Modeling of NOx Emissions Using a Super-Extended Zel’dovich Mechanism

2003 ◽  
Author(s):  
Huateng Yang ◽  
Sundar R. Krishnan ◽  
Kalyan K. Srinivasan ◽  
K. Clark Midkiff
Keyword(s):  
Diesel Engine ◽  
Reaction Scheme ◽  
Combustion Model ◽  
Nox Emissions ◽  
Si Engine ◽  
Nox Formation ◽  
Natural Gas Engines ◽  
Lean Combustion ◽  
Temperature And Pressure ◽  
The Difference

A kinetic model for NOx production has been developed to predict NOx emissions. The reaction scheme is a modified super-extended Zel’dovich mechanism (SEZM), which includes 43 reactions and 20 species instead of just the three reactions typically used in the extended Zel’dovich mechanism. The NOx emissions predicted by both mechanisms are compared using two separate models. First, a theoretical investigation of the two mechanisms is made for an SI engine using prescribed temperature and pressure histories. Then each of the two mechanisms is combined with a phenomenological combustion model for a single-cylinder Caterpillar 3400 series diesel engine to calculate the NOx emissions. The predictions from both mechanisms are compared with experimental results. It is shown that the SEZM can predict NOx emissions more accurately than the extended Zel’dovich mechanism. Results show that the SEZM increases the predicted NOx by about 25 percent. The difference between the two models is more pronounced for lean combustion, in which NO2 and NH play an important role in the NOx formation. In addition, the effects of several parameters on diesel engine NOx production are investigated. The super-extended Zel’dovich mechanism for NOx formation is expected to be more appropriate for lean combustion, such as in diesel or natural gas engines and other engines that typically operate at lean conditions.

Cycle-to-Cycle NO and NOx Emissions From a HSDI Diesel Engine

2018 ◽  
Author(s):  
Felix Leach ◽  
Martin Davy ◽  
Mark Peckham
Keyword(s):  
Diesel Engine ◽  
High Speed ◽  
Nox Emissions ◽  
Nox Formation ◽  
Reduction Techniques ◽  
Light Duty ◽  
Peak Cylinder Pressure ◽  
Crank Angle ◽  
The Difference ◽  
Hsdi Diesel Engine

Engine-out NOx emissions from diesel engines continue to be a major topic of research interest. While substantial understanding has been obtained of engine-out (i.e. before any aftertreatment) NOx formation and reduction techniques, not least EGR which is now well established and fitted to production vehicles, much less data are available on cycle resolved NOx emissions. In this work, crank-angle resolved NO and NOx measurements have been taken from a high-speed light duty diesel engine at test conditions both with and without EGR. These have been combined with 1D data of exhaust flow and this used to form a mass average of NO and NOx emissions per cycle. These results have been compared with combustion data and other emissions. The results show that there is a very strong correlation (R2 > 0.95) between the NOx emitted per cycle and the peak cylinder pressure of that cycle. In addition, the crank-angle resolved NO and NOx measurements also reveal that there is a difference in NO : NO2 ratio (where NO2 is assumed to be the difference between NO and NOx) during the exhaust period, with proportionally more NO2 being emitted during the blowdown period compared to the rest of the exhaust stroke.

Cycle-to-Cycle NO and NOx Emissions From a HSDI Diesel Engine

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Felix Leach ◽  
Martin Davy ◽  
Mark Peckham
Keyword(s):  
Diesel Engine ◽  
High Speed ◽  
Nox Emissions ◽  
Nox Formation ◽  
Reduction Techniques ◽  
Peak Cylinder Pressure ◽  
Crank Angle ◽  
The Difference ◽  
Hsdi Diesel Engine ◽  
Gas Recirculation

