Evaluation of electrostatic screen battery for emissions control (ESBEC) with diesel emissions.
We recently developed a novel diesel emissions control device, Electrostatic Screen Battery for Emissions Control (ESBEC), where diesel exhaust particles are collected onto metal screens using electrostatic principle. This paper focuses on further development of this technology: design and integration of a particle charger and testing of ESBEC with diesel exhaust. Two units - 0.038 and 0.152 m (1.5 and 6 inches) in diameter - were fabricated using 3D printing. Both units feature cylinder-shaped housing integrating the electrical charger and up to seven pairs of metal screens, which collect airborne particles. In the small-scale version, particles are charged by ions emitted from a carbon fiber brush, while in the large-scale version, this is done by using two tungsten wires traversing the cross-section of ESBEC in a crisscross pattern. Small-scale version showed average collection efficiency of 80% over a wide range of diesel exhaust mass concentrations (5 to 400 mg/[m.sup.3]) and 1.5 m/s diesel exhaust face velocity. When ESBEC was tested continuously for 6 hours with diesel exhaust concentration of 300-400 mg/[m.sup.3], it maintained collection efficiency of >95%. The pressure drop across ESBEC during those six hours increased only minimally. In the next step, the large-scale version was challenged with diesel exhaust of 200 mg/[m.sup.3] concentration. ESBEC removed 71-99% of exhaust particle mass entering the collector at different temperatures (40-77 [degrees]C). In the near future, a full version of ESBEC will be fabricated from a heat-resistant material, and its performance will be compared with a conventional diesel particulate filter.
CITATION: Han, T, Zhen, H., and Mainelis, G., "Evaluation of Electrostatic Screen Battery for Emissions Control (ESBEC) with Diesel Emissions," SAE Int. J. Engines 9(4):2016, doi: 10.4271/2016-01-9047.
Diesel particulate filters (DPF) have been developed and implemented as a viable option to control diesel particulate matter (DPM) emissions; it is one of the options to retrofit existing diesel engines to control DPM emissions [1, 2, 3, 4]. However, the cost of retrofitting ranges from $2,500 to $4,300 per engine (US EPA, 2006) . In addition, the reduction in particle mass concentrations by current DPFs is not consistently accompanied by decreases in the number concentration of ultrafine particles (<100 nm in diameter) [6, 7]. During the operation of a DPF, particles accumulate inside of it and cause an increased resistance to exhaust flow (create backpressure) . Increased backpressure reduces fuel economy and engine performance, thus creating a need to regenerate the DPF by burning off the collected particles [9, 10]. However, in all traditional DPFs, regeneration creates secondary aerosol emission, especially in the 10-30 nm particle size range  which contributes to air pollution [12, 13]. There have been attempts to solve these issues by using different DPM collection methods, such as the application of electrostatic precipitation either by itself or in combination with traditional DPFs [14, 15, 16, 17]. However, the presented designs do not offer a viable alternative to existing DPFs and are not commercially available.
In our earlier publication, we presented a novel electrostatics-based DPM collector concept , where exhaust particles are electrically charged and then captured onto a series of metal screen pairs by the action of electrostatic forces. This design incorporates various elements from our earlier research: aerosol deposition on screens  combined with the development of electrostatic samplers [20, 21, 22, 23]. In our initial development of the collector , the incoming particles were electrically charged using a commercially available unipolar car ionizer (AS 150, Wein Products, Inc.). While this charger allowed testing a proof of concept of the collector, it quickly became obvious that it would not be effective when challenged with actual diesel exhaust. Thus, the design of a new particle charger and its integration with the collector was one of the goals of this project.
The developed prototypes Electrostatic Screen Battery for Emissions Control (ESBEC) consist of two main parts: an ionizer for field-induced charging of incoming diesel exhaust particles and a series of metal screen (i.e., mesh) pairs to which a voltage differential is applied to collect the charged particles. This manuscript focuses on the testing and performance of ESBEC prototypes when they are challenged with actual diesel emissions. The prototypes were tested as a function of charging and collection voltages (8-16 kV), diesel exhaust mass concentration (4-400 mg/[m.sup.3]), exhaust temperature (18-102 [degrees]C), diesel exhaust face velocity (0.36-2.1 m/s), and sampling time (3 min to 7 hours). ESBEC's performance was determined in terms of particle collection efficiency and pressure drop across the collector.
