Abstract: Approaches to calculation of the flow losses in compoments of the combustor,such as diffuser,swirler and flame tube,and the flow losses in combustor under combustion conditions are investigated.The empiric formulae are derived from tests.They feature simplicity and sufficient accuracy and are applicable to design and redesign of combustor.The tests were conducted on the models of 4 types of diffusers,10 kinds of swirlers 7 types of flame tubes and,7 simulators of inlet flow field distortion.In comparison with the existing methods,the presented method considerably improves the calculation of the flow losses in the diffuser.For the swirler the correlation between flow resistance and the discharge coefficient and the formula for heating losses are also found out.