A series of ceria-cobalt oxide (Co
100−
x
Ce
x
) catalysts with controlled metal molar ratios were tested for the catalytic performance of NO reduction by CO. The structural property, and surface ...chemistry were investigated by nitrogen adsorption, X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photo-electron spectroscopy, and temperature-programmed reduction by hydrogen. The flow reactor studies revealed that the Co
98
Ce
2
catalyst can achieve 99% N
2
selectivity at a relatively low temperature (260 °C), and the Co
15
Ce
85
catalyst exhibits ∼100% N
2
selectivity at a high temperature (580 °C). Notably, the tandem use of Co
98
Ce
2
and Co
15
Ce
85
catalysts (molar ratio 1 : 1) achieved 99.6% conversion of NO and 99.7% selectivity of N
2
for a wide temperature range from 250 to 680 °C. The synergistic effects of Ce and Co were evidenced in this work. The Co
2+
/Co
3+
ratio was increased with 2% Ce incorporation, which could promote NO adsorption at low temperature; the Ce-O-Co solid solution formed rich surface oxygen that may promote CO oxidation through the Mars-van Krevelen mechanism on surfaces and oxygen vacancies would be replenished when adsorbed NO molecules were reduced to N
2
. The rich O/(Ce + Co), Co
2+
/Co
3+
, and Ce
4+
/Ce
3+
pairs on the surface of Co
100−
x
Ce
x
promoted sustainable activity for NO decomposition to N
2
. This study provides a promising avenue for boosting the conversion of polluted exhaust gas
via
designing suitable tandem catalysis systems.
The effectiveness of the tandem catalysts was verified by a combination of Co
98
Ce
2
for low temperature reactions and Co
15
Ce
85
for high temperature reactions.
Isocyanic acid (HNCO) is a chemical constituent suspected to be harmful to
humans if ambient concentrations exceed ∼1 ppbv. HNCO is
mainly emitted by combustion processes but is also inadvertently ...released
by NOx mitigation measures in flue gas treatments. With increasing
biomass burning and more widespread usage of catalytic converters in car
engines, good prediction of HNCO atmospheric levels with global models is
desirable. Little is known directly about the chemical loss processes of HNCO,
which limits the implementation in global Earth system models. This study
aims to close this knowledge gap by combining a theoretical kinetic study on
the major oxidants reacting with HNCO with a global modelling study. The
potential energy surfaces of the reactions of HNCO with OH and NO3
radicals, Cl atoms, and ozone were studied using high-level
CCSD(T)/CBS(DTQ)//M06-2X/aug-cc-pVTZ quantum chemical methodologies,
followed by transition state theory (TST) theoretical kinetic predictions of the rate coefficients at
temperatures of 200–3000 K. It was found that the reactions are all slow in
atmospheric conditions, with k(300K)≤7×10-16 cm3molecule-1s-1, and that product formation occurs predominantly by
H abstraction; the predictions are in good agreement with earlier
experimental work, where available. The reverse reactions of NCO radicals
with H2O, HNO3, and HCl, of importance mostly in combustion, were
also examined briefly. The findings are implemented into the atmospheric model EMAC (ECHAM/MESSy Atmospheric Chemistry) to estimate the
importance of each chemical loss process on a global scale. The EMAC
predictions confirm that the gas-phase chemical loss of HNCO is a negligible
process, contributing less than 1 % and leaving heterogeneous losses as the
major sinks. The removal of HNCO by clouds and precipitation contributes
about 10 % of the total loss, while globally dry deposition is the main
sink, accounting for ∼90 %. The global simulation also
shows that due to its long chemical lifetime in the free troposphere, HNCO
can be efficiently transported into the UTLS by deep convection events.
Daily-average mixing ratios of ground-level HNCO are found to regularly
exceed 1 ppbv in regions dominated by biomass burning events, but rarely
exceed levels above 10 ppt in other areas of the troposphere, though locally
instantaneous toxic levels are expected.
Abstract
A vapor injection heat pump using electric motor exhaust thermal and ambient air is proposed. This system is applied in pure electric vehicles to improve the air conditioning system consumes ...too much energy when the ambient temperature is lower than -15°C that affects the vehicle mileage. The compressor of two inlets connected with the high-pressure heat exchanger and the outside evaporator. Mathematical models about vapor injection compressor have been built. The performance analysis is carried out under variable conditions. The results show that the vapor injection heat pump using electric motor waste thermal and ambient air has more performance in low ambient. The optimal opening about the high-pressure electronic expansion valve (EXV) is 13%, and the optimal COP for the air conditioning system is 1.75, the car inside outlet temperature higher than 40°C.
