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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.

This paper focuses on the combustion development portion of the Advanced Combustion Controls Enabling Systems and Solutions (ACCESS) project, a joint research project partially funded by a Department of Energy grant. The main goal of the project is to improve fuel economy in a gasoline fueled light-duty vehicle by 30% while maintaining similar performance and meeting SULEV emission standards for the Federal Test Procedure (FTP) cycle. In this study, several combustion modes Spark Ignited (SI), Homogeneous Charge Compression Ignition (HCCI), Spark- Assisted Compression Ignition (SACI)) were compared under various conditions (naturally aspirated, boosted, lean, and stoichiometric) to compare the methods of controlled auto-ignition on a downsized, boosted multi-cylinder engine with an advanced valvetrain system capable of operating under wide negative valve overlap (NVO) conditions.

The use of Low Pressure - Exhaust Gas Recirculation (EGR) is intended to allow displacement reduction in turbocharged gasoline engines and improve fuel economy. Low Pressure EGR designs have an advantage over High Pressure configurations since they interfere less with turbocharger efficiency and improve the uniformity of air-EGR mixing in the engine. In this research, Low Pressure (LP) cooled EGR is evaluated on a turbocharged direct injection gasoline engine with variable valve timing using both simulation and experimental results. First, a model-based calibration study is conducted using simulation tools to identify fuel efficiency gains of LP EGR over the base calibration. The main sources of the efficiency improvement are then quantified individually, focusing on part-load de-throttling of the engine, heat loss reduction, knock mitigation as well as decreased high-load fuel enrichment through exhaust temperature reduction.

With increasingly stringent emissions regulations and concurrent requirements for enhanced engine thermal efficiency, a comprehensive characterization of the automotive gasoline fuel spray has become essential. The acquisition of accurate and repeatable spray data is even more critical when a combustion strategy such as gasoline direct injection is to be utilized. Without industry-wide standardization of testing procedures, large variablilities have been experienced in attempts to verify the claimed spray performance values for the Sauter mean diameter, Dv90, tip penetration and cone angle of many types of fuel sprays. A new SAE Recommended Practice document, J2715, has been developed by the SAE Gasoline Fuel Injection Standards Committee (GFISC) and is now available for the measurement and characterization of the fuel sprays from both gasoline direct injection and port fuel injection injectors.

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%).

High technology, spark ignition direct injection (SIDI), engines are currently capable of achieving optimum horsepower and ULEV emissions levels. However, to meet the requirements of modern automotive powertrains, the task of increasing power density, improving fuel economy and reaching SULEV2 emissions is much more challenging. To achieve this, direct injection (DI) fuel systems offer the greatest precision and flexibility for engine fuel control. Features like high pressure start and improved catalyst heating, through multiple injections per combustion cycle, produce low engine-out emissions without the need for a secondary air injection system. This paper describes the analytical and experimental work done to achieve SULEV emissions levels for a twin-turbocharged derivative of General Motors (GM) high feature V6 engine.

An experimental study is performed for homogeneous charge compression ignition (HCCI) combustion focusing on late phasing conditions with high cyclic variability (CV) approaching misfire. High CV limits the feasible operating range and the objective is to understand and quantify the dominating effects of the CV in order to enable controls for widening the operating range of HCCI. A combustion analysis method is developed for explaining the dynamic coupling in sequences of combustion cycles where important variables are residual gas temperature, combustion efficiency, heat release during re-compression, and unburned fuel mass. The results show that the unburned fuel mass carries over to the re-compression and to the next cycle creating a coupling between cycles, in addition to the well known temperature coupling, that is essential for understanding and predicting the HCCI behavior at lean conditions with high CV.

