Engineering, 14.04.2020 22:21 angelespinosa521

Determine the mean effective pressure of an ideal Otto cycle that uses air as the working fluid if its state at the beginning of the compression is 14 psia and 60°F, its temperature at the end of the combustion is 1500°F, and its compression ratio is 9. Use constant specific heats at room temperature. The properties of air at room temperature are R = 0.3704 psia·ft3/lbm·R, cp = 0.240 Btu/lbm·R, cv = 0.171 Btu/lbm·R, and k = 1.4.

Answers: 1

Show answers

Answers

Answer from: BrainGeek4848

The mean effective pressure of the ideal Otto Cycle that uses air as the working fluid is; 31.28 psia

We are given;

Initial pressure; P₁ = 14 psia

Initial temperature; T₁ = 60°F = 520 R

Maximum temperature; T₃ = 1500°F = 1960 R

Compression ratio = 9

From tables, the specific heat capacities and constants are;

c_v = 0.171 btu/lbm.R c_p = 0.24 btu/lbm.R R = 0.3704 btu/lbm.R ratio of specific heats; k = 1.4

Let us first calculate the initial volume from the formula;

V₁ = RT₁/P₁

V₁ = (0.3704 * 520)/14

V₁ = 13.7577 ft³/lb.m

Compression ratio is; V₁/V₂ = 9

Thus;

V₂ = V₁/9

V₂ = 13.7577/9

V₂ = 1.5286 ft³/lb.m

To get the temperature T₂, we will use the formula;

T₂ = T₁(V₁/V₂)^(k - 1)

T₂ = 520(9)^(1.4 - 1)

T₂ = 1252.277 R

Similarly;

T₄ = T₃/9

T₄ = 1960/(9^(1.4 - 1))

T₄ = 813.87 R

Formula for heat entering and heat exiting are;

Q_in = c_v(T₃ - T₂)

Thus;

Q_in = 0.171(1960 - 1252.277)

Q_in = 121.02 btu/lbm

Q_out = c_v(T₄ - T₁)

Q_out = 0.171(813.87 - 520)

Q_out = 50.251 btu/lbm

Net work done is given by;

W_net = Q_in - Q_out

W_net = 121.02 - 50.251

W_net = 70.769 btu/lbm

Formula for the mean effective pressure is;

mean effective pressure = W_net/(V₁ - V₂)

mean effective pressure = 70.769/(13.7577 - 1.5286)

mean effective pressure = 5.7869 btu.ft³

Converting to psia gives;

Mean effective pressure = 31.28 psia

Read more about compression ratio at; link

Answer from: jaquezdaking4919

The mean effective pressure of the Otto cycle is 31.268 psi

Explanation:

The mean effective pressure is obtained by dividing the work done in the working stroke process of the cycle by the volume of the stroke ar the stroke volume.

In the Otto cycle, therefore, we are to apply an expression for the work done and the volume of the Otto cycle stroke to derive the value of the mean effective pressure as follows.

Here we have the mean effective pressure given by

MEP $\frac{w_{net}}{\alpha _1 - \alpha_1 }$

$= \frac{Heat\, Supplied - Rejected \, Heat}{\alpha_1 -\frac{\alpha_1 }{r} }$

= $\frac{q_{in} -q_{out}}{\alpha_1-\frac{\alpha_1 }{r} }$

$=\frac{P_1}{RT_1} \frac{r}{r-1} (c_v(T_3-T_2)-c_v(T_4 - T_1))$

$=\frac{P_1}{RT_1} \frac{c_v r}{r-1} (T_3(1-r^{1-k})+T_1(1 - r^{k-1}))$

= $=\frac{14\cdot 0.171 \cdot 9}{(9-1)\cdot 0.06855 \cdot 520} (1960(1-9^{1-1.4})+520(1-9^{1.4-1}))$

31.268 psi.

Answer from: Quest

answer:

i dont know the answer but good luck

explanation:

Answer from: Quest

Idon’t do engeneering classes sorry

Another question on Engineering

Engineering, 04.07.2019 08:10

Which of the following is an easy way to remember the modified “x” tire rotation? a. nondrive wheels straight, cross the drive wheels b. drive wheels straight, cross the nondrive wheels c. drive wheels crossed, nondrive wheels straight d. drive wheels crossed, nondrive wheels crossed

Answers: 1

Answer

Engineering, 04.07.2019 18:10

What difference(s) did you notice using a pneumatic circuit over hydraulic circuit.explain why the pneumatic piston stumbles when it hits an obstacle.

Answers: 2

Answer

Engineering, 04.07.2019 18:10

If a particle moves along a path such that r : (3 sin t) m and ? : 2t rad, where t is in seconds. what is the particle's acceleration in m/s in 4 seconds? a)- 16.43 b)- 16.29 c)- 15.21 d)- 13.79

Answers: 1

Answer

Engineering, 04.07.2019 18:10

Ajournal bearing has a journal diameter of 3.250 in with a unilateral tolerance of 20.003 in. the bushing bore has a diameter of 3.256 in and a unilateral tolerance of 0.004 in. the bushing is 2.8 in long and supports a 700-lbf load. the journal speed is 900 rev/min. find the minimum oil film thickness and the maximum film pressure for both sae 20 and sae 20w-30 lubricants, for the tightest assembly if the operating film temperature is 160°f. a computer code is appropriate for solving this problem.

Answers: 3

Answer

You know the right answer?

Determine the mean effective pressure of an ideal Otto cycle that uses air as the working fluid if i...

Questions