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Mechanical Engineering Systems 2008 Part 3

Tham khảo tài liệu 'mechanical engineering systems 2008 part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 42 Thermodynamics P4 V4 P5 V . IS y ì QKQ l 1.4 V4 y 1.358 V3 V V5 60 hlvr a IS t- 1 1 ppp I 0.4 TT 1573 I 1 . 8 c 586.5K vj 16 Vc Heat energy supplied m.cv T3 - T2 m.Cp T4 - T3 0.717 1159 - 918 1.004 1573 - 1159 using a mass of 1kg 173 416 589kJ kg Heat energy rejected m.cv T5 - T1 0.717 586.5 - 303 203.3 kJ kg heat rejected Air standard efficiency 1 - -- - - heat supplied 1 - 203 0.6548 589 65.48 Problems 2.4.1 1 A petrol engine working on the Otto cycle has a compression ratio of 9 1 and at the beginning of compression the temperature is 32 C. After heat energy supply at constant volume the temperature is 1700 C. The index of compression and expansion is 1.4. Calculate a temperature at the end of compression b temperature at the end of expansion c air standard efficiency of the cycle. 2 In a diesel cycle the pressure and temperature of the air at the start of compression are 1 bar and 57 C respectively. The volume compression ratio is 16 and the energy added at constant pressure is 1250kJ kg. Calculate a theoretical cycle efficiency b mean effective pressure. 3 The swept volume of an engine working on the ideal dual combustion cycle is 0.1068 m3 and the clearance volume is 8900 cm3. At the beginning of compression the pressure is 1 bar and temperature is 42 C. If the temperature after Thermodynamics 43 expansion is 450 C the maximum temperature 1500 C and the maximum pressure 45 bar calculate the air standard efficiency of the cycle. 7 1.4 cv 0.715 J kgK 4 A compression ignition engine cycle is represented by compression according to the law pV135 C 1160kJ kg of heat energy supplied at constant pressure expansion according to the law pV1.3 C back to the initial volume at bottom dead centre and completed by heat rejection at constant volume. The initial conditions are 1 bar 43 C and the compression ratio is 13 1. Assuming air to be the working fluid throughout determine the heat transfer per kg during a the compression process b the expansion process c the .