To enable economical access to space through the use of an air breathing engine, major technical hurdles need to be overcome; in particular, skin friction drag. Skin friction drag can be reduced by film cooling or boundary layer combustor. But the main problem is using a technique which is able to sustain a sufficient amount of fuel in the boundary layer for both these mechanism to occur. Porous injectors are the most promising method to inject fuel into the boundary layer. However there is currently a gap in the literature on how to model them in Eilmer4. The porous injector was modelled by two different methods. The first method, a more simple approach, looked at setting a constant hydrogen inflow boundary condition along the edge of the combustor. The second method, a more realistic approach, used a user-defined fluid block which separated a high pressure hydrogen reservoir and the combustor. It was found that both these methods can model porous injectors in Eilmer4. It was also found that porous injectors are able to eliminate skin friction completely along the face of the combustor due to the zero velocity gradient along the length of the wall in the direction to the centre of the combustor. The porous injector is able to replenish the fuel faster than the crosswind is able to rip it off the wall. The relevance of this investigation is that it provides confidence in modelling porous injectors in Eilmer4 as well as gaining a new understanding on the skin friction reduction effects of a porous injector.