Simulation of PFI (Port fuel injection) engine using Converge

Aim: To set up and perform Fullhydro simulation of PFI (Port fuel injection) engine using Converge.

Objective:

1. Set up full hydro simulation using Converge Studio.
2. Obtain the compression ratio of the given engine.
3. Calculate the combustion efficiency of the engine.
4. Use the engine performance calculator, to determine the power and torque for this engine.

PFI engine

In PFI engines the fuel is sprayed into the intake ports to mix with incoming air. The fuel injectors in PFI configurations are typically mounted in the intake manifold and the air/fuel mixture is pulled into the cylinder head as the intake valve opens.

Geometry

Import the STL file in converge studio and perform surface preparation. After removing all the surface errors, flag the boundaries.

Case setup

Application type: Crank angle based

Engine parameters

Material

'mech.dat' file is imported to the reaction mechanism. Gas thermodynamic data is given as a 'therm.dat' file. For the parcel simulation, parcel liquid and species are defined as the fuel. In this case IC8H18.

Simulation parameters

Solver: Transient

Simulation mode: Full hydrodynamic

Gas flow solver: Compressible

Liquid flow solver: Incompressible

Navier Stokes solver scheme: PISO

Simulation time parameters

Regions and initial conditions

Region	Pressure(Pa)	Temperature(K)	Species
Cylinder region	101325	300	CO2(0.192304),H2O(0.088559),N2(0.719137)
Intake port 1	101325	390	IC8H18(0.025508),N2(0.77292),O2(0.20157)
Intake port 2	101325	370	O2(0.23),N2(0.77)
Exhaust port	185731	1360	CO2(0.192304),H2O(0.088559),N2(0.719137)

Events

For this simulation 2 cyclic events were created for connecting the intake port and exhaust port to the cylinder region. The event is a valve type. Valve profile is taken from boundary conditions. A permanent event is also created for connecting intake port 1 and intake port 2 regions.

Boundary conditions

Boundary	Boundary type	Wall motion type	Temperature (K)	Pressure (Pa)	Region
Inflow	Inflow	_	363	101325	Intake port 2
Intake port 1	Wall	Stationary	425	_	Intake port 1
Intake port 2	Wall	Stationary	425	_	Intake port 2
Intake valve top	Wall	Translating	480	_	Intake port 1
Intake valve angle	Wall	Translating	480	_	Intake port 1
Intake valve bottom	Wall	Translating	480	_	Cylinder region
Cylinder head	Wall	Stationary	450	_	Cylinder region
Spark plug	Wall	Stationary	550	_	Cylinder region
Spark plug terminal	Wall	Stationary	600	_	Cylinder region
Liner	Wall	Stationary	450	_	Cylinder region
Piston	Wall	Translating	450	_	Cylinder region
Exhaust valve top	Wall	Translating	525	_	Exhaust port
Exhaust valve angle	Wall	Translating	525	_	Exhaust port
Exhaust Valve bottom	Wall	Translating	525	_	Cylinder region
Exhaust port	Wall	Stationary	500	_	Exhaust port
Outflow	Outflow	_	800	101325	Exhaust port

Wall motion profile for intake valve and exhaust valve are given as files 'intake_lift.in' and 'exhaust_lift.in'. The motion of the piston is defined as piston motion.

Grid control

Base grid size=0.004m

Adaptive mesh refinement (AMR)

AMR refine the mesh when the gradient of a parameter is higher than a particular value (Sub grid-scale value). In this case, AMR is given on cylinder, intake port1, and intake port2 regions. AMR is created for temperature and velocity with SGS 2.5 and 1 respectively. The maximum embedding level for both the AMR is 3.

Base grid size=4mm

Maximum embedding level = 3

Minimum cell size= `4/(2^3)=0.5 mm`

Also, a fixed embedding is created for intake valve angle and exhaust valve angle to avoid cell pairing. In order to capture the cylinder region a region-based embedding is given to it. A cyclic embedding is given to the injector also.

Physical models

Spray modeling

Spray modeling is used for simulating fuel injection. For gaseous spray, CONVERGE uses an Eulerian solver, and for liquid spray, CONVERGE uses a Lagrangian solver to model discrete parcels and an Eulerian solver to model continuous fluid domain.

The different parameters selected are shown below,

We need to set up an injector and nozzles. In this case, we use a single injector with 4 nozzles.

Nozzle diameter = 250 micro-meter

Circular injection radius = Nozzle radius

Spray cone angle = 10

• Nozzle 0
  • center 0.0823357 0.00100001 0.07019
  • Align Vector -0.732501 0.210489 -0.647408
• Nozzle 1
  • center 0.0823357 -0.00099999 0.07019
  • Align Vector -0.732501 -0.210489 -0.647408
• Nozzle 2
  • center 0.0823357 -0.0004 0.07019
  • Align Vector -0.5 -0.2 -0.647408
• Nozzle 3
  • center 0.0823357 0.0003 0.07019
  • Align Vector -0.5 0.2 -0.647408

Combustion modeling

For capturing the combustion of fuel combustion modeling is used. In this simulation, the SAGE model is used with fuel as IC18H18.

Turbulence model

RNG K epsilon

Result

Temperature change inside the combustion chamber

Pressure change inside the combustion chamber

Emission

The mole fraction of exhaust products is shown in the plot above.

Soot emission

Total cells

Since AMR is added the number of cells increases when the gradient is higher than the SGS value.

Compression ratio

Cylinder volume vs crank plot

Compression ratio=`(V_d+V_c)/V_c`

= displacement volume

= clearance volume

Minimum volume of the cylinder=0.00005 m3

Maximum volume of the cylinder=0.00055 m3

Compression ratio=`0.00055/0.00005`=11

Combustion efficiency

Peak integrated heat release rate=1240 J

Combustion efficency=(Total energy released/Energy content of fuel per cycle)*100

Mass of fuel=3e-5 Kg

LHV of fuel=43.44 MJ

Energy content of fuel per cycle= 3e-5*43.44 MJ =1303.2 J

Combustion efficency=(1240/1303.2)*100= 95.15 %

Power and torque

Work done=468.86

Combustion duration= 240 deg

Crank speed =3000 rpm= 50 RPS

Degrees per second= 18000

Time=240/18000=0.0133 s

Power= work done / Time= 468.86/0.0133=35252.6 W

Power(P) = (2*π*N*T)/60

Hence torque `T=(P*60)/(2 piN)`

T=`(35252.6*60)/(2*pi*3000`=112.21 N-m

Animation

Piston and valve motion

Flame propagation

Conclusion

The simulation of the PFI engine is performed and plotted different parameters and calculated engine performance.