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Four-way, integrated, diesel emission control systems that combine selective catalytic reduction for NOx control with a continuously regenerating trap to remove diesel particulate matter were evaluated under real-world, on-road conditions. Tests were conducted using a semi-tractor with an emissions year 2000, 6-cylinder, 12 L, Volvo engine rated at 287 kW at 1800 rpm and 1964 N-m. The emission control system was certified for retrofit application on-highway trucks, model years 1994 through 2002, with 4-stroke, 186-373 kW (250-500 hp) heavy-duty diesel engines without exhaust gas recirculation. The evaluations were unique because the mobile laboratory platform enabled evaluation under real-world exhaust plume dilution conditions as opposed to laboratory dilution conditions. Real-time plume measurements for NOx, particle number concentration and size distribution were made and emission control performance was evaluated on-road.

Gasoline Homogeneous Charge Compression Ignition (HCCI) combustion has been studied widely in the past decade. However, in HCCI engines using negative valve overlap (NVO), there is still uncertainty as to whether the effect of pilot injection during NVO on the start of combustion is primarily due to heat release of the pilot fuel during NVO or whether it is due to pilot fuel reformation. This paper presents data taken on a 4-cylinder gasoline direct injection, spark ignition/HCCI engine with a dual cam system, capable of recompressing residual gas. Engine in-cylinder samples are extracted at various points during the engine cycle through a high-speed sampling system and directly analysed with a gas chromatograph and flame ionisation detector. Engine parameter sweeps are performed for different pilot injection timings and quantities at a medium load point.

In HCCI engines, the Air/Fuel Ratio (AFR) and Residual Gas Fraction (RGF) are difficult to control during the SI-HCCI-SI transition, and this may result in incomplete combustion and/or high pressure raise rates. As a result, there may be undesirably high engine load fluctuations. The objectives of this work are to further understand this process and develop control methods to minimize these load fluctuations. This paper presents data on instantaneous AFR and RGF measurements, both taken by novel experimental techniques. The data provides an insight into the cyclic AFR and RGF fluctuations during the switch. These results suggest that the relatively slow change in the intake Manifold Air Pressure (MAP) and actuation time of the Variable Valve Timing (VVT) are the main causes of undesired AFR and RGF fluctuations, and hence an unacceptable Net IMEP (NIMEP) fluctuation. We also found large cylinder-to-cylinder AFR variations during the transition.

A Stochastic Reactor Model (SRM) has been used to simulate the transition from Spark Ignition (SI) mode to Homogeneous Charge Compression Ignition (HCCI) mode in a four cylinder in-line four-stroke naturally aspirated direct injection SI engine with cam profile switching. The SRM is coupled with GT-Power, a one-dimensional engine simulation tool used for modelling engine breathing during the open valve portion of the engine cycle, enabling multi-cycle simulations. The model is initially calibrated in both modes using steady state data from SI and HCCI operation. The mode change is achieved by switching the cam profiles and phasing, resulting in a Negative Valve Overlap (NVO), opening the throttle, advancing the spark timing and reducing the fuel mass as well as utilising a pilot injection. Experimental data is presented along with the simulation results.

A 1.9 liter Volkswagen TDI engine has been modified to accomodate the addition of hydrogen into the intake manifold via timed port fuel injection. Engine out particulate matter and the emissions of oxides of nitrogen were investigated. Two fuels,low sulfur diesel fuel (BP50) and soy methyl ester (SME) biodiesel (B99), were tested with supplemental hydrogen fueling. Three test conditions were selected to represent a range of engine operating modes. The tests were executed at 20, 40, and 60 % rated load with a constant engine speed o 1700 RPM. At each test condition the percentage of power from hydrogen energy was varied from 0 to 40 %. This corresponds to hydrogen flow rates ranging from 7 to 85 liters per minute. Particulate matter (PM) emissions were measured using a scaning mobility particle sizer (SMPS) and a two stage micro dilution system. Oxides of nitrogen were also monitored.

The use of a corona-less electrostatic precipitator as a collection and agglomeration device for diesel soot has been investigated. It collects and grows diesel particles which are emitted in the submicron diameter range and grow into much larger particles. These larger particles may then be collected with a relatively simple inertial device. Previous testing of a full scale precipitator designed for a Caterpillar 3304 engine showed that the reduction in sub-micron sized mass from the engine was roughly 30 to 40%. Greater reductions were desired. A sub-scale electrostatic agglomerator was built to analyze in greater detail the behavior of an existing full scale device. Tests were designed to determine; the charged fraction of the particles from the engine used, the collection efficiency of the electrostatic agglomerator, the effect of geometry on collection efficiency, and the size distribution of the particles reentrained after electrostatic collection.

