Abstract: A conical filter device inserts into a duct having flow passing from upstream to downstream. The filter device includes fluted filter media having flutes formed therein and a housing. The filter forms a seal between the outer edge of the filter at the downstream side and the housing. The upstream face of the filter is conical shaped in a first embodiment and frusto-conical in a second embodiment with the housing roughly corresponding to the shape of the filter. The filter elements are formed by winding layers of filter media to form a circular cross-section. The elements are moved axially as they are wound or placed on a shaping form while the sealant is still pliable to shape the element.

Abstract: A filter device inserts into a duct having flow passing from upstream to downstream. The filter device includes fluted filter media having flutes formed therein. The filter forms a seal between the outer edge of the filter and the downstream side of the duct. The filter media may be rolled or stacked in layers to match the shape of the duct.

Abstract: A filter device inserts into a duct having flow passing from upstream to downstream. The filter device includes fluted filter media having flutes formed therein inserting into a housing. The filter media is stacked and placed at an angle to the prevailing flow direction.

Abstract: A filter-cleaning apparatus utilizes pulsed air to remove matter collected on a first surface of a filter. Reverse flow loosens the material which is collected in a hopper on the upstream side of the filter. The collected matter may then be combusted in the hopper so that the amount of material collected is minimized. The pulses are directed at the filter with a controlled shape and time to optimize reverse pulsing. Pulsing occurs while the thermal exhaust flow continues so that operation of the engine is not interrupted. A number of valves may be utilized to clean one or more filters.