MATERIALS AND METHODS
Design of the Electrostatic Screen Battery for Emission Control (ESBEC)
Figure 1 shows the schematic diagram and pictures of several ESBEC prototypes. Each is comprised of an electrical charger and a collection section containing multiple pairs of metal mesh screens in series (i.e., a battery of screens) [18, 24]. One screen in each pair is supplied with a high voltage while the other is grounded, thus producing an electrostatic field across the screens. Overall, three different ESBEC models were produced and tested, depending on the objective of a test.
Model 1: A Small-Scale ESBEC Model (0.038 m (1.5 Inches) in Diameter) with 7 Pairs of Collection Screens
A new charger utilizing carbon fibers was designed and incorporated with the collector (Figure 1a). Here, an additional screen is positioned in front of the collection section screen and grounded. A carbon brush containing ~800 single carbon fibers of ~7 [micro]m in diameter is positioned in front of that screen at a distance of 0.019 m (0.75 inches) and connected to a high positive voltage. In this design, the carbon brush is located in the outer shell of the device. Once the shell is slid over the collector (two half-cylinder shells holding the screens), the carbon brush is perpendicular to the direction of the airflow and the entire unit is airtight (Figure 1b). Since the carbon brush is connected to a high positive voltage, the voltage used in the collection section is negative. During the ESBEC's operation, the high voltage between the grounded first screen and the tips of the carbon brush creates a strong electrical field which causes ion emission from the brush, and the produced ions attach to the incoming airborne particles. Once the charged particles move further into the battery, the screens connected to the voltage opposite to the sign of their charge attract the particles and remove them from the air stream. The prototype was fabricated by 3D printing technology through www.shapeways.com, and it was made of plastic (e.g., fine polyamide PA 2200). The primary goal of the small-scale model was to verify the performance of the integrated charger and collector when using polystyrene latex (PSL) particles (Duke Scientific Corp.).
Model 2: A Small-Scale, Heat-Resistant ESBEC Model (0.038 m (1.5 Inches) in Diameter) with 2 Pairs of Collection Screens
This model was produced from a heat-resistant and electrically non-conductive material (e.g., ceramic) to investigate ESBEC's performance at high temperatures (e.g., ~93 [degrees]C). Since it was a pilot-type test, screen holders for only two pairs of screens were fabricated by 3D printing and then placed into a ceramic housing shell (99.5% [AL.sub.2][O.sub.3], Ceramic Solution Inc.) (Figure 1c). The rest of the design was the same as in Model 1, i.e., carbon fiber brush charger was used for particle charging.
Model 3: A Large-Scale ESBEC Model (0.152 m (6 Inches) in Diameter) with 7 Pairs of Collection Screens
This model (Figure 1d) was produced using 3D printing to test ESBEC's scalability and ability to handle exhaust flow rates of typical diesel vehicles. The collector's design remained the same as in small-scale models, but the charger was redesigned to ensure that the incoming particles and produced ions are efficiently mixed in the larger air volume. We have explored using different charger configurations: single or four individual carbon brushes and either two tungsten wires or two carbon fiber strings traversing ESBEC in a crisscross pattern. Based on the laboratory experiments with polystyrene latex (PSL) particles (G500B, Duke Scientific Corp.) of 0.5 [micro]m in diameter, we determined that two tungsten strings (76.2 [micro]m in diameter) traversing ESBEC provided the best solution for this ESBEC model (Figure 1d). Here, ions are produced once a voltage differential is applied to the strings and a grounded screen positioned behind them - the same concept as in the 0.038 m diameter ESBEC - however, the carbon brush is replaced by two tungsten wire strings. The design of the rest of the collector remained unchanged.