A study of the sources of variability in particulate measurements using the Heavy-Duty Transient Test (40 CFR Subpart N) has been conducted. It consisted of several phases: a critical examination of the test procedures, visits to representative facilities to compare and contrast facility designs and test procedures, and development of a simplified model of the systems and procedures used for the Heavy-Duty Transient Test. Some of the sources of variability include; thermophoretic deposition of particulate matter onto walls of the sampling system followed by subsequent reentrainment in an unpredictable manner, the influence of dilution and cooling upon the soluble organic fraction, inconsistency among laboratories in the engine and dynamometer control strategies, and errors in measurements of flows into and out of the secondary dilution tunnel.

Soot is the largest component of contaminants found in the diesel engine lubricating oil. The soot enters lubricating oil mainly through thermophoretic deposition on the cylinder wall. Although the mechanism is still not fully understood, it is generally accepted that soot particles promote engine wear, reducing engine component service life, fuel efficiency and performance. This problem will be further exacerbated when more and more diesel engines use EGR to reduce NOx emissions and when lubricating oil consumption is drastically reduced to control particulate emissions. In this study, lubricating oil samples were taken from 7 different operating diesel engines. The size distribution and concentration of the diesel soot particles in the lubricants were investigated by methods of photosedimentation and quantitative spectrophotometry. The size distributions were compared to those of soot particles in the exhaust.

The flow and heat transfer phenomena in the intake port of a spark ignition engine with port fuel injection play a significant role in the mixture preparation process, especially at part load. The backflow of the hot burned gas from the cylinder into the intake port when the intake valve is opened breaks up any liquid film around the inlet valve, influences gas and wall temperatures, and has a major effect on the fuel vaporization process. The backflow of in-cylinder mixture with its residual component during the compression stroke prior to inlet valve closing fills part of the port with gas at higher than fresh mixture temperature. To quantify these phenomena, time-resolved measurements of the hydrocarbon concentration profile along the center-line of the intake port were made with a fast-response flame ionization detector, and of the gas temperature with a fine wire resistance thermometer, in a single-cylinder engine running with premixed propane/air mixture.

Recent studies in the USA have revealed that the catalysts (which are universally fitted to gasoline automobiles) are failing in service to an unacceptable extent. Although the reasons for the failures are not completely clear, it seems that misfiring, leading to highly exothermic reaction in the catalyst, may be responsible for the damage. Legislation is to be enacted later in this decade to address this problem by requiring on board diagnostic (OBD) systems which can measure misfire, as well as catalyst hydrocarbon (HC) conversion efficiency. Although some ideas have been suggested for the OBD requirements, no fully satisfactory sensor technology has yet appeared. This paper describes a novel hydrocarbon sensor based on a surface catalysis principle. The fundamental studies reported here have been made with the automobile application in mind. A catalytic chemi-ionisation model is proposed in order to enhance our understanding of this surface ionisation.

Partially premixed compression ignition (PPCI) engines operating with a low temperature highly homogeneous charge have been demonstrated previously using conventional diesel fuel. The short ignition delay of conventional diesel fuel requires high fuel injection pressures to achieve adequate premixing along with high levels of EGR (exhaust gas recirculation) to achieve low NOx emissions. Low load operating regions are typified by substantial emissions of CO and HC and there exists an upper operating load limitation due to very high rates of in-cylinder gas pressure rise. In this study mixtures of gasoline and diesel fuel were investigated using a multi-cylinder light duty diesel engine. It was found that an increased proportion of gasoline fuel reduced smoke emissions at higher operating loads through an increase in charge premixing resulting from an increase in ignition delay and higher fuel volatility.

Highly homogeneous compression ignition is difficult to achieve in a direct injection diesel engine. The difficulty of achieving adequate fuel vaporization and the problems of fuel spray wall impingement are the main factors. Limitation of the maximum operating load results from high rates of pressure rise that occur in this combustion regime. The levels of HC and CO emissions are raised substantially when compared with conventional combustion and remain a significant emission factor. In this study, two methods of achieving highly homogeneous combustion in a direct injection diesel engine were investigated, Nissan MK type and early injection. The effects of fuel injection pressure, injection timing, EGR level, EGR cooler efficiency and compression ratio were examined using a conventional 4 cylinder 2.0L common rail diesel engine with 18.4:1 and 14.4:1 compression ratios.

A new fast response NO detector, based on the chemiluminescence (CLD) method has been used to measure continuous, real time levels of NO in the cylinder, and simultaneously in the exhaust port of a virtually unmodified production SI engine. The real time NO concentration data show a great deal of information. Simultaneous NO measurements taken in-cylinder at sample points a few millimetres apart show substantial differences. Exhaust and in-cylinder levels from the same cycle show even greater differences, though the levels on average are well correlated.

