Week 11: Project 2 - Emission characterization on a CAT3410 engine

Aim: To Perform Emission Characterization on a CAT3410 Engine.

Objective:

To run a 3D Simulation of a CAT3410 Diesel Engine using two different piston bowl profiles and to understand the effect of Piston Bowl geometry on the Performance ans Emission characteristics of the Engine.

Geometry:

A tool called Make Engine Sector surface is used to create the engine the engine sector model and to perform the closed cycle analysis. The reason behind generating engine sector is that the geometry is symmetric about its axis and by using periodic Boundary condition at the forward and backward face , The Entire Combustion chamber can be simulated using a sector , there by saving lot of computational resources.

For Diesel Engine , the fuel injector is mounted exactly at the center of cylinder head and it will have multiple nozzle, In this case the spray will be symmetrical , hence to increase the computational efficiency , one sector of the engine is taken and combustion is simulated with it. It will lead to faster run times, This is called sector modelling and it is carried out as shown below.

Open W-type Piston:

Omega Type Piston:

Different  Bowl profile open -W type omega type

The geometry available with us has six nozzles with engine specifications;

Bore-0.13716 m

Stroke-0.1651 m

Connecting rod-0.263 m

Speed- 1600 Rpm

Compression ratio-17.5:1

Sector angle- 60 degrees ( No of nozzles=6, sector angle=360/6 =60 degrees)

Each injector with one nozzle 

Note; Due to system compatability here we set to 30 degree.

Setup:

Converge studio provides  us a separate application for IC Engine flow. 

Materials:

Gas Simulation:

Gas Simulation  and Reaction Mechanism are selected and thermodynamics Properties are imported for the equation to be solved.

Parcel simulation:

Reaction Mechanism:

Species:

Parcels  are used to simulate a special type of liquid that is used in conjunction with spray modelling, setting up a parcel simulation is identical to setting up a liquid simulation.

Diesel  species is selected under parcel simulation as this has  very close properties to diesel.

Simulation Parameters:

Run Parameters:

Simulation Time Parameters:

Transient Equation are selected and Full - Hydro case set is to run  , Running a non - Hydro simulation ignores transport equation ,spray and combustion thus are generally reducing Computational time.

We have Previously run this and analyzed for mesh simulation earlier.

Boundary Conditions:

Boundaries:

Piston:

Front and Back Face:

Cylinder Wall:

Cylinder region:

Regions and Initialization:

Here we create region ID to assign the parameters like temp, Pressure to each regions, and initialize species , passive and turbulence in each region , By Doing that we can highlight and isolate all boundaries associated to a region.

Region 0:

In cylinder Region

Temperature=355 k

Pressure =197000 pa

Species:

O2 = 0.23029
N2 = 0.76765
CO2 = 0.0014304
H2O = 0.0006296      

Spray Modelling:

The Kelvin- Helmholtz model and Rayleigh- Taylor model are used for spray Modelling . An injector with a nozzle is used to spray the fuel.

Converge offers injector mechanism that consists of n number of nozzles each with different size, orientation, cone angle, etc..

Parcel Species : DIESEL2

Start of Injection: -9.0 deg

Injection Duration: 21.0 deg

Total Injection Mass : 2.70167e-05 Kg

Fuel Temperature: 341.0 K

Injectors with one nozzle as12 nozzle are divided  into 12 parts I.e 30 Degree sector angle rate shape profile.

Combustion Modelling:

The sage detailed chemical kinetics solver is used for the combustion modelling.

Converge uses the multi-zone model which accelerate the chemistry calculations by grouping together similar computational cells and then invoking the chemistry  solver once per group than once per cell.

On the other hand generally less computational expensive and less productive . This may be used if we want to use global parameters correctly or just find out the maximum combustion temperature.

Start time: -10 deg

End time : 135 deg

Turbulence Model: RNG K-ε

Geometry Mesh:

Mesh Size-4 mm in dx=dy=dz directions.

Along with Mesh embedding velocity and temp adaptive mesh Refinement was also enabled.

