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Technical Paper

Analysis of Transient Noise Behavior of a Truck Diesel Engine

2001-04-30
2001-01-1566
Based on NVH tests conducted on a heavy-duty turbocharged DI diesel engine, noise relevant differences between steady-state and transient operating condition were investigated. A vehicle drive-by test simulating the effects of vehicle mass and inertia was performed, followed by transient NVH measurements in a semi-anechoic test cell. Steady-state noise was exceeded by 5 dBA during transient operation due to broadband increase of noise excitation combined with structure resonance amplification. Transient noise results mainly from “harsher” combustion as a consequence of enlarged ignition delay indicated by significant increase in maximum cylinder pressure gradient. Variation of geartrain excitation and combustion excitation revealed that geartrain noise is of minor importance in this context.
Technical Paper

A New TEHD Approach for Sophisticated Simulation of Journal Bearings

2001-10-01
2001-01-3367
The new Thermo-Elasto-Hydro-Dynamic (TEHD) code developed by FEV, is designed to improve the predictability of journal bearing designs and thereby increase the reliability of safety factors in the development of highly loaded internal combustion engines. Advanced analysis tools are evaluated by their performance as well as by their ease of use. High performance means on the one hand: taking into account all the important characteristics, like bearing elasticity or cavitation effects, to mention only some major parameters for modern journal bearing analysis. On the other hand: an economic run-time behavior must be a key feature concerning usability of the TEHD-demands for daily development praxis. Ease of use means also, that the TEHD model can easily be used as a plug-in routine of an already existing software package that is well known to the development departments.
Technical Paper

Modeling of Exhaust Valve Opening in a Camless Engine

2002-03-04
2002-01-0376
Electromechanical valve trains in camless engines enable virtually fully variable valve timing that offers large potential for both part load fuel economy and high low end torque. Based upon the principle of a spring-mass-oscillator, the actuator stores the energy to open and close the valves in springs. However, the motion of the valves and the electromechanical actuation suffers from parasitic losses, such as friction and ohmic resistance. Besides eddy current losses, gas forces obviously play a further important role in the control of exhaust valve opening especially at high engine speeds and loads. Based on engine test bench data, computational simulations (3D CFD, gas exchange process and electromechanical system) are carried out to analyze the effects of exhaust valve gas forces on the dynamic motion of valve and actuator. The modeling approach and results of this investigation are discussed in this paper.
Technical Paper

Applying Representative Interactive Flamelets (RIF) with Special Emphasis on Pollutant Formation to Simulate a DI Diesel Engine with Roof-Shaped Combustion Chamber and Tumble Charge Motion

2007-04-16
2007-01-0167
Combustion and pollutant formation in a new recently introduced Common-Rail DI Diesel engine concept with roof-shaped combustion chamber and tumble charge motion are numerically investigated using the Representative Interactive Flamelet concept (RIF). A reference case with a cup shaped piston bowl for full load operating conditions is considered in detail. In addition to the reference case, three more cases are investigated with a variation of start of injection (SOI). A surrogate fuel consisting of n-decane (70% liquid volume fraction) and α-methylnaphthalene (30% liquid volume fraction) is used in the simulation. The underlying complete reaction mechanism comprises 506 elementary reactions and 118 chemical species. Special emphasis is put on pollutant formation, in particular on the formation of NOx, where a new technique based on a three-dimensional transport equation within the flamelet framework is applied.
Technical Paper

Application of Vehicle Interior Noise Simulation (VINS) for NVH Analysis of a Passenger Car

2005-05-16
2005-01-2514
The overall perception of a vehicle's quality is significantly influenced by its interior noise characteristics. Therefore, it is important to strike a balance between “pleasant” and “dynamic” sound that fits the customer requirements with respect to vehicle brand and class [1]. Typically, a significant share of the interior vehicle noise is transferred through structure-borne paths. Hence, the powertrain mounting system plays an important role in designing the interior noise. This paper describes an application of the method of vehicle interior noise simulation (VINS) to achieve a characteristic interior sound. This approach is based on separate measurements (or calculations) of excitations and transfer functions and subsequent calculation of the interior noise in the time domain.
Technical Paper

