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MCQOPTIONS
This section includes 471 Mcqs, each offering curated multiple-choice questions to sharpen your Uncategorized topics knowledge and support exam preparation. Choose a topic below to get started.
| 101. |
Reason for not using very high suction pressure in an engine with the help of supercharger / turbocharger are |
| A. | high mean wall and exhaust gas temprature |
| B. | increased detonation in si engine |
| C. | increased weight |
| D. | all of the above |
| Answer» E. | |
| 102. |
superchargin is usually is not employed in si engine in the following cases |
| A. | static or mobile enigne |
| B. | static engine at high altitude |
| C. | aero enignes at the time of take off |
| D. | none of the above |
| Answer» B. static engine at high altitude | |
| 103. |
superchargin in ci engine is limited by |
| A. | peak pressure and temprature in cylinder |
| B. | mean cylinder wall tempratuer |
| C. | load on bearing and fuel economy |
| D. | all of the above |
| Answer» D. all of the above | |
| 104. |
A theory in which chain carriers are formed in one step and destroyed in the next step relate to the theory of combustion as |
| A. | preferencial burning of carbon |
| B. | chain reaction theory |
| C. | hydroxylation theory |
| D. | none of the above |
| Answer» C. hydroxylation theory | |
| 105. |
Angle tuned by crank between the point of spark and formation of flame is called |
| A. | igniton lag |
| B. | ignition delay period |
| C. | ignition delay angle |
| D. | either a or b |
| Answer» D. either a or b | |
| 106. |
In a vertical engine, the crank angle before TDC at the instant spark is given is called |
| A. | igniton lag |
| B. | ignition delay period |
| C. | ignition delay angle |
| D. | angle of spark advance |
| Answer» E. | |
| 107. |
The travel of flame speed (m/s) in the S.I. combustion chamber is approximately |
| A. | 5 to 15 |
| B. | 15 to 35 |
| C. | 35 to 50 |
| D. | > 50 |
| Answer» C. 35 to 50 | |
| 108. |
Time interval between instant the spark is given and the point a tiny flame appears is called |
| A. | igniton lag |
| B. | ignition delay period |
| C. | ignition delay angle |
| D. | either a or b |
| Answer» E. | |
| 109. |
Ignition lag in S.I. engine reduces due to |
| A. | increase in pressure,temperature and compression ratio |
| B. | decrease in pressure,temperature and compression ratio |
| C. | decrease in residual gases |
| D. | both a and c |
| Answer» E. | |
| 110. |
The maximum resistance to detonation is by the fuel |
| A. | iso octane |
| B. | n heptane |
| C. | alpha methyl nonane |
| D. | cetane |
| Answer» B. n heptane | |
| 111. |
Pre-ignition takes place when____ |
| A. | flame reaches the unburnt charge before delay period is over |
| B. | ignition takes place after spark |
| C. | ignition starts before spark |
| D. | flame travels very fast |
| Answer» D. flame travels very fast | |
| 112. |
Minimum ignition lag is obtained when |
| A. | rich mixture(5 to 10%) |
| B. | stoichiometric mixture |
| C. | lean mixture |
| D. | very rich mixture(15 to 30%) |
| Answer» B. stoichiometric mixture | |
| 113. |
Maximum efficiency from the S I engine can be obtained |
| A. | at any air fuel ratio |
| B. | depends on working condition of the engine |
| C. | leaner mixture region compared to stoichiometric conditions |
| D. | in the region of richer air-fuel ratio compared to stoichiometric conditions |
| Answer» E. | |
| 114. |
Ignition delay period with increase in speed |
| A. | increases |
| B. | decreases |
| C. | remains same |
| D. | none of the above |
| Answer» D. none of the above | |
| 115. |
Ignition delay angle________with increase in speed |
| A. | increases |
| B. | decreases |
| C. | remains same |
| D. | none of the above |
