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Technical Paper

An Analytical Methodology for Engine Gear Rattle and Whine Assessment and Noise Simulation

In this paper, a CAE methodology based on a multiphysics approach for engine gear noise evaluation is reviewed. The method comprises the results and outputs from several different analytical domains to perform the noise risk assessment. The assessment includes the source-path analysis of the gear-induced rattling and whining noise. The vibration data from the exterior surface of the engine is extended through acoustic analysis to perform the engine noise simulation and to identify acoustic hot spots contributing to the noise. The study includes simulations under different engine loading conditions with results presented in both time and frequency domains. Various sensitivity analyses involving different gear geometries and micro-geometries are investigated as well. Finally, the simulation results from three different engines are compared vis-a-vis.
Technical Paper

Predicting Variation in the NVH Characteristics of an Automatic Transmission using a Detailed Parametric Modelling Approach

Generally within engineering design, the current emphasis is on biasing the development process towards increased virtual prototyping and reduced “real” prototyping. Therefore there is a requirement for more CAE based automated optimisation, Design of Experiments and Design for Six Sigma. The main requirements for these processes are that the model being analysed is parametric and that the solution time is short. Prediction of gear whine behaviour in automatic transmissions is a particularly complex problem where the conventional FEA approach precludes the rapid assessment of “what if?” scenarios due to the slow model building and solution times. This paper will present an alternative approach, which is a fully parametric functionality-based model, including the effects of and interactions between all components in the transmission. In particular the time-varying load sharing and misalignment in the planetary gears will be analysed in detail.
Technical Paper

Engine Cylinder Blocks and Heads NVH Improvements: Bolt Accelerations Computation Methodology

The need for engine system CAE radiated noise analysis to confirm results obtained from “component - only” analysis are expensive and time consuming. This is because engine system analysis requires finite element modeling of most engine components (large modeling time) and extensive CPU time and cost to run the full FE system model. The objective of this paper is to introduce a new CAE methodology that makes use of “component - only” analysis to predict the NVH systems effect of the engine block and head, without the need of analyzing the full engine system model. This new CAE methodology evaluates the bolted joint accelerations at the engine block and head flange connections to the: front cover; cam covers; oil pan; intake; exhausts; and transmission. This new method is called BAC (Bolt Accelerations Computation). BAC, in conjunction with SVL (Surface Velocity Level) acoustic response, has been used to optimize the Ford 5.4L cylinder block and cylinder heads for NVH.
Technical Paper

Numerical Modeling of Engine Noise Radiation through the use of Acoustic Transfer Vectors - A Case Study

This paper presents the numerical modeling of noise radiated by an engine, using the so-called Acoustic Transfer Vectors and Modal Acoustic Transfer Vectors concept. Acoustic Transfer Vectors are input-output relations between the normal structural velocity of the radiating surface and the sound pressure level at a specific field point and can thus be interpreted as an ensemble of Acoustic Transfer Functions from the surface nodes to a single field point or microphone position. The modal counter part establishes the same acoustic transfer expressed in modal coordinates of the radiating structure. The method is used to evaluate the noise radiated during an engine run-up in the frequency domain. The dynamics of the engine is described using a finite element model loaded with a rpm-dependent excitation. The effectiveness of the method in terms of calculation speed, compared with classical boundary element methods, is illustrated.