Offline measurement of cellular filtration efficiency

Abstract

This invention discloses an apparatus and method for determining the filtration efficiency of a filter body even in a clean state. One or more embodiments of this disclosure relate to a method for determining the filtration efficiency of a filter consisting of a porous wall portion having a longitudinal axis extending from an inlet end (202) to an outlet end (204), and an outer peripheral portion extending parallel to the longitudinal axis and surrounding the porous wall portion. The method includes: sealing the outer peripheral portion; forcing an inlet flow consisting of gas into the inlet end (202) of the filter at a set flow rate; introducing particles, such as smoke particles, into the inlet flow; and optically counting the number of particles entering and leaving the filter during a sampling event, for example using diffraction-based optical particle counters located upstream and downstream of the filter.

Description

Technical Field

[0001] The embodiments disclosed herein generally relate to methods and apparatus for offline measurement of filtration efficiency of cellular structures. Background Technology

[0002] Particulate filters, such as diesel particulate filters and gasoline particulate filters (GPFs), filter particles from the exhaust gas stream of engines (e.g., motor vehicles that burn diesel and gasoline fuels, respectively). Evaluating the filtration efficiency of particulate filters in a “clean state” (i.e., pristine state or containing very small amounts of soot and / or ash and / or other particulate matter) would be valuable for engine or vehicle manufacturers.

[0003] Therefore, alternative methods and apparatus are needed to evaluate or achieve the target filtration efficiency when the particulate filter is in a clean state. Summary of the Invention

[0004] One or more embodiments of this disclosure relate to a method for determining the filtration efficiency of a filter comprising a porous wall portion having a longitudinal axis extending from an inlet end to an outlet end, and an outer peripheral portion extending parallel to the longitudinal axis and surrounding the porous wall portion. The method includes: sealing the outer peripheral portion to prevent gas from flowing across the outermost surface of the outer peripheral portion; forcing an inlet flow of gas (e.g., air) into the inlet end of the filter at a set flow rate; introducing particles, such as smoke particles, into the inlet flow; and optically counting the number of particles entering and leaving the filter during a sampling event, for example using diffraction-based optical particle counters located upstream and downstream of the filter. Preferably, the airflow is a soot-free flow that does not load contaminants that need to be removed or burned off onto the cellular filter body. Therefore, the filter body remains substantially clean even after its filtration efficiency has been tested.

[0005] In some implementations, the particles are smoke particles.

[0006] In some implementations, the optical counting of the number of particles entering and leaving the filter during a sampling event is achieved using diffraction-based optical particle counters located upstream and downstream of the filter.

[0007] Other embodiments of this disclosure relate to the methods disclosed herein. Attached Figure Description

[0008] To gain a more detailed understanding of the foregoing features of this disclosure, a more specific description of the disclosure, which has been briefly outlined above, can be obtained by referring to embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings illustrate only typical embodiments of this disclosure and should not be construed as limiting its scope, as other equally effective embodiments are possible.

[0009] Figure 1 This is a schematic diagram of a laboratory FE system that can be used to measure filtration efficiency in a laboratory environment.

[0010] Figure 2A Three theoretical particle trapping mechanisms that can be combined to provide filtration efficiency are shown: interception, impaction, and diffusion.

[0011] Figure 2B The diagram schematically depicts filtration efficiency versus particle diameter and Figure 2A The relevant theoretical particle trapping mechanism.

[0012] Figure 3 An embodiment of the clean FE system disclosed herein is schematically depicted, showing a GPF ceramic honeycomb filter body used for testing.

[0013] Figure 4A A graph showing a representative particle size distribution used to measure the filtration efficiency of a GPF filter in a clean FE system is presented.

[0014] Figure 4B An exemplary preferred target upstream particle concentration and concentration range for allowing FE measurements are shown.

[0015] Figure 5 The correlation between smoke FE measurements and laboratory FE measurements is shown.

[0016] Figure 6A The Measurement System Analysis (MSA) results of the Smoke Cleaning FE System (Smoke FE System) are shown, which presents the raw data of a 4.055-inch diameter contour component, with 10 sections of each contour measured 3 times each by 2 operators at different FE levels.

[0017] Figure 6B The Measurement System Analysis (MSA) results of the Smoke Cleaning FE System (Smoke FE System) are shown, which presents the raw data of a 5.2-inch diameter profile component, with 10 sections of each profile at different FE levels, each measured 3 times by 2 operators.

[0018] Figure 7The low pooled standard deviation of 0.35% is shown for all profiles, operators, and FE levels performed using the apparatus disclosed herein and the methods disclosed herein.

[0019] Figure 8A The illustration schematically shows a cleaning FE device that does not have an airbag system but instead uses a conical section where the filter component is mounted and sealed against a soft rubber gasket.

[0020] Figure 8B The cleaning FE device using an airbag system is illustrated schematically.

[0021] Figure 9 A honeycomb structure is schematically shown.

[0022] Figure 10 A wall-flow particulate filter according to an embodiment disclosed and described herein is illustrated schematically.

[0023] Figure 11 Figure 8 shows a longitudinal cross-sectional view of the particulate filter.

[0024] Figure 12 The wall of a honeycomb with particle load is schematically shown. Detailed Implementation

[0025] Before describing several exemplary embodiments of this disclosure, it should be understood that this disclosure is not limited to the details of the construction or process steps set forth in the following description. This disclosure may have other embodiments and can be practiced or implemented in various ways.

[0026] This document discloses a system for measuring the filtration efficiency (FE) of particulate filters. In some embodiments, the system is cost-effective and / or substantially pollution-free, and / or capable of high-speed operation to enable, for example, FE measurements of large percentages, even up to 100%, of cellular filter bodies during manufacturing. In contrast to laboratory FE benchtop units (or “laboratory FE systems”), the system disclosed herein, sometimes referred to herein as a “clean FE benchtop test system” or “clean FE test apparatus” or “clean FE system”, may in some embodiments include alternating particle generation and / or particle measurement and / or data analysis from a laboratory FE system.

