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The effects of fuel composition on emissions levels from compression ignition engines can be profound, and this understanding has led to mandated reductions in both sulfur and aromatic content of automotive diesel fuels. A Navistar T444E (V8, 7.3 liter) engine was installed on an engine dynamometer and subjected to transient emissions measurement using a variety of fuels, namely federal low sulfur pump diesel; California pump diesel; Malaysian Fischer-Tropsch fuel with very low sulfur and aromatic content; various blends of soy-derived biodiesel; a Fischer-Tropsch fuel with very low sulfur and 10% aromatics; and the same Fischer-Tropsch fuel with 10% isobutanol by volume. The biodiesel blends showed their ability to reduce particulate matter, but at the expense of increasing oxides of nitrogen (NOx), following the simple argument that cetane enhancement led to earlier ignition. However, the Fischer-Tropsch fuels showed their ability to reduce all of the regulated emissions.

This study summarizes the work that has been done on the linear engine since it's invention. It attempts to highlight some of the major technologies, designs, and old and recent developments in the long history of the linear engine. In this paper, linear engines are grouped and studied from different standpoints such as internal or external combustion, 2-stroke vs. 4-stroke, number and arrangement of pistons, fuel type, the type of the machine the linear engine drives, depth of investigation, and the complexity of modeling the linear engine. This paper concludes that although simulation of the linear engine has been done with varying complexity and accuracy by several research groups and prototypes have run showing experimental results that predict higher efficiency for the linear engine than that of conventional engines, much work has to be done before the linear engine becomes commercially available.

A new technique of translating linear to rotary motion, using the Stiller- Smith mechanism, can be applied to the design of internal combustion engines and compressors. This new mechanism produces purely sinusoidal motion of the pistons relative to crank angle, which is a different motion from that produced by a conventional slider-crank mechanism, Influence of this sinusoidal motion on thermodynamic performance of engines and compressors was investigated theoretically and experimentally. Data are presented from a numerical analysis of compression and of spark-ignited combustion. Also, pressure-time curves for a standard and a modified (long connecting rod) spark ignition engine are compared. All data confirm that there is little thermodynamic difference between the Stiller-Smith and slider-crank devices.

The free piston engine combined with a linear electric alternator has the potential to be a highly efficient converter from fossil fuel energy to electrical power. With only a single major moving part (the translating rod), mechanical friction is reduced compared to conventional crankshaft technology. Instead of crankshaft linkages, the motion of the translator is driven by the force balance between the engine cylinder, alternator, damping losses, and springs. Focusing primarily on mechanical springs, this paper explores the use of springs to increase engine speed and reduce cyclic variability. A numeric model has been constructed in MATLAB®/Simulink to represent the various subsystems, including the engine, alternator, and springs. Within the simulation is a controller that forces the engine to operate at a constant compression ratio by affecting the alternator load.

Growing concern over ground-level ozone and its role in smog formation has resulted in extensive investigation into identifying ozone sources. Motor vehicle exhaust, specifically oxides of nitrogen and hydrocarbons, have been identified as major ozone precursors in urban areas. Past research has concentrated on assessing the impact of emissions from gasoline fueled light duty vehicles. However, little work has been done on identifying ozone precursors from medium and heavy duty diesel fueled vehicles. This paper presents the results of testing performed on a Navistar T 444E 190 horsepower diesel engine which is certified as a light/heavy-duty emissions classification and is used in medium duty trucks up to 11,800 kg (26,000 lb) GVW. Regulated emissions and speciated hydrocarbon emissions were collected using a filter, bag and Tenax adsorption cartridges for both steady state and transient engine operation.

Recent free piston engine research reported in the literature has included development efforts for single and dual cylinder devices through both simulation and prototype operation. A single cylinder, spring opposed, oscillating linear engine and alternator (OLEA) is a suitable architecture for application as a steady state generator. Such a device could be tuned and optimized for peak efficiency and nominal power at unthrottled operation. One of the significant challenges facing researchers is startup of the engine. It could be achieved by operating the alternator in a motoring mode according to the natural system resonant frequency, effectively bouncing the translator between the spring and cylinder, increasing stroke until sufficient compression is reached to allow introduction of fuel and initiation of combustion. To study the natural resonance of the OLEA, a numeric model has been built to simulate multiple cycles of operation.

In a recent study the present authors showed that piston motion in a compression ignition engine can have a small yet significant effect on ignition delay of diesel fuel. In particular, sinusoidal piston motion, or a motion with high dwell near top-dead-center, promotes reduced delay and improved cold starting relative to conventional slider-crank piston motion. This paper extends the analysis to the case of coal-diesel and coal-methanol blends, using experimental data from the thesis available in the literature. Ignition delay was shown again to be reduced with sinusoidal motion. In addition, the effect of piston motion on mass loss was considered. As expected, higher dwell near top-dead-center caused more mass loss, but there is still benefit to ignition delay of unusual piston motions unless the coefficient of leakage past the rings is very large.

