# US 10,245,543 B2 · Air filter systems and methods of using the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,245,543 B2 - Document ID: US10245543B2 - Status: Granted - Kind: B2 - Application number: 14/772,268 - Filed: 2014-03-04 - Published: 2016-01-21 - Granted: 2019-04-02 - Earliest claimed: 2013-03-04 - Assignees: Donaldson Company, Inc. - Applicants: Donaldson Company, Inc. - Inventors: Thomas D. Raether - Web page: https://patentgrep.com/patent/US10245543B2 ## CPC - B01D 46/71: with pressurised gas, e.g. pulsed air - B01D 46/2411: {Filter cartridges} - B01D 46/60: arranged concentrically or coaxially - B01D 46/0004: {Details of removable closures, lids, caps or filter heads} - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) ## Abstract The air filter systems described herein include one or more pulse collectors and pulse generators aligned along pulse axes. The pulse generators and filter elements may be arranged along a pulse distance as measured from a pulse outlet to a filter element opening. The pulse collectors and the filter elements may have openings with a relationship between them within parameters described herein. The pulse collectors may have a relationship between their hydraulic diameter and their length within parameters described herein. The pulse collectors may include a filter section and a pulse section that meet at a junction along a length of the pulse collector. The pulse sections may have a hydraulic diameter that increases when moving from the junction to the tube sheet opening of the pulse section. The filter sections may have a hydraulic diameter that remains constant when moving from the junction to the filter end opening of the filter section. Filter elements/cartridges used in the air filter systems may have filter media shaped or formed into ovate cross-sections. ## Claims ### Claim 1 An air filter system comprising: a tube sheet configured to separate a housing into a dirty air chamber and a clean air chamber; a pulse collector defining a passageway that extends through the pulse collector from a filter end opening at a filter end of the pulse collector element to a tube sheet opening at a tube sheet end of the pulse collector; an aperture in the tube sheet, wherein the tube sheet end of the pulse collector is configured for attachment to the tube sheet such that the tube sheet opening of the pulse collector is aligned with the aperture such that air passing from the dirty air chamber into the clean air chamber through the aperture passes through the passageway of the pulse collector; a filter element attached to the filter end of the pulse collector such that air passing into the passageway of the pulse collector through the filter end opening of the pulse collector passes through an interior volume of the filter element before reaching the filter end opening, wherein the filter element comprises a filter element opening at a junction between the filter end of the pulse collector and the filter element; a pulse generator located in the clean air chamber and positioned to deliver pulses of air into the interior volume of the filter element, the pulses of air passing through the aperture and the passageway of the pulse collector before reaching the interior volume of the filter element, wherein the pulse generator is configured to deliver the pulses of air along a pulse axis that extends from the pulse generator through the aperture in the tube sheet, the tube sheet opening in the pulse collector, and the filter end opening in the pulse collector, wherein the pulse generator comprises a pulse outlet located on the pulse axis and through which the pulses of air are delivered along the pulse axis, the pulse outlet defined by opposing walls that do not diverge with respect to the pulse axis, and wherein the pulse outlet defines a pulse outlet hydraulic diameter; and a yoke supporting the filter element, the yoke extending away from the pulse collector along the pulse axis, wherein the yoke comprises two or more support beams aligned with the pulse axis, wherein the two or more support beams are arranged asymmetrically about the pulse axis, and wherein the filter element comprises an end cap comprising notches that align with and receive the two or more support beams when the filter element is in only one rotational orientation relative to the pulse axis; wherein a pulse distance measured along the pulse axis from the pulse outlet to the filter element opening is 30 or more times the pulse outlet hydraulic diameter. ### Claim 2 (depends on 1) A system according to claim 1, wherein the pulse distance is within a range that is 50 times or less and 30 times or more the pulse outlet hydraulic diameter. ### Claim 3 (depends on 1) A system according to claim 1, wherein a hydraulic diameter of the filter element opening is 112% or less of a hydraulic diameter of the filter end opening of the pulse collector. ### Claim 4 (depends on 1) A system according to claim 1, wherein the hydraulic diameter of the filter element opening is within a range that is 90% or more of the hydraulic diameter of the filter end opening of the pulse collector and 112% or less of a hydraulic diameter of the filter end opening of the pulse collector. ### Claim 5 (depends on 1) A system according to claim 1, wherein an absolute value of a difference between a hydraulic diameter of the filter element opening and a hydraulic diameter of the filter end opening of the pulse collector is within 2% or less of the hydraulic diameter of the filter