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Modeling and NVH Analysis of a Four-Cylinder Gasoline Engine and Providing a way to Reduce it

Khorshidi, Mohammad | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50621 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Saadat Foumani, Mahmoud
  7. Abstract:
  8. Millions of people are exposed to noise every day in their work and life, and their physical and mental health is at risk due to this issue. Hence, the issue of noise and vibration has become an important factor in car quality. One of the sources of noise and vibration in the vehicle is the engine. The engine is the heart of the car and its most important part. Therefore, reducing Engine noise can have a significant effect on the noise emitted by the vehicle. Engine noise can be divided into three categories: 1 - combustion noise 2 - mechanical noise 3 - aerodynamic noise. This project is in line with a project defined between the university and industry aimed at improving all sources of noise in the vehicle in question. The purpose of this research is to identify sources of noise in the engine and complete engine modeling for its NVH analysis. The conducted modeling provides the basis for studying the effect of different variables on Engine noise. Current research begins with the introduction of noise and vibration factors in the engine. The main focus of this research is on full engine modeling in Abaqus software. After the model was prepared, the dynamic analysis of the engine was performed in the AVL Excite Powerunit software. The acoustic analysis of the engine was performed to obtain noise from the engine by the AVL Excite Acoustics software. Due to the effect of each source of noise in the engine and its ability to be investigated, the noise generated by combustion and mechanical components are obtained through simulation. The results of these two software are verified by the vibrational and acoustical tests performed on the Engine. Due to the limitations of changing many parameters of noise factors that directly affect engine performance, The Engine noise reduction process is limited to checking the parameters of the valve and piston assembly. For this purpose, the optimal number of parameters for reducing Engine noise is obtained. By applying these optimal parameters, the Engine noise is reduced by one decibel. After reviewing the sources of noise, investigating the different sexes for the head of the helmet tried to improve the transmission paths of noise to the surrounding environment. With a change in the cylinder head from aluminum to cast iron, the engine noise level has dropped by a decibel. By making changes to improve engine noise, the engine noise level was reduced by about two dB
  9. Keywords:
  10. Engine Modeling ; Noise Pollution ; Mechanical Noise ; Aerodynamic Noise ; Vibrational Test Engine ; Piston Impact

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