A New Transient Elastohydrodynamic (EHD) Bearing Model Linkable to ADAMS®

2001-03-05
2001-01-1075
The new elastohydrodynamic (EHD) code developed by FEV Motorentechnik GmbH, Aachen, is designed to improve the predictability of journal bearing designs and thereby increase the reliability of safety factors in the development of highly loaded internal combustion engines. Using this tool design targets can be achieved with higher confidence levels. The developed code may be linked to commercial multibody system (MBS) codes such as ADAMS® while simultaneously representing the important characteristics occurring in transiently loaded journal bearings including elastic deformation, cavitation, and non-constant speed. Static deviations from ideal journal and bearing shell shapes caused by manufacturing and assembly processes can be considered and are substantially important in the evaluation of journal bearings. Presented is an economic bearing model approach which includes elastic bearing deformations.
Technical Paper

Borderline Design of Crankshafts Based on Hybrid Simulation Technology

2009-06-15
2009-01-1918
This paper introduces different modeling approaches of crankshafts, compares the refinement levels and discusses the difference between the results of the crankshaft durability calculation methodologies. A V6 crankshaft is considered for the comparison of the refinement levels depending on the deviation between the signals such as main bearing forces and deflection angle. Although a good correlation is observed between the results in low speed range, the deviation is evident through the mid to high speed ranges. The deviation amplitude differs depending on the signal being observed and model being used. An inline 4 crankshaft is considered for the comparison of the durability results. The analysis results show that the durability potential is underestimated with a classical crankshaft calculation approach which leads to a limitation of maximum speed of 5500 rpm.
Technical Paper

Prediction of Combustion Delay and -Duration of Homogeneous Charge Gasoline Engines based on In-Cylinder Flow Simulation

2009-06-15
2009-01-1796
In this paper a new approach is presented to evaluate the combustion behaviour of homogeneous gasoline engines by predicting burn delay and -duration in a way which can be obtained under the time constraints of the development process. This is accomplished by means of pure in-cylinder flow simulations without a classical combustion model. The burn delay model is based on the local distribution of the turbulent flow near the spark plug. It features also a methodology to compare different designs regarding combustion stability. The correlation for burn duration uses a turbulent characteristic number that is obtained from the turbulent flow in the combustion chamber together with a model for the turbulent burning velocity. The results show good agreement with the combustion process of the analyzed engines.
Technical Paper

A New CFD Approach for Assessment of Swirl Flow Pattern in HSDI Diesel Engines

2010-09-28
2010-32-0037
The fulfillment of the aggravated demands on future small-size High-Speed Direct Injection (HSDI) Diesel engines requires next to the optimization of the injection system and the combustion chamber also the generation of an optimal in-cylinder swirl charge motion. To evaluate different port concepts for modern HSDI Diesel engines, usually quantities as the in-cylinder swirl ratio and the flow coefficient are determined, which are measured on a steady-state flow test bench. It has been shown that different valve lift strategies nominally lead to similar swirl levels. However, significant differences in combustion behavior and engine-out emissions give rise to the assumption that local differences in the in-cylinder flow structure caused by different valve lift strategies have noticeable impact. In this study an additional criterion, the homogeneity of the swirl flow, is introduced and a new approach for a quantitative assessment of swirl flow pattern is presented.
Technical Paper

Advanced Combustion for Low Emissions and High Efficiency Part 1: Impact of Engine Hardware on HCCI Combustion

2008-10-06
2008-01-2405
Two single-cylinder diesel engines were optimised for advanced combustion performance by means of practical and cumulative hardware enhancements that are likely to be used to meet Euro 5 and 6 emissions limits and beyond. These enhancements included high fuel injection pressures, high EGR levels and charge cooling, increased swirl, and a fixed combustion phasing, providing low engine-out emissions of NOx and PM with engine efficiencies equivalent to today's diesel engines. These combustion conditions approach those of Homogeneous Charge Compression Ignition (HCCI), especially at the lower part-load operating points. Four fuels exhibiting a range of ignition quality, volatility, and aromatics contents were used to evaluate the performance of these hardware enhancements on engine-out emissions, performance, and noise levels.
Technical Paper

