Improvements relating to internal combustion engines

An ammonia-fuelled internal combustion engine system comprising:

• a cracking device connectable to an ammonia fuel supply and configured, during operation of the engine, to produce a cracked fuel comprising a mixture of nitrogen and hydrogen by cracking of an ammonia fuel provided by the ammonia fuel supply;
• a main combustion chamber, an intake and an exhaust each in fluid communication with the main combustion chamber;
• a precombustion chamber in fluid communication with the main combustion chamber via at least one orifice, the precombustion chamber further comprising a cracked fuel inlet to permit introduction of the cracked fuel, supplied from the cracking device, into the precombustion chamber;
• an ignition device operatively positioned with the precombustion chamber and configured to ignite the cracked fuel in the precombustion chamber, wherein the precombustion chamber and/or the orifice are configured to produce a stream of combusting fluid from the precombustion chamber to the main combustion chamber via the orifice, when cracked fuel is ignited in the precombustion chamber, so as to permit ignition of fuel present in the main combustion chamber;
• a sensor arrangement configured to measure properties of the cracked fuel;
• an electronic control device in communication with the sensor arrangement and with the ignition device, the electronic control device configured to evaluate a characteristic of the hydrogen present in the cracked fuel using measurements received from the sensor arrangement and to control introduction of cracked fuel into the precombustion chamber according to those evaluated hydrogen characteristics.

A method of modifying an internal combustion engine system to reconfigure the engine as an ammonia-fuelled engine system, the method comprising:

• fitting a precombustion chamber to a main combustion chamber of the internal combustion engine system with the precombustion chamber in fluid communication with the main combustion chamber via at least one orifice, the precombustion chamber comprising an ignition device configured to, during operation, permit ignition of fuel inside the precombustion chamber;
• installing a cracking device connectable to an ammonia fuel supply and configured, during operation, to produce a cracked fuel comprising a mixture of nitrogen and hydrogen by cracking of an ammonia fuel provided by the ammonia fuel supply;
• connecting the precombustion chamber to a supply of precombustion fuel comprising the cracked fuel obtained from the ammonia cracking device;
• installing a sensor arrangement configured to measure properties of the cracked fuel;
• installing or reconfiguring an electronic control device in electronic communication with the sensor arrangement and the ignition device, the electronic control device configured to evaluate a characteristic of the hydrogen present in the cracked fuel using measurements received from the sensor arrangement and to control introduction of cracked fuel into the precombustion chamber according to those evaluated hydrogen characteristics.

A method of operating an ammonia-fuelled internal combustion engine which comprises a precombustion chamber in fluid communication with a main combustion chamber, the method comprising:

• operating a cracking device fed with an ammonia fuel supply to produce a cracked fuel comprising a mixture of hydrogen and nitrogen;
• introducing a fuel into the main combustion chamber;
• introducing the cracked fuel from the cracking device into the precombustion chamber;
• igniting the cracked fuel in the precombustion chamber to produce a stream of combusting gases entering the main combustion chamber from the precombustion chamber to ignite the fuel present in the main combustion chamber;
• and
• controlling the introduction of cracked fuel into the precombustion chamber, using information received from a sensor arrangement associated with the cracked fuel.