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what is dpf filter?

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Answer # 1 #

Diesel particulate filters operate by trapping soot particles from the engine exhaust, preventing them from reaching the environment.  Unlike a catalytic converter which is designed to reduce gas-phase emissions flowing through the catalyst, the particulate filter is designed to trap and retain the solid particles until the particles can be oxidized or burned in the DPF itself, through a process called regeneration.

The most common diesel particulate filters in widespread use are cellular ceramic honeycomb filters with channels that are plugged at alternating ends, as shown in Figure 1.  The ends of the filter, plugged in a checkerboard pattern, force the soot-containing exhaust to flow through the porous filter walls.  While the exhaust gas can flow through the walls, the soot particles are trapped within the filter pores and in a layer on top of the channel walls.  The honeycomb design provides a large filtration area while minimizing pressure losses, and has become the standard, so-called wall-flow filter for most diesel exhaust filtration applications. Ceramic materials are widely used for particulate filters, given their good thermal durability, with the most common ceramic materials being: cordierite, silicon carbide, and aluminum titanate.

The details of the filtration process are illustrated in Figure 1(b), which shows the soot particles trapped along the inlet channel, which is open at the front end but plugged at the back end.  DPFs contain several hundred channels or cells per square inch (cpsi), with the most common being 200 cpsi.  Since half of the channels are plugged at the front of the DPF and the other half are plugged at the back of the filter, only half of the filter channels accumulate soot or ash.  That is, only the channels open on the inlet side are exposed to the “dirty” exhaust flow, while the channels open to the outlet side remain clean.  Given the small pore size and design of the honeycomb filters, DPFs can achieve a particle trapping efficiency of 99% or greater . Due to the high trapping efficiency and DPF cell design, no visible soot or ash should pass through the filter walls.  Black streaks or visible soot in the outlet channels are a sure sign of filter failure.

Soot particles are captured and retained in the DPF through a combination of depth filtration inside the filter pores and surface filtration along the channel walls. The inset in Figure 1(c) shows these two processes, where a small fraction of the soot initially accumulates in the filter pores (1) and then subsequently builds a layer along the channel walls (2).  As the soot load in the filter increases, so too does the filter’s trapping efficiency, as the accumulated soot provides an additional layer to trap incoming particles.  The specific soot filtration mechanisms, whether in the pores on the surface of the walls, plays an important role in determining the overall increase in exhaust back pressure (or pressure drop across the filter), shown in Figure 2.

The porosity of most commercial DPFs ranges from around 40% to 60%.  The walls of these filters contain a complex network of pores in the range of 10 – 30 micrometers (microns) in diameter .  In a new or clean DPF, the surface of the filter is exposed to the exhaust flow and soot rapidly accumulates in the surface pores. Although only a small fraction of the total soot accumulates in the filter micro-pores, it contributes to a steep rise in filter pressure drop shown in Figure 2.  Subsequent soot accumulation in the DPF forms a layer (cake layer) along the walls of the channel, and results in a slower and more gradual rise in filter pressure drop .  Depending on the soot loading level and filter type, the pore accumulation can account for 50% of the filter pressure drop, or more, in some cases.  The non-linear response of the DPF to material accumulation complicates the determination of filter soot or ash loading levels based on pressure drop alone

In order to reduce filter pressure drop due to soot accumulation, the filter is regenerated through a processes the burns off (oxidizes) the soot.  There are two broad categories of regeneration processes, although most commercial applications use some combination of the two.  This is particularly true with vehicles or equipment experiencing extended periods of low exhaust temperature operation, such as long periods of idle or low speed/load operating cycles.

Active Regeneration requires the addition of heat to the exhaust to increase the temperature of the soot to the point at which it will oxidize in the presence of excess oxygen in the exhaust.  The combustion of soot in oxygen typically requires temperatures above 550 °C (1,000 °F).  Since these high temperatures generally fo not occur during normal engine operation, a number of strategies are used to actively increase the exhaust temperature .  Active regeneration systems may include the use of a diesel burner to directly heat the exhaust entering the DPF or the use of a diesel oxidation catalyst (DOC) to oxidize diesel fuel over the catalyst as a means for increasing the DPF temperature.  Use of the DOC also requires excess diesel fuel in the exhaust, which may be accomplished through a fuel injector (hydrocarbon doser) mounted in the exhaust upstream of the DOC, or through late in-cylinder post injection strategies.  Other forms of active regeneration include the use of electrical heating elements, microwaves, or plasma burners.

The use of a DOC in combination with some form of exhaust fuel dosing is the most common active regeneration strategy currently used for on- and off-highway applications.  The duration of an active regeneration event generally ranges from 20 to 30 minutes on average, under normal operating conditions. In some cases, such as severe DPF soot plugging, a parked regeneration may be required, which can last up to several hours to slowly burn off the soot under more controlled conditions.  Regardless of the specific strategy, active regenerations always require additional energy input (additional fuel) to heat the exhaust and the DPF to the required temperature.

