•Modelling of large marine two-stroke diesel engine with EGR and turbocharger cut out.•Impact of TC capacity ratio and EGR rate on fuel consumption and NOx emissions.•TC capacity ratio of 70:30 ...provides 169.4 g/kWh weighed BSFC introducing 2.6% penalty.•EGR blower speed control and cylinder bypass address engine and TC operational issues.•Recommendations for the engine–turbocharger matching are provided.
Albeit the exhaust gas recirculation (EGR) is widely used to reduce the nitrogen oxides (NOx) emissions from large marine two-stroke engines, several challenges emerge for the engine–turbocharging system matching considering the contradictory requirements of the engine and its subsystems operation. Such challenges become more pronounced in complex engine configurations that include parallel turbochargers and the EGR system along with cut out and bypass branches. This study aims at parametrically investigating a large marine two-stroke engine equipped with an EGR system, two parallel turbochargers of different size, and cut out branches. The turbocharging system characteristics are selected targeting the minimisation of the engine specific fuel consumption whilst ensuring compliance with the respective NOx emissions limits and satisfying imposed constraints for the compressors operation. A detailed model of the zero/one dimensional type is developed in the GT-SUITE software and used to simulate the investigated engine along with its subsystems. Simulation runs are performed to investigate the engine with four different turbocharger configurations of varying capacity ratio and under various operating conditions in terms of the EGR rate and engine load. The simulation results are analysed to reveal the impact of the turbocharger selection of the engine performance and emissions parameters. Furthermore, modulation schemes with EGR blower speed control, exhaust gas bypass and cylinder bypass are investigated to overcome the mismatch on the engine components flow rates and avoid turbocharger operational issues. The derived results demonstrate that the lowest weighted BSFC is achieved for the case of 70:30 capacity ratio between the large and small turbochargers, whilst the engine operation with the EGR is associated with a 2.6% penalty in the weighted BSFC. The EGR blower speed control is found sufficient to avoid the compressor overspeed at high engine loads exhibiting the lower BSFC penalty, whereas the cylinder bypass control is appropriate for controlling the compressor speed at low engine loads. This study contributes on delineating the underlying parameters and interactions between the engine components for the investigated marine two-stroke engine and provides recommendations for the engine–turbocharging system matching procedure.
Electrically heated catalyst (EHC) is integrated with the exhaust aftertreatment system to reduce cold-start emissions. Implementation of this proposed emission control technology will also provide ...addition CO2 and fuel consumption benefits. Developing an energy-efficient heating strategy has shown a significant reduction in the time required for the catalysts to light-off from the cold-start. In this study, it was found for the first time that the novel pulsating heating strategy with the pulse width of 30 s compared with typical heating strategy improved the CO and THC emissions conversion efficiency up to 34% and 31%, respectively. In contrast, a further increase in the heating pulse leads to lower emissions' conversion performance due to extending heating off period and consequently leading to the catalyst's light-out. Furthermore, combined electrical and fuel post-injection catalyst heating can benefit from the EHC's quick catalyst light-off and higher heating efficiency of the fuel post-injection, which showed a significant improvement in the DOC's emissions conversion performance. This approach can result in higher catalyst heating efficiencies and lower THC emissions which can be critical to meet the emissions legislations. An increase in the DOC's outlet temperature can be also beneficial for downstream aftertreatment component heating, e.g. DPF regeneration.
•At engine cold-start, hydrocarbon (HC) and carbon monoxide (CO) emissions are high.•Energy-efficient heating strategy reduces the time required for catalyst light-off.•Electrical heater enhances oxidation of CO and THC over a diesel oxidation catalyst.•Novel pulsating strategy improved CO and THC conversion efficiency by 34% and 31%.•Energy-efficient thermal management of catalyst has potential for hybrid vehicles.
This study aimed to analyze the trend of particulate matter (PM) generation from tires by nonexhaust systems. These types of PM are lesser known than the airborne PM generated from automotive exhaust ...systems. Specimens with rubber formulations similar to commercial tires for trucks and buses were artificially abraded, and the generated PM was analyzed. Abrasion of a specimen made of butadiene rubber, which is a synthetic rubber, generated lesser PM than a natural rubber specimen. This reduction of PM generation was particularly significant for PM10. Furthermore, using carbon black (a filler in tires) having small sized particles, the generation of PM2.5 was reduced to a large extent. To study the influence of tire aging on the increased generation of PM, rubber specimens were analyzed after prolonged exposure to a high temperature.
•Stirling engine as waste heat recovery system at the exhaust of diesel engine.•Experimental tests are performed to evaluate Stirling engine efficiency.•Velocity and pressure in Stirling engine is ...evaluated by an adiabatic model.•1D/3D model is developed to analyze the heat transfer mechanism.