This paper focuses on the engine design portion of the Advanced Combustion Controls Enabling Systems and Solutions (ACCESS) project, a joint research project partially funded by a Department of Energy grant. The main goal of the project is to improve fuel economy in a gasoline fueled light-duty vehicle by 25% while maintaining similar performance and meeting SULEV emission standards. A Cadillac CTS with a high-feature naturally-aspirated 3.6L V6 engine was chosen as the baseline vehicle. To achieve the target fuel economy improvement over the baseline engine configuration, gasoline turbocharged direct-injection (GTDI) technology was utilized for engine downsizing in combination with part-load lean homogeneous charge compression ignition (HCCI) operation for further fuel economy gains. The GM 2.0L I4 GTDI Ecotec engine was used as the platform for the basis of this design.

High-pressure gasoline injection can improve combustion efficiency and lower engine-out emissions; however, the spray characteristics of high-pressure gasoline (>500 bar) are not well known. Effects of different injector nozzle geometry on high-pressure gasoline sprays were studied using a constant volume chamber. Five nozzles with controlled internal flow features including differences in nozzle inlet rounding, conicity, and outlet diameter were investigated. Reference grade gasoline was injected at fuel pressures of 300, 600, 900, 1200, and 1500 bar. The chamber pressure was varied using nitrogen at ambient temperature and pressures of 1, 5, 10, and 20 bar. Spray development was recorded using diffuse backlit shadowgraph imaging methods.

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.

With the wider use of biofuels in the marketplace, a program was conducted to study the deposit forming tendencies and performance of E85 (85% denatured ethanol and 15% gasoline) in a modern Flexible Fuel Vehicle (FFV). The test vehicle for this program was a 2006 General Motors Chevrolet Impala FFV equipped with a 3.5 liter V-6 powertrain. A series of 5,000 mile Chassis Dynamometer (CD) Intake Valve Deposits (IVD) and performance tests were conducted while operating the FFV on conventional (E0) regular unleaded gasoline and E85 to determine the deposit forming tendencies of both fuels. E85 test fuels were found to generate significantly higher levels of IVD than would have been predicted from the base gasoline component alone. The effects on the weight and composition of IVD due to a corrosion inhibitor and sulfates that were indigenous to one of the ethanols were also studied.

This paper describes a new tool to capture cylinder pressure information, calculate combustion parameters, and implement control algorithms. There are numerous instrumentation and prototyping systems which can provide some or all of this capability. The Cylinder Pressure Development Controller (CPDC) is unique in that it uses advanced high volume automotive grade circuitry, packaging, and software methodologies. This approach provides insight regarding the implementation of cylinder pressure based controls in a production engine management system. A high performance data acquisition system is described along with a data reduction technique to minimize data processing requirements. The CPDC software architecture is discussed along with model-based algorithm development and autocoding. Finally, CPDC calculated combustion parameters are compared with those from a well established combustion analysis system and thermodynamic simulations.

Implementation of real-time combustion feedback for use in closed-loop combustion control is a technology that has potential to assist in the successful production implementation of advanced diesel combustion modes. Low-temperature, pre-mixed diesel combustion is presently of interest because it offers the ability to lower the engine-out emissions of oxides of nitrogen (NOx) and particulate matter (PM). The need for lowering these two emissions is driven by tighter regulations enacted worldwide, especially the NOx limits in the United States. Reducing engine-out emissions eases the need for additional exhaust aftertreatment devices and their associated cost and mass. In this paper we will describe an experimental cylinder pressure-based control system and present both steady-state and transient results from a diesel engine employing a pre-mixed type of combustion.

2-Step variable-valve lift and timing is a high-value technology for the further development of automotive internal combustion engines. 2-Step valve train systems provide improved engine efficiency, emissions, and performance using components that are relatively low-cost and compatible with new and existing cylinder heads. This paper describes the design and development of a 2-Step rocker arm using a combination of analytical tools and physical testing. Prototype hardware was built to confirm the design. Performance and durability test results are presented.

Modern engines are becoming highly complex, with several strongly interactive subsystems - - variable cam phasers on both intake and exhaust, along with various kinds of variable valve lift mechanisms. Isolated component models may not yield adequate information to deal with system-level interactive issues, especially when it comes to transient behavior. In addition, massive amounts of expensive experimental work will be required for optimization. Recent computing speed improvements are beginning to permit the use of co-simulation to couple highly detailed and accurate submodels of the various engine components, each created using the most appropriate available simulation package. This paper describes such a system model using GT-Power to model the engine, AMESim to model cam phasers and the engine lubrication system, and Matlab/Simulink to model the engine controllers and the vehicle.

