Project 2 - Emission characterization on a CAT3410 engine

Aim:

• To generate the sector geometry of the combustion chamber of the CAT 3410 engine for the Open w piston and Omega piston.
• To simulate the both profiles of omega piston and open w piston with the same parameters
• To study the emissions for the both configurations and study the conclusions

Introduction:

• The CAT 3410 is an industrial engine which is manufactured by the CATERPILLAR Company. It operated with the diesel as a fuel. In diesel engines the fuel is get into the combustion chamber through the injectors. The fuel is subjected to break and atomized before being mix the air mixture and thus allow the combustion takes place in the combustion chamber. A diesel engine with the different piston head will affect the combustion process and also the engine performance.

Procedure:

• Import the geometry into the converge. The image below shows the entire combustion chamber with the 360 degrees. If we run the entire simulation it consumes a lot of the computational time and also acquires a lot of memory. So in order to save the time and memory we need to sector the geometry by using Make engine surface sector.

• First we extract the profile from the surface.dat. This generated the four profiles bowl profile, Forward profile, Reverse profile and the head profile of the combustion chamber.
• Entering the values of the bore, Stroke, Connecting rod, Compression ratio and the sector angle.
• Now we can use the bowl profile option to export the bowl surface file which resembles the piston profile and make click the geometry surface.so now we can generate the two piston profiles which contains all the boundary flagging and boundary conditions and other parameters which are requires for the simulation
• The below image shows the generation of the piston profile and the generated the Open W Piston profile

• The below image Shows the generation of the piston profile and the generated Omega W Piston Profile.

Case Setup:

• Application Type: Crank angle based IC engine

• Go to materials and Enable the Gas simulation, parcel simulation and the Reaction mechanism
• Make the defaults valves in the gas simulation and in the parcel simulation add the liquid parcel as a Diesel2 and click ok

• Global transport parameters keep the default values as Turbulent prandtl number=0.9, Turbulent Schmidt Number=0.78.
• Reaction mechanism add the file of mech.in and then we get all the species that are required for the simulation.

• In the Species add in the parcel simulation as Diesel2 and also the Internal passive HIROY_Soot and NOX and the Schmidt number for all is 0.7800 and the solve option is IN_PISO

Simulation Parameters:

• In run Parameters the solver we used is Transient and type as Crank angle based engine simulation and then remaining should be default values.
• In simulation time Parameters the start time = -147 degrees, end time=135 degrees, initial time step=5e-07 sec, minimum time step=1e-08 sec, maximum time step=2.5e-05 sec and collision grid time step multiple 1e+28 and put the remaining values default.
• In solver parameters the solver should be Density based solver

Boundary Conditions for the geometry:

Regions and initialization:

Physical models:

• In the physical models enable the Spray Modeling, Combustion Modeling, Emission Modeling and Turbulence Modeling

Spray Modeling:

Accurate spray and turbulence modelling is critical for predictive diesel and gasoline combustion simulations. In order to obtain results that are the realistic as possible, converge contains a wide variety of spray and turbulence modeling options. Converge includes both Reynolds-Averaged Navier Stokes (RANS) and large Eddy Simulation(LES)turbulence models. For spray, converge contains a host of options to simulate injection, breakup, vaporization and other spray related processes. All of the spray and turbulence models in Converge are well validated and powerful.

The liquid and vapor penetration lengths (LPL and VPL) are two of the properties that characterize a spray. CONVERGE calculates both quantities for each nozzle at each timestep.
To measure the LPL, CONVERGE first calculates the total mass of the liquid parcels from the nozzle and then multiplies this mass by the liquid penetration fraction to yield the
penetrated spray mass. Starting from the center of the nozzle hole, CONVERGE sums the mass of the liquid parcels until it reaches the penetrated spray mass. This distance is the
LPL. CONVERGE reports the LPL for penetration fractions of 0.90, 0.95, 0.97, and 0.99 in spray_ecn.out. Additionally, you specify a liquid penetration fraction, penet_frac, in spray.in.
CONVERGE writes the corresponding LPL to spray.out.
Figure shows a schematic of the LPL with penet_frac set to 0.98.

To measure the VPL, CONVERGE requires two parameters in spray.in: the vapor penetration fraction, vapor_penet_frac, and the penetration bin size, penet_bin_size. For
each cell inside the spray cone, if the mass fraction of fuel vapor in the cell exceeds the vapor_penet_frac and if the cell size does not exceed the penet_bin_size, CONVERGE
calculates the distance from the center of the nozzle hole to the center of the cell. The largest of these distances is the VPL, which CONVERGE writes to spray_ecn.out. We
recommend a penet_bin_size of at least twice the size of the cells in the spray cone.