Engine-out NOx emissions from diesel engines continue to be a major topic of research interest. While substantial understanding has been obtained of engine-out (i.e., before any aftertreatment) NOx formation and reduction techniques, not least exhaust gas recirculation (EGR) which is now well established and fitted to production vehicles, much less data are available on cycle resolved NOx emissions. In this work, crank-angle resolved NO and NOx measurements have been taken from a high-speed light duty diesel engine at test conditions both with and without EGR. These have been combined with 1D data of exhaust flow, and this used to form a mass average of NO and NOx emissions per cycle. These results have been compared with combustion data and other emissions. The results show that there is a very strong correlation (R2 > 0.95) between the NOx emitted per cycle and the peak cylinder pressure of that cycle. In addition, the crank-angle resolved NO and NOx measurements also reveal that there is a difference in NO : NO2 ratio (where NO2 is assumed to be the difference between NO and NOx) during the exhaust period, with proportionally more NO2 being emitted during the blowdown period compared to the rest of the exhaust stroke.

scholarly journals Effects of Incomplete Premixing on NOx Formation at Temperature and Pressure Conditions of LP Combustion Turbines

1997 ◽  
Author(s):  
Teodora Rutar ◽  
Scott M. Martin ◽  
David G. Nicol ◽  
Philip C. Malte ◽  
David T. Pratt
Keyword(s):  
Air Temperature ◽  
Chemical Reactor ◽  
Nox Emissions ◽  
Reactor Model ◽  
Nox Formation ◽  
Air Temperatures ◽  
Primary Zone ◽  
Lean Premixed ◽  
Temperature And Pressure

A probability density function/chemical reactor model (PDF/CRM) is applied to study how NOx emissions vary with mean combustion temperature, inlet air temperature, and pressure for different degrees of premixing quality under lean-premixed (LP) gas turbine combustor conditions. Inlet air temperatures of 550, 650 and 750 K, and combustor pressures of 10, 14 and 30 atm are examined in different chemical reactor configurations. Primary results from this study are: incomplete premixing can either increase or decrease NOx emissions, depending on the primary zone stoichiometry; an Arrhenius-type plot of NOx emissions may have promise for assessing the premixer quality of lean-premixed combustors; and decreasing premixing quality enhances the influence of inlet air temperature and pressure on NOx emissions.

Detailed Evaluation of a New Semi-Empirical Two-Zone NOx Model by Application on Various Diesel Engine Configurations

2012 ◽  
Author(s):  
Stelios Provataris ◽  
Nicholas Savva ◽  
Dimitrios Hountalas
Keyword(s):  
Diesel Engine ◽  
Accurate Estimation ◽  
Operating Parameters ◽  
Nox Emissions ◽  
Heavy Duty ◽  
Nox Formation ◽  
Light Duty ◽  
Physically Based ◽  
Di Diesel Engine ◽  
Semi Empirical

Over a significant period of time, efforts have been made towards a valid and accurate estimation of DI diesel engine NOx emissions. Considering the fact that experiments have a high cost in both time and money, modelling approaches have been developed in an effort to overcome these issues. It is well known that accuracy in the prediction of NOx emissions lies specifically on the accurate estimation of local temperature and O2 histories inside the combustion chamber that govern NOx formation, fulfilled by an accurate estimation of the combustion mechanism. To account for the actual effect of parameters that control NOx formation and overcome inefficiencies introduced from existing purely empirical models or artificial neural networks, valid only on the combustion systems for which they were developed [1], an alternative solution is the introduction of physically based semi-empirical models. Towards this direction, in the present work is presented and evaluated a new modelling approach, based on the combustion rate obtained from the measured cylinder pressure trace using Heat Release Rate Analysis. The model used is a semi-empirical two-zone one which makes use of the estimated elementary fuel mass burnt at each crank angle interval. The combustion process is considered to be adiabatic, while chemical dissociation is also considered. With this approach, temperature distribution throughout the combustion chamber is considered for, together with its evolution during the engine cycle. In addition, O2 availability is also considered for through the calculated charge composition. The result is an extremely fast computational model, combining the advantages of both empirical and physically based ones. In the present work is given a detailed validation of the model, from its application on two different types of diesel engines: a heavy-duty DI diesel engine and a light-duty DI diesel engine with pilot fuel injection. A significant number of cases where tested for both engine configurations, considering different operation points and variation of operating parameters, such as rail pressure and EGR. The twelve points of the European Stationary Cycle (ESC) were covered for the case of the heavy duty DI diesel engine, whilst for the light-duty DI engine a total number of forty-six operating points was studied. For both engine configurations the model reveals a very good predictive ability, considering for the effect of all operating parameters examined on NOx emissions. However, there is potential for improvement and development on its physical base for even more accurate predictions. The merits of good accuracy in prediction trends with varying engine operating parameters — even without calibration — and low computational time establish a potential for model use in engine development, optimization studies and model based control applications.

