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Abstract Modern transportation requires advanced powertrain systems to reduce the production of greenhouse gas CO2. Partially premixed combustion (PPC) is one of the most promising methods to achieve low emission and low fuel consumption of internal combustion engines. The present paper evaluated the effects of the calibration parameters on the efficiency and emissions of a multi-cylinder engine using PPC during stable operations, and the performance of the engine during transient operations. The peak gross indicated efficiency of 51.5% and the peak net indicated efficiency of 48.7% were achieved under stable operating conditions. The transient results also demonstrate an average net indicated efficiency of 47.5%. The nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbon (HC) conform with the Euro VI emission legislation in the case of most transient operations except some low load points.

Artículos en revistas Islands are facing considerable challenges in meeting their energy needs in a sustainable, affordable and reliable way. The present paper develops an integrated approach to economically assess initiatives that can transform island power systems into smart ones. Single and multi-action initiatives fostering the deployment of renewable energy sources (RES), energy storage systems (ESS), demand-side management (DSM), and electric vehicle (EV) are considered. An hourly unit commitment on a weekly basis is proposed to assess the impact of the initiatives on the system operation costs of five prototype island power systems, which have been identified by applying clustering techniques to a set of sixty islands power systems. The different investment costs of the initiatives are accounted for determining their corresponding internal rate of return (IRR) through their lifetime. The economic assessment of single and multi-action initiatives for five prototype islands representing sixty island power systems quantifies which initiatives are most suitable for which type of island power system. The assessment shows that islands of different sizes and features require different initiatives. Larger islands tend to DSM initiatives, whereas smaller islands tend to RES initiatives. Multi-action initiatives achieve highest system operation cost reduction, whereas single action initiatives yield to highest IRR. info:eu-repo/semantics/publishedVersion

Abstract The hydrothermal liquefaction (HTL) of microalgae produces water-soluble biocrude (WSB) and water-insoluble biocrude (WISB) simultaneously. The effects of heterogeneous catalysts (i.e. Pt/C, Ru/C, and Pt/C + Ru/C) on the properties of the two types of biocrudes derived from Chlorella HTL were explored for the first time. The results show that the addition of catalyst (Pt/C, Ru/C, or Pt/C + Ru/C) and/or the increase of residence time (from 10 to 30 min) could decrease the WSB fraction in total biocrude (WSB + WISB) mainly due to the improvement of the WISB yield. The catalytic effects on the WISB yield primarily occurred at the low algae loading (i.e., 1:10 of algae/water) condition, and there was a certain synergetic catalytic effect between Pt/C and Ru/C at this condition. The catalytic effect of Pt/C on the yields of WISB and total biocrude reduced as residence time increased. At the HTL conditions of 350 °C, 0.3 MPa H2, and 1:5 of algae/water for 30 min, Pt/C and Ru/C separately led to WSB and WISB with the highest C (63.57 and 74.16 wt%), H (7.34 and 8.44 wt%) contents and the lowest N (12.19 and 7.06 wt%), O (14.06 and 9.15 wt%) contents, and the highest HHVs (29.73 and 35.60 MJ/kg). The WISB produced with Pt/C mainly consisted of amides, hydrocarbons, organic acids and phenols. Pt/C could promote the cracking of high-molecular-weight compounds in WSB to form more low-boiling-point compounds.

Abstract Varying fuel injection strategies is one of the promising methods to reduce engine out emissions and improve its performance as injection characteristics have great influences on combustion process. Out of various injection strategies, injection rate shaping is potentially an effective technique to reduce emission from engines. Injection rate shaping helps in reducing NOx emissions and reduces combustion noise. This work investigates the effect of injection rate shaping on combustion and emission characteristics of a direct injection diesel engine fueled by biodiesel. The CFD simulations were performed using multi-dimensional KIVA-4 code coupled with CHEMKIN chemistry solver. A detailed chemical kinetics of methyl decanoate (MD) and methyl-9-decenoate (MD9D) with 112 species and 498 reactions were used as surrogate fuel for biodiesel. The injection rate shapes were varied in terms of boot length (long, medium and short boot length) and boot pressure (low, medium and high boot pressure) and it was found from the results that a trade-off between NOx and soot emissions were obtained for long boot length, and high boot pressure injection rate profiles.