element opening. ### Claim 6 (depends on 1) A system according to claim 1, wherein the pulse collector comprises a filter section and a pulse section, wherein the filter section and the pulse section meet at a junction located between the filter end and the tube sheet end of the pulse collector; wherein a portion of the passageway defined by the pulse section comprises a hydraulic diameter that increases when moving from the junction to the tube sheet opening; and wherein a portion of the passageway defined by the filter section comprises a hydraulic diameter that remains constant when moving from the junction to the filter end. ### Claim 7 (depends on 6) A system according to claim 6, wherein the filter section comprises a filter section length measured along the pulse axis from the filter end to the junction and the pulse section comprises a pulse section length measured along the pulse axis from the tube sheet end to the junction, wherein the filter section length is less than or equal to the pulse section length. ### Claim 8 (depends on 6) A system according to claim 6, wherein the pulse section comprises opposing walls defining the portion of the passageway in the pulse section that diverge from the pulse axis at an included angle that is greater than zero (0) degrees and less than or equal to ten (10) degrees. ### Claim 9 An air filter system comprising: a tube sheet configured to separate a housing into a dirty air chamber and a clean air chamber; a pulse collector defining a passageway that extends through the pulse collector from a filter end opening at a filter end of the pulse collector element to a tube sheet opening at a tube sheet end of the pulse collector; an aperture in the tube sheet, wherein the tube sheet end of the pulse collector is configured for attachment to the tube sheet such that the tube sheet opening of the pulse collector is aligned with the aperture such that air passing from the dirty air chamber into the clean air chamber through the aperture passes through the passageway of the pulse collector; a filter element attached to the filter end of the pulse collector such that air passing into the passageway of the pulse collector through the filter end opening of the pulse collector passes through an interior volume of the filter element before reaching the filter end opening, wherein the filter element comprises a filter element opening at a junction between the filter end of the pulse collector and the filter element; a pulse generator located in the clean air chamber and positioned to deliver pulses of air into the interior volume of the filter element, the pulses of air passing through the aperture and the passageway of the pulse collector before reaching the interior volume of the filter element, wherein the pulse generator is configured to deliver the pulses of air along a pulse axis that extends from the pulse generator through the aperture in the tube sheet, the tube sheet opening in the pulse collector, and the filter end opening in the pulse collector, wherein the pulse generator comprises a pulse outlet located on the pulse axis and through which the pulses of air are delivered along the pulse axis, the pulse outlet defined by opposing walls that do not diverge with respect to the pulse axis, and wherein the pulse outlet defines a pulse outlet hydraulic diameter; wherein the filter element is supported on a yoke extending away from the pulse collector along the pulse axis, wherein the yoke comprises two or more support beams aligned with the pulse axis, wherein the two or more support beams are arranged asymmetrically about the pulse axis, and wherein the filter element opening comprises alignment features arranged to align with the two or more support beams when the filter element is in only one rotational orientation relative to the pulse axis; and wherein a pulse distance measured along the pulse axis from the pulse outlet to the filter element opening is 30 or more times the pulse outlet hydraulic diameter. ### Claim 10 (depends on 9) A system according to claim 9, wherein the pulse distance is within a range that is 50 times or less and 30 times or more the pulse outlet hydraulic diameter. ### Claim 11 (depends on 9) A system according to claim 9, wherein a hydraulic diameter of the filter element opening is 112% or less of a hydraulic diameter of the filter end opening of the pulse collector. ### Claim 12 (depends on 9) A system according to claim 9, wherein the hydraulic diameter of the filter element opening is within a range that is 90% or more of the hydraulic diameter of the filter end opening of the pulse collector and 112% or less of a hydraulic diameter of the filter end opening of the pulse collector. ### Claim 13 (depends on 9) A system according to claim 9, wherein an absolute value of a difference between a hydraulic diameter of the filter element opening and a hydraulic diameter of the filter end opening of the pulse collector is within 2% or less of the hydraulic diameter of the filter element opening. ### Claim 14 (depends on 9) A system according to claim 9, wherein the pulse collector comprises a filter section and a pulse section, wherein the filter section and the pulse section meet at a junction located between the filter end and the tube sheet end of the pulse collector; wherein a portion of the passageway defined by the pulse section comprises a hydraulic diameter that increases when moving from the junction to the tube sheet opening; and wherein a portion of the passageway defined