Flame Characteristics Research Articles

Comparative study on combustion and flame characteristics of NH3 dual-fuel engine under CI vs SI combustion modes

Ammonia can be used for engines to reduce carbon emissions, while its poor combustion performance limits commercial applications. Thus, combustion promotors are needed to improve the combustion properties of NH3. In this study, the combustion and flame characteristics of NH3-heptane dual-fuel engines under CI vs SI combustion modes are comparably studied. The initial flame formation and its development are addressed by high-speed direct photography, whereas simultaneous pressure acquisition is applied to quantify the engine performance. The results show N-heptane can significantly improve the combustion of NH3 under both SI and CI modes, while the effective energy fraction of N-heptane is beyond 30%. Besides, a critical direct injection timing exists for the effect of N-heptane on NH3 dual-fuel CI combustion, before/after which the combustion phase will delay. Flame images show that the color of ammonia-based fuel flame tends to feature an orange-yellow color. When comparing the SI and CI mode, the thermal efficiency of CI combustion is much higher because of the multipoint auto-ignition combustion in CI mode. Statistical analysis of flame shows that the early flame duration of CI mode is short and the corresponding cycle-to-cycle variation is low. More specifically, the flame of CI is nearly symmetrical distribution and the high probability is at the center, while that of SI is at the side.

Performance evaluation of throated downdraft gasifier using peanut shell and mango seed hull as a feedstock

Bioenergy, or energy derived from biomass, has the potential to displace fossil fuels in the near future due to its abundance, cleanliness, and carbon dioxide neutrality. From biomass thermochemical treatments, the release of syngas, which can be employed in various heat and power generation systems, makes gasification particularly alluring. When a syngas with little tar and impurity is required most of the time downdraft gasifiers are among the first gasification systems that are chosen. The current study aims to investigate the performance of a throated downdraft gasification system by using a model and experiments based on the characterization of pretreated biomass feedstock. Mango seed hull (MSH) and peanut shell (PS), two biomass wastes that were readily available locally, were used for the analyses. The producer gas generated with MSH has a composition of 18.34 % H2, 23.87 % CO, 14.83 % CO2, and 1.27 % CH4 in a wet basis. The calorific value was determined to be 4.89 MJ/Nm3. Similarly, the PG was produced with 9 mm PS pellets and 17.93 % H2, 24.43 % CO, 12.47 % CO2, and 1.22 % CH4 in a wet basis. The calorific value was found to be 4.96 MJ/Nm3. From the model for MSH the syngas composition in wet basis was found to be 22.38 % H2, 24.16 % CO, 8.43 % CO2, 0.24 % CH4, which shows how close the prediction of the model and the experimental results are, which is also similar for the PS. When MSH and 9 mm PS pellets were utilized, gas with good flame characteristics was produced. Additionally, the gasifier's overall performance for these feedstocks was favorable. Thus, MSH and PS are discovered to be good biomass feedstocks for producing syngas through biomass gasification based on the model and the conducted experiments.

Effects of Ammonia Addition on the Sooting Characteristics of Ethylene Counterflow Diffusion Flames with Oscillating Strain Rates

Effects of Ammonia Addition on the Sooting Characteristics of Ethylene Counterflow Diffusion Flames with Oscillating Strain Rates

Characteristics of Methane Explosion and Dynamic Response of Rock Mass in an H-Type Roadway with Different Ignition Sources.

Methane explosion is an undesired incident in the coal mining industry. Its high pressure wave can cause damage to the rock mass. This study numerically investigated the flame and wave transport characteristics of methane explosion with ignition sources at three different locations, and the corresponding dynamic response of the rock masses was discussed. The results showed that the flame propagation time is shortest when the ignition position is located at the center of the H-type roadway structure and the maximum overpressure decreases as the ignition position deviates from the center of the H-type roadway structure. When the ignition point is located at the center of the H-type roadway structure, the smallest total deformation of rock mass shows up with the highest maximum overpressure. In contrast, the largest total deformation appears when the ignition point is most away from the center due to the asymmetric distribution of the gas pressure exerted on both sidewalls of the rock masses. This work may provide insights into the understanding of deflagration propagation and the dynamic evolution of stresses under complex conditions.

