Week-4 : Basic Calibration of Single cylinder CI-Engine

Difference Between SI Engines and CI Engines:

SI Engine	CI Engine
It is based on OTTO cycle constant Volume heat addition and rejection Cycle	It is based on Diesel cycle or constant Pressure heat addition and constant volume rejection Cycle
A high Volatile, high self –ignition temperature fuel, gasoline is used.	Comparatively low Volatile and low self –ignition temperature fuel, Diesel is used.
A gaseous mixture of air and fuel is inducted during the suction stroke. A carburettor is necessary to provide the mixture.	Fuel, is injected at high pressure at the end of Compression Stroke. A fuel pump and injector unit is used.
Throttles control the quantity of fuel-air mixture introduced.	The quantity of fuel is regulated in pump. Air quantity is not controlled. There is quality Control.
For Combustion of the charge, it requires Ignition system with Spark plug in Combustion Chamber.	Auto Ignition occurs due to High Temperature of air resulting from high Compression ratio.
Compression ratio Ranges from 6 to 10	Compression ratio Ranges from 16 to 20
Due to light Weight and homogenous combustion, they are high speed engines.	Due to heavy Weight and heterogeneous combustion, they are Comparatively low speed engines.
It has lower Thermal Efficiency due to lower Compression Ratio but delivers more power for some compression ratio	It has higher Thermal Efficiency due to high Compression Ratio and delivers lesser power for some compression ratio
In SI engine physical delay is almost zero chemical delay Controls Combustion.	In CI engine chemical delay Controls Combustion
Delay period must be as long as possible. High Octane fuel(low Cetane) is required.	Delay period must be as Short as possible. High Cetane fuel(low Octane) is required.
Less Maintenance is Required	More Maintenance is Required
Noise Produced is less	Comparatively Produced High Noises.
Initial Cost is Less	Initial Cost is High.
Direct port- Tumble	Helical Port -Swirl
Operates at High Speed	Operates at Low Speed

Exploring the Tutorial of Single Cylinder Diesel Engine:

Layout of the 1-cylinder Diesel Injection Engine:

Engine Geometry Template:

Cylinder Template:

• This part represents the combustion chamber first comes the main tab

Injector Template:

Intake Valve Temperature:

Intake Valve Lift:

Intake Valve Flow Coefficients:

Run:

Engine Performance with 2 different types of Speed:

• From the above results we can clearly have observed that the Speed increases the output of power is also increases.
• The brake power is 26.2 Hp at a speed of 1800RPM and have shown tremendously increases to 48.6 Hp.
• The brake Specific Fuel Consumption is 221.3 g/kw-h at a speed of 1800 rpm and 238.2 g/kw-h at a speed of 3600.This clearly indicates the raise in the value.
• The air fuel ratio is also increased which is also shown in above image.

• Maximum inside Cylinder pressure is also increased from 104.34 bar to 117.11 bar.
• Emissions like HC,CO and CO2 in ppm are greatly reduced with the higher speed.
• The Exahust temperature is 1045 k with a speed of 1800 RPM and 1039K with a Speed of 3600 RPM

Plots:

Pressure Plot for Both Speeds 1800 and 3600:

PV Plot for Both Speeds 1800 and 3600:

Temperature Plot for Both Speeds 1800 and 3600:

 

Calibration of SI Engine done:

The block diagram of the SI Engine shows in the below Image:

The Geometry Dimensions of the Engine Cylinder:

The details of the combustion Chamber:

Run the case:

Engine Performance:

Cylinder Details:

Brake-specific fuel consumption (BSFC):

• 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 fuelconsumption divided by the power It may also be thought of as power-specific fuel consumption, for this reason. BSFC allows the fuel efficiency of different engines to be directly compared.
• BSFC numbers change a lot for different engine designs, and compression ratio and power rating. Engines of different classes like diesels and gasoline engines will have very different BSFC numbers, ranging from less than 200 g/(kW⋅h) (diesel at low speed and high torque) to more than 1,000 g/(kW⋅h) (turboprop at low power level).

Exhaust Temperature:

• The temperature of the exhaust gases at the outlet is called Exhaust Temperature.
• The exhaust gases of the petrol engines are hotter than the Diesel engine. As Diesel engine employs higher Compression ratio and the gas expands more it gets Cooler.
• The diesel engines also operates at higher Air fuel ratio as there are no throttling losses and hence lower exhaust temperature.