This work analyzes the performances of a Stirling engine for waste heat recovery from the exhaust gas of internal combustion engines. Both experimental and numerical approaches were used. Experimental tests have been carried out on a research Stirling engine coupled to compression ignition engine by a thermally insulate pipe and a cap. Three configurations of coupling have been analyzed. Then, a three-dimensional numerical model has been developed by the authors to deepen the heat transfer between exhaust gas and working gas in the Stirling engine. The cap-heater system has been studied as a shell-and-tube heat exchanger. Experimental results have been set as boundary condition values for the cap, whereas for the heater, pressure and velocity have been evaluated using a 1D adiabatic model properly modified according to Stirling engine configuration. Velocity fields and temperature distribution inside the cap and heater have been analyzed, remarking that the layout of the heat exchanger becomes important for system efficiency. The method presented in this work could be useful to improve in wider terms the coupling between Stirling engine and internal combustion engines.
Abstract
In the event of a fire in a road tunnel, the effect of natural smoke exhaust alone is far inferior to that of mechanical smoke exhaust. Study of the characteristics of the flux of smoke ...gases inside the tunnel with the use of mechanical exhausts in case of sudden fire in road tunnels by means of specific model simulation methods, specific analysis by setting fixed exhaust spacing and different emission volumes, and the addition of fine water mist is studied. The results show that: when the exhaust vent spacing is 30m, the smoke exhaust volume in 30m³/s, 40m³/s, 50m³/s mechanical smoke exhaust device under the action of temperature, CO concentration and visibility will not affect the safe evacuation of the personnel, but taking into account the control of smoke propagation and economic reasonableness, the smoke exhaust volume of 40m³/s is better than the smoke exhaust volume of 30m³/s and 50m³/s. Under the coupling effect of mechanical smoke exhaust system and fine water mist, the spread of smoke in the tunnel can be controlled within a certain range and the internal temperature of the tunnel can be reduced. It can provide a certain basis for the design of the exhaust vent and the setting of water mist in the future.
This concept study presents an approach for resolving the trade-off between energy-efficient building operation and the provision of hygienically harmless indoor air quality. A novel coupling of ...HVAC-systems (heating, ventilation and air conditioning systems) with DAC-technology (direct air capturing technology) is proposed to separate CO2 in the exhaust air of buildings and recirculate the CO2-depleted air back into the building. In a mainly theoretical approach, the corresponding potentials and limitations of the novel HVAC/DAC-coupling in recirculation mode are evaluated. For that purpose, CO2-loads in the feed and exhaust air of four buildings located in Germany were measured using calibrated non-dispersive infrared (NDIR) sensors with pyroelectric detection principle. Subsequent numerical model simulations resort to typical meteorological data as well as building operation parameters grouped in different scenarios. The measurement and simulation results were assessed with regard to: (i) the unique possibilities of a HVAC/DAC-coupling in recirculation mode for the improvement of indoor air quality, (ii) the energy saving potentials through reduced air conditioning requirements enabled by a HVAC/DAC-coupling in recirculation mode, and (iii) the potential allocation of CO2 separated from building exhaust air for energetic and/or material reutilization in decentralized systems. In conclusion, a HVAC/DAC-coupling in recirculation mode can not only reduce the energy demand of buildings but also facilitates access to unutilized CO2-resources transported in the built environment and additionally offers the potential to improve indoor air quality. However, a suitable DAC module for operation in indoor air is not yet commercially available.
•HVAC/DAC-coupling in recirculation mode is proposed as new ventilation concept.•DAC-technology is expected to efficiently lower the CO2 concentration indoors.•HVAC/DAC-coupling allows to lower the energy demand of buildings for certain scenarios.•DAC in the built environment facilitates access to unutilized carbon sources.•Urban infrastructure enables DAC as keystone for sector coupling.
•Over 10% of engine original power was recovered using IBC WHR system.•Integration of ORC with IBC in the WHR system led to 18% extra power generation.•Employment of IBC-ORC WHR system increased the ...backpressure up to 0.8 bar.•The IBC and ORC power output fluctuations in various engine loads was investigated.•The system BSFC increased by 3% by employing proposed WHR system.•The system thermal efficiency decreased by 1% by employing proposed WHR system.