A comparative study of combustion models for simulating partially premixed swirling natural gas flames

Combustion models are important for simulating chemical reaction properties and the turbulence-chemistry interaction (TCI) in combustion. However, little attention has been paid to the temperature/species distributions/velocity flow fields predicted by different combustion models and their requirements for mesh resolution. In the present work, a partially premixed swirling natural gas flame was separately simulated by two commonly-used combustion models in Reynolds-Averaged-Numerical-Simulation (RANS) simulations: the flamelet generated manifold (FGM) model and the eddy dissipation concept (EDC) model. It is found that the EDC model requires a higher quality of mesh than the FGM model from the temperature and species distributions perspective. It is possible for the EDC model to overpredict temperature, however, such a problem can be solved by improving the mesh quality. The combustion models do not differ obviously for the mesh refinement for flow fields. The further analysis find that the EDC model brings forward the reaction location (11 mm upstream than the FGM model). The weakened turbulence mixing and early chemical reactions make the EDC model derive discrepancies with measured values, resulting from the variations between its modelling principles and actual applications in the software ANSYS Fluent. The low turbulence viscosity makes the EDC model flame thicker. Overall, the FGM model showed better suitability and accuracy for such a partially-premixed swirling natural gas flame. This work connects the two common combustion models and partially premixed swirling flame characteristics in the RANS simulations, and highlights the effects on the temperature/species concentration/turbulence flow fields, in concerns of mesh resolution and reaction properties rather than sole applications, which can provide foundation for subsequent researchers.

Numerical analysis of the enrichment of CH4/H2 in ammonia combustion in a hot co-flow environment

A numerical investigation is conducted using OpenFOAM to study the characteristics of ammonia flames enriched with methane and hydrogen, influenced by a diluted co-flow (exhaust gas). The study aims to explore various flame characteristics, including fuel consumption, ignition delay time, lift-off height and position, temperature, and CO and NO emissions while maintaining a constant energy input of 5 kW. Non-stabilized flames are identified by analyzing the OH peak in the computational domain among ammonia flames enriched with CH4/H2 for different dilutions of O2 (6 %, 9 %, and 12 %). The study is structured into three stages of numerical simulations corresponding to stabilized flames: (1) no reaction, (2) reaction in the absence of O2, and (3) reaction with O2 to see the sole impact of the hot co-flow and local turbulence mixing on the primary cracking of ammonia. Furthermore, the rates of H2 and N2 formation resulting from the utilization of ammonia in the presence of hot co-flow are thoroughly examined. Additionally, the behavior of ammonia flames and CH4/H2-enriched ammonia flames under preheated air conditions (23 % O2) is analysed. Stable flames are observed in the co-flow at 12 % O2, displaying characteristics of Moderate or Intense Low-oxygen Dilution (MILD) combustion. Conversely, ammonia flames under preheated air conditions exhibit conventional flame behavior. Pure ammonia flames exhibit stronger temperature gradients and higher levels of CO and NO emissions. As the enrichment of NH3 with CH4/H2 increases, peak temperatures decrease while lift-off heights increase, indicating a transition towards more distributed flame structures. Notably, the instance with 40 % H2 enrichment exhibits lower NO emissions and a higher rate of ammonia consumption along with more distributive flame characteristics.

Experimental investigation on spray and flame characteristics of a marine diesel engine with single and double injection

Multiple injection is one of the advanced technologies employed in modern diesel engines to improve combustion efficiency, reduce pollutant emissions, and minimize combustion noise. The application of multiple injection in marine diesel engines differs from its use in vehicles or heavy-duty engines, as it is not commonly combined with Exhaust Gas Recirculation (EGR). However, there is a scarcity of studies specifically examining the combustion characteristics of medium-speed marine diesel engines utilizing multiple injection. Given the large space scale of marine diesel engine, a constant volume chamber with a visible diameter of 240 mm was used, and an injector with a nozzle diameter of 0.465 mm was employed in the experiment. The spray development and combustion process were recorded by Mie-scattering and flame natural luminosity imaging respectively. Both conventional and double injection combustion processes were analyzed in detail. The results show that although the liquid phase spray does not fully penetrate to the cylinder wall in marine diesel engines, the flame penetrates to the cylinder wall rapidly, the flame burns near the wall almost throughout the entire combustion duration. The combustion characteristics of the double injection are significantly different, the flame propagation speed of the pilot and main injection fuel is one-third to one-half of that of a single injection with a long duration. For single injection spray with long injection duration, the flame penetration velocity is determined by the sequential ignition velocity of the fuel. While the flame penetration velocity for sprays with short injection duration mainly depends on the jet penetration velocity. The investigation on the impact of dwell time, fuel distribution, and injection pressure on the combustion process of double injection also provides valuable insights for optimizing multiple injection strategies.

