scholarly journals Influence of Fuel Composition and Spray Characteristics on Nitric Oxide Formation

1989 ◽  
Author(s):  
K. K. Rink ◽  
A. H. Lefebvre
Keyword(s):  
Nitric Oxide ◽  
Drop Size ◽  
Perforated Plate ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Fuel Composition ◽  
Circular Array ◽  
Nitric Oxide Formation ◽  
Nitric Oxide Emissions ◽  
Standard Instrumentation

Measurements of nitric oxide emissions are carried out on a continuous flow combustor when operating over wide ranges of fuel/air ratio at pressures up to 1.52 MPa (15 atmos). Fuel is supplied to the flame zone from a circular array of 30 equispaced miniature airblast atomizers which is incorporated into a perforated-plate flameholder. Standard instrumentation and sampling techniques are used to measure pollutant emissions over wide ranges of mean fuel drop size. The results obtained with several selected fuels demonstrate the effects of variations in fuel composition, fuel drop size, and combustor operating conditions on nitric oxide emissions.

Effect of Fuel Composition on Emissions From a Low-Swirl Burner

2007 ◽  
Author(s):  
Daniel Sequera ◽  
Ajay K. Agrawal
Keyword(s):  
Gas Turbines ◽  
Bluff Body ◽  
Swirling Flow ◽  
Flame Temperature ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Recirculation Region ◽  
Fuel Composition ◽  
High Hydrogen ◽  
Flow Recirculation

Lean Premixed Combustion (LPM) is a widely used approach to effectively reduce pollutant emissions in advanced gas turbines. Most LPM combustion systems employ the swirling flow with a bluff body at the center to stabilize the flame. The flow recirculation region established downstream of the bluff-body brings combustion products in contact with fresh reactants to sustain the reactions. However, such systems are prone to combustion oscillations and flame flashback, especially if high hydrogen containing fuels are used. Low-Swirl Injector (LSI) is an innovative approach, whereby a freely propagating LPM flame is stabilized in a diverging flow field surrounded by a weakly-swirling flow. The LSI is devoid of the flow recirculation region in the reaction zone. In the present study, emissions measurements are reported for a LSI operated on mixtures of methane (CH4), hydrogen (H2), and carbon monoxide (CO) to simulate H2 synthetic gas produced by coal gasification. For a fixed adiabatic flame temperature and air flow rate, CH4 content of the fuel in atmospheric pressure experiments is varied from 100% to 50% (by volume) with the remainder of the fuel containing equal amounts of CO and H2. For each test case, the CO and nitric oxide (NOx) emissions are measured axially at the combustor center and radially at several axial locations. Results show that the LSI provides stable flame for a range of operating conditions and fuel mixtures. The emissions are relatively insensitive to the fuel composition within the operational range of the present experiments.

Modelling and Optimization of the NO Formation in an Industrial Glass Furnace

1992 ◽  
Vol 114 (4) ◽  
pp. 514-523 ◽  
Author(s):  
M. G. Carvalho ◽  
V. S. Semia˜o ◽  
P. J. Coelho
Keyword(s):  
Nitric Oxide ◽  
Mathematical Model ◽  
Glass Furnace ◽  
Dominant Role ◽  
Formation Rate ◽  
Heat Transfer Process ◽  
Operating Conditions ◽  
Industrial Glass ◽  
Nitric Oxide Emissions ◽  
Glass Furnaces

