An experimental investigation on heat transfer performance of pulsating heat pipe

Journal of Mechanical Science and Technology - Heat input and inclination angle are essential factors influencing heat transfer performance of a pulsating heat pipe (PHP). The heat transfer...     

柴油发动机寿命实时预测系统的设计与实现

通过三通道传感器设计实现柴油发动机缸压力、机油压力和喷油压力数据的在线同步采集,并导入柴油发动机寿命预测数学模型,实现不解体的情况下动态测算柴油发动机的剩余寿命,判断发动机工作状态及何时需要进行发动机检修.实验表明在同一地区车辆行驶里程越大,预测提前量也越大;西藏地区的总体预测提前量大于广西地区的预测提前量.     

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CFX对管式换热器在烟气余热回收中的改进

通过对换热器结构特点的分析,提出在换热管外壁添加圆形翅片以此来提高管式空气换热器的余热回收。利用CFX软件模拟分析新型换热器的传热特性,通过分析翅片厚度、翅片间距、翅片高度得出,翅片厚度为0.8mm、翅片间距为3mm、翅片高度为12.5mm,换热器的换热性能最佳。     

Thermodynamic analysis of a dual loop cycle coupled with a marine gas turbine for waste heat recovery system using low global warming potential working fluids

Journal of Mechanical Science and Technology - The combined use of generation and propulsion gas turbines and steam turbines is efficient and can meet the environmental regulations. In this study,...     

An investigation of a heat pipe cooling system for use in turning on a lathe

A novel proposal is presented in this paper for reducing the thermal inaccuracy of turning on a lathe by removing the portion of the heat generated during the cutting process which is transferred to the carbide cutting insert by installing a heat pipe in the toolholder. The ability of the heat pipe to affect the temperature of the carbide cutting insert and the elongation of the toolholder is inferred from the response of thermocouples and strain gauges mounted on the toolholder to the heat generated during various cutting conditions. The results of the experimental investigation have proved the feasibility of the concept and recommendations have been made for continuing the research and improving the performance of the system.     

A tribological investigation of lubricant effects on bearing friction and fuel economy for passenger car engines and heavy duty diesel engines

Rising fuel costs and the need to conserve fossil fuel have led to increased interest in the role of lubricants in improving fuel economy. Crankshaft bearings can account for up to 40% of engine friction. Lubricant formulations can provide a beneficial reduction in engine friction, thus improving fuel economy. A unique journal bearing test rig has been developed to evaluate lubricants under transient and steady‐state conditions for passenger car engines and heavy duty diesel engines. The rig can measure bearing friction over a wide temperature, speed and load range. The rig uses production components and can be operated so as to produce the bearing pressures, lambda ratio and shear rates experienced by lubricants in fired engines. The properties of a range of lubricants of varying viscometrics, including Newtonian, non‐Newtonian and fully formulated oils have been evaluated. Significant differences due to formulation have been observed. The results of the study have been compared to fuel economy data generated from fired engines with the same lubricants as those tested in the journal bearing rig. Copyright © 2006 John Wiley & Sons, Ltd.     

Development of a 200 kW ORC radial turbine for waste heat recovery

Journal of Mechanical Science and Technology - There has recently been a growing interest in sustainable energy converters. One such technology is the organic Rankine cycle, which uses conventional...     

基于iSIGHT的变循环发动机性能优化

通过对变循环发动机结构形式和工作机理的分析研究,依照模块化合成程序的计算流程,给出了变循环发动机数学模型,利用面向对象的C++程序语言发展了基于部件类的变循环发动机数值仿真软件。利用商用软件iSIGHT的多学科优化能力,该仿真软件具有可视化操作界面,具备进行设计点的性能仿真计算、非设计点特性仿真计算以及设计点任务分析的仿真计算的能力。基于iSIGHT优化平台,对变循环发动机的性能进行了优化分析。     

3D heat transfer,lubrication and friction coupled study for piston ring-liner on diesel engines

The piston ring and liner of internal combustion engines are generally used under increasingly harsh conditions. To investigate the mechanisms affecting the work ineffective, the coupled heat transfer, lubrication and friction model between the piston ring and liner is proposed by coupling the gas, piston set-liner, lubrication film and coolant. In this model, the temperature variation of lubricant, the gas blowby, the surface roughness, the rupture position and the non-axial symmetry of oil film are considered. The coupled heat transfer, lubrication and friction simulation is carried out for 6110 diesel engine, and the temperature fields of piston set-liner along with the corresponding lubrication and friction curves are obtained. The simulated results are verified by comparing with the temperature experiment of piston.