Effect of ferrocene as a combustion catalyst on the premixed combustion flame characteristics of Jatropha biodiesel

Fuel additives are widely used to optimize the combustion process, reduce the harmful emissions, and improve the performance of engines. Among the metal-based additives, ferrocene is soluble in most fuels, including biodiesel. Furthermore, it is easily available and has high stability, low toxicity, and high lipophilicity. It can evenly disperse in biodiesel without causing any change in the physicochemical properties. Therefore, it can serve as an effective combustion catalyst for biodiesel. In this study, the effect of ferrocene as a combustion catalyst on the pyrolysis and combustion performance of Jatropha biodiesel is investigated. The coupled technique of thermogravimetry-Fourier transform infrared spectroscopy-mass spectrometry (TG-FTIR-MS) is used to analyze the evolution characteristics of multicomponent gaseous products generated during the pyrolysis and high-temperature oxidation of Jatropha biodiesel (JB100) and Jatropha biodiesel + ferrocene (JBF). The laminar premixed combustion flame and pollutant emissions of JB100 and JBF are examined using a variety of techniques, including OH planar laser-induced fluorescence (OH-PLIF), flue gas analysis, spectral analysis, transmission electron microscopy, etc. The results reveal that after adding ferrocene, the activation energy for the pyrolysis reaction of JB100 decreases by 4.66 kJ/mol and the complete weight loss temperature decreases by 10 ℃. Further, the addition of ferrocene reduces the endothermic heat by 0.38 mW/mg during the initial stage of the high-temperature oxidation reaction of JB100, and the amounts of final products CO2 and H2O are increased. Compared with JB100, JBF shows an enhanced OH group intensity in the combustion flame and a lower soot spectral peak. Furthermore, compared with JB100, under JBF combustion, the pollutant PM2.5 emissions decrease by 13.3 %, PM10 emissions decrease by 13.2 %, PM> 10 particulate matter emissions decrease by 19.3 %, CO emissions decrease by 6.8 %, NOx emissions increase by 21.2 %, and the size of soot particles decreases by 20.8 %.

Study on the inhibition of hydrogen explosion pressure and flame propagation by trifluoroiodomethane

A 20L spherical device and a schlieren system were used to study the suppression effect of CF3I on the hydrogen explosion pressure and flame characteristics. The results show that CF3I can promote and inhibit the pressure parameters of hydrogen under lean fuel, but only inhibit the pressure parameters of hydrogen under equivalence ratios and rich fuel. Such as, φ = 0.6, adding 10 % CF3I, the maximum explosion pressure increased by 8.8 %. φ = 1, adding 5 % CF3I, the maximum explosion pressure decreased by 25 %. Different from the explosion pressure, the laminar burning velocity of hydrogen with different equivalence ratio decreases gradually with the increase of CF3I concentration. Numerical simulation was used to reveal the mechanism of CF3I inhibiting hydrogen. The results show that the concentration of active free radicals(H, O, OH) decreases with the increase of trifluoroiodomethane concentration. Further analysis on the rate of production and sensitivity of H free radicals found that R822 and R839 are the main generation reactions of H free radicals in the fluorine- and iodine-containing elemental reactions, and R1397, R1396, R1391 and R859 are the main consumption of H free radicals reaction. The elementary reaction with the greatest inhibitory effect on H free radicals is R1391, and the elementary reaction with the greatest promoting effect is R850.

Combustion instability and emission characteristics of spray flame under flue gas jet

In this paper, dry flue gas was injected into the combustion chamber in a jet pattern that collided diagonally to control the combustion instability of ethanol spray flame. The effects of jet flow rate, jet height, and jet temperature were experimentally studied. The results show that the closer the jet point is to the flame root, the better the control effect on the pressure oscillations is. And as the jet flow rate grows, the pressure damping also increases, reaching a maximum of 68.7 %. However, the CO emissions also reached the maximum level of 5020.8 mg/m3. Moreover, it is observed that the oscillation frequencies tend to shift to a higher frequency at a significant jet flow rate. The flame will also transition from a high-fat type to a compact type, forming a low-temperature zone at the tail. 80 ℃ is the optimal jet temperature, which is conducive to flame and sound field decoupling. At this temperature, the pressure oscillations can not only be well suppressed, but also the emissions of CO and NOx are at relatively low levels. The flue gas jet provides a solution to the combustion instability of liquid fuels, expanding its practical application.

