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Scott, MIT Graduate
Category: Homework
Satisfied Customers: 3040
Experience:  MIT Graduate (Math, Programming, Science, and Music)
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Consider the thermodynamic efficiency of a Diesel engine.

Customer Question

Consider the thermodynamic efficiency of a Diesel engine. Using equation (2.73) of your
textbook, plot the efficiency of this type of engine for injection ratios ρ between 1and 5
(incrementing by 1) at compression ratios ε of 18, 20, 22, and 24. Note that this is ηth vs ρ
plot at the stated ε values. Describe your observations. Use MATLAB to plot the graphs.
Submitted: 1 year ago.
Category: Homework
Customer: replied 1 year ago.
1- 1/(k ε^k(rho^(k-1)/rho-1)) is equation 2.73
Expert:  Ryan replied 1 year ago.


Thank you for using the site. I'm sorry that you haven't received any reply until now. It seems that your question was initially placed in a different category, and has only recently been moved to the Math category.

I'll be happy to help you with this, but there are a couple of issues that need to be resolved first.

To begin with, I do not have access to MATLAB. I can produce the graphs, just not with MATLAB. If using MATLAB is an absolute requirement from your instructor, then I won't be able to help with this.

Secondly, assuming that a graphing utility other than MATLAB is acceptable, I need you to clarify the equation that needs to be graphed. The text representation that was included in your earlier posting could be interpreted a couple of different ways. Please review the document at the link below and let me know which (if either) of the two equations shown matches with Equation 2.73 in your text. If it is neither, is there a way that you could take a picture of the equation in your textbook and post that?

Here is the link:


Finally, can you describe the desired results? By that, I mean, there are 5 different values of rho and 4 different values of the compression ratio. Is the goal to have:

1) all combinations of rho and the compression ratio on one graph, (i.e. one graph with 20 curves plotted on it), or

2) a separate graph for each value of rho, with each graph showing a curve for each value of the compression ratio (i.e. four curves on each graph), or

3) a separate graph for each value of the compression ratio, with each graph showing a curve for each value of rho (i.e five curves on each graph)

I look forward to hearing from you.



Customer: replied 1 year ago.
no worries...i have solved it
Expert:  Ryan replied 1 year ago.

Ok, no problem.