Dual fuel engines employing pilot diesel injection to ignite premixed natural gas provide an opportunity for liquid petroleum fuel replacement and for reduced emissions of oxides of nitrogen (NOx) and particulate matter (PM). A Navistar T444E turbocharged V8 engine was converted to operate in dual fuel mode by metering the compressed natural gas (CNG) with an IMPCO Technologies, Inc. regulator and electronic valve while retaining the stock Navistar Hydraulically-Actuated Electronically-Controlled Unit Injection (HEUI) system for diesel pilot injection. A dedicated controller was designed and constructed to allow manual control of diesel fuel injection pulsewidth (FIPW), diesel injection advance (ADV), hydraulic injection control pressure (ICP) and natural gas mass flow. The controller employed two Microchip, Inc. PIC-based microcontrollers: one to perform initialization of a Silicon Systems, Inc. 67F867 engine interface peripheral, and the other to perform the runtime algorithms.

Series hybrid electric vehicles (HEVs) require power-plants that can generate electrical energy without specifically requiring rotary input shaft motion. A small-bore working prototype of a two-stroke spark ignited linear engine-alternator combination has been designed, constructed and tested and has been found to produce as much as 316W of electrical energy. This engine consists of two opposed pistons (of 36 mm diameter) linked by a connecting rod with a permanent magnet alternator arranged on the reciprocating shaft. This paper presents the numerical modeling of the operation of the linear engine. The piston motion of the linear engine is not mechanically defined: it rather results from the balance of the in-cylinder pressures, inertia, friction, and the load applied to the shaft by the alternator, along with history effects from the previous cycle. The engine computational model combines dynamic and thermodynamic analyses.

Selective NOX Recirculation (SNR) involves three main steps in NOX reduction. The first step adsorbs NOX from the exhaust stream, followed by periodic desorption from the aftertreatment medium. The final step passes the desorbed NOX gas into the intake air stream and feeds into the engine. A percentage of the NOX is expected to be decomposed during the combustion process. The motivation for this research was to clarify the reduction of NOX from large stationary engines. The objective of this paper is to report the NOX decomposition phenomenon during the combustion process from three test engines. The results will be used to develop an optimal system for the conversion of NOX with a NOX adsorbtion system. A 1993 Cummins L10G natural gas engine, a 1992 Detroit Diesel series 60 engine and a 13hp Honda gasoline engine were used in the experiments. Commercially available nitric oxide (NO) was injected into the engine intake to mimic the NOX stream from the desorption process.

A novel engine concept, currently under study, addresses many of the problems commonly associated with conventional internal combustion engines. In its simplest form the novel engine consists of a single crankshaft operating both a piston compressor and a piston expander which are connected by a continuous flame combustion chamber. One might regard this as a Brayton piston engine which is similar to a previous engine investigated by Warren. Also, due to the use of piston cylinders as the compression and expansion devices, this engine varies little mechanically from current engine technology thus allowing for easy implementation. The main improvement from conventional engine design is that the expansion cylinder can have a larger displacement than that of the compression cylinder. This allows more power to be extracted by lowering the loss due to blowdown and this will increase the thermal efficiency.

Concern over health effects associated with diesel exhaust and debate over the influence of high number counts of particles in diesel exhaust prompted research to develop a methodology for diesel particulate matter (PM) characterization. As part of this program, a tractor truck with an electronically managed diesel engine and a dynamometer were installed in the Old Dominion University (ODU) Langley full-scale wind tunnel. This arrangement permitted repeat measurements of diesel exhaust under realistic and reproducible conditions and permitted examination of the steady exhaust plume at multiple points. Background particle size distribution was characterized using a Scanning Mobility Particle Sizer (SMPS). In addition, a remote sampling system consisting of a SMPS, PM filter arrangement, and carbon dioxide (CO2) analyzer, was attached to a roving gantry allowing for exhaust plume sampling in a three dimensional grid. Raw exhaust CO2 levels and truck performance data were also measured.

Linear, crankless, internal combustion engines may find application in the generation of electrical power without the need to convert linear to rotary motion. The elimination of the connecting rod and crankshaft would significantly improve the efficiency of the engine and the reduced weight and cost is an added advantage. The case of two opposed cylinders, with two pistons linked by a solid rod, was considered for idealized modeling. The piston/rod assembly was considered to oscillate with only constant frictional drag. The Otto cycle was used to model efficiency, and this in turn determined compression ratio. Dimensionless groups governing the engine working were identified and used in formulating a description of the engine behavior. Two-stroke operation was assumed. Velocity and position can be related analytically to yield a phase plot.