Advanced Combustion for Low Emissions and High Efficiency Part 2: Impact of Fuel Properties on HCCI Combustion

2008-10-06
2008-01-2404
A broad range of diesel, kerosene, and gasoline-like fuels has been tested in a single-cylinder diesel engine optimized for advanced combustion performance. These fuels were selected in order to better understand the effects of ignition quality, volatility, and molecular composition on engine-out emissions, performance, and noise levels. Low-level biofuel blends, both biodiesel (FAME) and ethanol, were included in the fuel set in order to test for short-term advantages or disadvantages. The diesel engine optimized in Part 1 of this study included cumulative engine hardware enhancements that are likely to be used to meet Euro 6 emissions limits and beyond, in part by operating under conditions of Homogeneous Charge Compression Ignition (HCCI), at least over some portions of the speed and load map.
Technical Paper

Powertrain-related vehicle sound development

2000-06-12
2000-05-0301
This paper reflects an efficient and comprehensive approach for vehicle sound optimization integrated into the entire development process. It shows the benefits of early consideration of typical vehicle NVH features and of intensive interaction of P/T and vehicle responsibilities. The process presented here considers the typical restriction that acoustically representative prototypes of engines and vehicles are not available simultaneously at the early development phase. For process optimization at this stage, a method for vehicle interior noise estimation is developed, which bases on measurements from the P/T test bench only, while the vehicle transfer behavior for airborne and structure-borne noise is assumed to be similar to a favorable existing vehicle. This method enables to start with the pre- optimization of the pure P/T and its components by focusing on such approaches which are mainly relevant for the vehicle interior noise.
Technical Paper

Plain Bearings in High Performance Engines - Simulation Tools for Advanced Investigations and Layouts

2006-04-03
2006-01-1102
The loads on the plain bearings of modern combustion engines increase continuously. Reasons for this development are increasing engine speeds on gasoline engines, growing cylinder peak pressures at diesel engines and both combined with the steady trend toward light weight concepts. The still significantly increasing power output of modern engines has to be combined with actions reducing the engine friction losses, as for example smaller bearing dimensions or lower engine oil viscosities. At the same time the comfort, lifetime and engine service interval targets are aggravating boundary conditions. This development leads to the point, where former approaches toward plain bearing layout reach their systematic limitations - a first indication are bearing failures, which occur even though all conventional layout criteria's are fulfilled. Further effects need to be considered to simulate the behavior of the plain bearing under the boundary conditions of a fired combustion engine.
Technical Paper

Modern Gear Train Simulation Process for the Virtual Engine and Transmission Development

2006-04-03
2006-01-0585
Current simulation tools for the investigation of the dynamic system response as well as for the component stresses on the basis of multi-body and finite-element techniques are integral part of today's powertrain development efforts. These tools are typical used for the analysis and optimization of shafts, clutches, chain/belt drives, bearings, levers, brackets, housings and many other components. An exception is made by gears which today are still frequently investigated by the help of semi-empirical methods based on DIN, ISO, AGMA and the specific knowledge base of well experienced developers. The main difficulty is that the gears are rolling off via large contact surfaces with complex nonlinear mechanical contact properties. Within the scope of research work FEV developed a new method for the analysis and optimization of gear drives based on comercial multi-body and finite-element software platforms.
Technical Paper

Analytical Investigation of Crankshaft Dynamics as a Virtual Engine Module

1999-05-17
1999-01-1750
A combined finite element method (FEM), multibody system simulation (MSS), and hydrodynamic (HD) bearing simulation technique can be applied to solve for engine crankshaft and cylinder block dynamics. The cylinder block and crankshaft are implemented in the MSS program as flexible FEM structures. The main bearing oil film reaction is described in the MSS program by a pre-calculated reaction force database. The results are displacements and deformations of the crank train parts and the main bearing reaction forces. Verification of the tool was carried out by comparison of main bearing cap accelerations to measured data.
Technical Paper