Influence of Ignition Timing and EGR on the NOx Emission and the Performance of an SI Engine Fueled With Hydrogen

2015 ◽  
Author(s):  
Hassan A. Khairallah ◽  
Warren S. Vaz ◽  
Umit O. Koylu
Keyword(s):  
Hydrogen Oxidation ◽  
Engine Performance ◽  
Nox Emission ◽  
Nox Emissions ◽  
Ignition Timing ◽  
Si Engine ◽  
Nox Formation ◽  
Performance And Emission ◽  
Conflicting Objectives ◽  
Engine Power

Exhaust gas recirculation (EGR) and ignition timing have strong effects on engine performance and exhaust emissions. In the present study, detailed chemical reactions with 29 steps of hydrogen oxidation with additional nitrogen oxidation reactions were coupled with an advanced CFD code to investigate the engine performance and emission characteristics of a SI engine fueled with hydrogen. The NOx formation within the engine was computed using the extended Zeldovich mechanism with parameters adjusted for a carbon-free fuel such as hydrogen. The computational results were validated against experimental results with equivalence ratio of 0.84 and fixed ignition timing at crank angle of 5° BTDC (before top dead center). The simulations were then employed to examine the effects of EGR and ignition timing on the engine performance and NOx formation and emission. The EGR ratio was varied between 5% and 15% while the ignition timings considered were 5°, 10°, 15°, and 20° BTDC. It was found that NOx emission increased with advancing the ignition timing away from TDC while the indicated engine power showed an increasing trend with further advancing the ignition timing. Higher indicated mean effective pressure (IMEP) and indicated thermal efficiency were obtained with an advanced ignition timing of 20° BTDC. The model was also run with three different EGR ratios of 5%, 10% and 15% with fixed ignition timing at 5° BTDC. The simulation results quantified the reduction in NOx and the indicated engine power with the increase in the EGR ratio. The computations were consistent with the hypothesis that the combustion duration increases with the EGR ratio. Finally, the maximization of engine power and minimization of NOx emissions were considered as conflicting objectives. The different data points were plotted in the objective space. Using the concept of “knee”, (5° BTDC, 0% EGR) was selected as the optimal operating point representing the best trade-off between maximum engine power and minimum NOx emissions.

Nitrogen Oxides Reduction Effect and the Influence Mechanism of Exhaust Valve Lift on a Two-Stroke Marine Diesel Engine

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Lijiang Wei ◽  
Anmin Wu ◽  
Jie Liu ◽  
Mingliang Zhong ◽  
Xuebai Wang
Keyword(s):  
Diesel Engine ◽  
Nitrogen Oxides ◽  
Exhaust Valve ◽  
Marine Diesel Engine ◽  
Nox Emissions ◽  
Exhaust Gas ◽  
Nox Formation ◽  
Influence Mechanism ◽  
Marine Diesel ◽  
Reduction Effect

