Browse Topic: Diesel exhaust emissions control
Upcoming, stricter diesel exhaust emissions standards will likely require aftertreatment architectures with multiple diesel exhaust fluid (DEF) introduction locations. Managing NH3 slip with technologies such as an ammonia slip catalyst (ASC) will continue to be critical in these future aftertreatment systems. In this study, we evaluate the impact of SO2 exposure on a state-of-the-art commercially available ASC. SO2 is co-fed at 0.5 or 3 ppmv to either approximate or accelerate a real-world exhaust SO2 impact. ASC performance during sulfur co-feeding is measured under a wide variety of simulated real-world conditions. Results indicate that the loss of NO conversion during SCR is dependent on the cumulative SO2 exposure, regardless of the inlet SO2 concentration. Meanwhile, N2O formation under SCR conditions is nonlinearly affected by SO2 exposure, with formation increasing during 0.5 ppmv SO2 exposure but decreasing in the presence of 3 ppmv SO2. TPO experiments reveal the formation of ammonium sulfate species, but only after prolonged SO2 exposure at 0.5ppmv or accelerated SO2 exposure at 3 ppmv. Reactivation at 550°C is sufficient to recover ASC reactivity following multiple SO2 exposure tests in all cases. These findings are especially relevant for the development of diesel exhaust aftertreatment accelerated aging protocols.
To avoid frequent regeneration intervals leading to expeditious ageing of the catalyst and substantial fuel penalty for the owner, it is always desired to estimate the soot coming from diesel exhaust emission, the soot accumulated and burnt in the Diesel Particulate Filter (DPF). Certain applications and vehicle duty cycles cannot make use of the differential pressure sensor for estimating the soot loading in the DPF because of the limitations of the sensor tolerance and measurement accuracy. The physical soot model is always active and hence a precise and more accurate model is preferred to calibrate & optimize the regeneration interval. This paper presents the approach to estimate the engine-out soot and the accumulated soot in the DPF using a graphical calculation tool (AVL Concerto CalcGraf™). The tool reduces the efforts of driving different duty cycles multiple times on the testbed and recurrent vehicle trips for data collection while calibrating the soot models, hence saving testbed cost, diesel cost, and manpower efforts. Results were established over BSVI emission legislative cycles (WHTC) and vehicle duty cycles to ratify with the model-generated data.
The Bharat Stage VI emission norms in India is driving the use of more complex after treatment systems for diesel engines, to meet the stringent emission limits. The after-treatment system typically includes theSelective Catalytic Reduction (SCR) catalyst and the Diesel Oxidation Catalyst (DOC) - Diesel Particulate Filter (DPF) systems to reduce engine out emissions of Nitrogen Oxides (NOx), hydrocarbons (HC), and particulates respectively. For a durable functioning of the aftertreatment system, cleaning of these components at regular intervals is required, the process termed as ‘regeneration’. The most common industry technique for regeneration is to use the existing injectors in the engine, to dose the extra fuel which is burnt in the DOC for regeneration. This has been a cost effective and simpler technique compared to the external hydrocarbon dosing system. But the tradeoff involved with this in-cylinder dosing technique is the risk of fuel in oil (FIO). The extra fuel injected impinges the cylinder wall and eventually get mixed with engine oil thereby diluting it. The diluted oil increases the risk of early wear and impacts the durability of the engine. This paper emphasizes on parameters impacting fuel in oil dilution due to regeneration, associated tradeoffs and some system level analysis of the same. Through six sigma, the various factors impacting FIO is studiedexperimentally using a mid-range diesel engine in an engine dynamometer. Study also considers impact of regen frequency and application level impact on oil drain interval for some on-highway commercial vehicle applications. A system level approach is formulated to understand FIO which can be used in the early phase of design and calibration of aftertreatment system.
