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•A novel exhaust heat recovery system was devised and modified on a vehicle exhaust channel for waste heat utilization.•The vehicle economy and emissions test under cold start NEDC ...were carried out on the chassis dynamometer.•Lower average ambient temperature increases the cold start running duration.•The fuel economy has been improved slightly by 2.8% with EHRS actuation over NEDC at −7 °C.•A new theory was proposed to reveal the mechanism of NOX formation under cold start.
Over the decades, unremitting efforts have been made to achieve energy conservation and emission reduction throughout the world. While for a vehicle engine, a great deal of the fuel energy is wasted as exhaust heat. Based on a novel exhaust heat recovery system devised and modified on a vehicle exhaust channel, the chief objective of this study is to improve the vehicle economy and emissions under cold start. Therefore, a detailed experimental investigation was conducted on the chassis dynamometer (CD) under cold start NEDC at 25 °C and −7 °C temperatures. And the method of comparative analyses of the coolant temperature, gasoline fuel consumption and exhaust emissions including total hydrocarbon (THC), carbon monoxide (CO) and nitrogen oxide (NOX) have been obtained to reveal the effects of EHRS on vehicle economy and emissions under cold start. The results show that, since the coolant temperature can be quickly increased with EHRS to shorten engine warm-up time under cold start, vehicle economy is enhanced during NEDC. Moreover, the device of EHRS can effectively alleviate the combustion deterioration and wall frame quenching effect in the cylinders under cold start, which greatly decreases THC emission. Although the excess air coefficient cannot be changed by EHRS, it can improve the combustion environment in cylinders, which contributes to the reduction of CO emission. It is unexpected to find that NOX emission is also decreased with EHRS actuation, which can be explained by a new theory called Fenimore mechanism. All these aims to provide helpful preliminary work for vehicles to meet the upcoming stringent limit of the real driving emission (RDE) of CHINA 6.
Reducing greenhouse gas and pollutant emissions is one of the most stringent priorities of our society to minimize their dramatic effects on health and environment. Natural gas (NG) engines, in ...particular at lean conditions, emit less CO2 in comparison to combustion engines operated with liquid fuels but NG engines still require emission control devices for NOx removal. Using state‐of‐the‐art technologies for selective catalytic reduction (SCR) of NOx with NH3, we evaluated the interplay of the reducing agent NH3 and formaldehyde, which is always present in the exhaust of NG engines. Our results show that a significant amount of highly toxic hydrogen cyanide (HCN) is formed. All catalysts tested partially convert formaldehyde to HCOOH and CO. Additionally, they form secondary emissions of HCN due to catalytic reactions of formaldehyde and its oxidation intermediates with NH3. With the present components of the exhaust gas aftertreatment system the HCN emissions are not efficiently converted to non‐polluting gases. The development of more advanced catalyst formulations with improved oxidation activity is mandatory to solve this novel critical issue.
HCN formation over common SCR catalysts: Natural gas engines emit less CO2 in comparison to common liquid fuel combustion engines and are therefore an attractive alternative. Nevertheless, they still require emission control devices for NOx removal. As HCHO is present in the exhaust, this study was focused on the interplay of HCHO and other compounds of an SCR gas mixture and revealed the formation of HCN over a broad variety of common NH3‐SCR catalysts.
Member countries of the European Union have released targets to reduce carbon dioxide emissions by 80% by the year 2050. Energy use in buildings is a major source of these emissions, which is why ...this study focused on the cost-optimal renovation of Finnish apartment buildings. Apartment buildings from four different construction years (pre-1976, 1976-2002, 2003-2009 and post-2010) were modelled, using three different heating systems: district heating, ground-source heat pump and exhaust air heat pump. Multi-objective optimisation was utilised to find the most cost-effective energy renovation measures. Most cost-effective renovation measures were ground-source heat pumps, demand-based ventilation and solar electricity. Additional thermal insulation of walls was usually too expensive. By performing only the cost-effective renovations, the emissions could be reduced by 80%, 82%, 69% and 68%, from the oldest to the newest buildings, respectively. This could be done with the initial investment cost of 296, 235, 115 and 104 €/m
2
, respectively.