Strict NOx and soot emission regulations for Diesel engines have created an interest in low-temperature partially-homogeneous combustion regimes in both the US and Europe. One strategy, Homogeneous-Charge Late-Injection (HCLI) combustion utilizes 55% or more cooled external Exhaust Gas Recirculation (EGR) with a single Direct Injection strategy to control ignition timing. These engines are operated at low temperatures to ensure near zero NOx emissions, implying that fuel in the thermal boundary layers will not reach sufficient temperature to fully oxidize, resulting in Unburnt Hydrocarbon (UHC) and CO emissions. Of particular interest to HCLI engines are the UHC's that are not fully oxidized by the Diesel Oxidation Catalyst (DOC). Experimental measurements reveal that at average equivalence ratios greater than 0.8, methane is the single largest tailpipe-out UHC emission.

This paper describes a correlation study on fuel spray pattern recognition of multi-hole injectors for gasoline direct injection (GDi) engines. Spray pattern is characterized by patternation length, which represents the distance of maximum droplet concentration from the axis of the injector. Five fuel injectors with different numbers and sizes of nozzle holes were considered in this study. Experimental data and CFD modeling results were used separately to develop regression models for spray patternation. These regressions predicted the influence of a number of injector operating and design parameters, including injection system operating pressure, valve lift, injector hole length-to-diameter ratio (L/d) and the orientation of the injector hole. The regression correlations provided a good fit with both experimental and CFD spray simulation results. Thus CFD offers a good complement to experimental validation during development efforts to meet a desired injector spray pattern.

In recent years, advanced automotive technologies have been developed to increase engine output power and improve fuel economy. In order to design dedicated control algorithms for these cutting-edge techniques, a control-oriented model is developed in this paper to capture the behavior of a turbocharged Spark Ignition Direct Injection (SIDI) engine with Variable Valve Timing (VVT). In the proposed model, mean value models are employed to simulate the cycle-average dynamics of the airflow system, while a discrete-event model is used to capture the reciprocating engine combustion cycle. This model, established in Simulink, has been parameterized using experimental data that are collected from a four-cylinder SIDI engine over a wide range of operation conditions. The dynamic performance of this model was validated with data collected during engine transients.

Worldwide regulatory demands to reduce emissions of greenhouse gases and other airborne pollutants are leading to significant changes in internal combustion engines. Many engine subsystems such as fuel injection, valvetrain, turbochargers and EGR, are being changed to address these demands. Additionally, advanced combustion modes such as HCCI are being pursued to address the key shortcomings of today's gasoline and diesel engines. Cylinder pressure based control is an enabling technology to the development and application of advanced engine subsystems and a key control element for advanced combustion modes. This paper describes a tool for rapid development of closed-loop cylinder pressure based algorithms. The Cylinder Pressure Development Controller (CPDC) is an affordable, automotive grade package containing a unique architecture enabling real-time, next engine cycle combustion feedback control.

Flexible fuel vehicles (FFVs) are able to operate on a blend of ethanol and gasoline in any volumetric concentration of up to 85% ethanol (93% in Brazil). The estimation of ethanol content is crucial for optimized and robust performance in such vehicles. Even if an ethanol sensor is utilized, an estimation scheme independent of the ethanol sensor measurement retains advantages in enhancing the reliability of ethanol estimation and allowing on-board diagnostics. It is well-known that an exhaust gas oxygen (EGO) sensor could be utilized to estimate the ethanol content, which exploits the difference in stoichiometric air-to-fuel ratio (SAFR) between ethanol (9.0) and gasoline (14.6). The SAFR-based ethanol estimation has been shown to be prone to large errors with mass air flow sensor bias and/or fuel injector shift.