柴油机气缸盖的热流耦合分析

对某柴油机气缸盖的热流体与热应力进行耦合分析.首先运用CFD(Computational FluidDynamics)分析软件SC/Tetra计算温度场及流场,然后将得到的节点温度映射到用于结构分析的网格,再用有限元分析软件进行结构的热应力计算.通过对结果的分析发现设计的气缸盖的缸盖鼻梁区温度偏高,且温度梯度较大,热应力集中,说明鼻梁区冷却效果差,易出现裂纹.因此该处为危险区域,应该视为重点研究对象.还发现水套进水口布置的不够合理,调整进水口布置将不但有利于降低第四缸处最高温度,还有利于改进鼻梁区冷却.     

柴油机气缸盖的模态分析

利用有限元法对柴油机气缸盖进行了模态分析,获得了气缸盖的基本振型和相关频率,与试验结果进行比较,两者有较好的一致性,因而可利用所建立的有限元模型完成气缸盖的动态响应分析及设计优化.     

Transient heat transfer studies on a diesel engine valve

Numerical calculations based on finite difference approximations are carried out to assess the transient thermal response of the inlet and exhaust valves of a Tata-Mercedes, six cylinder, four stroke, water cooled diesel engine with a compression ratio of 19.5 and a rated power output of 110 hp at 3000 rpm for three different engine loadings. A detailed analysis has been given for estimating the boundary conditions of the inlet and exhaust valves of an internal combustion engine. The problem has been extended by applying a thin ceramic insulation coating of 2 mm thickness at the valve plate. The isothermal distribution in the valve bodies and the heat flow rates through the various cooling media for three different engine loadings have been depicted for each of the cases with and without insulation coating. The results indicate a reduction in heat loss through valves by use of an insulation coating on the valve plate.     

Experimental evaluation of waste plastic oil and its blends on a single cylinder diesel engine

Journal of Mechanical Science and Technology - The aim of the present work to investigate the performance of oil derived from the waste plastic on diesel engine. Waste plastic fuel (WPF) is derived...     

Corrosive wear of diesel engine cylinder bore

Deleterious wear of the cylinder bore in diesel engines can be aggravated by alteration of combustion conditions, such as that brought about by use of Exhaust Gas Recirculation (EGR) equipment and consequent high mileage. This paper describes the influence of combustion products — i.e. sulphuric acid and carbon soot, which can be primarily concerned in corrosive wear — on lubrication under reciprocating sliding of a piston ring and on the bore wear.     

船用柴油机气门导管与缸盖压装过程的研究与优化

柴油机缸盖是组成船用柴油机的核心部件之一,气门导管是柴油机气门的导向装置,其准确完成装配才能确保气门能够准确无误地做直线往复运动,气门导管与缸盖之间一般采用过盈联接,因此保证气门导管与缸盖的装配质量是十分重要的。主要分析了在不同过盈量的条件下,气门导管与缸盖装配过程中的压装力及由其引起的应力与位移变化情况,并以被包容件气门导管的内径作为优化参数进行优化,在满足实际工作要求的条件下,设计出最优的气门导管内径尺寸,得到二者过盈配合时的最佳配合尺寸,为气门导管以最小的压装力、应力和最佳过盈量压入缸盖内提供了理论参考,指导实际生产。     

四缸柴油机机体结构强度及缸套变形分析

以某四缸柴油机机体组合件为对象,对机体、气缸盖、气缸套、油底壳等多个零件、部件的组合件进行了全面的有限元分析和结构改进.在机体组合件强度分析的基础上,深入阐述了截面圆度、漏光率、圆柱度、同轴度、连续13个截面最小半径等气缸套变形评价指标的意义.并且运用这些指标对原方案及改进方案进行分析比较,得出以下结论:改进方案降低了原方案中偏高的机体隔板应力,降幅达32%已处于安全水平;改善了气缸套的变形,可以有效地提高发动机排放性能.     

基于CFD的风冷摩托车发动机气缸体的传热仿真研究

针对单缸风冷摩托车发动机气缸体的传热问题,基于热力学第一定律建立了进气过程中气缸壁传热量的数学模型,分析了气缸周壁的传热方式,通过CAD三维软件建立了发动机气缸体的三维模型,并进行计算网格划分,给定边界条件,应用计算流体力学( CFD)软件对发动机气缸体传热过程进行数值模拟计算,得出气缸体的温度分布图,从而获得气缸壁传给进气气体的热量值,为进一步研究摩托车发动机气缸体的传热问题提供参考.     