| Answer» B. decreases | |
| 116. |
The speed of the flame propagation increases with increase in |
| A. | compression ratio |
| B. | suction pressure and temperatur |
| C. | slightly rich mixtures |
| D. | all of the above |
| Answer» E. | |
| 117. |
Approximate tempearture between electrodes of spark plug is |
| A. | 5,000 deg. celsius |
| B. | 20,000 deg. celsius |
| C. | 2,000 deg. celsius |
| D. | 10,000 deg. celsius |
| Answer» E. | |
| 118. |
Increase in speed of the engine________the flame speeds |
| A. | increases |
| B. | decreases |
| C. | doesn t affect |
| D. | none of the above |
| Answer» B. decreases | |
| 119. |
Increase in turbulence________the flame speeds |
| A. | increases |
| B. | decreases |
| C. | doesn t affect |
| D. | none of the above |
| Answer» B. decreases | |
| 120. |
The idle jet does not supply fuel during |
| A. | idling |
| B. | during part load running |
| C. | both a and b |
| D. | none of the above |
| Answer» C. both a and b | |
| 121. |
Gap size in spark plug electrodes is about |
| A. | 10 to 20mm |
| B. | 1 to 2 mm |
| C. | 0.01 mm to 0.1 mm |
| D. | none of the above |
| Answer» C. 0.01 mm to 0.1 mm | |
| 122. |
Flame speed in combustion chamber during flame travel are |
| A. | high at beginning and at the end whereas low in the middle |
| B. | low at beginning and end and high in the middle |
| C. | constant throught |
| D. | cannot predict |
| Answer» C. constant throught | |
| 123. |
Increase in the size of similar engines__________the crank angle turned during flame travel across the cylinder |
| A. | increases |
| B. | decreases |
| C. | doesn t affect |
| D. | none of the above |
| Answer» D. none of the above | |
| 124. |
Self Ignition temperature(SIT) of iso-octane fule(C8H18) is_________ than the SIT of n_heptane fuel(C7H16) |
| A. | higher |
| B. | lower |
| C. | same |
| D. | cannot predict |
| Answer» B. lower | |
| 125. |
autoignition in petrol engine means |
| A. | ignition of fuel due to spark |
| B. | ignition of mixture at the end of compression stroke |
| C. | ignition of mixture without flame front reaches to it |
| D. | none of the above |
| Answer» D. none of the above | |
| 126. |
Abnormal combustion in SI engine relates to |
| A. | rapid and uniform rate of pressure rise due to combustion |
| B. | rapid release of energy in some part of combustion chamber without flame front |
| C. | both a and b |
| D. | none of the above |
| Answer» C. both a and b | |
| 127. |
Detonation in SI engines takes place when |
| A. | end part of charges reaches to sit and its delay period is over |
| B. | the flame front reaches to end of the part of the charge |
| C. | the flame front doesn t reach to end part of the charge |
| D. | both a and c |
| Answer» E. | |
| 128. |
Detonation in SI engine may result into |
| A. | loss of the power and efficiency |
| B. | pre-ignition |
| C. | failure of spark plug |
| D. | all of the above |
| Answer» E. | |
| 129. |
A spark plug should be located at the |
| A. | center of cylinder head |
| B. | near the inlet valve |
| C. | near the exhaust valve |
| D. | none of the above |
| Answer» B. near the inlet valve | |
| 130. |
Pre-igntion can occur |
| A. | diesel engine |
| B. | petrol engine |
| C. | both in petrol and diesel engines |
| D. | none of the above |
| Answer» C. both in petrol and diesel engines | |
| 131. |
Use of two spark plugs in middle of cylinder head causes detonation tendancy to |
| A. | increases |
| B. | reduce |
| C. | remains same |
| D. | none of the above |
| Answer» C. remains same | |
| 132. |
Detonation in SI engine may be decreased by |
| A. | reduction in suction pressure and temperature |
| B. | reducing cr |
| C. | reduction in coolant temperature |
| D. | all of the above |
| Answer» E. | |
| 133. |
Increased load on engine may_______ the detonation in SI engine |