This paper presents the development and experimental study of an ammonia water absorption refrigeration prototype for waste heat utilization of diesel engine exhaust. Side cooling rectification and ...side heating generation are designed to achieve desirable heat matching for better internal heat recovery thus improving the system performance. An active open heat pipe method is applied for taking the exhaust heat to make the heat input stable. The condensation and absorption processes are combined in one unit and cooled by circulated precooled solution. Small diameter tube bundle heat exchangers with large specific surface area are employed for all components. Both the features make the system bulk small. The experimental results show that the operation of the system is reliable with a sharp variation of the exhaust condition. The prototype produces cooling capacity of 33.8 kW and the system thermal COP reaches 0.53 under the test conditions that the temperatures of the cooling water, secondary refrigerant and exhaust inlet are 26.1 °C, −15.2 °C and 567 °C, respectively. The novel design of the prototype is proved to be valid and its concept can be extended to other applications.
•Side cooling rectification and side heating generation are designed.•An active open heat pipe technology is used for taking the exhaust heat.•Small channel tube bundle heat exchangers are employed.•The prototype produces cooling capacity of 33.8 kW and thermal COP of 0.53.
To succeed on the aim of achieving a carbon-neutral energy system, improving the efficiency of waste heat recovery is an important technique route. However, most of available heat sources in ...energy-intensive industries and transport sectors always present fluctuating nature that prohibits the safe and efficient operation of organic Rankine cycle (ORC) based waste heat recovery systems. Hereby, this study proposes a novel ORC system integrated with latent thermal energy storage (LTES), using LTES to reduce the thermal power fluctuations of engine exhaust and improve the safety performance of downstream ORC system. A dual-model test bench including the traditional basic ORC and ORC-LTES directly driven by engine exhaust is designed and established. The dynamic performance of basic ORC and ORC-LTES is experimentally investigated and compared under different step-change and cyclic engine conditions. The experimental results indicate that the existing of LTES can significantly reduce the fluctuating range of exhaust temperature at the evaporator inlet under both step-change and cyclic engine conditions. Under step-change engine conditions, ORC-LTES can completely resist the sudden reduction of exhaust temperature and mass flowrate under small step-change ratio of engine load, and the superheat degree of ORC-LTES lasts much longer time to drop to zero than the basic ORC under larger step-change ratio of engine load, while superheat degree of the basic ORC fast drops to zero under different step-change engine conditions. Under cyclic engine condition, ORC-LTES keeps safely operating all the time while the basic ORC has to stop working in each period, in addition, the net power and thermal efficiency of ORC-LTES are 23.5% and 23.2% higher than that of the basic ORC respectively.
•A novel ORC system integrating with latent thermal energy storage is proposed 79.•A dual-mode ORC test rig driven by transient engine exhaust is designed and built.•Different step-change and cyclic engine operating conditions are considered.•Dynamic performance of basic ORC and proposed ORC-LTES are experimentally compared.•Net power and thermal efficiency of ORC-LTES are 23.5% and 23.2% higher than basic ORC.
•Waste energy from a non-solar multi-stage recuperative Brayton cycle is recovered.•Feasibility of waste energy recovery from intercooling and exhaust gas is evaluated.•Different organic Rankine ...cycles and supercritical CO2 power cycles are compared.•Waste energy recovery from intercooling and exhaust gas is an attractive option.•Waste energy recovery is currently more beneficial than solar hybridization.
Multi-stage gas turbine cycle configurations can greatly contribute to improve the economic and environmental aspects of gas turbine power plants. In the first part of this work, the hybridization of multi-stage recuperative Brayton power cycles with a solar power tower system that used a pressurized air receiver was evaluated. In this work, a detailed thermodynamic and economic analysis was conducted to evaluate the waste energy recovery from a non-solar multi-stage recuperative Brayton cycle configuration that showed the lowest levelized cost of electricity (LCOE) in the first part. A comparative analysis between different organic Rankine cycles (ORCs) and supercritical CO2 power cycles was conducted for waste energy recovery from both intercooling stages and the exhaust gas. After designing the systems, a transient analysis was conducted to consider the effect of off-design conditions on the cycles thermo-economic performance. The obtained results showed that waste energy recovery using an ORC is the most economical option. By recovering the available heat in intercooling and exhaust gas stages by ORCs that use Isobutane and Toluene as working fluids, respectively, an additional power of 3508 kW was generated. Also, thermal efficiency was increased from 53.6% to 59.9% and the LCOE was reduced from $57.80/MWh to $54.77/MWh. Overall, the results demonstrated that waste energy recovery from intercooling stages and exhaust gas of a multi-stage gas turbine power plant is an attractive option for improving its thermal and economic performance. Also, considering the high price of a solar power tower plant and the technological pressure and temperature limitation of a pressurized air receiver, waste energy recovery is a more practical and beneficial option at current time than hybridization with a solar power tower plant.
