A corporate PA-31 shut down the left engine and returned to the departure airport following the catastrophic failure of the left engine.

Narrative

After preflight my two passengers arrived; and we boarded the aircraft for departure. I departed on an IFR flight plan in Class D airspace and was handed off to Departure shortly after takeoff who approved a climb to 6;000 MSL. Climbing through approximately 2;700 MSL I heard the left engine make an unusual noise; and the manifold pressure on the left engine made a sudden slight decrease. All engine indicating instruments were in their appropriate ranges (green arcs). While visually observing the left engine it made a sudden change in sound and began to shake. A large amount of oil quickly started pouring out of the engine cowling; and upon reaching the exhaust and/or turbocharger the oil ignited into an engine fire. I then shut down and feathered the left engine.Shortly after shutting down the left engine the fire extinguished. I added power to the right engine and pointed the nose of the aircraft down to maintain sufficient airspeed. I finished securing the engine; established stable level flight and advised the passengers of the situation. I then told Approach I had to shut the left engine down and wanted vectors for the ILS to the runway. They vectored me for the approach and asked me to state fuel on board and souls on board.I established my aircraft on the ILS and the Tower cleared me to land and notified me that fire trucks were waiting. After landing I taxied back to the hangar and was followed in by a fire truck. Upon inspection of the aircraft after shutdown I found the left engine crank case shattered in many places. It appeared to be a connecting rod that broke loose and then proceeded to break apart the case until the engine was shut down. This engine had just 20 hours since major overhaul.