A Methodology to Validate the V-band Clamp Used in High-Temperature Sealing Joint of a Light-Duty Diesel Engine 2022-01-0637

The stringent emission regulations demand highly complex after-treatment systems. The packaging and functional requirements of the after-treatment system demand very close coupling of the diesel oxidation catalyst (DOC) with the turbocharger outlet. The sealing effectiveness between the turbocharger and DOC is ensured by the V-band grooved clamp along with the suitable gasket. This V-band grooved clamp is widely used in diesel engines due to its ease of assembly and low cost. Since the V-band grooved clamp is subjected to a very high temperature, vibration, thermal shock, a robust and holistic validation is required to ensure the functional and safety requirements. Despite its wide range of applications, the testing and validation methodologies required to effectively validate the strength and other aspects of the clamp are not fully defined. In the present work, the authors discuss the various design validation methods involved during the development of the V-band grooved clamp.

Detailed finite element analysis was performed to determine the axial load generated by the V-band grooved clamp for the specified torque. The cross-section profile of the V-band grooved clamp was optimized to improve the axial contact pressure for the specified tightening torque. Moreover, the conical surfaces of the interface parts (turbocharger, DOC) were optimized together to achieve better results. The predicted axial load was validated by the experimental method and found to be having a good correlation. The typical construction of the V-band grooved clamp is to have a bridge at the middle which is welded to the clamp shells at both ends. Hence, validation of the welding joint is extremely important to assess the durability of the clamp design. A unique method was adapted to test the welding strength such as weld pull and weld-peel. The structural integrity of the V- band grooved clamp was confirmed by tightening it up to 125% of the nominal torque to ensure robustness. This was done to increase Factor of Safety (FOS) with higher loading to cater to the harsh real-world usage patterns. The part level inspection and sealing pressure measurements (Fuji-film) confirm that the design of the V-band grooved clamp was robust enough for the given application. The present work also gives an insight into the criticalities involved while developing a V-band grooved clamp for a mass-production light-duty diesel engine meant for Bharat Stage VI (BS-VI) emission regulations.