Search Results

A quasi-dimensional model for a direct injection diesel engine was developed based on experiments at Sandia National Laboratory. The Sandia researchers obtained images describing diesel spray evolution, spray mixing, premixed combustion, mixing controlled combustion, soot formation, and NOx formation. Dec [1] combined all of the available images to develop a conceptual diesel combustion model to describe diesel combustion from the start of injection up to the quasi-steady form of the jet. The end of injection behavior was left undescribed in this conceptual model because no clear image was available due to the chaotic behavior of diesel combustion. A conceptual end-of-injection diesel combustion behavior model was developed to capture diesel combustion throughout its life span. The compression, expansion, and gas exchange stages are modeled via zero-dimensional single zone calculations.

The Rotating Liner Engine (RLE) is an engine design concept where the cylinder liner rotates in order to reduce piston assembly friction and liner/ring wear. The reduction is achieved by the elimination of the mixed and boundary lubrication regimes that occur near TDC. Prior engines for aircraft developed during WW2 with partly rotating liners (Sleeve Valve Engines or SVE) have exhibited reduction of bore wear by factor of 10 for high BMEP operation, which supports the elimination of mixed lubrication near the TDC area via liner rotation. Our prior research on rotating liner engines experimentally proved that the boundary/mixed components near TDC are indeed eliminated, and a high friction reduction was quantified compared to a baseline engine. The added friction required to rotate the liner is hydrodynamic via a modest sliding speed, and is thus much smaller than the mixed and boundary friction that is eliminated.

EmiSense Technologies, LLC (www.emisense.com) is commercializing its electronic particulate matter (PM) sensor that is based on technology developed at the University of Texas at Austin (UT). To demonstrate the capability of this sensor for real-time PM measurements and on board diagnostics (OBD) for failure detection of diesel particle filters (DPF), independent measurements were performed to characterize the engine PM emissions and to compare with the PM sensor response. Computational fluid dynamics (CFD) modeling was performed to characterize the hydrodynamics of the sensor's housing and to develop an improved PM sensor housing with reproducible hydrodynamics and an internal baffle to minimize orientation effects. PM sensors with the improved housing were evaluated in the truck exhaust of a heavy duty (HD) diesel engine tested on-road and on a chassis dynamometer at the University of California, Riverside (UCR) using their Mobile Emissions Laboratory (MEL).

An electronic particulate matter sensor (EPMS) developed at the University of Texas was used to characterize exhaust gases from a single-cylinder diesel engine and a light-duty diesel vehicle. Measurements were made during transient tip-in events with multiple sensor configurations in the single-cylinder engine. The sensor was operated in two modes: one with the electric field energized, and the other with no electric field present. In each mode, different characteristic signals were produced in response to a tip-in event, highlighting the two primary mechanisms of sensor operation. The sensor responded to both the natural charge of the particulate matter (PM) emitted from the engine, and was also found to create a signal by charging neutral particles. The characteristics of the two mechanisms of operation are discussed as well as their implications on the placement and operation of the sensor.

This paper presents the latest developments in the design and performance of an electronic particulate matter (PM) sensor developed at The University of Texas at Austin (UT) and suitable, with further development, for applications in active engine control of PM emissions. The sensor detects the carbonaceous mass component of PM in the exhaust and has a time-resolution less than 20 (ms), allowing PM levels to be quantified for engine transients. Sample measurements made with the sensor in the exhaust of a single-cylinder light duty diesel engine are presented for both steady-state and transient operations: a steady-state correlation with gravimetric filter measurements is presented, and the sensor response to rapid increases in PM emission during engine transients is shown for several different tip-in (momentary increases in fuel delivery) conditions.

The basic process of spark ignition in engines has changed little over the more than 100 years since its first application. The rapid evolution of several advanced engine concepts and the refinement of existing engine designs, especially applications of power boost technology, have led to a renewed interest in advanced spark ignition concepts. The increasingly large rates of in-cylinder dilution via EGR and ultra-lean operation, combined with increases in boost pressures are placing new demands on spark ignition systems. The challenge is to achieve strong and consistent ignition of the in-cylinder mixture in every cycle, to meet performance and emissions goals while maintaining or improving the durability of ignitor. The application of railplug ignition to some of these engine systems is seen as a potential alternative to conventional spark ignition systems that may lead to improved ignition performance.

Combustion chamber pressure measurement in engines via a passage is an old technique that is still widely used in engine research. This paper presents improved passage designs for an off-set electrode spark plug designed to accept a pressure transducer. The spark plug studied was the Champion model 304-063A. Two acoustic models were developed to compute the resonance characteristics. The new designs have a resonance frequency in a range higher than the fundamental frequency expected from knock so that the signal can be lowpass filtered to remove the resonance and not interfere with pressure signal components associated with combustion phenomena. Engine experiments verified the spark plug resonance behavior. For the baseline engine operating condition approximately 50 of 100 cycles had visible passage resonance in the measured pressure traces, at an average frequency of 8.03 kHz.

