Download or read book Modeling and Analysis of the Formation of Oxides of Nitrogen and Formaldehyde in Large bore Lean burn Natural Gas Engines written by Anamol Pundle and published by . This book was released on 2013 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: Emissions from large-bore, spark ignition engines running on natural gas pose a serious problem, especially in non-attainment areas. These engines emit substantial amounts of oxides of nitrogen, unburned hydrocarbons and carbon monoxide. The pathways of formation of oxides of nitrogen (NOx) and formaldehyde (HCHO) have been explored in this study. This is done by using UWSI, a computer model of gas phase combustion in spark-ignition engines previously developed at the University of Washington, and through chemical reactor modeling using CHEMKIN. The UWSI model is set up and calibrated using data from a single test case. Further matching of NOx emissions for varying fuel-air equivalence ratios is also performed and the model is then used to predict NOx emission for three leanest cases beyond the range of test data. The HCHO emission from the model for each test case is examined. Several scenarios which may lead to HCHO formation in the engine are also modeled. NOx formation pathways at lean conditions in these engines are studied through chemical reactor modeling. A simplified NOx model based on the results of the chemical reactor modeling is developed and validated by comparing its results against those obtained from the UWSI code. Results obtained indicate that incomplete propagation of the flame across the cylinder is the most likely pathway to HCHO formation in these engines. Engines experiencing borderline auto-ignition may also contribute to HCHO emission, while unburned charge trapped in cracks and crevices and released late in the cycle is not indicated to have a significant effect. The Zeldovich and nitrous oxide pathways are shown to be the predominant contributors to NOx formation at lean conditions in these engines. A simplified NOx predictor based on these pathways is developed and validated against data obtained from the UWSI model.

Download or read book Selective NOx Recirculation for Stationary Lean Burn Natural Gas Engines written by Nigel N. Clark and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nitric oxide (NO) and nitrogen dioxide (NO2) generated by internal combustion (IC) engines are implicated in adverse environmental and health effects. Even though lean-burn natural gas engines have traditionally emitted lower oxides of nitrogen (NOx) emissions compared to their diesel counterparts, natural gas engines are being further challenged to reduce NOx emissions to 0.1 g/bhp-hr. The Selective NOx Recirculation (SNR) approach for NOx reduction involves cooling the engine exhaust gas and then adsorbing the NOx from the exhaust stream, followed by the periodic desorption of NOx. By sending the desorbed NOx back into the intake and through the engine, a percentage of the NOx can be decomposed during the combustion process. SNR technology has the support of the Department of Energy (DOE), under the Advanced Reciprocating Engine Systems (ARES) program to reduce NOx emissions to under 0.1 g/bhp-hr from stationary natural gas engines by 2010. The NO decomposition phenomenon was studied using two Cummins L10G natural gas fueled spark-ignited (SI) engines in three experimental campaigns. It was observed that the air/fuel ratio ({lambda}), injected NO quantity, added exhaust gas recirculation (EGR) percentage, and engine operating points affected NOx decomposition rates within the engine. Chemical kinetic model predictions using the software package CHEMKIN were performed to relate the experimental data with established rate and equilibrium models. The model was used to predict NO decomposition during lean-burn, stoichiometric burn, and slightly rich-burn cases with added EGR. NOx decomposition rates were estimated from the model to be from 35 to 42% for the lean-burn cases and from 50 to 70% for the rich-burn cases. The modeling results provided an insight as to how to maximize NOx decomposition rates for the experimental engine. Results from this experiment along with chemical kinetic modeling solutions prompted the investigation of rich-burn operating conditions, with added EGR to prevent preignition. It was observed that the relative air/fuel ratio, injected NO quantity, added EGR fraction, and engine operating points affected the NO decomposition rates. While operating under these modified conditions, the highest NO decomposition rate of 92% was observed. In-cylinder pressure data gathered during the experiments showed minimum deviation from peak pressure as a result of NO injections into the engine. A NOx adsorption system, from Sorbent Technologies, Inc., was integrated with the Cummins engine, comprised a NOx adsorbent chamber, heat exchanger, demister, and a hot air blower. Data were gathered to show the possibility of NOx adsorption from the engine exhaust, and desorption of NOx from the sorbent material. In order to quantify the NOx adsorption/desorption characteristics of the sorbent material, a benchtop adsorption system was constructed. The temperature of this apparatus was controlled while data were gathered on the characteristics of the sorbent material for development of a system model. A simplified linear driving force model was developed to predict NOx adsorption into the sorbent material as cooled exhaust passed over fresh sorbent material. A mass heat transfer analysis was conducted to analyze the possibility of using hot exhaust gas for the desorption process. It was found in the adsorption studies, and through literature review, that NO adsorption was poor when the carrier gas was nitrogen, but that NO in the presence of oxygen was adsorbed at levels exceeding 1% by mass of the sorbent. From the three experimental campaigns, chemical kinetic modeling analysis, and the scaled benchtop NOx adsorption system, an overall SNR system model was developed. An economic analysis was completed, and showed that the system was impractical in cost for small engines, but that economies of scale favored the technology.

