(55 points) Hypothetical Air-Standard Cycle.Use Constant Specific Heats A hypoth
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(55 points) Hypothetical Air-Standard Cycle.Use Constant Specific Heats A hypothetical air-standard ideal cycle this is neither an Otto nor a diesel cycle) is executed in a closed system as shown in the P-v diagram below. Air enters at the beginning of the compression process at pi 80 kPa and T 20°C. The compression ratio of the cycle is r vilv, 14. The cut-off ratio is: r. v/vx 1.2 and the pressure ratio across the first stage of heat addition 2 px/pu 1.4 Use constant specific heats with R 0.287 (from to X) is: r kJ/kg-K, k 1.4, c 1.005 kJ/kg-K and c 0.718 kJ/kg-K. 1. 7 points) Describe the processes from 1 to 4 (e sentropic compression) Process description Process (1-2) (2-X) CK-3) (3-4) (4-1)Explanation / Answer
The given PV diagram represnts a combination of Diesel & Otto cycle. Due to the partial working principle of semi diesel engine, It is also called semi diesel cycle, Partly in constant pressure and constant volume, the heat is absorbed in this cycle. It is a combination of two reversible isentropic(adiabatic), two constant volume and one constant pressure processes as shown in the PV diagram.
The details of the process explained below
Isoentropic compression
In this process,the air is compressed, adiabatically and reversibly from a temperature of T1 to T2. No heat released or absorbed by the air during this process.
During this process, the air is heated at constant volume from T2 to TX. Heat absorbed by the air in this process is given by qin= mCv(TX-T2)
In this process, the heating of air occurs at constant pressure from temp TX to T3. The heat absorbed by the air is given by qin= mCp(T3-TX)
Process Process description (1-2)Isoentropic compression
In this process,the air is compressed, adiabatically and reversibly from a temperature of T1 to T2. No heat released or absorbed by the air during this process.
(2-X)During this process, the air is heated at constant volume from T2 to TX. Heat absorbed by the air in this process is given by qin= mCv(TX-T2)
(X-3)In this process, the heating of air occurs at constant pressure from temp TX to T3. The heat absorbed by the air is given by qin= mCp(T3-TX)
(3-4) During this process, the air is expanded adiabatically and reversibly from a temperature of T3 to T4. No heat is absorbed or released during the process. (4-1) In this final process, the air undergoes cooling at constant volume from temperature T4 to T1. Heat released by the air is given by qout= mCv(T4-T1).Related Questions
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