Emission characterization on a CAT3410 engine

Emission characterization on a CAT3410 engine

In order to reduce the emission from the IC Engines, one of the most important aspect to look at is the Piston bawl profile. In this Project we are comparing between Open_w and Omega bawl profile piston type to see which Piston is better in order to reduce emissions.

The CAT3410 engine is a heavy duty engine produced by the Caterpillar. This engine is generally used for the industrial applications. The geometry of the piston head plays a vital role in altering the compression ratio apart from the design of the cylinder head. High domed piston shave generally more compression  ratio compared to flat.

What is closed loop simulation?

In a closed loop simulation, the input is adjusted function of the output of the virtual system. This means that any disturbances affecting the virtual system will be compensated by the input. The operations engineer can compare operational data with simulated results to diagnose problems with the physical asset. The assumption is that the system model of the physical asset reflects the reality accurately. Such a finely calibrated model can be used to diagnose physical asset.

Example Scenario:

Model Calibration

The simulation engineer compares model simulation results with the operational data. This helps to fine tune the system model. The physical asset is used as a reference to calibrate the system model.

Virtual Sensor:

In certain cases, physical parameters cannot be measured. For example, torque on the shaft in operation cannot be measured while keeping it operational. In other cases, physical parameters could be difficult to measure because of inaccessible location to place the sensor. In such a scenario, the operations engineer can use a system model where the immeasurable parameters are modelled as output variables. The operational data is fed to the system model and the output variables act as virtual sensors providing value which could not be measured.

Diagnostics:

The operations engineer can compare operational data with simulated results to diagnose problems with the physical asset. The assumption is that the system model of the physical asset reflects the reality accurately. Such a finely calibrated model can be used to diagnose physical asset.

Performance Improvement:

Identify optimal inputs to the machine for better efficiency and maximum performance. The key parameters can be identified by comparing the results against various inputs.

 

Spray Modelling:

Spray model is a simplified mathematical model use to capture the spray process. The spray is made up of a multiple Parcels which is collection of drops.

Converge can model both gaseous and liquid sprays. Converge includes state-of-the-art models for spray processes including spray automization, drop breakup, collision and coalescence, turbulent dispersion, and drop evaporation.

 

Combustion Modelling:

A combustion facilitates energy transfer in an engine. It uses a detailed SAGE Chemistry solver.

The SAGE detailed chemistry solver uses local conditions to calculates the reaction rates based in the principle of chemical kinetics.

It couples(add) with the Transport solver via source terms in the species transport equations.

   

 

Adaptive Mesh Refinement(AMR):

It works on the principle of Curvature of properties (pressure, temperature), that is second order derivative. Examples: d^2T/dx^2 (for temperature). In AMR we define sub-grid value. If the Curvature of temperature or velocity is greater than the subgrid value, the AMR will be enabled by showing these change in temperature or velocity, which helps us to capture physics correctly at very fine cell size.

Calculation of reducing in base grid size due to Embedding:

Grid size after subgrid(smallest cell size after subgrid)=Base grid size/(2^Max embedding level)=4/(2^1)=4/2=2metre.

Grid size after subgrid(smallest cell size after subgrid)=Base grid size/(2^Max embedding level)=4/(2^2)=4/4=1metre.

Grid size after subgrid(smallest cell size after subgrid)=Base grid size/(2^Max embedding level)=4/(2^3)=4/8=0.5metre.

 

Four stroke engine:

- Cycle of operation completed in four strokes of the piston or two revolution of the piston.

(i) Suction stroke (suction valve open, exhaust valve closed)-charge consisting of fresh air mixed with the fuel is drawn into the cylinder due to the vacuum pressure created by the movement of the piston from TDC to BDC.

(ii) Compression stroke (both valves closed)-fresh charge is compressed into clearance volume by the return stroke of the piston and ignited by the spark for combustion. Hence pressure and temperature is increased due to the combustion of fuel

(iii) Expansion stroke (both valves closed)-high pressure of the burnt gases force the piston towards BDC and hence power is obtained at the crankshaft.

(iv) Exhaust stroke (exhaust valve open, suction valve closed)- burned gases expel out due to the movement of piston from BDC to TDC.

 

Geometry Setup:

In the Diesel Engine simulation, we are going to perform the close cycle analysis. We are creating the Engine Sector and simulating one portion of the sector.

Bore=0.13716m

Stroke=0.1651m

Connecting rod=0.263m

Cranck speed=1600rpm

Open_w sector :  

 

Omega sector:

Case Setup/Simulation Setup:

Click on IC engine. ->

 MATERIAL:

Gas Simulation:

• check Reaction Mechanism.
• Predifined mixture: air
• Enable species(not in mech.dat) as we want to assign the participating species of Air like O2 and N2
• Parcel Simulation: Predefined liquid DIESEL2

Gas Simulation:

• Import thermo.dat () contains thermodynamic properties of species)

Reaction mechanism:

• Import mech.dat(Types of species)

Global Transport Properties

• Terbulent Prandtl number: 0.9
• Terbulent Schmidt number: 0.78

Species:

• Add Parcel species DIESEL2
• Internal Passive: HIROY_SOOT and NOx

SIMULATION PARAMETER:

Run Parameter:

• Solver: Density-based Transient
• Simulation Mode: Full Hydro
• Gas flow Solver: Compressible (as air is working medium)

Simulation Time Parameter:

• End time: -147 degree
• Start time: 135 degree
• Initial time step: 5e-07 s
• Minimum time step: 1e-08 s
• Maximum time step: 1 s

BOUNDARY:

         By using the right amount of fuel the end products/species should be CO2, H20 and N2

1. Piston- 553K.

Boundary type-wall. Wall motion type-Translating. Surface movement- Moving. Triangle motion: Piston motion

2. Front_face-

Boundary type-Periodic. Periodic type-Translating. Exhaust valve bottom temeprature - 525K. Triangle motion: User specified. Periodic Shape angle: 45 degree. Matching Boundary: Back face

3. Back_face-

Boundary type-Periodic. Periodic type-Matched Boundary. Matching Boundary: Front face.