Download or read book Model for Nitric oxide Formation in a Large bore Spark Gas Engine written by R. P. Wilson and published by . This book was released on 1979 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Formaldehyde as a Tracer to Examine Mixture Formation in Spark Ignited Engines written by Aulia Muhammad Taufiq Nasution and published by Cuvillier Verlag. This book was released on 2006 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Study of Pollutant Formation from the Lean Premixed Combustion of Gaseous Fuel Alternatives to Natural Gas written by Keith Boyd Fackler and published by . This book was released on 2011 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this research is to identify how nitrogen oxide (NOx) emissions and flame stability (blowout) are impacted by the use of fuels that are alternatives to typical pipeline natural gas. The research focuses on lean, premixed combustors that are typically used in state-of-the-art natural gas fueled systems. An idealized laboratory lean premixed combustor, specifically the jet-stirred reactor, is used for experimental data. A series of models, including those featuring detailed fluid dynamics and those focusing on detailed chemistry, are used to interpret the data and understand the underlying chemical kinetic reasons for differences in emissions between the various fuel blends. An ultimate goal is to use these data and interpretive tools to develop a way to predict the emission and stability impacts of changing fuels within practical combustors. All experimental results are obtained from a high intensity, single-jet stirred reactor (JSR). Five fuel categories are studied: (1) pure H2, (2) process and refinery gas, including combinations of H2, CH4, C2H6, and C3H8, (3) oxygen blown gasified coal/petcoke composed of H2, CO, and CO2, (4) landfill and digester gas composed of CH4, CO2, and N2, and (5) liquified natural gas (LNG)/shale/associated gases composed of CH4, C2H6, and C3H8. NOx measurements are taken at a nominal combustion temperature of 1800 K, atmospheric pressure, and a reactor residence time of 3 ms. This is done to focus the results on differences caused by fuel chemistry by comparing all fuels at a common temperature, pressure, and residence time. This is one of the few studies in the literature that attempts to remove these effects when studying fuels varying in composition. Additionally, the effects of changing temperature and residence time are investigated for selected fuels. At the nominal temperature and residence time, the experimental and modeling results show the following trends for NOx emissions as a function of fuel type: 1.) NOx emissions decrease with increasing H2 fuel fraction for combustion of CH4/H2 blends. This appears to be caused by a reduction in the amount of NO made by the prompt pathway involving the reaction of N2 with hydrocarbon radicals as the CH4 is replaced by H2. 2.) For category 2 (the process and refinery blend) and category 5 (the LNG, shale, and associated gases), NOx emissions increase with the addition of C2 and C3 hydrocarbons. This could be due to an increased production of free radicals resulting from increasing CO production when higher molecular weight hydrocarbons are broken down. 3.) For category 3 (the O2 blown gasified coal/petcoke), NOx emissions increase with increasing CO fuel fraction. The reason for this is attributed to CO producing more radicals per unit heat release than H2. When CO replaces H2, an increase in NOx emissions is seen due to an increase in the productivity of the N2O, NNH, and Zeldovich pathways. 