     

集装箱船余热回收系统中温差发电模块的热电耦合分析

随着热电发电、热电制冷技术研究的不断深入,热电在船舶余热回收方面有了重大突破.以集装箱船余热回收系统中温差发电模块为研究对象,考虑了热电模块热端和冷端温度差存在温度变化的实际情况,运用ANSYS软件建立了热电单P-N结模型,分析了热电单元温度场的分布规律,得到了温差发电系统的输出特性,根据分析结果进行了温差发电模块用于...     

Investigation of waste heat recovery system at supercritical conditions with vehicle drive cycles

Waste heat recovery (WHR) for internal combustion engines in vehicles using Organic Rankine cycle (ORC) has been a promising technology. The operation of the ORC WHR system in supercritical conditions has a potential to generate more power output and thermal efficiency compared with the conventional subcritical conditions. However, in supercritical conditions, the heat transfer process in the evaporator, the key component of the ORC WHR system, becomes unpredictable as the thermo-physical properties of the working fluid change with the temperature. Furthermore, the transient heat source from the vehicle’s exhaust makes the operation of the WHR system difficult. We investigated the performance of the ORC WHR system at supercritical conditions with engine’s exhaust data from real city and highway drive cycles. The effects of operating variables, such as refrigerant flow rates, evaporator and condenser pressure, and evaporator outlet temperature, on the performance indicators of the WHR system in supercritical conditions were examined. Simulation of operating parameters and the boundary of the WHR system are also included in this paper.

     

Analysis upon fuel injection quantity variation of common rail system for diesel engines

Fuel injection quantity variation of common rail system has effect on the stability and reliability of diesel engines. For purpose of investigating the influence rule and mechanism of fuel injection quantity variation caused by parameters, taking account of the influence of fuel physical properties on dynamic injection characteristics of the system, a bond graph model of common rail injector has been proposed based on bond graph methodology and the state equations of the system are obtained. Comparisons between calculated fuel injection quantities by the numerical model and experimental measurements at different rail pressures and injection pulse widths indicate that the developed model can reasonably predict the fuel injection quantity characteristic of the system. Fuel injection quantity variation characteristics caused by the parameters of common rail injector have been analyzed in entire operating conditions. The selected parameters are delivery chamber diameter, needle seat semi-angle, needle cone semi-angle, ball valve seat semi-angle, nozzle hole diameter, inlet orifice diameter and outlet orifice diameter. The variation rules of quantitative percentages are obtained by quantitative analysis upon fuel injection quantity variation influential factors. It is concluded that ball valve seat semi-angle, nozzle hole diameter, inlet orifice diameter and outlet orifice diameter have the most significant effect on fuel injection quantity variation, and the followed are delivery chamber diameter and needle seat semi-angle. In addition, needle cone semi-angle also results in the variation of fuel injection quantity, but the effect is insignificant.

     

Exergo-economic analysis of finned tube for waste heat recovery including phase change heat transfer

In this paper, an exergo-economic criterion, i.e. the net profit per unit transferred heat load, is established from the perspective of exergy recovery to evaluate the performance of finned tube used in waste heat recovery. Also, the dimensionless exergy change number is introduced to investigate the effect of the flow (mechanical) exergy loss rate on the recovered thermal exergy. Selecting R245fa as a working fluid and exhaust flue gas as a heat source, the effects of the internal Reynolds number Re _i, the external Reynolds number Re _o, the unit cost of thermal exergy ? _q, the geometric parameter of finned tube η _o β and the phase change temperature T _v etc. on the performance of finned tube are discussed in detail. The results show that the higher T _v and η _o β, and lower Re _i may lead to the negligible flow (mechanical) exergy loss rate. There exists an optimal value of Re _i where the net profit per unit transferred heat load peaks, while the variations of Re _o, ? _q and T _v cause monotonic change of the net profit per unit transferred heat load. The phase change temperature exerts relatively greater influence on the exergo-economic performance of finned tube in comparison with other parameters. And there exists a critical phase change temperature, where the net profit per unit transferred heat load is equal to zero.     

