To perform 1D simulation on single cylinder SI engine and conduct study to increase power output by 10% using GT-SUITE.

Objective: To perform a 1D simulation of the Single Cylinder SI engine using GT-SUITE.

1. List down following parameters (for= 1800 RPM)

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

2. Increase power output by 30% @ RPM= 3600.

Given: Copy 1CySI-Final.gtm from a tutorial (Engine performance) and paste it into the working directory.

Results:

Here, we are going to perform a 1D simulation of a single-cylinder SI engine and we will take a look into engine performance. And also we will conduct the study on various parameters that will be responsible for increasing the power output.

1. Parameters at 1800 RPM of engine:

In this study, we only change here in engine speed to 1800 RPM and run the simulation.

Output parameters are as follows:

• Airflow Rate- 24.646053 Kg/Hr
• Fuel flow rate- 1.6998 Kg/Hr

Since we are here assuming that equivalence ratio has maintained to unity and the air-fuel ratio is fixed to 14.5:1.

• BMEP(Brake Mean Effective Pressure)- 9.476768 bar
• BSFC (Brake Specific Fuel Consumption)- 239.17131 g/Kw-Hr
• In-cylinder Pressure- 48.891994 bar

Brake torque and Brake power produced by an engine running at 1800 RPM are 37.704 N-m and 7.1070 KW respectively.
The maximum temperature produced inside the engine after combustion is 2552.1812 K.

2. Increase power output by 10% if the engine runs at 3600 RPM.

In this study, we will be changing engine speed to 3600 RPM and we will be changing for possible engine characteristics to increase power output by 10%.

A case before implementing changes:

The Brake Power output found at 3600 RPM of given SI engine as 16.697336 KW.

Now, we are going to change the parameters which will increase the power output by 10% (i.e. 18.359 KW).

To increase the power output we are going to employ various strategies like Engine geometry, Injection Control, and Cylinder parameters.

• Changing geometric parameters

CASE-1: In this first, we will choose Bore as 86mm and stroke length varying from 86mm to 96mm (under-square engine) with an interval of 2mm while keeping the rest of the parameters constant.

Variation of Brake power output is shown below:

As we can see in the above results we can say that by changing Stroke length power output increases. At Stroke length of 96mm and Bore 86mm, the power output we got is 18.474415 KW which is 10.64% of existing engine configuration.
At Brake power output of 18.474415 KW, the maximum pressure and maximum temperature inside the combustion chamber are found out to be 61.2542 bar and 2705.106 K.

CASE-2: In this case, we are going to change the Bore diameter from 86mm to 91mm (Over-square engine) and Stroke length as 86mm while keeping the rest of the parameters the same.

Variation of Brake power output is as below:

At Bore diameter 86mm and stroke length 91mm brake power output found out as 18.588701 KW which is 11.32% of the power generated using existing engine configuration.

From the above result, we can see that Using an Over-squared engine will be beneficial in terms of BSFC (Brake Specific Fuel Consumption). In the Under-squared engine, BSFC is 247.03 g/Kw-h to produce 18.4744 KW of power, and BSFC for the Over-squared engine is 246.426 g/Kw-h for producing 18.5887 KW of power.

• Cylinder Strategies (Combustion model):

CASE-1: By Lowering the anchor angle (the angle at which 50% of combustion completed).

The increasing rate of combustion up to a certain value will little increase the power output then reduces. We can see in the graph below.

This strategy doesn't contribute enough to increase more power.

CASE-2: By lowering combustion duration (the crank angle duration in which from 10% to 90% combustion completed ).

Power Output:

As we can in the graph, lowering the combustion duration won't affect much in increasing power output. Even if we lower combustion duration the rate power output increase will be lower.

For combustion duration of 11 crank angle, the maximum pressure and maximum temperature inside the combustion chamber are found out to be 68.2450 bar and 2777.687 K.
Since the values of pressure and temperature are so huge this situation will definitely lead to engine knocking.

• Injection Control:

CASE-1: Changing Air-fuel ratio (lean or rich air-fuel)

For Rich mixture-

The brake power variation will be-

From the graph, making 6.8% rich fuel we can see a little increase in power output. And making further air-fuel mixture rich lowers the power output and at the same time it drastically increases CO emission.

For Lean mixture-

Variation of power output-


Engine working on a lean mixture will not produce sufficient power we can see in the above graph. Brake power reduces as we increase the air quantity in the air-fuel mixture. But it lowers the CO emission since complete burning of fuel is possible due to excess air.

CASE-2: Changing the injection delivery rate.

Reducing Injection delivery rate:

Variation of Power output is below:


The increase in power output by reducing the injection delivery rate is very less up to 6 g/s and a further decrease in injection delivery rate power output decreased.

CONCLUSION:

In this way, we have studied 1D simulation of one cylinder SI engine and also conducted the study to increase the brake power output of engine running @ 3600 RPM by 10%.
Following are the conclusions we can draw from the study:

1. Engine geometry is the only way to increase brake power output by 10% i.e. 18.359 KW. But working on such high power output is detrimental for the SI engine because working on such high power output causes a drastic increase in combustion temperature which ultimately leads to ENGINE KNOCKING. This knocking phenomenon will cause severe engine damage during operation. This is the reason we always try to limit this phenomenon as this is very much sensitive to temperature.

2. Increasing the Compression ratio is also one of the ways to increase power output but a higher compression ratio causes the high temperature inside the combustion chamber. Hence practically most of SI engine limits to work between 8:1 to 13:1 compression ratio.

3. We have also conducted studied on other parameters like injection control and combustion parameters, but the output that we desired has not obtained. This parameters shows a little increase in power output