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Regulated and unregulated exhaust emissions (individual hydrocarbons, aldehydes and ketones, polynuclear aromatic hydrocarbons (PAH), and nitro-polynuclear aromatic hydrocarbons (NPAH)) were characterized for the following alternate diesel combustion modes: premixed charge compression ignition (PCCI), and low-temperature combustion (LTC). PCCI and LTC were studied on a PSA light-duty high-speed diesel engine. Engine-out emissions of carbonyl compounds were significantly increased for all LTC modes and for PCCI-Lean conditions as compared to diesel operation; however, PCCI-Rich produced much lower carbonyl emissions than diesel operations. For PAH compounds, emissions were found to be substantially increased over baseline diesel operation for LTC-Lean, LTC-Rich, and PCCI-Lean conditions. PCCI-Rich operation, however, gave PAH emission rates comparable to baseline diesel operation.

Multi-dimensional numerical simulation of the combustion process in spark ignition engines were performed using the Coherent Flame Model (CFM) which is based on the flamelet assumption. The CFM uses a balance equation for the flame surface area to simulate flame surface advection, diffusion, production and destruction in a turbulent reacting flow. There are two model constants in CFM, one associated with the modeling of flame surface production and the other with the modeling of flame surface destruction. Previous experimental results on two test engines charged with propane-air mixtures were used to compare with the computations for different engine speeds, loads, equivalence ratios and spark plug locations. Predicted engine cylinder pressure histories agree well with the experimental results for various operating conditions after the model constants were calibrated against a reference operating condition.

Four-way catalyst system consisting of diesel oxidation catalyst (DOC), diesel particulate filter (DPF) and lean NOx trap (LNT) with alternative combustion such as low temperature combustion (LTC) and premixed controlled compression ignition (PCCI) is one of the effective ways to achieve the US Tier 2 Bin 5 and future European emissions for light duty diesel vehicles. However, thermal responses such as substrate temperature and temperature gradient of each catalyst component in the exhaust treatment system are different under different combustion modes and operation conditions. One exhaust treatment component's performance or durability can not be sacrificed for the sake of another. In this paper, thermal management strategies for exhaust treatment component temperature and temperature gradient by controlling lean and rich conditions of low temperature combustions as well as premixed controlled combustion, EGR rate and exhaust flow are demonstrated on a Renault G9T600 engine.

The Texas Project was a multi-year study of aftermarket conversions of a variety of light-duty vehicles to CNG or LPG. One aspect of this project was to examine the factors that influence the economics of fleet conversions to these alternative fuels. The present analysis did not include longer-term effects (such as possible increases in exhaust system life or increases in tire wear). Additionally, assumptions were required to estimate the costs of repairs to the alternative fuel system and engine. Other factors considered include conversion cost, fuel prices, annual alternative fuel tax (as applied for the state of Texas), annual miles accumulated, and the percent miles traveled while using the alternative fuel for dual fuel conversions.

The Texas Department of Transportation (TxDOT) began using an emulsified diesel fuel as an emissions control measure in July 2002. They initiated a study of the effectiveness of this fuel in comparison to conventional diesel fuel for TxDOT's Houston District operations and included the fleet operated by the Associated General Contractors (AGC) in the Houston area. Cost-effectiveness analyses, including the incremental cost per ton of NOx removed, were performed. NOx removal was the focus of this study because Houston is an ozone nonattainment area, and NOx is believed to be the limiting factor in ozone formation in the Houston area. The cost factors accounted for in the cost-effectiveness analyses included the incremental cost of the fuel (including an available rebate from the State of Texas), the cost of refueling more often, implementation costs, productivity costs, maintenance costs, and various costs associated with the tendency of the emulsion to separate.

Piston wetting can be isolated from the other sources of HC emissions from DISI engines by operating the engine predominantly on a gaseous fuel and using an injector probe to impact a small amount of liquid fuel on the piston top. This results in a marked increase in HC emissions. All of our prior tests with the injector probe used California Phase 2 reformulated gasoline as the liquid fuel. In the present study, a variety of pure liquid hydrocarbon fuels are used to examine the influence of fuel volatility and structure. Additionally, the exhaust hydrocarbons are speciated to differentiate between the emissions resulting from the gaseous fuel and those resulting from the liquid fuel. It is shown that the HC emissions correspond to the Leidenfrost effect: fuels with very low boiling points yield high HCs and those with a boiling point near or above the piston temperature produce much lower HCs.

