Secondary filter element and filter system

A filter system for filtering a gaseous fluid and for pressure pulse self-cleaning in an air filtration system, comprising:

• a purging device configured for applying a back-washing cleaning pressure pulse;
• and
• a secondary filter element, comprising:
• a hollow cylinder-shaped central tube extending along and surrounding a longitudinal axis and having an open end,
• wherein, adjacent to the open end on a circumference of the hollow cylinder-shaped central tube, a circumferentially closed region having an axial length is formed;
• a filter medium arranged on and closing about a radially outer side of the hollow cylinder-shaped central tube, configured for the gaseous fluid to flow from a radially outer side of the filter medium to a radially inner side of the filter medium;
• wherein the radially outer side of the filter medium is an inflow side of the filter medium and
• the radially inner side of the filter medium is an outflow side of the filter medium;
• and
• wherein the circumferentially closed region covers at least one impact point of the back-washing cleaning pressure pulse applied by the purging device to impact the circumferentially closed region, thereby reducing a risk of damage to the filter medium from the back-washing cleaning pressure pulse;
• wherein the at least one impact point is arranged on the axial length of the circumferentially closed region between the filter medium and the open end of the hollow cylinder-shaped central tube;
• wherein the purging device comprises a purging pipe having a cone shaped diffuser adjacent an outlet end of the purging pipe, the cone shaped diffuser is configured to direct the back-washing cleaning pressure pulse onto the at least one impact point arranged on the axial length of the circumferentially closed region;
• and
• a support element arranged at and closing about the inflow side of the filter medium and having flow-through openings,
• wherein the support element has a proportion of an open surface provided for the flow-through openings to a closed surface of at most 85%, such that the support element covers and closes off at least 15% of a flow area of the inflow side of the filter medium, supporting and stabilizing the filter medium against the back-washing cleaning pressure pulse applied by the purging device.