4. Back_face-

Boundary type-wall. Wall motion type-Stationary. Surface movement- FIXED.

 

REGION & INITIALIZATION:

• Click on Region and Initialization and add 1 Region.
• 

Physical Model

Spray Modelling

• General

Injector setup:

• To see Injection pressure and velocity, Injectors-> Tools->Spray rate preview-> Spray rate calculator->calculate rate-> Injection pressure

Fig

To see whether all the nozzle inside the computational domain, Tools-> validate nozzle location.

COMBUSTION MODELLING:

• 
• 
• General-> Fuel species name-C7H16.

 

Emission modelling:

 

Turbulence model:

• RNG k-epsilon

 

Base grid:

• dx=0.004m; dy=0.004m; dz=0.004m

Adaptive Mesh Refinement(AMR):

Velocity AMR

Temperature AMR:

 

Fixed Embedding:

Nozzle Embedding                                                                                               Piston Embedding

Cylinder Head Embedding:

 

Post-variable selection:

Output files:

Export input files and Running the Simulation:

Now we have successfully setup the Case and need to export the input files to run the Simulation.

Run the Simulation in Cygwin using parallel processor.

 

Post Converting:

Now we need to convert all the output files which are processed by converge msmpi into the files which will be readable for post-processing in Paraview

 

 Plots:

Pressure Plot:

The mean Peak Pressure in Omega piston bawl profile is more than the open_w piston.

Temperature Plot:

Due to high Peak Pressure of Omega piston , the temperature is also high, which means that there is a better combustion of fuel and unburnt fuel will be less. On the other hand, the open_W piston, has slight lower combustion temperature and the burning of fuel will be lesser.

Hear Release Rate(HRR):

The HRR of Omega piston is more due to high peak pressure and tempearure.

Integrated HRR:

The Integrated HRR of Omega piston is more than the Open_w piston.

NOx Formation:

Due to lowe temperature , the emission Nitrogen Oxide(NOx) formation of Open_w piston is lesser than the Omega piston as the temperature of combustion is highrer.

Soot formation:

The emission soot formation of Omega piston is lesser than the Open_W piston.

Unburnt Hidrocarbon(UHC):

Due to high Peak Pressure of Omega piston , the temperature is also high, which means that there is a better combustion of fuel and unburnt fuel will be less. On the other hand, the open_W piston, has slight lower combustion temperature and the burning of fuel will be lesser.

Carbon Monoxide(CO) emission:

Both Omega and Open_W piston has almost same amount of CO formation. BUt Omega piston has slight more CO emission.

CO2:

Mesh:

Omega_piston

Open_W Piston

Timing Map:

Power and Torque Calculation:

Omega piston:

Engine performance calculator:

The IMEP=197475 Pa

Indicated mean effective pressure is the average pressure produced in the combustion chamber during the operating cycle.

Power=Work/Time

Time(sec/degree)=60/(360*1600(rpm))=1.04e-4 s/degree

Time for 270.239 degree(per cycle)=1.04e-4*270.239=0.0281 s/cycle.

Work=482.012 Nm(from Engine performance calculator)

Power=4820.12/0.0281=17153 Watts.

Power=2*3.14*N*T/60.

Torque=102.37 Nm.

 

Open_w piston:

The IMEP = 524405 Pa

Power=Work/Time

Time(sec/degree)=60/(360*1600(rpm))=1.04e-4 s/degree

Time for 270.239 degree(per cycle)=1.04e-4*270.239=0.0281 s/cycle.

Work=411.867Nm(from Engine performance calculator)

Power=411.867/0.0281=14651 Watts.

Power=2*3.14*N*T/60.

Torque=87.43 Nm.

 

Animation:

NOx:

Open_w                                                                                                                    Omega piston:

CO:

CO2:

Conclusion:

• Power and Torque of Omega Piston is more than Open_w piston.
• Due to high Peak Pressure of Omega piston , the temperature is also high, which means that there is a better combustion of fuel and unburnt fuel will be less. On the other hand, the open_W piston, has slight lower combustion temperature and the burning of fuel will be lesser.
• The HRR of Omega piston is more due to high peak pressure and tempearure.
• The Integrated HRR of Omega piston is more than the Open_w piston.
• Due to lowe temperature , the emission Nitrogen Oxide(NOx) formation of Open_w piston is lesser than the Omega piston as the temperature of combustion is higher but The emission soot formation of Omega piston is lesser than the Open_W piston.
• The emission soot formation of Omega piston is lesser than the Open_W piston.
• Both Omega and Open_W piston has almost same amount of CO formation. BUt Omega piston has slight more CO emission.
• IMEP of Open_w piston is more than Omega piston.