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The increasing use of gasoline direct injection (GDI) engines coupled with the implementation of new particulate matter (PM) and particle number (PN) emissions regulations requires new emissions control strategies. Gasoline particulate filters (GPFs) present one approach to reduce particle emissions. Although primarily composed of combustible material which may be removed through oxidation, particle also contains incombustible components or ash. Over the service life of the filter the accumulation of ash causes an increase in exhaust backpressure, and limits the useful life of the GPF. This study utilized an accelerated aging system to generate elevated ash levels by injecting lubricant oil with the gasoline fuel into a burner system. GPFs were aged to a series of levels representing filter life up to 150,000 miles (240,000 km). The impact of ash on the filter pressure drop and on its sensitivity to soot accumulation was investigated at specific ash levels.

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.

Measurements of particulate matter (PM) from spark ignition (SI) engine exhaust using dilution tunnels will become more prevalent as emission standards are tightened. Hence, a study of the dilution process was undertaken in order to understand how various dilution related parameters affect the accuracy with which PM sizes and concentrations can be determined. A SI and a compression ignition (CI) engine were separately used to examine parameters of the dilution process; the present work discusses the results in the context of SI exhaust dilution. A Scanning Mobility Particle Sizer (SMPS) was used to measure the size distribution, number density, and volume fraction of PM. Temperature measurements in the exhaust pipe and dilution tunnel reveal the degree of mixing between exhaust and dilution air, the effect of flowrate on heat transfer from undiluted and diluted exhaust to the environment, and the minimum permissible dilution ratio for a maximum sample temperature of 52°C.

The Diesel Particulate Filter (DPF) system has been developed as one of key technologies to comply with tight diesel PM emission regulations. For the DPF control system, it is necessary to maintain temperature inside the DPF below the allowable service temperature, especially during soot regeneration to prevent catalyst deterioration and cracks. Therefore, the evaluation of soot regeneration is one of the key development items for the DPF system. On the other hand, regeneration evaluation requires a lot of time and cost since many different regeneration conditions should be investigated in order to simulate actual driving. The simulation tool to predict soot regeneration behavior is a powerful tool to accelerate the development of DPF design and safe regeneration control strategies. This paper describes the soot regeneration model applied to fuel additive and catalyzed types, and shows good correlation with measured data.

As emissions regulations are becoming more stringent, various efforts to improve emission performance have been carried out in different areas including the honeycomb structure of catalytic converters. This report describes the development of a simulation tool to predict emission performance and simulation results for different cell structures. The simulation model was developed based on global kinetic chemical reaction model [1]. Having tuned the reaction parameters through a light-off test and estimated oxygen storage capacity through an oxygen storage test, we ultimately tuned the model in a vehicle test (with Bags 1 and 2, FTP 75). As a result, the simulated cumulative tailpipe emissions are within ±25 percent of the test results. Parameter analyses indicate that the amount of emissions decreased as the density of cells increased and that the amount of emissions also decreased the thinner the wall thicknesses were.

Developing ultra thin wall ceramic substrates is necessary to meet stricter emissions regulations, in part because substrate cell walls need to be thinner in order to improve warm-up and light-off characteristics and lower exhaust system backpressure. However, the thinner the cell wall becomes, the poorer the mechanical and thermal characteristics of the substrate. Furthermore, the conditions under which the ultra thin wall substrates are used are becoming more severe. Therefore both the mechanical and thermal characteristics are becoming important parameters in the design of advanced converter systems. Whereas square cells are used world-wide in conjunction with oxidation and/or three-way catalysts, hexagonal cells, with features promoting a homogeneous catalyst coating layer, have found limited use as a NOx absorber due to its enhanced sulfur desorption capability.

To meet stringent emissions regulations, high conversion efficiency is required. This calls for advanced catalyst substrates with thinner walls and higher cell density. Higher cell density is needed because it brings higher mass transfer from the gas to the substrate wall. Basically, the increase in total surface area (TSA) causes higher mass transfer. However, not only the TSA, but the cell shape also has a great effect on mass transfer. There are two main kinds of substrates. One is the extruded ceramic substrate and the other is the metal foil type substrate. These have different cell shapes due to different manufacturing processes. For the extruded ceramic substrate, it is possible to fabricate various cell shapes such as triangle, hexagon, etc. as well as the square shape. The difference in the cell shape changes not only the mass transfer rate, but also causes pressure loss change. This is an important item to be considered in the substrate design.

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.

HC emission standards will be tightened during the 1990's in the US. A key issue in reducing HC emission is improving the warm-up characteristics of catalysts during the cold start of engines. For this purpose, studies are under way on reduction of heat mass of ceramic substrates. Reduction of cell walls in substrates to thickness smaller than the current thickness of 12mil or 6mil has resulted in reduced heat mass, and also reduced flow restriction of substrates. The warm-up characteristics of low bulk density catalysts are better than those of high bulk density, i.e., the warm-up characteristics of thinner wall or lower cell density catalysts are better than those of thicker wall or higher cell density catalysts. A relationship between geometric surface area and warm-up characteristics is observed.

