Week 2 : Basic Calibration of Single cylinder SI-Engine

                                                             Calibration of Single cylinder SI-Engine

Aim: To run analysis for SI engine.

Objective: 1.Run the case at 1800 rpm and list down important parameters

• air flow rate
• BMEP
• BSFC
• In-cylinder pressure

2. Increase the power output at 3600 rpm by 10%

Theory:

A spark-ignition engine (SI engine) is an internal combustion engine, where the combustion process of the air-fuel mixture is ignited by a spark from a spark plug. In contrast to compression-ignition engine, typically diesel engines, where the heat generated from compression together with the injection of fuel is enough to initiate the combustion process, without needing any external spark.

WORKING OF THE SI ENGINE:

The working cycle of both spark-ignition and compression-ignition engines may be either two-stroke or four-stroke.

A four-stroke spark-ignition engine is an otto cycle engine. It consists of following four strokes: suction or intake stroke, compression stroke, expansion or power stroke, exhaust stroke. Each stroke consists of 180 degree rotation of crankshaft rotation and hence a four-stroke cycle is completed through 720 degree of crank rotation. Thus for one complete cycle there is only one power stroke while the crankshaft turns by two or more revolutions.

In-contrast to 2-stroke engine where a power-stroke takes place during a single rotation of the crank-shaft.

Some important parameters :

Air-flow rate:

The amount of air that is entering the engine and it is important because it decides how the fuel combustion takes place. A low air flow produces incomplete combustion leading to CO emissions whereas a higher air flow leads to NOx emissions. Therefore, an air flow close to stoichiometry is desired.

Break Mean Effective Pressure ( BMEP ):

The ratio of gross work-done per cycle to the volume displaced per cycle. It provides a valuable measure of the engine performance which is independent of the engine displacement.

Brake Specific Fuel Consumption ( BSFC ):

The amount of fuel consumed per unit power produced in a cycle. Low values of BFSC are desirable

In-cylinder pressure:

The maximum pressure that is developed inside the engine during a single cycle. It provides a measure of the work that can be extracted from the engine.

Setup:

Open the SI engine

Case setup:

Injection parameter:

Inlet:

Outlet:

Simulation  setup:

Post results:

In- cylinde pressure:

BMEP:

P-V diagram:

T-S diagram:

Engine geometry:

Engine performance :

 2. To increase power output at 3600 rpm.

Tune to 3600 rpm and increase the bore length.

P-V diagram:

T-S diagram:

Temperaure plot:

Engine geometry:

Engine performace:

Post results:

Brake power and torque is increased by 10% by changing the bore length.

Conclusion:

Post results is obtained for both the cases.

Power output is increase bt 10%.