Experimental Setup for ESBEC when Testing with Actual Diesel Emissions
The schematic diagram of the experimental setup is shown in Figure 2. It was set up outdoors on the Rutgers University Cook campus in New Brunswick, NJ. It consisted of a diesel particulate matter generator (i.e., source) (Figure 2a), a pipe system for emissions transport, exhaust pipe and flow control valves (brass ball valves, McMaster-Carr Co.) to divert the desired amount of exhaust flow to pass through ESBEC. Depending on the tested ESBEC version (0.038 m in diameter versus 0.152 m in diameter), the pipe adapters were set up accordingly for proper fit (Figures 2b and 2c). A diesel electric generator (6000-watt diesel generator, Central Maine Diesel Inc. operated with no electrical load was used as a source of diesel particulate matter. A 0.038 m diameter galvanized steel pipe (McMaster-Carr Co.) was used to transport diesel exhaust emissions from the power generator to a split, where a part of the exhaust was diverted to pass through ESBEC while the remaining diesel was exhausted through a pipe 0.102 m (4 inches) in diameter and 3.048 m (10 feet) in height. Figure 2b shows the sampling line for the 0.038 m diameter prototype; it consisted of a dilution airflow blower (model 119104, Ametek, Inc.) with HEFA filter for intake air, a thermocouple thermometer (4015CC, Cole-Parmer LLC), a particle mass monitor (pDR-1200, Thermo Fisher Inc.), a pressure gage, an after-filter and an air mover (e.g., pump). The latter was used to ensure the desired flow rate through ESBEC. A HEPA-filtered dilution airflow provided by the blower was used to adjust the diesel particulate matter concentration (4-400 mg/[m.sup.3]); the blower flow rate was controlled by a voltage transformer and a needle valve (both from McMaster-Carr Co.). When testing test the 0.152 m ESBEC diameter prototype, diesel exhaust stream was pushed through sampling train by the diesel generator and neither the dilution blower nor the air mover was needed (Figure 2c).
The air flow rate passing through ESBEC was either 25 or 145 L/min for the small-scale model and 660 or 1310 L/min for the large-scale model. The flow rate was measured downstream of ESBEC using a hot wire anemometer (model 9535, TSI Inc.) and adjusted through valve and air blower settings. These flow rates were selected so that the resulting airflow velocities of 0.37-2.1 m/s through ESBEC would be within the range of air velocities in conventional diesel particulate filters. The values are based on a typical range of DPF flow rates (11-680 [m.sup.3]/hour) and diameters (0.12-0.27 m) [25,26]. Two stable DC high voltage power supplies (205B-10R and 205B-30R, Bertan Associates, Inc.) provided power to the charger and collector of ESBEC; its charging voltage was fixed at +10 kV while its collection voltage was varied from -8 to -16 kV. During ESBEC's operation, the DPM entering the device was positively charged and then collected onto the screens by the electrostatic field between the screens.
Test Parameters and Determination of ESBEC's Collection Efficiency
The study was structured as three tasks to investigate the field performance of ESBEC with actual diesel emission and, to the extent needed, in the laboratory with PSL particles. Table 1 summarizes the experimental conditions.
Parameters of the Small-Scale ESBEC
In Test 1, the performance of ESBEC 0.038 m in diameter was tested at three DPM concentrations: low (< 10 mg/[m.sup.3]), medium (80-140 mg/[m.sup.3]), and high (320-400 mg/[m.sup.3]) using experimental setup shown in Figure 2b. The airflow rate through ESBEC was 25 L/min (corresponding to 1.5 m/s air face velocity). The DPM concentration upstream and downstream of ESBEC was measured either for 3 min (short-term test) or for up to 6 hours (long-term test). ESBEC was operated at the charging voltage of+10kV while its collection voltage was varied from -8 to -16 kV. Table 2 presents characteristics of woven stainless steel screens installed in ESBEC. The collection efficiency was measured by comparing DPM mass concentration upstream and downstream of ESBEC as described below.
In Test 3, we tested a small-scale ceramic version of 0.038 m diameter prototype (Figure 1c) at ~93 [degrees]C degrees for up to 7 hours. This pilot test was conducted at an airflow face velocity of approximately 2.1 m/s with a diesel exhaust mass concentration of 30-60 mg/[m.sup.3]. Two pairs of woven stainless steel screens of 10 x 10 mesh size and 0.508 mm (0.02 inches) in diameter with 64 % porosity were used.
