Emission characterization on a CAT3410 engine

Aim: To perform close simulation of a CAT 3410 engine with different piston profile and obtain characterized emission and compare power and IMEP.

Introduction: The rise in a restriction on emission lead the manufacture to explore a new way to reduce the emission such as a change in cylinder profile, piston geometry, alternate fuel etc. The following are piston profile

• Open W cylinder :

• Omega cylinder:

The following are cylinder profile:

• Open W profile:

• Omega Profile:

The following are the detail of cylinder geometry:

• Bore: 0.13716 m
• Stroke: 0.1651 m
• Connecting Rode: 0.263m
• Compression ratio: 14.5
• Sector angle: 45

Case Setup:

Application:

• IC Engine
• Swirl ratio: 6.78e-1
• Swirl profile: 3.11
• Crank speed: 1600

Material:

• Gas simulation
• Parcel simulation
• Diesel2
• Reaction mechanism

• Global transport parameter
• Species
• Parcel (Diesel2)

Simulation Parameters

• Transient solver
• Start time: -147.0 deg.
• End time: 135.0 deg.
• Initial time step: 5e-7 s
• Minimum time step: 1e-8s
• Maximum time step: 2.5e-5 s

Boundary:

Name	Region	Type	Condition
Piston	Inclinder region	Wall	Moving Piston motion	Law of wall (553K)
Front face	Inclinder region	Periodic	Angle (45 deg.)
Back face	Inclinder region	periodic	Angle (45 deg.)
Cylinder wall	Inclinder region	wall	Stationary	Law of wall (433K)
Cylinder head	Inclinder region	wall	Stationary	Law of wall (523K)

Region and initialization:

Name	Temperature	Pressure	Species
Inclinder region	355k	197000 Pa	O2=0.23029, N2=0.76765, CO2=0.0014304, H2O=0.006296

Physical Models:

• Spray Modelling
• General
• Parcel distribution: Cluster parcels near cone center
• Evaporation model: Frossling model
• Wall Interaction
• Spray-wall interaction model: Rebound/slide
• Injectors
• Parcel species: Diesel 2
• Combustion Modelling
• SAGA
• Minimum cell temperature: 600K
• Minimum HC species mole fraction: 1e-8
• Temporal type: Sequential
• Start time: -10deg.
• End time: 135deg.
• Turbulence modelling
• Reynolds Averaged navier stokes (RANS)
• Turbulence model: RNG k-ε

Grid Control

• Base Gird
• dx= 0.0014
• dy=0.0014
• dz=0.0014
• Adaptive Mesh: 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.
• Minimum cells: 1
• Maximum cells: 200000
• Embedding level: 2
• Active region: Incylinder region
• Velocity
• Sub-grid criterion: 2
• Timing control type: permanent
• Temperature
• Sub-grid criterion: 5.0
• Timing control type: Sequential
• Star time: -12 deg.
• End time: 180 deg.
• Fixed Embedding
• Embedding 1
• Entity type: Nozzle
• Mode: Sequential
• Scale: 2
• Start time: -12 deg.
• End time: 15 deg.
• Radius 1: 0.001 m
• Radius 2: 0.003 m
• Length: 0.01 m
• Embedding 2
• Entity type: Boundary
• Boundary ID: Piston
• Mode: Sequential
• Scale: 1
• Embed Layers: 1
• Start time: -20 deg.
• End time: 180 deg.
• Embedding 3
• Entity type: Boundary
• Boundary ID: Cylinder head
• Mode: Sequential
• Scale: 1
• Embed Layers: 1
• Start time: -20 deg.
• End time: 180 deg.

Output file:

• Time interval to write 3D output files- 2 deg.
• Time interval to write text output files- 0.1 deg.
• Time interval to write restarting output – 5 deg.

Timing map:

Post-processing:

• Mesh: The base grid of 1.4 mm is provided. Addition with that AMR and fixed embedding is also provided.

• Emission:
• Soot:

The above plot shows the formation of soot in Open W piston and Omega piston. In case of Open w piston the formation of soot higher in comparison to the Omega because TKE (turbulent kinetic energy) is lower in case of Open W piston. As the TKE increase, reduces the formation of soot.

• NOx=

The above plot shows the formation of NOx in open w and omega type piston. The formation of NOx in case of Omega is much higher than the Open W. The formation of the NOx depends upon the maximum temperature obtained in the combustion chamber.

• CO:

The above plot shows the formation of CO in open w and Omega piston. The formation of CO in both cases is nearly the same.

From the above graph, we can say that the complete atomization of fuel takes place in case of omega which leads to the formation of the homogenous mixture. SO complete combustion takes place in case of omega. As the incomplete combustion takes place in case of Open w type which leads to more formation of CO in emission.