4.) For category 4 (the landfill gas) the addition of diluents such as CO2 and N2 at constant air flow produces more NOx per kg of CH4 consumed, and N2 is more effective than CO2 in increasing the NOx emission index. The increase in emission index appears to be due to an enhancement of the prompt NOx pathway as the diluents are added and the mixture moves towards stoichiometric. In addition, the presence of CO2 as a diluent catalyzes the loss of flame radicals, leading to less NOx formation than when an equivalent amount of N2 is used as a diluent. For a selected set of fuels, detailed spacial reactor probing is carried out. At the nominal temperature and residence time, the experimental results show the following trends for flame structure as a function of fuel type: 1.) Pure H2 is far more reactive in comparison to CH4 and all other pure alkane fuels. This results in relatively flat NOx and temperature profiles; whereas, the alkane fuels drop in both temperature and NOx production in the jet, where more fresh reactor feed gases are present. 2.) For category 2 (the Process and Refinery blends), H2 addition increases reactivity in the jet while decreasing overall NOx emissions. The increased reactivity is especially evident in the CO profiles where the fuels blended with C2H6 and H2 have CO peaks on jet centerline and CO emissions for pure CH4 peaks slightly off centerline. 3.) For category 3 (the O2 blown gasified coal/petcoke), the temperature profiles for the gasification blend and pure H2 are nearly identical, which is likely due to the high reactivity of H2 dominating the relatively low reactivity of CO. Despite a small temperature difference, the addition of CO causes an increase in NOx production. 4.) For category 4 (the landfill gas), the temperature profiles are virtually indistinguishable. However, the addition of diluent decreases reactivity and spreads out the reaction zone with the CO concentration peaking at 2 mm off of centerline instead of 1 mm. Diluent addition increases NOx production in comparison to pure CH4 for reasons explained above. 5.) For category 5 (the LNG, shale, and associated gases), the temperature profiles are all very similar. The increased reactivity of C2H6 is evident from looking at the CO profiles. Increased C2H6 promotes CO production on jet centerline which is indicative of the hydrocarbon material breaking down earlier in the jet. At temperatures and residence times other than the nominal conditions, the experimental results show the following trends: 1,) The NOx emissions from LPM combustion of pure CH4, H2, C2H6, and C3H8 are shown to vary linearly with residence time and in an Arrhenius fashion with temperature. This occurs because (1) more reaction time leads to more NOx formation, and (2) NOx formation is a strong, non-linear function of temperature. 2.) The addition of both H2 and C2H6 to a LPM CH4 flame is effective at extending its lean blowout limit. The results of both two and three dimensional CFD simulations are presented to illustrate the general flow, temperature, and species structure within the reactor. Since the two dimensional model is far more computationally efficient, it is employed to study various fuel mixtures with more sophisticated chemical mechanisms. The CFD results from the LPM combustion of H2, H2/CO, and CH4 with NOx formation are presented. A three dimensional CFD simulation is run for LPM CH4 combustion that uses a global CH4 oxidation mechanism. While this model does not predict intermediate radicals and NOx, the CO contours and flow field can be used as guidelines to develop a chemical reactor network (CRN), which can incorporate detailed chemistry. In addition, this model runs quickly enough that it is a good way to initialize the temperature and flow field for simulations that do incorporate more complex chemistry. The two dimensional model is used to illustrate the difference in combustion behavior between the various fuels tested. In particular, it illustrates the geometric locations of the super-equilibrium radical fields and shows where and through which pathways NOx is formed. The pathway breakdowns show good agreement with the CRN modeling results. The main goal of the CFD modeling is to use the results of each model to develop Chemical Reactor Networks, CRNs, that are customized for a particular burner. The CRN can then be used to estimate the impacts due to fuel variation.