Passive Regeneration, as the name implies, does not require additional energy to carry out the regeneration process.  Instead, this strategy relies on the oxidation of soot in the presence of NO2, which can occur at much lower temperatures in the range of 250 °C to 400 °C (480 °F to 750 °F).  A catalyst is used to convert NO present in the exhaust to NO2.  These catalysts require the use of precious metals to facilitate the reaction, platinum (Pt), in particular, which adds additional cost to the system.  In some cases the catalyst coating is applied directly to the DPF, as with a catalyzed DPF (C-DPF), or an upstream oxidation catalyst (DOC) may also be used .  Many commercial systems utilize a combination of a DOC and C-DPF.  Use of the catalysts allows NO2 to be produced and soot to be oxidized at temperatures which occur during normal engine or vehicle operation.

In an ideal case, if engine operation results in a certain amount of time spent within this passive regeneration “temperature window” then active regeneration may not be needed.  In reality however, low temperature operation may occur for extended periods of time, such as long periods of idle or low load operation, particularly in cold climates, and some active regeneration may still be needed.  In the absence of active regeneration, periods of low temperature operation may be supplemented by periods of high temperature operation (such as extended highway driving) to induce passive regeneration.

In order to reduce fuel consumption, passive regeneration is preferred, although most commercial systems still use active regeneration to varying degrees, depending on the drive cycle and operating conditions. Regardless of the regeneration method, the oxidation of soot (whether active or passive) results in incombustible material, or ash, which can not be burned, and remains in the DPF.  Understanding the key differences between ash and soot, as well as their impacts on DPF performance is important when selecting the most appropriate cleaning method for the filter.

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Answer # 2 #

1) UTI is an educational institution and cannot guarantee employment or salary.

2) For program outcome information and other disclosures, visit www.uti.edu/disclosures.

3) Approximately 8,000 of the 8,400 UTI graduates in 2019 were available for employment. At the time of reporting, approximately 6,700 were employed within one year of their graduation date, for a total of 84%. This rate excludes graduates not available for employment because of continuing education, military service, health, incarceration, death or international student status. The rate includes graduates who completed manufacturer-specific advanced training programs and those employed in positions that were obtained before or during their UTI education, where the primary job duties after graduation align with the educational and training objectives of the program. UTI is an educational institution and cannot guarantee employment or salary.

5) UTI programs prepare graduates for careers in industries using the provided training, primarily as automotive, diesel, collision repair, motorcycle and marine technicians. Some UTI graduates get jobs within their field of study in positions other than as a technician, such as: parts associate, service writer, fabricator, paint and paint prep, and shop owner/operator. UTI is an educational institution and cannot guarantee employment or salary.

6) UTI graduates' achievements may vary. Individual circumstances and wages depend on personal credentials and economic factors. Work experience, industry certifications, the location of the employer and their compensation programs affect wages. UTI is an educational institution and cannot guarantee employment or salary.

7) Some programs may require longer than one year to complete.

10) Financial aid, scholarships and grants are available to those who qualify. Awards vary due to specific conditions, criteria and state.

11) See program details for eligibility requirements and conditions that may apply.

12) Based on data compiled from the U.S. Bureau of Labor Statistics, Employment Projections (2016-2026), www.bls.gov, viewed October 24, 2017. The projected number of annual job openings, by job classification is: Automotive Service Technicians and Mechanics, 75,900; Bus and Truck Mechanics and Diesel Engine Specialists, 28,300; Automotive Body and Related Repairers, 17,200. Job openings include openings due to growth and net replacements.

14) Incentive programs and employee eligibility are at the discretion of the employer and available at select locations. Special conditions may apply. Talk to potential employers to learn more about the programs available in your area.

15) Manufacturer-paid advanced training programs are conducted by UTI on behalf of manufacturers who determine acceptance criteria and conditions. These programs are not part of UTI’s accreditation. Programs available at select locations.

16) Not all programs are accredited by the ASE Education Foundation.

20) VA benefits may not be available at all campus locations.

21) GI Bill® is a registered trademark of the U.S. Department of Veterans Affairs (VA). More information about education benefits offered by VA is available at the official U.S. government website.

22) Salute to Service Grant is available to all eligible veterans at all campus locations. The Yellow Ribbon program is approved at our Avondale, Dallas/Fort Worth, Long Beach, Orlando, Rancho Cucamonga and Sacramento campus locations.

24) NASCAR Technical Institute prepares graduates to work as entry-level automotive service technicians. Graduates who take NASCAR-specific electives also may have job opportunities in racing-related industries. Of those 2019 graduates who took electives, approximately 20% found racing-related opportunities. NASCAR Tech’s overall employment rate for 2019 was 84%.