A liquid-phase port injection system for liquefied petroleum gas (LPG) generally consists of a fuel storage tank with extended capability of operating up to 600 psi, a fuel pump, and suitable fuel lines to and from the LPG fuel injectors mounted in the fuel rail manifold. Port injection of LPG in the liquid phase is attractive due to engine emissions and performance benefits. However, maintaining the LPG in the liquid phase at under-hood conditions and re-starting after hot soak can be difficult. Multiphase behavior within a liquid-phase LPG injection system was investigated computationally and experimentally. A commercial chemical equilibrium code (ASPEN PLUS™) was used to model various LPG compositions under operating conditions.

The effect of combustion chamber wall-wetting on the emissions of unburned and partially-burned hydrocarbons (HCs) from gasoline-fueled SI engines was investigated experimentally. A spark-plug mounted directional injection probe was developed to study the fate of liquid fuel which impinges on different surfaces of the combustion chamber, and to quantify its contribution to the HC emissions from direct-injected (DI) and port-fuel injected (PFI) engines. With this probe, a controlled amount of liquid fuel was deposited on a given location within the combustion chamber at a desired crank angle while the engine was operated on pre-mixed LPG. Thus, with this technique, the HC emissions due to in-cylinder wall wetting were studied independently of all other HC sources. Results from these tests show that the location where liquid fuel impinges on the combustion chamber has a very important effect on the resulting HC emissions.

A team of student engineers at the University of Texas at Austin has designed and built “Texas Native Sun”, a solar powered vehicle for competition in GM Sunrayce U.S.A. The single-seat vehicle uses conventional photovoltaic solar cells to produce electricity for vehicle propulsion. The vehicle features graphite/epoxy composite monocoque construction, a high power-density permanent magnet electric motor, a mechanical/hydraulic continuously variable transmission, nickel-hydrogen satellite batteries, and a composite leaf spring suspension. The race strategies and tactics of energy management are optimized through use of a computer code which simulates the vehicle under race conditions. Much of the technology employed in the vehicle may one day become an ordinary part of future transportation systems which seek greater energy efficiency and less damage to the environment.

HCCI/PCCI combustion concepts have been demonstrated for both high brake thermal efficiency and low engine-out emissions. However, these advanced combustion concepts still could not be fully utilized partially due to the limitations of conventional fixed spray angle nozzle designs for issues related to wall wetting for early injections. The micro-variable circular orifice (MVCO) fuel injector provides variable spray angles, variable orifice areas, and variable spray patterns. The MVCO provides optimized spray patterns to minimize combustion chamber surface-wetting, oil dilution and emissions. Designed with a concise structure, MVCO can significantly extend the operation maps of high efficiency early HCCI/PCCI combustion, and enable optimization of a dual-mode HCCI/PCCI and Accelerated Diffusion Combustion (ADC) over full engine operating maps. The MVCO variable spray pattern characteristics are analyzed with high speed photographing.

The University of Texas 2000 Ethanol Vehicle Challenge team remains focused on cold start, cold drivability, fuel economy, and emissions reduction for our 2000 Ethanol Vehicle Challenge entry. We used the stock PCM for all control functions except control of an innovative cold-start system our team designed. The primary modifications for improved emissions control involved ceramic coating of the exhaust manifolds, use of close-coupled ethanol-specific catalysts, use of a moddified version of the California Emissions Calibrated PCM, and our cold-start system that eliminates the need to overfuel the engine at the beginning of the FTP. Additionally, we eliminated EGR at high load to improve power density. Major modifications, such as increasing the compression ratio or pressure boosting, were eliminated from consideration due to cost, complexity, reliability, or emissions penalties.

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.

An investigation of cyclic variability in a spark ignition engine is reported. Specifically, the predictions of an engine code have been compared with experimental data obtained using a well-characterized SI engine. The engine used for the experimental work and modeled in the code is the single cylinder research engine developed at Sandia National Laboratories and now operating at Drexel University. The data used for comparison were cylinder pressure histories for 110 engine cycles gathered during operation at a single engine operating condition. The code allows the various factors that could influence cyclic variability to be examined independently. Specifically, a model has been used to independently examine the effects of variations in equivalence ratio and of the turbulence intensity on cycle-to-cycle variations in the peak cylinder pressure, the crankangle of occurrence of peak pressure, the flame development angle, and the rapid burning angle.

Gasoline compression ignition (GCI) combustion is a promising solution to address increasingly stringent efficiency and emissions regulations imposed on the internal combustion engine. However, the high resistance to auto-ignition of modern market gasoline makes low load compression ignition (CI) operation difficult. Accordingly, a method that enables the variation of the fuel reactivity on demand is an ideal solution to address low load stability issues. Metal engine experiments conducted on a single cylinder medium-duty research engine allowed for the investigation of this strategy. The fuels used for this study were 87 octane gasoline (primary fuel stream) and diesel fuel (reactivity enhancer). Initial tests demonstrated load extension down to idle conditions with only 20% diesel by mass, which reduced to 0% at loads above 3 bar IMEPg.