by the filter section comprises a hydraulic diameter that remains constant when moving from the junction to the filter end. ### Claim 15 (depends on 14) A system according to claim 14, wherein the filter section comprises a filter section length measured along the pulse axis from the filter end to the junction and the pulse section comprises a pulse section length measured along the pulse axis from the tube sheet end to the junction, wherein the filter section length is less than or equal to the pulse section length. ### Claim 16 (depends on 14) A system according to claim 14, wherein the pulse section comprises opposing walls defining the portion of the passageway in the pulse section that diverge from the pulse axis at an included angle that is greater than zero (0) degrees and less than or equal to ten (10) degrees. ### Claim 17 (depends on 9) A system according to claim 9, wherein a diverging pulse guide is operably connected to the pulse generator, wherein the pulses of air from the pulse generator pass through the diverging pulse guide, and wherein the diverging pulse guide comprises: a tubular wall comprising a connector end connected to the pulse generator and an open end located distal from the connector end; an interior channel extending through the diverging pulse guide from the connector end to the open end, wherein the interior channel defines a channel length extending from the connector end to the open end and a channel width defined by opposing interior surfaces of the tubular wall, wherein the channel length extends along a longitudinal axis and wherein the channel width extends transverse to the longitudinal axis; wherein the interior channel comprises a first section proximate the connector end and a second section proximate the open end such that the first section is located between the second section and the connector end and the second section is located between the first section and the open end; wherein the opposing interior surfaces of the diverging pulse guide in the first section diverge from the longitudinal axis at a first angle, wherein the first angle is greater than zero (0) degrees; wherein the opposing interior surfaces of the diverging pulse guide in the second section diverge from the longitudinal axis at a second angle that is greater than the first angle. ### Claim 18 (depends on 17) A system according to claim 17, wherein the second section of the interior channel comprises a second section length measured along the longitudinal axis that greater than the channel width at the connector end. ### Claim 19 An air filter system comprising: a tube sheet configured to separate a housing into a dirty air chamber and a clean air chamber; a pulse collector defining a passageway that extends through the pulse collector from a filter end opening at a filter end of the pulse collector element to a tube sheet opening at a tube sheet end of the pulse collector; an aperture in the tube sheet, wherein the tube sheet end of the pulse collector is configured for attachment to the tube sheet such that the tube sheet opening of the pulse collector is aligned with the aperture such that air passing from the dirty air chamber into the clean air chamber through the aperture passes through the passageway of the pulse collector; a filter element attached to the filter end of the pulse collector such that air passing into the passageway of the pulse collector through the filter end opening of the pulse collector passes through an interior volume of the filter element before reaching the filter end opening, wherein the filter element comprises a filter element opening at a junction between the filter end of the pulse collector and the filter element; a yoke supporting the filter element, the yoke extending away from the pulse collector along the pulse axis, wherein the yoke comprises two or more support beams aligned with the pulse axis, wherein the two or more support beams are arranged asymmetrically about the pulse axis, and wherein the filter element opening comprises alignment features arranged to align with the two or more support beams when the filter element is in only one rotational orientation relative to the pulse axis; a pulse generator located in the clean air chamber and positioned to deliver pulses of air into the interior volume of the filter element, the pulses of air passing through the aperture and the passageway of the pulse collector before reaching the interior volume of the filter element, wherein the pulse generator is configured to deliver the pulses of air along a pulse axis that extends from the pulse generator through the aperture in the tube sheet, the tube sheet opening in the pulse collector, and the filter end opening in the pulse collector, wherein the pulse generator comprises a pulse outlet located on the pulse axis and through which the pulses of air are delivered along the pulse axis, the pulse outlet defined by opposing walls that do not diverge with respect to the pulse axis, and wherein the pulse outlet defines a pulse outlet hydraulic diameter; and a diverging pulse guide operably connected to the pulse generator, wherein the pulses of air from the pulse generator pass through the diverging pulse guide, and wherein the diverging pulse guide comprises: a tubular wall comprising a connector end connected to the pulse generator and an open end located distal from the connector end; an interior channel extending through the diverging pulse guide from the connector end to the open end, wherein the