25) Estimated annual median salary for Automotive Service Technicians and Mechanics in the U.S. Bureau of Labor Statistics’ Occupational Employment and Wages, May 2020. UTI is an educational institution and cannot guarantee employment or salary. UTI graduates’ achievements may vary. Individual circumstances and wages depend on personal credentials and economic factors. Work experience, industry certifications, the location of the employer and their compensation programs affect wages. Entry-level salaries are lower. UTI programs prepare graduates for careers in industries using the provided training, primarily as automotive technicians. Some UTI graduates get jobs within their field of study in positions other than as a technician, such as service writer, smog inspector and parts manager. Salary information for the Commonwealth of Massachusetts: The average annual entry-level salary range for persons employed as Automotive Service Technicians and Mechanics in the Commonwealth of Massachusetts (49-3023) is $32,140 to $53,430 (Massachusetts Labor and Workforce Development, May 2020 data, viewed January 19, 2022, https://lmi.dua.eol.mass.gov/lmi/OccupationalEmploymentAndWageSpecificOccupations#). North Carolina salary information: The U.S. Department of Labor estimate of hourly earnings of the middle 50% for skilled automotive technicians in North Carolina, published May 2021, is $20.59. The Bureau of Labor Statistics does not publish entry-level salary data. However, the 25th and 10th percentile of hourly earnings in North Carolina are $14.55 and $11.27, respectively. (Bureau of Labor Statistics, U.S. Department of Labor, Occupational Employment and Wages, May 2020. Automotive Service Technicians and Mechanics, viewed June 2, 2021.)

26) Estimated annual median salary for Welders, Cutters, Solderers, and Brazers in the U.S. Bureau of Labor Statistics’ Occupational Employment and Wages, May 2020. UTI is an educational institution and cannot guarantee employment or salary. UTI graduates’ achievements may vary. Individual circumstances and wages depend on personal credentials and economic factors. Work experience, industry certifications, the location of the employer and their compensation programs affect wages. Entry-level salaries are lower. UTI programs prepare graduates for careers in industries using the provided training, primarily as welding technicians. Some UTI graduates get jobs within their field of study in positions other than as a technician, such as inspector and quality control. Salary information for the Commonwealth of Massachusetts: The average annual entry-level salary range for persons employed as Welders, Cutters, Solderers, and Brazers in the Commonwealth of Massachusetts (51-4121) is $36,160 to $50,810 (Massachusetts Labor and Workforce Development, May 2020 data, viewed January 19, 2022, https://lmi.dua.eol.mass.gov/lmi/OccupationalEmploymentAndWageSpecificOccupations#). North Carolina salary information: The U.S. Department of Labor estimate of hourly earnings of the middle 50% for skilled welders in North Carolina, published May 2021, is $20.28. The Bureau of Labor Statistics does not publish entry-level salary data. However, the 25th and 10th percentile of hourly earnings in North Carolina are $16.97 and $14.24, respectively. (Bureau of Labor Statistics, U.S. Department of Labor, Occupational Employment and Wages, May 2020. Welders, Cutters, Solderers, and Brazers, viewed June 2, 2021.)

27) Does not include time required to complete a qualifying prerequisite program of 18 weeks plus an additional 12 weeks or 24 weeks in manufacturer-specific training, depending on the manufacturer.

28) Estimated annual median salary for Automotive Body and Related Repairers in the U.S. Bureau of Labor Statistics’ Occupational Employment and Wages, May 2020. UTI is an educational institution and cannot guarantee employment or salary. UTI graduates’ achievements may vary. Individual circumstances and wages depend on personal credentials and economic factors. Work experience, industry certifications, the location of the employer and their compensation programs affect wages. Entry-level salaries are lower. UTI programs prepare graduates for careers in industries using the provided training, primarily as collision repair technicians. Some UTI graduates get jobs within their field of study in positions other than as a technician, such as appraiser, estimator and inspector. Salary information for the Commonwealth of Massachusetts: The average annual entry-level salary range for persons employed as Automotive Body and Related Repairers (49-3021) in the Commonwealth of Massachusetts is $30,400 to $34,240 (Massachusetts Labor and Workforce Development, May 2020 data, viewed January 19, 2022, https://lmi.dua.eol.mass.gov/lmi/OccupationalEmploymentAndWageSpecificOccupations#). North Carolina salary information: The U.S. Department of Labor estimate of hourly earnings of the middle 50% for skilled collision technicians in North Carolina, published May 2021, is $23.40. The Bureau of Labor Statistics does not publish entry-level salary data. However, the 25th and 10th percentile of hourly earnings in North Carolina are $17.94 and $13.99, respectively. (Bureau of Labor Statistics, U.S. Department of Labor, Occupational Employment and Wages, May 2020. Automotive Body and Related Repairers, viewed June 2, 2021.)

29) Estimated annual median salary for Bus and Truck Mechanics and Diesel Engine Specialists in the U.S. Bureau of Labor Statistics’ Occupational Employment and Wages, May 2020. UTI is an educational institution and cannot guarantee employment or salary. UTI graduates’ achievements may vary. Individual circumstances and wages depend on personal credentials and economic factors. Work experience, industry certifications, the location of the employer and their compensation programs affect wages. Entry-level salaries are lower. UTI programs prepare graduates for careers in industries using the provided training, primarily as diesel technicians. Some UTI graduates get jobs within their field of study in positions other than as a diesel truck technician, such as maintenance technician, locomotive technician and marine diesel technician. Salary information for the Commonwealth of Massachusetts: The average annual entry-level salary range for persons employed as Bus and Truck Mechanics and Diesel Engine Specialists (49-3031) in the Commonwealth of Massachusetts is $32,360 to $94,400 (Massachusetts Labor and Workforce Development, May 2020 data, viewed January 19, 2022, https://lmi.dua.eol.mass.gov/lmi/OccupationalEmploymentAndWageSpecificOccupations#). North Carolina salary information: The U.S. Department of Labor estimate of hourly earnings of the middle 50% for skilled diesel technicians in North Carolina, published May 2021, is $23.20. The Bureau of Labor Statistics does not publish entry-level salary data. However, the 25th and 10th percentile of hourly earnings in North Carolina are $19.41 and $16.18, respectively. (Bureau of Labor Statistics, U.S. Department of Labor, Occupational Employment and Wages, May 2020. Bus and Truck Mechanics and Diesel Engine Specialists, viewed June 2, 2021.)

