Question

Problem #3 (Total marks-14) Given: An engine has the following operating conditions per air-standard Otto cycle: Gasolina (SI) TYCO engine Pressure at beginning of compression process (Pal state 1 Temperature at beginning of compression process state 1) Volumetric compression ratio , Specific heat added during combustion process ( k g) (process 273) 300 1400 Data used for constant Specific Heat (standard cold-air assumption) Method: Ic ... 1.005 kJ/kg. K(C) = 0.718 kJ/kg.K. k=1.400, R -0.287 kJkgK Required: Draw a clear schematic diagram showing basic arrangement of a one-cylinder gasoline engine. Indicate the main components on the schematic diagram. Using systematic step-by-step approach of mass and energy system analysis and the standard cold-air assumption (constant specific heat) method, calculate the following (state your assumptions whenever applicable, and justify the equations used) - circle your final answers: (a) The pressure (in kPa) and temperature (in K) at the end of the compression process (process 12); (b) The specific volumes (in m®/kg) at the TDC and BDC positions of the piston: (c) The maximum pressure (in kPa) and maximum temperature (in K) in the cycle, (d) The pressure (in kPa) and temperature (in K) at the end of the expansion process/power stroke (process 3–4): (0) The specific network (in kJ/kg) produced by the cycle: (h) The cycle thermal efficiency (in %): (9) The mean effective pressure MEP in kPa): (h) Draw clear T-s and p-v diagrams with labeled data (related calculated results) on the diagrams representing this cycle: (1) The maximum temperature in the cycle, the specific network output, the mean effective pressure, and thermal efficiency using the variable specific heat method. Data for the variable specific heat method is given on the next page. Briefly, compare your results with the above results in a Table form). () Explain using qualitative T-s and p-v diagrams how Atkinson cycle differs from Otto cycle: (k) Using the standard cold-air assumption method, determine the specific network output, the mean effective pressure and thermal efficiency values assuming an Atkinson cycle operating under the same conditions as given in the Table above. Compare your results with that of Otto cycle results determined earlier (use a Table form for comparison) 11/20

Answer 1

otto Cycle V-c Po wout (s:c) 7 din Win (s=c)' Qout (VEC) P = 100 kPa Ti= 300k (2-3 = 1400 kJ/kg (p= 1.005 kJ/eg-k , Cy= 0.718 kJ/kg - R = 287 5/legak Isentropic compression 1-2 P2=2000 kla - Ansa [9.57*non T2 = 706.136k - Ansa

P. Vi = RT 100x10² vi= 287 x 300 - = 0.861 m3/leg Ansb P2 V₂ = 8 Tz 2000 x 103 V2 = 287x706.136 V2 = 0.10133 m²/kg Ansb Q2-3 = Cv (Tz-Tz) 1400 = 0.718 (T3-706-136) T3 =2655.99k Ansc Isochoric process 2-3 2000 706.136 2655.99 - P₂ = 7522.62 kPa - Ansc Isentropic process 3-4 7522.62 - [8-5]" Pu = 375.99 kPa - Angd

2655.99 - 2655.99 = [8.5]14-1 - Tu = 1128.389k - Angd W3-4 - Wi-2 Wnet = Cv (T3- Tu) - G (T₂-T.) = Cv (T3- Tu - Tz + T.) 0.718 (2655.99-1128.389 - 706.136+300 Weet = 805.2118 kJ/kg - Anse Lotto : 1 - 1 Hotto = 1 (8.5)1.4-1 hath = 57.515% - Ans f MEP= Whet W-V₂ - 805.2118 0.861-010133 MEP = 1059.95 kPa - Ans