interior channel defines a channel length extending from the connector end to the open end and a channel width defined by opposing interior surfaces of the tubular wall, wherein the channel length extends along a longitudinal axis and wherein the channel width extends transverse to the longitudinal axis; wherein the interior channel comprises a first section proximate the connector end and a second section proximate the open end such that the first section is located between the second section and the connector end and the second section is located between the first section and the open end; wherein the opposing interior surfaces of the diverging pulse guide in the first section diverge from the longitudinal axis at a first angle, wherein the first angle is greater than zero (0) degrees; wherein the opposing interior surfaces of the diverging pulse guide in the second section diverge from the longitudinal axis at a second angle that is greater than the first angle; wherein a pulse distance measured along the pulse axis from the pulse outlet to the filter element opening is 30 or more times the pulse outlet hydraulic diameter. ### Claim 20 (depends on 19) A system according to claim 19, wherein the pulse distance is within a range that is 50 times or less and 30 times or more the pulse outlet hydraulic diameter. ### Claim 21 (depends on 19) A system according to claim 19, wherein a hydraulic diameter of the filter element opening is 112% or less of a hydraulic diameter of the filter end opening of the pulse collector. ### Claim 22 (depends on 19) A system according to claim 19, wherein the hydraulic diameter of the filter element opening is within a range that is 90% or more of the hydraulic diameter of the filter end opening of the pulse collector and 112% or less of a hydraulic diameter of the filter end opening of the pulse collector. ### Claim 23 (depends on 19) A system according to claim 19, wherein an absolute value of a difference between a hydraulic diameter of the filter element opening and a hydraulic diameter of the filter end opening of the pulse collector is within 2% or less of the hydraulic diameter of the filter element opening. ### Claim 24 (depends on 19) A system according to claim 19, wherein the pulse collector comprises a filter section and a pulse section, wherein the filter section and the pulse section meet at a junction located between the filter end and the tube sheet end of the pulse collector; wherein a portion of the passageway defined by the pulse section comprises a hydraulic diameter that increases when moving from the junction to the tube sheet opening; and wherein a portion of the passageway defined by the filter section comprises a hydraulic diameter that remains constant when moving from the junction to the filter end. ### Claim 25 (depends on 24) A system according to claim 24, wherein the filter section comprises a filter section length measured along the pulse axis from the filter end to the junction and the pulse section comprises a pulse section length measured along the pulse axis from the tube sheet end to the junction, wherein the filter section length is less than or equal to the pulse section length. ### Claim 26 (depends on 24) A system according to claim 24, wherein the pulse section comprises opposing walls defining the portion of the passageway in the pulse section that diverge from the pulse axis at an included angle that is greater than zero (0) degrees and less than or equal to ten (10) degrees. ### Claim 27 (depends on 19) A system according to claim 19, wherein the second section of the interior channel comprises a second section length measured along the longitudinal axis that greater than the channel width at the connector end. ### Claim 28 An air filter system comprising: a tube sheet configured to separate a housing into a dirty air chamber and a clean air chamber; a pulse collector defining a passageway that extends through the pulse collector from a filter end opening at a filter end of the pulse collector element to a tube sheet opening at a tube sheet end of the pulse collector; an aperture in the tube sheet, wherein the tube sheet end of the pulse collector is configured for attachment to the tube sheet such that the tube sheet opening of the pulse collector is aligned with the aperture such that air passing from the dirty air chamber into the clean air chamber through the aperture passes through the passageway of the pulse collector; a filter element attached to the filter end of the pulse collector such that air passing into the passageway of the pulse collector through the filter end opening of the pulse collector passes through an interior volume of the filter element before reaching the filter end opening, wherein the filter element comprises a filter element opening at a junction between the filter end of the pulse collector and the filter element; a pulse generator located in the clean air chamber and positioned to deliver pulses of air into the interior volume of the filter element, the pulses of air passing through the aperture and the passageway of the pulse collector before reaching the interior volume of the filter element, wherein the pulse generator is configured to deliver the pulses of air along a pulse axis that extends from the pulse generator through the aperture in the tube sheet, the tube sheet opening in the pulse collector, and the filter end opening in the pulse collector, wherein the pulse generator comprises a pulse outlet located on the pulse axis and through which