The effects of combustion excess-air level, air preheating, and fuel composition on the nitric oxide emissions from an industrial glass furnace are studied through the use of a mathematical model. The mathematical model is based on the solution of the time-averaged form of the governing conservation equations for mass, momentum, energy, and chemical species. The k-ε turbulence model is employed for modelling the turbulence fluxes. The flame is modelled as a turbulent diffusion one and the chemical reactions associated with the heat release are assumed to be fast. The fluctuations of scalar properties are accounted for by use of a clipped-Gaussian probability density function. The thermal radiation, playing the dominant role in the heat-transfer process, is modelled using the discrete transfer method. Because of the high temperatures at which industrial glass furnaces operate a considerable amount of thermal NO is formed. The present work presents a model, based on a chemical kinetic approach, to predict the nitric oxide emissions from industrial glass furnaces. The Zeldovich mechanism, retaining the reverse reactions, is incorporated in the model in order to predict the instantaneous NO net formation rate from atmospheric nitrogen. The whole procedure is applied to a cross-fired regenerative furnace. A set of parametric studies is carried out, demonstrating the ability of the model to evaluate the influence of changes in operating conditions on the NO emissions.

Impact of Fuel Composition on Blow Off and Flashback in Swirl Stabilized Lean Premixed Combustion

2013 ◽  
Author(s):  
Amin Akbari ◽  
Vincent McDonell ◽  
Scott Samuelsen
Keyword(s):  
Natural Gas ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Pollutant Emissions ◽  
Fuel Composition ◽  
Pure Hydrogen ◽  
Combustion Properties ◽  
Lean Premixed ◽  
The Impact

Co firing of natural gas with renewable fuels such as hydrogen can reduce greenhouse gas emissions, and meet other sustainability considerations. At the same time, adding hydrogen to natural gas alters combustion properties, such as burning speeds, heating values, flammability limits, and chemical characteristics. It is important to identify how combustion stability relates to fuel mixture composition in industrial gas turbines and burners and correlate such behavior to fuel properties or operating conditions. Ultimately, it is desired to predict and prevent operability issues when designing a fuel flexible gas turbine combustor. Fuel interchangeability is used to describe the ability of a substitute fuel composition to replace a baseline fuel without significantly altering performance and operation. Any substitute fuel, while maintaining the same heating load as the baseline fuel, must also provide stable combustion with low pollutant emissions. Interchangeability indices try to predict the impact of fuel composition on lean blowoff and flashback. Correlations for operability limits have been reported, though results are more consistent for blowoff compared to flashback. Yet, even for blowoff, some disagreement regarding fuel composition effects are evident. In the present work, promising correlations and parameters for lean blow off and flashback in a swirl stabilized lean premixed combustor are evaluated. Measurements are conducted for fuel compositions ranging from pure natural gas to pure hydrogen under different levels of preheat and air flow rates. The results are used to evaluate the ability of existing approaches to predict blowoff and flashback. The results show that, while a Damköhler number approach for blowoff is promising, important considerations are required in applying the method. For flashback, the quench constant parameter suggested for combustion induced vortex breakdown was applied and found to have limited success for predicting flashback in the present configuration.

Nitric Oxide Formation in Diesel Engines

1974 ◽  
Vol 188 (1) ◽  
pp. 477-483 ◽  
Author(s):  
H. Çakir
Keyword(s):  
Nitric Oxide ◽  
Nitrogen Oxides ◽  
Analytical Solutions ◽  
Diesel Engines ◽  
Operating Conditions ◽  
Experimental Results ◽  
Combustion Model ◽  
Oxide Formation ◽  
Nitric Oxide Formation ◽  
Good Agreement

A combustion model is presented to account for the nitric oxide formation in diesel engines at all operating conditions. The paper tries to introduce the concept of variable air-fuel ratio estimated to exist during diesel combustion. Analytical solutions are found to be in good agreement with experimental results. Further investigations will be directed to diesel engines having combustion systems other than the M.A.N.-FM system, and to possible remedies to reduce the formation of nitrogen oxides.

