# Homework Help: HELP NEED ! Engine cycle Question

1. Mar 22, 2009

### Apple4ever

URGENT HELP NEED ! Engine cycle Question !!!

Q: Data on an engine cycle is presented.if the gas has a compression/expansion index of 1.4, determine the work done(KJ) in the cycle by theoratical and graphical

Given:

Pressure in (Pa)
p1= 1 X 105
p2= 11.764 X 105
p3= 11.764X105
p4=2.207X105

Volume in M3

v1=0.826
v2=0.142
v3=0.25
v4=0.826

T1 (Temperature at state 1) = 293.15 K
Specific heat capacity at constant pressure = 1000 J/KgK
Specific Gas Constant = 287J/KgK

Calculate the Work done and Thermal Efficiency(%) for the Cycle

::: Theratical :::
i drew a p-v diagram as below;

check the attachment

i found T2 = 592.84
T3= 1046.61 K
T4 = 15.6 K

im bit unsure about the T4 calculation

T1 is given as above.

now im going to find the enthalpy using specific heat constant and temperature at each cycle 1-2 ,2-3,3-4,4-1 to find the work and heat for each process.

QUESTION:

Is this the correct way of solving this or is there any other easy way of solving this problem??

#### Attached Files:

• ###### Untitled.jpg
File size:
11 KB
Views:
112
Last edited: Mar 23, 2009
2. Mar 22, 2009

### xxChrisxx

Re: URGENT HELP NEED ! Engine cycle Question !!!

How do you find work from a closed loop cycle? Think about how you'd find distance travelled from a velocity time graph.

Also think about what you've got. PV and its a gas so what equations do you think? Also as this is closed internal energy is important, how do you find internal energy from temperature?

Last edited: Mar 22, 2009
3. Mar 22, 2009

### Apple4ever

Re: URGENT HELP NEED ! Engine cycle Question !!!

thanks a lot for replying chirsxx.
did u check the p-v diagram i drew for this process ? is that correct?

Last edited: Mar 23, 2009
4. Mar 22, 2009

### xxChrisxx

Re: URGENT HELP NEED ! Engine cycle Question !!!

In steam tables, the working fluid is water. This is an air standard case, so we use....?
I cant check the p-v diagram as the attachment is pending approval.