the pulses of air are delivered along the pulse axis, the pulse outlet defined by opposing walls that do not diverge with respect to the pulse axis, and wherein the pulse outlet defines a pulse outlet hydraulic diameter; a diverging pulse guide operably connected to the pulse generator, wherein the pulses of air from the pulse generator pass through the diverging pulse guide, and wherein the diverging pulse guide comprises: a tubular wall comprising a connector end connected to the pulse generator and an open end located distal from the connector end; an interior channel extending through the diverging pulse guide from the connector end to the open end, wherein the interior channel defines a channel length extending from the connector end to the open end and a channel width defined by opposing interior surfaces of the tubular wall, wherein the channel length extends along a longitudinal axis and wherein the channel width extends transverse to the longitudinal axis; wherein the interior channel comprises a first section proximate the connector end and a second section proximate the open end such that the first section is located between the second section and the connector end and the second section is located between the first section and the open end; wherein the opposing interior surfaces of the diverging pulse guide in the first section diverge from the longitudinal axis at a first angle, wherein the first angle is greater than zero (0) degrees; wherein the opposing interior surfaces of the diverging pulse guide in the second section diverge from the longitudinal axis at a second angle that is greater than the first angle; and a yoke supporting the filter element, the yoke extending away from the pulse collector along the pulse axis, wherein the yoke comprises two or more support beams aligned with the pulse axis, wherein the two or more support beams are arranged asymmetrically about the pulse axis, and wherein the filter element comprises an end cap comprising notches that align with and receive the two or more support beams when the filter element is in only one rotational orientation relative to the pulse axis; wherein a pulse distance measured along the pulse axis from the pulse outlet to the filter element opening is 30 or more times the pulse outlet hydraulic diameter. ### Claim 29 (depends on 28) A system according to claim 28, wherein the pulse distance is within a range that is 50 times or less and 30 times or more the pulse outlet hydraulic diameter. ### Claim 30 (depends on 28) A system according to claim 28, wherein a hydraulic diameter of the filter element opening is 112% or less of a hydraulic diameter of the filter end opening of the pulse collector. ### Claim 31 (depends on 28) A system according to claim 28, wherein the hydraulic diameter of the filter element opening is within a range that is 90% or more of the hydraulic diameter of the filter end opening of the pulse collector and 112% or less of a hydraulic diameter of the filter end opening of the pulse collector. ### Claim 32 (depends on 28) A system according to claim 28, wherein an absolute value of a difference between a hydraulic diameter of the filter element opening and a hydraulic diameter of the filter end opening of the pulse collector is within 2% or less of the hydraulic diameter of the filter element opening. ### Claim 33 (depends on 28) A system according to claim 28, wherein the pulse collector comprises a filter section and a pulse section, wherein the filter section and the pulse section meet at a junction located between the filter end and the tube sheet end of the pulse collector; wherein a portion of the passageway defined by the pulse section comprises a hydraulic diameter that increases when moving from the junction to the tube sheet opening; and wherein a portion of the passageway defined by the filter section comprises a hydraulic diameter that remains constant when moving from the junction to the filter end. ### Claim 34 (depends on 33) A system according to claim 33, wherein the filter section comprises a filter section length measured along the pulse axis from the filter end to the junction and the pulse section comprises a pulse section length measured along the pulse axis from the tube sheet end to the junction, wherein the filter section length is less than or equal to the pulse section length. ### Claim 35 (depends on 33) A system according to claim 33, wherein the pulse section comprises opposing walls defining the portion of the passageway in the pulse section that diverge from the pulse axis at an included angle that is greater than zero (0) degrees and less than or equal to ten (10) degrees. ### Claim 36 (depends on 28) A system according to claim 28, wherein the second section of the interior channel comprises a second section length measured along the longitudinal axis that greater than the channel width at the connector end. ### Claim 37 An air filter system comprising: a tube sheet configured to separate a housing into a dirty air chamber and a clean air chamber; a pulse collector defining a passageway that extends through the pulse collector from a filter end opening at a filter end of the pulse collector element to a tube sheet opening at a tube sheet end of the pulse collector; an aperture in the tube sheet, wherein the tube sheet end of the pulse collector is configured for attachment to the tube sheet such that the tube sheet opening of the pulse collector is aligned with the aperture such that air passing from the dirty air