High performance engine tuners have traditionally relied primarily on empirical techniques for intake flow optimization. This paper describes the use of a commercial Computational Fluid Dynamics (CFD) package to complement the traditional optimization strategies. This paper describes why some experimental methods are difficult to apply, including an example of Particle Image Velocimetry (PIV), and demonstrates the benefits of using computational analysis to investigate geometry changes to the intake or exhaust systems. This paper also illustrates the use of a Coordinate Measurement Machine (CMM) to digitize an existing cylinder head to develop a solid model suitable for CFD analysis. A comparison of results from a CFD prediction from a digitized solid model to a flow bench measurement demonstrates the validity and usefulness of this approach.

This paper explores the possibility of on-board fuel classification for fuel property adaptive compression-ignition engine control system. The fuel classifier is designed to on-board classify the fuel that a diesel engine is running, including alternative and renewable fuels such as bio-diesel. Based on this classification, the key fuel properties are provided to the engine control system for optimal control of in-cylinder combustion and exhaust treatment system management with respect to the fuel. The fuel classifier employs engine input-output response characteristics measured from standard engine sensors to classify the fuel. For proof-of-concept purposes, engine input-output responses were measured for three different fuels at three different engine operating conditions. Two neural-network-based fuel classifiers were developed for different classification scenarios. Of the three engine operating conditions tested, two conditions were selected for the fuel classifier to be active.

Four fuels in the gasoline boiling range where tested in a constant volume combustion bomb and a variable compression ratio HCCI engine. The fuels were tested using a port fuel injection system. The results of the experiments defined the range of HCCI operation in terms of the Coefficient of Variation (COV) of IMEP and the maximum rate of pressure rise. The results for the test fuels are compared to each other and to a baseline gasoline. The results are discussed in terms of the effects of the fuel properties (basically, various measure of ignition quality) on the engine heat release rates and efficiencies.

Fiber Reinforced Composites (FRCs) offer the possibility for reduced mass and increased performance in internal combustion engines, yet the automotive and aerospace industries have been slow to adopt these materials. Extensive research has been done over the past 25 years, producing nearly every components of an internal combustion engine out of some form of FRC. This Previous work is summarized herein. A prediction of engine weight reduction is made for direct substitution of FRCs. An additional prediction is made to quantify the additive effects of mass reduction on component mass, and power. It is estimated that engine mass might be reduced by as much as 70% using FRCs and reciprocating mass might be reduced by as much as 90%. In addition, increased mechanical efficiency on the order of 2% may be possible from reduced inertial and frictional loads.

A 2003 heavy-duty diesel engine (2002 emissions level) was used to test a representative biodiesel fuel as well as the methyl esters of several different fatty acids. The fuel variables included degree of saturation, the oxygen content, and carbon chain length. In addition, two pure normal paraffins with the corresponding chain lengths of two of the methyl esters were also tested to determine the impact of chain length. The dependent variables were the NOx and the particulate emissions (PM). The results indicated that the primary fuel variable affecting the emissions is the oxygen content. The emissions results showed that the highest oxygen content test fuel had the lowest emissions of both NOx and PM. As compared to the baseline diesel fuel the NOx emissions were reduced by 5 percent and the PM emissions were reduced by 83 percent.

A low pressure fuel distillation system is proposed for extracting a high-volatility fraction of gasoline, and to improve start-up and warm-up behavior of SI engines. More complicated methods for generating high-volatility start-up fuels have demonstrated improved cold start driveability and reduced HC emissions, but so far they have not been put into mass production. In this project, a ‘bench-top’ apparatus was used to investigate the feasibility of using sub-atmospheric pressures to extract a lighter and more volatile fraction from the parent gasoline. A series of experiments was conducted to evaluate the characteristics of the extracted fuel vapor as a function of temperature and pressure. The sensitivity to different brands and grades of gasoline was also explored. The results show that the extracted fuel consists mostly of C5 and C6 compounds, and that its Molecular Weight and Stoichiometric A/F ratio show little sensitivity to the pressure level used for the extraction.

An innovative pedal-assist system for bicycles has been designed and demonstrated by RevoPower Inc. This system incorporates a single-cylinder piston-ported two stroke engine, mounted radially within the front wheel hub of a bicycle. This design is light, compact, and easily adaptable to any common bicycle. However, this application presents some unique challenges for the engine and drivetrain. This paper describes a project undertaken to further develop this self-contained engine-driven bicycle wheel to improve its performance and reduce its noise emission. As described, a variety of computational end experimental techniques were used to analyze and improve the initial engine and wheel design. The work presented here resulted in a tripling of engine power over the baseline configuration, and a simultaneous overall sound reduction of nearly 20 dB(A).

