Finite Element Analysis based Investigation to Evaluate Sealing Capability of High-Pressure Fuel Line Joints in IC Engine

For better fuel economy and reduced emissions; fuel system plays a very important role. There are some major challenges related to development of suitable fuel system due to high static (~2000 bar) and fluctuating pressures in high pressure (HP) fuel lines. This enforces to design leak proof joints as they directly affect engine operation and can cause customer inconvenience. It is also critical from safety standpoint. Sealing capability of a joint is generally evaluated by sealing pressure, length of the sealing width and retaining capability of joint preload over time. Theoretically, it is known that preload loss at a joint is a combination of several factors such as; thread pitch, nut stiffness and friction at threads. In our current work the cause of leakage in HP fuel line joints is explored. Using fish bone diagram for RCA (Root Cause Analysis), probable causes are narrowed down and design parameters responsible for preload loss are identified. A parametric study has been performed for different designs to evaluate their preload retaining capability. Additionally; end form of fuel joints, collar and frictional coefficient are studied to understand their impact on sealing capability as the part of this work. Sealing capability of two different engine platforms are evaluated through Finite Element Analysis (FEA) simulation and analytical methods. The results are validated through testing. The key findings of the current work can be useful in FEA and analytical modelling of HP fuel lines to evaluate joint sealing capability and will be helpful in designing better fuel line system in future.