Abstract: The invention concerns a device to generate mechanical work with a steam engine that works with a closed circuit and that has a feed water tank, a feed pump, an evaporator to generate steam, the steam engine, and a condenser. The invention is based on the problem of keeping a device of the initially cited kind free of damage from freezing water when the device is not operating and the environmental temperatures are low. To this end, an inert gas in the feed water tank (10) is used to expel the feed water from the other part (36) of the circuit to the feed water tank (10). This is done by switching a valve arrangement. The feed water tank (10) is designed so that it will not be damaged, for example by exploding from freezing water inside. The advantages of the closed circuit are retained. To restart the device, the system is reheated, and the valve arrangement only has to be switched back to the position suitable for normal operation.

Abstract: In a steam motor with a piston engine, the piston engine is included in a closed steam circuit. This steam circuit includes a steam generator, a steam injector for injecting steam into the piston engine, a condenser for condensing the steam emerging from the piston engine to condensed water, and a water feeding pump for feeding the condensed water to the steam generator. The steam generator is heated by hot combustion gas from a combustion unit. The combustion unit burns fuel. The fuel is mixed with fresh air supplied by an air feeding device through a fresh air passage. The fresh air passage usually contains a first heat exchanger for pre-heating the fresh air by heat from the expanded steam emerging from the piston engine, and a second heat exchanger for pre-heating the fresh air by heat from hot waste gas emerging from the steam generator. In order to provide a particularly compact steam motor without adversely affecting the efficiency, a rotary piston engine is used as piston engine.