinder was calculated and used as the indicator of fault cylinder. The proposed method was proven by a misfire experiment on a six-cylinder diesel engine to be able to diagnose with high accuracy single-cylinder and double-cylinder misfire faults under high speed and low load conditions, extending the diagnosing scope that the conventional methods cannot cover.

中文摘要: 内燃机工作时依赖冷却系统将多余热量及时带走以保证燃烧室核心部件及润滑油膜的正常工作温度。常规内燃机冷却介质导热系数偏低，而新一代强化传热工质纳米流体具有明显提升的传热性能，应用于内燃机冷却系统有利于强化内燃机传热及提高热管理性能。且由于纳米流体的传热性能受纳米粒子的种类、大小、浓度、形状等因素影响，可以通过改变这些因素控制内燃机冷却水腔的传热量。综述了国内外研究者针对纳米流体导热系数与对流换热性能开展的试验测试、理论分析和计算机模拟研究工作，以及纳米流体应用于内燃机冷却系统中强化传热的进展，最后指出当前研究工作的不足及未来工作方向。 英文摘要: Internal combustion engine relies on its cooling system to take away the excess heat and control the normal operating temperatures of the core components of the combustion chamber and the lubricating oil film, wherein the heat transfer performance of the conventional cooling mediums is generally low. Nanofluids, as the new generation of enhanced heat transfer working medium, has good heat transfer performance, which is ideal for the cooling system of internal combustion engine to use it to enhance heat dissipation and improve thermal management performance. Moreover, because the heat transfer performance of the nanofluids is affected by factors such as the type, size, concentration and shape of the nanoparticles, the heat transfer amount of the cooling water chamber of the internal combustion engine can be controlled by changing these factors. This paper reviews the experimental, theoretical and computer simulation studies conducted by researchers on the thermal conductivity and convective heat transfer performance of nanofluids, as well as the application of nanofluids in enhancing heat transfer of internal combustion engine. Finally, it points out the shortcomings of the current research work, and the future work directions.

中文摘要: 为探究催化型柴油机颗粒捕集器（catalytic diesel particulate filter， CDPF）的再生性能，自制了CDPF颗粒加载装置，通过模拟气试验平台研究了炭载量、再生温度及气体流量对CDPF再生性能的影响，并对其再生效率、再生效能比、最高温度及最高温度梯度性能指标进行评价。试验结果表明：CDPF再生过程主要有两个阶段，第一个阶段主要发生在250~400 ℃之间，为低温长时间再生阶段；第二个阶段主要发生在500~600 ℃之间，为高温短时间再生阶段。当再生温度为350 ℃、气体流量为200 mL/min时，3.2 g/L、5.0 g/L和7.0 g/L 3种炭载量下的最高温度梯度均达到最小，分别为2737.5 ℃/m、4387.5 ℃/m和3837.5 ℃/m。其再生效率在再生温度为250 ℃时均约为6.0%，而在550 ℃时均达到85.6%。当炭载量为5.0 g/L，再生温度为500 ℃和550 ℃，气体流量为300 mL/min时，最高温度、最高温度梯度及再生效率均达到最大，再生效能比随气体流量的增大从4.6×10-5 J-1下降到1.8×10-5 J-1。 英文摘要: In order to explore the regeneration performance of catalytic diesel particulate filter(CDPF), an in-house-made CDPF carbon particle loading device was developed. The effects of carbon loading, regeneration temperature and gas flow rate on the regeneration performance of CDPF were studied through a simulated gas test platform, and the regeneration efficiency, regeneration efficiency ratio, maximum temperature and maximum temperature gradient were evaluated. The results show that there are two main stages in the CDPF regeneration. The first stage mainly takes place between 250 ℃ and 400 ℃, which is a long regeneration at low temperatures; the second stage mainly occurrs between 500 ℃and 600 ℃, which is a short regeneration at high temperatures. When the regeneration temperature is 350 ℃ and the gas flow rate is 200 mL/min, the maximum temperature gradients of 3.2 g/L, 5.0 g/L and 7.0 g/L carbon loading are the smallest, being 2737.5 ℃/m, 4387.5 ℃/m and 3837.5 ℃/m respectively. The regeneration efficiency is about 6% at 250 ℃, and 85.6% at 550 ℃. When the carbon loading is 5.0 g/L, the regeneration temperature is 500 ℃ and 550 ℃ and the gas flow rate increases to 300 mL/min, the maximum temperature, the maximum temperature gradient and the regeneration efficiency all reach the highest, and the regeneration efficiency ratio decreases from 4.6×10-5 J-1 to 1.8×10-5 J-1 with the increase in the gas flow rate.

