Zeolites for control of NO emissions: Opportunities and challenges

This paper details the experimental and numerical analysis of a combustion process for atmospheric swirl burners using methane with added ammonia as fuel. The research was carried out for lean methane–air mixtures, which were doped with ammonia up to 5% and preheated up to 473 K. A flow with internal recirculation was induced by burners with different outflow angles from swirling blades, 30° and 50°, where tested equivalence ratio was 0.71. The NO and CO distribution profiles on specified axial positions of the combustor and the overall emission levels at the combustor outlet were measured and compared to a modelled outcome. The highest values of the NO emissions were collected for 5% NH3 and 50° (1950 ppmv), while a reduction to 1585 ppmv was observed at 30°. The doubling of the firing rates from 15 kW up to 30 kW did not have any great influence on the overall emissions. The emission trend lines were not proportional to the raising share of the ammonia in the fuel. 3D numerical tests and a kinetic study with a reactor network showed that the NO outlet concentration for swirl flame depended on the recirculation ratio, residence time, wall temperature, and the mechanism used. Those parameters need to be carefully defined in order to get highly accurate NO predictions—both for 3D simulations and simplified reactor-based models.

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The effect of after-treatment techniques on the correlations between driving behaviours and NO emissions of a passenger cars

Journal of Cleaner Production ◽

10.1016/j.jclepro.2020.125647 ◽

2021 ◽

Vol 288 ◽

pp. 125647

Author(s):

Jianbing Gao ◽

Haibo Chen ◽

Ye Liu ◽

Ying Li ◽

Tiezhu Li ◽

...

Keyword(s):

Passenger Cars ◽

Treatment Techniques ◽

No Emissions

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Prediction of gaseous pollutant emissions from a spark-ignition direct-injection engine with gas-exchange simulation

International Journal of Engine Research ◽

10.1177/14680874211005053 ◽

2021 ◽

pp. 146808742110050

Author(s):

Stefania Esposito ◽

Lutz Diekhoff ◽

Stefan Pischinger

Keyword(s):

Gas Exchange ◽

Combustion Chamber ◽

Direct Injection ◽

Spark Ignition ◽

Operating Conditions ◽

Pollutant Emissions ◽

Operating Parameters ◽

Gaseous Pollutant ◽

Fuel Ratio ◽

No Emissions

With the further tightening of emission regulations and the introduction of real driving emission tests (RDE), the simulative prediction of emissions is becoming increasingly important for the development of future low-emission internal combustion engines. In this context, gas-exchange simulation can be used as a powerful tool for the evaluation of new design concepts. However, the simplified description of the combustion chamber can make the prediction of complex in-cylinder phenomena like emission formation quite challenging. The present work focuses on the prediction of gaseous pollutants from a spark-ignition (SI) direct injection (DI) engine with 1D–0D gas-exchange simulations. The accuracy of the simulative prediction regarding gaseous pollutant emissions is assessed based on the comparison with measurement data obtained with a research single cylinder engine (SCE). Multiple variations of engine operating parameters – for example, load, speed, air-to-fuel ratio, valve timing – are taken into account to verify the predictivity of the simulation toward changing engine operating conditions. Regarding the unburned hydrocarbon (HC) emissions, phenomenological models are used to estimate the contribution of the piston top-land crevice as well as flame wall-quenching and oil-film fuel adsorption-desorption mechanisms. Regarding CO and NO emissions, multiple approaches to describe the burned zone kinetics in combination with a two-zone 0D combustion chamber model are evaluated. In particular, calculations with reduced reaction kinetics are compared with simplified kinetic descriptions. At engine warm operation, the HC models show an accuracy mainly within 20%. The predictions for the NO emissions follow the trend of the measurements with changing engine operating parameters and all modeled results are mainly within ±20%. Regarding CO emissions, the simplified kinetic models are not capable to predict CO at stoichiometric conditions with errors below 30%. With the usage of a reduced kinetic mechanism, a better prediction capability of CO at stoichiometric air-to-fuel ratio could be achieved.