• HC:

The above graph shows the formation of HC in a different type of piston. Due to insufficient temperature in the combustion chamber, a higher amount of HC is formed in case of Open w in compare to the omega.

• CO2:

The above plot shows the formation of CO in a different type of piston. The higher amount of CO2 is preferred because higher amount shows the complete combustion of fuel take place. So from plot, we can say that a higher amount of fuel gets completely combust in case of omega in compare to the open w type piston.

Engine Emission Comparison

Emission	Open W	Omega	Comparison
Soot (Kg)	2.20E-06	0.000002197	The formation of soot in 0.13% higher in open W piston in comparison to omega
NOx (Kg)	0.0000033	0.0000055	The formation of NOx in 40% lower in Open W piston in comparison to omega
HC (Kg)	0.0000779	0.0000657	The formation of HC in 18.5% higher in Open W piston in comparison to omega
CO2 (Kg)	0.000055	0.000066	The formation of CO2 in 16.6% lower in Open W piston in comparison to omega
CO (Kg)	0.000234	0.000237	The formation of CO in 1.2% higher in Open W piston in comparison to omega

• Mean Temperature:

The omega Piston produces more amount heat in comparison to the Open W. As the TKE higher lead to higher combustion. The higher temperature is because of the higher heat produced in the combustion.

• Engine Performance:

	Open W	Omega
Cycle	1	1
Start (deg.)	-135.153	-135.153
End (deg.)	135.021	135.015
Duration (S)	270.174	270.168
Work (Nm)	3542.89	4064.76
IMEP (pa)	1.45E+06	1.67E+06
crank angle at which 10% fuel is consumed (deg.)	0.110623	0.110623
crank angle at which 50% fuel is consumed (deg.)	14.1019	13.8144
crank angle at which 90% fuel is consumed (deg.)	60.5157	48.0166
Peak firing pressure (Pa)	12.619	11.2404
Crank angle at peak firing pressure (deg.)	7.80128	13.1186
Heat Release Rate (j/deg.)	292.932	479.308
Crank Angle at peak heat release rate (deg.)	-3.79179	-2.39364

Power

• Open w

Work= 3542.89 (Nm)

RPM= 1600

Time per duration= 60 X 270.174 / 360 X 1600 = 0.028143125 s

Power = Work/time =3542.89/0.028143125 = 125.88 KNm/s

• Omega

Work= 4064.76 (Nm)

RPM= 1600

Time per duration= 60 X 270.168/ 360 X 1600 = 0.0281425 s

Power = Work/time = 4064.76/0.0281425 = 144.43 KNm/s

Torque

• Open w

Torque= 60 X power/ 2 X pi X N= 60 X 125.88 / 2 X 3.14 X 1600 =750 Nm

• Omega

Torque= 60 X power/ 2 X pi X N= 60 X 144.43 / 2 X 3.14 X 1600 =861.65 Nm

Combustion Efficiency

The below plot show the comparison of integrated heat release between Open w and Omega type piston.

As we can say that the integrated heat release in omega type piston higher than the open W.

• Integrated heat release rate for omega type piston= 9656 J
• Integrated heat release rate for Open W type piston= 8455 J
• Calorific value for C7H16 =48.06 MJ/kg
• Amount of fuel injected per cycle=2.70167e-05 Kg
• Total heat content of fuel = Amount of fuel X Calorific value X no. of injector = 2.70167e-5 X 48.06e+6 X 8 = 10387.38082 J
• Combustion efficiency for omega type piston= total heat release / total heat content of fuel = 965610387.38082=92.95%">965610387.38082=92.95%965610387.38082=92.95%
• Combustion efficiency for Open W type piston= total heat release / total heat content of fuel =845510387.38082=81.39%">845510387.38082=81.39%845510387.38082=81.39%
• Difference between integrated heat release= 1201 J
• Difference in amount of fuel burn= Diffence in HR / calorific Value = 120148.06=0.0249g">120148.06=0.0249g120148.06=0.0249g

The amount of fuel burn by omega type piston is 0.0249 g more than the open W piston.

Conclusion:

In case of open W piston profile the formation of HC, Soot, CO is higher in comparison to the Omega. But, the emission of NOx is higher in Omega type.

As from engine performance, we can see that omega produces more power and torque in comparison to the open W. It can be verified by PV curved. As the area under the PV curve is work done. The below plot show varies of PV curve for Omega and Open W profile.

In general the decision on the profile is made on the bases of many factors. If the decision is based on the emission of the engine than the Open W is prefer because controlling the emission of NOx is difficult and costly. While the performance of the engine is considered than Omega type piston is prefer