Download or read book Experimental and Analytical Study of Nitric Oxide Formation During Combustion of Propane in a Jet stirred Combustor written by N. T. Wakelyn and published by . This book was released on 1978 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Biographies des pr tres du dioc se de Cambrai qui se sont le plus distingu s written by and published by . This book was released on 1890 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Chemical Kinetic Models for Combustion of Hydrocarbons and Formation of Nitric Oxide written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-13 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: The formation of nitrogen oxides NOx during combustion of methane, propane, and a jet fuel, JP-4, was investigated in a jet stirred combustor. The results of the experiments were interpreted using reaction models in which the nitric oxide (NO) forming reactions were coupled to the appropriate hydrocarbon combustion reaction mechanisms. Comparison between the experimental data and the model predictions reveals that the CH + N2 reaction process has a significant effect on NO formation especially in stoichiometric and fuel rich mixtures. Reaction models were assembled that predicted nitric oxide levels that were in reasonable agreement with the jet stirred combustor data and with data obtained from a high pressure (5.9 atm (0.6 MPa)), prevaporized, premixed, flame tube type combustor. The results also suggested that the behavior of hydrocarbon mixtures, like JP-4, may not be significantly different from that of pure hydrocarbons. Application of the propane combustion and nitric oxide formation model to the analysis of NOx emission data reported for various aircraft gas turbines showed the contribution of the various nitric oxide forming processes to the total NOx formed. Jachimowski, C. J. and Wilson, C. H. Langley Research Center NASA-TP-1794, L-14106 RTOP 506-52-33-01...

Download or read book Controlling Nitrogen Oxides written by Alice Hastings and published by . This book was released on 1980 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Computer Model of Nitric Oxide and Carbon Monoxide Formation in a Lean burn Gas fired Spark Ignition System written by Stephen F. Clark and published by . This book was released on 1989 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimentation and Modeling of NOx Formation from a Micro pilot Ignited Natural Gas Engine written by Huateng Yang and published by . This book was released on 2005 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Inevitability of Engine Out Nox Emissions from Spark Ignition and Diesel Engines written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Internal combustion engines, both spark ignition and Diesel, are dominant types of vehicle power sources and also provide power for other important stationary applications. Overall, these engines are a central part of power generation in modern society. However, these engines, burning hydrocarbon fuels from natural gas to gasoline and Diesel fuel, are also responsible for a great deal of pollutant emissions to the environment, especially oxides of nitrogen (NO[sub x]) and unburned hydrocarbons (UHC). In recent years, pollutant species emissions from internal combustion engines have been the object of steadily more stringent limitations from various governmental agencies. Engine designers have responded by developing engines that reduce emissions to accommodate these tighter limitations. However, as these limits become ever more stringent, the ability of engine design modifications to meet those limits must be questioned. Production of NO[sub x] in internal combustion engines is primarily due to the high temperature extended Zeldovich reaction mechanism: (1) O + N[sub 2] = NO + N; (2) N + O[sub 2] = NO + O; and (3) N + OH = NO + H. The rates of these reactions become significant when combustion temperatures reach or exceed about 2000K. This large temperature dependence, characterized by large activation energies for the rates of the reactions listed here, is a direct result of the need to break apart the tightly bonded oxygen and nitrogen molecules. The strongest bond is the triple bond in the N [triple-bond] N molecule, resulting in an activation energy of about 75 kcal/mole for Reaction (1), which is the principal cause for the large temperature dependence of the extended Zeldovich NO[sub x] mechanism. In most engines, NO[sub x] is therefore produced primarily in the high temperature combustion product gases. Using a reliable kinetic model for NO[sub x] production such as the GRI Mechanism [1] or the Miller-Bowman model [2] with hydrocarbon products at temperatures from 1500K through 2500K, the amounts of NO[sub x] produced at a given residence time in an engine can easily be computed, as shown in Figure 1. Figure 1 depicts how temperatures such as those existing in the combustion zones of heavy-duty engines would produce NO[sub x] emissions. This figure was created assuming that a fuel/air equivalence ratio [phi] of 0.65 was used to heat the combustion air. This equivalence ratio would be similar to that of a heavy-duty lean-burn spark-ignition or diesel engine. At temperatures in the neighborhood of 2000K and residence times between 1-5 milliseconds, which are typical of residence times at these temperatures in engines, the production of NO[sub x] increases dramatically. It is evident from Fig. 1 that product temperatures must remain below approximately 2100K to achieve extremely low NO[sub x] production levels in engines. This conclusion led to a combined experimental and modeling study of product gas temperatures in engine combustion and their influence on emission levels.

