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%.     

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.

     

分析内燃机的磨损磨粒-利用铁谱加热法

阐述了内燃机摩擦磨损机理和铁谱技术。通过利用铁谱加热分析法对内燃机的摩擦磨损进行分析与研究。这一分析方法对于分析和鉴别多摩擦副工况下的油液中各类磨粒的材质成分是一种极为有效方法,并且为内燃机摩擦磨损的故障诊断提供了有利的科学依据。     

国内外内燃机冷却水添加剂标准之比较

冷却水添加剂已广泛应用于内燃机，有关冷却水添加剂有许多国家和行业标准，本在综述国内外标准基础上，着重比较了中国和美国的有关标准。对有关冷却水添加剂标准下一步的制订提出了作的观点。     

Influence of temperature on cam-tappet lubrication in an internal combustion engine

The transient thermo-elastohydrodynamic (TEHL) lubrication simulation and isothermal elastohydrodynamic (EHL) simulation were performed on the exhausting camtappet friction pair of an internal combustion engine. Although by employing the two models the center pressure, the thickness of the lubricant film and friction coefficient obtained were similar in the changing trend during a rotating cycle, the parameters make a great difference, especially for the thickness of the lubricant film; the TEHL was four times thicker than the EHL. These results show that the temperature should not be neglected in the study of the lubrication of cam-tappet pairs. __________ Translated from Tribology, 2006, 26(4): 362–366 [译自: 摩擦学学报]     

基于多压力变温实验的缸套-活塞环摩擦因数预测研究

为探究内燃机中缸套-活塞环摩擦副在复杂工况下的摩擦因数变化规律,根据实际工况下的温度和压力,使用SRV高温摩擦试验机模拟内燃机系统缸套-活塞环之间的往复式摩擦运动,获得不同温度和压力下的摩擦因数,并测试不同温度下润滑油的黏度。以摩擦接触面温度、载荷和润滑油黏度为输入,摩擦因数为输出,构建BP神经网络预测模型。结果表明,BP神经网络具有较高的预测精度,测试集误差值稳定在1%以内,满足工程精度要求。     

Investigation of emission characteristics affected by new cooling system in a diesel engine

In a typical cooling system of automotive engine, a mechanical water pump is used to control the flow rate of coolant. However, this traditional cooling system is not suitable for a high efficiency performance in terms of fuel economy and exhaust emission. Therefore, it is necessary to develop a new technology for engine cooling systems. These days, the electronic water pump is spotlighted as the new cooling system of an engine. The new cooling system can provide more flexible control of the coolant flow rate and the engine temperature, which used to be strongly relied on the engine driving conditions such as load and speed. In this study, an engine experiment was carried out on a New European Drive Cycle (NEDC) with a 2.7L diesel engine. The electric water pump operated by BLDC motor and the electronic valve were installed in the cooling system to control the coolant flow rate and temperature. This paper explains that the exhaust emissions were reduced with an increase in the engine temperature and a decrease in the coolant flow. From this experiment, we found that increasing coolant temperature had a significant effect on reducing the emissions (e.g. THC and CO). Decreasing coolant flow also affected the reduction of emissions. In contrast, NOx emission was observed to increase in these conditions. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Kyung-Wook Choi received his B.S. degree in Mechanical Engineering from Hanyang University, Korea, in 2006. He is now working on a doctoral degree in Hanyang University. Kyung-Wook’s research interests include Hybrid Electric Vehicle, Internal Engine Combustion, and Engine Cooling System. Ki-bum Kim was awarded a bachelor’s degree in naval architecture and ocean engineering from Chung-Nam National University in the Republic of Korea. In August 2001, he began graduate study at the University of Florida. Kibum graduated with a Master of Science degree in mechanical engineering from the University of Florida in August 2003. He went on to earn his Ph.D. in mechanical engineering, also at the University of Florida, in August 2006. He is working as a research professor at Hanyang University. Ki-Hyung Lee is a Professor at the department of mechanical engineering in Hanyang University. He received his B.S and M.S degree in Hanyang University in 1983 and 1986. Then he graduated with a Ph.D. degree in mechanical Engineering at Kobe University, Japan in 1989. He worked as a research engineer at Nissan motor’s central technical center for 4 years.     

内燃机主轴承摩擦功率损失的影响因素

研究了影响主轴承摩擦功率损失的影响因素,包括轴承表面粗糙度、润滑油温度、曲轴转速、轴颈间隙和供油提前角,同时分析各影响因素对内燃机主轴承的影响。分析所用物理模型为直列六缸内燃机,其数学模型主要依据有限差分法与欧拉法求解雷诺方程,润滑油膜接触通过在时域内压力平衡迭代计算。对内燃机曲轴主轴承摩擦功率损失影响因素进行了探讨,计算结果表明,在内燃机零部件设计阶段应充分考虑轴承间隙以及表面粗糙度对摩擦功率损失的影响。     

Piston ring friction loss behaviour for motored and fired reciprocating engines

A previously developed piston ring lubrication model has been further extended so that the piston ring frictional losses can be predicted in both hydrodynamic lubrication and metal-to-metal contact regions for various engine operating conditions. Ring friction results for two engine types are presented for both hot motoring and engine firing conditions. The hot motoring predictions were found to be in good agreement with tests. Results show that when the engine is motored, piston ring friction losses in the hydrodynamic lubrication region predominate. If the engine is fired, the losses in the metal-to-metal contact region become dominant due to high gas pressure and temperature effects. Ring friction loss can be significantly reduced by using low tension rings with a correct ring sliding face profile.     