Influence of fuel composition on nitric oxide formation in mass-burning stokers

Fuel ◽  
1986 ◽  
Vol 65 (8) ◽  
pp. 1047-1050 ◽  
Author(s):  
G.P. Starley ◽  
B.J. Overmoe ◽  
D.W. Pershing ◽  
G.B. Martin
Keyword(s):  
Nitric Oxide ◽  
Fuel Composition ◽  
Oxide Formation ◽  
Nitric Oxide Formation

The Use of a Three-Zone Combustion Model to Determine Nitric Oxide Emissions From a Homogeneous-Charge, Spark-Ignited Engine

2003 ◽  
Author(s):  
Jerald A. Caton
Keyword(s):  
Nitric Oxide ◽  
Engine Speed ◽  
Combustion Process ◽  
Core Region ◽  
Operating Conditions ◽  
Combustion Model ◽  
Nitric Oxides ◽  
Cycle Simulation ◽  
Nitric Oxide Emissions ◽  
Homogeneous Charge

Nitric oxide emissions were estimated for a homogeneous-charge, spark-ignited automotive engine using a cycle simulation which employed three zones for the combustion process: (1) unburned gas, (2) adiabatic core region, and (3) boundary-layer gas. The use of the adiabatic core region has been shown to be especially necessary to capture the production of nitric oxides which are highly temperature dependent. The effects of major engine parameters such as equivalence ratio, spark timing, inlet manifold pressure, and engine speed on nitric oxide emissions are examined. In particular, the detail reasons for the effects of these engine parameters on the nitric oxide emissions are presented. Comparisons are completed between the computed values and a set of published measurements for the nitric oxide concentrations. Although not all engine parameters were known, reasonable agreement is demonstrated for most cases. In particular, the variations of nitric oxide concentrations as engine speed increased were duplicated. As an example, four operating conditions are examined in detail to help explain the measured results. Nitric oxide emissions are shown to be mainly the net result of gas temperatures, oxygen concentrations, and residence times.

Effects of Hydrogen Enrichment on Confined Methane Flame Behavior

2006 ◽  
Author(s):  
Onur Tuncer ◽  
Sumanta Acharya ◽  
Jong Ho Uhm
Keyword(s):  
Gas Turbine ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Major Constituent ◽  
Fuel Composition ◽  
Mixed Gas ◽  
Gas Turbine Combustor ◽  
Flammability Limits ◽  
Methane Flame ◽  
Flame Flashback

Many land based power generation units presently operate on natural gas, whose major constituent is methane, and many of them would need to tackle the challenges due to a fuel switch towards synthesis gas in the near future. Operating conditions and stability of a pre-mixed gas turbine combustor is quite sensitive to the changes in the fuel composition. Behavior of a premixed confined hydrogen enriched methane flame is studied with regard to thermo-acoustic instability induced flame flashback, emissions, flammability limits and acoustics over a wide range of operating conditions. However, most emphasis is put on lean combustion, which is an industry standard method used to lower pollutant emissions by reducing adiabatic flame temperatures. Hydrogen addition extends the flammability limits and enables lower nitric oxide emissions levels to be achieved at leaner equivalence ratios. On the other hand, increased root-mean-square pressure fluctuation levels, and higher susceptibility to flashback is observed with increasing hydrogen volume fraction inside the fuel mixture. This phenomenon is mostly attributed to much higher burning speeds of hydrogen in contrast to pure methane. A semi-analytical model has been utilized to capture the flame holding and thermo-acoustically induced flame flashback dynamics for a pre-mixed gas turbine combustor. A simple linearized acoustic model, derived from the basic conservation laws, and a front-tracking algorithm based on the Markstein’s G-equation are coupled together in order to track the flame initiation front, which in turn yields in an understanding of dynamic flame holding characteristics. A limit cycle behavior in the flame front movement is observed during simulations due to a non-linearity in the feedback term that relates acoustic velocity to heat release. Sets of experiments including flashback speed measurements have been performed at varying fuel composition. Phase locked CH radical imaging measurements have also been performed in order to track the flame initiation front in time with respect to the dominant instability cycle. Computer simulations are performed to study flashback and combustor acoustics together numerically and it is observed that these are in good qualitative agreement with the experiments.

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