Robust Design Optimization For Automotive Fuel Tank Slosh Noise Depression

More and more attention is given to the NVH performance of a vehicle as the result of the growth of Chinese automotive market. This article introduces a noise that few people are aware of, fuel slosh noise. Fuel tank is a device to contain fuel for engine to combust on vehicle in automotive industry. It is often a thin container made of steel or plastic. Due to its special structure, it might create boring noise when vehicle is driving. New technology in automotive powertrain system will make this noise even more noticeable. Those new technologies include start and stop function, the hybrid system, etc.This case in the article comes from actual problem. The vehicle which has slosh noise problem is Multi-Purpose Vehicle. The package of its fuel tank is very special because of its unique body structure. The long side of the fuel tank is in the same direction of the driving direction of the vehicle, which results in higher kinetic energy accumulation during deceleration. Higher kinetic energy means higher vibration level and more obvious low frequency slosh noise generated when the liquid fuel hits the fuel tank body. The difficulties of this problem is how to analyze the systemic cause of fuel slosh noise and pick up the best solution with balance of cost, performance and other customer focuses. Besides, how to convert the problem into simplified mathematic model and optimize the design through DOE is another difficulty.In this article, analysis has been done regarding the systemic cause of fuel slosh noise according to noise and vibration theory. Different kinds of solutions are also presented to solve different kinds of root cause of the noise both in component level and system integration level.At the same time, Design for Six Sigma was introduced and it helps us solve the problem with methodical approach. Design for Six Sigma (DFSS) is a methodical approach to robust design. It does not only focus on improving the existing design or process. DFSS concentrates its efforts on creating a new and improved design or process. It requires applying resources to find out what customers'real needs are, and then devotes the entire project to meet those customers'demand and meet cost constraint at the same time.The workflow of DFSS can be regarded as I-D-D-O-V which means Identify, Define requirement, Develop concept, Optimize, and Verify. It requests to gather the voices of customers at the first place and convert them into engineering metrics by using QFD (Quality Function Deployment). QFD teaches us how to define proper engineering target which can lead the product to success with lowest cost.Following I-D-D-O-V process of DFSS and using CAE as a tool of analysis, we successfully optimize the fuel slosh noise by modifying the shape of fuel tank body. Final evaluation shows significant improvement than the previous version of the design.