Euro 6 emission norms are getting implemented in India from April 2020 and it is being viewed as one of the greatest challenges ever faced by the Indian automotive industry. In order to achieve such stringent emission norms along with top performance for vehicle, a good strategy should be incorporated to control system out NOx emissions and soot regeneration. Extruded Vanadium catalyst is deployed for this passive regeneration system with DOC (Diesel Oxidation Catalyst), DPF (Diesel Particulate Filter) and SCR (Selective Catalyst Reduction), where the amount of catalyst loading in DOC plays an apex role in deciding conversion efficiency of SCR and passive regeneration capabilities. This study mainly focuses on the impact of catalyst loading of DOC over SCR efficiency. NO2 to NOx ratio should be close to 0.5 for optimum conversion efficiency of SCR. Catalyst loading in DOC decides the amount of NO2 coming upstream to SCR. Higher amount NO2 from DOC will benefit in passive regeneration but it will also inhibit NOx conversion rate. An optimum trade-off should be made for the effectiveness of dual emission control. Moreover, this study has also included the effect of prolonged aging of catalyst (1000 hours) over its efficiency. With aging of catalyst, it was found that there is a drop in NO oxidation by 8-10% and improvement in SCR efficiency by 5-6% compared to the fresh catalyst system.
As agencies and governing bodies evaluate the feasibility of reduced emission standards, additional focus has been placed on technology durability. This is seen in proposed updates, which would require Original Equipment Manufacturers (OEMs) to certify engine families utilizing a full useful life (FUL) aftertreatment system. These kinds of proposed rulings would place a heavy burden on the manufacturer to generate FUL components utilizing traditional engine aging methods. Complications in this process will also increase the product development effort and will likely limit the amount of aftertreatment durability testing. There is also uncertainty regarding the aging approach and the representative impact compared to field aged units. Existing methodologies have evolved to account for several deterioration mechanisms that, when controlled, can be utilized to create a flexible aging protocol. As a result, these methodologies provide the necessary foundation for continued development. The Diesel Aftertreatment Accelerated Aging Cycle (DAAAC) protocol considers thermal loading, lubricant derived poisoning, and sulfur exposure as integral elements for aftertreatment aging. Combining these elements simulates deterioration mechanisms observed during normal vehicle operation. In doing so, these elements are introduced at an accelerated rate to reduce aging duration by a factor of ten. The following case study will consider a special application of the DAAAC protocol for an advanced aftertreatment technology demonstration. Since these technologies normally have limited field data to guide the aging cycle development process, they bring about several challenges. This includes understanding the implication of the technology on the overall system, as well as, limitations from unknown service practices. To discuss this topic in detail, an example from the CARB low NOX stage 1 demonstration program will be referenced as part of this this work. It will show that ensuring proper deterioration mechanism exposure is important to assess the overall system performance.
The increasingly stringent emission regulations have mandated the use of CCRT (catalyzed continuously regeneration trap) made by upstream DOC (diesel oxidation catalyst) and downstream CDPF (catalyzed diesel particulate filter) for heavy-duty diesel vehicles, which is proved to be the only way that can efficiently control the gaseous and particulate emissions. The performance of after-treatment is greatly influenced by the running conditions of the diesel vehicle and its exhaust parameters, so this paper intended to use grey relational analysis to study the correlation between running conditions (velocity, acceleration, VSP (vehicle specific power)), exhaust parameters (exhaust flow rate, DOC inlet temperature, concentrations of CO, THC, O2 and NOX) and the performance of DOC and CCRT based on chassis dynamometer test. Results showed that the effect of DOC on CO and THC is mainly affected by exhaust flow rate, exhaust temperature and THC concentration. This also applied to effect on CCRT on CO. But for the effect of CCRT on THC, the most important three factors are exhaust temperature, O2 and THC concentration. The trapping effect of DOC on PN (particle number) was greatly affected by vehicle speed, exhaust flow rate and exhaust temperature, while for CCRT, the trapping effect on both PN and PM (particle mass) are greatly affected by exhaust temperature, THC and O2 concentration. And the exhaust flow rate is also a noticeable factor for the effect of CCRT on PM. In terms of the pressure drop of CCRT, the important factors are ranked as: THC concentration > exhaust flow rate > PN reduction = PM reduction. In summary, the performance of DOC and CCRT was greatly affected by the exhaust flow and temperature, while the THC concentration of the engine was also a main factor.
In recent years, environmental regulations in the automotive industry have become increasingly strict, particularly with respect to emissions from diesel engines. Large amounts of these harmful emissions are released during the cfold start of a vehicle, due to the catalytic converter system not yet reaching its light-off temperature. This paper presents an induction heating system which heats the catalytic converter during a cold start, reducing the time for it to reach light-off temperature, and thus reducing cold-start emissions. Detailed dynamometer testing results are used to develop vehicle models of the induction heating system for a diesel Peugeot 308 light duty vehicle. The model is used to quantify the changes in hydrocarbons (HC), carbon monoxide (CO), carbon dioxide (CO2), oxygen (O2), nitrogen oxide (NOx), and fuel consumption on a variety of standard drive cycles. The results are then extrapolated to investigate the reduction of emissions possible on a Chevrolet Silverado 3500HD heavy-duty vehicle.
