Modern Engineering Thermodynamics

13.21 Diesel Cycle 515
Solution
a. The compression ratio CR = 18.0, and the cutoff ratio CO = 2.32, so the Diesel cold ASC thermal efficiency is given by
Eq. (13.36) as
ðη T Þ Diesel
= 1 − ð18:0Þ− 0:40 ½ð2:32Þ 1:40 − 1Š
= 0:617 = 61:7%
1:40ð2:32 − 1Þ
cold ASC
b. The rate of energy provided by burning the fuel is
_Q fuel = ðFuel heating value in kJ/kg-fuelÞ × ðFuel flow rate in kg-fuel/sÞ
= ð45:5 × 10 3 kJ/kg-fuelÞ × ð3:35 kg-fuel/sÞ = 152 × 10 3 kJ/s = 152,000 kW
Then the actual thermal efficiency of the engine is given by Eqs. (7.5) and (13.33) as
c. Since ðη T Þ actual = ðη m Þðη T Þ cold ASC ,
ðη T Þ Diesel
actual
= ð _W B Þ out
= 80,080 = 0:527 = 52:7%
_Q fuel
152,000
η m =
ðη TÞ actual
= 0:525 = 0:851 = 85:1%
ðη T Þ cold ASC
0:617
Exercises
50. Determine the Diesel cold ASC efficiency discussed in Example 13.17 if the compression ratio is decreased to 14.0 to 1.
Assume all other variables remain unchanged. Answer: (η T ) Diesel cold ASC = 61.6%.
51. Find the Diesel cold ASC thermal efficiency of the engine in Example 13.17 if the cutoff ratio is increased to 4.65.
Answer: (η T ) Diesel cold ASC = 61.1%.
52. Calculate the indicated horsepower output for the Diesel engine in Example 13.17. Answer:
ð _W I Þ out
= ðη T Þ Diesel
× _Q fuel = 0:661 × 152,000 kW = 100,500 kW.
cold ASC
53. Determine the actual thermal efficiency of the diesel engine in Example 13.16 if it produces 85,500 kW rather than
80,080 kW. Assume all other variables remain unchanged. Answer: (η T ) Diesel actual = 56.1%.
NO RAY OF LIGHT ON DIESEL MYSTERY
German Inventor Was a Millionaire and His Home Was Happy
Special Cable to The New York Times
LONDON, Oct. 1—Today brought no fresh tidings in regard to Dr. Rudolf Diesel, the oil engine inventor, and that he met his
death by drowning on his way from Antwerp to Harwich on Monday night appears to be certain.
Dr. Diesel’s friends are greatly mystified. While on the one hand the probabilities of an accidental fall overboard seem
remote, on the other hand they cannot conceive any motive which might prompt a suggestion of suicide.
Dr. Diesel was a wealthy man. His patent rights in the Diesel engine were sold for huge sums in various countries, and,
having amassed a fortune, he had to all intents and purposes retired from active business. It is believed that he amassed a
fortune of $2,500,000 in a few years.
Sidney Whitman, the oldest of Dr. Diesel’s English friends, says Dr. Diesel lived in Munich in one of the most palatial
modern houses in Bavaria, which cost $250,000 to build. Mr. Whitman says that when he was in America last year
Dr. Diesel struck up a great friendship with Thomas A. Edison. The latter told him not to eat too much and he would live
to be a hundred.