The design of thermal structures in the aerospace industry, including exhaust structures on embedded engine aircraft and hypersonic thermal protection systems, poses a number of complex design ...challenges. These challenges are particularly well addressed by the material layout capabilities of structural topology optimization; however, no topology optimization methods are readily available with the necessary thermoelastic considerations for these problems. This is due in large part to the emphasis on cases of maximum stiffness design for structures subjected to externally applied mechanical loads in the majority of topology optimization applications. In addition, while limited work in the literature has investigated thermoelastic topology optimization, a direct treatment of thermal stresses is not well documented. Such a treatment is critical in the design of thermal structures where excessive thermal stresses are a primary failure mode. In this paper, we present a method for the topology optimization of structures with combined mechanical and thermoelastic (temperature) loads that are subject to stress constraints. We present the necessary steps needed to address both the design-dependent thermal loads and accommodate the challenges of stress-based design criteria. A relaxation technique is utilized to remove the singularity phenomenon in stresses and the large number of stress constraints is handled using a scaled aggregation technique that has been shown previously to satisfy prescribed stress limits in mechanical problems. Finally, the stress-based thermoelastic formulation is applied to two numerical example problems to demonstrate its effectiveness.
•Ethanol-gasoline blends tested on cylinder engine and two vehicles over a dynamometer.•Hydrocarbons emissions increases with EtOH content while CO, NOx decreases.•Fuel sensitivity depends on ...HoV.•Conventional vehicles can operated with ethanol content up to 20% volume.•Ozone forming potential decrease as ethanol increase in the blend.
The study investigated the combustion and emissions of gasoline engines using four ethanol–gasoline blends ranging from 10 to 85 volume percent ethanol, and an E0 control Performance were compared in single cylinder engine and tested in a chassis dynamometer using two Tier I vehicles. The octane sensitivity of the fuels increases with the addition of ethanol from 7.8 for a non-oxygenated fuel to 23 for the 85% ethanol blend. Fuel sensitivity have a direct relationship with the latent heat of vaporization, because charge cooling is one of the way alcohols increases Research Octane Number. For the primary gaseous compounds, an increase in total hydrocarbon emissions and a decrease in aromatic BTEX compounds was detected as the amount of ethanol in the fuel increased. Both vehicles operated without engine fault code display except when the E-85 was used. The engine could be started stably with E10, E20, and E45. However, for E85 the engine idling became unstable because the air–fuel mixture was too lean making impossible the reduction reactions necessary for NOx emission control in the catalytic converter.
The paper describes the results achieved in an experimental study aimed at identify the operating parameters, in terms of fuel injection characteristics, intake/exhaust conditions and ...thermomechanical stress of engine and turbocharger, required to exceed the high threshold of 100 kW/l for light-duty high speed diesel engines. In order to increase the power/weight-volume ratio, such target is currently one of the milestones for diesel engine development engineers. To achieve the specific power target a high-performance prototype 0.5 l single-cylinder engine demonstrator was developed employing some special very robust components and high-quality parts from the state-of-art automotive diesel technology. A prototype advanced piezo injection system, capable of 3000 bar maximum injection pressure, was employed. Geometrical features of the combustion system and injector nozzle were carefully preconfigured based on the characteristics of the most recent diesel engines developed for premium high-performance cars, as well as on the best knowledge of the authors. The operating parameters in terms of intake -- exhaust conditions and injection strategy were properly parametrized in order to find the boundary conditions suitable for the desired specific power target. The paper discusses the system sensitivity to the boundary conditions of the charging and exhaust systems, and develops a balanced set of targets for the complete system based on thermo-structural, fluid-dynamic and efficiency considerations. The tests confirmed the benefits of the employment of very high fuel injection pressures as a way to face with the trade-off of combining high performance and fuel economy for light-duty high-speed diesel engines.
•The exhaust detritiation system using a polymer membrane was operated for 2.5 y.•There were no serious malfunctions after starting the operation.•The operating data indicates that the system has a ...potentially higher detritiation factor than DF = 103.
An exhaust detritiation system using commercially available hollow fiber-type polyimide membrane modules, a PM system, was installed and applied for tritium recovery in the vacuum vessel purge gas of a large fusion test device. The PM system is operated annually and there were no serious malfunctions after starting the operation for approximately 2.5 y. The continuous recovery of tritiated water without the heating operation and the switching of valves as well as the regeneration operation of molecular sieves, was demonstrated. The tritium in the process gas was successfully recovered by the PM system even though the average tritium concentration at the inlet of the PM system was less than the order of 10−3 Bq/cm3. The detritiation factor and tritium recovery ratio were greater than 103 and 0.97, respectively. The tritium concentration at the outlet of the PM system was maintained in the order of 10−6 Bq/cm3 irrespective of the tritium concentration at the inlet of the PM system. Thus, the operating data indicates that the PM system has a potentially higher detritiation factor than DF = 103.