The European roadmap to the realisation of fusion energy has identified a number of technological and scientific challenges towards the development of a DEMO reactor. Mission 2 ‘Heat-exhaust systems’ ...includes the investigation of alternative divertor configurations such as the snowflake, X and super-X divertors as a reliable solution for the power exhaust problem. This paper, starting from the geometrical description of a conventional European DEMO scenario with an aspect ratio of 3.1 and a reference Single Null configuration, firstly illustrates the objectives, the figure of merits and the constraints considered in the design of alternative configurations. DEMO descriptions for Double Null, Snowflake, X-divertor and Super-X configurations optimizing the plasma shape, the machine geometry and the PF coil system will be proposed. A comparison of costs and benefits of the various configurations is given, with particular reference to the power exhaust issues.
This work aims to study exhaust flow pattern of one of the Three Wheeler Exhaust System (Bajaj RE Diesel Auto Rickshaw) in order to understand the exhaust characteristics, implications to ...surroundings, flow tendencies and exhaust dispersion at outlet. This work utilizes Finite Volume Computational Fluid Dynamics (CFD) Analysis which is performed using Solid Works Flow Simulation tool to analyse Autorickshaw Exhaust System Model developed using Proe Creo. The Model is created by measuring actual dimensions of the Exhaust System Components, neglecting all hangar positions as their contribution to thermal behaviour is negligible.
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The air curtain system can collect the dust particles from hard-to-seal sources, which proves to be a feasible method for satisfying the increasing dust prevention requirements in ...China. In this study, aiming at addressing the dust escape problem at the tobacco stem loading point in a tobacco factory, a rotational flow air curtain dust-collecting system with a size of 2m x 2m x 2m was used for dust collection. The dust-collecting characteristics using the original dust suction hood and the developed air curtain dust-collecting system were analyzed and compared. Results show that the external dust concentration when the original dust suction hood operated was as high as 83.65 mg/m3, with a dust-collecting efficiency of only 16.35 %, suggesting serious dust escape; after the use of the developed air curtain dust-collecting system, the dust-collecting efficiency reached up to 86.93∼94.76 % under the same operating conditions. By studying the influence of two factors, air curtain jet velocity and exhaust-to-pressure ratio, on the dust collection efficiency of the air curtain system, at an exhaust-to-pressure ratio of 0.8 and an air curtain jet velocity of 13.5 m/s, the corresponding dust-collecting efficiency reached a maximum of 94.76 %. The present test results confirmed a better application effect of the developed air curtain dust-collecting system than the original dust-collecting system at the industrial loading point. Using the developed air curtain dust-collecting system is mainly aimed at the dust source, reduce the dust in the workshop dissemination and dispersion that can lower the transmission path of COVID-19 via aerosol.
Mixed-potential type ammonia sensors based on yttria-stabilized zirconia are promising devices in NO
x
reducing system for high-temperature exhaust. However, selectivity is a critical issue that ...should be urgently addressed. Herein, a novel bilayer Cr
2
O
3
|In
2
O
3
sensing electrode (SE) was designed to improve the selectivity of the ammonia sensor, in which an additional Cr
2
O
3
layer was deposited on In
2
O
3
SE. The selectivity was examined in NH
3
, CO, NO and NO
2
. Finally, the sensor with the bilayer Cr
2
O
3
|In
2
O
3
SE exhibits an improvement of NH
3
selectivity at 600 °C, which is attributed to the Cr
2
O
3
layer catalysing the removal of CO and NO
x
before the gases reach the triple-phase boundaries (TPBs). Furthermore, the mixed-potential model of the NH
3
sensor with the bilayer SE was identified using the polarization curves obtained in different concentrations of NH
3
. Additionally, the proposed sensor displayed a good repeatability and resistances to CO
2
and H
2
O. This innovative bilayer Cr
2
O
3
|In
2
O
3
SE is expected to be applied in high-temperature NH
3
detection.
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