Experimental investigation on the influence of engine operating conditions on combustion and nanoparticle emission characteristics of a small DI diesel engine

The influence of variations in engine speed, injection pressure, injection timing, and multiple injection strategies on the combustion and nanoparticle characteristics of a small Direct injection (DI) diesel engine was experimentally investigated. To measure the size distribution and number concentration of particle emissions, a rotating disk thermo-diluter (dilution system), a Condensation particle counter (CPC), and a Scanning mobility particle sizer (SMPS) were used. The injection pressure was changed from 60 MPa to 120 MPa, at an engine speed of 1200 rpm. Injection timing was varied from Before top dead center (BTDC) 40˚ to Top dead center (TDC). To investigate the effect of multiple-injection strategies, the injection strategies consisted of two pulse signals with different dwell time. The experimental results show that the peak combustion pressure and Rate of heat release (ROHR) profile are increased and ignition delay is shortened with the increase of injection pressure from 60 MPa to 120 MPa. The concentration of soot emission for 120 MPa is lower than that of 60 MPa at advanced injection timing from TDC up to BTDC 25°. As the injection timing advances to over BTDC 30°, soot emissions rapidly increase and the high injection pressure case (120 MPa) creates more emissions than the 60 MPa case. The overall trends of total particle number are relatively increased with high injection pressure for single injection conditions. In the advanced injection timings of over BTDC 30°, the trend of total particle number is high for all injection pressures. For multiple injections, the peak combustion pressures and ROHR of multiple-injection strategies are slightly lower compared with those of single-combustion results. Comparing the multiple injection strategies, soot emission is reduced with the retard of second injection timing (-30°+5°). The overall trends of particle size and total number for the 7 mg+3 mg case revealed the lowest level compared with other cases, which is 50% lower than that for the 5 mg+5 mg case. When compared with single injection results, the total particle number and Dp of multiple injection cases were eventually lower.

     

Analysis of engine temperature and energy flow in diesel engine using engine thermal management

Recently, precise analysis of energy flow in engines has become necessary to improve fuel economy. An integrated engine thermal management model, which is introduced in this paper, is suitable for that process. The model consists of six sub-models for thermal mass, coolant, lubricant, heat transfer, friction, and exhaust. The sub-models are coupled to each other and they exchange heat and signals. Combustion energy flow analysis and temperature estimation of the engine components and working fluids were simulated under various conditions. Simulation results were compared with experimental data and they showed good agreement. Then, a variable-speed water pump (VSWP) to control coolant flow was applied in place of a conventional water pump. Engine warm-up time decreased with proper coolant flow control, and fuel economy could be improved by 2.5%.     

柴油机缸套断裂故障的原因分析及对策

针对实习中所见一台柴油发动机气缸套断裂的故障，结合该发动机的结构特点，归纳整理出产生故障的原因，并提出相应的故障诊断和排除方法。     

Experimental investigation for the optimization of heat pipe performance in latent heat thermal storage

We investigated the optimum performance of heat pipe in Latent heat thermal energy storage (LHTES), and compared it with copper pipe. Classical plan of experimentation was used to optimize the parameters of heat pipe. Heat pipe fill ratio, evaporator section length to condenser section length ratio i.e., Heat pipe length ratio (HPLR) and heat pipe diameter, was the parameter used for optimization, as result of parametric analysis. Experiment with flow rate of 10 lit./min. was conducted for different fill ratio, HPLR and different diameter. Fill ratio of 80 %, HPLR of 0.9 and heat pipe with diameter of 18 mm showed better trend in charging and discharging. Comparison between the storage tank with optimized heat pipe and copper pipe showed almost 186 % improvement in charging and discharging time compared with the copper pipe embedded thermal storage. Heat transfer between Heat transferring fluid (HTF) and Phase change material (PCM) increased with increase in area of heat transferring media, but storage density of storage tank decreased. Storage tank with heat pipe embedded in place of copper pipe is a better option in terms of charging and discharging time as well heat storage capacity due to less heat lost. This justifies the better efficiency and effectiveness of storage tank with embedded optimized heat pipe.     

重型柴油机气缸套变形数值模拟及分析

运用有限元法计算得到某150柴油机气缸套三维温度场的分布,在此基础上计算了缸套在预紧工况和爆发两种情况下的受力变形情况.结果显示缸套最高温度为240℃,出现在缸套活塞上止点附近;考虑热负荷后,缸套的应力及变形要明显比未加载的情况下大得多,说明了对缸套的变形进行分析的时候考虑热载荷作用的必要性.     

单缸柴油机配气机构动力学仿真研究

应用虚拟样机技术和有限元技术对某型柴油机配气机构的动力学特性进行了仿真研究。采用了先建立实体模型和构件的有限元模型、后导入虚拟样机软件构建多体动力学分析模型的思路,建立了配气机构刚柔耦合的多体动力学分析模型,并对气门加速度、凸轮挺柱间作用力等性能指标进行了仿真分析,分析结果也通过气门加速度试验得到验证。与应用广泛的多刚体模型相比,该耦合模型能够更好地反映气门、推杆等零件的刚度、阻尼变化,计算精度更高。同时,该分析结果对于进一步的分析和优化也具有一定的参考价值。     

An analytical study on the performance analysis of a unit-injector system of a diesel engine

