simulation of spark ignition engine using converge
Objective
To simulate the spark-ignition engine with following given parameters and discuss the results with a finding of how much torque it will generate
Engine Geometric Parameters
- Bore =0.086 m
- Stroke = 0.09 m
- Connecting rod length = 0.18 m
- RPM = 3000
Run parameters
- Simulation mode: No Hydro
Simulation time parameters
- Start time: -520 deg
- end time: 120 deg
Boundary conditions
- Piston temperature - 450K
- Liner temperature - 450K
- Head temperature - 450K
- Spark Plug temperature - 550K
- Spark Plug electrode temperature - 600K
- Exhaust ports temperature - 500K
- Exhaust outflow - 1 bar
- Exhaust outflow temperature - 800k
- Exhaust species concentration - Calculate the stoichiometric condition
- Exhaust valve top temperature - 525K
- Exhaust valve angle temperature - 525K
- Exhaust valve bottom temperature - 525K
- Intake port - 1 temperature 425K
- Intake port - 2 temperature 425K
- Inflow pressure - 1 bar total pressure
- Inflow temperature - 363K
- Inflow species - Air
- Intake valve top temperature - 480K
- Intake valve angle temperature - 480K
- Intake valve bottom temperature - 480K
Initial conditions
- Intake port - 1 (closer to combustion chamber)
- ic8h18 - 0.025508
- o2 - 0.20157
- n2 - 0.77292
- Temperature - 390k
- pressure - 1 bar
- Intake port - 2 (away from combustion chamber)
- Air
- Temperature - 370K
- Pressure - 1 bar
- Cylinder
- Pressure - 1.85731 bar
- Temperature - 1360K
- Stoichiometric composition
Injection Parameters
- Fuel flow rate = 7.5e-4 Kg/second
- Injection start time = -480.0
- Injection duration = 191.2
- Fuel temperature = 330K
Nozzle positions
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
Spark Ignition Parameters
- Start of spark = -15 deg
- Spark duration = 10 deg
- Spark location = -0.003 0 0.0091
- Spark radius = 0.0005m
steps to simulate spark-ignition engine
- geometry preparation
- case setup
- processing
- postprocessing
1.1 geometry preparation
steps in geometry preparation
- geometry import and flagging boundaries with assigning volumetric regions to engine
- Clean up geometry or removing all topological errors
1.1.1 geometry import and flagging boundaries
- import si8_engine.stl dirty file to converge
- diagnose file by using diagnose deck for any geometrical errors in a file
1.2.1 clean up geometry and flagging boundaries
- case setup for ic engine
- volumetric regions in this IC Engine are a cylinder, intake port 1, intake port 2, exhaust region
1.2.2 assigning boundaries after setting up regions and initialization
Tools used in assigning boundaries are as follows;
- geometry deck - boundary - fence and flag
intake valve, exhaust valve and spark plug
1.2.3 removing all topological errors
below images show errors in geometry
- to remove these errors following tools are used
- geometry deck - delete and patch - (use of open edge)
- below image shows intersection triangles
- to remove this type of error we need to translating valve geometry (using transform tool) toward the cylinder region.
above image shows, there are no geometrical errors present in computational geometry.
