Week-4 : Basic Calibration of Single cylinder CI-Engine
Aim:
- Basic Calibration of single cylinder CI-Engine.
Objectives:
1.Compare SI vs CI and list down differences (assignment no 2-SI)
2.Comments on following parameters
- BSFC
- Exhaust Temperature
- A/F ratios
3.Change MFB 50 and observe impact on performance
Pre-processing and solver:
1.Compare SI vs CI and list down differences (assignment no 2-SI)
| SI Engine | CI Engine | |
| 1. | SI engine is known as the Spark Ignition engine. | CI engine is known as the Combustion Ignition engine. |
| 2. | The fuel used here is Gasoline or Petrol. | In CI engine the fuel used is Diesel. |
| 3. | The compression ratio is 6 to 9. | The compression ratio is high around 15 to 20. |
| 4. | This is light in weight because of the low pressure developed here. | This is heavy in weight because of the high pressure developed here. |
| 5. | Low vibration and Noise here. | Here more vibration and noise. |
| 6. | SI engine works on the Otto cycle. | CI engine works on the Diesel cycle. |
| 7. | The speed is higher in the SI engine. | The speed is low in the CI engine. |
| 8. | Thermal efficiency is low or average. | Thermal efficiency is high. |
| 9. | Air and fuel are used during the intake process | but here only air is used during the intake process. |
| 10. | This is kind of cheaper in price. | This we get higher in price. |
| 11. | This is also called a constant volume cycle. | This is called a constant pressure cycle. |
| 12. | Petrol fuel has a high self-ignition temperature. | Diesel fuel has a self-ignition temperature but it’s low. |
| 13. | Knocking takes place at the end of the combustion. | Knocking takes place at the beginning of the combustion. |
| 14. | A homogeneous mixture of fuel. | A heterogeneous mixture of fuel. |
| 15. | Petrol fuel is used in aerospace and automobiles. | Diese fuel used in heavy vehicles such as lorries, buses, and trucks, more. |
| 16. | SI engine fitted with carburetor and spark plug. | CI engine fitted with injection or fuel injected pump. |
| 17. | Here ignition of air-fuel mixtures takes place by an electric spark produced by a spark plug. | But here air-fuel take place by injection of fuel into the hot compressed air. |
| 18. | Temperature range here 250 to 300-degree celsius. | In CI engine Temperature 600 to 700 degree celsius. |
| 19. | In the SI engine, Specific fuel consumption is more. | Here in the CI engine, the specific fuel consumption is less. |
Homogeneous Mixture:
- A homogeneous mixture can be defined as a mixture that has a uniform composition throughout its mass. For example sugar in water or salt in water. That is, when sugar or salt is mixed in water they dissolve completely in the solvent which is water in this case.
heterogeneous Mixture:
-
Definition of Heterogeneous Mixtures. In a heterogeneous mixture, the substances do not blend smoothly throughout, and the individual substances that compose the mixture can be detected. Heterogeneous mixtures can typically be separated back into their individual components through chemical or physical means.
Combustion in SI Engine:
- A spark-ignition engine is an internal combustion engine, generally a petrol engine, where the combustion process of the air-fuel mixture is ignited by a spark from a spark plug.
Combustion in CI Engine:
- CI engine is an internal combustion engine in which ignition of the fuel takes place with the help of hot compressed air. As the air is compressed, it gets hot and its heat is used for the ignition and burning of the fuel.
case setup:1
Plot setup
Results:
Pressure
P-V Diagram
Temperature
Burn Rate
Burned Fuel
NOx Concentration
Engine Performance
From the engine performance date we obtain
BFSC at MFB 40= 249.3 g/kw-hr
BFSC at MFB 50= 276.0 g/kw-hr
BFSC at MFB 60= 308.8 g/kw-hr
A/F Ratio at MFB 40= 20.78
A/F Ratio at MFB 50= 20.78
A/F Ratio at MFB 60= 20.79
BP at MFB 40= 33.6kw
BP at MFB 50= 30.3kw
BP at MFB 60= 27.1kw
Exhaust Temperature at MFB 40= 1063 K
Exhaust Temperature at MFB 50= 1111 K
Exhaust Temperature at MFB 40= 1153 K
From the engine performance it is seen that with increase in combustion duration, the BP of engine decreases and vice versa. The brake efficiency increaeses with combustion duration but for NOx ppm it is lower for more combustion duration.
Conclusion:
- The CI engine is successfully designed at differentcombustion duration and same injection period.
- The post simulation calibration is done to compare the impact on effciency and other parameters.