30) Estimated annual median salary for Motorcycle Mechanics in the U.S. Bureau of Labor Statistics’ Occupational Employment and Wages, May 2020. MMI is an educational institution and cannot guarantee employment or salary. MMI graduates’ achievements may vary. Individual circumstances and wages depend on personal credentials and economic factors. Work experience, industry certifications, the location of the employer and their compensation programs affect wages. Entry-level salaries are lower. MMI programs prepare graduates for careers in industries using the provided training, primarily as motorcycle technicians. Some MMI graduates get jobs within their field of study in positions other than as a technician, such as service writer, equipment maintenance, and parts associate. Salary information for the Commonwealth of Massachusetts: The average annual entry-level salary for persons employed as Motorcycle Mechanics (49-3052) in the Commonwealth of Massachusetts is $30,660 (Massachusetts Labor and Workforce Development, May 2020 data, viewed January 19, 2022, https://lmi.dua.eol.mass.gov/lmi/OccupationalEmploymentAndWageSpecificOccupations#). North Carolina salary information: The U.S. Department of Labor estimate of hourly earnings of the middle 50% for skilled motorcycle technicians in North Carolina, published May 2021, is $15.94. The Bureau of Labor Statistics does not publish entry-level salary data. However, the 25th and 10th percentile of hourly earnings in North Carolina are $12.31 and $10.56, respectively. (Bureau of Labor Statistics, U.S. Department of Labor, Occupational Employment and Wages, May 2020. Motorcycle Mechanics, viewed June 2, 2021.)

31) Estimated annual median salary for Motorboat Mechanics and Service Technicians in the U.S. Bureau of Labor Statistics’ Occupational Employment and Wages, May 2020. MMI is an educational institution and cannot guarantee employment or salary. MMI graduates’ achievements may vary. Individual circumstances and wages depend on personal credentials and economic factors. Work experience, industry certifications, the location of the employer and their compensation programs affect wages. Entry-level salaries are lower. MMI programs prepare graduates for careers in industries using the provided training, primarily as marine technicians. Some MMI graduates get jobs within their field of study in positions other than as a technician, such as equipment maintenance, inspector and parts associate. Salary information for the Commonwealth of Massachusetts: The average annual entry-level salary range for persons employed as Motorboat Mechanics and Service Technicians (49-3051) in the Commonwealth of Massachusetts is $32,760 to $42,570 (Massachusetts Labor and Workforce Development, May 2020 data, viewed January 19, 2022, https://lmi.dua.eol.mass.gov/lmi/OccupationalEmploymentAndWageSpecificOccupations#). North Carolina salary information: The U.S. Department of Labor estimate of hourly earnings of the middle 50% for skilled marine technician in North Carolina, published May 2021, is $18.61. The Bureau of Labor Statistics does not publish entry-level salary data. However, the 25th and 10th percentile of hourly earnings in North Carolina are $15.18 and $12.87, respectively. (Bureau of Labor Statistics, U.S. Department of Labor, Occupational Employment and Wages, May 2020. Motorboat Mechanics and Service Technicians, viewed June 2, 2021.)

33) Courses vary by campus. For details, contact the program representative at the campus you are interested in attending.

34) Estimated annual median salary for Computer Numerically Controlled Tool Operators in the U.S. Bureau of Labor Statistics’ Occupational Employment and Wages, May 2020. UTI is an educational institution and cannot guarantee employment or salary. UTI graduates’ achievements may vary. Individual circumstances and wages depend on personal credentials and economic factors. Work experience, industry certifications, the location of the employer and their compensation programs affect wages. Entry-level salaries are lower. UTI programs prepare graduates for careers in industries using the provided training, primarily as CNC machining technicians. Some UTI graduates get jobs within their field of study in positions other than as a technician, such as CNC operator, apprentice machinist, and machined parts inspector. Salary information for the Commonwealth of Massachusetts: The average annual entry-level salary for persons employed as Computer-Controlled Machine Tool Operators, Metal and Plastic (51-4011) in the Commonwealth of Massachusetts is $35,140 (Massachusetts Labor and Workforce Development, May 2020 data, viewed January 19, 2022, https://lmi.dua.eol.mass.gov/lmi/OccupationalEmploymentAndWageSpecificOccupations#). North Carolina salary information: The U.S. Department of Labor estimate of hourly earnings of the middle 50% for skilled CNC machinists in North Carolina, published May 2021, is $20.24. The Bureau of Labor Statistics does not publish entry-level salary data. However, the 25th and 10th percentile of hourly earnings in North Carolina are $16.56 and $13.97, respectively. (Bureau of Labor Statistics, U.S. Department of Labor, Occupational Employment and Wages, May 2020. Computer Numerically Controlled Tool Operators, viewed June 2, 2021.)

