T_init 400[K] Initial temperature at BDC p_init 1.5e5[Pa] Initial pressure at BDC La 0.08[m] Crank arm length Lc 0.2693[m] Connecting rod length S 0.16[m] Stroke D 0.13[m] Bore diameter CR 15 Compression ratio N 1500 Engine rpm ER 0.5 Equivalence ratio R Lc/La Length ratio x_CH4 1/(4.76*2/ER+1) Initial CH4 mole fraction x_O2 0.21*(1-x_CH4) Initial O2 mole fraction x_N2 1-x_CH4-x_O2-x_CH2O Initial N2 mole fraction x_CH2O 0.0013 Initial CH2O mole fraction c_CH4_0 x_CH4*p_init/(R_const*T_init) Initial CH4 concentration c_O2_0 x_O2*p_init/(R_const*T_init) Initial O2 concentration c_N2_0 x_N2*p_init/(R_const*T_init) Initial N2 concentration c_CH2O_0 x_CH2O*p_init/(R_const*T_init) Initial CH2O concentration V_s pi*D^2/4*S Swept volume V_c V_s/(CR-1) Clearance volume