In order to improve the thermal efficiency of engines, it is essential to increase their geometric compression ratio or the expansion ratio. This research explores the technology options to enable a higher expansion ratio in future boosted spark-ignition direct-injection engines, with the aim of significantly reducing the fuel consumption while achieving the same torque and combustion performances as those of baseline turbocharged engines. Variable-valve-actuation technologies such as the late-intake-valve-closing cam strategy and the early-intake-valve-closing cam strategy were considered, and their effectiveness in reducing the effective compression and preventing knock in high-compression-ratio engines was assessed. To compensate for the torque loss due to late intake valve closing or early intake valve closing, multi-stage boosting systems including the turbocharger–supercharger combination and the two-stage turbocharger were implemented and compared. In this study, a Miller cycle engine concept with a high expansion ratio of 12.0:1 was developed with variable valve actuation and multi-stage boosting. On the basis of this new concept, an engine was built and extensively tested on an engine dynamometer to assess its part-load fuel consumption and full-load performance. The experimental results indicated that this engine concept can improve the fuel economy of the vehicle by 3–4% at typical city and highway driving conditions while maintaining the same performance.
Distributed Energy Resources (DER) connected to Smartgrids are most of the time addressed on a grid operation point of view or on a commercial point of view, moreover focusing only on one layer of the overall electricity grids structure. However, interdependencies between grid and commercial operation as well as interconnection of more and more systems and involvement of numerous actors at various levels of the electricity value chain raise growing challenges that are presented in this paper. A market-based approach called Next Generation Marketplace (NGM) is introduced as a potential response and solution to these challenges. The paper presents several NGM aspects such as underlying rationale and pillars, a practical illustration through a detailed use case, and recommendations on corresponding IT infrastructure. The paper concludes that a NGM approach is a necessary step to see Smartgrids evolving towards Smarter markets but still requires regulation evolutions.
In this paper, the development of a Miller cycle gasoline engine which has a high compression ratio from 11.5:1 to 12.5:1, single-stage turbocharging and external cooled exhaust gas recirculation is described. The improvement in the fuel economy by adding external cooled exhaust gas recirculation to the Miller cycle engine at different geometric compression ratios were experimentally evaluated in part-load operating conditions. The potential of adding external cooled exhaust gas recirculation in full-load conditions to mitigate pre-ignition in order to allow higher geometric compression ratios to be utilized was also assessed. An average of 3.2% additional improvement in the fuel economy was achieved by adding external cooled exhaust gas recirculation to the Miller cycle engine at a geometric compression ratio of 11.5:1. It was also demonstrated that the fuel consumption of the engine with external cooled exhaust gas recirculation was reduced by 3-7% in a wide range of part-load operating conditions and that the engine output of the Miller cycle engine at a geometric compression ratio of 12.5:1 increased at 2000 r/min in the full-load condition. The Miller cycle engine with external cooled exhaust gas recirculation at a geometric compression ratio of 12.5:1 achieved a broad brake specific fuel consumption range of 220 g/kW h or lower, with the lowest brake specific fuel consumption of 215 g/kW h. While there are still challenges in implementing external cooled exhaust gas recirculation, the Miller cycle engine with single-stage turbocharging and external cooled exhaust gas recirculation showed its potential for substantial improvement in the fuel economy as one of the technical pathways to meet future requirements in reducing carbon dioxide emissions.
This paper describes the design optimization of a compound boosting system consisting of a turbocharger and a supercharger for a 2.0 l four-cylinder Miller cycle engine which has a high expansion ratio of 12.0:1 and variable valve actuation. Various system configurations and supercharger sizes were evaluated numerically and experimentally to reduce the supercharger power consumption and the engine fuel consumption while maintaining the same engine torque performance in steady-state conditions. The supercharger–turbocharger boosting system with a V400 supercharger showed an average engine fuel consumption that was 2.8% lower in boosted conditions than did the turbocharger–supercharger boosting system with the same V400 supercharger; this was predicted by engine cycle simulations and verified by experiments. When the supercharger was placed upstream of the turbocharger, the supercharger inlet pressure was lower and the total mass flow rate through the supercharger was reduced, which reduced the supercharger power consumption and the bypass air flow. The turbocharger–supercharger boosting system with a smaller supercharger (R340 or V250) significantly improved the engine efficiency (by 3.3% or 5.0% respectively in comparison with the turbocharger–supercharger boosting system with a V400 supercharger), by reducing the mass air flow rates through the supercharger and minimizing the supercharger power consumption. The turbocharger–supercharger boosting system with a V250 supercharger achieved the lowest engine fuel consumption in full-load conditions of all the turbocharger and supercharger compound boosting system options evaluated for the 2.0 l Miller cycle engine on the basis of the simulation results. This study defined the optimal system layout and the optimal supercharger size for implementing the turbocharger and supercharger compound boosting system on a 2.0 l Miller cycle spark ignition engine to maximize the improvement in the fuel economy of the vehicle while maintaining the same torque performance.
Lighting subsystems account for up to 50% of the energy consumption of a typical tunnel. Day‐time lighting levels account for over two‐thirds of the total system lighting power; their periodic nature creates daily peaks in the tunnel's energy load profile. This paper studies the integration of semitransparent photovoltaic (STPV) cells into sunscreen structures installed above tunnel entrances to reduce tunnel lighting requirements and offset their day‐time lighting loads using energy generated from PVs. The electrical lighting load of a typical 1‐km length road tunnel with and without STPV sunscreen structures was modeled to establish the potential for energy savings. Using a daylighting and energy modeling plug‐in called DIVA, the transparencies and ratios of photovoltaics (PV) to glass of a STPV sunscreen that are in accordance with the luminance reduction code requirements were determined. Reduced lighting requirements over the whole tunnel length, including the threshold, transition, and interior lighting zones of the tunnel were considered, resulting in significant energy savings. The annual power production of the sections covered with STPV was then simulated using the PVsyst software. The integration of PV cells resulted in an annual energy production that reduced annual net‐energy use by up to 7% and with the potential to reduce electric lighting loads by up to 60% during the day‐time. Results also demonstrated that STPV sunscreens have the potential to meet luminance requirements if supplemented with an intelligent lighting control system.
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