《内燃机工程》2020年第2期目次

目次

《内燃机工程》2020年第1期目次

中文摘要: 针对强噪声干扰下柴油机失火故障难以诊断的问题，提出一种基于变分模态分解（variational mode decomposition, VMD）与交叉小波变换（cross wavelet transform, XWT）的柴油机失火故障诊断方法。该方法首先通过VMD将缸盖振动信号进行分解、自适应消噪及信号重构，再利用XWT对任意两个连续工作循环信号进行时频相关分析，进一步消除振动信号中的干扰噪声以提取柴油机燃烧特征，最后通过计算时频空间各缸能量占比进行柴油机失火故障诊断。通过对仿真信号分析及柴油机失火故障诊断，结果表明：该方法可以消除强噪声干扰，提取柴油机燃烧周期瞬态振动冲击特征，有效地识别柴油机失火故障。 英文摘要: Aiming at the problem that diesel engine misfire is difficult to diagnose under strong noise interference, a diesel engine misfire fault diagnosis method based on variational mode decomposition(VMD) and cross wavelet transform(XWT) is proposed. Firstly, cylinder head vibration signal is decomposed, denoised and reconstructed by VMD, and then the time-frequency correlation analysis on any two consecutive operating cycle signals is carried out by using XWT to extract the diesel combustion features after eliminating the interference noise in the vibration signal, and finally the diesel engine misfire fault diagnosis is performed by calculating the energy ratio of each cylinder in the time frequency space. Simulation and analysis results show that the method can eliminate the strong noise interference, extract the transient vibration shock features in diesel engine combustion cycle and effectively identify the diesel engine misfire fault.

中文摘要: 对大功率发电柴油机选择性催化还原（selective catalytic reduction,SCR）尿素喷雾锥角进行研究。运用计算流体动力学（computational fluid dynamics,CFD）软件模拟了4种不同喷雾锥角尿素混合管内的结晶风险和NH3 分布均匀性,通过分析仿真结果,优选出60°和70°两种喷雾锥角的尿素喷嘴。使用选定的喷雾锥角进行结晶对比试验和性能对比试验。结晶对比试验结果显示,60°喷雾锥角的结晶风险明显低于70°喷雾锥角的结晶风险。性能对比试验结果显示,两种喷雾锥角的NOx 转化效率基本一致。综合分析仿真结果与试验结果,最终将SCR系统的尿素喷雾锥角优化为60°。 英文摘要: The urea spray cone angle of a selective catalytic reduction (SCR) system used on a high-power generating set diesel engine was studied. The crystallization risk and NH3 distribution uniformity in an urea mixing pipe with 4 different spray cone angles were simulated by a computational fluid dynamics software. Through the simulation analysis, two kinds of urea nozzles with spray cone angles of 60° and 70° were selected for the crystallization contrast test and performance comparison test. The results of the crystallization contrast test show that the crystallization risk of the 60° spray cone angle is obviously lower than the 70° spray cone angle. The performance comparison test indicates that the NOx conversion efficiencies of the two spray cone angles are basically the same. After the comprehensive analysis of the simulation calculations and test results, the urea spray cone angle of the SCR system is finally optimised to 60°.

中文摘要: 基于弹流润滑（elastic hydrodynamic lubrication，EHL）和粗糙峰接触理论及平均流量模型，建立了某连杆小头摆动摩擦副柔性多体动力学模型，分析研究了抛物型线、双曲型线和锥度型线3种衬套型线对连杆小头摆动摩擦副润滑及变形匹配的影响。结果表明：抛物型线与双曲型线的润滑和变形特性都要优于无型线；而锥度型线润滑性能变差，变形特性能得到提升；综合来看，切削量为6μm的双曲型线对连杆小头衬套润滑和变形匹配的综合改善效果较好。 英文摘要: Based on the theory of elastic hydrodynamic lubrication and rough peak contact and the average flow model, a flexible multi-body dynamics model of the swinging friction pair of a connecting rod small end bushing was established, and the effect of the different profiles of the bushings, including parabolic, hyperbolic and tapered profiles, on lubrication and deformation of their swinging friction pairs was analyzed. Results show that compared with plain type bushing, the bushings with parabolic or hyperbolic profiles have better lubrication and deformation characteristics, while the bushing with a tapered profile has poor lubricity, but its deformation characteristics is better. In summary, use of hyperbolic profile with a cutting amount of 6 um can greatly improve the comprehensive characteristics of lubrication and deformation of the connecting rod small end bushings.