A novel Fast Response Chemiluminescence Detector and a Fast Flame Ionization detector have been used to examine the instantaneous NO and unburnt hydrocarbon concentration in the cylinder and exhaust port of a DI Diesel engine. The in-cylinder results indicate very high levels of NO in the premixed phase of combustion, followed by generally lower levels during the diffusion burning phase. Hydrocarbon signals also indicate significant detail. The in-cylinder uHC signal is consistent with the probe location being between two of the fuel sprays. Both in-cylinder and exhaust results indicate rather high cyclic variability in the NO levels at steady conditions. Variations in the timing and structure of the exhaust uHC signal during the valve open period with load may give insight into the fuel spray/air motion.

A novel mechanical method of achieving a rapid switch between stoichiometric and lean conditions for SI engines is explored. Two and three throttle configurations, a switch strategy which employs a standard intake manifold and an assembly of pipes and throttle(s), are investigated numerically by using a one-dimensional engine simulation program based on the method of characteristics. The results indicate that it is possible to achieve rapid AFR switch without a torque jump, i.e. unperceptible to the driver.

A major problem with many soot emission control devices is the fact that they quickly become loaded with soot which must be removed by a controlled burning (regeneration) process. The need for regeneration greatly complicates such diesel particle emission control devices. In this paper, an electrostatic agglomerator (ESA) which efficiently collects diesel particles but does not require regeneration is described. The ESA is an electrostatic precipitator which is designed to collect and subsequently reentrain diesel soot particles. The collection and reentrainment processes results in growth of particle diameter from roughly 0.2 μm to larger than 1.0 μm. The agglomerated particles are large enough to be collected by a relatively simple inertial device, e.g., a cyclone separator. The collected particle may be either recycled to the engine or disposed of by other means. Electrostatic collection is made easier by the fact that diesel particles are charged by the combustion process itself.

There is a growing body of evidence that in-cylinder surfaces play an important role in determining the nature and quantity of soot emitted by diesel engines. This paper describes recent experimental results which demonstrate the importance of both the deposition of soot on walls during the combustion process and its subsequent reentrainment during exhaust blowdown. Soot deposition was demonstrated both experimentally and theoretically. The principal mechanism of soot deposition during combustion is thermophoresis. Our results suggest that the gross rate of in-cylinder deposition in the indirect injection diesel engine is between 20 and 45 percent of the net soot emission rate. Thus, a significant fraction of the soot emitted may have been stored on combustion chamber surfaces and protected from oxidation. Further evidence of wall deposition and subsequent reentrainment has been obtained by making time-resolved measurements of soot concentrations in the exhaust.

The effects of fuel sulfur content and dilution conditions on diesel engine PM number emissions have been researched extensively through steady state testing. Most results show that the concentration of nuclei-mode particles emitted increases with fuel sulfur content. A few studies further observed that fuel sulfur content has little effect on the emissions of heavily-used engines. It has also been found that primary dilution conditions can have a large impact on the size and number distribution of the nuclei-mode particles. These effects, however, have not yet been fully understood through transient testing, the method used by governments worldwide to certify engines and regulate emissions, and a means of experimentation which generates realistic conditions of on-road vehicles by varying the load and speed of the engine.

Particle concentrations and size distributions were measured in the exhaust of a turbocharged, aftercooled, direct-injection, Diesel engine equipped with a ceramic filter (trap). Measurements were performed both upstream and downstream of the filter using a two-stage, variable residence time, micro-dilution system, a condensation particle counter and a scanning mobility particle sizer set up to count and size particles in the 7-320 nm diameter range. Engine operating conditions of the ISO 11 Mode test were used. The engine out (upstream of filter) size distribution has a bimodal, log normal structure, consisting of a nuclei mode with a geometric number mean diameter, DGN, in the 10-30 nm range and an accumulation mode with DGN in the 50-80 nm range. The modal structure of the size distribution is less distinct downstream of the filter. Nearly all the particle number emissions come from the nuclei mode, are nanoparticles (Dp < 50nm), and are volatile.

An established Stochastic Reactor Model (SRM) is used to simulate the transition from Spark Ignition (SI) to Homogeneous Charge Compression Ignition (HCCI) combustion mode in a four-cylinder in-line four-stroke naturally aspirated direct injection SI engine with cam profile switching. The SRM is coupled with GT-Power, a one-dimensional engine simulation tool used for modeling engine breathing during the open valve portion of the engine cycle, enabling multi-cycle simulations. The mode change is achieved by switching the cam profiles and phasing, resulting in a Negative Valve Overlap (NVO), opening the throttle, advancing the spark timing and reducing the fuel mass as well as using a pilot injection. A proven technique for tabulating the model is used to create look-up tables in both SI and HCCI modes. In HCCI mode several tables are required, including tables for the first NVO, transient valve timing NVO, transient valve timing HCCI and steady valve timing HCCI and NVO.