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Heavy Duty Vehicle (HDV) Diesel emission regulations are set to be tightened in the future. The introduction of PN PEMS testing for Euro VI-e, and the expected tightening of PM/NOx targets set to be introduced by CARB in the US beyond 2024 are expected to create challenging tailpipe PN conditions for OEMs. Additionally, warranty and the useful life period will be extended from current levels. Improved fuel efficiency (reduction of CO2) also remains an important performance criteria. Furthermore, future non-road diesel emission regulations may follow tighten HDV diesel emission regulations contents, and non-road cycles evaluation needs to be considered as well for future. In response to the above tightened regulation, for Diesel Particulate Filter (DPF) technologies will require higher PN filtration performance, lower pressure drop, higher ash capacity and better pressure drop hysteresis for improved soot detectability.

Selective catalyst reduction (SCR) using cordierite honeycomb substrate is generally used as a DeNOx catalyst for diesel engines exhaust in both on-road and commercial off-highway vehicles to meet today’s worldwide emission regulations. Worldwide NOx emission regulations will become stricter, as represented by CARB2027 and EuroVII. Technologies which can achieve further lower NOx emissions are required. Recently, several technologies, like increased SCR catalyst loading amount on honeycomb substrates, and additional SCR catalyst volume in positions closer to the engine are being considered to achieve ultra-low NOx emissions. However, undesirable pressure drop increase and enlarging after treatment systems will be caused by adopting these technologies. Therefore, optimization of the material and honeycomb cell structure for SCR is inevitable to achieve ultra-low NOx emissions, while minimizing any system drawbacks.

With the push towards more stringent on-road US heavy duty diesel regulations (i.e. HD GHG Phase 2 and the proposed ARB 20 mg/bhp-hr NOx), emission system packaging has grown critical while improving fuel economy and NOx emissions. The ARB regulations are expected to be implemented post 2023 while regulation for EU off-road segment will begin from 2019. The regulation, called Stage V, will introduce particle number (PN) regulation requiring EU OEMs to introduce a diesel particulate filter (DPF) while customer demands will require the OEMs to maintain current emission system packaging. A viable market solution to meet these requirements, especially for EU Stage V being implemented first, is a DPF coated with a selective catalyst reduction (SCR) washcoat (i.e. SCRonDPF).

In order to meet the challenging CO2 targets beyond 2020 despite keeping high performance engines, Gasoline Direct Injection (GDI) technology usually combined with charged aspiration is expanding in the automotive industry. While providing more efficient powertrains to reduce fuel consumption one side effect of GDI is the increased particle formation during the combustion process. For the first time for GDI from September 2014 there is a Particle Number (PN) limit in EU of 6x10 sup 12 #/km, which will be further reduced by one order of magnitude to 6x10 sup 11 #/km effective from September 2017 to be the same level as applied to Diesel engines. In addition to the PN limit of the certification cycle NEDC further certification of Real Driving Emissions (RDE) including portable PN measurements are under discussion by the European Commission. RDE test procedure requires stable and low emissions in a wide range of engine operations and durable over a distance of 160 000 km.

Ammonia Selective Catalytic Reduction (SCR) is adapted for a variety of applications to control nitrogen oxides (NOx) in diesel engine exhaust. The most commonly used catalyst for SCR in established markets is Cu-Zeolite (CuZ) due to excellent NOx conversion and thermal durability. However, most applications in emerging markets and certain applications in established markets utilize vanadia SCR. The operating temperature is typically maintained below 550°C to avoid vanadium sublimation due to active regeneration of the diesel particulate filter (DPF), or some OEMs may eliminate the DPF because they can achieve particulate matter (PM) standard with engine tuning. Further improvement of vanadia SCR durability and NOx conversion at low exhaust gas temperatures will be required in consideration of future emission standards.

Ammonia Selective Catalytic Reduction (SCR) is a key emission control component utilized in diesel engine applications for NOx reduction. There are several types of SCR catalyst currently in the market: Cu-Zeolite, Fe-Zeolite and Vanadia. Diesel vehicle and engine manufacturers down select their production SCR catalyst primarily based on vehicle exhaust gas temperature operation, ammonia dosing strategy, fuel quality, packaging envelope and cost. For Vanadia SCR, the operating temperature is normally controlled below 550oC to avoid vanadium sublimation. In emerging markets, the Vanadia SCR is typically installed alone or downstream of the DOC with low exhaust gas temperature exposure. Vanadia SCR is also utilized in some European applications with passive DPF soot regeneration. However, further improvement of Vanadia SCR NOx conversion at low exhaust gas temperatures will be required to meet future emission regulations (i.e.: HDD Phase 2 GHG).