[0027] Figure 1This is a schematic diagram of a laboratory FE system for measuring filtration efficiency in a laboratory environment. Particles are generated by a CAST soot generator, and the required amount of soot is mixed with an airflow (primary air) via an injector (gun) or nozzle (gun), flows through a duct to the filter, and is collected (e.g., a Torit dust collector) and discharged to the emission reduction system. Any remaining unused soot generated can be guided to the dust collector via a bypass line (bypass). A micro-smoke sensor is used to measure the instantaneous total soot concentration at low concentration levels, exhibiting high sensitivity and excellent unbiased accuracy. The pressure drop (ΔP) across the filter under test, as well as the absolute pressure (Abs.P) just upstream of the filter, can be measured. An engine exhaust particulate matter (EEPS) sensor is used to measure particle size distribution and total concentration in real time to monitor filtration efficiency (“FE”) during the test cycle. Particle concentration and particle size distribution measurements are performed upstream and downstream of the cell. The filtration efficiency FE can be obtained from the measured concentration and Equation 1:

[0028] (1) μ e = n t / n u = (n u - n d ) / n u (1),

[0029] Where μ e =Air filtration efficiency, n t = The number of captured particles, n u = Upstream particles, and n d = Downstream particles.

[0030] Not restricted by any specific operational theory, such as Figure 2A and Figure 2B As shown. It is believed that, depending on particle size, three particle trapping mechanisms can combine to provide filtration efficiency: interception, impaction, and diffusion. For example, smaller particles can be trapped primarily through diffusion, larger particles can be trapped primarily through interception and impaction, while medium-sized particles can be trapped through a combination of diffusion and interception. Therefore, the initial filtration efficiency of a new or fresh ceramic honeycomb filter (such as a gasoline particulate filter (GPF)) may vary depending on the particle size. For example, both smaller and larger particles can be trapped, but lower filtration efficiency can be observed for particles with a diameter of approximately 200 nm.

[0031] Figure 3An embodiment of the clean FE system disclosed herein is schematically depicted, showing a GPF ceramic honeycomb filter body used for testing. The GPF component is shown loaded into a tight bladder seal embedded in a section of a circular duct connected to a blower. The blower pushes regulated air (or one or more other gases) through the duct to the GPF at a set flow rate. Once the flow has stabilized, a small amount of smoke from a reservoir is pushed into the duct using compressed air (or one or more other gases). Smoke particles mix with the airflow and pass through the GPF, which filters out a certain percentage of these particles, indicating the GPF's filtration efficiency. Diffraction-based optical particle counters are placed upstream and downstream of the GPF to count the number of smoke particles entering and leaving the GPF. The filtration efficiency of the GPF is calculated using Equation 1. The flow rate through the GPF is maintained at a constant rate using a blower and a temperature-compensated flow meter.

[0032] The reservoir can contain particles from a variety of sources, such as (burning) cigarettes, liquid atomizers, burning organic powders, etc. In some embodiments, for filters, such as gasoline particulate filters, the particles from the reservoir preferably have a particle size distribution in the range of 0.2 μm to 2.0 μm, more preferably with a peak value of 0.3 μm. Figure 4A A graph showing a representative particle size distribution for measuring the filtration efficiency of a GPF filter in a clean FE system is presented. The particles range from 0.2 μm to 2.0 μm, with a peak at 0.3 μm. In addition to the particle size distribution, the particle concentration provided is preferably optimized to maximize the signal-to-noise ratio of the particle counter without overloading it. Figure 4B Exemplary preferred target upstream particle concentrations and concentration ranges for allowing FE measurements are shown. In a preferred embodiment, the target upstream particle count is between 9,000 and 11,000, and in other preferred embodiments, between 9,500 and 10,500. Particle counters can operate accurately at relatively low concentrations compared to equipment used on laboratory FE benches (EEPS, CPC, etc.), and are therefore preferred. Particle counters are further preferred and can be very important in various embodiments for obtaining stable, consistent, and / or repeatable FE results during GPF measurements and even after multiple repeated tests. Furthermore, optically based particle counters are significantly cheaper (in some cases, orders of magnitude) than other measurement methods.

[0033] In the various embodiments disclosed herein, a system and method are provided for measuring the filtration efficiency (FE) of a particulate filter. FE is determined by measuring the difference between the number of particles introduced into the particulate filter and the number of particles leaving the particulate filter under defined airflow conditions.

[0034] Figure 3 A set of implementation schemes disclosed herein are shown. Figure 3 The system for performing FE measurements is shown, comprising three main components: (1) a flow delivery system with a particle filter support; (2) a particle generator and particle delivery system with metrological capabilities; and (3) a set of aerosol spectrometers for measuring particle count and particle size distribution.

[0035] In order to generate test conditions for stable, repeatable and accurate FE measurements, it is preferable to have control over each of the three components in the system.

[0036] In this set of embodiments, the flow delivery system comprises a sealed circular duct, but not limited to circular (e.g., adapted to an elliptical profile), with a centrifugal blower, which draws air from a room through a HEPA filter (99.97% FE for particles >0.3 μm) to remove contaminants from the room. The air exits the blower and is forced into the duct containing a particulate filter holder. The duct is sized to accommodate the largest particulate filter to be tested, plus some space for the particulate filter holder. The holder is a plate with perforations and an inflatable bladder, the inner diameter of which is slightly larger than the component. To load the particulate filter into the holder, the encased rubber ring is deflated, and the component is then loaded into the holder plate and seated on a retaining pin. The rubber ring is then inflated to seal against the outer diameter of the particulate filter and to center the particulate filter within the holder. The upper portion of the test section of the duct is then lowered to meet the lower portion of the duct below the filter, and a tight seal is formed, for example, using a gasket.

