Muddy points When and where do we use c, and c? Some definitions use du=c dT. Is it ever Explanation of the above comparison between Diesel and Otto. ( MP 2A. 4) 2.A.3 Brayton Cycle The Brayton cycle is the cycle that represents the operation of a gas turbine engine. The simple gas turbine "can be operated in open cycle or closed cycle(recirculating working fluid) modes. as shown below H Fuel Heat Turbine Co Turbine Air Products Q Figure 2A-4: Gas turbine engine operating on the Brayton cycle-(a)open cycle operation, (b) closed cycle operatio Efficiency of the Brayton cycle We derived the ideal Brayton cycle efficiency in Section 1.A Net work per unit mass flow in a Brayton cycle: The net mechanical work of the cycle is given by Net mechanical work/unit mass= wrurbine-Wcompressor compressor=-4h12 burbine =-Ah34=-Ahrurb If kinetic energy changes across the compressor and turbine are neglected, the temperature ratio TR, across the compressor and turbine is related to the enthalpy changes R-1= 2A-52A-5 Muddy points When and where do we use c v and c p ? Some definitions use dU=c v dT. Is it ever dU=c p dT? (MP 2A.3) Explanation of the above comparison between Diesel and Otto. (MP 2A.4) 2.A.3 Brayton Cycle The Brayton cycle is the cycle that represents the operation of a gas turbine engine. The “simple gas turbine” can be operated in open cycle or closed cycle (recirculating working fluid) modes, as shown below. Fuel QH w wnet net Air Products QL Combustion chamber Compressor Turbine Heat exchanger Heat exchanger Compressor Turbine (a) (b) Figure 2A-4: Gas turbine engine operating on the Brayton cycle – (a) open cycle operation, (b) closed cycle operation Efficiency of the Brayton cycle: We derived the ideal Brayton cycle efficiency in Section 1.A: η Brayton γ γ inlet compressorexit T T PR =− =− − 1 1 1 ( )/ 1 . Net work per unit mass flow in a Brayton cycle: The net mechanical work of the cycle is given by: Net mechanical work/unit mass = − w w turbine compressor, where w hh w hh compressor comp turbine turb =− =− =− =− ∆ ∆ ∆ ∆ 12 34 If kinetic energy changes across the compressor and turbine are neglected, the temperature ratio, TR, across the compressor and turbine is related to the enthalpy changes: TR h h h h comp turb −= = 1 1 4 ∆ ∆