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Questions (61 - 71)
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In this lesson, questions (61 - 71) 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 (61-71)


  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 61 In the operation of four-stroke diesel engines, the term 'squish' refers to the: (a) Injection of fuel in the pre-combustion chamber (b) Discharge of gases from the pre-combustion chamber (c) Entry of air into the combustion chamber (d) Stripping of fuel from the core


  4. Solution 61 Mixing of the fuel more thoroughly. Improved mixing had to be accomplished by imparting additional motion to the air, most commonly by induction-produced air swirls or a radial movement of the air, called squish, or both, from the outer edge of the piston toward the centre. Various methods have been employed to create this swirl and squish Ans : C


  5. Question 62 The correct sequence of the decreasing order of brake thermal efficiency of the three given basic type of IC engines is (a) 4 stroke CI engine, 4 stroke SI engine, 2 stroke SI engine (b) 4 stroke SI engine, 4 stroke CI engine, 2 stroke SI engine (c) 4 stroke CI engine, 2 stroke SI engine, 4 stroke SI engine (d) 2 stroke SI engine, 4 stroke SI engine, 4 stroke CI engine. Ans a


  6. Question 63 Assertion (A): Knocking in S.I. engines is due to auto-ignition of the end charge while knocking, in C.I. engines are due to auto-ignition of the first charge. Reason (R): Spark ignition engines employ lower compression ratio than diesel engines and the fuel used has a calorific value lower than that of diesel oil (a) Both A and R are individually true and R is the correct explanation of A (b) Both A and R are individually true but R is not the correct explanation of A (c) A is true but R is false (d) A is false but R is true Ans b


  7. Question 64 At the time of starting, idling and low speed operation, the carburretor supplies a mixture which can be termed as (a) Lean (c) stoichiometric (b) slightly leaner than stoichiometric (d) rich Ans : d


  8. Question 65 The essential function of the carburettor in a spark ignition engine is to: (a) Meter the fuel into air stream and amount dictated by the load and speed (b) Bring about mixing of air and fuel to get a homogeneous mixture (c) Vaporise the fuel (d) Distribute fuel uniformly to all cylinders in a multi cylinder engine and also vaporise it Ans a


  9. Question 66 Assertion (A): A simple or elementary carburettor provides progressively rich mixture with increasing air flow Reason (R): The density of the air tends to increase as the rate of air flow increases (a) Both A and R are individually true and R is the correct explanation of A (b) Both A and R are individually true but R is not the correct explanation of A (c) A is true but R is false (d) A is false but R is true Ans: C


  10. Question 67 Oxides of nitrogen in the engine exhaust can be reduced by which of the following methods? 1. Decrease in compression ratio 2. Exhaust gas recirculation 3, Use of 5% lean mixture 4. Use of oxidation catalysts in exhaust manifold Select the correct answer using the code given below: (a) 1 and 2 only (b) 1 and 3 only (c) 1, 2 and 4 (d) 2 and 4 only Ans : c


  11. Question 69 What is the flash point of a liquid fuel? (a) The temperature at which the fuel ignites spontaneously with a bang (b) The temperature at which the fuel emits vapours at a rate which produces an inflammable mixture with air (c) The temperature at which the fuel ignites with a clearly (d) The temperature at which the fuel ignites without a spark Ans :b


  12. Question 71 In a SI Engine, which one of the following is the correct order of the fuels with increasing detonation tendency? (a) Paraffins, Olefins, Naphthenes, Aromatics (b) Aromatics, Naphthenes, Paraffins, Olefins (c) Naphthenes, Olefins, Aromatics, Paraffins (d) Aromatics, Naphthenes, Olefins, Paraffins Ans: d