Carbureted 2-stroke engines are a worldwide pandemic. There are over 50 million 2-stroke cycle engines in Asia alone, powering motorbikes, mopeds, “three-wheelers”, “auto-rickshaws”, “tuk-tuks”, and “tricycles”. These carbureted 2-stroke engines are characterized by high levels of hydrocarbon (HC), carbon monoxide (CO), and particulate matter (PM) emissions. Direct injection is a technology that has shown a great ability to reduce these emissions while at the same time improve fuel economy. A prototype kit has been designed for use in retrofitting existing carbureted two-stroke engines to direct injection. The kit was designed for use on a Kawasaki HDIII; a motorcycle from the Philippines that is commonly used as a taxi. It is however, a relatively common engine design and Kawasaki manufactures similar models for sale all over the world. The retrofit kit incorporates the Orbital air blast direct injection system.

Southwest Research Institute (SwRI) is exploring the feasibility of extending the performance and fuel efficiency of the spark ignition (SI) engine to match that of the emission constrained compression (CI) engine, whilst retaining the cost effective 3-way stoichiometric aftertreatment systems associated with traditional SI light duty engines. The engine concept, which has a relatively high compression ratio and uses heavy EGR, is called “HEDGE”, i.e. High Efficiency Durable Gasoline Engine. Whereas previous SwRI papers have been medium and heavy duty development focused, this paper uses results from simulations, with some test bed correlations, to predict multicylinder torque curves, brake thermal efficiency and NOx emissions as well as knock limit for light and medium duty applications.

SwRI has developed a new technology concept involving the use of high EGR rates coupled with a high-energy ignition system in a gasoline engine to improve fuel economy and emissions. Based on a single-cylinder study [1], this study extends the concept of a high compression ratio gasoline engine with EGR rates > 30% and a high-energy ignition system to a multi-cylinder engine. A 2000 MY Isuzu Duramax 6.6 L 8-cylinder engine was converted to run on gasoline with a diesel pilot ignition system. The engine was run at two compression ratios, 17.5:1 and 12.5:1 and with two different EGR systems - a low-pressure loop and a high pressure loop. A high cetane number (CN) diesel fuel (CN=76) was used as the ignition source and two different octane number (ON) gasolines were investigated - a pump grade 91 ON ((R+M)/2) and a 103 ON ((R+M)/2) racing fuel.

The Rotating Linear Engine (RLE) derives improved fuel efficiency and decreased maintenance costs via a unique lubrication design, which decreases piston assembly friction and the associated wear for heavy-duty natural gas and diesel engines. The piston ring friction exhibited on current engines accounts for 1% of total US energy consumption. The RLE is expected to reduce this friction by 50-70%, an expectation supported by hot motoring and tear-down tests on the UT single cylinder RLE prototype. Current engines have stationary liners where the oil film thins near the ends of the stroke, resulting in metal-to-metal contact. This metal-to-metal contact is the major source of both engine friction and wear, especially at high load. The RLE maintains an oil film between the piston rings and liner throughout the piston stroke due to liner rotation. This assumption has also been confirmed by recent testing of the single cylinder RLE prototype.

Cylinder liner rotation (Rotating Liner Engine, RLE) is a new concept for reducing piston assembly friction in the internal combustion engine. The purpose of the RLE is to reduce or eliminate the occurrence of boundary and mixed lubrication friction in the piston assembly (specifically, the rings and skirt). This paper reports the results of experiments to quantify the potential of the RLE. A 2.3 L GM Quad 4 SI engine was converted to single cylinder operation and modified for cylinder liner rotation. To allow examination of the effects of liner rotational speed, the rotating liner is driven by an electric motor. A torque cell in the motor output shaft is used to measure the torque required to rotate the liner. The hot motoring method was used to compare the friction loss between the baseline engine and the rotating liner engine. Additionally, hot motoring tear-down tests were used to measure the contribution of each engine component to the total friction torque.

As natural gas engines are designed to operate leaner and with increased boost pressure, durability of the spark plugs becomes problematic. Among the various new ignition devices that have been considered to solve some of the problems facing spark plugs, railplugs appear to hold clear advantages in some areas. There are two types of railplugs: coaxial rail and parallel rail. This paper reports the results of an experimental study of various parameters that affect the performance of parallel railplugs. Their performance was quantified by the distance that the arc traveled along the rails from the initiation point. Travel along the rails is thought to be an important performance metric because rail-travel limits excessive local wear and produces a distributed ignition source which can potentially reduce mixture inhomogeneity induced ignition problems.