36) Students enrolled in select UTI programs are eligible to apply for the Early Employment Program. Participating employers will contact selected applicants to conduct interviews. Hiring, employee retention and compensation decisions are made solely by the prospective employer. Employer participation and program details are subject to change. For additional information, please contact Career Services. UTI is an educational institution and cannot guarantee employment or salary.

37) Power & Performance courses are not offered at NASCAR Technical Institute. UTI is an educational institution and cannot guarantee employment or salary. For program outcome information and other disclosures, visit www.uti.edu/disclosures.

38) The U.S. Bureau of Labor Statistics projects that total national employment in each of the following occupations by 2030 will be: Automotive Service Technicians and Mechanics, 705,900; Welders, Cutters, Solderers, and Brazers, 452,400; Bus and Truck Mechanics and Diesel Engine Specialists, 296,800; Automotive Body and Related Repairers, 161,800; and Computer Numerically Controlled Tool Operators, 154,500.  See Table 1.2 Employment by detailed occupation, 2020 and projected 2030, U.S. Bureau of Labor Statistics, www.bls.gov, viewed November 18, 2021. UTI is an educational institution and cannot guarantee employment or salary. Updated on November 18, 2021.

39) Refresher training available to graduates only if the course is still available and space is available. Students are responsible for any other costs such as lab fees associated with the course.

41) For Automotive Service Technicians and Mechanics, the U.S. Bureau of Labor Statistics projects an annual average of 69,000 job openings between 2020 and 2030. Job openings include openings due to net employment changes and net replacements. See Table 1.10 Occupational separations and openings, projected 2020–30, U.S. Bureau of Labor Statistics, www.bls.gov, viewed November 18, 2021. UTI is an educational institution and cannot guarantee employment or salary. Updated on November 18, 2021.

42) For Welders, Cutters, Solderers, and Brazers, the U.S. Bureau of Labor Statistics projects an annual average of 49,200 job openings between 2020 and 2030. Job openings include openings due to net employment changes and net replacements. See Table 1.10 Occupational separations and openings, projected 2020–30, U.S. Bureau of Labor Statistics, www.bls.gov, viewed November 18, 2021. UTI is an educational institution and cannot guarantee employment or salary. Updated on November 18, 2021.

43) For Bus and Truck Mechanics and Diesel Engine Specialists, the U.S. Bureau of Labor Statistics projects an annual average of 28,100 job openings between 2020 and 2030. Job openings include openings due to net employment changes and net replacements. See Table 1.10 Occupational separations and openings, projected 2020–30, U.S. Bureau of Labor Statistics, www.bls.gov, viewed November 18, 2021. UTI is an educational institution and cannot guarantee employment or salary. Updated on November 18, 2021.

44) For Automotive Body and Related Repairers, the U.S. Bureau of Labor Statistics projects an annual average of 15,200 job openings between 2020 and 2030. Job openings include openings due to net employment changes and net replacements. See Table 1.10 Occupational separations and openings, projected 2020–30, U.S. Bureau of Labor Statistics, www.bls.gov, viewed November 18, 2021. UTI is an educational institution and cannot guarantee employment or salary. Updated on November 18, 2021.

45) For Computer Numerically Controlled Tool Operators, the U.S. Bureau of Labor Statistics projects an annual average of 16,500 job openings between 2020 and 2030. Job openings include openings due to net employment changes and net replacements. See Table 1.10 Occupational separations and openings, projected 2020–30, U.S. Bureau of Labor Statistics, www.bls.gov, viewed November 18, 2021. UTI is an educational institution and cannot guarantee employment or salary. Updated on November 18, 2021.

46) Students must maintain a minimum 3.5 GPA and 95% attendance rate.

47) The U.S. Bureau of Labor Statistics projects that total national employment for Automotive Service Technicians and Mechanics will be 705,900 by 2030. See Table 1.2 Employment by detailed occupation, 2020 and projected 2030, U.S. Bureau of Labor Statistics, www.bls.gov, viewed November 18, 2021. UTI is an educational institution and cannot guarantee employment or salary. Updated on November 18, 2021.

48) The U.S. Bureau of Labor Statistics projects that total national employment for Bus and Truck Mechanics and Diesel Engine Specialists will be 296,800 by 2030. See Table 1.2 Employment by detailed occupation, 2020 and projected 2030, U.S. Bureau of Labor Statistics, www.bls.gov, viewed November 18, 2021. UTI is an educational institution and cannot guarantee employment or salary. Updated on November 18, 2021.

49) The U.S. Bureau of Labor Statistics projects that total national employment for Automotive Body and Related Repairers will be 161,800 by 2030 See Table 1.2 Employment by detailed occupation, 2020 and projected 2030, U.S. Bureau of Labor Statistics, www.bls.gov, viewed November 18, 2021. UTI is an educational institution and cannot guarantee employment or salary. Updated on November 18, 2021.

