This calculator evaluates ratio equations, efficiency and effectiveness for the Brayton Cycles.
The following are the variables for the equations.
V = the volume. i.e. V(1) is the volume at state 1.
r(k) is the compression ratio
r(e) is the expansion ratio
r(c) is the cut-off ratio
MEP = mean effective pressure. The constant theoretical pressure would produce the same network in one complete cycle if it acted on the piston. And can be defined as the following:
MEP=DisplacementVolumeNetWorkForOneCycle
η = the efficiency of the cycle
k = the adiabatic index
P = the pressure. i.e. P(1) is the pressure at state 1.
Where: P(1)[D(eff)-N(eff)] = Q(h)-Q(c), Q(h) is the amount of heat initially extracted, and Q(c) is the heat expelled.
WT=mCPΔT
T1T2=T4T3
QA=mCPΔT
Work Calculations
Inputs
m
:100.00g
C(P)
:4.18J/g*K
T (change in temp)
:20.00degC
Output
W
:8,360.00kJ
WP=mCPΔT
Efficiency Calculations
Inputs
W(C)
:20.00kJ
W(T)
:30.00kJ
Output
r(BW)
:0.67
rBW=WTWC
η
:-0.10
η=1−rpkk−11
Net Work and Combustor Calculations
Inputs
P(1)
:40.00atm
P(2)
:100.00atm
T(1)
:25.00degC
T(3)
:35.00degC
T(max)
:25.00degC
T(min)
:30.00degC
Q(air)
:80.00J
Q (fuel)
:100.00J
k
:7.00
Maximum Net Work Results
P(x)
:63.25atm
Px=P1P2
T(2)
:29.58degC
T2=T1T3
r(p)
:0.90
rp=(TminTmax)2k−2k
Combustor Efficiency Results
e(c)
:0.80
ec=QfuelQair
r(B)
:0.65
rB=rpkk−1(T3T1)
Brayton Cycle
In using the calculators and inputting values above, refer to Figure 1 and the different states of the Brayton cycle.
Figure 1: Temperature vs Entropy Graph for a Brayton Cycle
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