Question

Consider the following statements regarding supercharging of Diesel engines:

1) The mechanical efficiency of a supercharged diesel engine is slightly better than that of the naturally aspirated engine.

2) There is a reduction in smoke in the case of a supercharged engine in the overload operation.

3) Increased valve overlap is used in the supercharged engine.

Which of the above statements are correct?
1. 1, 2 and 3
2. 1 and 2 only
3. 1 and 3 only
4. 2 and 3 only

Answer 1

Correct Answer - Option 1 : 1, 2 and 3

Explanation:

• Supercharging of diesel engine increases mechanical efficiency despite the increase in friction power due to a large increase in brake mean effective pressure or equivalently we can say due to the large increase in brake power.
• The reduction of smoke in the super-charged engine at overload is due to the availability of oxygen in sufficient quantity. In a naturally aspirated engine, this level of smoke is high.
• Due to supercharging heat generation and heat transfer increases.
• As a result of which there is a greater tendency of overheating the piston crown and the seat and edges of exhaust valves.
• To overcome this problem the valve overlap is greater.

Hence all the statements 1,2 and 3 are correct. So, the correct option is an option (1)