Download or read book Catalytic Reduction of Nitrogen Oxide Emissions with Lower Hydrocarbons for Natural Gas fired Lean burn Engines written by Sreshtha Sinha Majumdar and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A hydrothermally stable dual-catalyst aftertreatment system for emission control of nitrogen oxides (NOx) with lower hydrocarbons (CHx) has been developed for natural gas-fired stationary lean-burn engines. The dual-catalyst system consists of a physical mixture of a reduction catalyst, palladium supported on sulfated zirconia (Pd/SZ) and an oxidation catalyst, cobalt oxide supported on ceria, CoOx/CeO2. The multifunctional aftertreatment system oxidizes nitric oxide (NO) to nitrogen dioxide (NO2), reduces NO2 to nitrogen (N2), and oxidizes carbon monoxide (CO) and the unutilized hydrocarbons. For practical applications in environmental catalysis, the catalytically active powder catalyst needs to be wash-coated onto a monolith core. To prevent permanent loss of activity due to physical separation of the wash-coat from the walls of the monolith core, adhesivity enhancing materials (binders) are added to the wash-coat. A novel method of incorporating binder to the active catalyst in situ during sol-gel synthesis is presented in this work. Alumina binder incorporated into Pd/SZ in situ during sol-gel synthesis was chosen for further development of a catalytically active washcoat based on activity tests under simulated engine-exhaust conditions. The alumina binder-incorporated Pd/SZ catalyst slurry controlled at pH 1 and calcined at 700°C demonstrated the most promising NOx reduction and CH4 oxidation activity. Cyclic thermal shock tests demonstrated enhanced adhesive properties of the wash-coat to the walls of the cordierite monolith core. Thus, a catalytically active wash-coat with superior adhesive properties was developed for practical application in a real-world aftertreatment unit.

Download or read book Lean NOx Trap Catalysis for Lean Burn Natural Gas Engines written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As the nation's demand for energy grows along with concern for the environment, there is a pressing need for cleaner, more efficient forms of energy. The internal combustion engine is well established as one of the most reliable forms of power production. They are commercially available in power ranges from 0.5 kW to 6.5 MW, which make them suitable for a wide range of distributed power applications from small scale residential to large scale industrial. In addition, alternative fuels with domestic abundance, such as natural gas, can play a key role in weaning our nations dependence on foreign oil. Lean burn natural gas engines can achieve high efficiencies and can be conveniently placed anywhere natural gas supplies are available. However, the aftertreatment of Nox emissions presents a challenge in lean exhaust conditions. Unlike carbon monoxide and hydrocarbons, which can be catalytically reduced in lean exhaust, NOx emissions require a net reducing atmosphere for catalytic reduction. Unless this challenge of NOx reduction can be met, emissions regulations may restrict the implementation of highly efficient lean burn natural gas engines for stationary power applications. While the typical three-way catalyst is ineffective for NOx reduction under lean exhaust conditions, several emerging catalyst technologies have demonstrated potential. The three leading contenders for lean burn engine de-NOx are the Lean NOx Catalyst (LNC), Selective Catalytic Reduction (SCR) and the Lean Nox Trap (LNT). Similar to the principles of SCR, an LNT catalyst has the ability to store NOx under lean engine operation. Then, an intermittent rich condition is created causing the stored NOx to be released and subsequently reduced. However, unlike SCR, which uses urea injection to create the reducing atmosphere, the LNT can use the same fuel supplied to the engine as the reductant. LNT technology has demonstrated high reduction efficiencies in diesel applications where diesel fuel is the reducing agent. The premise of this research is to explore the application of Lean NOx Trap technology to a lean burn natural gas engine where natural gas is the reducing agent. Natural gas is primarily composed of methane, a highly stable hydrocarbon. The two primary challenges addressed by this research are the performance of the LNT in the temperature ranges experienced from lean natural gas combustion and the utilization of the highly stable methane as the reducing agent. The project used an 8.3 liter lean burn natural gas engine on a dynamometer to generate the lean exhaust conditions. The catalysts were packaged in a dual path aftertreatment system, and a set of valves were used to control the flow of exhaust to either leg during adsorption and regeneration.

Download or read book Nitric Oxide Formation in Gas Turbine Engines written by Thomas Mikus and published by . This book was released on 1978 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of the Ratio of Hydrocarbon to Oxides of Nitrogen in Irradiated Auto Exhaust written by Merrill W. Korth and published by . This book was released on 1966 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Hydrocarbon Emissions from Lean burn Natural Gas Engines written by A. Broe Bendtsen and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: