Predicting ignition time of thermally thick solid fuels using backpropagation neural network (BPNN) and support vector regression (SVR)
摘要
Ignition time (tig) of thermally thick solids, a crucial indicator of thermal safety and fire risk, was predicted by developing three machine learning (ML) models, namely backpropagation neural network (BPNN) with only one hidden layer (BPNN1), BPNN with two hidden layers (BPNN2), and support vector regression (SVR). A 1D numerical model was utilized to generate dataset. Six parameters highly related to tig served as inputs of ML models, including surface absorptivity (ε), density (ρ), specific heat (Cp), thermal conductivity (k), critical temperature (Tcri), and incident heat flux (HF). By tuning hyperparameters, the neuron number of BPNN1 (Nh,1), neuron numbers in hidden layers of BPNN2 (Nh,1 and Nh,2), penalty parameter (C) and shape parameter (γ) of kernel function of SVR were optimized. Accuracy, convergence efficiency, and robustness of three models were compared using multiple statistical metrics. Feature importance of inputs was analyzed using two methods. Reliability of the models was verified by comparing with experimentally measured tig of five polymers. The results show that the optimal Nh,1 of BPNN1 is 34; the optimal Nh,1 and Nh,2 of BPNN2 are 11 and 10; the optimal C and γ of SVR are 7 and 5. Accuracy, convergence efficiency, and residual of the three models share the same ranking of BPNN2 > BPNN1 > SVR, whereas SVR exhibits highest robustness when treating incomplete datasets. Tcri poses greatest impact on tig followed by ε and then HF, while k, ρ, and Cp exert approximately identical least effect on tig. Measured tig are relatively well predicted by the ML models.