50) The U.S. Bureau of Labor Statistics projects that total national employment for Welders, Cutters, Solderers, and Brazers will be 452,400 by 2030. See Table 1.2 Employment by detailed occupation, 2020 and projected 2030, U.S. Bureau of Labor Statistics, www.bls.gov, viewed November 18, 2021. UTI is an educational institution and cannot guarantee employment or salary. Updated on November 18, 2021.

51) The U.S. Bureau of Labor Statistics projects that total national employment for Computer Numerically Controlled Tool Operators will be 154,500 by 2030. See Table 1.2 Employment by detailed occupation, 2020 and projected 2030, U.S. Bureau of Labor Statistics, www.bls.gov, viewed November 18, 2021. UTI is an educational institution and cannot guarantee employment or salary. Updated on November 18, 2021.

52) The U.S. Bureau of Labor Statistics projects the national average annual job openings in each of the following occupations between 2020 and 2030 will be: Automotive Service Technicians and Mechanics, 69,000; Bus and Truck Mechanics and Diesel Engine Specialists, 28,100; and Welders, Cutters, Solderers, and Brazers, 49,200. Job openings include openings due to net employment changes and net replacements. See Table 1.10 Occupational separations and openings, projected 2020–30, U.S. Bureau of Labor Statistics, www.bls.gov, viewed November 18, 2021. UTI is an educational institution and cannot guarantee employment or salary. Approved on November 18, 2021.

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Answer # 3 #

A diesel particulate filter (DPF) is a device designed to remove diesel particulate matter or soot from the exhaust gas of a diesel engine.

Wall-flow diesel particulate filters usually remove 85% or more of the soot, and under certain conditions can attain soot removal efficiencies approaching 100%. Some filters are single-use, intended for disposal and replacement once full of accumulated ash. Others are designed to burn off the accumulated particulate either passively through the use of a catalyst or by active means such as a fuel burner which heats the filter to soot combustion temperatures. This is accomplished by engine programming to run (when the filter is full) in a manner that elevates exhaust temperature, in conjunction with an extra fuel injector in the exhaust stream that injects fuel to react with a catalyst element to burn off accumulated soot in the DPF filter, or through other methods. This is known as filter regeneration. Cleaning is also required as part of periodic maintenance, and it must be done carefully to avoid damaging the filter. Failure of fuel injectors or turbochargers resulting in contamination of the filter with raw diesel or engine oil can also necessitate cleaning. The regeneration process occurs at road speeds higher than can generally be attained on city streets; vehicles driven exclusively at low speeds in urban traffic can require periodic trips at higher speeds to clean out the DPF. If the driver ignores the warning light and waits too long to operate the vehicle above 60 km/h (40 mph), the DPF may not regenerate properly, and continued operation past that point may spoil the DPF completely so it must be replaced. Some newer diesel engines, namely those installed in combination vehicles, can also perform what is called a Parked Regeneration, where the engine increases RPM to around 1400 while parked, to increase the temperature of the exhaust.

Diesel engines produce a variety of particles during the combustion of the fuel/air mix due to incomplete combustion. The composition of the particles varies widely dependent upon engine type, age, and the emissions specification that the engine was designed to meet. Two-stroke diesel engines produce more particulate per unit of power than do four-stroke diesel engines, as they burn the fuel-air mix less completely.

Diesel particulate matter resulting from the incomplete combustion of diesel fuel produces soot (black carbon) particles. These particles include tiny nanoparticles—smaller than one micrometre (one micron). Soot and other particles from diesel engines worsen the particulate matter pollution in the air and are harmful to health. New particulate filters can capture from 30% to greater than 95% of the harmful soot. With an optimal diesel particulate filter (DPF), soot emissions may be decreased to 0.001 g/km or less.

The quality of the fuel also influences the formation of these particles. For example, a high sulphur content diesel produces more particles. Lower sulphur fuel produces fewer particles, and allows use of particulate filters. The injection pressure of diesel also influences the formation of fine particles.

Diesel particulate filtering was first considered in the 1970s due to concerns regarding the impacts of inhaled particulates. Particulate filters have been in use on non-road machines since 1980, and in automobiles since 1985. Historically medium and heavy duty diesel engine emissions were not regulated until 1987 when the first California Heavy Truck rule was introduced capping particulate emissions at 0.60 g/BHP Hour. Since then, progressively tighter standards have been introduced for light- and heavy-duty roadgoing diesel-powered vehicles and for off-road diesel engines. Similar regulations have also been adopted by the European Union and some individual European countries, most Asian countries, and the rest of North and South America.

While no jurisdiction has explicitly made filters mandatory, the increasingly stringent emissions regulations that engine manufacturers must meet mean that eventually all on-road diesel engines will be fitted with them. In the European Union, filters are expected to be necessary to meet the Euro.VI heavy truck engine emissions regulations currently under discussion and planned for the 2012-2013 time frame. In 2000, in anticipation of the future Euro 5 regulations PSA Peugeot Citroën became the first company to make filters standard on passenger cars.

