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The development of hydrogen-fueled vehicles has created the need for established fuel consumption testing methods. Until now the EPA has only accepted three methods of hydrogen fuel consumption testing, gravimetric, PVT (stabilized pressure, volume and temperature), and Coriolis mass flow; all of which necessitate physical measurements of the fuel supply [1]. BMW has developed an equation and subsequent testing methods to accurately and effectively determine hydrogen fuel consumption in light-duty vehicles using only exhaust emissions. Known as “Hydrogen-Balance”, the new equation requires no changes to EPA procedures and only slight modifications to most existing chassis dynamometers and CVS (Constant Volume Sampling) systems. The SAE 2008-01-1036, also written by BMW, explains the background as well as required equipment and changes to the CVS testing system. This paper takes hydrogen balance further by testing it against the three EPA established forms of fuel consumption.

The Hydrogen-Balance equation makes it possible to calculate the fuel economy or fuel consumption of hydrogen powered vehicles simply by analyzing exhaust emissions. While the benefits of such a method are apparent, it is important to discuss possible influencing factors that may decrease Hydrogen-Balance accuracy. Measuring vehicle exhaust emissions is done with a CVS (Constant Volume Sampling) system. While the CVS system has proven itself both robust and precise over the years, utilizing it for hydrogen applications requires extra caution to retain measurement accuracy. Consideration should be given to all testing equipment, as well as the vehicle being tested. Certain environmental factors may also play a role not just in Hydrogen-Balance accuracy, but as also in other low emission testing accuracy.

The reduction of vehicle exhaust particle emissions is a success story of European legislation. Various particle number (PN) counters and calibration procedures serve as tools to enforce PN emission limits during vehicle type approval (VTA) or periodical technical inspection (PTI) of in-use vehicles. Although all devices and procedures apply to the same PN-metric, they were developed for different purposes, by different stakeholder groups and for different target costs and technical scopes. Furthermore, their calibration procedures were independently defined by different stakeholder communities. This frequently leads to comparability and interpretation issues. Systematic differences of stationary and mobile PN counters (PN-PEMS) are well-documented. New, low-cost PTI PN counters will aggravate this problem. Today, tools to directly compare different instruments are scarce.

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.

To meet LEV and EU Stage III emission requirements, it is necessary for new catalytic converters to be designed which exceed light-off temperature as quickly as possible. The technical solutions are secondary air injection, active heating systems such as the electrically heated catalytic converter, and the close coupled catalytic converter. Engine control functions are extensively used to heat the converter and will to play a significant role in the future. The concept of relocating the converter to a position close to the engine in an existing vehicle involves new conflicts. Examples include the space requirements, the thermal resistance of the catalytic coating and high temperature loads in the engine compartment.

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).

Although hydrogen ICE engines have existed in one sort or another for many years, the testing of fuel consumption by way of exhaust emissions is not yet a proven method. The current consumption method for gasoline- and diesel-fueled vehicles is called the Carbon-Balance method, and it works by testing the vehicle exhaust for all carbon-containing components. Through conservation of mass, the carbon that comes out as exhaust must have gone in as fuel. Just like the Carbon-Balance method for gas and diesel engines, the new Hydrogen-Balance equation works on the principle that what goes into the engine must come out as exhaust components. This allows for fuel consumption measurements without direct contact with the fuel. This means increased accuracy and simplicity. This new method requires some modifications to the testing procedures and CVS (Constant Volume Sampling) system.

The study of oil emission is of essential interest for the engine development of modern cars, as well as for the understanding of hydrocarbon emissions especially during cold start conditions. A laser mass spectrometer has been used to measure single aromatic hydrocarbons in unconditioned exhaust gas of a H2-fueled engine at stationary and transient motor operation. These compounds represent unburned oil constituents. The measurements were accompanied by FID and GC-FID measurements of hydrocarbons which represent the burned oil constituents. The total oil consumption has been determined by measuring the oil sampled by freezing and weighing. It has been concluded that only 10 % of the oil consumption via exhaust gas has burned in the cylinders. A correlation of the emission of single oil-based components at ppb level detected with the laser mass spectrometer to the total motor oil emission has been found.

