The present invention relates to a lean direct injection (LDI) combustion system (10) for a gas turbine using a shell and tube heat exchanger concept to construct a shell and tube lean direct injector ('LDI')(14) for the combustion system (10). One side of the LDI injector (14), either the shell side (16) or the tube side (18) , carries an oxidizer, such as air, to the combustor (12), while the other side of the LDI injector (14) carries fuel to the combustor (14). Straight or angled holes (34,38) drilled in an end plate (32) of the combustor (12) allow the fuel to enter the combustor (12) and mix with air being injected into the combustor (12).