Parameters of the Large-Scale ESBEC
The first step in scaling-up ESBEC was to design a charger that ensures effective particle charging in a larger air volume (factor of 64 increase compared to the 0.038 m version). We first explored several different charger configurations: a single carbon brush, four individual carbon brushes, comb-type carbon brush, as well as two and four strings (either carbon or tungsten) traversing the diameter of ESBEC. A two-string type charger is illustrated in Figure 1d. These experiments were conducted with PSL particles of 0.5 [micro]m in size at an airflow rate of 1,320 L/min (corresponding to 1.2 m/s face velocity; this was the maximum achievable velocity by our air mover). This particle size was selected to represent the typical sizes of diesel exhaust particles, i.e., less than 2.5 [micro]m in diameter and dominated by submicron particles [27, 28, 29]. The laboratory test setup is described in detail in our previous publication . Briefly, it consisted of a particle generation system, an air mover, a flow control system, and a particle monitoring system. High capacity air blower provided airflow through the system. The system was housed inside a Class II Biosafety cabinet (Type A/B3, NUAIRE Inc.). ESBEC was operated at the charging voltage of+10kV while its collection voltage was varied from -10 to -15 kV. ESBEC's performance was determined by comparing PSL particle concentration upstream and downstream of the device using a Grimm particle counter (model 1.108, Grimm Technologies Inc.). Based on these experiments, the best-performing charger configuration was selected for field experiments. Here, ESBEC was tested at the air face velocity of approximately 0.6 m/s and challenged with a diesel exhaust mass concentration of 200 mg/[m.sup.3]. Charging voltage was set at +10 kV and the collection voltage was set at -12 kV. Table 3 presents characteristics of woven stainless steel screens that were installed in ESBEC for these tests.
Determination of ESBEC Collection Efficiency
In all tests, the overall collection efficiency of ESBEC, [[eta].sub.OVERALL, DPM'] was determined by comparing the particle (PSL or DPM) mass concentration upstream and downstream of the device:
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (1)
where [C.sub.up] and [C.sub.down] are airborne particle concentrations upstream and downstream of ESBEC, respectively, when power is ON.
RESULTS AND DISCUSSION
Performance of the Small-Scale ESBEC Prototype
Figure 3 shows the collection efficiency of ESBEC when challenged with three different DPM concentrations at collection voltages ranging from -8kV to -16kV. The charging voltage was set at +10 kV The average temperature of diesel emissions at the measurement point was 19.4 [+ or -] 2.2 [degrees]C. As shown in Figure 3, the average collection efficiencies were as follows: 62 [+ or -] 18% at -8 kV, 67 [+ or -] 20% at -10 kV, 88 [+ or -] 4% at -12 kV, 91 [+ or -] 3% at -14 kV, and 92 [+ or -] 3% at -16 kV. As could be expected, increasing voltage applied to the collection electrodes improved the sampler's collection efficiency. Overall, the collection efficiency greater than 80% was achieved at negative collection voltages higher than 12kV
The results also indicated that the collection efficiency increased with increasing DPM concentration at each used collection voltage, with this dependency being most pronounced at -8 and -lOkV. At these two voltages, the collection efficiency at the medium mass concentration was 11% higher than that at the low mass concentration, while the efficiency at high DPM concentration was 68% higher than that at the low mass concentration. About 90% of diesel exhaust particles are ultrafine particles , but particles of such size rapidly accumulate into larger accumulation mode particles, especially at their high concentrations . Since the larger particles acquire greater electrical mobility during the same charging time compared to their smaller particles , they are collected with greater efficiency compared to smaller particles, which are dominant at lower DPM concentrations. However, at -12 to -16kV collection voltages, the observed increase in the collection efficiency with the increasing mass concentration shows little change because the magnitude or strength of the electrostatic field seems to be sufficient to capture charged particles regardless of the degree of agglomeration. A two-way ANOVA with Holm-Sidak posthoc method indicated a statistically significant effect of both collection voltage and DPM concentration. When pair-wise comparisons of collection efficiency at different DPM concentrations were performed for each collection voltage, the collection efficiency at different DPM was statistically different (p < 0.05) for all collection voltages except between medium and high DPM concentrations at -12 and -16 kV.
The ESBEC performance is visually illustrated in Figure 4 that shows DPM collected on filters downstream of ESBEC with its power OFF and power ON. This test was performed at DPM concentration of 370-400 mg/[m.sup.3], and collection times were 5 min.
Since ESBEC showed collection efficiency of 80-100 % in the short-term test (Figure 4). we were encouraged by the result and performed a long-term sampling of 6 hours; the observed collection efficiency is presented in Figure 5.
Here, the average collection efficiency was 98.8 [+ or -] 0.3% when sampling at +10/-12 kV charging/collection voltages and 300-400 mg/[m.sup.3] DPM concentration. The collection efficiency was very consistent over the entire test period (coefficient of variation = 0.3%). It is also important to note that the pressure drop across ESBEC remained low after 6 hours of continuous operation: approximately 2.49 Pa.
