The internal combustion engine system includes:

The said internal combustion engine  includes the combustion chamber comprises of :

1. a moving cylinder head and liner assembly;
2. a piston with a hemispherical cavity; and
3. a flat cylinder head

The gaseous fuel delivery system comprises:

• gas storage tanks
• mass flow controllers
• mixing chamber
• a delivery line pressure sensor
• The controller is configured to vary the compression ratio of the internal combustion engine by varying the clearance volume of the combustion chamber by moving cylinder head and liner assembly.
• The outlet of the exhaust manifold is connected to the inlet of the intake manifold through an exhaust valve to recirculate the exhausted gases
• Data acquisition system based on a crank angle degree resolution of the crank angle encoder gets triggered, collects the data from the plurality of sensors and stores them in a memory associated with the system
• The gaseous fuel delivery system further comprises of a fuel metering device connected to the gaseous fuel outlet delivery line to meter the fuel.