Piston rings for slow and medium speed diesel engines: Aspects of manufacture and performance

The manufacture of piston rings for slow and medium speed diesel engines is a strange mixture of art and science whose final arbiter, the engine, is critical in its judgement of success or failure. Piston ring design is a delicate balance of tribology, practice, and manufacturing techniques, yet the piston ring is the least understood of all the components in a diesel engine, and the one most often found in practice to bear the brunt of the development problems of modern highly rated diesel engines. This paper presents a selection of some of the more practically orientated principles of the successful manufacture of grey cast iron piston rings greater than 175 mm in diameter, and shows that when considered with the sciences of strength of materials and diesel engineering, the subject of piston rings is almost an embodiment of the wider subject of tribology     

机车柴油机组合活塞的温度场数值模拟

应用PRO/E软件对复杂的16v280zjA型柴油机活塞建立三维实体模型,确定活塞的换热边界条件,并借助于软件PRO/EMechanica计算出活塞在热载荷作用下的温度场,计算结果与实测结果基本相吻合.明确了活塞在工作过程中活塞关键部位的温度分布状况,对于工程技术人员来说,了解活塞的温度场具体分布,进而可以求得活塞的应力分布、变形分布情况,为进一步改进组合活塞的结构设计具有一定的参考价值.     

Design of an optimal idle speed controller for a turbocharged diesel engine using fuzzy logic method

Idle Control of Internal Combustion Engines (ICEs) is one of the most important modules of Engine Management Systems (EMS) due to its effects on fuel consumption (FC) and pollutions produced in urban traffics. PID controllers are usually used for idle speed regulation. In this paper a PID like fuzzy controller is used to control the idle speed. The aim of this research is to introduce the selection method of membership functions for nonlinear processes which have unsymmetrical behaviors around working point. Also a simple yet useful graphical base approach to optimize fuzzy like PID controller is introduced. In order to design the controller a mean value model of a 1.6 turbocharged diesel engine is applied. In this model the effects of injection timing, injected fuel mass, ambient conditions and cycle by cycle torque generation variations are taken into account. The model also predicts the engine behavior in warm-up period. Two main manipulated variables of injection timing and injected fuel mass per cycle are handled to control the engine speed under different sources of engine speed variation such as external loads made by A/C, steering hydraulic pump or alternator and also the internal loads e.g. variable internal friction. The designed controller shows high robustness in response to change in ambient conditions.     

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.     

Correlation analysis of factors influencing the electronic unit pump cycle fuel injection quantity under overall operating conditions for diesel engines

Electronic unit pump (EUP) can satisfy both diesel engine emission legislation and fuel economy by improving injection pressure and numerical control. Fluctuations in cycle fuel injection quantity (CFIQ) of EUP determine the coherence and stability of the EUP fuel injection system. The EUP simulation model is developed in the AMESim environment. The method for the simulation experiment is designed in the MODDE environment using the design of experiments method. The results of the simulation reveal the variation laws of correlation between parameters with interaction or no interaction under overall operating conditions of diesel engines. In addition, the results also show the EUP system is a complex nonlinear system. Under overall operating conditions, all the characteristic parameters, such as fuel supply pressure, cam profile velocity, control valve lift, injector opening pressure, injector needle lift, and injector flow coefficient, have significant correlation with CFIQ. The interacting first-order factors exhibit the most significant correlation with CFIQ. The self-interacting second-order factors have significant secondary correlation with CFIQ.     

热管单管性能测试系统开发

针对现有的热管检测过程中通常采用人工摇动以辨别声音的方式,其存在效率低、准确性差等缺点,研制开发了一套重力热管单管性能测试系统。该系统以高精度环形槽作为热管的加热源,采用非接触式的红外测温技术,以流水作业的方式测量管壁温度,实现了热管传热性能的自动判别。通过阐述热管工作原理,建立了一个测试系统模型;根据整个系统结构设计开发了PLC控制器程序,在.Net开发平台下运用面向对象的设计方法开发了相应的测控软件;在此基础上该系统还引入了抗干扰技术等稳定性设计的方法,以克服外界因素的干扰,保证了整个系统的可靠性;最后,对测试结果进行了分析比较。研究结果表明,该测试系统具有测量效率高、测量数据准确、运行稳定可靠等优点。