Adaptive Mesh Refinement:

Velocity:

Temperature:

It eliminates the need to mesh the whole model finely, Adaptive Mesh Refinement Provides such a dynamic programming Environment for adopting the precision of the numerical computation based on the requirements of a computation Problem in specific areas which need precision while leaving the other regions at lower levels of precision and resolution.

Fixed Embedding:

Nozzle:

Piston:

Cylinder_head:

Fixed Embedding is used to refine the mesh for a particular component to refine a finite mesh.

Sequential embedding of factor 1 was defined at the piston and cylinder head boundaries, between the crank angle,  -20 deg to 180 deg when the combustion is said  to occur.

In addition to this , a nozzle embedding of factor 2 was provided at the injector to capture the fuel sprays.

Output Files:

Plots:

The variation of Pressure, mean temp, heat released rate , integrated heat release for both the piston Profiles were plotted and Analyzed.Pressure Plot:

From the plot ,We can see that peak pressure for omega Piston 9.47854 mpa is a bit higher than the peak pressure ofopen W Piston type 9.522 mpa. The difference being about 0.04346 mpa Which is due to difference in combustion chamber. Geometries, / shape of piston as Pressure is inversely Proportional to area . or In case of pressure comparison both Piston types, has the same amount of credits.

Mean Temp plot:

Omega piston tend to produce higher mean temp, due to better mixing of air -fuel mixture inside the combustion chamber leading to higher heat release rates. Whereas in this case of open W piston, due to the effect of liquid spray infringement, the combustion process is delayed leading to lower performance ratings.

The Peak temp of Omega Piston is 2128 K, and W-type Piston is 1831 k.

Integrated Heat release plot:

From the integrated heat release plot , it can be noticed that for the same amount of fuel injected , the energy outputs have some deviations about 72 J for both the piston types, hence there are discrepancy in the total heat released due to combustion differences.    

Between the two pistons bowl for the same quantity of fuel injected . The reason being that the fuel which has been impinged upon the open W piston does not get vaporized  in time for combustion to occur even though all the fuel vaporize due to high cylinder temperature.

Heat Release rate Plot:

From the plot , we notice that one can infer that release rate for omega Piston type is more than that of Open W piston type. This is due to mixing of air fuel  mixture  inside the Combustion Chamber leading to higher heat release rates. The Plot is smoother for omega type than Open W type and  it indicates that there waves forming leading to knocking / detonation  Phenomenon.

And by seeing the plot we notice that the omega type piston takes heat release exact to zero crank angle and where the w-type piston is taking after the crank angle zeroin between 2 to 5 degree.

Emission Plots:

Where the molecules are burnt and realsed with a amount of oxides like Co2, Co, NoX, soot, HC molecules etc..,

This consists of small non Equilibrium molecules formed when  large fuel molecules break up I.e thermal cracking during combustion reaction

Fuel In :

From the above plot where we can see Omega type piston have consumed volume of fuel in less iteratation , and w-type piston have taken in more iteratation.

And By this process in w-type piston some amount of fuel got vapourised and might not be burned  and get emission gas increase.

I n general CI engines has combustion efficiency  of 98%

This means only 2% of HC fuel being emitted . This may be due to wall deposit absorption , crevice volume     

Hydro Carbon:

Due to low fuel is burnt which creates more HC in w-type piston when compared to Omega Piston.

 Carbon Monoxide:

Carbon Monoxide is a colorless and odorless , but it is a poisonous gas generated when the operated with fuel-rich equivalence ratio , when there is not enough oxygen to convert all carbon to CO2 , Some carbon ends up with CO.

Oxides of Nitrogen:

Diesel engine operate at a higher temp, and pressure than petrol engines, These condition favors for NoX gases . The quantity depends on the volume and duration of the hottest  part of the flame, NoX is created mostly from nitrogen to air.

Especially at high temperature , Most of these will be NO and NO2and Produce due to energy limitation, Oxygen and Nitrogen do  not react at ambient temperature. But at high temp ,They undergo to endothermic reaction produces various oxides of nitrogen.