The Fischer-Tropsch (F-T) catalytic conversion process can be used to synthesize diesel fuels from a variety of feedstocks, including coal, natural gas and biomass. Synthetic diesel fuels can have very low sulfur and aromatic content, and excellent autoignition characteristics. Moreover, Fischer-Tropsch diesel fuels may also be economically competitive with California diesel fuel if produced in large volumes. An overview of Fischer-Tropsch diesel fuel production and engine emissions testing is presented. Previous engine laboratory tests indicate that F-T diesel is a promising alternative fuel because it can be used in unmodified diesel engines, and substantial exhaust emissions reductions can be realized. The authors have performed preliminary tests to assess the real-world performance of F-T diesel fuels in heavy-duty trucks. Seven White-GMC Class 8 trucks equipped with Caterpillar 10.3 liter engines were tested using F-T diesel fuel.

Synthetic diesel fuel can be made from a variety of feedstocks, including coal, natural gas and biomass. Synthetic diesel fuels can have very low sulfur and aromatic content, and excellent autoignition characteristics. Moreover, synthetic diesel fuels may also be economically competitive with California diesel fuel if produced in large volumes. Previous engine laboratory and field tests using a heavy-duty chassis dynamometer indicate that synthetic diesel fuel made using the Fischer-Tropsch (F-T) catalytic conversion process is a promising alternative fuel because it can be used in unmodified diesel engines, and can reduce exhaust emissions substantially. The objective of this study was a preliminary assessment of the emissions from older model transit operated on Mossgas synthetic diesel fuel. The study compared emissions from transit buses operating on Federal no. 2 Diesel fuel, Mossgas synthetic diesel (MGSD), and a 50/50 blend of the two fuels.

The free piston linear engine has the potential to achieve high efficiency and might serve as a viable platform for robust implementation of low temperature combustion schemes (such as homogeneous charge compression ignition - HCCI) due to its ability to vary compression and stroke in response to cylinder and load events. A major challenge is control of the translator motion. Lack of geometric constraint on the piston leads to uncertainty about its top dead center position and timing. While combustion control depends on knowledge of the piston motion, the combustion event also affects the motion profile of the piston. To advance understanding of this coupled system, a numeric model was developed to simulate multiple cycles of a dual cylinder, spring assisted, 2-stroke HCCI, free piston linear engine generator.

Emissions of six 32 passenger transit buses were characterized using one of the West Virginia University (WVU) Transportable Heavy Duty Emissions Testing Laboratories, and the fixed base chassis dynamometer at the Colorado Institute for Fuels and High Altitude Engine Research (CIFER). Three of the buses were powered with 1997 ISB 5.9 liter Cummins diesel engines, and three were powered with the 1997 5.9 liter Cummins natural gas (NG) counterpart. The NG engines were LEV certified. Objectives were to contrast the emissions performance of the diesel and NG units, and to compare results from the two laboratories. Both laboratories found that oxides of nitrogen and particulate matter (PM) emissions were substantially lower for the natural gas buses than for the diesel buses. It was observed that by varying the rapidity of pedal movement during accelerations in the Central Business District cycle (CBD), CO and PM emissions from the diesel buses could be varied by a factor of three or more.

In an effort to develop engine/vehicle test methods that will reflect real-world emission characteristics, West Virginia University (WVU) designed and conducted a study on a Class-8 tractor with an electronically controlled diesel engine that was mounted on a chassis dynamometer in the Old Dominion University Langley full-scale wind tunnel. With wind speeds set at 88 km/hr in the tunnel, and the tractor operating at 88 km/hr on the chassis dynamometer, a Scanning Mobility Particle Sizer (SMPS) was employed for measuring PM size distributions and concentrations. The SMPS was housed in a container that was attached to a three-axis gantry in the wind tunnel. Background PM size-distributions were measured with another SMPS unit that was located upstream of the truck plume. Ambient temperatures were recorded at each of the sampling locations. The truck was also operated through transient tests with vehicle speeds varying from 65 to 88 km/hr, with a wind speed of 76 km/hr.

Data has been gathered using the West Virginia University Heavy Duty Transportable Emissions Laboratories from buses operating on diesel and a variety of alternate fuels in the field. Typically, the transportable chassis dynamo meter is set up at a local transit agency and the selected buses are tested using the fuel in the vehicle at the time of the test. The dynamometer may be set up to operate indoors or outdoors depending on the space available at the site. Samples of the fuels being used at the site are collected and sent to the laboratory for analysis and this information is then sent together with emissions data to the Alternate Fuels Data Center at the National Renewable Energy Laboratory. Emissions data are acquired from buses using the Central Business District cycle reported in SAE Standard J1376; this cycle has 14 ramps with 20 mph (32.2 km/h) peaks, separated by idle periods.

The Rand Cam engine is a novel design which avoids the use of pistons in favor of a cavity of varying size and shape. A set of vanes protrudes from a rotor into a circular trough in a stator. The vanes seal to the walls and base of the trough, which is of varying depth, and progress around the trough with rotation of the rotor. These vanes therefore pass through the rotor and are constrained to move parallel to the rotational axis. Intake and exhaust processes occur through ports in the stator wall which are revealed by the passing vanes. Advantages of the basic design include an absence of valves, reduction in reciprocating masses, presence of an integral flywheel in the rotor and strong fluid movement akin a swirl induced by the relative velocity between the rotor and stator.