As of December 2008 the California Air Resources Board (CARB) established the 2008 California Statewide Truck and Bus Rule which—with variance according to vehicle type, size and usage—requires that on-road diesel heavy trucks and buses in California be retrofitted, repowered, or replaced to reduce particulate matter (PM) emissions by at least 85%. Retrofitting the engines with CARB-approved diesel particulate filters is one way to fulfill this requirement. In 2009 the American Recovery and Reinvestment Act provided funding to assist owners in offsetting the cost of diesel retrofits for their vehicles. Other jurisdictions have also launched retrofit programs, including:

Inadequately maintained particulate filters on vehicles with diesel engines are prone to soot buildup, which can cause engine problems due to high back pressure.

In 2018 the UK made changes to its MOT test requirements, including tougher scrutiny of diesel cars. One requirement was to have a properly fitted and working DPF. Driving without a DPF could incur a £1000 fine.

Unlike a catalytic converter which is a flow-through device, a DPF retains bigger exhaust gas particles by forcing the gas to flow through the filter; however, the DPF does not retain small particles. Maintenance-free DPFs oxidise or burn larger particles until they are small enough to pass through the filter, though often particles "clump" together in the DPF reducing the overall particle count as well as overall mass. There are a variety of diesel particulate filter technologies on the market. Each is designed around similar requirements:

The most common filter is made of cordierite (a ceramic material that is also used as catalytic converter supports (cores)). Cordierite filters provide excellent filtration efficiency, are relatively inexpensive, and have thermal properties that make packaging them for installation in the vehicle simple. The major drawback is that cordierite has a relatively low melting point (about 1200 °C) and cordierite substrates have been known to melt during filter regeneration. This is mostly an issue if the filter has become loaded more heavily than usual, and is more of an issue with passive systems than with active systems, unless there is a system breakdown.

Cordierite filter cores look like catalytic converter cores that have had alternate channels plugged - the plugs force the exhaust gas flow through the wall and the particulate collects on the inlet face.

The second most popular filter material is silicon carbide, or SiC. It has a higher (2700 °C) melting point than cordierite, however, it is not as stable thermally, making packaging an issue. Small SiC cores are made of single pieces, while larger cores are made in segments, which are separated by a special cement so that heat expansion of the core will be taken up by the cement, and not the package. SiC cores are usually more expensive than cordierite cores, however they are manufactured in similar sizes, and one can often be used to replace the other. Silicon carbide filter cores also look like catalytic converter cores that have had alternate channels plugged - again the plugs force the exhaust gas flow through the wall and the particulate collects on the inlet face.

The characteristics of the wall flow diesel particulate filter substrate are:

Fibrous ceramic filters are made from several different types of ceramic fibers that are mixed together to form a porous medium. This medium can be formed into almost any shape and can be customized to suit various applications. The porosity can be controlled in order to produce high flow, lower efficiency or high efficiency lower volume filtration. Fibrous filters have an advantage over wall flow design of producing lower back pressure. Fibrous ceramic filters remove carbon particulates almost completely, including fine particulates less than 100 nanometres (nm) diameter with an efficiency of greater than 95% in mass and greater than 99% in number of particles over a wide range of engine operating conditions. Since the continuous flow of soot into the filter would eventually block it, it is necessary to 'regenerate' the filtration properties of the filter by burning off the collected particulate on a regular basis. Soot particulate burn-off forms water and CO2 in small quantities amounting to less than 0.05% of the CO2 emitted by the engine.

Some cores are made from metal fibers – generally the fibers are "woven" into a monolith. Such cores have the advantage that an electrical current can be passed through the monolith to heat the core for regeneration purposes, allowing the filter to regenerate at low exhaust temperatures and/or low exhaust flow rates. Metal fiber cores tend to be more expensive than cordierite or silicon carbide cores, and are generally not interchangeable with them because of the electrical requirement.

Disposable paper cores are used in certain specialty applications, without a regeneration strategy. Coal mines are common users – the exhaust gas is usually first passed through a water trap to cool it, and then through the filter. Paper filters are also used when a diesel machine must be used indoors for short periods of time, such as on a forklift being used to install equipment inside a store.

There are a variety of devices that produce over 50% particulate matter filtration, but less than 85%. Partial filters come in a variety of materials. The only commonality between them is that they produce more back pressure than a catalytic converter, and less than a diesel particulate filter. Partial filter technology is popular for retrofit.

Filters require more maintenance than catalytic converters. Soot, a byproduct of oil consumption from normal engine operation, builds up in the filter as it cannot be converted into a gas and pass through the walls of the filter. This increases the pressure before the filter.