For the two-stroke marine diesel engine, the action of exhaust valve has a significant impact on scavenging and combustion processes and ultimately affects the engine performances and emissions. In order to reduce nitrogen oxides (NOx) emissions of a two-stroke marine diesel engine, different exhaust valve lifts (EVLs) were achieved by computational fluid dynamics simulation method in this study. The NOx reduction effect and influence mechanism of EVL on a two-stroke marine diesel engine were investigated in detail. The results showed that the in-cylinder residual exhaust gas and the internal exhaust gas recirculation (EGR) rate gradually increased with the decreasing EVL. Although the total mass of charge enclosed in the cylinder did not change much, the composition changed gradually and the maximum internal EGR rate reached 13.17% in this study. The maximum compression pressure and combustion pressure both rose first and then decreased with the decreasing EVL. While the start of combustion and the maximum combustion temperature were basically unaffected by EVL, the indicated power of the engine was also not much impacted when the EVL was changed from increasing 10 mm to decreasing 20 mm. The indicated specific fuel consumption first declined slowly and then rose rapidly as the EVL reduction exceeded 20 mm. NOx emissions decreased monotonously with the decreasing EVL. The reduction of NOx formation rate and the amount of NOx formation mass mainly occurred at the middle and late stages of combustion for the downward moving of residual exhaust gas. NOx emissions were reduced by 12.57% without compromising other engine performances at medium-reduced EVL in this study. However, in order to further reduce NOx emissions at low EVLs, other measures may be needed to make the residual exhaust gas more evenly distributed during the initial stage of combustion.

NOx Emissions From a Diesel Engine Fueled With Natural Gas

1995 ◽  
Vol 117 (4) ◽  
pp. 290-296 ◽  
Author(s):  
Y. Tao ◽  
K. B. Hodgins ◽  
P. G. Hill
Keyword(s):  
Diesel Engine ◽  
Natural Gas ◽  
Ignition Delay ◽  
Substantial Reduction ◽  
Equilibrium Concentration ◽  
Nox Emission ◽  
Combustion Model ◽  
Injection Timing ◽  
Exhaust Pipe ◽  
Nox Emissions

The performance and emission characteristics of a single-cylinder two-stroke diesel engine fueled with direct injection of natural gas entrained with pilot diesel ignition enhancer have been measured. The thermal efficiency of the optimum gas-diesel operation was shown to exceed that of the conventional diesel at full load, but to be less at part load where the ignition delay was excessive. At high load, where the NOx emission problem is most serious, substantial reduction in NOx emission rate was obtained with delay of injection timing and also with use of exhaust gas recirculation. Measured cylinder pressures were used with a three-zone combustion model to determine ignition delay and the temperatures of the burned gas. The predicted NOx emissions based on equilibrium concentration of NO at the maximum burned gas temperature were found to correlate closely with exhaust pipe measurements of NOx.

scholarly journals Research on the Influence of Euro VI Diesel Engine Assembly Consistency on NOx Emissions

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5335
Author(s):  
Wei Yan ◽  
Tengyao Dou ◽  
Jinbo Wang ◽  
Na Mei ◽  
Guoxiang Li
Keyword(s):  
Experimental Data ◽  
Diesel Engine ◽  
Combustion Chamber ◽  
Nox Emission ◽  
Combustion Model ◽  
Nox Emissions ◽  
Assembly Tolerance ◽  
Nozzle Extension ◽  
Assembly Tolerance Variation ◽  
Chamber Diameter

The assembly consistency of a diesel engine will affect its nitrogen oxides (NOx) emission variation. In order to improve the NOx emissions of diesel engines, a study was carried out based on the assembly tolerance variation of the diesel engine’s combustion system. Firstly, a diesel engine which meets the Euro VI standards together with the experimental data is obtained. The mesh model and combustion model of the engine combustion system are built in the Converge software (version 2.4, Tecplot, Bellevue, DC, USA), and the experimental data is used to calibrate the combustion model obtained in the Converge software. Then, the four-factor and three-level orthogonal simulation experiments are carried out on the dimension parameters that include nozzle extension height, throat diameter, shrinkage diameter and combustion chamber depth. Through mathematical analysis on the experimental data, the results show that the variation of nozzle extension height and combustion chamber depth have a strong influence on NOx emission results, and the variation of combustion chamber diameter also has a weak influence on NOx production. According to the regression model obtained from the analysis, there is a quadratic function relating the nozzle extension height and NOx emissions and the amount of NOx increases with increasing nozzle extension height. The relationship between emission performance and size parameters is complex. In the selected size range, the influence of the variation of the chamber diameter on NOx is linear. The variation of the chamber depth also has an effect on NOx production, and the simulation results vary with the change of assembly tolerance variation. Thus, in the engine assembly process, it is necessary to strictly control the nozzle extension height and combustion chamber depth. The research results are useful to improve the NOx emission of diesel engine and provide a basis for the control strategy of selective catalytic reduction (SCR) devices.

