Internal Combustion Engines (I.C. Engines) MCQ Questions & Answers | Mechanical Engineering

The ratio of the indicated thermal efficiency to the air standard efficiency is known as Relative efficiency

Volatility of diesel fuel oil is Indicated by 90% distillation temperature, i.e., when 90% of sample oil has distilled off. Volatility refers to how easily a fuel vaporizes. It affects how easily you can start your car, warm it up, and how well it runs. Diesel fuel comes in two basic grades, each with a different volatility. Automobiles use one and large trucks do better on the other.

Installation of supercharger on a four cycle diesel engine can result in the following percentage increase in power Up to 100%

The operation of forcing additional air under pressure into the engine cylinder is known as Supercharging

In an internal combustion engine, the process of removing the burnt gases from the combustion chamber of the engine cylinder is known as Scavenging. Scavenging is a process of pushing exhaust gas out of the cylinder and drawing in fresh draught of air or air fuel mixture for the next cycle. The process is essential in having a smooth running of I.C. Engine. If scavenging is incomplete the following stroke will begin with a mix of exhaust fumes rather than clean air. This may be insufficient for poor combustion which leading to poor running condition on an engine.

The operation of forcing additional air under pressure in the engine cylinder is known as Supercharging

The knock in diesel engine occurs due to Instantaneous and rapid burning of the first part of the charge. Diesel engine knocks when there is accumulation of fuel in the combustion chamber which happens when the injected fuel fails to burn as there will a huge delay period. And at a specific time all mixture burns simultaneously which causes increase in peak pressure and shock waves travel at higher speeds and can lead to permanent damage to piston crown and cylinder wall and head.

An engine indicator is used to determine m.e.p. and I.H.P. An engine indicator is an instrument for graphically recording the pressure versus piston displacement through an engine stroke cycle. Engineers use the resulting diagram to check the design and performance of the engine.

Morse test is used to determine the I.P. of a Multi cylinder engine

The delay period in compression ignition engines depends upon:
- Temperature and pressure in the cylinder at the time of injection.
- Nature of the fuel mixture strength.
- Relative velocity between the fuel injection and air turbulence pressure of residual gases.