Light duty vehicle emission standards are getting more stringent than ever before as stipulated by US EPA Tier 2 Standards and LEV III regulations proposed by CARB. The research in this paper sponsored by US DoE is focused towards developing a Tier 2 Bin 2 Emissions compliant light duty pickup truck with class leading fuel economy targets of 22.4 mpg "City" / 34.3 mpg "Highway". Many advanced technologies comprising both engine and after-treatment systems are essential towards accomplishing this goal. The objective of this paper would be to discuss key engine technology enablers that will help in achieving the target emission levels and fuel economy. Several enabling technologies comprising air-handling, fuel system and base engine design requirements will be discussed in this paper highlighting both experimental and analytical evaluations. Mostly, this paper will focus on steady-state emissions and fuel consumption results that are tied to operating duty cycle with actual vehicle comparisons wherever applicable. GT-Power 1D cycle simulation analysis was done to narrow the turbocharger and air-handling architecture evaluation. The importance of turbocharger matching is critical to achieving both power density and emission goals. This paper highlights the challenges involved in selecting a single stage variable geometry turbocharger capable of delivering a 75hp/liter power density in addition to meeting light duty drive cycle emission requirements. The benefits of low pressure [LP] and high pressure [HP] EGR systems for this light-duty engine architecture will be explored in detail along with outlining the possible strategy of dual loop EGR to reduce overall fuel consumption. On the combustion system development, this paper will highlight the importance of compression ratio, variable swirl architecture, injector nozzle hardware and injection strategy optimization towards meeting the stringent emissions, fuel consumption and noise targets. Fundamental thermodynamic explanations relating the fuel consumption improvements back to closed cycle and open cycle work are also being presented. Also, the paper will discuss challenges involving unburned HC and CO emissions when operating in premixed/low temperature combustion like regimes involving higher EGR rates and early pilot injection timings. Potential solutions to mitigate such undesired emissions have been investigated both analytically and experimentally.

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Characteristics of diesel sprays injected through Cummins medium-duty ISB injectors were studied experimentally in an optically accessible constant-volume combustion vessel. The experiments were performed with ultra-low-sulfur diesel (ULSD) under non-reacting and non-vaporizing conditions, including different ambient gas densities (23–65 kg/m3), injection pressures (500–1,500 bar), and injection duration times (0.5–1.5 ms). The ambient temperature of the vessel was maintained at a room temperature of 313 K for all the tests. A systematic comparison was made between single-hole (SH) and multi-hole (MH) injector configurations. A plume-to-plume variation in spray penetration length was observed for various operating conditions. A substantial deviation was observed for a specific hole against the averaged plume, indicating that arbitrary selection of the plume index may result in inaccurate spray characterization of the MH injector. The penetration length of the MH injector was shorter than that of the SH injector under the same operating conditions, indicating that a spray model calibrated on SH injector data may not accurately predict the transient spray behavior of the MH injector in practical engine simulations. A square-root correlation of the spray penetration length was applied for both the SH and MH injectors. The spray penetration length and dispersion angles of the ISB SH injector were also compared with those of the heavy-duty Cummins ISX SH injector. While the ISX SH injector showed a faster penetration than the ISB SH injector, the dispersion angle was similar. The differences in spray penetration between ISB and ISX injectors followed the expected trend based on their nozzle hole diameters.

This paper outlines a novel sensor selection and observer design algorithm for linear time-invariant systems with both process and measurement noise based on H2 optimization to optimize the tradeoff between the observer error and the number of required sensors. The optimization problem is relaxed to a sequence of convex optimization problems that minimize the cost function consisting of the H2 norm of the observer error and the weighted l1 norm of the observer gain. An LMI formulation allows for efficient solution via semi-definite programing. The approach is applied here, for the first time, to a turbo-charged spark-ignited engine using exhaust gas circulation to determine the optimal sensor sets for real-time intake manifold burnt gas mass fraction estimation. Simulation with the candidate estimator embedded in a high fidelity engine GT-Power model demonstrates that the optimal sensor sets selected using this algorithm have the best H2 estimation performance. Sensor redundancy is also analyzed based on the algorithm results. This algorithm is applicable for any type of modern internal combustion engines to reduce system design time and experimental efforts typically required for selecting optimal sensor sets.

Improving the efficiency of internal combustion engines can result in lower operating costs and enable reduced total cost of vehicle ownership. On the other hand, it is of utmost importance that the development of engine technologies is also directed toward curbing climate-altering and harmful emissions. One such technology is gasoline compression ignition, which can offer increased fuel efficiency and reduced emissions and criteria pollutants. By means of modal analysis methods, this study focuses on characterizing the internal flow behavior of a production, eight-hole, medium-duty diesel injector operating with gasoline-like fuels under typical diesel injection conditions. High-resolution tomographic reconstructions of the injector tip geometry, along with needle motion measurements, were obtained via X-ray measurements. This information was combined with a previously validated computational setup to perform a series of in-nozzle flow computational fluid dynamics (CFD) simulations. The CFD results were analyzed to identify the connection between the injector’s global behavior and relevant flowfields such as velocity and vorticity. The results obtained with the X-ray geometry were then compared against those obtained with a nominal geometry to investigate the effect of the injector’s geometric features on its behavior. Variations to the K-factor and inlet ellipticity of the orifices were explored, and these parameters’ ability to reduce in-orifice cavitation was assessed by analyzing the predicted in-orifice fuel vapor volume fraction. Relatively large and persistent flow structures arising within the injector sac were identified as the main driver for orifice-to-orifice variability, as their location and size impacted the amount of fuel delivered by each orifice. Assessing the extent to which these energetic structures impact the injector performance is of interest; thus, it is desirable to investigate the most energetically significant flowfield structures as a function of modifications to specific features of the injector geometry. Modal decomposition tools, such as space-only proper orthogonal decomposition (POD) and spectral proper orthogonal decomposition (SPOD) were applied to gain insight into dominant coherent structures that persist over the early phase of the needle opening event. It was found that the geometrical modifications applied resulted in variations of the modal energy content, as well as in the leading dominant spatial mode features. Additionally, it was found that the dominant frequency associated with the most significant energetic content was largely invariant to the geometrical modifications, with the difference between realistic and modified geometries being mostly found in the modal energy content.