Analyze an air-standard Otto cycle assuming it is a cold cycle with properties evaluated at 300 K. Air intake and exhaust are at 300 K, 1 bar. After the combustion (heat in) process, the temperature is 2500K. The compression ratio is 9. The volume at bottom dead center is 1 liter.
a. What is the mass of air in the cycle?
b. How much work is produced during expansion?
c. How much work is consumed during compression?
d. How much energy is transferred into the air during heating?
e. What is the thermal efficiency of the cycle?
The biggest problem I am having is identifying which temperature and pressure corresponds to what process. Does air intake and exhaust mean that T1 = 300K?
1 to 2: Isentropic Compression (BDC to TDC)
2 to 3: Constant Vol. heat transfvr to air while piston at TDC.
3 to 4: Isentropic expansion
4 to 1: Constant Vol. where heat rejected from air at BDC
Also, I can do c,d,e once a and b are known, but I need help with those.
The Attempt at a Solution
b) efficiency of turbine n_t = (h1-h2)/(h1-h2s)
h2 = h1 - n_t(h1-h2s)
= 2804.2 -0.75(2804.2 - 2084.63) = 2264.5225
Power of pump Wp_dot = m_dot*(h4-h3)
h4 = h3 + Wp_dot/m_dot = h3 + v3(p4-p3)/n_p
Where n_ p = pump efficiency
h = enthalpy
p = pressure
m_dot = mass flow rate
v = specific volume