Diesel exhaust emission control systems often contain DOC (Diesel Oxidation Catalyst) + CSF (Catalyzed Soot Filter) components. In this system PM (particulate matter) is filtered and accumulated in the CSF and such filtered PM is periodically combusted by supplying heat to the CSF. The heat to CSF is generated within the DOC by an exothermic reaction with extra fuel supplied to the DOC. Here the exothermic performance of DOC depends on not only the active catalytic site (such as Pt and/or Pd) but also on the characteristics of the porous material supporting the precious metals. Various properties of Al2O3, i.e. pore diameter, pore volume, BET surface area, acidity, basicity and the Ea (activation energy) of fuel combustion, used in DOCs and PGM particle size of each DOC were measured. The fuel combustion performance of each DOC was evaluated by diesel engine bench. A correlation between various properties and the fuel combustion performance was investigated by multiple analysis software, modeFRONTIER.
The objective of this study was to obtain an improved understanding of the effects of the simultaneous use of cold flow improver (CFI) and antioxidant on the cold flow properties, oxidation stability and diesel exhaust emissions of various biodiesels and biodiesel blends. Cold flow properties were evaluated by assessing the cloud point (CP) and pour point (PP) values, as well as from the results of the cold soak filtration test (CSFT). Oxidation stability was also determined by measuring the peroxide induction period (IP). The neat biodiesels (B100) derived from soybean oil(SME), Jatropha curcus oil(JME), rice bran oil(RBME), palm oil(PME) and waste cooking oil(WME), and biodiesel blends with JIS No.2 diesel fuel were tested. A CFI and antioxidant specially designed for use in biodiesel fuels were employed during the work. The experimental data demonstrated that the addition of antioxidant had no effect on either the CP or PP values. The CSFT time value increases with increasing biodiesel content in biodiesel blends, although the addition of the CFI has little effect on the CSFT value. On the other hand, the CSFT results, however, were increased by antioxidant addition and also by increasing the CFI content in the SME(B100). The CSFT value was found to be well correlated with both CP and PP results in the case of the palm oil biodiesel. The IP value of SME(B100) is elevated with increasing CFI addition when an amine-based type antioxidant is added. We also determined that the addition of CFI and antioxidant reduces the extent of initial combustion due to premix combustion of DI diesel engines, which results in slightly decreased total unburned hydrocarbon (THC) and particulate matter (PM) emissions in exhaust at high engine loads.
A typical diesel exhaust emission control system for meeting the US EPA 2010 regulations includes one or more platinum-group metal (PGM)-containing catalysts, located upstream of an SCR unit. However, as was previously reported in literature, under certain operating conditions PGM elements can get transferred onto the downstream SCR catalyst, resulting in the loss of its NOx conversion efficiency. In the same studies, the effect of Pt poisoning was found to be mitigated by catalyst treatment at 850°C, presumably due to Pt volatilization and migration. In the present study, we have explored the process of Pt poisoning mitigation, and identified that the recovery can take place at lower temperatures, reducing the risk of hydrothermal damage to the catalyst. We have also proven that the performance recovery, observed upon treatment at 700°C, was induced by Pt sintering, rather than by volatilization, thus minimizing the risk of secondary poisoning via Pt redistribution across the SCR system. These findings pave the way for the practical rejuvenation of zeolite-based SCR catalysts, deactivated through Pt contamination.
Biofuel companies are determined to become viable on their own but want continued government assistance if oil companies receive assistance, too. Conventional liquid fuels have never been under siege as much as they are now and from more angles of attack than ever. Lithium, hydrogen, hydraulics, and biofuels-all seem destined to eat into oil's near monopoly as a vehicle fuel. Few people, however, are predicting that any or all of those alternative technologies will topple oil as the energy source of choice anytime soon. Views differ as to when (and in some cases, whether) alternatives' current niche positions will evolve into something more. Based on the idea that over-reliance on oil, especially Middle East sourced oil, is unwise, the U.S. government is providing support for all alternatives to one degree or another. With several pure- and partial-electric vehicle models recently introduced to the mass market, lithium-based energy-storage technology has finally arrived. Hydrogen and hydraulic-hybrid technology are still in the R&D stage.
