Semianalytical Correlations for NOx, CO, and UHC Emissions

Abstract

To meet the future goals of reduced emissions produced by gas turbine combustors, a better understanding of the process of formation of various pollutants is required. Both empirical and analytical approaches are used to provide the exhaust concentrations of pollutants of interest such as NOx, CO, and unburned hydrocarbon with varying degrees of success. In the present investigation, an emission model that simulates the combustor by a number of reactors representing various combustion zones is proposed. A detailed chemical kinetic scheme was used to provide a fundamental basis for the derivation of a number of expressions that simulate the reaction scheme. The model addresses the combined effects of spray evaporation and mixing in the reaction zone. The model validation included the utilization of a large data base obtained for an annular combustor of a modern turbopropulsion engine. In addition to the satisfactory agreement with the measurements, the model provided insight into the regions within the combustor that could be responsible for the excessive formation of emissions. Methods to reduce the emissions may be implemented in light of such information.

Investigation of parameters affecting exergy and emission performance of basic and intercooled gas turbine cycles

“…of Mongia [5]. The parameters controlling emission in the proposed model are taken to be equivalence ratio (f), primary-zonetemperature, residence time, combustor inlet pressure and temperature.…”

“…Other parameters affecting UHC emission are residence time, combustor inlet pressure as well as pressure drop in combustor due to excessive turbulence (induced in the combustor to enhance combustion). The mass of UHC emission has been has been modeled to be dependent upon various parameters as under [5]:…”

“…N. K. Rizk and H. C. Mongia [5] have reported results of an emission model that addresses the combined effect of spray evaporation and mixing in the gas turbine combustor reaction zone. The model also provides an insight into the regions within the combustor that could be responsible for the excessive formation of NO x , CO (carbon-monoxide) and UHC (unburnt-hydrocarbon).…”

Microturbine Design Point Evaluation and Optimization Considering Pollutant Emissions and Thermoeconomic Approach

“…= total cost rate of operation, ∕h c p = specific heat at constant pressure, kJ∕k e 1 , e 2 , e 3 = quadratic functions f = material cost factor far = fuel air ratio h = stagnation enthalpy, kJ∕kg m = mass, kg _ m = mass flow, kg∕s N = number of operating hours per year, h∕year P = stagnation pressure, kPa R = gas constant, kJ∕kgK r = pressure ratio T = stagnation temperature, K v i = product mol number, mol W = specific work output, kJ∕Kg _ W = power, kW z i = reagent mol number, mol A, α, β, λ, σ = coefficients in Gulder's expression [29] ΔP = pressure drop ε = recuperator effectiveness, % η = cycle efficiency, % θ = dimensionless temperature ξ = investments over the capital, % π = dimensionless pressure τ = combustor residence time, ms τ ev = evaporation time, ms ϕ = entropy function, kJ∕kg φ = fuel to air equivalence ratio ψ = fuel H∕C atomic ratio become widespread in recent years as distributed generation (DG). DG is known as on-site power generation or at the point of consumption, eliminating the difficulties associated with transmission and distribution, such as cost, complexity, energy loss, and interdependencies.…”

“…The NO x formation is more complex, but it is of less concern than the others because microturbines operate with lean mixture and low adiabatic flame temperature, reaching a very low rate of emission of NO x . According to microturbine operation conditions, the pollution equations proposed by Rizk and Mongia [29] and Lewis [30] were used in this work. Lewis suggests that NO x formation depends only on the postcombustion temperature and pressure and it is completely independent of the residence time of the gases inside the combustor chamber.…”