Numerical simulation study on two-phase flow of thermal runaway evolution and jet fire of 18650 lithium-ion battery under thermal abuse

The influence of particles on the external jet flame generated by 18650 lithium-ion batteries during thermal runaway is considered. A model that employed multi-component Navier-Stokes equations to consider gas-phase flow, and used the Lagrangian method to consider solid particles, was applied to describe the mixing characteristics of the jet flames and particles generated by battery combustion. The related combustion process, with and without particles, was compared and analyzed, and the flow lines outside the battery were obtained. Moreover, the effect of particles on the concentration of combustion components and the elevation of flame height are discussed. The results show that particles reduce the generation of external vortices outside the battery, making the external airflow more stable. The particles reduce the rate of concentration decrease outside the core, leading to an increase in the overall flame height. In the early stage of battery combustion, the flame has not yet stabilized, and the total flame height with the particles is on average 1–2 times higher than that without them. This article demonstrates that particles have a significant impact on the jet flame characteristics and dynamic behavior during thermal runaway process of batteries, providing a reference for the safety evaluation of actual batteries.

Intermittency of Flame Structure and Thermo-Acoustic Behavior in a Staged Multipoint Injector Using Liquid Fuel

Abstract This study investigates the impact of the staging factor, the ratio between the fuel injected through the pilot stage and the multipoint injection, on the flame dynamic. The BIMER combustor is an atmospheric pressure rig equipped with two corotating swirling air injections (a fixed amount of around 87% of the air goes inside the multipoint stage) and two fuel injection paths for staged combustion. Liquid dodecane is injected with air preheated at 437 K with a global equivalence ratio of 0.6 and a thermal power of around 72 kW. The change of the staging factor from 100% (pilot-only injection) toward 0% (multipoint-only injection) generates changes in the flame-shape which bifurcates from an anchored V-flame into a lifted flame. This flame shape bifurcation appears at a staging of factor around 25%. Around this staging factor, one can witness multistable flames where the flame structure transits randomly between five different states. Processing microphone signals recorded in the chamber provides an understanding of the flame dynamics. The attached flame presents limited pressure fluctuations level at 270 Hz, while the lifted flame features high-pressure fluctuations at 323 Hz. The intermittency between the five states (including the two stable states) is investigated.

Effects of Damköhler Number on Lean Premixed Jet Flames in Crossflow Using Direct Numerical Simulation

ABSTRACT In the present work, lean premixed jet flames in crossflow were studied using direct numerical simulation to explore the effects of Damköhler numbers () on turbulence and flame characteristics. The configuration is based on an experiment, where a jet of lean premixed ethylene-air mixtures ( = 0.6) was injected into a hot vitiated crossflow. The case with a higher and lower Da is denoted as case Da+ and case Da-, respectively. It was found that the turbulence is weakened around the reaction zone of case . In contrast, the turbulence of case is barely influenced by heat release. The vorticity dynamics are examined with the enstrophy transport equation budget terms, and the viscous dissipation term is the main sink for both cases. The windward and leeward flame branches of case are dominated by auto-ignition and premixed flame propagation respectively, while the auto-ignition and flame propagation modes coexist on the leeward flame branch of case . The scalar gradient magnitude in the leeward branch is generally lower compared with the windward branch so that the flame is overall thicker. The normal strain rate is negative, which tends to enhance the scalar gradient, but it becomes positive on the leeward side of case , which is influenced by the alignment between the scalar gradient and the principal strain rates.