Demonstrating Improved Fuel Economy Using Subsystem Specific Lubricants on a Modified Diesel Engine

Fuel economy performance in modern internal combustion engines is of increasing importance to lubricant formulators due to regulations targeting global greenhouse gas emissions. Engines typically employ a single lubricant, with a common sump, to service all components. As a result, base oil and additive selection for fuel economy performance is a compromise among competing demands for different engine subsystems. Opportunities for significant fuel economy improvement through targeted formulation of lubricants for specific engine subsystems are presented, with specific emphasis on segregating the lubricant supplies for the valve train and the power cylinder subsystems. A working prototype was developed in a lab environment by modifying a commercially available twin-cylinder diesel engine. Motored valve train and whole-engine fired test results were obtained and compared to model data. Fuel economy benefits were demonstrated using market representative heavy-duty diesel lubricants, including mineral oil and polyalphaolefin (PAO) blends. The fuel economy benefits of a dual-loop lubricant system are demonstrated through significant viscosity reduction in the power cylinder subsystem, achieving overall engine friction reductions of up to 8% for the investigated operating condition. Results suggest that additional gains may be realized through targeted base oil and additive formulation. Implications for incorporation in larger diesel engines are also considered.     

Friction Power Loss Simulation of Internal Combustion Engines Considering Mixed Lubricated Radial Slider,Axial Slider and Piston to Liner Contacts

Different types of mixed lubricated contacts are present in internal combustion engines. These are several radial slider bearings; for instance, in main bearings; big end, small end, and piston pin bearings; as well as axial slider bearings and piston–liner contacts. Phenomena such as friction power loss and wear as well as acoustic excitation and oil consumption of the overall lubrication system are mainly affected by these contacts. Therefore, the simulation-based investigation of oil film–lubricated contacts is important during the development process of internal combustion engines. Due to the highly nonlinear interactions, the applied mathematical models have to consider the dynamics of the overall flexible body system in addition to the detailed properties of the contacts and the lubricant itself.

This work outlines both the theory of the separated mathematical models and their coupling. The large number of nonlinear contacts, which is possible to consider when applying the presented coupling approach, is emphasized. Furthermore, application of a friction power loss analysis for an in-line four-cylinder internal combustion engine is described.     

Novel method of measuring tappet rotation and the effect of lubricant rheology

One of the main drivers for developing lubricant technology is engine durability. Researchers and scientists are using new technologies, materials and advanced lubricant formulations to reduce overall engine friction and wear. One of the main engine tribological components is the valve train. This is one of the most challenging components to lubricate effectively because of the higher contact loadings and accounts for 10–20% of the total engine friction loss. The two main factors affecting the performance of engine valve trains are wear and friction, and a wide range of mechanical configurations are used to improve these. For example, direct-acting overhead camshaft valve train configurations use a rotating tappet design. Normally, the tappet is slightly offset from the cams and the cam is slightly conical to match the domed tappet to facilitate tappet rotation for even wear and to reduce slippage. In this paper, a novel innovative technique has been described to monitor tappet rotation in a real production engine having a direct overhead cam–tappet arrangement. The monitoring technique was applied to a VW Tdi engine head, and tests were carried out under different operating conditions. Lubricant compositions, oil temperature, pressure and camshaft speeds on tappet rotation were measured and all are shown to have an effect. The balance of forces between the cam–tappet and tappet-bore was found to be interlinked and the design of the hydraulic lash adjuster had a significant effect.This unique tappet rotation monitoring system can be used on most of the direct overhead camshaft engines, with minor engine modifications, to measure lubricant and hardware effects under both motored and fired conditions.     

Modeling and fuzzy control of the engine coolant conditioning system in an IC engine test bed

Mechanical and thermodynamical performance of internal combustion engines is significantly affected by the engine working temperature. In an engine test bed, the internal combustion engines are tested in different operating conditions using a dynamometer. It is required that the engine temperature be controlled precisely, particularly in transient states. This precise control can be achieved by an engine coolant conditioning system mainly consisting of a heat exchanger, a control valve, and a controller. In this study, constitutive equations of the system are derived first. These differential equations show the second-order nonlinear time-varying dynamics of the system. The model is validated with the experimental data providing satisfactory results. After presenting the dynamic equations of the system, a fuzzy controller is designed based on our prior knowledge of the system. The fuzzy rules and the membership functions are derived by a trial and error and heuristic method. Because of the nonlinear nature of the system the fuzzy rules are set to satisfy the requirements of the temperature control for different operating conditions of the engine. The performance of the fuzzy controller is compared with a PI one for different transient conditions. The results of the simulation show the better performance of the fuzzy controller. The main advantages of the fuzzy controller are the shorter settling time, smaller overshoot, and improved performance especially in the transient states of the system.     

