Method and apparatus for sealing a combustion chamber of a combustion system as well as a combustion system

The invention relates to a method and an apparatus (1) for sealing a combustion chamber (2) of a heat engine with external combustion comprising a Stirling engine (5), with respect to an environment (3), in particular for sealing a combustion chamber (2) between a premixing burner (4), the Stirling engine (5) and the environment (3). The invention further relates to a combustion system (10 with an apparatus (1) according to the invention. The seal is simply constructed and ensures a reliable seal. The method is characterised in that an overpressure with respect to a combustion chamber pressure is generated in a sealing zone. The apparatus (1) is characterised in that at a transition (6) to be sealed from the combustion chamber (2) to the environment (3), at least two sealing elements (8), which are spaced apart from one another and disposed one behind the other to form an intermediate chamber (7), are provided wherein the intermediate chamber (7) is connected fluidically to a cold medium supply. The combustion system (10) is characterised in that an apparatus (1) according to the invention is provided.