Turbulent Flame Speed and Flame Characteristics of Lean Premixed H2-CH4 Flames at Moderate Pressure Levels

Abstract Carbon dioxide emissions in gas turbine power generation can be reduced by adding an increasing amount of hydrogen to the existing natural gas-fueled combustion systems. To enable safe operation, more insight on how H2 addition affects turbulent flame speed and other important flame characteristics is needed. In this work, the investigation of hydrogen addition effects on certain flame properties has been carried out in a high-pressure axial-dump combustor at gas turbine relevant conditions. OH planar laser induced fluorescence (PLIF) was applied to retrieve flame front contours and turbulent flame speed. The results show that as the concentration of hydrogen in the fuel mixture increases, turbulent flame speed and flame characteristics change drastically. Two main regimes can be identified: From 0 to 50% vol. Hydrogen, the turbulent flame speed increases weakly in an almost linear fashion, while from 50% vol. to 100% vol. the trend sharply changes and the higher reactivity of hydrogen, combined with a lower Lewis number, cause thermal-diffusive instability and preferential diffusion effects to become increasingly strong, leading to very high burning rates. The presented results help to understand and to define the relevant modifications that are necessary to successfully operate gas turbine combustor systems with high H2 content fuels.

Statistical investigation of combustion and emission characteristics of biofuels according to their physical properties: A way to explore suitable alternative fuels

The Pollutant emissions and limited fossil fuel resources attracted researchers toward alternative fuels. Therefore, the combustion of liquid biofuels (as an alternative fuel) is gaining importance in research for the power generation sector for gas turbine engines and internal combustion engines. The physical properties of these fuels play an important role in the combustion characteristics (in terms of flame characteristics, emission characteristics, and flame temperature profile characteristics), and their experimental testing is costly. Considering the importance of research and cost in the experiment, the analysis is carried out to develop a new model for evaluating post-combustion emission characteristics based on the physical properties of liquid fuels. Raw data is extracted from experimental investigations to establish the present analysis models. Experimental studies have been carried out to evaluate the properties of different fuels and their composition-wise effects on flame, temperature, and emission characteristics. Thereby, reliable combustion performance and low emission profiles (in terms of physical fuel properties) can be ensured for potential alternative fuels. The results of the analysis show that specific properties such as high viscosity, high density, and high aromatic content of the fuel have the potential to generate high CO. In contrast, a decrease in these properties promotes high CO2 formation. In addition, low NOx emissions and low CO trends are unlikely to be achieved by simultaneously changing the value of fuel properties. The analysis shows that the low viscosity of the fuel induces low soot emission and flame length retardant.

Effects of hydrogen enrichment on the heat generation and emission of natural gas turbulent premixed flame

The demand for clean energy and the decarbonisation targets set globally require researching and developing new solutions. An efficient computational approach was implemented to examine the effect of hydrogen enrichment on flame characteristics, flame temperature, heat generation, NOx and carbon emissions under varying stoichiometry of combustion. Results showed that hydrogen enrichment significantly reduces CO2 emissions but also has undesirable effects which include reducing the heat generation capability of flame and increasing NOx emissions. The level of impact on each of these characteristics was found to be different. Under a boiler-like condition and stoichiometry (Ф = 0.8), a 10 % decrease in CO2 emissions was observed when enriching the fuel with 20 % hydrogen. Concurrently, the heat flux generated from the flame is reduced by 6 % and NOx emission is increased by 2 %. The effect of hydrogen enrichment on these aspects becomes more prominent at a higher enrichment level. The study also finds that making combustion leaner is an effective strategy to combat the effect of hydrogen enrichment with respect to CO2 and NOx emission generation. Despite the leaner combustion producing less emissions for any given hydrogen enrichment level, it significantly decreases the heat transfer capacity of the flame. Alongside these flame characteristics, the significant role of hydrogen enrichment on increasing water vapour (H2O) production was examined.

Experimental investigation on the development characteristics of explosive overpressure induced by high-pressure hydrogen jet flame

Accidental release of high-pressure hydrogen can induce the self-ignition, and the spontaneously combusting flame can eventually induce a non-premixed jet flame or even explosion. In this study, the explosion overpressure characteristic of hydrogen jet flame outside the pipeline was investigated. Experiments were conducted on high-pressure hydrogen release pipelines with a diameter of 10 mm and pipeline lengths of 750, 1450 and 2200 mm, respectively, under different hydrogen release pressure. The impact of different initial conditions on the peak value of high-pressure hydrogen jet explosion was systematically investigated. The external pressure signals and flame images were completely collected. The results show that the external explosion overpressure decreased with the increase of axial distance away from the nozzle. When the length of the pipeline increased, the peak value of the overpressure was also gradually decreased. Meanwhile, as the high-pressure hydrogen burst pressure increased, the overpressure rose first and then decreased. With the increase of release pressure, when the hydrogen pressure exceeded 8 MPa, the hydrogen flow in the tube formed a blocked flow, so the increase of external explosion overpressure became slow. This topic can provide a reference for the safety development of the high-pressure hydrogen storage system.

