To achieve the applicability of a manifold branch model to different branch numbers

a multi-branch momentum conservation boundary model was derived. Firstly

on the basis of the continuity equation and energy equation

a multi-branch momentum conservation boundary model suitable for any number of branches was built considering the momentum change of working medium flowing through multi-branch junctions due to the influence of branch structures and flow parameters. Then

a shock tube test example was set up to compare and analyze the calculation accuracy and efficiency of such different multi-branch models as traditional isobaric model

pressure loss model and momentum conservation model. Finally

a simulation model was established for an internal combustion engine of high power density

and the prediction accuracy of the engine performance was compared with the traditional isobaric model and derived multi-branch momentum conservation boundary model. The results show that the derived model has better comprehensive advantages by balancing calculation accuracy and calculation efficiency on the basis of considering the model compressibility and applicability. For the high power density engine

the maximum prediction error of the engine performance at the rated speed with the traditional isobaric model is 7.58%

and that with the momentum conservation model is 2.47%. The prediction accuracy is greatly improved.