Bissoy.com
Doctors Medicines MCQs Q&A

Consider the following statements with regard to IC engines: 1. For best fuel economy of spark ignition engines, the fuel-air mixture should be lean 2. With supercharging, the specific consumption in compression ignition engines increases 3. With increase of load, knocking tendency in compression ignition engines increases Which of the above statements are correct?

Consider the following statements with regard to IC engines: 1. For best fuel economy of spark ignition engines, the fuel-air mixture should be lean 2. With supercharging, the specific consumption in compression ignition engines increases 3. With increase of load, knocking tendency in compression ignition engines increases Which of the above statements are correct? Correct Answer 1 and 3 only

Concept:

  • Performance of SI engine

 

[ alt="F1 S.C Madhu 07.04.20 D4" src="//storage.googleapis.com/tb-img/production/20/04/F1_S.C_Madhu_07.04.20_D4.png" style="width: 374px; height: 351px;">

  1. To achieve maximum power and quick speeding/overtaking, the engine needs a rich mixture. (12:1 to 13:1)
  2. To achieve maximum fuel economy the engine needs a leaner air-fuel ratio of 16: 1 to 17: 1

 

  • Effect of Supercharging 
  1. The power output of a supercharged engine is higher than its naturally aspirated counterpart.
  2.  The mechanical efficiencies of supercharged engines are slightly better than the naturally aspirated engines.
  3.  In spite of better mixing and combustion due to reduced delay, a mechanically supercharged Otto engine almost always have specific fuel consumption higher than a naturally aspirated engine.

 

  • The tendency of knocking in CI engine
  1. Due to an increase in load, the knocking tendency in the CI engine increases.
  2. Low ignition temperature, speed reduces knocking tendency.

Related Questions

Which of the following remarks pertaining to supercharging of IC engines are correct? 1. Ideal supercharging increases the output, but decreases the thermal efficiency slightly 2. The indicated mean effective pressure and mechanical efficiency increase with supercharging 3. The permissible amount of supercharging depends on the compression ratio, air-fuel mixture and design of engine 4. Engine friction losses increase with supercharging
Consider the following statements pertaining to supercharging of engines: 1. The power output for a given engine increases 2. The loss of power due to altitude is compensated 3. The increase in supercharging pressure decreases the tendency to detonate in spark ignition engines 4. The mechanical efficiency of supercharged engines is quite high compared to naturally aspirated engines Which of the above statements are correct?
Consider the following statements regarding supercharging of CI engines: 1. Supercharging results in a quieter and smoother operation of a CI engine 2. Supercharging of a CI engine requires an increase in valve overlap 3. The limit of supercharging for a CI engine is reached by thermal and mechanical loading Which of the above statements are correct?
The pie chart given below shows the fuel consumption by five vehicles V1, V2, V3, V4 and V5. In a month total fuel consumption by all five vehicles is 720 litre. Fuel consumption of a particular vehicle is shown in terms of degree with respect to the total fuel consumption by all these five vehicles. J1 = Difference between the fuel consumption of V4 and V5. J2 = Difference between the fuel consumption of V1 and V2. What is the value of J2 – J1?
Consider the following statement with reference to combustion and performance in a four-stroke petrol engine: 1. The auto-ignition temperature of petrol as a fuel is higher than that of diesel oil as a fuel. 2. The highest compression ratio of petrol engines is constrained by the possibility of detonation. 3. A petrol engine is basically less suitable for supercharging than a diesel engine. Which of the above statements are correct?
The advancing of spark timing in spark ignition engines will _________ knocking tendency.
Which of the following statements are true/ false?
1. In the market economy, the prices are determined by the level of demand and supply in the market.
2. Mixed economy is an economic system in which both the private and public sector have equal roles to play.
3. Planned economy is also known as a centralised economy, controlled economy or command economy.
4. In the market economy, governments do not have much role to play.
In petrol engine, using a fixed octane rating fuel and fixed compression ratio, supercharging will _________ the knocking tendency.
Which of the following increase the diesel knocking tendency? 1. Decreased compression ratio 2. Decreased engine speed 3. Retarded injection timing 4. Supercharging
In order to prevent knocking in spark ignition engines, the charge away from the spark plug should have