Pulsejet simulations

This report describes a work in progress, where numerical simulations of two different kinds are used to study different aspects of the operation of a pulsejet. The two methods employed are: "full" simulations, where both the inlet valve and the combustion process are included in the model, and expansion simulations, where neither of these two aspects are included. In the second of these kind of simulations, the combustion process is neglected, except for an assumed, increased, homogeneous pressure in the combustor initially. Since the initial pressure due to the combustion is not known, several different values are used in the study. These simulations are performed in two dimensions. Since the combustion process is extremely complex, and since important aspects can be studied through the less demanding expansion simulations, it is fruitful to employ these less complex computations. For example, these types of simulations are used to illustrate the development of compression waves in the flow field; they are used to show the effect of choking, if the pressure in the combustor is too high; and they are also used to show the effect of running the engine with or without a flare at the exit. The full simulation are done in three dimensions, but in order to reduce the size of the computational problem, only a slice, representing one tenth of the engine (including one valve) is used in the computations. The results from these simulations are compared with experimental results. This report is somewhat unfocused to its character, disparate result are listed, without being tightly connected. The reason for this is that the project is ongoing, and when this part was ended there was a need to list the results from the work being done.