Search Results

Global demand for alternative fuels to combat rising energy costs has sparked a renewed interest in catalysts that can effectively remediate NOx emissions resulting from combustion of a range of HC based fuels. Because many of these new engine technologies rely on lean operating environments to produce efficient power, the resulting emissions are also present in a lean atmosphere. While HCs are easily controlled in such environments, achieving high NOx conversion to N2 has continued to elude fully satisfactory solution. Until recently, most approaches have relied on catalysts with precious metals to either store NOx and subsequently release it as N2 under rich conditions, or use NH3 SCR catalysts with urea injection to reduce NOx under lean conditions. However, new improvements in Ag based technologies also look very promising for NOx reduction in lean environments.

A 1.8L Gasoline Direct Injection Compression Ignition (GDCI) engine was tested over a wide range of engine speeds and loads using RON91 gasoline. The engine was operated with a new partially premixed combustion process without combustion mode switching. Injection parameters were used to control mixture stratification and combustion phasing using a multiple-late injection strategy with GDi-like injection pressures. At idle and low loads, rebreathing of hot exhaust gases provided stable compression ignition with very low engine-out NOx and PM emissions. Rebreathing enabled reduced boost pressure, while increasing exhaust temperatures greatly. Hydrocarbon and carbon monoxide emissions after the oxidation catalyst were very low. Brake specific fuel consumption (BSFC) of 267 g/kWh was measured at the 2000 rpm-2bar BMEP global test point.

The second generation 1.8L Gasoline Direct Injection Compression Ignition (GDCI) engine was built and tested using RON91 gasoline. The engine is intended to meet stringent US Tier 3 emissions standards with diesel-like fuel efficiency. The engine utilizes a fulltime, partially premixed combustion process without combustion mode switching. The second generation engine features a pentroof combustion chamber, 400 bar central-mounted injector, 15:1 compression ratio, and low swirl and squish. Improvements were made to all engine subsystems including fuel injection, valve train, thermal management, piston and ring pack, lubrication, EGR, boost, and aftertreatment. Low firing friction was a major engine design objective. Preliminary test results indicated good improvement in brake specific fuel consumption (BSFC) over the first generation GDCI engines, while meeting targets for engine out emissions, combustion noise and stability.

Increasingly stringent emissions regulations in automotive applications are driving advancements in after-treatment technology and emissions control strategies. Fast warm-up of the after-treatment system during the engine cold-start is essential to meet future emissions targets. In this study, a range of strategies were evaluated on a 2.2L, four cylinder, light-duty Gasoline Compression Ignition (GCI) engine with geometric compression ratio 17. The GCI engine has a single stage turbocharger and low-pressure exhaust gas recirculation (EGR) with EGR cooler bypass. For cold-start assist, the engine is equipped with a 2.5kW electric intake air heater. The aftertreatment system is comprised of an oxidation catalyst, followed by a particulate filter and an SCR catalyst. A GT-Power model of a light-duty diesel engine was modified to represent the GCI engine system setup for catalyst light-off strategies evaluations.

Low-cost lean NOx aftertreatment is one of the main challenges facing high-efficiency gasoline and diesel engines operating with lean mixtures. While there are many candidate technologies, they all offer tradeoffs. We have investigated a multi-component Dual SCR aftertreatment system that is capable of obtaining NOx reduction efficiencies of greater than 90% under lean conditions, without the use of precious metals or urea injection into the exhaust. The Dual SCR approach here uses an Ag HC-SCR catalyst followed by an NH3-SCR catalyst. In bench reactor studies from 150 °C to 500 °C, we have found, for modest C/N ratios, that NOx reacts over the first catalyst to predominantly form nitrogen. In addition, it also forms ammonia in sufficient quantities to react on the second NH3-SCR catalyst to improve system performance. The operational window and the formation of NH3 are improved in the presence of small quantities of hydrogen (0.1–1.0%).

A single-cylinder engine was used to study the potential of a high-efficiency combustion concept called gasoline direct-injection compression-ignition (GDCI). Low temperature combustion was achieved using multiple injections, intake boost, and moderate EGR to reduce engine-out NOx and PM emissions engine for stringent emissions standards. This combustion strategy benefits from the relatively long ignition delay and high volatility of regular unleaded gasoline fuel. Tests were conducted at 6 bar IMEP - 1500 rpm using various injection strategies with low-to-moderate injection pressure. Results showed that triple injection GDCI achieved about 8 percent greater indicated thermal efficiency and about 14 percent lower specific CO2 emissions relative to diesel baseline tests on the same engine. Heat release rates and combustion noise could be controlled with a multiple-late injection strategy for controlled fuel-air stratification. Estimated heat losses were significantly reduced.

The pursuit of new combustion concepts or modes is ongoing to meet future emissions regulations and to eliminate or at least to minimize the burden of aftertreatment systems. In this research, Premixed Low Temperature Diesel Combustion (PLTDC) was developed using a single-cylinder engine to achieve low NOx and soot emissions while maintaining fuel efficiency. Operating conditions considered were 1500 rpm, 3 bar and 6 bar IMEP. The effects of injection timing, injection pressure, swirl ratio, EGR rate, and multiple injection strategies on the combustion process have been investigated. The results show that low NOx and soot emissions can be obtained at both operating conditions without sacrificing the fuel efficiency. Low NOx and soot emissions are achieved through minimization of peak temperatures during the combustion process and homogenization of in-cylinder air-fuel mixture.

