COMPARISON OF SPARK IGNITION AND COMPRESSION IGNITION ENGINES

 

https://www.mesubjects.net/wp-admin/post.php?post=7399&action=edit        Otto cycle

https://www.mesubjects.net/wp-admin/post.php?post=12079&action=edit       MCQ Diesel Cycle

https://www.mesubjects.net/wp-admin/post.php?post=7489&action=edit         MCQ Air standard cycles

https://www.mesubjects.net/wp-admin/post.php?post=2549&action=edit       Thermodynamic Cycles

https://www.mesubjects.net/wp-admin/post.php?post=7759&action=edit         Combustion Internal Combustion Engines

https://www.mesubjects.net/wp-admin/post.php?post=7667&action=edit          highlights internal combustion engines

https://www.mesubjects.net/wp-admin/post.php?post=6145&action=edit          Q. Answers internal Combustion engines

https://www.mesubjects.net/wp-admin/post.php?post=3920&action=edit          Scavenging internal combustion engines

https://www.mesubjects.net/wp-admin/post.php?post=3917&action=edit          Terminology internal combustion engines

COMPARISON OF SPARK IGNITION AND

COMPRESSION IGNITION ENGINES

Combustion is a process of burning hydrogen and carbon in the fuel with oxygen. There are major differences in the combustion process in SI and CI engines. These have been tabulated below:

Sr. No.

SI Engine

CI Engine

 

1.

There is a carburetor and a spark plug.

There is no carburetor and no spark plug.

2.

A homogeneous mixture of petrol and air is compressed

Only air is compressed.

At the end of compression stroke, liquid fuel is injected

3.

Compression ratio is between 6 to 10

Compression ratio is between 12 to 20

4.

The mixture is ignited with a spark plug

The fuel starts burning because very high temperature of air after compression

5.

There is can be pre-ignition in SI engines because higher cylinder wall temperature from the last discharge.

There is no pre-ignition in CI engines as only air is compressed.

6.

Just after ignition, flame travels progressively in the rest of the air fuel mixture.

Just after ignition, flame travels through the air and make the air hot.

7.

The entire mixture burns simultaneously.

Fuel is injected over a certain period of time. Thus the fuel burns in a longer period than that of SI engines.

8.

Turbulence within the mixture is highly desirable to increase the speed of combustion.

No Turbulence is required in CI engines.

9.

Amount of fuel burnt depend on load on its engine

Amount of fuel burnt depend on load on its engine

10.

Knocking in SI Engines is at the end of compression

Knocking in CI Engines is at the start of compression

11.

Maximum temperature and pressure are reached in SI engines because of homogeneous mixture.

Lower pressure and lower temperatures are reached in the knocking of CI Engines.

12.

There is an ignition lag in SI engines.

There is an ignition delay. It is time internal between fuel injection and fuel ignition.