FEV Motorentechnik GmbH : Powertrain Dynamics Applications using " ADAMS / Engine powered by FEV " Part II : Cranktrain Dynamics

In development processes of modern powertrains virtual prototyping methods become more and more important. On one hand numerical simulations save development time and expenses replacing expensive test rig investigations and on the other hand they help the development engineers understanding the dynamics of the subsystems in detail. In general it can be distinguished between special software and multi purpose simulation software. Previous engine development processes have shown that neither the specialized engine programs nor the multi purpose software are able to match all requirements of modern development processes alone. Only a combination of both can deliver the specific acknowledgment on one hand and the flexibility in usage on the other hand. Therefore it has been decided at FEV Motorentechnik to set up specific software which bases on the standard components (e.g. Solver) of multi purpose software. Since it is possible to include flexible structures from Finite Element Analysis (FEA) into Multibody System Simulation (MSS), ADAMS appears to be the perfect base for engine specific add ons. The Dynamics of subsystems can be simulated as well as the structural dynamics of single components. With ADAMS/ENGINE the product line already delivers a good architecture for simulation activities embedded into powertrain development processes. A strategic partnership was formed between MDI and FEV to combine the strength of both companies. Beneath enhancements of existing modules the development of the new cranktrain module is the first common project. For this FEV delivers years of experience in cranktrain simulation while MDI puts the ADAMS/Engine architecture and know how in software engineering at disposal. The development of the cranktrain module is split up into two parts: The first part is based on rigid bodies and simplified flexibility approaches. Three levels of refinement will be available for the description of the crankshaft: -rigid crankshaft -torsional flexible crankshaft -torsional and bending flexible crankshaft using a beam approach The user can easily switch between these approaches depending on the results that are expected. For an evaluation of the free forces for example the rigid approach is sufficient. Additional Features that will be included in the cranktrain module are: -Engine Mounts (rubberand hydro-), -Flywheel (single and dual mass), -Torsional vibration damper (rubber and viscous), -Hydrodynamic plain bearings, -Balancing shafts. The second part of the cranktrain module development part contains flexible body approaches for crankshaft and engine block. It is perfect to deliver highly accurate boundary conditions for stress analysis and NVH investigations. Most of the methodology to be implemented has been used and verified successfully in engineering projects before. This paper describes some of these features and shows examples of elements currently being developed. CAE IN THE MODERN POWERTRAIN DEVELOPMENT PROCESS There are many areas of CAE applications on combustion engines. Beneath the thermodynamics of the combustion and fluid dynamics of the intake and exhaust systems mechanical simulations are a basic part of the engine development process. Fig. 1 shows the typical subsystems of the engine, that are designed with simulation support. In the case of the mechanical subsystems, shown on the left hand side, design improvements are expected from simulation work, mainly focusing on: Component stresses and durability, Lubrication, friction and wear out, Noise and vibrations. Intake Gas Dynamics Intake Gas yna ics Exhaust Gas Dynamics Exhaust as Dynamics Combustion o bustion Cranktrain Cranktrain Valve Train Valve Train Timing Drive Timing Drive Accessories Accessories Accessory Drive Accessory Drive Piston / Piston Ring Piston / Piston Ring Fig. 1: Engine CAE Areas To ensure efficiency when including CAE into development processes, it is important, that the targets of simultaneous engineering techniques are fulfilled. This means, that valuable results must be available after time periods that are reasonable concerning the current project phase, because in the tight frame of modern development processes it is not possible to wait for simulation results. On the other hand the quality of the results has to be sufficient to make unique design decisions. Especially in the first development phases, when no prototype is available, the simulation results are often the only decision base and must be reliable. A mayor design change after the first prototype produces a large amount of additional costs and often leads to project delay. An additional problem for the CAE engineers is the fact, that the expectations on response time and results quality are continuously changing during the development. In the very early concept phase evaluations of rough tendencies may be sufficient but have to be delivered quickly. In a detailed design phase more time may be available, but the results have to be more accurate. Fig. 2 shows the CAE support in the pre-prototype phases of an engine development project. To support all three phases, concept, layout and detailed design, the used CAE software must have different “Refinement Levels” to achieve a first prototype that is on a high technical development level. State of the art is using different software in different phases. Most times these software packages are based on different data structures, so transferring the data from one simulation tool to the other means additional manual work and of course a quality risk too. So one of the main demands on engine simulation software to be used in the development is flexibility concerning refinement levels. Engineering Judgment Tools 3D CAE Engine Development CAE Support Prototyping Detail Design Layout Concept