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Innovative nozzle hole shapes for inwardly opening multi-hole gasoline direct injectors offer opportunities for improved mixture formation and particulate emissions reduction. Compared to increased fuel pressure, an alternative associated with higher system costs and increased pumping work, nozzle hole shaping simply requires changes to the injector nozzle shape and may have the potential to meet Euro 6 particulate regulations at today's 200 bar operating pressure. Using advanced laser drilling technology, injectors with non-round nozzle holes were built and tested on a single-cylinder engine with a centrally-mounted injector location. Particulate emissions were measured and coking deposits were imaged over time at several operating fuel pressures. This paper presents spray analysis and engine test results showing the potential benefits of alternative non-round nozzle holes in reducing particulate emissions and enhancing robustness to coking with various operating fuel pressures.

To meet future particulate number regulations, one path being investigated is higher fuel pressures for direct injection systems. At operating pressures of 30 MPa to 40 MPa, the fuel system components must be designed to withstand these pressures and additional power is required by the pump to pressurize the fuel to higher pressures than the nominal 15MPa to 20MPa in use today. This additional power to the pump can affect vehicle fuel economy, but may be partially offset by increases in combustion efficiency due to improved spray mixture preparation. This paper examines the impact on fuel economy from increased system fuel pressures from a combination of test results and simulations. A GDi pump and valvetrain model has been developed and correlated to existing pump torque measurements and subsequently used to predict the increase in torque and associated impact on fuel economy due to higher GDi system pressures.

New particulate sensing technologies are currently being readied for production to meet the on-board diagnostic (OBD) regulations associated with diagnosing diesel particulate filter (DPF) efficiency. The threshold levels for diagnosis have been tightened starting in 2013, requiring a new approach beyond the current techniques which often rely on differential pressure sensing across the filter. A new sensor has been developed to directly detect the particles passing through the DPF and estimate the cumulative particle flow. Using this information, an estimate can be made of the filter's efficiency and an associated diagnosis of its ability to meet emissions requirements. In this paper we will discuss the sensor's operating principle, accuracy and repeatability.

A gasoline compression-ignition combustion system is being developed for full-time operation over the speed-load map. Low-temperature combustion was achieved using multiple late injection (MLI), intake boost, and moderate EGR for high efficiency, low NOx, and low particulate emissions. The relatively long ignition delay and high volatility of RON 91 pump gasoline combined with an advanced injection system and variable valve actuation provided controlled mixture stratification for low combustion noise. Tests were conducted on a single-cylinder research engine. Design of Experiments and response surface models were used to evaluate injection strategies, injector designs, and various valve lift profiles across the speed-load operating range. At light loads, an exhaust rebreathing strategy was used to promote autoignition and maintain exhaust temperatures. At medium loads, a triple injection strategy produced the best results with high thermal efficiency.

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.