[0037] After the components have been loaded and sealed in the test section, the blower velocity is increased or boosted to the target velocity. Preferably, the velocity through the test chamber is stable and controlled within the temperature range of the gas flowing through the system. In one embodiment, the blower speed is controlled at 51 Nm using a Sierra Quadra-Therm 780i mass flow meter with temperature correction. 3 / hr+ / -0.1Nm 3 The correct flow rate is / hr, independent of gas temperature. Monitoring and controlling the gas temperature is preferred. In some implementations, temperature is not actively controlled, but measurement only begins when the temperature is between 18-40 degrees Celsius (not passable).

[0038] The next step of the process is to inject particles of appropriate size (as described in this invention) at an appropriate concentration into the flow stream upstream of the particle filter. Preferably, a minimum distance (e.g., about 5 tube diameters) separates the injection point and the first measurement point to allow the particles to be properly mixed into the flow stream; having such a separation distance or spacing avoids unexpected changes or fluctuations in concentration that could otherwise lead to erroneous measurements. In one embodiment, the particles are generated by burning cigarette smoke having a median particle size of 300 nm and such... Figure 4B The particle size distribution is shown. Particles can also be generated by or through other sources, such as the combustion of liquid atomizers or organic powders. In one embodiment, the particles used in the system are generated by burning a cigarette and drawing smoke into a reservoir using a smoke respirator. The smoke respirator draws air through the lit cigarette using a square wave suction mode with a suction period equal to 10. Particles flow into the reservoir, and a stirring fan keeps the particles carried in the air until they are pushed into the main chamber flow using a compressed air source and a mass flow controller. The upper limit of the mass flow controller helps ensure a constant total flow rate. When this limit is reached, a new suction from the cigarette is required. In the main test section before the particulate filter under test, particles are mixed into the airflow. The mass flow controller is used to regulate the amount of smoke pushed into the test section such that the total number of particles in the test chamber is 10,000 particles / second ± 500 particles / second. Particle concentration and size distribution are measured using an upstream airborne particle counter (Lighthouse Worldwide Solutions Model Handheld 2016). In addition to total particle concentration, concentration variability, and concentration stability, particle size distribution is also controlled (selected). In this embodiment of the clean FE system (here, a smoke FE system), the particle count in each particle size cell is set to be within 10% of its defined setpoint, between 0.2 μm and 2 μm (see [link to documentation]). Figure 4B ).

[0039] The smoke FE blower and smoke delivery system were operated until the smoke concentration and particle size distribution reached stable values ​​within acceptable ranges. The system then recorded 20-second data from upstream and downstream particle counters. The system then calculated a 20-second average using only particles with a 0.3 μm box size to produce the upstream and downstream particle counts for Equation 1. Experimentally, it was determined that using the total particle count from all particle sizes (or some smaller size bands) produces high variability in FE measurements. This variability is attributed to the sensitivity of particulate filter efficiency to the size of the source particles generated during puffing. To eliminate this effect, the filtration efficiency was calculated using only the 20-second average particle count from 0.3 μm smoke particles (0.3 μm box size). In addition to the 20-second average, the RMS and slope were also measured. The RMS can be used to clarify or identify measurements where particle concentration is particularly noisy, as is often seen after fresh puffing. The slope was measured to ensure that the particle concentration remained constant (or substantially constant) during the 20-second measurement.

[0040] In some embodiments, the pressure differential caused by the flow through the filter components can also be measured by the system after the FE measurement is completed. In one embodiment, three ports are provided to measure the pressure before (upstream) and after (downstream) the component. The measured pressures are physically averaged and the data is recorded using a differential pressure gauge. The system can be configured to shut off the blower after the pressure measurement is completed; the test chamber can then be opened, allowing the component part-holding bladder to deflate and the particulate filter to be removed. The next filter can then be loaded and the process repeated. In some embodiments, the cleaning FE system can be configured to process components at a rate of approximately 1 minute and 40 seconds per component from loading to unloading. In some embodiments, the total measurement time can be further reduced, for example, by running the blower between measurements (without shutting it off), and / or by replacing the smoke generator with a fully automated system (e.g., a liquid aerosol generator) that can eliminate the ignition or combustion of organic matter such as cigarette smoke.

[0041] To test the clean FE system's capabilities, a measurement system analysis (MSA) with bias and linearity studies was conducted to assess variability, as well as a correlation study with the laboratory FE system. The MSA used to test measurement repeatability consisted of 10 circular particulate filters, each with two component diameters, measured three times each by two operators. All filters were constructed from a porous cordierite Corning GC 1.0 gasoline particulate filter material composition, with 300 cells per square inch (CPSI) and a wall thickness of 0.008” (8 mils) per channel. Figure 6AThe Measurement System Analysis (MSA) results of the Smoke Cleaning FE System (Smoke FE System) are shown, which presents the raw data for a 4.055-inch diameter profile component, where each profile has 10 parts at various different FE levels, each measured 3 times by 2 operators. Figure 6B The Measurement System Analysis (MSA) results for the smoke cleaning FE system (Smoke FE System) are shown, illustrating the raw data for a 5.2-inch diameter profile component, where each profile has 10 segments at different FE levels, each measured 3 times by 2 operators. Therefore, each profile has 10 segments at different FE levels, each measured 3 times by 2 operators. Figure 6A and 6B As shown, the raw data indicates a close distribution of FE measurements across the operator, component diameter, and FE level. Figure 7 The analysis results showed a low pooled standard deviation of 0.35% across all profiles, operators, and FE levels. To evaluate these components, the MSA results were within acceptable levels when averaged across all component profiles, operators, and FE levels. GRR, or Gage R&R, or Gauge Repeatability and Reproducibility, is a method for evaluating the amount of variation in measurement data of a measurement system as part of an MSA. A comparison was made between a clean FE system using smoke particles (“Smoke FE System”) and a standard laboratory FE system by performing deviation and linearity studies, with results as follows: Figure 5 As shown, the correlation coefficient between the smoke and laboratory FE systems is 0.97, indicating a strong correlation. An offset was observed between the systems, which is attributed to particle size and the filtration sensitivity of particle filters to particles of different sizes, as shown in Figure 2, since the average diameter of laboratory FE soot particles is approximately 75 nm, while the size of smoke FE particles is approximately 300 nm. The offset between the laboratory FE and smoke FE systems can be explained using a correction factor if needed. Furthermore, the laboratory FE workbench was operated at a lower flow rate and used a different particle measurement system. Other data also show the correlation between the smoke FE system and Cambustion, a commercial FE measurement system utilizing soot particles. One advantage of the smoke FE system disclosed herein is that, due to the ability to account for particle size, the measured FE can be lower and can be better scaled; thus, higher resolution can be achieved, and small differences in FE can be identified.

