Thermal fatigue test bench for variable thermal load engine system

The invention relates to the technical field of automobile power assembly tests, and discloses a variable thermal load engine system thermal fatigue test bench which comprises a rack, an engine is placed on the rack, a motor is arranged on the rack, a circulating gas pipeline is further arranged on the rack, and the circulating gas pipeline comprises a first exhaust manifold and a second exhaust manifold. The first exhaust manifold is connected with the air inlet side of the engine, the other end of the first exhaust manifold is connected with an outer circulation air inlet pipe, the second exhaust manifold is connected with the exhaust side of the engine, the other end of the second exhaust manifold is connected with an outer circulation exhaust pipe, and gate valves are arranged on the outer circulation air inlet pipe and the outer circulation exhaust pipe. The other end of the first exhaust manifold and the other end of the second exhaust manifold are further connected through a gas circuit switching devic