Precise instrumentation of a diesel single-cylinder research engine

The accuracy of any empirical result is a direct consequence of the quality of experimental setup and the strict control over testing conditions. For internal combustion engines, a large number of parameters that also exhibit complex interdependence may significantly affect the engine performance. Therefore, this work describes the essentials required to establish a high-quality diesel engine research laboratory. A single-cylinder diesel engine is taken as the fundamental building block and the requirements for all essential sub-systems including fuel, intake, exhaust, coolant and exhaust gas recirculation (EGR) are laid out. The measurement and analysis of cylinder pressure, and exhaust gas sampling/conditioning requirements for emission measurement are discussed in detail. The independent control of EGR and intake boost is also highlighted. The measurement and analysis techniques are supported with empirical data from a single-cylinder diesel engine setup. The emphasis is on providing the necessary guidelines for setting up a fully-instrumented diesel engine test laboratory.     

Optimizing parameters of complexly loaded friction bearings

Crankshaft rod bearings of a combustion engine are used as an example to show the technique and results of optimization of the design parameters of friction bearing under a complex load. The field of hydrodynamic pressures in a lubricating layer, which separates the crank pin and the bearing lining, is determined by integrating the equation for filling of the gap. This approach ensures observance of the condition of lubricant continuity at the boundaries of discontinuity and restoration of the lubricating layer. The lubricant viscosity, which is assumed to be an effective function of the temperature of the lubricating layer, is adjusted at each step of the calculation of the crank pin’s motion trajectory.     

内燃机润滑油添加剂抗磨损能力及其对发动机性能影响的试验研究

本文通过对几种选型的发动机润滑油添加剂的专用摩擦磨损试验机试验和发动机呆性能对比试验,证实了此类机油添加剂的减磨作用效果。分析了两种志用摩擦磨损试验机的试验结果与发动机性能试验结果的对应关系,从而提出了进一步试验研究的方向。     

DYNAMIC DESIGN OF INTERNAL COMBUSTION ENGINE BLOCK STRUCTURE

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Investigations on the effect of measurement errors on estimated combustion and performance parameters in HCCI combustion engine

Several parameters derived from heat release analysis are used for combustion diagnostics and control in internal combustion engines. It is important to tune the input parameters used in heat release calculations, in order to get correct estimation of heat release rate. In this study, tuning of input parameters is carried out by using cumulative heat release calculations of cylinder pressure during motoring. This tuning procedure uses offline iterative processing of motoring in-cylinder pressure data. The tuned parameters obtained from this method can also be utilized for online analysis of combustion parameters. Input parameters used in these investigations are intake air temperature, intake air pressure, phasing between the acquired pressure and crank angle position, compression ratio and scaling factor of heat transfer coefficient. Effect of error in these input parameters on estimated combustion and performance parameters like IMEP, combustion phasing, combustion duration, heat release rate, and maximum mean gas temperature are evaluated. The relative importance of measurement error in input parameters and its maximum expected error in the final results is analyzed in a HCCI combustion engine. Results shows that measurement errors in phasing between pressure and crank angle position, compression ratio and inlet air pressure affect estimated combustion and performance parameters significantly.     

The effect of a friction modifier on piston ring and cylinder bore friction and wear

The addition of friction modifiers to crankcase lubricants has been shown to significantly reduce the mechanical losses of critical components in internal combustion (ic) engine; thereby improving fuel economy.In this study the friction and wear of a piston ring/cylinder bore material combination was studied using a pin-on-plate laboratory tribo-test machine developed to reproduce the wear mechanisms encountered in an ic engine. Two lubricants were evaluated: (i) a standard SAE 30 grade diesel formulation, and (ii) the same formulation with the addition of a 5% soluble MoS₂ friction modifier.Analysis of the wear results identified three periods of wear: (1) running-in, (2) transient wear and (3) terminal wear. Throughout this study particular emphasis has been placed on the simulation of the wear mechanisms occurring within engines. Surface analysis confirmed that both abrasive wear and delamination wear was produced.Friction benefits attributable to the addition of MoS₂ friction modifier were obtained. However, under specific conditions the wear rate increased due to increased abrasion of the plate.     

Friction model of a marine diesel engine piston assembly

In modern marine diesel engines, power output and in-cylinder firing pressures are constantly increasing, leading to higher friction in engine components and especially in the piston assembly. A good understanding of the friction contributions of the various engine components is needed, if mechanical efficiency is to be improved. A friction model for the engine piston assembly has been developed and is presented in this paper. The model, based on lubrication theory, considers the detailed engine geometry and the complete lubricant action, and thus can be applied to a wide range of engines. In detail, the analysis takes into account the friction components of compression rings, oil control rings, piston skirt and gudgeon pin of the engine piston assembly. The model was applied to a four-stroke (medium speed) marine diesel engine and the effect of engine speed and load on friction was examined and compared with results from other semi-empirical models. The engine friction was predicted at constant rotational speed (generator operation) and variable rotational speed (propulsion operation).