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Experimental Investigation of Oxygen Carrier Aided Combustion (OCAC) with Methane and PSA Off-Gas

Applied Sciences ◽

10.3390/app11010210 ◽

2020 ◽

Vol 11 (1) ◽

pp. 210

Author(s):

Viktor Stenberg ◽

Magnus Rydén ◽

Tobias Mattisson ◽

Anders Lyngfelt

Keyword(s):

Oxygen Carrier ◽

Silica Sand ◽

Fuel Conversion ◽

Fuel Gas ◽

Bed Temperature ◽

Bed Materials ◽

Distribution Plate ◽

Bed Material ◽

Gas Conversion ◽

No Emissions

Oxygen carrier aided combustion (OCAC) is utilized to promote the combustion of relatively stable fuels already in the dense bed of bubbling fluidized beds by adding a new mechanism of fuel conversion, i.e., direct gas–solid reaction between the metal oxide and the fuel. Methane and a fuel gas mixture (PSA off-gas) consisting of H2, CH4 and CO were used as fuel. Two oxygen carrier bed materials—ilmenite and synthetic particles of calcium manganate—were investigated and compared to silica sand, an in this context inert bed material. The results with methane show that the fuel conversion is significantly higher inside the bed when using oxygen carrier particles, where the calcium manganate material displayed the highest conversion. In total, 99.3–99.7% of the methane was converted at 900 °C with ilmenite and calcium manganate as a bed material at the measurement point 9 cm above the distribution plate, whereas the bed with sand resulted in a gas conversion of 86.7%. Operation with PSA off-gas as fuel showed an overall high gas conversion at moderate temperatures (600–750 °C) and only minor differences were observed for the different bed materials. NO emissions were generally low, apart from the cases where a significant part of the fuel conversion took place above the bed, essentially causing flame combustion. The NO concentration was low in the bed with both fuels and especially low with PSA off-gas as fuel. No more than 11 ppm was detected at any height in the reactor, with any of the bed materials, in the bed temperature range of 700–750 °C.

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Residual-effected homogeneous charge compression ignition at a low compression ratio using exhaust reinduction

International Journal of Engine Research ◽

10.1243/146808703322223306 ◽

2003 ◽

Vol 4 (3) ◽

pp. 163-177 ◽

Cited By ~ 53

Author(s):

P. A. Caton ◽

A. J. Simon ◽

J. C. Gerdes ◽

C. F. Edwards

Keyword(s):

Compression Ratio ◽

Equivalence Ratio ◽

Homogeneous Charge Compression Ignition ◽

Compression Ignition ◽

Single Digit ◽

Hcci Combustion ◽

Actuation System ◽

Order Of Magnitude ◽

No Emissions ◽

Homogeneous Charge

Studies have been conducted to assess the performance of homogeneous charge compression ignition (HCCI) combustion initiated by exhaust reinduction from the previous engine cycle. Reinduction is achieved using a fully flexible electrohydraulic variable-valve actuation system. In this way, HCCI is implemented at low compression ratio without throttling the intake or exhaust, and without preheating the intake charge. By using late exhaust valve closing and late intake valve opening strategies, steady HCCI combustion was achieved over a range of engine conditions. By varying the timing of both valve events, control can be exerted over both work output (load) and combustion phasing. In comparison with throttled spark ignition (SI) operation on the same engine, HCCI achieved 25–55 per cent of the peak SI indicated work, and did so at uniformly higher thermal efficiency. This was accompanied by a two order of magnitude reduction in NO emissions. In fact, single-digit (ppm) NO emissions were realized under many load conditions. In contrast, hydrocarbon emissions proved to be significantly higher in HCCI combustion under almost all conditions. Varying the equivalence ratio showed a wider equivalence ratio tolerance at low loads for HCCI.

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