A nephelometer system was developed to characterize engine particulate emissions from DISI engines. Results were correlated with images showing the location and history of particulates in the cylinder of an optical engine. The nephelometer's operation is based upon the dependence of scattered laser light on particulate size from a flow sampled from the exhaust of an engine. The nephelometer simultaneously measured the scattered light from angles of 20° to 160° from the forward scattering direction in 4° increments. The angular scattering measurements were then compared with calculations using a Mie scattering code to infer information regarding particulate size. Measurements of particulate mass were made based upon a correlation developed between the scattered light intensity and particulate mass samples trapped in a 0.2-micron filter. Measurements were made in a direct injection single-cylinder spark ignition research engine having a transparent quartz cylinder.

The aim of this study was to establish a fully capable diesel exhaust treatment system (4-way catalyst system) based on a catalyzed diesel particulate filter (cDPF) and a Lean NOx trap (LNT) for meeting US Tier 2 emissions. In this study, two modified combustion technologies, LTC (Low Temperature Combustion) and PCCI (Premixed Controlled Compression Ignition), were used and improved to achieve high catalyst bed temperatures and to provide rich exhaust gas with low smoke to utilize a 4-way catalyst system. The LTC operation area was expanded to both lower and higher loads using a dual loop EGR system (high-and low-pressure-loop EGR). The effect of air-fuel ratio, injection timing, and intake manifold temperature on combustion stability and soot emissions of LTC were investigated. PCCI, characterized by increased and advanced pilot injection, combined with retarded main injection timings and without EGR was used to achieve low-smoke, rich combustion at medium loads.

This paper presents the results of an experimental investigation of the fuel-air mixing process in a port-fuel-injected, 4-valve, spark-ignited engine that was motored to simulate cold cranking and start-up conditions. An infrared fiber-optic instrumented spark plug probe was used to measure the local, crank angle resolved, fuel concentration in the vicinity of the spark gap of a single-cylinder research engine with a production head and fuel injector. The crank-angle resolved fuel concentrations were compared for various injection timings including open-intake-valve (OIV) and closed-intake-valve (CIV) injection, using federal certification gasoline. In addition, the effects of speed, intake manifold pressure, and injected fuel mass were examined.

Diesel particulate filters (DPF) have been shown to effectively reduce particulate emissions from diesel engines. However, uncontrolled DPF regeneration can easily damage the DPF. In this paper, three different types of uncontrolled DPF regeneration are defined. They are: Type A: Uncontrolled high initial exotherm at the start of DPF regeneration, Type B: “Runaway” or uncontrolled regeneration, which takes place when the engine goes to idle during normal DPF regeneration, and Type C: Uneven soot distribution causing excess thermal stress during normal DPF regeneration. In this paper, different control strategies are developed for each of the three types of uncontrolled DPF regenerations. These control strategies include SOF control, exhaust flow pattern improvement, as well as EGR control through intake throttling and A/F ratio control.

An optical access engine was used to image the liquid film evaporation off the piston of a simulated direct injected gasoline engine. A directional injector probe was used to inject liquid fuel (gasoline, i-octane and n-pentane) directly onto the piston of an engine primarily fueled on propane. The engine was run at idle conditions (750 RPM and closed throttle) and at the Ford World Wide Mapping Point (1500 RPM and 262 kPa BMEP). Mie scattering images show the liquid exiting the injector probe as a stream and directly impacting the piston top. Schlieren imaging was used to show the fuel vaporizing off the piston top late in the expansion stroke and during the exhaust stroke. Previous emissions tests showed that the presence of liquid fuel on in-cylinder surfaces increases engine-out hydrocarbon emissions.

Recent research activities have greatly expanded the understanding of HCCI, its controlling mechanisms, and operation strategies. However, substantially more work is required before HCCI engines will be ready for production. This includes development of a methodology for feedback and closed-loop control of the fuel and air systems to realize HCCI combustion over the speed load range in a production vehicle. In this paper, we use in-cylinder ion sensing to extract the timing of start of combustion and monitor other combustion information such as knocking as feedback signals for closed loop control of HCCI engines. The ion sensor we use is modified from the existing glow plug. This method will minimize the cost relative to an in-cylinder pressure sensor and signal conditioning circuitry while providing equivalent combustion information for the ECU to control the engine.