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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.

Ethanol, used widely as a spark-ignition (SI) engine fuel, has seen minimal success as a compression ignition (CI) engine fuel. The lack of success of ethanol in CI engines is mainly due to ethanol's very low cetane number and its poor lubricity properties. Past researchers have utilized nearly pure ethanol in a CI engine by either increasing the compression ratio which requires extensive engine modification and/or using an expensive ignition improver. The objective of this work was to demonstrate the ability of a hydrogen port fuel injection (PFI) system to facilitate the combustion of ethanol in a CI engine. Non-denatured anhydrous ethanol, mixed with a lubricity additive, was used in a variable compression ratio CI engine. Testing was conducted by varying the amount of bottled hydrogen gas injected into the intake manifold via a PFI system. The hydrogen flowrates were varied from 0 - 10 slpm.

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.

Diesel exhaust particle number concentrations and size distributions, as well as gaseous and particulate mass emissions, were measured during steady-state tests on a US heavy-duty engine and a European passenger car engine. Two fuels were compared, namely a Fischer-Tropsch diesel fuel manufactured from natural gas, and a US D2 on-highway diesel fuel. With both engines, the Fischer-Tropsch fuel showed a considerable reduction in the number of particles formed by nucleation, when compared with the D2 fuel. At most test modes, particle number emissions were dominated by nucleation mode particles. Consequently, there were generally large reductions (up to 93%) in the total particle number emissions with the Fischer-Tropsch fuel. It is thought that the most probable cause for the reduction in nucleation mode particles is the negligible sulphur content of the Fischer-Tropsch fuel. In general, there were also reductions in all the regulated emissions with the Fischer-Tropsch fuel.

A one-stage dilution tunnel has been developed to sample and dilute diesel exhaust. The tunnel has the capability of simulating many aspects of the atmospheric dilution process. The dilution rate and overall dilution ratio, temperature, relative humidity, and residence time in the tunnel, as well as residence time and temperature in the transfer line between the tunnel and exhaust sampling point may be varied. In this work we studied the influence of the exhaust transfer line, tunnel residence time, and dilution air temperature on the exhaust particle size distribution. The influences of fuel sulfur content on the size distribution and on the sensitivity of the size distribution to dilution and sampling conditions were also examined. We do not suggest an optimum dilution scheme, but do identify critical variables.

Nanoparticle formation during exhaust sampling and dilution has been examined using a two-stage micro-dilution system to sample the exhaust from a modern, medium-duty diesel engine. Growth rates of nanoparticles at different exhaust dilution ratios and temperatures have been determined by monitoring the evolution of particle size distributions in the first stage of the dilution system. Two methods, graphical and analytical, are described to determine particle growth rate. Extrapolation of size distribution down to 1 nm in diameter has been demonstrated using the graphical method. The average growth rate of nanoparticles is calculated using the analytical method. The growth rate ranges from 6 nm/sec to 24 nm/sec, except at a dilution ratio of 40 and primary dilution temperature of 48 °C where the growth rate drops to 2 nm /sec. This condition seems to represent a threshold for growth. Observed nucleation and growth patterns are consistent with predictions of a simple physical model.

Two types of in-cylinder optical probes were applied to a single cylinder CFR engine to detect knocking combustion. The first probe was integrated directly into the engine spark plug to monitor the radiation from burned gas in the combustion process. The second was built into a steel body and installed near the end gas region of the combustion chamber. It measured the radiant emission from the end gas in which knock originates. The measurements were centered in the near infrared region because thermal radiation from the combustion products was believed to be the main source of radiation from a spark ignition engine. As a result, ordinary photo detectors can be applied to the system to reduce its cost and complexity. It was found that the measured luminous intensity was strongly dependent upon the location of the optical sensor.

Low emission heavy-duty diesel engines are increasingly utilizing four-valve designs with vertical central injectors. However, two-valve DI diesel engines with inclined injectors offset from the centerline of the piston bowl are likely to continue to be used in medium and light duty applications for some time. In such situations, designing of the hole-type nozzle is very difficult and may cause unavoidable back-drilling problems. The purpose of this paper is to solve back-drilling problems connected with hole-type nozzles and improve fuel-air mixing which leads to more efficient combustion. Based on geometric considerations, this paper introduces single-cone hole-type nozzles, double-cone hole-type nozzles, and the critical principal angles for hole-type nozzles. The single-cone hole-type nozzles and double-cone hole-type nozzles can meet requirements for height of the spray impingement points and spray orifice distribution angle at the same time.

A test reactor was designed for a 6.7 kW, 303 cc, single cylinder, air cooled, gasoline fueled engine. The reactor was very efficient at hydrocarbon (HC) and carbon monoxide (CO) reductions - with up to 99.9 and 98.6% removed, respectively. It had no effect on oxides of nitrogen (NOx) emissions. With the reactor, the engine met the California Air Resources Board (ARB) proposed Tier II emission standards. A factorial test was used to determine that A/F ratio and air injection rate significantly affected CO reduction efficiency whereas air injection location, ignition timing, and engine load did not. Relationships were established between CO reduction, air injection rate, and reactor core temperature.

A system has been developed that allows near real time measurements of total, volatile, and nonvolatile particle concentrations in engine exhaust. It consists of a short section of heated catalyst, a cooling coil, and an electrical aerosol analyzer. The performance of this catalytic stripper system has been characterized with nonvolatile (NaCl), volatile sulfate ((NH4)2 SO4), and volatile hydrocarbon (engine oil) particles with diameters ranging from 0.05-0.5 μm. The operating temperature of 300°C gives essentially complete removal of volatile sulfate and hydrocarbon particles, but also leads to removal of 15-25% of solid particles. This system has been used to determine total, volatile, and nonvolatile particle concentrations in the exhaust of a Diesel engine and a spark ignition engine. Volatile volume fractions measured in Diesel exhaust with the catalytic stripper system increased from 19-65% as the equivalence ratio (load) decreased from 0.64-0.13.