Diesel engines are widely used to reduce CO2 emission due to its higher thermal efficiency over gasoline engines. Considering long term CO2 targets, as well as tighter gas emission, especially NOx, diesel engines must become cleaner and more efficient. However, there is a tradeoff between CO2 and NOx and, naturally, engine developers choose lower CO2 because NOx can be reduced by a catalytic converter, such as a SCR catalyst. Lower CO2 engine calibration, unfortunately, leads to lower exhaust gas temperatures, which delays the activation of the catalytic converter. In order to overcome both problems, higher engine out NOx emission and lower exhaust gas temperatures, close-coupled a diesel particulate filter (DPF) system with integration of SCR catalyst technology is preferred. For SCR catalyst activity, it is known that the catalyst loading amount has an influence on NOx performance, so a high SCR catalyst loading will be required.

Since the implementation of Euro 6 in September 2014, diesel engines are facing another drastic reduction of NOx emission limits from 180 to only 80 mg/km during NEDC and real driving emissions (RDE) are going to be monitored until limit values are enforced from September 2017. Considering also long term CO2 targets of 95 g/km beyond 2020, diesel engines must become cleaner and more efficient. However, there is a tradeoff between NOx and CO2 and, naturally, engine developers choose lower CO2 because NOx can be reduced by additional devices such as EGR or a catalytic converter. Lower CO2 engine calibration, unfortunately, leads to lower exhaust gas temperatures, which delays the activation of the catalytic converter. In order to overcome both problems, higher NOx engine out emission and lower exhaust gas temperatures, new aftertreatment systems will incorporate close-coupled DeNOx systems.

A Particle Number (PN) limit for Gasoline Direct Injection (GDI) vehicles was introduced in Europe from September 2014 (Euro 6b). In addition, further certification to Real Driving Emissions (RDE) is planned [1] [2], which requires low and stable emissions in a wide range of engine operation, which must be durable for at least 160,000 km. To achieve such stringent targets, a ceramic wall-flow Gasoline Particulate Filter (GPF) is one potential emission control device. This paper focuses on a catalyzed GPF, combining particle trapping and catalytic conversion into a single device. The main parameters to be considered when introducing this technology are filtration efficiency, pressure drop and catalytic conversion. This paper portrays a detailed study starting from the choice of material recipe, design optimization, engine bench evaluation, and final validation inside a standard vehicle from the market during an extensive field test up to 160,000 km on public roads.

Today the Ammonia Selective Catalytic Reduction (SCR) system with good NOx conversion is the emission technology of choice for diesel engines globally. High NOx conversion SCR systems combined with optimized engine calibration not only address the stringent NOx emission limits which have been introduced or are being considered for later this decade, but also reduce CO2 emissions required by government regulations and the increase in fuel economy required by end-users. Reducing the packaging envelope of today's SCR systems, while retaining or improving NOx conversion and pressure drop, is a key customer demand. High SCR loadings ensure high NOx conversion at very low temperatures. To meet this performance requirement, a High Porosity Substrate which minimizes the pressure drop impact, was introduced in SAE Paper 2012-01-1079 [1], [2], [3].

Low fuel consumption and improved power output are the main market drivers in the automotive industry. For these challenges, Gasoline Direct Injection (GDI) technology provides higher thermal efficiency than Multi Point Injection (MPI) engines and this technology is expanding as a solution to reduce CO₂ and improve driveability. In Europe under the Euro 5 regulation, engine downsizing becomes a major solution to reduce CO₂ of gasoline engines. For this concept GDI is essential together with turbocharging technology. However GDI technology increases particulate matter (PM) emissions compared to MPI engines. As the introduction of a Particle Number (PN) regulation for Euro 6 GDI vehicles has been decided, technologies to reduce GDI PN emissions start to become necessary. For this requirement, a gasoline particulate filter (GPF) is an effective solution.

Diesel particulate filters (DPF) are a common component in emission-control systems of modern clean diesel vehicles. Several DPF materials have been used in various applications. Silicone Carbide (SiC) is common for passenger vehicles because of its thermal robustness derived from its high specific gravity and heat conductivity. However, a segmented structure is required to relieve thermal stress due to SiC's higher coefficient of thermal expansion (CTE). Cordierite (Cd) is a popular material for heavy-duty vehicles. Cordierite which has less mass per given volume, exhibits superior light-off performance, and is also adequate for use in larger monolith structures, due to its lower CTE. SiC and cordierite are recognized as the most prevalent DPF materials since the 2000's. The DPF traps not only combustible particles (soot) but also incombustible ash. Ash accumulates in the DPF and remains in the filter until being physically removed.

The automotive industry is currently evaluating the gasoline particulate filter (GPF) as a potential technology to reduce particulate emissions from gasoline direct injection (GDI) engines. In this paper, several GPF design measures which were taken to obtain a filter with lower pressure drop when compared to our previous concept will be presented. Based on engine test bench and vehicle test results, it was determined some soot will accumulate on the GPF walls, resulting in an increase in pressure drop. However, the accumulated soot will be combusted under high temperature and high O₂ concentration conditions. In a typical vehicle application, passive regeneration will likely occur and a cycle of soot accumulation and combustion might be repeated in the actual driving conditions.

