Abstract
Global sensitivity analysis (GSA) of large chemical reaction mechanisms remains a challenge since the model with uncertainties in the large number of input parameters provides large dimension of input parameter space and tends to be difficult to evaluate the effect of input parameters on model outputs. In this paper, a criterion for frequency selection to input parameter is proposed so that Fourier amplitude sensitivity test (FAST) method can evaluate the complex model with a low sample size. This developed FAST method can establish the relationship between the number of input parameters and sample size needed to measure sensitivity indices with high accuracy. The performance of this FAST method which can allow both the qualitative and quantitative analysis of complex systems is validated by a H2/air combustion model and a CH4/air combustion model. This FAST method is also compared with other GSA methods to illustrate the features of this FAST method. The results show that FAST method can evaluate the reaction systems with low sample size, and the sensitivity indices obtained from the FAST method can provide more important information which the variance-based GSA methods cannot obtain. FAST method can be a remarkably effective tool for the modelling and diagnosis of large chemical reaction.
Highlights
Combustion in engines with a practical fuel is very complex and is commonly described by a detailed mechanism which may involve dozens or even hundreds of reactions
H2/Air Reaction Mechanisms. e aim of this section is to validate the formula of frequency selection proposed in (3) and evaluate the performance of the Fourier amplitude sensitivity test (FAST) method. e H2/O2 combustion model developed by Konnov [26] is selected as test case to validate the performance of the FAST method since this combustion model has defined the uncertainty factor for each reaction
We generated logarithmically 1000 points in the range of 10−5 to 10−2 s as time points for the sensitivity indices measured by the global sensitivity analysis (GSA) methods, and the ordinary differential equation (ODE) solver should be modified for obtaining the calculation results at fixed points in time
Summary
Combustion in engines with a practical fuel is very complex and is commonly described by a detailed mechanism which may involve dozens or even hundreds of reactions. Ese methods have been successfully applied to complex reaction models such as reaction mechanism construction [21,22,23,24] and chemical reaction mechanism analysis [6, 19, 25] These GSA methods are rarely employed to evaluate large numbers of input numbers. Since Sobol’ method does not employ the dimensionality reduction techniques like FAST and HDMR methods, it needs very large sample size to evaluate the reaction systems. Sobol’ method with large sample size is widely applied to validate other GSA methods through a model with small input parameters since sensitivity indices for complex reaction systems could not be analytically evaluated. Only few references of GSA methods are validated by using them to large combustion mechanisms with a small sample size and a low computational cost
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