A numerical algorithm is developed to analyze the performance of a Unit-injector (UI) System for a diesel engine. The fundamental theory of the algorithm is based on the continuity equation of fluid dynamics. The loss factors that should be seriously regarded on the continuity equation are the compressibility effect of liquid fuel, the wall friction loss in high-pressure fuel lines of the system, the kinetic energy loss of fuel in the system, and the leakage of fuel out of the control volume. For an evaluation of the developed simulation algorithm, the calculation results are compared with the experimental outputs provided by the Technical Research Center of Doowon Precision Industry Co. (DPICO); the maximum pressure in the plunger chamber (P _p ) and total amount of fuel injected into a cylinder per cycle (Q_f) at each operational condition. The result shows that the average error rate (%)of P _p andQ _f are 2.90% and 4.87%, respectively, in the specified operational conditions. Hence, it can be concluded that the analytical simulation algorithm developed in this study can be reasonably applied to the performance prediction of newly designed UI system.     

基于模糊熵的16V280ZJA型柴油机缸盖螺栓的可靠性优化设计

缸盖螺栓工作的可靠性将严重影响柴油机运动件的整体动平衡、功率及油耗状况。将模糊设计与优化设计理论相结合,并引入熵理论,整理并推导出柴油机缸盖螺栓可靠性优化设计数学模型,通过Matlab编程实现数值解的计算及图形输出。该方法在DF8B型货运内燃机车装用的16V280ZJA型柴油机上进行了实例设计,结果表明,该方法设计的螺栓比原设计方案的质量减小了55.56%,优化效果十分明显。     

Experimental investigation of heat and mass transfer in absorber with enhanced tubes

In this paper, an experimental study of the absorption process of water vapor into lithium bromide solution is reported. For the purpose of developing high performance absorption chiller/heater utilizing lithium bromide solutions as working fluid, it brings the largest contribution to improve the performance of the absorber which normally requires the largest surface area among the four heat exchangers of the system. The performance of four types of absorber tubes; bare tube, bumping bare tube, floral tube and twisted floral tube, have been experimentally evaluated. The results show that the floral tube and the twisted floral tube show about 40% higher heat and mass transfer performance than the bare tube which is conventionally used in absorbers.     

发动机缸体缸盖的消失模铸造技术

消失模铸造技术是一种利用泡沫模样代替传统复杂造型过程实现零件生产的铸造工艺。近二十年来,消失模铸造广泛应用于具有复杂结构零件的铸造,通常情况,铸件越复杂越能体现该工艺的优越性。20世纪90年代,美国成功地将消失模铸造技术应用于发动机缸体缸盖的工业化生产,使得零件设计更为柔性、集成度高,减轻铸件重量,提高燃油效率,降低成本;目前我国企业尝试用消失模铸造技术小批量生产缸体缸盖,初步获得成功,开始走向市场,但由于受到增碳、气孔等铸造缺陷的困扰,还未能实现低废品率的大批量工业化生产。     

Real-time diagnostic system using acoustic emission for a cylinder liner in a large two-stroke diesel engine

Damage that originates from abnormal wear in the cylinder liner of marine diesel engines causes a considerable loss of property to manage shipping vessels. However, because multiple factors contribute to such damage, it is difficult to anticipate the damage that is caused by abnormal wear, such as scuffing, by investigating the mechanism of abnormal wear. Therefore, several methods have been explored for predicting the abnormal wear between the cylinder liner and the piston ring in marine diesel engines. For example, methods that are based on an analysis of the temperature, vibration, or cylinder drain oil have been researched. However, the response time of such methods is too slow for an operator to have enough time to promptly cope with severe damage. The implementation of such methods also requires prior modifications to the engine, which cost time and money. To overcome such problems, methods of prediction that use AE (acoustic emission) have been widely investigated. Studies on the relationship between abnormal wear and AE signals have demonstrated that severe damage is preceded by a change in the RMS value of AE and the FFT amplitude of a specific frequency. However, previous studies on the AE technique were based on the offline analysis of stored data due to their focus on the relationship between abnormal wear and AE signals. Thus, for direct implementation of the AE technique in industry, a real-time diagnostic system is needed. This paper focuses on the development of a real-time diagnostic system for analyzing high speed AE signals and examining the wear status of cylinder liners in marine diesel engines.     

Influence of load on the tribological conditions in piston ring and cylinder liner contacts in a medium-speed diesel engine

The present work is an attempt to determine the oil film thickness in a medium-speed four-stroke diesel engine with a cylinder diameter of 200 mm. Experimental research on this topic was found necessary due to the limited amount of published information available with reference to engines of the present size. The experimental part of the study was carried out as firing engine tests, with an instrumented piston, equipped with telemetric data transmission, and an instrumented cylinder liner in a 6-in-line test engine. The study was carried out for different parts of the four-stroke working cycle and for different levels of engine power output. The results were compared with the results of computer simulations, carried out using a commercial software package. The conclusions of the study comprise aspects on the formation and development of the oil film between the rings and the liner under a set of load levels together with the periodical fluctuation during different strokes of the working cycle.