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Questions (83 - 92)
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In this lesson, questions (83 - 92) have been explained.

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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  1. COURSE: Question on I C Engine Lesson: Question (83-92)


  2. About me Graduated from NIT Nagpur in 2008 Cleared Engineering Services Examination (ESE-UPSC) Exam Got the offer letter from most of the Maharatna and Navratna Companies Cleared GATE Exam Rate, Review, Recommend, Share Follow me on Unacademy at: https://unacademy.in/user/harshit aggarwal


  3. Question 83 During a Morse test on a 4 cylinder engine, the following measurements of brake power were taken at constant speed. All cylinders firing Number 1 cylinder not firing Number 2 cylinder not firing Number 3 cylinder not firing Number 4 cylinder not firing The mechanical efficiency of the engine is (a) 91.53% 3037 kW 2102 kW 2102 kW 2100 kW 2098 kW (b) 85.07% (c) 81.07% (d) 61.22%


  4. Solution 83 Given: . .-3037 kw I.P) 3037-2102-935 kw (I. .),-3037-2102-935 kw (L.P), 3037-2100-937 kw (LP) 3037-2098-939 kw Total L.P. of the cylinder (.P(PP)+IP), 935+935+937+939 3746 kW B.P 3037 Mechanical efficiency of the en3746 81 Ans c


  5. Question 84 Brake thermal efficiency of the three types of reciprocating commonly used in road vehicles are given in the increasing order as (a) 2 stroke Sl engine, 4 stroke Sl engine, 4 stroke Cl engine (b) 2 stroke Sl engine, 4 stroke Cl engine, 4 stroke Sl engine (c) 4 stroke Sl engine, 2 stroke SI engine, 4 stroke Cl engine (d) 4 stroke Cl engine, 4 stroke Sl engine, 2 stroke Sl engine engines Ans : a


  6. Question 85 In a variable speed S.I. engine, the maximum torque occurs at the maximum (a) Speed (c) Indicated power (b) brake power (d) volumetric efficiency Ans: c


  7. Question 86 In a Morse test for a 2-cylinder, 2-stroke, spark ignition engine, the brake power was 9 kW whereas the brake powers of individual cylinders with spark cut of were 4.25 kW and 3.75 kW respectively. The mechanical efficiency of the engine is (a) 90% (b) 80% (c) 45.5% (d) 52.5%


  8. Solution 86 Indicated power of second cylinder is 9 4.254.75 kW and of first engine is 9- 3.75 5.25 kW. Thus total indicated power of engine is 4.75 + 5.25 = 10 kW. Mechanical efficiency of engine- x100 = 90% 10 Ans a


  9. Question 87 Consider the following statements: I. The performance of an S.I. engine can be improved by increasing the compression ratio. II. Fuels of higher octane number can be employed at higher compression ratio. Of these statements (a) Both I and II are true (c) I is true but II is false (b) both I and II are false (d) I is false but II is true Ans d


  10. Question 88 Besides mean effective pressure, the data needed for determining the indicated power of an engine would include (a) Piston diameter, length of stroke and calorific value of fuel (b) Piston diameter, specific fuel consumption and calorific value of fuel (c) Piston diameter, length of stroke and speed of rotation (d) Specific fuel consumption, speed of rotation and torque Ans c


  11. Question 90 Match List-I with List-II and select the correct answer using the codes given below the lists: List-I A. Supercharging B. Morse test C. Heterogeneous combustion 3. Calorific value D. Ignition quality of petrol 4. Aircraft engine List-II 1. Multi-cylinder engine 2. C.I. engine 5. Octane number 6. Single cylinder S.I. engine (a) 425(b) 1 3 42 (c) 542 3 d 4 2 3 Ans: a


  12. Question 92 Which one of the following quantities is assumed constant for an internal combustion engine while estimating its friction power by extrapolation through Willan's line? (a) Brake thermal efficiency (c) Mechanical efficiency Indicated thermal efficiency (d) Volumetric efficiency. Ans b