Extension of the universal erosive burning law to partly symmetric propellant grain geometries

• Detailed 3-D viscous calculations are performed to study the flow phenomena inside practical motor configurations.
• Existing Erosive burning model for symmetric propellant is extended for asymmetric configurations.
• The improved model worked nicely for finocyl configuration with highly loaded grain.

This paper aims at extending the universal erosive burning law developed by two of the present authors from axi-symmetric internally burning grains to partly symmetric burning grains. This extension revolves around three dimensional flow calculations inside highly loaded grain geometry and benefiting from an observation that the flow gradients normal to the surface in such geometries have a smooth behavior along the perimeter of the grain. These are used to help identify the diameter that gives the same perimeter the characteristic dimension rather than a mean hydraulic diameter chosen earlier. The predictions of highly loaded grains from the newly chosen dimension in the erosive burning law show better comparison with measured pressure–time curves while those with mean hydraulic diameter definitely over-predict the pressures.