Combustion Modeling:

CONVERGE’s SAGE detailed chemistry solver uses local conditions to calculate reaction rates based on the principles of chemical kinetics. This solver is fully coupled to the flow solver, but the chemistry and flow solvers parallelize independently of one another, which speeds up the simulation. With the appropriate mechanism, the SAGE solver can predict a wide range of cases (e.g., a variety of fuels [premixed, non-premixed, partially premixed, multiple fuels], emissions modeling, and unique phenomena such as end-gas auto-ignition). With its accuracy and robustness, Converge can perform predictive modeling instead of merely confirming experimental results.

• In combustion modeling the general the fuel species name=C7H16 and under relaxation for steady state combustion is =0.25
• Temporal type=Sequential
• Cyclic period=0 degrees
• Start time=-10.0 degrees
• End time=135.0 degrees
• Region =Not region independent
• Combustion temperature cut off =600
• Minimum HC species mole fraction=1e-08

Emissions Modeling:

• Enable the thermal NOX model and then select the Equilibrium Assumption and the mass scaling factor converting the NO to NOX is 1.533
• In the Hiroyasu-NSC soot model and enable the Hiroyasu_NSC soot model
• Soot pre exponential formation rate factor =350
• Soot activation energy in the formation rate=12500.0
• Soot particle diameter=2.5e-06
• Soot oxidation rate factor=1.0
• Soot density=2
• In the species section enable the use total hydrocarbons for formation Species.
• In the phenomenological soot model and the Detailed Soot models none is selected

Turbulence Modeling:

Grid Control:

• The base grid mesh we used in the simulations as dx=dy=dz=0.004 m

Adaptive mesh refinement (AMR):

• In numerical analysis, adaptive mesh refinement(AMR) is a method of adapting the accuracy of a solution within certain sensitive or turbulent regions of simulation, dynamically and during the time the solution is being calculated. When solutions are calculated numerically, they are often limited to pre-determined quantified grids as in the Cartesian plane which constitute the computational grid, or 'mesh'. Many problems in numerical analysis, however, do not require a uniform precision in the numerical grids used for graph plotting or computational simulation, and would be better suited if specific areas of graphs which needed precision could be refined in quantification only in the regions requiring the added precision. Adaptive mesh refinement provides such a dynamic programming environment for adapting the precision of the numerical computation based on the requirements of a computation problem in specific areas of multi-dimensional graphs which need precision while leaving the other regions of the multi-dimensional graphs at lower levels of precision and resolution.
• In our simulation we used the velocity and temperature based sub grid criterion of two embedding level and the sub grid criterion as 2 and 5 in In_cylinder_region. So Converge checks the temperature and velocity property provided in the AMR and refines the mesh of the both property between the consecutive grid is more than the defined SGS valve.
• For velocity the Timing control type=Permanent and the for the temperature it is Sequential the start and end for this are -12.0 degrees and 180 degrees and the cyclic period=720 degrees.
• The formula used by the AMR to refine the mesh

Fixed embedding:

• Embedding is provided to refine the grid mesh size at the specified locations to improve the accuracy of the solutions.
• Use fixed embedding to refine the grid at specific locations in the domain where a finer resolution is critical to the accuracy of the solution. Fixed embedding allows the rest of the grid to remain coarse to minimize simulation time
• The piston and cylinder head have small elements because near the TDC Position the combustion process takes place. For the nozzle when simulating sprays, you can add an area of fixed embedding by the nozzle to resolve the complex flow behaviour

Nozzle Embedding:

The entity type used in this is nozzle and the mode is sequential with the scale of 2 and the start time and end time should be -12 degrees and 1 degrees and the injector id should be Injector_0 and the Nozzle ID should be Nozzle_0@Injector_0 and the radius 1 be 0.001 and the radius 2 should be 0.003 and length should be the 0.01

Output and Post Processing:

• Time interval for writing 3d output data files=2 degree
• Time interval for writing text output =0.1 degrees
• Time interval for writing restarting output =5 degrees
• Maximum wall clock time between restarting files=1 hour
• Maximum number of restart files saved=5

Results:

Mesh animation:

Total cell count for both the pistons:

Pressure plot:

• The pressure plot shows the omega piston had faster and higher rise in the pressure than the open w piston.
• This was because of the faster burning of fuel after it is injected into the combustion chamber.

