Ventilation system

A ventilation system, comprising:

• a hydrogen engine;
• and
• a vehicle controller, wherein
• the hydrogen engine includes:
• an intake passage;
• a compressor of a forced-induction device arranged in the intake passage;
• a blow-by gas passage extending from a crankcase to a part of the intake passage located downstream of the compressor;
• a first positive crankcase ventilation (PCV) valve arranged in the blow-by gas passage and configured to open when a pressure of the intake passage at a downstream side of the compressor becomes lower than or equal to a first specified pressure that is lower than an atmospheric pressure;
• and
• a circulation passage extending from a part of the intake passage located upstream of the compressor to the crankcase,
• the vehicle controller includes processing circuitry,
• the processing circuitry is configured to execute a threshold value determination process that determines whether the pressure of the intake passage at the downstream side of the compressor is higher than or equal to a first threshold value that is lower than the atmospheric pressure, and
• when a condition that the pressure of the intake passage at the downstream side of the compressor is higher than or equal to the first threshold value is satisfied, the processing circuitry is configured to execute a ventilation process that drives the hydrogen engine so that the pressure of the intake passage at the downstream side of the compressor becomes lower than or equal to the first specified pressure.