Research On Light-weight And Low-noise Design For Single Cylinder Diesel Engine With Virtual Design Technology

Single cylinder diesel engine is the primary power mechanism in Chinese agriculture. Presently the development of single cylinder diesel engine industry confronts multiple difficulties and challenges, such as the rise of material price, fierce market competition, increasingly stringent legislations. Therefore it is proposed to develop new generation single cylinder engine with lower noise, lighter weight, cleaner emission and lower fuel consumption. The dissertation applies advanced digital design and virtual simulation technologies to low-noise and lightweight design of single cylinder engine, and mainly studies up on the engine dynamics response, noise and vibration characteristics, componets strenghth and thermal stress, cylinder block structure optimization, which also involves great theoretical significance and engineering application values.Starting from engine thermal dynamics and multi-body dynamics, derive the inner and outer loads history during working cycle utilizing virtual simulation technology, supplying exact boundary conditions and loads for subsequently structural finite element analysis. Different from traditional empirical design, the dissertation introduces a new approach based on simulation technology to analyze the varying regulations of connect rod's equivalent reciprocating mass and equivalent rotating mass. According to the analytical results, new mechanisms are developed to completely balance centrifugal force and 1st reciprocating force of cranktrain.In the respect of low-noise design, main research contents include identification of noise sources and analysis of noise characteristics,prediction of block radiated noise and low-noise design, balance mechanism design. Systematically identifying engine noise sources is performed, utilizing several experiment methods, to serve the noise reduction task. Aiming at the problem of predicting structure radiated noise, an integrated numerical simulation method is proposed, combining multibody simulation (MBS), finite element method (FEM) and boundary element method (BEM), furthermore the specific operating process is presented to perform low noise engine development. In the respect of lightweight design, the structural nonlinear analysis and lightweight design based on structure optimization technology are presented. For a start set up exact nonlinear finite element model and analyze the block's stress distribution, preparing for next optimization work. Comparing of different loadcases, influences on stress level, cylinder head bolt's tension and gasket pressure are discussed due to mechanical load and thermal load. Secondly topology optimization and shape optimization are applied to block lightweight design, detailedly specifying the definition of optimization parameters and design process. The dissertation explores a path for the application of structure optimization technology to the engine complicated components'design.The research in the dissertation is the first national case to entirely reduce the noise of single cylinder diesel engine, moreover lightweight design is studied, avoiding the contradiction between lightweight design and low-noise design. Finally the first single cylinder engine with lightweight and low-noise is designed and produced successfully. According to the experimental validation, block weight is reduced by 5kg, and the engine noise is reduced from 114.21dBA to 110.8dBA, nearly 3.4dBA apparently, coinciding with national noise legislation.