In this study, energy assessment is performed for an industrial turbocharged diesel engine integrated with a novel waste heat recovery (WHR) system. The exhaust energy is used in inverted Brayton cycle (IBC) for waste heat recovery purpose. Also, the heat energy from IBC heat exchanger is used as the heat source for the organic Rankine cycle (ORC) to produce extra power. The case study engine is modelled in AVL BOOST software and the model is validated against real engine performance data. For studying the performance of the proposed waste energy recovery system, IBC is added to the engine model in AVL BOOST software and the thermodynamic model of the ORC is developed in MATLAB and it is linked to AVL BOOST. Then, the model is solved, and the main engine output parameters are studied at 1800 RPM and various engine loads. The results show that employment of the proposed WHR system leads to enhancement of the system power by about 18%. However, the backpressure produced by installing the WHR system can result in increase of the BSFC up to 3% and reduction of the total thermal efficiency by almost 1% at engine full load condition. The results of this work contribute to determine the interactions between the proposed novel waste heat recovery system (IBC-ORC) and the engine. The proposed bottoming cycle based on IBC-ORC can be installed on existing industrial stationary engines for enhancement of power generation without imposing a new source of power generation.
Platinum group metals (PGM) and cerium as one of the rare-earth elements are considered as critical raw materials, thus their recycling and re-use is of utmost importance. Among the PGMs, platinum ...(Pt), palladium (Pd), and rhodium (Rh) are the basic and most valuable metals used in catalytic converters. Due to the high price of PGMs, there are already recycling routes in Europe and especially in Germany. For PGM and rare-earth elements, research is focusing on greener, plain recovery techniques, which utilize milder reagents, offer better energy efficiency, and replace the existing recycling routes. In this work, a hydrometallurgical process is proposed to add a hydrometallurgy method to the mostly pyrometallurgical industrial recycling routes, resulting in recovery rates for cerium and PGMs of 63.21% and only 1.03% with sulfuric acid, respectively. With hydrochloric acid, the leaching efficiency for cerium is even lower, and for PGM it is comparable. In the method proposed in the present paper, the main PGMs remain in monoliths and can be recycled in existing recycling routes like pyrometallurgical recycling.
Nitrogen isotope (δ15N) monitoring is a potentially powerful tool in tracing atmospheric nitrogen oxides (NOx); however, the isotopic fingerprint of vehicle exhaust remains poorly interpreted. This ...deficiency limits our understanding of the origin of atmospheric haze pollution, especially in China. In this study, we systemically explored the δ15N-NOx fingerprints of various vehicle exhausts (n = 137) in China. The δ15N-NOx values of vehicle exhausts ranged from −18.8‰ to +6.4‰, presenting a significant correlation with NOx concentrations (p < 0.01). The highest δ15N-NOx values were observed for liquefied petroleum gas vehicles (−0.1 ± 1.8‰), followed by gasoline vehicles (−7.0 ± 4.8‰) and diesel vehicles (−12.7 ± 3.4‰), all of which displayed a rising trend as emissions standards were continuously updated. The δ15N-NOx values under working conditions followed the trend warm start (−5.9 ± 5.0‰) > driving (−7.3 ± 5.9‰) > cold start (−9.2 ± 2.7‰). By establishing a suitable model for assessing representative δ15N-NOx values, the δ15N-NOx values of various vehicles, including different fuel types with different emission standards, were evaluated. A model of δ15N-NOx associated with motor vehicle data was developed, which estimated the national δ15N-NOx value of vehicle emissions to be −12.6 ± 2.2‰, but there was considerable variation among different target areas in China.
A recurrent concern in nature conservation is the potential competition for forage plants between wild bees and managed honey bees. Specifically, that the highly sophisticated system of recruitment ...and large perennial colonies of honey bees quickly exhaust forage resources leading to the local extirpation of wild bees. However, different species of bees show different preferences for forage plants. We here summarize known forage plants for honey bees and wild bee species at national scale in Denmark. Our focus is on floral resources shared by honey bees and wild bees, with an emphasis on both threatened wild bee species and foraging specialist species. Across all 292 known bee species from Denmark, a total of 410 plant genera were recorded as forage plants. These included 294 plant genera visited by honey bees and 292 plant genera visited by different species of wild bees. Honey bees and wild bees share 176 plant genera in Denmark. Comparing the pairwise niche overlap for individual bee species, no significant relationship was found between their overlap and forage specialization or conservation status. Network analysis of the bee-plant interactions placed honey bees aside from most other bee species, specifically the module containing the honey bee had fewer links to any other modules, while the remaining modules were more highly inter-connected. Despite the lack of predictive relationship from the pairwise niche overlap, data for individual species could be summarized. Consequently, we have identified a set of operational parameters that, based on a high foraging overlap (>70%) and unfavorable conservation status (Vulnerable+Endangered+Critically Endangered), can guide both conservation actions and land management decisions in proximity to known or suspected populations of these species.
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