ENGINE BOTTOM END DESIGN: A CASE STUDY

Engine noise and vibration are the major contributors to vehicle interior and exterior noise. Among the engine components, the cylinder block is one of the major noise emitting parts as well as a vibration transmitting passage to the periphery components. Therefore, increasing block stiffness has been the major concern in designing an engine for good NVH. Studies have shown that 70-80% of vibration energy is transmitted through the cranktrain system. Hence, not only the overall stiffness of the cylinder block is a concern of design, but the block bottom end design is critical to the structure-borne and air-borne noise characteristics. Many papers have been presented to discuss different designs of the bottom end and their effect on vibration and noise radiation. The design decision is often based more on the design features than the engineering functions. Although stiffness is often defined as a criterion for design targets, there is no clear definition of what metrics and targets should be used in the design process. This study presents a comparison of the structural deformation and surface vibration of two engines with similar fundamental designs but significant differences in the block bottom end design. One engine is quieter than the other. This study begins with static stiffness and experimental modal analysis and extends to include laser holography and surface velocily measurements. This information provides more insights about structural rigidity, noise radiation and component joint effects than simple overall stiffness. Based on the results, design changes are identified and the results of prototype testing are presented to demonstrate the improvements. For the covering abstract see IRRD E104312.

Language

  • English

Media Info

  • Features: References;
  • Pagination: p. 101-6

Subject/Index Terms

Filing Info

  • Accession Number: 00790175
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • ISBN: 0-9622072-3-3
  • Files: ITRD
  • Created Date: Apr 11 2000 12:00AM