Internal combustion engine and method for controlling the internal combustion engine

An internal combustion engine, comprising:

• an oxidant supply device that supplies an oxidant into a combustion chamber;
• a reductant supply device that supplies a reductant, which is burned by reaction with the oxidant, into the combustion chamber;
• a circulation path which is communicated at both ends with the combustion chamber, into which exhaust gas generated after the reductant is burned in the combustion chamber flows through one of the both ends, from which gas that is taken in the combustion chamber flows into the combustion chamber through the other end, and through which working gas which is gas that has a specific heat ratio higher than a specific heat ratio of air and that is circulated back to the combustion chamber flows;
• and
• a supply amount setting unit that sets a supply amount of the reductant and a supply amount of the oxidant, wherein when the internal combustion engine is in a predetermined operating state, the supply amount setting unit sets the supply amount of the reductant and the supply amount of the oxidant in such a manner that one of a ratio of the supply amount of the reductant to the supply amount of the oxidant and a ratio of the supply amount of the oxidant to the supply amount of the reductant is higher than the one of the ratios used during normal operation.