DPF filters go through a regeneration process which removes this soot and lowers the filter pressure. There are three types of regeneration: passive, active, and forced. Passive regeneration takes place normally while driving, when engine load and vehicle drive-cycle create temperatures that are high enough to regenerate the soot buildup on the DPF walls. Active regeneration happens while the vehicle is in use, when low engine load and lower exhaust gas temperatures inhibit the naturally occurring passive regeneration. Sensors upstream and downstream of the DPF (or a differential pressure sensor) provide readings that initiate a metered addition of fuel into the exhaust stream. There are two methods to inject fuel, either downstream injection directly into the exhaust stream, downstream of the turbo, or fuel injection into the engine cylinders on the exhaust stroke. This fuel and exhaust gas mixture passes through the Diesel Oxidation Catalyst (DOC) creating temperatures high enough to burn off the accumulated soot. Once the pressure drop across the DPF lowers to a calculated value, the process ends, until the soot accumulation builds up again. This works well for vehicles that drive longer distances with few stops compared to those that perform short trips with many starts and stops. If the filter develops too much pressure then the last type of regeneration must be used - a forced regeneration. This can be accomplished in two ways. The vehicle operator can initiate the regeneration via a dashboard mounted switch. Various signal interlocks, such as park brake applied, transmission in neutral, engine coolant temperature, and an absence of engine related fault codes are required (vary by OEM and application) for this process to initiate. When the soot accumulation reaches a level that is potentially damaging to the engine or the exhaust system, the solution involves a garage using a computer program to run a regeneration of the DPF manually.

When a regeneration occurs, the soot is turned to gasses and ash of which some remains in the filter. This will increase restriction through the filter and can result in a blockage. Warnings are given to the driver before filter restriction causes an issue with driveability or damage to the engine or filter develop. Regular filter maintenance is a necessity to remove ash build up, either through cleaning or replacement of the filter.

In 2011, Ford recalled 37,400 F-Series trucks with diesel engines after fuel and oil leaks caused fires in the diesel particulate filters of the trucks. No injuries occurred before the recall, though one grass fire was started. A similar recall was issued for 2005-2007 Jaguar S-Type and XJ diesels, where large amounts of soot became trapped in the DPF In affected vehicles, smoke and fire emanated from the vehicle underside, accompanied by flames from the rear of the exhaust. The heat from the fire could cause heating through the transmission tunnel to the interior, melting interior components and potentially causing interior fires.

Regeneration is the process of burning off (oxidizing) the accumulated soot from the filter. This is done either passively (from the engine's exhaust heat in normal operation or by adding a catalyst to the filter) or actively introducing very high heat into the exhaust system. On-board active filter management can use a variety of strategies:

All on-board active systems use extra fuel, whether through burning to heat the DPF, or providing extra power to the DPF's electrical system, although the use of a fuel borne catalyst reduces the energy required very significantly. Typically a computer monitors one or more sensors that measure back pressure and/or temperature, and based on pre-programmed set points the computer makes decisions on when to activate the regeneration cycle. The additional fuel can be supplied by a metering pump. Running the cycle too often while keeping the back pressure in the exhaust system low will result in high fuel consumption. Not running the regeneration cycle soon enough increases the risk of engine damage and/or uncontrolled regeneration (thermal runaway) and possible DPF failure.

Diesel particulate matter burns when temperatures above 600 °C are attained. This temperature can be reduced to somewhere in the range of 350 to 450 °C by use of a fuel-borne catalyst. The actual temperature of soot burn-out will depend on the chemistry employed. In the mid-2010s, scientists at 3M developed a magnesium doped version of traditional iron based catalysts which lowered the temperature required for particulate matter oxidation to just over 200 °C. The lower reaction temperature is made possible by the dopant allowing the Fe lattice to hold more oxygen. This advancement is significant because it allows the cleaning reaction to take place at the standard operating temperature of most diesel engines, removing the requirement for burning extra fuel or otherwise artificially heating the engine. The family of Mg doped catalysts, named Grindstaff catalysts after the chemist who started the work, has been the subject of much investigation across industry and academia with the tightening of emissions regulations on particulate matter world wide.

In some cases, in the absence of a fuel-borne catalyst, the combustion of the particulate matter can raise temperatures so high, that they are above the structural integrity threshold of the filter material, which can cause catastrophic failure of the substrate. Various strategies have been developed to limit this possibility. Note that unlike a spark-ignited engine, which typically has less than 0.5% oxygen in the exhaust gas stream before the emission control device(s), diesel engines have a very high ratio of oxygen available. While the amount of available oxygen makes fast regeneration of a filter possible, it also contributes to runaway regeneration problems.

Some applications use off-board regeneration. Off-board regeneration requires operator intervention (i.e. the machine is either plugged into a wall/floor mounted regeneration station, or the filter is removed from the machine and placed in the regeneration station). Off-board regeneration is not suitable for on-road vehicles, except in situations where the vehicles are parked in a central depot when not in use. Off-board regeneration is mainly used in industrial and mining applications. Coal mines (with the attendant explosion risk from coal damp) use off-board regeneration if non-disposable filters are installed, with the regeneration stations sited in an area where non-permissible machinery is allowed.

Many forklifts may also use off-board regeneration – typically mining machinery and other machinery that spend their operational lives in one location, which makes having a stationary regeneration station practical. In situations where the filter is physically removed from the machine for regeneration there is also the advantage of being able to inspect the filter core on a daily basis (DPF cores for non-road applications are typically sized to be usable for one shift - so regeneration is a daily occurrence).

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