[0042] Figure 8A The cleaning FE device is schematically shown, which does not have an airbag system but uses a conical section where the filter component is mounted and sealed against a soft rubber gasket.

[0043] Figure 8BThe cleaning FE device using an airbag system is illustrated schematically.

[0044] In one set of embodiments, this document discloses a method for determining the filtration efficiency of a filter comprising a porous wall portion having a longitudinal axis extending from an inlet end to an outlet end, and an outer peripheral portion extending parallel to the longitudinal axis and surrounding the porous wall portion. The method includes: sealing the outer peripheral portion to prevent gas from flowing across the outermost surface of the outer peripheral portion; forcing an inlet flow consisting of gas (air) into the inlet end of the filter at a set flow rate; introducing particles into the inlet flow; and optically counting the number of particles entering and leaving the filter during a sampling event. In some embodiments, the particles are smoke particles. In some embodiments, the optical counting of the number of particles entering and leaving the filter during a sampling event is achieved using diffraction-based optical particle counters located upstream and downstream of the filter.

[0045] In some implementations, the particles are selected to have a particle size distribution that maximizes the signal-to-noise ratio of the particle counter.

[0046] In some implementations, the particles are selected to have a particle size distribution that maximizes the signal-to-noise ratio of the particle counter without overloading the particle counter.

[0047] In some embodiments, the particles are generated by burning a cigarette to produce cigarette smoke particles. In some embodiments, the cigarette smoke particles are placed in a reservoir. In some embodiments, a smoke respirator is used to place the cigarette smoke particles in the reservoir.

[0048] In some embodiments, the sampling event continues until more than 5,000 particles are counted upstream of the filter. In some embodiments, the sampling event continues until more than 8,000 particles are counted upstream of the filter. In some embodiments, the sampling event continues until 9,000 or more particles are counted upstream of the filter. In some embodiments, the sampling event continues until 15,000 particles are counted upstream of the filter. In some embodiments, the sampling event continues until 12,000 particles are counted upstream of the filter. In some embodiments, the sampling event continues until 9,000 to 11,000 particles are counted upstream of the filter. In some embodiments, the sampling event continues until 9,500 to 10,050 particles are counted upstream of the filter.

[0049] In some implementations, the sampling event lasts 10 to 30 seconds. In some implementations, the sampling event lasts 15 to 25 seconds. In some implementations, the sampling event lasts 20 seconds.

[0050] In some embodiments, the particle size distribution of the particles introduced into the inlet stream ranges from 0.2 μm to 2.0 μm, with a median particle size of 0.3 μm. In some embodiments, the particle size distribution of the particles introduced into the inlet stream ranges from 0.2 μm to 2.0 μm, with a peak size between 0.2 and 0.4 μm. In some embodiments, the particles are present upstream of the filter at a target upstream particle count of between 9000 and 11000, and in other preferred embodiments, between 9500 and 10500.

[0051] In some implementations, the gas flow rate remains constant with a volumetric velocity variation not exceeding 10% during the sampling event. In some implementations, the gas flow rate is maintained by a temperature-compensated flow meter. In some implementations, the gas flow rate is maintained at greater than 35 Nm. 3 / hr, and less than 60Nm 3 / hr. In some implementations, the airflow is maintained at 51 Nm. 3 / hr+ / -0.1Nm 3 / hr, independent of gas temperature.

[0052] In some embodiments, the airflow is between 15 and 50 degrees Celsius. In some embodiments, the airflow is between 18 and 40 degrees Celsius. In some embodiments, the airflow is temperature-controlled. In some embodiments, the airflow is between 15 and 50 degrees Celsius.

[0053] In some embodiments, the particles are selected from cigarette smoke particles, atomized particles, liquid particles, nebulized particles, burned organic powders, and combinations thereof.

[0054] In some embodiments, the gas inlet stream is filtered to remove contaminants; in some of these embodiments, the gas inlet stream is filtered through a HEPA filter to remove contaminants; in some of these embodiments, the gas inlet stream is filtered through a HEPA filter with 99.97% FE for particles larger than 0.3 μm to remove contaminants.

[0055] In some embodiments, the particles are introduced further upstream than where the upstream optical particle count occurs. In some embodiments, the gas inlet flow is directed through a hollow tube with an effective diameter Deff, and the particles are introduced at a distance of 5 Deff upstream of where the upstream particle count occurs.

[0056] In some implementation schemes, the filtration efficiency of the filter is determined by the following formula:

[0057] μe = (n u - n d ) / n u (1),

[0058] Where μ e = Filtration efficiency, n u = Upstream particles, and n d = Downstream particles.

[0059] In some implementation schemes, the filtration efficiency of the filter is determined by the following formula:

[0060] μ e = (n u - n d ) / n u (1),

[0061] Where μ e = Filtration efficiency, n u = 0.3μm sampling binary upstream particles, and n d = Downstream particles in the 0.3μm sampling bin.