The formation of particles in the combustion chamber of a direct injection diesel engine has been studied with the use of the Total Cylinder Sampling Method. With this method, nearly the entire contents of the cylinder of an operating diesel engine can be quickly removed at various times during the combustion process. The particle mass and size distributions present in the sample can then be analyzed. If quenching of the combustion process is quick and complete, the resulting samples are representative of the particle mass and size distributions present in the cylinder near the time sampling begins. This paper discusses the effect of injection timing and piston bowl shape on the particle formation and oxidation. Example size distribution measurements are also shown. The particle concentrations in the cylinder were measured for three different injection timings with the standard piston installed in the engine.

Carbon black particles, which morphologically and chemically simulate a diesel exhaust soot, were mixed with the intake air of a single-cylinder direct injection diesel engine to investigate the efficiency of their removal by oxidation in the combustion chamber. An aerosol generation system, which is capable of generating carbon black aerosol of a size distribution and mass flow rate comparable to those of the soot agglomerates, was developed first. The aerosol was then introduced into the engine which was operating on conventional fuel. Four methods were used to characterize the exhaust particles: an electrical aerosol analyzer, a condensation nuclei counter, a low volume filter, and a micro-orifice cascade impactor. The size distribution and concentration of the diesel soot particles in the lubricants were investigated by methods of photosedimentation and quantitative spectrophotometry, respectively.

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.

Because of the more hostile environment in the compression ignition engine compared to the spark ignition engine, development and application of CI engine in-cylinder diagnostic methods have lagged those for SI engines. However, with more stringent federally mandated particulate and NOx standards which will go into effect in 1991 and 1994, the need for detailed information on the combustion processes in the cylinder is vital to controlling tailpipe emissions. The present paper contains a summary of the state-of-the-art techniques for determining in-situ species concentrations and profiles; particle concentrations, profiles, and size distributions; and temperature fields. Optical and physical probing methods, total cylinder dumping methods, and optical diagnostics applied for use in CI engine combustion chambers are discussed.

This paper describes an examination of the origin of the response of a real-time exhaust particle sensor. The sensor works by detecting the net electrical charge carried by diesel exhaust particles emitted during exhaust blow-down. The distribution of charge on these particles has been measured using an electrical mobility analysis system. The results show that the exhaust particles are highly charged and that their charge distributions are nearly symmetrical. The sensor signal results from a slight departure from this symmetry. The results suggest that most of the charge on the exhaust particles results from bipolar charging by flame ions during combustion, but that the net charge detected by the sensor results from surface interactions which some of the larger particles undergo during exhaust blowdown.

A unique system which allows sampling of the entire contents of one of the cylinders of a 5.7-liter V-8 indirect-injection diesel engine has been developed. An explosively actuated cutter ruptures a diaphragm in the combustion chamber and allows the contents of the cylinder to rush out and be subsequently diluted and quenched with cool nitrogen. Particles are collected with a high-volume impactor/filter system. This system has been used to collect a series of particle samples at crankangles ranging from 5 to 40 degrees after top dead center. Particle samples from the exhaust were also obtained. The samples have been extracted to determine the soluble organic fraction. These extracts have been analyzed for five polycyclic aromatic compounds: pyrene, fluoranthene, benz(a)pyrene, benz(k)fluoranthene, and 1-nitropyrene. The results indicate significant removal of the first four between the combustion chamber and the exhaust manifold.

Particle mass and size distribution measurements have been made on the exhaust of an Onan prechamber diesel engine. Seven fuels were examined: no. 1 and no. 2 diesel fuel, 40 and 50 cetane number secondary reference fuels, and no. 2 diesel fuel doped with three different concentrations of Lubrizol 565, a barium-based smoke suppressant. The no. 1 and no. 2 diesel fuels and the 50 cetane number reference fuels produced very similar emissions with emission indices in the range 0.3-1.3 mg (gm-fuel)-1 and volume mean diameters between .09 and 0.15 μm. The 40 cetane number reference fuel produced both smaller emission indices, 0.2 to 0.8 mg (gm-fuel)-1, and particle diameters, 0.03 to 0.09 μm. These reductions were apparently related to the longer ignition delay period of the 40 cetane number fuel, which allowed better mixing of the fuel and air prior to combustion.

This paper describes the performance and emissions of a hydrogen-fueled, spark-ignited engine. An electronic control device, designed to provide the engine with a timed injection of the fuel, is shown to give high mean effective pressures and high efficiencies. The oxides of nitrogen from the exhaust gases have been analyzed and the mechanism for their formation is reviewed. The paper further describes an experiment with traces of hydrocarbons added to the hydrogen in an attempt to explain any additional phenomena that may be taking place during the combustion, such as “prompt NO” which is known to occur in hydrocarbon flames only. As it turns out, such additions have a negligible effect on the NOx formation in the region investigated.

Combustion characteristics of an L-head engine combustion chamber have been examined using ionization probes and piezioelectric pressure transducers. The method describes how pressure rise rates, peak pressures, mean effective pressures, and flame arrival times were recorded. The flame arrival times were then used to find the position and shape of the flame front as a function of time. The influence of spark plug location on the above parameters was then examined for two different combustion chamber shapes.