Vol V_c*(1+(CR-1)/2*(R+1-cos(phi)-sqrt(R^2-sin(phi)^2))) Cylinder volume V_s pi*D^2/4*S Swept volume V_c V_s/(CR-1) Clearance volume phi t*2*pi*N/60-pi Crank angle (rad) crank_angle phi*180/pi Crank angle (deg) 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 Initial CH2O mole fraction c_CH4_0 x_CH4*p_init/(Rg*T_init) Initial CH4 concentration c_O2_0 x_O2*p_init/(Rg*T_init) Initial O2 concentration c_N2_0 x_N2*p_init/(Rg*T_init) Initial N2 concentration c_CH2O_0 x_CH2O*p_init/(Rg*T_init) Initial CH2O concentration