[0062] In some embodiments, the porous wall portion comprises a wall having a bulk porosity of 40 to 75%, which is measured by mercury intrusion porosimetry.

[0063] In some embodiments, the porous wall portion comprises a wall made of cordierite, aluminum titanate, silicon carbide, mullite, spinel, silicon dioxide, aluminum oxide, silicon nitride, and combinations thereof.

[0064] In some implementations, the porous wall portion comprises a wall arranged in a honeycomb structure with 100 to 900 units per square inch.

[0065] In some implementations, the filter has an ash load of less than 0.1 g / cubic inch filter volume before and at the end of the sampling event.

[0066] In some implementations, the filter has an ash load of less than 0.1 g / cubic inch filter volume before and at the end of the sampling event.

[0067] Now for reference Figure 9The diagram illustrates a honeycomb structure 100 according to one or more embodiments shown and described in accordance with the present invention. In one embodiment, the honeycomb structure 100 may include a plurality of walls 115 defining a plurality of internal channels 110. The plurality of internal channels 110 and the intersecting channel walls 115 extend between a first end 105 (which may be an inlet end) and a second end 135 (which may be an outlet end) of the plugged honeycomb structure. The honeycomb structure may have one or more channels plugged in one or both of the first end 105 and the second end 135. The pattern of the plugged channels in the honeycomb structure is not limited. In some embodiments, the pattern of plugged and unplugged channels at one end of the plugged honeycomb structure may be, for example, a checkerboard pattern, wherein alternating channels at one end of the plugged honeycomb structure are plugged. In some embodiments, plugged channels at one end of the plugged honeycomb structure have corresponding unplugged channels at the other end, and unplugged channels at one end of the plugged honeycomb structure have corresponding plugged channels at the other end.

[0068] In one or more embodiments, the honeycomb structure of the plug may be composed of cordierite, aluminum titanate, enstatite, mullite, forsterite, corundum (SiC), spinel, sapphire, or periclase, or combinations thereof. Typically, cordierite has the formula Mg2Al4Si5O. 18 The composition. In some embodiments, the pore size, porosity, and pore size distribution of the ceramic material are obtained in a controlled manner, for example, by changing the particle size of the ceramic raw material. Furthermore, a pore-forming agent may be included in the ceramic batch used to form the honeycomb structure of the plug.

[0069] In some embodiments, the walls of the plug's honeycomb may have an average thickness from greater than or equal to 25 μm to less than or equal to 250 μm, for example from greater than or equal to 45 μm to less than or equal to 230 μm, greater than or equal to 65 μm to less than or equal to 210 μm, greater than or equal to 65 μm to less than or equal to 190 μm, or greater than or equal to 85 μm to less than or equal to 170 μm. The walls of the plug's honeycomb can be described as having a base portion consisting of a body portion (also referred to as the body in this invention) and a surface portion (also referred to as the surface in this invention). The surface portion of the wall extends from the surface of the wall of the plug's honeycomb toward the body portion of the plug's honeycomb. The surface portion can extend from 0 (zero) to a depth of about 10 μm into the base portion of the wall of the plug's honeycomb. In some embodiments, the surface portion can extend to about 5 μm, about 7 μm, or about 9 μm into the base portion of the wall (i.e., a depth of 0 (zero)). The body portion of the plug's honeycomb constitutes the thickness of the wall minus the surface portion. Therefore, the main body of the plug's honeycomb structure can be determined by the following equation:

[0070] t 总 -2t 表面

[0071] Where t 总 It is the total thickness of the wall, and t 表面 It is the thickness of the wall surface.

[0072] In one or more embodiments, the body of the plug's honeycomb (before the application of any filter material) has a median pore size ranging from greater than or equal to 7 μm to less than or equal to 25 μm, for example, from greater than or equal to 12 μm to less than or equal to 22 μm, or from greater than or equal to 12 μm to less than or equal to 18 μm. For example, in some embodiments, the body of the plug's honeycomb may have a median pore size of about 10 μm, about 11 μm, about 12 μm, about 13 μm, about 14 μm, about 15 μm, about 16 μm, about 17 μm, about 18 μm, about 19 μm, or about 20 μm. Typically, the pore size of any given material exists in a statistical distribution. Therefore, the term "median pore size" or "d50" (before the application of any filter material) refers to a length measurement based on the statistical distribution of all pores, with 50% of the pores having a pore size above it and the remaining 50% having a pore size below it. Pores in the ceramic body can be created by at least one of the following: (1) the particle size and particle size distribution of the inorganic batch; (2) the furnace / heat treatment firing time and temperature scheme; (3) the furnace atmosphere (e.g., low or high oxygen and / or water content); and (4) pore-forming agents, such as polymers and polymer particles, starch, wood flour, hollow inorganic particles and / or graphite / carbon particles.

[0073] In a specific embodiment, the median pore size (d50) of the plugged honeycomb body (before the application of any filter material) is in the range of approximately 16 μm, for example, 13-14 μm, from 10 μm to about 16 μm, and d10 refers to a length measurement based on the statistical distribution of all pores, with 90% of the pores above and the remaining 10% below, d10 is approximately 7 μm. In a specific embodiment, d90 refers to a length measurement based on the statistical distribution of all pores, with 10% of the pores of the plugged honeycomb body (before the application of any filter material) above and the remaining 90% below, d90 is approximately 30 μm. In a specific embodiment, the median diameter (D50) of the secondary particles or agglomerates is approximately 2 μm. In specific implementations, it has been determined that excellent filtration efficiency and low pressure drop results can be achieved when the median aggregate size D50 and the median wall pore size d50 of the bulk honeycomb are such that the ratio of the median aggregate size D50 to the median wall pore size d50 of the bulk honeycomb is in the range of 5:1 to 16:1. In more specific implementations, excellent filtration efficiency and low pressure drop results are provided when the ratio of the median aggregate size D50 to the median wall pore size d50 of the bulk honeycomb (before the application of any filter material) is in the range of 6:1 to 16:1, 7:1 to 16:1, 8:1 to 16:1, 9:1 to 16:1, 10:1 to 16:1, 11:1 to 16:1, or 12:1 to 6:1.