The objective of this paper is to study the parameters affecting the evolution of “uncontrolled” regeneration in diesel particulate filters with fuel-borne catalyst (FBC) support with emphasis on the development of thermal stresses critical for filter durability. The study is based on experiments performed on engine dynamometer, corresponding to “worst-case” scenario, as well as on advanced, multi-dimensional mathematical modeling. A new 2-dimensional mathematical model is presented which introduces an additional dimension across the soot layer and wall. With this dimension it is possible to take into account the variability of catalyst/soot ratio in the layer and to compute intra-layer composition gradients. The latter are important since they induce interesting O2 diffusion phenomena, which affect the regeneration evolution.

The objective of this study is to explain the physical and chemical mechanisms involved in the operation of a catalyzed diesel particulate filter. The study emphasizes on the coupling between reaction and diffusion phenomena (with emphasis on NO2 “back-diffusion”), based on modeling and experimental data obtained on the engine dynamometer. The study is facilitated by a novel multi-dimensional mathematical model able to predict both reaction and diffusion phenomena in the filter channels and through the soot layer and wall. The model is thus able to predict the species concentration gradients in the inlet/outlet channels, in the soot layer and wall, taking into account the effect of NO2 back diffusion. The model is validated versus engine dyno measurements. Two sets of measurements are employed corresponding to low-temperature “controlled” regenerations as well as high-temperature “uncontrolled” conditions.

Modern filter systems allow a significant reduction of diesel particulate emissions. The new silicon bonded silicon carbide particulate filters (Si-SiC filters) play an important role in this application, because they provide flexibility in terms of mean pore size and porosity and also have a high thermal shock capability to meet both engineering targets and emission limits for 2005 and beyond. Particulate filters are exposed to high temperatures and a harsh chemical environment in the exhaust gas of diesel vehicles. This paper will present further durability evaluation results of the new Si bonded SiC particulate filters which have been collected in engine bench tests and vehicle durability runs. The Si-SiC filters passed both 100 and 200 regeneration cycles under severe ageing conditions and without any problems. The used filters were subjected to a variety of analytical tests. The back pressure and ash distribution were determined. The filter material was also analysed.

The future emission limits for gasoline fuelled passenger cars require more and more efficient exhaust gas aftertreatment devices - the catalytic converter being one essential part of the complex system design. The present paper summarizes the results of several basic research programs putting major emphasis on the application of highly sophisticated three-way catalyst technologies being taylored for the utilization on ultra thin-wall ceramic substrates. In the first part of the investigation the following effects were examined in detail: Different washcoat loadings at constant PGM-loadings Different volumes of catalysts for constant amounts of PGM and washcoat Similar washcoat technologies at different ratios of WC-loading to precious metal concentration in the washcoat.

Changing of emission levels leads to an increasing demand for a satisfying solution to measure mass emissions of motor vehicles on both, engine and chassis dynamometers. Partial flow systems may fit to the demands. These systems require an exact determination of exhaust volume flow and time aligned concentration measurement. This paper will address these issues and problems related with partial flow sampling. Several exhaust flow measurement systems have been studied and integrated mass results have been checked against the full flow CVS. As the investigations indicate, modal mass calculation from sampling direct exhaust at the end of tailpipe is feasible but not a satisfying solution in equivalency and repeatability in comparison to CVS-results. This is especially the case on emission levels near or below ULEV.

Flame Ionization Detectors (FID) can be used to detect organic hydrocarbons that occur in plastics, lacquers, adhesives, solvents and gasoline. These substances are ionized in the hydrogen flame of the FID. The ionization current that is produced depends on the amount of hydrocarbon in the sample. With the lowering of emissions limits, measuring instruments, including the FID, have to be able to detect very low values. For SULEV (Super-Ultra Low Emissions Vehicle) measurements the accuracy and also the general applicability of the CVS (Constant Volume Sampling) measuring technique are now questioned. Basic understanding is necessary to ask the right questions. One important issue is the science behind the measurement principle of the FID. And in this case especially the influence of contamination of the operating gases, cross sensitivity and data processing on the Limit of Detection (LOD).

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.

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.

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.

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.

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.