Diesel engines are more fuel efficient due to their high thermal efficiency, compared to gasoline engines and therefore, have a higher potential to reduce CO2 emissions. Since diesel engines emit higher amounts of Particulate Matter (PM), DPF systems have been introduced. Today, DPF systems have become a standard technology. Nevertheless, with more stringent NOx emission limits and CO2 targets, additional NOx emission control is needed. For high NOx conversion efficiency, SCR catalysts technology shows high potential. Due to higher temperature at the close coupled position and space restrictions, an integrated SCR concept on the DPFs is preferred. A high SCR catalyst loading will be required to have high conversion efficiency over a wide range of engine operations which causes high pressure for conventional DPF materials.

Ammonia Selective Catalytic Reduction (SCR) and Lean NOx Trap (LNT) systems are key technologies to reduce NOx emission for diesel on-highway vehicles to meet worldwide tighter emission regulations. In addition DeNOx catalysts have already been applied to several commercial off-road applications. Adding the DeNOx catalyst to existing Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF) emission control system requires additional space and will result in an increase of emission system back pressure. Therefore it is necessary to address optimizing the DeNOx catalyst in regards to back pressure and downsizing. Recently, extruded zeolite for DeNOx application has been considered. This technology improves NOx conversion at low temperature due to the high catalyst amount. However, this technology has concerned about strength and robustness, because the honeycomb body is composed of catalyst.

Gasoline Direct Injection (GDI) engines achieve better fuel economy but have the drawback of increased Particulate Matter (PM) emissions. As known from diesel engine applications particulate filters are an effective PM reduction device which is expected to be effective for reduction of particulates emitted by GDI engines as well. For this investigation new filter concepts especially designed for GDI applications are proposed. Filtration efficiency, pressure drop and regeneration performance were verified by cold flow bench and engine and chassis dynamometer testing. The experimental data were used to discuss the validity of these new filter design concepts.

A numerical study was carried out to determine the relative impact of diesel engine after-treatment system placement on engine performance. The objective of the study was to investigate the advantages and disadvantages of placing the after-treatment system upstream of the turbocharger as opposed to the more conventional downstream location. The study was conducted under both steady state and transient operating conditions. The after-treatment system involved in this study consisted of a Diesel Oxidation Catalyst (DOC) followed by a Diesel Particulate Filter (DPF) directly downstream of the former. The DOC and DPF models were correlated with experimentally-obtained, individual, pressure drop and warm-up data sets for each device. In an additional step for transient studies, chemical reactions were modeled within the DOC to simulate HC and CO oxidation, and their associated exothermic behavior.

Due to its better fuel efficiency and low CO2 emissions, the number of diesel engine vehicles is increasing worldwide. Since they have high Particulate Matter (PM) emissions, tighter emission regulations will be enforced in Europe, the US, and Japan over the coming years. The Diesel Particulate Filter (DPF) has made it possible to meet the tighter regulations and Silicon Carbide and Cordierite DPF's have been applied to various vehicles from passenger cars to heavy-duty trucks. However, it has been reported that nano-size PM has a harmful effect on human health. Therefore, it is desirable that PM regulations should be tightened. This paper will describe the influence of the DPF material characteristics on PM filtration efficiency and emissions levels, in addition to pressure drop.

This paper is Part-1 of two papers discussing the filtration behavior of diesel particulate filters. Results of the fundamental study are presented in Part-1, and test results for real size DPFs are reported in the supplement, Part-2. In this paper, a fundamental experimental study was performed on the effect of pore size and pore size distribution on the PM filtration efficiency of the ceramic, wall-flow Diesel Particulate Filter (DPF). Small round plates of various average mean pore sizes (4.6, 9.4, 11.7, 17.7 micro-meters) with a narrow pore size distribution were manufactured for the tests. During the DPF filtration efficiency tests, ZnCl2 particles in the range of 10 nm to 500 nm were used instead of PM from actual diesel engine exhaust. ZnCl2 particles were made using an infrared furnace and separated into monodisperse particles by DMA (Differential Mobility Analyzer).

The application of Diesel Particulate Filters (DPF's) is expanding in the European, Japanese and US markets to comply with the tighter PM regulations. SiC DPF's, featuring greater robustness, have been applied extensively to passenger cars and are expanding into larger sizes for Light Duty Trucks applications. The SiC-DPF has higher mechanical strength when compared to other materials, such as Cordierite. However, SiC's thermal expansion ratio is greater. Therefore, the SiC-DPF is designed with 35 X 35mm segments and cement bonded construction, both of which function to relieve thermal stress. The appearance of the SiC-DPF with the segment design is shown in Figure 1. In this paper, the thermal stress mechanism of the segmented joint during soot regeneration and the influence of the cement properties on the thermal shock resistance was investigated by using the soot regeneration model and thermal stress analysis in addition to the engine test.