Supercharger Ventilator

Beginning with the T-55 in 1958, Soviet military combat vehicles with enclosed crew compartments were provided a ventilator that could ensure collective protection from an irradiated environment. For combat vehicles intended to operate near or within the front lines, the airborne radiological threat was mainly posed by irradiated particles suspended in the air immediately following a nuclear detonation and the destruction that would entail. This would be followed by nuclear fallout. To protect the crew of an enclosed vehicle from radioactive particles, a supercharger ventilator with a centrifugal dust separator was provided, to ensure an internal overpressure with purified air. The term supercharger refers to the fact that it generates a pressure in excess of 1 atm within the crew compartment. In practice, it is merely a relatively weak blower that is capable of sustaining an excess pressure.

The ventilator has two settings; normal and supercharger. This is effectively analogous to a 'low' and 'high' mode.

Referring to the drawing above, the supercharger is a two-stage centrifugal compressor consisting of a first stage impeller (6) with 40 vanes, and a second stage impeller with 160 vanes (3) which wrap around the electric fan motor. The first stage impeller modestly increases the air pressure, and then the second stage impeller strongly increases the air pressure. Due to the centrifugal action of the second stage impeller, dust particles, possessing a high inertia relative to air, are thrown against a slotted screen (8) where they are channeled out of the ventilator through a vent on the side, along with moisture and a large amount of air. The remaining air flowing between the impeller vanes proceeds out of the ventilator through the rear end.

The centrifugal method of dust separation was highly inefficient, as up to 50% of the total outgoing air would exit via the dust channel, so a much more powerful supercharger would be needed to generate the required overpressure. This inefficiency was partly leveraged to ensure that contaminated air does not enter the vehicle via the dust removal slit, although in this case, the large size of the dust vent slit was also an inefficient feature of this type of supercharger.

In the normal mode, the fan operates at a lower power, where the low air pressure results in lower dust separation effectiveness, but also lower flow loss. In this mode, the ventilator functions as a normal blower without the capacity to generate an overpressure when the vehicle hatches are sealed.  

Compared to the simple ventilator fans used in domestic vehicles previously, the supercharger ventilator provided more effective ventilation, not only in terms of air flow rate, but also in that it purifies the air from dust in general use. When driving in dry and dusty regions, usage of the ventilator in the supercharger mode improves the quality of air inside the vehicle compared to the simple ventilator fans of the past. In hot and humid environments, the dehumidification action of the ventilator also helps to improve crew working conditions.

This type of supercharger ventilator was standard in Soviet military combat vehicles throughout the 1960's, and continued to be fitted until the early 1970's, when a more efficient inertial-type dust separator was used to replace the centrifugal dust separator, and HEPA filter cartridges were incorporated to provide biological and chemical protection.