Downsizing of Diesel Engines: 3-Cylinder / 4-Cylinder

2000-03-06
2000-01-0990
Due to the future application of combustion engines in small and hybrid vehicles, the demand for high efficiency with low mass and compact engine design is of prime importance. The diesel engine, with its outstanding thermal efficiency, is a well suited candidate for such applications. In order to realize these targets, future diesel engines will need to have increasingly higher specific output combined with increased power to weight ratios. This is therefore driving the need for new designs of 3 and/or 4 cylinder, small bore engines of low displacement, sub 1.5l. Recent work on combustion development, has shown that combustion systems, ports, valves and injector sizes are available for bore sizes down to 65 mm.
Journal Article

Influence of the Mixture Formation on the Lubrication Oil Emission of Combustion Engines

2010-04-12
2010-01-1275
Partly competing objectives, as low fuel consumption, low friction, long oil maintenance rate, and at the same time lowest exhaust emissions have to be fulfilled. Diminishing resources, continuously reduced development periods, and shortened product cycles yield detailed knowledge about oil consumption mechanisms in combustion engines to be essential. There are different ways for the lubricating oil to enter the combustion chamber: for example as blow-by gas, leakage past valve stem seals, piston rings (reverse blow-by) and evaporation from the cylinder liner wall and the combustion chamber. For a further reduction of oil consumption the investigation of these mechanisms has become more and more important. In this paper the influence of the mixture formation and the resulting fuel content in the cylinder liner wall film on the lubricant oil emission was examined.
Technical Paper

Prediction of Hydrodynamic Bearing Behaviour for Pre-layout of Cranktrain Dimensions

2010-10-25
2010-01-2186
Calculating the bearing reliability and behavior is one of the primary tasks which have to be performed to define the main dimensions of the cranktrain of an internal combustion engine. Since the bearing results are essential for the pre-layout of the cranktrain, the conclusion on the bearing safety should be met as early as possible. Therefore detailed simulations like T-EHD or EHD analysis may not be applied to define the dimensions in such an early development phase. In the frame of this study a prediction methodology, based on a HD bearing approach, for bearing reliability of inline-4 crankshafts of passenger cars is proposed. In this way not only the design phase is shortened but also achieving the optimal solution is simplified. Moreover the requirement of a CAD model is eliminated for the preliminary design phase. The influencing parameters on the bearing behavior are first selected and divided into two groups: geometry and loading.
Technical Paper

Turbocharging of Downsized Gasoline DI Engines with 2 and 3 Cylinders

2011-09-11
2011-24-0138
Turbocharged DISI engines with four cylinders have established in the market and provide a performance comparable to larger six-cylinder engines in the smaller compartment of a four-cylinder engine. In the Japanese market, also turbo gasoline engines with 500 - 660 cm₃ displacement have a long tradition in Kei-Cars. However, those engines show a lower specific performance as would be required for propelling typical small or compact vehicles in Europe. Recently, two-cylinder turbo engines have come to market, which are found attractive with respect to sound, package, and also enable low vehicle fuel consumption in NEDC test. The paper presents a turbocharger layout study on 2- and 3-cylinder engines. It discusses the influence of cylinder displacement volume on the sizing of turbines and compressors, and how specific flow phenomena in the turbine can be captured in the simulation model.
Technical Paper

Sound Design Under the Aspects of Musical Harmonic Theory

2003-05-05
2003-01-1508
Sound design of vehicle interior and exterior noise is becoming more and more important for the customer's impression of product quality. To accommodate for this, FEV has developed a sound design method that utilizes FEV VINS (Vehicle Interior Noise Simulation) to design series production relevant hardware modifications. Within a new internal research program, FEV's NVH specialists investigated the theory of musical harmonics and compared the results with engine acoustics in an effort to establish if and what mechanical acoustics can learn from musical harmonics. Looking at engine acoustics from the point of view of musical harmonic theory, the specific combination of half and integer engine orders in particular offers the possibility of creating harmonious noise content. Furthermore, we can estimate how the typical subjective evaluations derive from the integer and half engine orders that occur depending on the engine concept.
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