Exploring SI engine tutorial and increasing power output

Run the case at 1800 rpm and list down important parameters 

• airflow rate
• BMEP
• BSFC
• In-cylinder pressure

The below-shown tutorial was loaded and the case setup was run

The case was set up for 1800 RPM as shown below:

The simulation was run for 10 cycles:

The simulation was run and the simulation window and summary are attached below:

Simulation summary:

The above tables provide the following details:

• The simulation converged at 7 cycles
• the simulation took 0.4667 to reach steady state.

Results:

Airflow rate:

The airflow rate is the mass of the air entering into the engine cylinder during the intake process. The airflow rate of our engine is shown in the tabular column below:

From the above table, it is seen that the airflow rate is 24.6 kg/h fo our engine.

Mean Effective Pressures(MEP):

It is an average pressure acting on the piston during the complete thermodynamic cycle in a Reciprocating internal combustion engine.

The different Mean Effective Pressures of our engines are listed below and the values are tabulated.

• IMEP – Indicated Mean Effective Pressure
• BMEP –Brake Mean Effective Pressure
• FMEP – Friction Mean Effective Pressure

From the above table, it is seen that the BMEP is 9.3 bar for our engine.

Brake Specific Fuel Consumption(BFSC):

Brake-specific fuel consumption (BSFC) is a measure of the fuel efficiency of any prime mover that burns fuel and produces rotational or shaft power. It is typically used for comparing the efficiency of internal combustion engines with a shaft output. It is the rate of fuel consumption divided by the power produced.

From the above table, it is seen that the BSFC is 244.2 g/kW-h for our engine

In-cylinder pressure:

Cylinder Pressure is the pressure in the engine cylinder during the 4 strokes of engine operation (intake, compression, combustion and expansion, and exhaust). Pressure during expansion is the most important because that is the cylinder pressure pushing on the piston to produce power.

in cylinder pressure vs crank angle degree plot:

From the above table, it is seen that the maximum pressure for our engine is 48.88 bar.

Increase the power output at 3600 rpm by 10%

The report summary for the engine running at 3600 RPM is attached below:

From the above tables, the power output of the engine at 3600 RPM is found to be 16.3 KW.

In order to increase this power output by 10% following techniques can be used.

1. Increasing the compression ratio.
2. changing the engine geometry.
3. Varying the lambda value.

Thus the following tables show the result of applying the above said techniques. The changed values are highlighted in the following tables.

Results and discussions:

It is seen that the engine brake power increases as the compression ratio increases. This is due to the increase in brake torque at high compression ratios. An increase in the compression ratio induces a greater turning effect on the cylinder crank. That means that the engine is giving more push on the piston, and more torque is generated.

As the compression ratio increases, the fuel mixture is sufficiently compressed thereby increasing the thermal efficiency, so that less fuel is required to produce the same amount of energy.