Currently, states that are out of compliance with the National Ambient Air Quality Standards must, according to the Clean Air Act Amendments of 1990 (CAAA), develop and implement control strategies that demonstrate specific degrees of reduction in emissions-with the degree of reduction depending upon the severity of the problem. One tool that has been developed to aid regulators in both deciding an appropriate course of action and to demonstrate the desired reductions in mobile emissions is EPA's Mobile 5a emission estimation model. In our study, Mobile 5a has been used to examine the effects of regulatory strategies, as applied to the Northeast United States, on vehicle emissions under worst-case ozone-forming conditions.

In this study, to satisfy increasingly strict emission regulations, the conversion efficiency of a 0.11 mm (4 mil) thin-wall catalyst is discussed. The effects of catalyst bulk density on reducing heat mass to improve catalyst emission conversion in the early cold transient mode (Bag 1 in the FTP-75 mode) is quantitatively discussed. To analyze the effects of low heat mass, catalyst's bed temperatures were measured. Effects of the geometric surface area (GSA) and volume of the catalyst were also analyzed. An early feedback control system with an HEGO oxygen sensor and a secondary air injection control system with an original oxygen sensor were compared with an original control system on THC, CO, and NOx emission amounts.

This paper proposes a high temperature catalytic converter design using a ceramic substrate and intumescent matting. It also describes the improvement of converter performance using an advanced thin wall ceramic substrate. Due to future tightening of emission regulations and improvement of fuel economy, higher exhaust gas temperatures are suggested. Therefore, reduction of thermal reliability of an intumescent mat will be a concern because the catalytic converter will be exposed to high temperatures. For this reason, a new design converter has been developed using a dual cone structure for both the inlet and outlet cones. This minimizes heat conduction through the cone and decreases the temperature affecting the mat area. This design converter, without the use of a heat-shield, reduces the converter surface temperature to 441°C despite a catalyst bed temperature of 1050°C. The long term durability of the converter is demonstrated by the hot vibration test.

Catalytic performance can be improved by increasing geometric surface area (GSA) and reducing bulk density (BD), namely heat capacity, using high cell-density / thinwall advanced ceramic substrates. The advanced substrates, such as 3 mil/600 cpsi and 2 mil/900 cpsi have improved the catalytic performance over the conventional substrates, and are expected to help in complying with future emission regulations, as well as catalyst downsizing. This paper describes the effects of GSA and BD using Pd-based catalysts. The reduction of hydrocarbons emissions was demonstrated significantly at close-coupled location, and dual bed design was proven effective. The effectiveness at under-floor location was not as significant as the close-coupled location.

In order to meet the strict automobile emission regulations in the U.S.A. and Europe, new aftertreatment technologies such as the EHC and HC Adsorber have been developed to reduce the cold start emissions. The EHC is obviously effective in reducing emissions, but has the demerits of a large electric power demand and a complicated power control system to support it (13). A by-pass type HC adsorber system has the concerns of unreliable by-pass valves and complicated plumbing (10). A major technical challenge of the in-line type HC adsorber was the difference between the HC desorption temperature and the light-off temperature of the burn-off catalyst. This paper describes the evaluation results of a completely passive “In-line HC Adsorber System” which can reduce the cold start emissions without the application of any type of mechanical or pneumatic control valve in the exhaust system.

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.

Although air pollution has mitigated since the introduction of exhaust emission regulations, further reduction of it especially in the metropolitan areas is anticipated. An effective way to resolve this issue is to improve the catalyst performance. Of many approaches, improving substrate is one promising way to achieve this goal. Results of applying high cell density and light- weight substrates, coupled with high precious metal content, are discussed theoretically and verified experimentally here. The significant improvements made in the low temperature activity and warmed-up conversions by increasing geometrical surface areas and lowering thermal mass of high cell density substrates are described.

The Wankel rotary engine is more compact than conventional piston engines, but its oil and fuel consumption must be reduced to satisfy emission standards and customer expectations. A key step toward this goal is to develop a better understanding of the apex seal lubrication to reduce oil injection while reducing friction and maintaining adequate wear. This paper presents an apex seal dynamics model capable of estimating relative wear and predicting friction, by modeling the gas and oil flows at the seal interfaces with the rotor housing and groove flanks. Model predictions show that a thin oil film can reduce wear and friction, but to a limited extent as the apex seal running face profile is sharp due to the engine kinematics.

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.

Three-piece oil control rings (TPOCR) are widely used in the majority of modern gasoline engines and they are critical for lubricant regulation and friction reduction. Despite their omnipresence, the TPOCRs’ motion and sealing mechanisms are not well studied. With stricter emission standards, gasoline engines are required to maintain lower oil consumption limits, since particulate emissions are strongly correlated with lubricant oil emissions. This piqued our interest in building a numerical model coupling TPOCR dynamics and oil transport to explain the physical mechanisms. In this work, a 2D dynamics model of all three pieces of the ring is built as the main frame. Oil transport in different zones are coupled into the dynamics model. Specifically, two mass-conserved fluid sub-models predict the oil movement between rail liner interface and rail groove clearance to capture the potential oil leakage through TPOCR. The model is applied on a 2D laser induced fluorescence (2D-LIF) engine.

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.