Regulatory and market pressures continue to challenge the automotive industry to develop technologies focused on reducing exhaust emissions and improving fuel economy. This paper introduces a practical model, which evaluates the economic value of various technologies based on their ability to reduce fuel consumption, improve emissions or provide consumer benefits such as improved performance. By evaluating the individual elements of economic value as viewed by the OEM manufacturer, while keeping the end consumer in mind, technology selection decisions can be made. These elements include annual fuel usage, vehicle performance, mass reduction and emissions, among others. The following technologies are discussed and evaluated: gasoline direct injection, variable valvetrain technologies, common-rail diesel and hybrid vehicles.

The automotive industry is facing tremendous challenges to improve fuel economy and emissions of the internal combustion engine. In the US, 2025 standards for fuel economy and CO2 emissions are extremely stringent. Simultaneously, vehicles must comply with new US Tier 3 emissions standards. In all market segments, there is a need for very clean and efficient engines operating on gasoline fuels. Gasoline Direct Injection Compression Ignition (GDCI) has been under development for several years and significant progress has been realized. As part of two US DOE programs, Delphi has developed a third generation GDCI engine that utilizes partially premixed compression ignition. The engine features an innovative “wetless”, low-temperature, combustion system with the latest high-pressure GDi injection system. The system was developed using extensive simulation and engine testing.

SwRI has developed the DCO® ignition system, a unique continuous discharge system that allows for variable duration/energy events in SI engines. The system uses two coils connected by a diode and a multi-striking controller to generate a continuous current flow through the spark plug of variable duration. A previous publication demonstrated the ability of the DCO system to improve EGR tolerance using low energy coils. In this publication, the work is extended to high current (≻ 300 mA/high energy (≻ 200 mJ) coils and compared to several advanced ignition systems. The results from a 4-cylinder, MPI application demonstrate that the higher current/higher energy coils offer an improvement over the lower energy coils. The engine was tested at a variety of speed and load conditions operating at stoichiometric air-fuel ratios with gasoline and EGR dilution.

A third generation Gasoline Direct Injection Compression Ignition (GDCI) engine has been designed and built. The engine is intended to meet stringent US Tier 3 emissions standards with diesel-like fuel efficiency. While nearly every aspect of the engine design has been improved over the previous second generation engine, this paper is primarily concerned with two of the most critical subsystems - the thermal management and EGR systems. These are especially important because gasoline compression ignition combustion is sensitive to intake gas temperature and exhaust gas dilution. Both parameters may deviate from steady state targets during transients. The quality of combustion control during transient vehicle operation is limited by significant response delay in both the thermal management and EGR systems. The intake air coolers must be sized for sufficient heat transfer capacity under peak load operating conditions, which results in coolers having significant thermal inertia.

Continued improvement in the combustion process of internal combustion engines is necessary to reduce fuel consumption, CO2 emissions, and criteria emissions for automotive transportation around the world. In this paper, test results for the Gen3X Gasoline Direct Injection Compression Ignition (GDCI) engine are presented. The engine is a 2.2L, four-cylinder, double overhead cam engine with compression ratio ~17. It features a “wetless” combustion system with a high-pressure direct injection fuel system. At low load, exhaust rebreathing and increased intake air temperature were used to promote autoignition and elevate exhaust temperatures to maintain high catalyst conversion efficiency. For medium-to-high loads, a new GDCI-diffusion combustion strategy was combined with advanced single-stage turbocharging to produce excellent low-end torque and power. Time-to-torque (TT) simulations indicated 90% load response in less than 1.5 seconds without a supercharger.

Fuel efficiency and emission performance sensitivity to fuel reactivity was examined using Delphi’s second-generation Gasoline Direct-Injection Compression Ignition (Gen 2.0 GDCI) multi-cylinder engine. The study was designed to compare a US market gasoline (RON 92 E10) to a higher reactivity gasoline (RON 80) at four operating conditions ranging from light load of 800 rpm / 2.0 bar gross indicated-mean-effective pressure (IMEPg) to medium load of 2000 rpm / 10.0 bar IMEPg. The experimental assessment indicated that both gasolines could achieve good performance and Tier 3 emission targets at each of the four operating conditions. Relative to the RON 92 E10 gasoline, better fuel consumption and engine-out emissions performance was achieved when using RON 80 gasoline; consistent with our previously reported single-cylinder engine research [1].

It is widely recognized that internal combustion engines (ICE) are needed for transport worldwide for years to come, however, demands on ICE fuel efficiency, emissions, cost, and performance are extremely challenging. Gasoline compression ignition (GCI) is one approach to achieve demanding efficiency and emissions targets. At Aramco Research Center-Detroit, an advanced, multi-cylinder GCI engine was designed and built using the latest combustion system, engine controls, and lean aftertreatment. The combustion system uses Aramco’s PPCI-diffusion process for ultra-low NOx and smoke. A P2 48V mild hybrid system was integrated on the engine for braking energy recovery and improved cold starts. For robust low-load operation, a 2-step valvetrain system was used for exhaust rebreathing. Test data showed that part-load fuel consumption was reduced 7 to 10 percent relative to a competitive 2.0L European diesel engine.