Ammonia burning internal combustion engine

An ammonia burning internal combustion engine using ammonia as fuel, comprising:

• a combustion chamber;
• an exhaust passage;
• an injector for feeding the ammonia into the combustion chamber;
• a reformer reforming the ammonia and producing a reformed gas containing hydrogen therein, the reformed gas being fed into the combustion chamber in addition to the ammonia, a ratio of an amount of the ammonia fed to a total amount of fuel fed being defined as an ammonia ratio,
• an exhaust purification catalyst arranged in the exhaust passage;
• a secondary air feeding device arranged in the exhaust passage upstream of the exhaust purification catalyst to feed a secondary air into the exhaust passage upstream of the exhaust purification catalyst;
• a memory for storing the ammonia ratio after completion of engine warmup as a set ammonia ratio, the set ammonia ratio being set in advance in accordance with an operating state of the engine;
• and
• a control unit configured to control the ammonia ratio and a supply of the secondary air in accordance with a reforming ability of the reformer so as to increase the ammonia ratio over the set ammonia ratio and cause the secondary air to feed from the secondary air feeding device when the reforming ability is less than a predetermined reforming ability.