[0074] In some embodiments, such as those measured by mercury porosimetry, the bulk porosity of the plugged honeycomb may have a bulk porosity (excluding coatings) greater than or equal to 50% to less than or equal to 75%. Other methods for measuring porosity include scanning electron microscopy (SEM) and X-ray tomography, both of which are particularly valuable for measuring surface porosity and bulk porosity independently of each other. In one or more embodiments, the bulk porosity of the plugged honeycomb may be, for example, in the range of about 50% to about 75%, in the range of about 50% to about 70%, in the range of about 50% to about 65%, in the range of about 50% to about 60%, in the range of about 50% to about 58%, in the range of about 50% to about 56%, or in the range of about 50% to about 54%.

[0075] In one or more embodiments, the surface portion of the plug's honeycomb structure has a median surface pore size greater than or equal to 7 μm and less than or equal to 20 μm, for example, greater than or equal to 8 μm and less than or equal to 15 μm, or greater than or equal to 10 μm and less than or equal to 14 μm. For example, in some embodiments, the surface of the plug's honeycomb structure may have a median surface pore size of about 8 μm, about 9 μm, about 10 μm, about 11 μm, about 12 μm, about 13 μm, about 14 μm, or about 15 μm.

[0076] In some embodiments, prior to the application of filter material deposits, the surface of the plug's honeycomb may have a surface porosity of greater than or equal to 35% and less than or equal to 75%, as measured by mercury intrusion porosimetry, SEM, or X-ray tomography. In one or more embodiments, for example, the surface porosity of the plug's honeycomb may be less than 65%, such as less than 60%, less than 55%, less than 50%, less than 48%, less than 46%, less than 44%, less than 42%, less than 40%, less than 48%, or less than 36%.

[0077] Now for reference Figure 10 and Figure 11 The diagram schematically depicts a honeycomb structure in the form of a particulate filter 200. The particulate filter 200 can serve as a wall-flow filter for filtering particulate matter from an exhaust gas stream 250, such as the exhaust gas stream from a gasoline engine; in this case, the particulate filter 200 is a gasoline particulate filter. The particulate filter 200 typically comprises a honeycomb structure having a plurality of channels 201 or cells extending between an inlet end 202 and an outlet end 204, defining a total length La (e.g., ...). Figure 11 (As shown). The channels 201 of the particulate filter 200 are formed by and at least partially defined by a plurality of phase communication channel walls 206 extending from the inlet end 202 to the outlet end 204. The particulate filter 200 may also include a surface layer 205 surrounding the plurality of channels 201. The surface layer 205 may be extruded during the formation of the channel walls 206 or formed as a post-applied surface layer in subsequent processing, for example by applying a surface adhesive to the outer periphery of the channels.

[0078] Figure 11 It shows Figure 10 The axial section of the particulate filter 200. In some embodiments, certain channels are designated as inlet channels 208, while certain other channels are designated as outlet channels 210. In some embodiments of the particulate filter 200, at least the first set of channels can be plugged with plugs 212. Typically, the plugs 212 are arranged near the ends of the channels 201 (i.e., the inlet or outlet end). The plugs are typically arranged in a predefined pattern, such as... Figure 10 The chessboard pattern shown has plugs inserted at the ends every other channel. Figure 10 As shown, inlet channel 208 can be plugged at or near outlet end 204, and outlet channel 210 can be plugged at or near inlet end 202 on a channel that does not correspond to the inlet channel. Therefore, each unit can be plugged only at or near one end of the particulate filter.

[0079] although Figure 10A checkerboard-patterned plug pattern is generally described, but it should be understood that alternative plug patterns can be used in porous ceramic honeycomb articles. In the embodiments described herein, the particulate filter 200 can be formed with a channel density of up to about 600 channels per square inch (cpsi). For example, in some embodiments, the particulate filter 100 may have a channel density in the range of about 100 cpsi to about 600 cpsi. In some other embodiments, the particulate filter 100 may have a channel density in the range of about 100 cpsi to about 400 cpsi or even about 200 cpsi to about 300 cpsi.

[0080] In the embodiments described herein, the thickness of the channel wall 206 of the particulate filter 200 may be greater than about 4 mils (101.6 μm). For example, in some embodiments, the thickness of the channel wall 206 may range from about 4 mils to about 30 mils (762 μm). In some other embodiments, the thickness of the channel wall 206 may range from about 7 mils (177.8 μm) to about 20 mils (508 μm).

[0081] In some embodiments of the particulate filter 200 described herein, the channel wall 206 of the particulate filter 200 may have a bare open porosity (i.e., the porosity before any coating is applied to the cell structure of the plug) %P. In some embodiments, the bare open porosity of the channel wall 206 may be 40% ≤ %P ≤ 75%. In other embodiments, the bare open porosity of the channel wall 206 may be 45% ≤ %P ≤ 75%, 50% ≤ %P ≤ 75%, 55% ≤ %P ≤ 75%, 60% ≤ %P ≤ 75%, 45% ≤ %P ≤ 70%, 50% ≤ %P ≤ 70%, 55% ≤ %P ≤ 70%, or 60% ≤ %P ≤ 70%.