Performance of a Large-Scale (6 in Diameter) ESBEC Prototype
Following successful results with a small-scale ESBEC model (0.038 m in diameter), we began development of a large-scale (0.152 m in diameter) model capable of handling exhaust flow rates of typical vehicles. In the initial experiments, we explored several different ionizer designs when collecting 0.5 [micro]m PSL particles at an airflow velocity of 1.2 m/s as described in Methods. The string type chargers showed the best performance. When ESBEC with an ionizer based on carbon fiber strings was tested against ESBEC with an ionizer based on tungsten wire strings, average collection efficiencies of 83.7 [+ or -] 4.6% and 65.3 [+ or -] 4.1%, respectively, were observed. These values are averages for the collection voltage varied between -10 to -15 kV However, it also became obvious that tungsten wire (76.2 [micro]m in diameter) is easier to work with and offers better resistance to high temperature than carbon fiber materials. Thus, ionizer based on tungsten wire was chosen for field experiments.
During field experiments, DPM concentration was approximately 200 mg/[m.sup.3], and airflow velocity through ESBEC was approximately 0.6 m/s. The temperature of the diesel emissions in the sampling line varied from 40 [degrees]C to 102 [degrees]C, depending on ambient conditions during tests in May and June of 2013. This model was fabricated from plastic (e.g., fine polyamide PA 2200) by 3D printing and, therefore, did not feature any heat-resistant properties. Collection efficiency of the large-scale ESBEC model is shown in Figure 6. As could be seen, its performance depended on temperature and yielded the following collection efficiency values: 99 [+ or -] 0.01% at 40 [degrees]C, 96 [+ or -] 1.4% at 62 [degrees]C, 79 [+ or -] 5.2% at 76 [degrees]C, and 14 [+ or -] 3.9% at 98 [degrees]C. The collection efficiency clearly declines with increasing diesel exhaust temperature. We speculate that the decrease in efficiency was due to damage to 3D printing material (i.e., nominally heatproof to 80 [degrees]C) and the resulting changes to dielectric properties of the material which likely affected electrostatic field inside the unit. Once we examined the inside of ESBEC, we did observe signs of damage, including some melting of the plastic. Therefore, for the next set of experiments, ESBEC was covered with three layers of heat-resistant paint (TemperKote 600, Sherwin-Williams Co.) and extra layers of liquid insulation (LTW-400, Gardner Bender Co.). The efficiency was tested between 76 to 102 [degrees]C and the results are shown in Figure 6. As could be seen, the efficiency of the coated unit was markedly higher compared to a non-coated unit: 99 [+ or -] 0.04% at 76 [degrees]C, 71 [+ or -] 3.5% at 89 [degrees]C, and 54 [+ or -] 2.7% at 102 [degrees]C degree. At the latter temperature, ESBEC was tested with coating only.
Performance of 1.5in-Diameter Heat-Resistant ESBEC Prototype
Based on the results in Figure 6, it obvious that ESBEC should be heat-resistant at least up temperatures of 93 [degrees]C. And even higher it was also realized that the use of a heat-resistant coating with 3D printed plastic shell is a temporary measure. Thus, we began building an ESBEC housed inside a heat-resistant ceramic shell. Due to technical limitations of the 3D printing service available at the time, only a 0.038 m diameter model with two pairs of 10 x 10 mesh screens (66% open area) was built from heat-resistant ceramics. However, even having just two pairs of screens inside ESBEC served our goal to test the feasibility of a heat resistant ESBEC prototype. This ESBEC model was tested at 2.1 m/s face velocity (3.5x higher than for 0.152 m version) to account for possibly strong diesel exhaust flows. The tests were conducted for 7 hours of continuous operation, and ESBEC was operated with the charging/collection voltage of + 10/-12 kV. The DPM concentration was approximately 30-60 mg/[m.sup.3]. According to the data shown in Figure 7, the average temperature during the tests was 91.7 [+ or -] 2.2 [degrees]C and the average collection efficiency was 36 [+ or -] 1.5% (COV= 4%). The temperature varied from 89 [degrees]C to 96 [degrees]C, and it did not have a statistically significant effect on collection efficiency (p = 0.797). In addition, the pressure drop increased by only 1.87 Pa after 7 hours of continuous operation. While the observed collection efficiency may seem low, it is based on only two pairs of screens within ESBEC. The models shown in Figure 3 had seven pairs of screens; its collection efficiency due to the contribution of the first two screen sets was similar to that shown in Figure 7. Thus, the data show that a ceramic (heat resistant) prototype of ESBEC is a viable idea. A full version of a heat-resistant prototype will be built and tested in another study.
