In gas turbine engines, the combustor performance directly impacts the overall fuel efficiency of the gas turbine engine and the pollutant emission.  Heat shields, also known as float walls, have therefore been provided within combustors to allow the combustor to operate at higher temperatures with relatively low combustor pressure drops.  As a result, the specific field consumption of gas turbine engines is enhanced. 
For cooling purposes, the heat shields may be equipped with a plurality of pin fins oriented away from the combustion zone of the combustor.  A coolant fluid circulates between the pin fins, thereby cooling the heat shields.  Spent coolant fluid is then directed onto the exposed surface of the heat shields to perform film cooling.  The fluid coolants are therefore used for two different types of cooling, namely internally through the pin array and externally via film cooling. 
Fresh coolant fluid is introduced where film cooling effectiveness dies.  Accordingly, coolant fluid introduction has an impact on the axial length of the heat shields.  To ensure optimal coolant distribution, some circumferential rails and like deflectors have been added among pin fin arrays.  However, such rails may introduce undesirable extra contact points, extra hot spots and stiffness discontinuity and this may have an impact on the overall durability of the heat shields.