[0082] Furthermore, in some embodiments, the channel wall 206 of the particulate filter 200 is formed such that the pores in the channel wall 206 have a median pore size of ≤30 μm before any coating is applied (i.e., bare). For example, in some embodiments, the median pore size may be ≥8 μm and less than or ≤30 μm. In other embodiments, the median pore size may be ≥10 μm and less than or ≤30 μm. In other embodiments, the median pore size may be ≥10 μm and less than or ≤25 μm. In some embodiments, particulate filters with a median pore size greater than about 30 μm have reduced filtration efficiency, while particulate filters with a median pore size less than about 8 μm may have difficulty permeating the pores with a catalyst-containing washcoat. Therefore, in some embodiments, it is desirable to maintain the median pore size of the channel wall in the range of about 8 μm to about 30 μm, for example, in the range of 10 μm to about 20 μm.

[0083] In one or more embodiments described herein, the honeycomb structure of the plugs of the particulate filter 200 is formed of a metallic or ceramic material, such as cordierite, silicon carbide, alumina, aluminum titanate, or any other ceramic material suitable for high-temperature particulate filtration applications. For example, the particulate filter 200 can be formed from cordierite by mixing a batch of ceramic precursor materials, which may include constituent materials suitable for manufacturing ceramic articles comprising primarily cordierite crystalline phases. Typically, constituent materials suitable for cordierite formation include a combination of inorganic components, including talc, silica-forming sources, and alumina-forming sources. The batch composition may also additionally contain clay, such as kaolin. The cordierite precursor batch composition may also contain organic components, such as organic pore-forming agents, which are added to the batch mixture to obtain the desired pore size distribution. For example, the batch composition may contain starch suitable for use as a pore-forming agent and / or other processing aid. Alternatively, the constituent materials may contain one or more cordierite powders suitable for forming a sintered cordierite honeycomb structure during firing, along with an organic pore-forming agent material.

[0084] The batch composition may additionally contain one or more processing aids, such as binders and liquid mediators, such as water or suitable solvents. Adding processing aids to the batch mixture plasticizes the mixture and generally improves processing, reduces drying time, reduces cracking during firing, and / or helps produce desired properties in the plugged celluloid. For example, the binder may include an organic binder. Suitable organic binders include water-soluble cellulose ether binders, such as methylcellulose, hydroxypropyl methylcellulose, methylcellulose derivatives, hydroxyethyl acrylate, polyvinyl alcohol, and / or any combination thereof. Incorporating organic binders into the plasticized batch composition allows for easy extrusion of the plasticized batch composition. In some embodiments, the batch composition may include one or more optional molding or processing aids, such as lubricants that facilitate the extrusion of the plasticized batch mixture. Exemplary lubricants may include tall oil, sodium stearate, or other suitable lubricants.

[0085] After mixing the batch of ceramic precursor material with suitable processing aids, the batch of ceramic precursor material is extruded and dried to form a green honeycomb, the green honeycomb including an inlet end and an outlet end, with multiple channel walls extending between the inlet end and the outlet end. The green honeycomb is then fired according to a firing scheme suitable for producing a fired honeycomb. At least a first set of channels in the fired honeycomb can then be plugged with a ceramic plugging composition in a predetermined plugging pattern, and the honeycomb is dried and / or heated to secure the plugs in the channels.

[0086] In various implementations, the plug's honeycomb structure is configured to filter particulate matter from an airflow, such as exhaust gas from a gasoline engine. Therefore, considering these filtration requirements of the plugged honeycomb structure, the median pore size, porosity, geometry, and other design aspects of the plug's honeycomb structure's body and surface are selected. For example, as... Figure 12 As shown in the implementation scheme, the plug's honeycomb body 300 (which can be as follows) Figure 10 and Figure 11 The wall 310 of the particulate filter (as shown) is provided with a filter material deposit 320, which in some embodiments is sintered by heat treatment or otherwise bonded. The filter material deposit 320 comprises particles 325 deposited on the wall 310 of the plugged cell 300 and helps prevent particulate matter, such as soot and / or ash, from leaving the plugged cell with the airflow 330, and helps prevent particulate matter from clogging the base portion of the wall 310 of the plugged cell 300. In this way, and according to embodiments, the filter material deposit 320 can serve as the primary filter element, while the base portion of the plugged cell can be configured to further minimize pressure drop, for example, compared to a cell without such a filter material deposit. The filter material deposit is delivered using the apparatus and deposition method disclosed herein.

[0087] Compared to the thickness of the base portion of the wall of the plug's honeycomb, the material on the wall of the plug's honeycomb (which may be an inorganic layer in some portions or embodiments) is very thin. The material on the plug's honeycomb (which may be an inorganic layer) can be formed by methods that allow deposited material to be applied to the wall surface of the plug's honeycomb in a very thin coating or in some portions as a layer. In one embodiment, the average thickness of the material, which may be the deposition region or the inorganic layer, on the base portion of the wall of the plug's honeycomb structure is greater than or equal to 0.5 μm and less than or equal to 50 μm, or greater than or equal to 0.5 μm and less than or equal to 45 μm, greater than or equal to 0.5 μm and less than or equal to 40 μm, or greater than or equal to 0.5 μm and less than or equal to 35 μm, or greater than or equal to 0.5 μm and less than or equal to 30 μm, greater than or equal to 0.5 μm and less than or equal to 25 μm, or greater than or equal to 0.5 μm and less than or equal to 20 μm, or greater than or equal to 0.5 μm and less than or equal to 15 μm, or greater than or equal to 0.5 μm and less than or equal to 10 μm. In one or more embodiments, the inorganic material includes alumina.

[0088] The system and method disclosed in this invention thus provide a fast and simple way to measure FE, which is significantly less expensive than commercial systems and standards, while providing very accurate and precise measurements.

[0089] Throughout this specification, references to "an embodiment," "certain embodiments," "one or more embodiments," or "implementation" mean that a particular feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this disclosure. Therefore, phrases such as "in one or more embodiments," "in some embodiments," "in one embodiment," or "in an embodiment" appearing throughout this specification do not necessarily refer to the same embodiment disclosed herein. Furthermore, that particular feature, structure, material, or characteristic may be combined in any suitable manner in one or more embodiments.