chamber into the clean air chamber through the aperture passes through the passageway of the pulse collector; a filter element attached to the filter end of the pulse collector such that air passing into the passageway of the pulse collector through the filter end opening of the pulse collector passes through an interior volume of the filter element before reaching the filter end opening, wherein the filter element comprises a filter element opening at a junction between the filter end of the pulse collector and the filter element; a pulse generator located in the clean air chamber and positioned to deliver pulses of air into the interior volume of the filter element, the pulses of air passing through the aperture and the passageway of the pulse collector before reaching the interior volume of the filter element, wherein the pulse generator is configured to deliver the pulses of air along a pulse axis that extends from the pulse generator through the aperture in the tube sheet, the tube sheet opening in the pulse collector, and the filter end opening in the pulse collector, wherein the pulse generator comprises a pulse outlet located on the pulse axis and through which the pulses of air are delivered along the pulse axis, the pulse outlet defined by opposing walls that do not diverge with respect to the pulse axis, and wherein the pulse outlet defines a pulse outlet hydraulic diameter; and a diverging pulse guide operably connected to the pulse generator, wherein the pulses of air from the pulse generator pass through the diverging pulse guide, and wherein the diverging pulse guide comprises: a tubular wall comprising a connector end connected to the pulse generator and an open end located distal from the connector end; an interior channel extending through the diverging pulse guide from the connector end to the open end, wherein the interior channel defines a channel length extending from the connector end to the open end and a channel width defined by opposing interior surfaces of the tubular wall, wherein the channel length extends along a longitudinal axis and wherein the channel width extends transverse to the longitudinal axis; wherein the interior channel comprises a first section proximate the connector end and a second section proximate the open end such that the first section is located between the second section and the connector end and the second section is located between the first section and the open end; wherein the opposing interior surfaces of the diverging pulse guide in the first section diverge from the longitudinal axis at a first angle, wherein the first angle is greater than zero (0) degrees; wherein the opposing interior surfaces of the diverging pulse guide in the second section diverge from the longitudinal axis at a second angle that is greater than the first angle; wherein the second section of the interior channel comprises a second section length measured along the longitudinal axis that greater than the channel width at the connector end; wherein a pulse distance measured along the pulse axis from the pulse outlet to the filter element opening is 30 or more times the pulse outlet hydraulic diameter. ### Claim 38 (depends on 37) A system according to claim 37, wherein the pulse distance is within a range that is 50 times or less and 30 times or more the pulse outlet hydraulic diameter. ### Claim 39 (depends on 37) A system according to claim 37, wherein a hydraulic diameter of the filter element opening is 112% or less of a hydraulic diameter of the filter end opening of the pulse collector. ### Claim 40 (depends on 37) A system according to claim 37, wherein the hydraulic diameter of the filter element opening is within a range that is 90% or more of the hydraulic diameter of the filter end opening of the pulse collector and 112% or less of a hydraulic diameter of the filter end opening of the pulse collector. ### Claim 41 (depends on 37) A system according to claim 37, wherein an absolute value of a difference between a hydraulic diameter of the filter element opening and a hydraulic diameter of the filter end opening of the pulse collector is within 2% or less of the hydraulic diameter of the filter element opening. ### Claim 42 (depends on 37) A system according to claim 37, wherein the pulse collector comprises a filter section and a pulse section, wherein the filter section and the pulse section meet at a junction located between the filter end and the tube sheet end of the pulse collector; wherein a portion of the passageway defined by the pulse section comprises a hydraulic diameter that increases when moving from the junction to the tube sheet opening; and wherein a portion of the passageway defined by the filter section comprises a hydraulic diameter that remains constant when moving from the junction to the filter end. ### Claim 43 (depends on 42) A system according to claim 42, wherein the filter section comprises a filter section length measured along the pulse axis from the filter end to the junction and the pulse section comprises a pulse section length measured along the pulse axis from the tube sheet end to the junction, wherein the filter section length is less than or equal to the pulse section length. ### Claim 44 (depends on 42) A system according to claim 42, wherein the pulse section comprises opposing walls defining the portion of the passageway in the pulse section that diverge from the pulse axis at an included angle that is greater than zero (0) degrees and less than or equal to ten (10) degrees.