Abstract Coal-fired power plants, cement plants and steel mills are three major CO2 emitters in the coastal areas of China. To examine potential CO2 reduction techniques in coastal areas, we used seawater as a CO2 absorbent with steel slag added to study the CO2 absorption capacity. An online chromatography apparatus was used to determine CO2 solubility in steel-slag-enhanced seawater, and the thermodynamics and kinetics were studied. CO2 was more soluble in seawater with steel slag than that in seawater alone, and as the concentration of steel slag increased, the CO2 solubility increased and mass transfer coefficient increased, favoring CO2 absorption rate by seawater. CO2 solubility increased on average by 115.56% when the steel slag increased by 1.0%. Among steel slag components, MgO had the strongest ability to enhance CO2 capture. CO2 solubility of seawater with 0.4% MgO was 0.0044 at 25 °C and 0.3 MPa. In addition, the combination addition of MgO and CaO had a strong synergistic effect on CO2 capture by seawater. Fe2O3 had a more remarkable capacity to accelerate CO2 capture than other steel slag components. The process was simulated by Aspen Plus to study the optimum operating conditions on the CO2-seawater-steel slag system. The optimum conditions (a liquid-gas mass ratio of 260, absorber temperature of 30 °C, absorber pressure of 1 atm, and steel slag-gas ratio of 0.10) ensured that CO2 absorption capacity was above 90% with low energy consumption and cost. Moreover two-thirds of the CO2 was captured and stored in calcium carbonate form. This process can provide CO2 capture and storage for coastal areas.

We propose several control algorithms and compare their performance and complexity through simulations; the control algorithms regulate the indoor climate of commercial buildings. The goal of these control algorithms is to use occupancy information to reduce energy use—over conventional control algorithms—while maintaining thermal comfort and indoor air quality. Three novel control algorithms are proposed, one that uses feedback from occupancy and temperature sensors, while the other two compute optimal control actions based on predictions of a dynamic model to reduce energy use. Both the optimal control based schemes use a model predictive control (MPC) methodology; the difference between the two is that one is allowed occupancy measurements while the other is allowed occupancy predictions. Simulation results show that each of the proposed controllers lead to significant amount of energy savings over a baseline conventional controller without sacrificing occupant health and comfort. Another key finding is that the feedback controller performs almost as well as the more complex MPC-based controllers. In light of the complexity of the MPC algorithms compared to the feedback control algorithm, we conclude that feedback control is the more suitable one for occupancy based zone-climate control. A related conclusion is that the difficulty of obtaining occupancy predictions does not commensurate with the resulting benefits; though these benefits are a strong function of ventilation standards.

Abstract Hydrofluorocarbons (HFCs) are now widely used in refrigeration and air-conditioning systems. These systems lose refrigerants through leaks and during servicing. This paper discusses the possibility of determining the emission rate of HFCs in buildings by applying tracer-gas techniques. The measurement of the emission rate of an HFC refrigerant (R134a) using the concentration-decay technique was carried out in a single-zone chamber. The results were compared with measurements made using an SF6 tracer and the Pitot-tube traverse method.

Abstract To obtain a better understanding of the characteristics of large-scale seasonal borehole thermal energy storage (BTES), a living laboratory was developed in Chifeng, China. In the living laboratory, combined heat sources of industrial waste heat and solar energy were adopted for 500000 m3 borehole thermal energy storage. The concept and design of the system, as well as the first operation results of the system, are presented herein. First, critical considerations for developing a large-scale borehole thermal energy storage system were briefly reviewed. The living laboratory was developed to be an experimental platform to conduct long-term field tests of major system operation options while working as an actual running application simultaneously. The flexibility of the system was enhanced using changeable system integration modes and a modular design for each subsystem. According to the monitoring results of the first heat injection period, a total of 33458.6 GJ of thermal energy was injected into the storage. The average soil temperature increased from 10.0 to 35.6 °C, and the core temperature increased to approximately 40.2 °C. The increase in soil temperature 5 m outside the storage was approximately 2 °C. No obvious temperature increase was observed 10 m outside the storage. The results indicate the potential of large-scale borehole thermal energy storage to be integrated into the district heating network to improve the flexibility, robustness, and energy efficiency of the overall energy system.