Scheme of the Trigeneration System – An energetic and economic assessment.
Display omitted
•Thermoeconomic model to assess the feasibility of trigeneration systems was made.•A case study based on the ...energy demands of an ice cream factory was analyzed.•Energy utilization factor of the trigeneration system increases approximately to 74%.•Case 3 shows good financial return since 26.32% IRR and 3 year of payback was obtained.
This work presents an energy and financial analysis of an energy trigeneration system, in which electricity, steam and chilled water are produced simultaneously using natural gas as source of input. The system consists of an internal combustion engine, a domestic heat recovery unit, a LiBr/H2O absorption chiller to produce chilled water and a recovery boiler to produce steam. In this system, the exhaust gases produced by the engine are used to drive an absorption chiller through a heat exchanger and can also drive a recovery boiler. According to the final results, and considering total engine load, the overall system of trigeneration presented an energy utilization factor of 74%, with average electricity, cooling and heating production of 214.1 kW, 35.7 kW and 162.1 kW, respectively. A case study based on the energy demands of an ice cream industry is presented in this article for the financial analysis of the system. In order to determine the best configuration for the company, the one that presented a higher financial return, three scenarios were developed for the application of cogeneration or trigeneration in the company. They were analyzed on the financial methodology of calculation of return on investment, using as parameters the net present value (NPV), the internal rate of return (IRR) and the simple payback, based on an interest rate of 6.4% and a project period of 10 years. The first two scenarios created were not economically viable, presenting a negative NPV. However, scenario 3 presented good financial return result, presenting a NPV of $ 269,390.40, a 26.32% IRR and a 3.4 year simple payback, making it the best financial scenario for the company. The results of this work indicate that the configuration proposed in scenario 3 provides several useful results with high efficiency and a good financial return for the company.
Copper manganese oxide (CuMn 2 O 4 ) was introduced into the nanoarray-based monolithic catalysts system for advanced exhaust after-treatment. Through scalable and cost-effective hydrothermal ...reactions, nanosheet layers of copper manganese oxide were uniformly coated onto the manganese oxide nanoarrays (HM-PCR), which were grown on the cordierite honeycomb monoliths. The core nanoarray support, HM-PCR, a well-defined array architecture for active material deposition, contributed to an increase of open surface area and thus enhanced catalytic oxidation performance. The CuMn 2 O 4 coated nanoarray-based catalyst, NA-CuMn 2 O 4 , shows efficient 90% propane (C 3 H 8 ) conversion at around 400 °C, which is 50 °C and 75 °C lower than CuMn 2 O 4 wash-coated catalyst (WC-CuMn 2 O 4 ) and Pd loaded catalyst (WC-Pd), respectively. Compared to monolithic catalysts with a traditional alumina support, the benefit of nanoarray morphology was demonstrated by correlating the variation of surface area to the reactivity. The incorporation of cobalt ions was found to increase the specific surface area and thus enhance C 3 H 8 conversion of CuMn 2 O 4 . The CuMn 2 O 4 /MnO 2 nanoarray-based monoliths are promising types of emission control devices.
•The switch modes of fully enclosed Platform Screen Doors are obtained.•The modes prove that reasonable opening of the end doors is beneficial to control smoke.•The air exhaust system in the platform ...floor and tunnel is critical during emergency fires.•Switch mode analysis helps to find solutions for smoke control in underground metro station.
Fire is a major hazard in an underground metro station. Faced with challenges from fires in metro stations, platform screen doors (PSDs) are usually installed on the ground, which are critical to passengers’ life safety. In case of a platform fire, in order to get optimal control of smoke and provide better environmental conditions for evacuation, the operation of those PSDs needs to be systematically studied. In this work, Fire Dynamics Simulator (FDS) was used to investigate the smoke exhaust effect during fires in underground island-type platform under twenty-four different PSD switch modes. The parameters that influence evacuee life safety, such as temperature and visibility contours at the stair entrance, were computed to compare the performance of different switch modes for the underground metro station with fully enclosed PSDs. The simulation results show that the optimization of the PSD switch modes in the underground metro station depends significantly on the cooperation of the air supply system in the lobby floor, the air exhaust system in the platform floor and the tunnel. Three potential fire sources in the platform floor have been studied. When the fire source is in the center of the subway platform, it is better to open four end doors and 12 PSDs in one side, or open all PSDs in one side during the developing stage of fire. As for its stable stage of fire, it is better to open four end doors or all PSDs in one side. When the fire source is near the ends of the platform, it is better to open all PSDs in one side or open four end doors during the developing stage of fire. As for its stable stage of fire, it is better to open all PSDs in both sides near the fire sources. Those results can provide some guidance to the smoke control design in case of platform fire in the underground metro station.
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