PART 2- POWER AND PROPULSION CYCLE 2A -Gas Power and propulsion cycles SB&vW-118,119,11.10,11.11,11.12,1113,11.14] In this section we analyze several gas cycles used in practical applications for propulsion and power generation, using the air standard cycle. The air standard cycle is an the actual cycle behavior, and the term specifically refers to analysis using the folpproximation to assumptions Air is the working fluid(the presence of combustion products is neglected) Combustion is represented by heat transfer from an external heat source The cycle is 'completed' by heat transfer to the surroundings All processes are internally reversible Air is a perfect gas with constant specific heats 2.A. I The Internal combustion engine(Otto Cycle The different processes of an idealized otto cycle (internal combustion engine) are shown in Figure 2A-1 P Adiabatic reversible Q Po V,=V Figure 2A-1: Ideal Otto cycle Intake stroke, gasoline vapor and air drawn into engine (5->1) i1. Compression stroke, P, Tincrease(1->2) ii1. Combustion( spark), short time, essentially constant volume (2->3) Model: heat absorbed from a series of reservoir at temperatures T2 to T3 Power stroke: expansion (3->4) Valve exhaust: valve opens, gas escapes vi.(4->1)Model: rejection of heat to series of reservoirs at temperatures T4 to TI vil. Exhaust stroke, piston pushes remaining combustion products out of chamber 1->5 2A-12A-1 PART 2 – POWER AND PROPULSION CYCLES 2A – Gas Power and Propulsion Cycles [SB&VW - 11.8, 11.9, 11.10, 11.11, 11.12, 11.13, 11.14] In this section we analyze several gas cycles used in practical applications for propulsion and power generation, using the air standard cycle. The air standard cycle is an approximation to the actual cycle behavior, and the term specifically refers to analysis using the following assumptions: • Air is the working fluid (the presence of combustion products is neglected) • Combustion is represented by heat transfer from an external heat source • The cycle is ‘completed’ by heat transfer to the surroundings • All processes are internally reversible • Air is a perfect gas with constant specific heats 2.A.1 The Internal combustion engine (Otto Cycle) The different processes of an idealized Otto cycle (internal combustion engine) are shown in Figure 2A-1: P V P0 V2 = V3 V1 = V4 5 2 3 4 1 QH QL Adiabatic reversible Figure 2A-1: Ideal Otto cycle i. Intake stroke, gasoline vapor and air drawn into engine (5 -> 1) ii. Compression stroke, P, T increase (1->2) iii. Combustion (spark), short time, essentially constant volume (2->3) Model: heat absorbed from a series of reservoir at temperatures T2 to T3 iv. Power stroke: expansion (3 ->4) v. Valve exhaust: valve opens, gas escapes vi. (4->1) Model: rejection of heat to series of reservoirs at temperatures T4 to T1 vii. Exhaust stroke, piston pushes remaining combustion products out of chamber 1->5