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Technical Paper

Lubrication and Ventilation System of Modern Engines - Measurements, Calculations and Analysis

The main function of an engine's lubrication system is to supply the different engine components with sufficient oil under all operating conditions. The demand of modern engines regarding the necessary oil pressure and flow of the individual components is influenced by the engine speeds and the accelerations due to the vehicle driving conditions. In addition to that, the lubrication system effects the following topics: The drive power of the oil pump which is influenced by the oil pump capacity, the oil pressure and mechanical losses of the oil pump. The oil mass which is supplied to the engine oil consumers and flows back via the oil return system to the crankcase and the oil pan. In the crankcase ventilation system, oil and gas have to be separated. The oil aeration due to the oil mass in the crankcase and the moving parts. The ventilation losses in the crankcase which are influenced by the axial ventilation areas and the moved oil mass.
Technical Paper

Exhaust Heat Recovery System for Modern Cars

The fuel consumption and the emissions of modern passenger cars are highly affected by the fluid and material temperatures of the engine. Unfortunately, the high thermal efficiencies of Direct Injection (DI) Diesel and Spark Ignition (SI) engines cause in many driving situations low heat transfer to the engine components and especially to the oil and the coolant. In these conditions the normal operating temperatures are not achieved. Especially at low ambient temperatures and low engine loads the requirement of a comfortable cabin heating and a fast warm-up of engine oil and coolant cannot be satisfied simultaneously. To reach the required warm-up performance, an Exhaust Heat Recovery System (EHRS) will be demonstrated. Further design and optimization processes for modern cooling systems in fuel-efficient engines require numerical and experimental investigations of supplemental heater systems to meet all requirements under all circumstances.
Technical Paper

Analytical and Empirical Methods for Optimization of Cylinder Liner Bore Distortion

Beside the traditional prediction of stresses and verification by mechanical testing the optimization of cylinder liner bore distortion is one of today's most important topics in crankcase structure development. Low bore distortion opens up potentials for optimizing the piston group. As the piston rings achieve better sealing characteristics in a low deformation cylinder liner, oil consumption and blow-by are reduced. For unchanged oil consumption and blow-by demands, engine friction and subsequently, fuel consumption could be reduced by decreasing the pre-tension of the piston rings. From the acoustical point of view an optimization of piston-slap noise is often based on an optimized bore distortion behavior. Apart from basics to the behavior of liner bore distortion the paper presents advanced analytical and empirical methods for detailed prediction, verification and optimization of bore distortion taking into account the effective engine operation conditions.
Technical Paper

Low Cycle Fatigue of Aluminum Cylinder Heads - Calculation and Measurement of Strain under Fired Operation

The problem of cracks in cylinder heads due to low cycle fatigue (thermal fatigue) is well known for engines with high specific power output. However it is still difficult to predict the lifetime of a new cylinder head due to the number of influencing parameters and the complexity of material behavior. Better understanding of cylinder head fatigue can improve the development process of a new engine concerning CAE as well as mechanical testing efficiency. Therefore a CAE tool which can calculate strains and stresses as a function of time for a defined operating cycle of the engine was developed. In parallel a measuring technique was developed which allows to measure strains on the surface of the combustion chamber side of the cylinder head during fired engine operation. For different Aluminum-Silicon casting alloys the material behavior was described in the Finite Element Program ABAQUS by a nonlinear kinematic / isotropic hardening model.
Technical Paper

PIFFO - Piston Friction Force Measurements During Engine Operation

Fuel consumption of a modern combustion engine is significantly influenced by the mechanical friction losses. Particularly in typical city driving, the reduction of the engine friction losses offers a remarkable potential in emission and fuel consumption reduction. The analysis of the engine friction distribution of modern engines shows that the piston group has a high share at total engine friction. This offers a high potential to optimize piston group friction. The paper presents results of recent research and development work in the field of the tribological system piston/piston ring/cylinder bore.
Technical Paper

Connecting Rod Bearing Operation with Aerated Lube Oil

The connecting rod big-end bearing is one of the most heavily loaded components of the lubrication system of high speed combustion engines. The bearing's oil supply has to be designed consciantious in order to ensure an immaculate reliability in operation. The supply oil flow has to pass the main bearing and the rotating crankshaft before entering the connecting rod bearing. It is common knowledge that the centrifugal forces due to the crankshaft rotation influence the oil flow through the also rotating supply bore. The centrifugal forces effect a parabolic pressure profile along the supply bore. The oil pump has to ensure a certain pressure level in the main oil gallery (depending on the engine speed and the spherical positioning of the rotating bore) to overcome these centrifugal forces. If the oil pressure is lower than this certain level the bearing's oil supply will be interrupted - bearing damage is the consequence.
Technical Paper

Cylinder Liner Deformation Analysis - Measurements and Calculations

Modern passenger car engines are designed to operate at increasingly higher rated engine speeds with higher thermal loads. To reduce engine weight and length, the engines are usually siamesed without a cooling path between the cylinder liners. This leads to high temperatures in the siamesed area and to an increase in liner deformation. The distortion of the cylinder liners of internal combustion engines has a significant affect on engine operation. It can affect the oil consumption, the blow-by, the wear behavior and, due to friction, the fuel consumption. In order to achieve future requirements regarding exhaust emissions and fuel consumption, the development of low distortion engine blocks will play a significant role.
Technical Paper

Cooling System Development and Optimization with the Computer Code COOL

Because of increasing stresses in combustion engines and critical comfort requirements of engine warm-up behavior, FEV has placed a special emphasis on solving cooling system problems. In addition to 3D-CFD calculations and special FEV measurement techniques - such as fiber optical cavitation detection, instationary heat balance measurements during warm-up, etc. - FEV has developed a 1D computer code, known as ‘COOL’, to optimize cooling systems already during the engine design phase or to analyse and eliminate weaknesses in the coolant circuit of existing engines. Beside the algorithm and structure of COOL the paper mainly presents the analysis capabilities of the code. In this connection the emphasis is placed on examples to the current OEMs problem: transient warm-up of DI-diesel engines. The COOL-code is so far a unique CAE tool which exclusively has been applied to projects conducted by FEV. Because of the increasing demand it is planned to commercialize the code in 1998.