To meet increasingly stringent diesel exhaust emissions requirements, original equipment manufacturers (OEMs) have introduced common rail fuel injection systems that develop pressures of up to 2000 bar (30,000 psi). In addition, fuel delivery schemes have become more complicated, often involving multiple injections per cycle. Containing higher pressures and allowing for precise metering of fuel requires very tight tolerances within the injector. These changes have made injectors more sensitive to fuel particulate contamination. Recently, problems caused by internal diesel injector deposits have been widely reported. In this paper, the results of an investigation into the chemical nature and probable sources of these deposits are discussed. Using an array of techniques, internal deposits were analyzed from on a number of sticking injectors from the field and from OEM test stands in North America. In each case, the internal deposits were found to be composed mainly of the sodium salts of alkenyl succinic acids. These salts are insoluble in ultra-low sulfur diesel (ULSD) fuel and can exist as very fine particles that pass through fuel filters, flowing to the rail and injectors. Sodium can enter diesel fuel from a number of sources including refinery salt driers, storage tank water bottoms and seawater used as ship ballast. Alkenyl succinic acids are commonly used as corrosion inhibitors to protect pipelines and other parts of the diesel fuel delivery system. Based on the proposed mechanism, an engine test was developed that reproduces the deposits and injector sticking observed in the field and OEM test stands. This test was used to identify alternate corrosion inhibitor and detergent chemistries that significantly reduce the propensity to build sticking deposits in low clearance areas inside high pressure diesel injectors.
Establishing a certain maintenance-free time period regarding modern diesel exhaust emission control systems is of major importance nowadays. One of the most serious problems Diesel Particulate Filter (DPF) manufacturers face concerning system's durability is the performance deterioration due to the filter aging because of the accumulation of the ash particles. The evaluation of the effect of the ash aging on the filter performance is a time and cost consuming task that slows down the process of manufacturing innovative filter structures and designs. In this work we present a methodology for producing filter samples aged by accumulating ash produced by the controlled pyrolysis of oil-fuel solutions. Such ash particles bear morphological (size) and compositional similarity to ash particles collected from engine aged DPFs. The ash particles obtained are compared to those from real engine operation. The ash-loaded samples are then evaluated with regard to their soot loading behavior, filtration efficiency and regeneration performance.
Combustion and aftertreatment technologies help engine manufacturers balance performance with emissions reduction. Within the off-highway world, a flurry of development has been under way for some time as OEMs continue to refine the ideal technologies to satisfy the looming wave of Tier 4 emissions standards. One look to the on-highway market reveals a number of commercially available technologies that have gained wide acceptance for treating diesel exhaust emissions, typically using some form of oxidation catalyst or particulate filtering, or some combination of both. While such exhaust management technologies are firmly established in the on-highway world, many off-highway OEMs and their suppliers have focused some of their most immediate efforts on the engine itself and the potential for avoiding or reducing emissions generation through more complete control of the combustion process. Facilitating a lower-temperature, more complete combustion reaction could help to repress the formation of the most troubling pollutants associated with diesel engines-oxides of nitrogen (NOx) and particulates, commonly referred to as soot.
Two of the goals of the Penn State FutureTruck project were to reduce the emissions of the hybrid electric Ford Explorer to ULEV or lower, and improve the fuel economy by 25% over the stock vehicle. The hybrid electric vehicle system is powered with a 103kW 2.5L Detroit Diesel engine which operates with a fuel blend consisting of ultra-low-sulfur diesel and biodiesel (35%). Lower emissions are inherently achieved by the use of biodiesel. Additionally, the engine was fitted with a series of aftertreatment devices in an effort to achieve the low emissions standards. Vehicle testing has shown a gasoline-equivalent fuel economy improvement of approximately 22%, a reduction in greenhouse gas emissions by approximately 38%, and meeting or exceeding stock emissions numbers in all other categories through the use of an advanced catalyst and control strategy. This paper will review the engine and emissions system strategy to meet the low emissions standards, detail the operation of the aftertreatment system, detail the process by which it was tested in an engine dyno lab and chassis dyno lab, and review the control optimization. Most importantly, the data will suggest what further optimization would need to be completed to meet lower emissions standards. Finally, this paper suggests some further research and questions to be answered in preparing and optimizing an aftertreatment system for a light-duty diesel engine.
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