CFD Analysis of NOx Formation in Waste-to-Energy Systems Using Detailed Chemical Kinetic Modeling

2012 ◽  
Author(s):  
Alex Frank ◽  
Marco J. Castaldi
Keyword(s):  
Three Dimensional ◽  
Chemical Kinetic ◽  
Waste To Energy ◽  
Combustion Model ◽  
Nox Emissions ◽  
Nox Formation ◽  
Chemical Kinetic Model ◽  
Small Impact ◽  
Detailed Chemical ◽  
No Emissions

This study was undertaken to better understand the governing processes and reaction conditions under which NOx is produced in Waste to Energy (WtE) boilers. A three dimensional CFD model was created and calculated using the GRI 3.0, 50 species, 309 step detailed chemical kinetic model (DCKM) for methane/ethane combustion. Model results for primary NOx emissions and other pollutants agree well with collected data, proving the fidelity of the model. NO was the primary pollutant accounting for approximately 99% of the total NOx emissions. Fuel bound nitrogen was found to be the main source of NO produced in the boiler with thermal and prompt mechanisms having lesser impacts. Three principal intermediates were identified in the formation of NO; NH, HNO, and NCO. The assumption of fuel nitrogen conversion to either NH3 or HCN is an unknown parameter that was shown to have a small impact on NO emissions, indicating that this is an area that should not be explored further in this continuing study. Furthermore, varying the boiler pressure had a small impact on final NO emissions, indicating that this is not a condition that should be considered for plant operation. The next phase of this research will include the development of a reduced DCKM in order to expedite the running of new scenarios for future studies as well as optimization of boiler geometry and combustion mixing to achieve the lowest possible NOx emissions.

Development and Validation of a Multi-Zone Combustion Model for Predicting Performance Characteristics and NOx Emissions in Large Scale Two-Stroke Diesel Engines

2009 ◽  
Author(s):  
Vasilios T. Lamaris ◽  
Dimitrios T. Hountalas ◽  
Theodoros C. Zannis ◽  
Stefanos E. Glaros
Keyword(s):  
Diesel Engine ◽  
Diesel Engines ◽  
Large Scale ◽  
Engine Performance ◽  
Performance Characteristics ◽  
Combustion Model ◽  
Combustion Mechanism ◽  
Nox Emissions ◽  
Predicting Performance ◽  
Pressure Trace

In the present study, an existing multi-zone combustion model has been modified and applied to predict the performance characteristics and the NOx emissions of a large-scale two-stroke diesel engine (i.e. 12.5 MW rated power). Initially, an attempt was made to examine whether the multizone model can predict with sufficient accuracy the main performance parameters of the stationary diesel engine, using input data from the shop tests (i.e. engine speed, fuel consumption and scavenging pressure at different engine loads). Hence, it was verified that the model is capable of describing the main performance characteristics of the engine with satisfactory accuracy (i.e. reference state). Further on, an experimental investigation was conducted on the specific engine, consisting of a series of performance and NOx emissions measurements that were conducted at constant speed and at three different engine loads. Then, the proposed model was applied at the present engine condition to evaluate its ability to predict the combustion mechanism using the measured cylinder pressure trace as basis for comparison. Furthermore, the predicted engine out NOx emissions were compared to measured values to examine if the model can estimate at least qualitatively the effect of engine load on them. From this combined theoretical and experimental analysis is revealed that the developed model is capable of adequately predicting both engine performance and NOx emissions of large-scale two-stroke diesel engines.

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