A machine learning-based approach for flames classification in industrial Heavy Oil-Fire Boilers

The burner combustion tuning is a complex problem that has been studied through flame monitoring and characterization. It has been observed that the flame electromagnetic spectrum and flickering contain specific flame information in combustion processes. This information is helpful for combustion stoichiometry tuning on burners. This paper described a method for selecting the best flame feature subset that can be computed from the scanner signal, in order to get the flame index and induce combustion stoichiometry on burners under specific combustion conditions. We propose a method for selecting a reduced subset with only the useful flame features for flame index classification. To extract the most relevant flame features we use a feature subset selection (FSS) algorithm and to determine the combustion state in burners, five flame indices were defined that represent the most common flame states in oil fuel-fired boilers. FSS includes complete, sequential, and random searches in order to eliminate redundant and noisy flame features to decrease the flame feature set dimension. A probabilistic neural network (PNN) algorithm was implemented for flame feature clustering. Signals from the actual flame scanner system and relevant variables from the boiler data acquisition system were used by the algorithms to calculate the burner flame index. A set of parametric tests was done in a heavy oil-fired boiler under well-known flame and index conditions to train and test the flame classifier. The results showed that only the four more relevant features are enough to classify flames with a good performance (92.3% accuracy), which is useful for burner combustion monitoring and optimization.

Numerical and Experimental Reconstruction of Temperature Distribution and Soot Concentration Field for Thin-Slice Flames Using a Charge Coupled Device Camera

This work proposed a novel model to simultaneously reconstruct temperature distribution and soot volume fraction field for two-dimensional thin-slice flames using the knowledge of monochromatic radiation intensities at two wavelengths using a CCD camera. The deduction process and numerical analysis of the model were described. Effects of wavelength combinations and measurement errors on reconstruction accuracy were considered in detail. Numerical results have proven the model’s accuracy and showed that the temperature and soot volume fraction fields can be reconstructed well even with noisy input data from flame radiation. In addition, a series of experiments were conducted on a mesoscale combustor to obtain the real thin-slice flames for further experimental reconstruction via the model. The experimental results indicated that the proposed model can successfully reconstruct the flame temperature distribution and soot volume fraction field and the main features of thin-slice flames also can be reasonably reproduced.

BPNN model based AI for the estimation of soot data from flame luminosity emissions in H2/N2 diluted ethylene laminar diffusion flames

Advanced combustion devices and alternative fuels like hydrogen require an estimation of the impact of such changes on engine exhaust emissions of regulated pollutants like soot. Huge experimental data are then required to be collected and post-processed, both in academic and industrial setups. Machine learning and artificial intelligence can be employed to reduce cost and time. This study presents a Back Propagation Neural Network (BPNN) model that has been validated and optimized for the simultaneous prediction of soot volume fraction, temperature and particle sizes from flame luminosity measurements. The compatibility, robustness and reliability of neural network models in terms of fuel composition and flow rate variations was analyzed , by varying both fuel flow rate and fuel stream dilution in axisymmetric diffusion flame burning in a coflow of air. BPNN model predicted results were contrasted against those obtained through laser diagnostics. A detailed analysis of the performance of BPNN model, based on an extensive experimental study revealed indifference to N2/H2 dilution and fuel flow rate variations. Furthermore, an original BPNN model is optimized to improve learning rate and to reduce computation cost, by applying a Bayesian algorithm which continuously monitors and minimizes an error function. It was concluded that a training set size of three was sufficient to predict soot field parameters with a fair prediction accuracy. These results have direct implication for the application of proposed technique in practical combustion equipment where operating parameter, e.g. Air–fuel ratio and EGR, show both gradual and instantaneous variations and affect both performance and emissions. These results clearly demonstrate the robustness of this technique which offers opportunities for real-time, in situ, monitoring of practical combustion devices. Hence, Real-time data of sooting characteristics of flames can be used to both monitor and control pollutant emissions by integrating a response strategy in the system.