Đang chuẩn bị nút TẢI XUỐNG, xin hãy chờ
Tải xuống
Tham khảo tài liệu 'internal combustion engines fundamentals episode 1 part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 132 INTERNAL COMBUSTION ENGINE FUNDAMENTALS FIGURE 4-11 Specific heat at constant pressure cJR as function of temperature for species COj HjO O2 N2 Hj and co. From JANAF tables.11 t2 t3 t4 A hf Afi t Af2 y Af3 Aft --------------- Af6 Afg 4.43 s where t T K 1000. Af6 is the constant for the datum of zero enthalpy for c M H2 o2 and N2 at 298.15 K. For a 0 K datum Afg is added to Afg. For pure n hydrocarbon compounds the coefficients Afi were found by fitting Eqs. 4.42 B and 4.43 to data from Rossini et al.16 Values for relevant pure fuels are given in Table 4.11. The units for CPJ are cal gmol K and for itf are kcal gmol. Multicomponent fuel coefficients were determined as follows.14 Chemical analysis of the fuel was performed to obtain the H C ratio average molecular weight heating value and the weight percent of aromatics olefins and total paraffins including cycloparaffins . The fuel was then modeled as composed of a representative aromatic olefin and paraffin hydrocarbon. From atomic conservation of hydrogen and carbon and the chemical analysis results component molar fractions and average carbon numbers can be determined. Table 4.11 gives values for the coefficients Afl to Afg for typical petroleum-based fuels. The units of the coefficients give cpf and hf in cal gmol-K and kcal gmol respectively with t T K Iooo7 Coefficients for polynomials Eqs. 4.42 and 4.43 1 for fuel enthalpy and specific heat Molecular Fuel Formula weight A F F A Ar. At A Methane CH 16.04 17.23 0.0580 -0.29149 26.327 -10.610 1.5656 0.16573 -18.331 4.3000 133 134 INTERNAL COMBUSTION ENGINE FUNDAMENTALS U kg K 1 FIGURE 4-12 Specific heat at constant pressure of unburned gasoline air burned gas mixtures as function of temperature equivalence ratio and burned gas fraction. Units kJ kg mixture K. FIGURE 4-13 I Ratio of specific heats y cpJc j I of unburned gasoline air burned gas mixtures as function of tern- I perature equivalence ratio and I burned gas fraction. 1 3 PROPERTIES OF WORKING .