As NoX are produced during the combustion process when nitrogen and oxygen are present at elevated temp, Open W tend to produce lesser NoX Emissions  compared to omega Piston due to  the fact in lower cylinder temp are maintained in open - W compared to omega Piston.

Soot  Emission:

Internal Combustion engines Produce soot as a result of incomplete fuel combustion , ideally , complete combustion in a cylinder would only Produce carbon dioxide  and water ,

But In reality No engine is complete Efficient , Because of the way the fuel injection and ignited soot formation occurs commonly in diesel than in gasoline engines.

Unlike gasoline engines where the fuel -air mixture is ignited by a spark , fuel and air entering the diesel engine ignite spontaneously due to high pressure in the combustion chamber.

The fuel and air mixture in diesel engines typically do not mix as through as they do in gasoline engines, This creates fuel- dense pockets that produce soot when ignited, while the majority of soot easily escapes through the exhaust , some gets past the piston rings and ends up in the oil.

where in Omega piston we can see higher soot Due to high temp of  gases and less in W-type Piston where all the fuel are getting in some other molecules.

Carbon dioxide:

Carbon dioxide is a green house gas which should be considered for its reduction in emission .CO2 is a result of complete combustion.

 Performance Calculation:

1.Open-W type Piston:

1. i) Power (P) :

Power (P) = Work done / Time taken

Work done = 483.04 N-m (From engine performance calculator)

Time per degree = 60 / (360*1600)

Hence time for 270.539 degrees = (270.539*60) / (360*1600) = 0.02819 sec/deg

Power (P) = 483.04/ 0.02819

Power (P) = 17,135.00 W

2.
ii) IMEP :

IMEP = 198090Pa (or) 1.98 Bar.

Work done also calculated under the area of P-V graph.

 

Performance Calculation:

2.Omega type Piston:

1. i) Power (P) :

Power (P) = Work done / Time taken

Work done = 549.375 N-m (From engine performance calculator)

Time per degree = 60 / (360*1600)

Hence time for 270.254 degrees = (270.254 * 60) / (360*1600) = 0.028151 sec/deg

Power (P) = 549.375/ 0.028151

Power (P) = 19,515.00 W

2.
ii) IMEP :

IMEP = 225073 Pa (or) 2.25 Bar 

Work done also calculated under the area of P-V graph.

 

Hence we seen that  Omega Piston is 8.78% more efficiency than Open-W type Piston

IMEP CHART:

The IMEP bar chart are seen with respect to values of Open- W type Piston is less compard to omega type Piston ,which indicates high Pressure in Omega Type piston .And shows that more effciency

POWER CHART:

The POWER chart are seen with respect to values of Open- W type Piston is less compard to omega type Piston ,which indicates high Power in Omega Type piston .And shows that more effciency

Animation Result:

NoX:

https://drive.google.com/file/d/1XrKSP9-VUzv_-4x13EwLB_Nj-I64fbf6/view?usp=sharing

Soot:

https://drive.google.com/file/d/1KWvRCsxEFVgOOGETxJpmMQriID8gLjkJ/view?usp=sharing

UHC:

https://drive.google.com/file/d/1Aw0XAOLdra4wwEi4NYtRxoQwXI0EFGvT/view?usp=sharing

Conclusion :

The simulation of sector is done I.e Open -W type Piston and Omega Type of CAT3410 diesel engine and their  Parameters plots and Performance Parameters are Compared.

The omega Type Piston outperforms Open W- type in mainly critical factors and is 8.78% more efficient than the latter with lesser concentrations of Hiroy soot , UHC, CO were generated in the former one.

The NOx concentration was higher in the Omega piston due to the higher cylinder temperatures. NOx emission can be reduced by primary methods such as retard injection, fuel nozzle modification, change of compression ratio, water direct injection, water emulsification, exhaust gas recirculation (EGR) and secondary method such as selective catalytic reduction (SCR).