Apparatus and method for adjusting internal pressure of a ventilated closed space subject to change in external pressure

摘要

The enclosed space (1), e.g. a rail carriage, has ventilation ducts (5, 6) carrying inward (q1) and outward (q2) air-flows, differing by a quantity (qf) representing leakage. Each duct contains a fan (10) and an adjustable (14, 15) flow-control device (11). An internal pressure (P1) sensor (13) inputs to a regulator (12) operating both flow-control actuators (14, 15). A memory (16) records a selected reference pressure. Above this pressure, the regulator reduces the in-flow, leaving the out-flow duct open; below, the out-flow, only, is reduced. The regulator ensures, in real time, that the difference between instantaneous flows continually compensates for leakage, keeping the internal pressure constant. Optionally, separate compensating ducts are provided, parallel to the main ducts.