Low ratio oil injection port for applications without the requirement of an oil pump

A compression system comprising:

• an oil cooler that cools oil to be injected into a screw compressor;
• an oil separator that separates oil from compression gasses generated by the screw compressor;
• and
• the screw compressor, wherein the screw compressor comprises:
• a compressor housing that includes a cylindrical bore having an outer wall;
• a main rotor rotationally mounted within the cylindrical bore of the compressor housing, the main rotor including at least one helical groove that defines a compression chamber;
• and
• a gate rotor having a gear tooth that closes the compression chamber at a start of a compression cycle, travels through the compression chamber during the compression cycle, and exits the compression chamber at an end of the compression cycle;
• wherein compression gasses within the compression chamber have a pressure, the pressure being equal to suction pressure at the start of the compression cycle and increasing during the compression cycle to a discharge pressure at the end of the compression cycle;
• wherein the outer wall of the cylindrical bore includes an oil injection port that injects oil into the compression chamber during a time period and stops injecting oil into the compression period at the end of the time period partially through the compression cycle, and an average pressure ratio of the pressure of the compression gasses within the compression chamber relative to the suction pressure during the time period is less than about 1.8:1.

A method of operating a screw compressor, the method comprising:

• providing s screw compressor, wherein the screw compressor comprises:
• a compressor housing that includes a cylindrical bore having an outer wall, the outer wall of the cylindrical bore including an oil injection port;
• a main rotor rotationally mounted within the cylindrical bore of the compressor housing, the main rotor including at least one helical groove that defines a compression chamber;
• and
• a gate rotor having a gear tooth that closes the compression chamber at a start of a compression cycle, travels through the compression chamber during the compression cycle, and exits the compression chamber at an end of the compression cycle;
• conducting a compression cycle, wherein compression gasses within the compression chamber have a pressure, the pressure being equal to suction pressure at the start of the compression cycle and increasing during the compression cycle to a discharge pressure at the end of the compression cycle;
• and
• injecting oil into the compression chamber through the oil injection port during a time period and stopping injecting oil into the compression period at the end of the time period partially through the compression cycle;
• wherein an average pressure ratio of the pressure of the compression gasses within the compression chamber relative to the suction pressure during the time period is less than about 1.8:1.