Definition

The high pressure compressor (HPC) is the section of a twin-spool jet engine that provides the final stage of compression for air ingested by the engine. 

Description

A basic jet engine consists of an intake section, a compressor section, a combustion section, and an exhaust section. Exhaust air flowing over the turbines provides the spinning motion to turn the engine shaft. Compressor blades attached at the front of the shaft squeeze the air to a desired level before it enters the combustion section. In the combustion section, the air is mixed with fuel and ignited. The extremely hot exhaust air exits the rear of the engine at a much greater pressure than the air entering the front of the engine, thus providing propulsion. A jet engine operates on Sir Isaac Newton’s principle that “for every action there is an equal and opposite reaction.”

A twin-spool design offers a more efficient refinement on the basic jet engine. In a twin-spool engine, two sets of compressors and two sets of turbines spin around a shaft within a shaft. A low-pressure compressor receives intake air and provides an initial stage of compression. The air continues into the high-pressure compressor for an even greater stage of compression. When the compressed air is mixed with fuel and ignited, it first flows over a high-pressure turbine. The high-pressure turbine extracts energy from the hot gases to spin the high-pressure compressor. Similarly, exhaust air flowing over the low-pressure turbine provides energy to spin the low-pressure compressor. The process is self-sustaining until the supply of fuel or air is removed.