The performance and particulate emission of a diesel engine are affected by the consumption of lubricating oil. Most studies on oil consumption mechanism of the cylinder have been done by using the experimental method...The performance and particulate emission of a diesel engine are affected by the consumption of lubricating oil. Most studies on oil consumption mechanism of the cylinder have been done by using the experimental method, however they are very costly. Therefore, it is very necessary to study oil consumption mechanism of the cylinder and obtain the accurate results by the calculation method. Firstly, four main modes of lubricating oil consumption in cylinder are analyzed and then the oil consumption rate under common working conditions are calculated for the four modes based on an engine. Then, the factors that affect the lubricating oil consumption such as working conditions, the second ring closed gap, the elastic force of the piston rings are also investigated for the four modes. The calculation results show that most of the lubricating oil is consumed by evaporation on the liner surface. Besides, there are three other findings： （1） The oil evaporation from the liner is determined by the working condition of an engine; （2） The increase of the ring closed gap reduces the oil blow through the top ring end gap but increases blow-by; （3） With the increase of the elastic force of the ring, both the left oil film thickness and the oil throw-off at the top ring decrease. The oil scraping of the piston top edge is consequently reduced while the friction loss between the rings and the liner increases. A neural network prediction model of the lubricating oil consumption in cylinder is established based on the BP neural network theory, and then the model is trained and validated. The main piston rings parameters which affect the oil consumption are optimized by using the BP neural network prediction model and the prediction accuracy of this BP neural network is within 8%, which is acceptable for normal engineering applications. The oil consumption is also measured experimentally. The relative errors of the calculated and experimental values are less than 10%, verifying the validity of the simulation results. Applying the established simulation model and the validated BP network model is able to generate numerical results with sufficient accuracy, which significantly reduces experimental work and provides guidance for the optimal design of the piston rings diesel engines.展开更多
为进一步提升在负压工况下动车组齿轮箱轴端密封性能,基于传统甩油环复合密封(OSRCS)结构,在甩油环外侧增加肋板和外缘倾角,提出一种新型动车组齿轮箱轴端肋板甩油环复合密封(Ribbed Oil-Slinging Ring Composite Seal,ROSRCS)结构。通...为进一步提升在负压工况下动车组齿轮箱轴端密封性能,基于传统甩油环复合密封(OSRCS)结构,在甩油环外侧增加肋板和外缘倾角,提出一种新型动车组齿轮箱轴端肋板甩油环复合密封(Ribbed Oil-Slinging Ring Composite Seal,ROSRCS)结构。通过计算流体力学(CFD)方法研究ROSRCS的泄漏特性,探究ROSRCS在不同甩油环倾角、外缘倾角、肋板数目和高度下的密封性能表现。结果表明:在特定的工况下,ROSRCS的密封性能明显优于OSRCS,润滑油泄漏率减少5.7%。当甩油环倾角为35°时,ROSRCS流场中湍流耗散中心向齿轮箱内部移动,与OSRCS相比,ROSRCS最大湍流耗散强度提高22.56%。合适的外缘倾角可明显增强甩油环外缘处射流强度,湍流耗散强度最大值提升9.21%。虽然甩油环增加肋板会在肋板根部形成负压区从而降低了ROSRCS的回油能力,但合适的肋板设置可通过改变涡流的数量、位置和强度,从而有效提升动车组齿轮箱轴端密封性能。展开更多
In order to prepare the polyol with all bio-based components as raw materials,cottonseed oil was first epoxidized by peroxyformic acid generated in situ from hydrogen peroxide and formic acid,and the cottonseed oil ba...In order to prepare the polyol with all bio-based components as raw materials,cottonseed oil was first epoxidized by peroxyformic acid generated in situ from hydrogen peroxide and formic acid,and the cottonseed oil based polyols with variable hydroxyl value were then prepared by the ring-opening of epoxidized cottonseed oil with sorbitol,which is a multi-functional hydroxyl compound derived from a natural source.The chemical structure of the products was characterized with FTIR analysis, and the residual epoxy oxygen content and hydroxyl value of the polyol versus the ring-opening time were investigated.展开更多
基金supported by National Natural Science Foundation of China (Grant No. 50975192)Specialized Research Foundation for the Doctoral Program of Higher Education of China (Grant No.20090032110001)
文摘The performance and particulate emission of a diesel engine are affected by the consumption of lubricating oil. Most studies on oil consumption mechanism of the cylinder have been done by using the experimental method, however they are very costly. Therefore, it is very necessary to study oil consumption mechanism of the cylinder and obtain the accurate results by the calculation method. Firstly, four main modes of lubricating oil consumption in cylinder are analyzed and then the oil consumption rate under common working conditions are calculated for the four modes based on an engine. Then, the factors that affect the lubricating oil consumption such as working conditions, the second ring closed gap, the elastic force of the piston rings are also investigated for the four modes. The calculation results show that most of the lubricating oil is consumed by evaporation on the liner surface. Besides, there are three other findings： （1） The oil evaporation from the liner is determined by the working condition of an engine; （2） The increase of the ring closed gap reduces the oil blow through the top ring end gap but increases blow-by; （3） With the increase of the elastic force of the ring, both the left oil film thickness and the oil throw-off at the top ring decrease. The oil scraping of the piston top edge is consequently reduced while the friction loss between the rings and the liner increases. A neural network prediction model of the lubricating oil consumption in cylinder is established based on the BP neural network theory, and then the model is trained and validated. The main piston rings parameters which affect the oil consumption are optimized by using the BP neural network prediction model and the prediction accuracy of this BP neural network is within 8%, which is acceptable for normal engineering applications. The oil consumption is also measured experimentally. The relative errors of the calculated and experimental values are less than 10%, verifying the validity of the simulation results. Applying the established simulation model and the validated BP network model is able to generate numerical results with sufficient accuracy, which significantly reduces experimental work and provides guidance for the optimal design of the piston rings diesel engines.
文摘为进一步提升在负压工况下动车组齿轮箱轴端密封性能,基于传统甩油环复合密封(OSRCS)结构,在甩油环外侧增加肋板和外缘倾角,提出一种新型动车组齿轮箱轴端肋板甩油环复合密封(Ribbed Oil-Slinging Ring Composite Seal,ROSRCS)结构。通过计算流体力学(CFD)方法研究ROSRCS的泄漏特性,探究ROSRCS在不同甩油环倾角、外缘倾角、肋板数目和高度下的密封性能表现。结果表明:在特定的工况下,ROSRCS的密封性能明显优于OSRCS,润滑油泄漏率减少5.7%。当甩油环倾角为35°时,ROSRCS流场中湍流耗散中心向齿轮箱内部移动,与OSRCS相比,ROSRCS最大湍流耗散强度提高22.56%。合适的外缘倾角可明显增强甩油环外缘处射流强度,湍流耗散强度最大值提升9.21%。虽然甩油环增加肋板会在肋板根部形成负压区从而降低了ROSRCS的回油能力,但合适的肋板设置可通过改变涡流的数量、位置和强度,从而有效提升动车组齿轮箱轴端密封性能。
文摘In order to prepare the polyol with all bio-based components as raw materials,cottonseed oil was first epoxidized by peroxyformic acid generated in situ from hydrogen peroxide and formic acid,and the cottonseed oil based polyols with variable hydroxyl value were then prepared by the ring-opening of epoxidized cottonseed oil with sorbitol,which is a multi-functional hydroxyl compound derived from a natural source.The chemical structure of the products was characterized with FTIR analysis, and the residual epoxy oxygen content and hydroxyl value of the polyol versus the ring-opening time were investigated.