[0090] Although the present invention has been described in conjunction with specific embodiments, those skilled in the art will understand that the described embodiments are merely illustrative of the principles and applications of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the methods and apparatus disclosed herein without departing from the spirit and scope of the invention. Therefore, the present invention can include modifications and variations within the scope of the appended claims and their equivalents.

Claims

1. A method for determining the filtration efficiency of a ceramic filter composed of a honeycomb structure, the ceramic filter comprising a plurality of intersecting porous walls forming a plurality of channels extending from an inlet end to an outlet end of the honeycomb structure, a longitudinal axis extending from the inlet end to the outlet end, at least some inlet channels inserted at or near the outlet end, and at least some outlet channels inserted at or near the inlet end, and an outer peripheral portion extending parallel to the longitudinal axis and surrounding the plurality of porous walls, the method comprising: The honeycomb structure is positioned on a support plate disposed in the pipe; The outer peripheral portion is sealed to prevent gas from flowing across the outermost surface of the outer peripheral portion, the seal comprising inflating an inflatable bladder surrounding the outer peripheral portion; The inlet flow consisting of gas is forced to flow into the inlet end of the filter at a set flow rate; The particles are introduced into the inlet stream, the particles including at least one of cigarette smoke particles, atomized particles, liquid particles, spray particles or burned organic powder, the particle size distribution range being 0.2 µm to 2.0 µm, and the peak particle size being 0.3 µm; Optical counting of the number of particles entering and leaving the filter during a sampling event; as well as The gas is filtered upstream of the inlet flow to remove contaminants from the gas.

2. The method of claim 1, wherein the particles introduced into the inlet stream are smoke particles.

3. The method of claim 1, wherein the optical count of the number of particles entering and leaving the filter during the sampling event is performed using diffraction-based optical particle counters located upstream and downstream of the filter.

4. The method of claim 1, wherein the particle selection is a particle size distribution that maximizes the signal-to-noise ratio of the particle counter without overloading the particle counter.

5. The method of claim 1, further comprising generating particles by burning cigarette smoke particles.

6. The method of claim 1, wherein the sampling event continues until at least 5,000 particles are counted upstream of the filter.

7. The method of claim 1, wherein the sampling event continues until at least 8,000 particles are counted upstream of the filter.

8. The method of claim 1, wherein the sampling event continues until at least 9,000 particles are counted upstream of the filter.

9. The method of claim 1, wherein the sampling event continues until at least 15,000 particles are counted upstream of the filter.

10. The method of claim 1, wherein the sampling event continues until at least 12,000 particles are counted upstream of the filter.

11. The method of claim 1, wherein the sampling event continues until 9,000 to 11,000 particles are counted upstream of the filter.

12. The method of claim 1, wherein the sampling event lasts from 10 seconds to 30 seconds.

13. The method of claim 1, wherein the sampling event lasts for 15 to 25 seconds.

14. The method of claim 1, wherein the expansion centers the honeycomb on the support plate.

15. The method of claim 1, wherein the particles are present upstream of the filter at a target upstream particle count of 9,000 to 11,000.

16. The method of claim 1, wherein the inlet flow maintains a volumetric flow rate that varies by no more than 10% during the sampling event.

17. The method of claim 16, wherein the volumetric flow rate of the inlet flow is maintained by a temperature-compensated flow meter.

18. The method of claim 17, wherein the inlet flow is maintained at greater than 35 Nm. 3 / hr, and less than 60Nm 3 / hr.

19. The method of claim 17, wherein the inlet flow is maintained at 51 Nm. 3 / hr + / - 0.1 Nm 3 / hr, regardless of the temperature of the gas.

20. The method of claim 1, wherein the temperature of the gas is between 15 degrees Celsius and 50 degrees Celsius.

21. The method of claim 1, wherein the temperature of the gas is between 18 degrees Celsius and 40 degrees Celsius.

22. The method of claim 1, wherein the gas is temperature controlled.

23. The method of claim 1, wherein the gas is filtered through a HEPA filter to remove contaminants.

24. The method of claim 23, wherein the HEPA filter has a filtration efficiency of 99.97% for particles larger than 0.3 μm.

25. The method of claim 1, wherein the particle is introduced upstream of the location where the upstream optical particle counting occurs.

26. The method of claim 25, wherein the inlet flow of the gas is directed through a hollow tube having an effective diameter Deff, and the particles are introduced at a distance of 5 Deff upstream of where an upstream particle count occurs.

27. The method of claim 1, wherein the filtration efficiency of the filter is determined by the following formula: μ e = (n u - n d ) / n u , Where μ e = Filtration efficiency, n u =Upstream particles, and n d =Downstream particles.

28. The method of claim 1, wherein the filtration efficiency of the filter is determined by the following formula: μ e = (n u - n d ) / n u , Where μ e = Filtration efficiency, n u = 0.3 µm sampling binary upstream particles, and n d = Downstream particles in a 0.3 µm sampling bin.

29. The method of claim 1, wherein the plurality of intersecting porous walls comprises porous walls having a bulk porosity of 40% to 75%, the bulk porosity being measured by mercury intrusion porosimetry.

30. The method of claim 1, wherein the plurality of intersecting porous walls comprises at least one of cordierite, aluminum titanate, silicon carbide, mullite, spinel, silicon dioxide, aluminum oxide, silicon nitride, or a combination thereof.

31. The method of claim 1, wherein the cell has 100 cells per square inch to 900 cells per square inch.

32. The method of claim 1, wherein the filter has an ash load of less than 6100 g / m³ (0.1 g / m³ inch) of filter volume before and at the end of the sampling event.

33. The method of claim 1, wherein the filter has an ash load of less than 6100 g / m³ (0.1 g / m³ inch) of filter volume before and at the end of the sampling event.

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