Test: SI & CI Engines - 2 - Mechanical Engineering MCQ

Match List I with List II and select the correct answer  

Match List I (Air-fuel ratio by mass) with List II (Engine operation mode) and select the correct answer using the codes given below the Lists  

Auto -ignition time for petrol- air mixture is minimum when the ratio of actual fuel-air ratio and chemically correct fuel air ratio is 

Assertion (A): In SI engines, as the engine speed increases, spark is required to be advanced.Reason (R): As the engine speed increases, flame velocity increases.  

By higher octane number of SI fuel, it is meant that the fuel has 

Consider the following statements: 
1. In the SI engines detonation occurs near the end of combustion whereas in CI engines knocking occurs near the beginning of combustion.
2. In SI engines no problems are encountered on account of pre-ignition.
3. Low inlet pressure and temperature reduce knocking tendency in SI engines but increase the knocking tendency in CI engines.
Which of the statements given above are correct?

List I gives the different terms related to combustion while List II gives the outcome of the events that follow. Match List I with List II and select the correct answer. 
List I                                           List II
A. Association                           1. Pseudo shock
B. Dissociation                          2. Knock
C. Flame front                           3. Endothermic
D. Abnormal combustion        4. Exothermic
Code: A B C D                     A B C D
       (a) 3 4 1 2                (b) 4 3 1 2
       (c) 3 4 2 1                (d) 4 3 2 1

Consider the following statements:  
In order to prevent detonation in a spark-ignition engine, the charge awayfrom the spark plug should have
1. Low temperature
2. Low density
3. Long ignition delay
Which of the statements given above is/are correct?

Which of the following action(s) increaser(s) the knocking tendency in the S I.engine? 

In a SI engine, combustion stage I takes 1 ms and combustion stage II takes1·5 ms when the engine runs at 1000 rpm. If stage I time duration isindependent of engine speed what will be the additional spark advancenecessary when the engine speed is doubled?  

Consider the following statements: 
Knock in the SI engine can be reduced by
1. Supercharging
2. Retarding the spark.
3. Using a fuel of long straight chain structure
4. Increasing the engine speed.
Of these correct statements are

Consider the following statements: 
Detonation in the S.I. engine can be suppressed by
1. Retarding the spark timing.
2. Increasing the engine speed.
3. Using 10% rich mixture.
Of these statements

Consider the following statements relevant to the ignition system of SI engine:
1. Too small a dwell angle will lead to the burning of condenser and contactpoints
2. Too small a dwell angle will result in misfiring.  
3. Too large a dwell angle will result in burning of condenser and contactpoints.
4. Too large a dwell angle will result in misfiring.
Which of the above statements are correct?

Which of the following feature(s) is/are used in the combustion chamber design to reduce S.I engine knock? 

A two-stroke engine has a speed of 750 rpm. A four-stroke engine having anidentical cylinder size runs at 1500 rpm. The theoretical output of the two stroke engine will

If the approximate average mean pressures during induction, compression,power and exhaust strokes of an internal combustion engine are respectively15 kN/m² below atmosphere, 200 kN/m² above atmosphere, 1000 kN/m² above atmosphere and 20 kN/m² above atmosphere, then the resultant mean effective pressure, in kN/m² , is 

Which of the following statements is "true"? 

Assertion (A): A very high compression ratio is favoured for a CI engine, in order toattain high mechanical efficiency without knocking.  
Reason (R): The delay period in CI combustion affects rate of pressure rise and hence knocking.

Consider the following measures: 
1. Increasing the compression ratio
2. Increasing the intake air temperature.
3. Increasing the length to diameter ratio of the cylinder.
4. Increasing the engine speed.The measures necessary to reduce the tendency to knock in CI engines wouldinclude

The knocking tendency in compression ignition engines increases with:

Which of the following factors would increase the probability of knock in theCI engines?
1. Long ignition delay of fuel
2. High self ignition temperature of fuel
3. Low volatility of fuel 
Select the correct answer using the codes given below:

Hypothetical pressure diagram fora compression ignition engine is shown in the given figure. The diesel knock is generated during the period

Which of the following factor(s) increase(s) the tendency for knocking in theC.I. engine?  

The object of providing masked inlet valve in the air passage of compressionignitionengines is to 

The tendency of knocking in C I engine reduces by  

If the performance of diesel engines of different sizes, cylinder dimensionsand power ratings are to be compared, which of the following parameters canbe used for such comparison? 

In the operation of four-stroke diesel engines, the term ‘squish’ refers to the: