COURSE: Question on I C Engine Lesson: Question (7-10

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Question 7 For an engine operating on air standard Otto cycle, the clearance volume is 10% of the swept volume. The specific heat ratio of air is 1.4. The air standard cycle efficiency is (a) 38.3% (b) 39.8% (c) 60.2% (d) 61.7%

Solution7 mpression ratio (G)=11 = 1-ry-1-1-(11)14-1 1.4-1 = 0.615 Ans d

Question 8 An ideal air standard Otto cycle has a compression ratio of 8.5. If the ratio of the specific heats of (v) is 1.4/ then what is the thermal efficiency (in percentage) of the Otto cycle? (a) 57.5 (b) 45.7 (c) 52.5 (d) 95

Solution 8 Ng-(1- )-100%-(1-ash )-100.575% ) x100-57.5% 8.5(14-1) Ans : a

Question 9 In an air-standard Otto cycle, the compression ratio is 10. The condition at the beginning of the compression process is 100 kPa and 27 C. Heat added at constant volume is 1500 kJ/kg, while 700 kJ/kg of heat is rejected during the other constant volume process in the cycle. Specific gas constant for air - 0.287 kJ/kgK. The mean effective pressure (in kPa) of the cycle is (a) 103 (b) 310 (c) 515 (d) 1032

Solution 9 area of p -v diagram length of p-v diagram work done 1500 kJ mep- 4 700 KJ AV Q,-Q (V,- V2) (1500-700)KJ (0.861-0.0861)m3 /kg 1032 KPa V. r 101 V. 0.287 x (300) 1100 -0.861 m3 /kg Ans d V2 0.0861

Question 10 In a spark ignition engine working on the ideal Otto cycle, the compression ratio is 5.5. The work output per cycle (i.e., area of the P-V diagram) is equal to 23.625 x 105 x Ve J, where Ve is the clearance volume in m3. The indicated mean effective pressure is (a) 4.295 bar (c) 86.870 bar (b) 5.250 bar (d) 106.300 bar

Solution 10 V. V 3 Work per cycle Piston displacement volume Pa 23.625 x 10x V (V,-V2) N/m2 23.625-10,0% Pa-525bar x V (5.5V,-Vc) Ans : b

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Harshit Aggarwal

Cleared UPSC ESE twice with Rank 63 and 90 in mechanical engg. Got 99 percentile in GATE. Cracked ONGC, BHEL,ISRO, SAIL, GAIL successfully

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Mohnish Lodhi

2 years ago

maza aa gaya,,, good for revision

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KAUSHAL SINGH

2 years ago

sir UPSC did some change in ESE ME ,syllabus and marking scheme for mains ,and prelim examination so can u make a video on this for complete information about that

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Harshit Aggarwal

2 years ago

Okay...i will make a course on this

KAUSHAL SINGH

2 years ago

thanks sir

Akshay Sarpate

a year ago

In IES exam, calculator is not allowed. So, How to do calculation regarding efficiency of Engine, ratio of spc. heat,etc?

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Abhishek Verma

a year ago

sir in question no.10 answer is coming 104.92bar

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Suraj prasad singh

a year ago

bro work done will
be equal to the indicated mean effective pressure multiplying with swept volume

Abhishek Verma

a year ago

sir in question no.10 answer is coming 104.92bar

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Abhishek Verma

a year ago

sir in question number 106.313 bar

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Abhishek Verma

a year ago

sir in question number 10 answer is coming 106.313 bar