Air Fuel Ratio:

• Air–fuel ratio(AFR) is the mass ratio of air to a solid, liquid, or gaseous fuel present in a combustion The combustion may take place in a controlled manner such as in an internal combustion engine or industrial furnace, or may result in an explosion (e.g., a dust explosion, gas or vapour explosion or in a thermobaric weapon).
• The air-fuel ratio determines whether a mixture is combustible at all, how much energy is being released, and how much unwanted pollutants are produced in the reaction.Typically a range of fuel to air ratios exists, outside of which ignition will not occur. These are known as the lower and upper explosive limits.
• In an internal combustion engineor industrial furnace, the air-fuel ratio is an important measure for anti-pollution and performance-tuning reasons. If exactly enough air is provided to completely burn all of the fuel, the ratio is known as the stoichiometric mixture, often abbreviated to stoich. Ratios lower than stoichiometric are considered "rich." Rich mixtures are less efficient, but may produce more power and burn cooler. Ratios higher than stoichiometric are considered "lean." Lean mixtures are more efficient but may cause higher temperatures, which can lead to the formation of nitrogen oxides. Some engines are designed with features to allow lean-burn. For precise air-fuel ratio calculations, the oxygen content of combustion air should be specified because of different air density due to different altitude or intake air temperature, possible dilution by ambient water vapor, or enrichment by oxygen additions.

Comparison of both SI and CI Engines on the below parameters:

Brake-specific fuel consumption (BSFC):

• The brake Specific Fuel Consumption of the Si engine is high as compared to the CI Engine which means for any given cycle the CI engine less fuel is consumed.

• SI Engine BSFC                                                                                    CI Engine BSFC

     

Exhaust Temperature:

• Due to higher BSFC and complete combustion in SI Engine the exhaust gas temperature is very high in SI engines where as in Diesel Engine the temperature is very less due to low BSFC.
• SI Engine Exhaust temperature                                                                               CI Engine Exhaust Temperature

   

Air Fuel Ratio:

• Air fuel ration in CI engines is very high (lean mixture and lean burned) whereas the SI engines having lower air fuel ratio (rich burned).
• This is due to the reduction in the compression ratio in SI engines.
• SI Engine Air Fuel Ratio                                                                              CI Engine Air Fuel Ratio

  

Change MFB 50 and observe impact on performance:

• The mass fraction burned (MFB) shows how the incylinder combustion progresses as a function of the crank angle. The rate of combustion inside an engine cylinder is a very important parameter affecting the engine thermal efficiency, peak cycle temperature and pressure, and exhaust emissions. This combustion rate is usually quantified by calculation of the burn crank angles at which the MFB reaches a specified value
• Combustion Control has always been an important role in the Modern Internal Combustion Engine system and being more crucial nowadays to improve the driveability and reduce pollutant emissions. The position where 50% of fuel mass burned over an engine cycle is reached.

By changing the main duration as parameter performance impact is provided. Duration in crank angle degrees of the main diffusion burn or the name of the dependency reference object.

Case 1: Main Duration 35:

Case 2: Main Duration 40:

Case 3: Main Duration 45:

Case 4: Main Duration 50:

The block diagram of the CI Engine shows in the below Image:

Cylinder Template:

CaseSetUp:

• From the above images we can observe that the Brake power is reduced when we increased the Main duration of the moment of the piston and aslo the Torque Power is aslo reduced and increase in the BSFC when we increasing the main duration time.

• The CO2 emissions from the engine is incfeases when we increase the Main duration ,the CO emissions are up and downs when we changed the values of the main duration. 

Graphical Results:

• Graphical results of the MFB50 can be shown below with 35,40,45,50 crank angle with the Speed of 3600 RPM respectively as shown in below.

Pressure Plot:

• The crank angle 35 has the high inside cylinder pressure than the remaining cases.

Temperature Plot:

• The crank angle 35 has the high Exhaust Temperature than the remaining cases.

Burned Fuel Plot:

• The Crank angle 35 has the highest fuel burned rate than the remaining cases.

Conclusions:

• The CI engine is successfully designed with different speeds and observe the results of the different parameters.
• Done the Comparison of the different parameters like BSFC,Air fuel Ratio,Exhaust Temperature of the SI and CI engines.
• Change the main duration time and observe the performance of the engine.