Key Steps and Methods in the Design and Development of Low Noise Engines 1999-01-1745
The next generation of automotive engines has to meet 2004 emission limits, ideally with improved fuel economy and with noise emission which is at least 3 dBA below the current status. Using both simulation and experimental analysis these challenging requirements can only be fulfilled by clearly defining all key steps in NVH development and by applying suitable technological methods.
The development procedure discussed in this paper is characterised by several aspects: two stage prediction procedure fully integrated in the design process, combustion development with a definite focus on noise, a closed loop between simulation and test bed development and consideration of noise in the calibration of engine and drivetrain management systems. Apart from meeting target noise levels, noise quality is the reference parameter which is continuously evaluated by means of the AVL Annoyance Index.
The first stage of the noise prediction procedure is made to quantify noise levels for different design concepts and has to be available in time for the concept design decision. Usually the time available does not allow extensive simulation of variants and requires a clever combination of simulation analysis and know-how drawn from experience with a variety of different engine designs. Compared to just a few years ago, higher quality simulation models - e.g. non-linear FE-analysis and dynamic valve train, gear train and cranktrain models - can now be created in a shorter time.
In the second stage of NVH optimisation work, the focus is shifted to the deeper understanding and more accurate description of boundary conditions and excitation mechanisms. This results in thorough interfacing of test results with the simulation procedure and is discussed in this paper for combustion noise, gear train, and other mechanical noise sources and radiators. Case evaluation procedures and overall development results are also presented.