Pressure animation:

Temperature plot:

Temperature animation:

• The temperature in the omega piston produces more heat than the open w piston because of the better combustion of air and fuel in the combustion chamber.
• The temperature profiles of the combustion chamber show that when the piston moves towards the TDC the air in the combustion chamber gets compressed and this cause the temperature to raise slowly.
• When the fuel spray particles are sprayed into the combustion chamber at the high temperature and high pressure results in the burning of the mixture and thus we observed the high temperature in the chamber before the volume starts increasingly.

Volume Plot:

Velocity Animation:

Density Plot:

Gamma Plot:

Integrated Heat release plot:

Heat Release plot:

• The heat released from the combustion chamber can be seen from the plots above.The faster burning in the case of Omega is the reason of the higher heat release rate.The Integrated heat plot shows the total heat released till an instant.
• The curve of the omega piston is higher than the open w piston.

Hiroy Soot Emissions:

Hiroy Soot Emissions Animation:

• The major pollutant emitted in the combustion of diesel and air in the internal combustion chamber. It is black in color which is mainly consists of carbon produced by the unburnt of the fuel.
• The soot emissions are more in the open w piston rather than the Omega piston

NOX Emissions:

NOX Emissions Animations:

• It is produced during the mixing of nitrogen and Oxygen gases during the combustion process.
• The NoX emissions are higher in the Omega piston rather than the Open w piston

HC Emissions:

• These emissions are produced due to the hydro carbons present in the combustion of the fuel.
• The HC emissions are higher than open W piston than the omega piston

CO Emissions:

• The CO emissions produced in both pistons are shown in above figure.The emissions for the open W piston are higher than the omega piston and clearly we observed that the emissions are dropped immediately after the raise.

CO2 Emissions:

PV Diagram Plots fro both the pistons:

• The area under the PV diagram of an engine indicates the work done by the engine. By comparing the above PV Diagrams of the both pistons configuration, the area under the Omega piston PV diagram curve is indicating the higher work done which we can observe in the Engine performance calculator.

Compare the imep and power values

Open W piston:

• Power is defined as the ratio of doing work done per unit time.

Power= work done/time

Power(P)=2πNT/60

Open w Piston:

• Work done=478.471
• Rotations per minute =1600
• Rotations per second=26.667
• Degrees per second=9600.12
• Hence time per degree =1/degree per second

Hence time moving for the degrees is =1/9600.12=0.00010417

=1.0417 x 10e-4 sec/degrees

Hence time for the 270.285 degrees =270.285 x 1.0417 x 10e-4

=0.028154

The power is calculated by power=work done/time

From the engine performance Calculator we get the work done as 478.41

Hence power is =478.471/0.028154

=16994.778=16.994 KW

Torque for the Open W piston engine is p=2πNT/60

T=(60 * P)/2πN=(60 X 16994.778 )/(2π X 1600)

=101.43 N-m

Omega Piston:

• Work done=548.293
• Rotations per minute =1600
• Rotations per second=26.667
• Degrees per second=9600.12
• Hence time per degree =1/degree per second

Hence time moving for the degrees is =1/9600.12=0.00010417

=1.0417 x 10e-4 sec/degrees

Hence time for the 270.279 degrees =270.279 x 1.0417

=0.028154

The power is calculated by power=work done/time

From the engine performance Calculator we get the work done as 548.293

Hence power is =548.293/0.028154

=19474.78155=19.47 KW

Torque for the Open W piston engine is p=2πNT/60

T=(60 * P)/2πN=(60 X 19474.78155 )/(2π X 1600)

=116.23 N-m

Engine performance:

• The performance parameters for both the piston configuration are calculated by using the engine performance calculator.

• From the above table we can observe that the work done by the omega piston is higher and also the IMEP is also higher in the case of omega piston than the Open w piston.
• We can see the crank angel at 90 degrees for the fuel combusts at an angle of 55.1066 in Open w piston and 44.2039 in Omega Piston. This indicates the combustion takes place more fast in the Omega piston.

Conclusion:

• The simulations are carried out for both the pistons in the CAT 3410 engine.
• The work, Power and Torque produced by the Omega piston configuration is higher than the Open W piston. The IMEP of the Omega piston is higher than the Open W piston so in terms of all we consider that the Omega piston is performed well
• The emissions produced by the both pistons are characterized, and it can be concluded that the Soot, NOX, HC produced in the Open w piston are higher.