This study shows that a novel recently developed electrostatic collector can efficiently remove DPM from an air stream. The collection efficiency of a small-scale prototype was close to 100% for 6 hours of continuous operation, and pressure drop across it increased only by 2.49 Pa. The collection efficiency of a 3D-printed large-scale prototype showed a negative correlation with increasing exhaust temperature, possibly due to changes in dielectric properties of the 3D printing material at high temperatures. This problem could be seemingly solved by using heat-resistant coating materials. Our initial prototype was built from ceramics - however, only two pairs of screens were used as opposed to seven pairs in other models. It also showed a consistent performance over several hours of continuous operation and the observed pressure drop was minimal (1.87 Pa increase).
Hence, the collector concept based on electrostatic precipitation and presented here was successful in removing DPM from the air stream with minimal resistance to the exhaust flow, i.e., backpressure. Eventual application of the superhydrophobic coating to the collection screens will enable removal of the collected material without the need for thermal regeneration thus eliminating production of the nano-sized particles. These features make the proposed ESBEC design more environmentally friendly than the existing DPFs; ESBEC could be widely deployed in a variety of mobile and stationary sources to help remove particulate emissions thereby contributing to abatement of air pollution.
In the next steps of ESBEC development, a full-sized version of ESBEC (e.g., seven or more sets of screens) will be fabricated from a heat-resistant and electrically non-conductive material, e.g., ceramic or similar, and then tested in the field environment to 1) determine optimum collection screen parameters leading to long-term operation (e.g., days or weeks or months) without the need for cleaning and; 2) investigate the best approaches to clean/remove the collected diesel PM, such as using an automatic wash-off system or using multiple collection screen batteries and their periodic rotation; 3) investigate how to reuse the captured exhaust for industrial applications (e.g., tire, rubber, paints, etc.).
The next step will be a real-world application and testing of ESBEC. Here we consider two options 1) mount ESBEC on the exhaust tail pipe of a truck or bus as a second-stage filter for fine or ultrafine particles or, 2) fully retrofit a mobile source to use ESBEC as a primary filter instead of a conventional DPF. One of the possible test beds for the real-world application would be a diesel-powered fleet vehicle, such as diesel buses or various types of construction equipment vehicles (e.g., tractors, bulldozers, etc.).
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Gediminas "Gedi" Mainelis, Ph.D.
Department of Environmental Sciences
Rutgers, The State University of New Jersey
14 College Farm Road
New Brunswick, New Jersey 08901-8551, USA
This work was supported by Grant "Continuing Development and Testing of the Electrostatic Battery for Emission Control (ESBEC)" from Rutgers and The Incubation Factory.
DPF - Diesel particulate matter filter.
DPM - Diesel particulate matter.
ESBEC - Electrostatic Screen Battery for Emissions Control.
kV - kilovolt.
HEPA - High-efficiency particulate air.
Taewon Han, Huajun Zhen, and Gediminas Mainelis Rutgers, The State University of New Jersey
Table 1. Summary of experimental conditions used in this study. Test Unit Diameter, Unit Flow Test Pairs of m (inches) material rate particles screens L/min Small- 1st scale 0.038(1.5) Plastic 25 DPM 7 model Large- 1310 0.5 [micro]m 7 PSL 2nd scale 0.152(6) Plastic model 660 DPM 7 Heat- 3rd resistant 0.038(1.5) Ceramic 145 DPM 2 small scale Table 2. Characteristics of woven stainless steel screens used when testing 0.038 m diameter ESBEC prototype in Test 1. Sequential Mesh size, Screen wire Unit number of Fraction of (number of diameter, screen open area, % openings/inch) mm pair Charger 0 70 22 0.191 1 70 22 0.191 2 67 24 0.191 3 50 22 0.343 Collector 4 47 24 0.330 5 44 24 0.356 6 44 24 0.356 7 44 24 0.356 Table 3. Characteristics of woven stainless steel screens that were used when testing ESBEC prototype 0.152 m in diameter. Sequential Mesh size, Screen wire Unit number of Fraction of (number of diameter, screen open area, % openings/inch) mm pair Charger 0 64 10 0.508 1 64 10 0.508 1 70 22 0.191 2 67 24 0.191 Collector 3 50 22 0.343 4 47 24 0.330 5 44 24 0.356 6 44 24 0.356
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|Author:||Han, Taewon; Zhen, Huajun; Mainelis, Gediminas|
|Publication:||SAE International Journal of Engines|
|Date:||Dec 1, 2016|
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