| A. | increase |
| B. | decrease |
| C. | have no effect |
| D. | none of the above |
| Answer» B. decrease | |
| 134. |
SI engines are |
| A. | always over loaded |
| B. | never over loaded |
| C. | both a and b |
| D. | it does not matter |
| Answer» C. both a and b | |
| 135. |
Which of the following factor decreases detonation in SI engines |
| A. | increased cr |
| B. | advancing the spark timing |
| C. | larger sized engine |
| D. | fuels with high s. i.t. |
| Answer» E. | |
| 136. |
Detonation in SI engine means |
| A. | sudden ignition of charge before delay period is over |
| B. | pre-ignition of charge before the spark |
| C. | auto-ignition of charge before the spark |
| D. | auto-ignition of charge after the delay period is over |
| Answer» E. | |
| 137. |
Larger combustion chambers |
| A. | increase detonation |
| B. | decrease detonation |
| C. | do not affect detonation |
| D. | cant say |
| Answer» B. decrease detonation | |
| 138. |
The carburetion does not perform this function |
| A. | atomization |
| B. | vaporization |
| C. | mixing air and fuel in right proportion |
| D. | increasing the temperature of the mixture near to its ignition point |
| Answer» E. | |
| 139. |
To reduce detonation the charge away from spark plug should have |
| A. | low density |
| B. | high ignition delay period |
| C. | lean mixture |
| D. | all of the above |
| Answer» E. | |
| 140. |
The process of carburettion depends on |
| A. | speed of engine |
| B. | temperature of suction air |
| C. | volatility of fuel |
| D. | all of the above |
| Answer» E. | |
| 141. |
Volatility of the fuel affects following processes in S I engine |
| A. | mixing of fuel with air |
| B. | vaporization and distribution of fuel |
| C. | both a and b |
| D. | none of the above |
| Answer» D. none of the above | |
| 142. |
Which air fuel ratio gives minimum BSFC |
| A. | 1970-01-01 15:01:00 |
| B. | 1970-01-01 16:01:00 |
| C. | 1970-01-01 19:01:00 |
| D. | 1970-01-01 12:01:00 |
| Answer» C. 1970-01-01 19:01:00 | |
| 143. |
Time available in seconds for process of carburettion at about 4000 rpm is about |
| A. | 0.0075 to 0.01 |
| B. | 0.01 to 0.02 |
| C. | 0.03 to 0.04 |
| D. | none of the above |
| Answer» B. 0.01 to 0.02 | |
| 144. |
If cooling water temperature is decreased flame speed___ |
| A. | increases |
| B. | decreases |
| C. | remains same |
| D. | cant predict |
| Answer» C. remains same | |
| 145. |
Compression ratio in SI engine is kept lower than diesel engine |
| A. | to reduce its weight |
| B. | to avoid preignition |
| C. | to improve its thermal efficiency |
| D. | none of the above |
| Answer» C. to improve its thermal efficiency | |
| 146. |
The objectives of SI engine design are |
| A. | high length of flame travel |
| B. | low speed of the flame travel |
| C. | high surface area to volume |
| D. | none of the above |
| Answer» E. | |
| 147. |
A compact engine having design to promote turbulence will________ detonation tendancy |
| A. | increase |
| B. | decrease |
| C. | have no effect |
| D. | none of the above |
| Answer» C. have no effect | |
| 148. |
rope brake dynamometer falls under the category of |
| A. | hydraulic dynamometer |
| B. | transmission type dynamometer |
| C. | mechanical friction type dynamometer |
| D. | torsion type dynamometer |
| Answer» D. torsion type dynamometer | |
| 149. |
Slightly rich mixture (5 to 10%) will ______ knocking in SI engines |
| A. | increase |
| B. | decrease |
| C. | have no effect |
| D. | none of the above |
| Answer» B. decrease | |
| 150. |
Exhaust valves of the SI engine should be |
| A. | kept away from the end charge of the mixture |
| B. | cooled by water jacket |
| C. | kept near from the end charge of the mixture |
| D. | both a and b |
| Answer» E. | |