2-case setup steps
- application type
- material
- simulation parameter
- boundary condition
- initial conditions and event
- physical model
- grid control
- post-processing
2.1 Application type
- select crank angle based ic engine
-
Engine Geometric Parameters
- Bore =0.086 m
- Stroke = 0.09 m
- Connecting rod length = 0.18 m
- RPM = 3000
2.2 material
- gas simulation
- parcel simulation
- global transport parameters
- reaction mechanism
- species
2.2.1 gas simulation
import thrm.dat and gas.dat fils and kept every parameter as its
2.2.2 parcel simulation
select predefined liquids as IC8H18
2.2.3 global transport parameters
use defined by software as it is
2.2.4 reaction mechanism
import mech.dat check for properties
2.2.5 species
parcel as IC8H18 and parcel as intake, NOX, exhaust, cylinder
2.3 simulation parameter
- run parameter
- simulation time parameter
- solver parameter
2.3.1 run parameter
no hydro simulation
2.3.1 simulation time parameter
from -520 to 120 degree for crank angle
2.3.3 solver parameter
as its software suggested
2.4 boundary
- intake port_2
- piston
- inflow
- liner
- cylinder head
- exhaust port
- outflow
- exhaust valve top
- exhaust valve angle geometry
- exhaust valve bottom
- intake port_1
- intake valve bottom
- intake valve angle
- intake valve top
- spark plug terminal
- spark plug
2.4.2 intake port_2
boundary type - wall
wall motion type - stationary
temperature boundary condition - 425 k
turbulent Kinetic energy boundary condition - zero normal gradients Neumann
turbulent dissipation (eps) boundary condition - wall model
2.4.3 piston
boundary type - wall
wall motion type - translating
surface movement - moving and follow the piston movement
temperature boundary condition - 450 k
turbulent Kinetic energy boundary condition - zero normal gradients Neumann
turbulent dissipation (eps) boundary condition - wall model
2.4.4 inflow
boundary type - inflow
pressure boundary condition - 101325 pa
velocity boundary condition - Neumann
temperature boundary condition - 363 k
species boundary condition - air
passive boundary condition - intake as one
2.4.5 liner
boundary type - wall
wall motion type - stationary
temperature boundary condition - 450 k
turbulent Kinetic energy boundary condition - zero normal gradients Neumann
turbulent dissipation (eps) boundary condition - wall model
2.4.6 cylinder head
boundary type - wall
wall motion type - stationary
temperature boundary condition - 425 k
turbulent Kinetic energy boundary condition - zero normal gradients Neumann
turbulent dissipation (eps) boundary condition - wall model
2.4.7 exhaust port
boundary type - wall
wall motion type - stationary
temperature boundary condition - 500 k
turbulent Kinetic energy boundary condition - zero normal gradients Neumann
turbulent dissipation (eps) boundary condition - wall model
2.4.8 outflow
boundary type - inflow
pressure boundary condition - 101325 pa
velocity boundary condition - Neumann
IN backflow
temperature backflow - 800k
species backflow -
CO2- mass fraction 0.192304
H2O- mass fraction 0.088559
N2- mass fraction 0.719137
2.4.9 exhaust valve top
boundary type - wall
wall motion type - translating
surface movement moving - user-defined as exhaust_lift.in
temperature boundary condition - 525 k
turbulent Kinetic energy boundary condition - zero normal gradients Neumann
turbulent dissipation (eps) boundary condition - wall model
2.4.10 exhaust valve angle
boundary type - wall
wall motion type - translating
surface movement moving - user-defined as exhaust_lift.in
temperature boundary condition - 525 k
turbulent Kinetic energy boundary condition - zero normal gradients Neumann
turbulent dissipation (eps) boundary condition - wall model
2.4.11 exhaust valve bottom
boundary type - wall
wall motion type - translating
surface movement moving - user-defined as exhaust_lift.in
temperature boundary condition - 525 k
turbulent Kinetic energy boundary condition - zero normal gradients Neumann
turbulent dissipation (eps) boundary condition - wall model
2.4.12 intake port_1
boundary type - wall
wall motion type - stationary
temperature boundary condition - 425 k
turbulent Kinetic energy boundary condition - zero normal gradients Neumann
turbulent dissipation (eps) boundary condition - wall model
2.4.13 intake valve bottom
boundary type - wall
wall motion type - translating
surface movement moving - user-defined as exhaust_lift.in
temperature boundary condition - 480 k
turbulent Kinetic energy boundary condition - zero normal gradients Neumann
turbulent dissipation (eps) boundary condition - wall model
2.4.14 intake valve angle
boundary type - wall
wall motion type - translating
surface movement moving - user-defined as exhaust_lift.in
temperature boundary condition - 480 k
turbulent Kinetic energy boundary condition - zero normal gradients Neumann
turbulent dissipation (eps) boundary condition - wall model
2.4.15 intake valve top
boundary type - wall
wall motion type - translating
surface movement moving - user-defined as exhaust_lift.in
temperature boundary condition - 480 k
turbulent Kinetic energy boundary condition - zero normal gradients Neumann
turbulent dissipation (eps) boundary condition - wall model
2.4.16 spark plug terminal
boundary type - wall
wall motion type - stationary
temperature boundary condition - 600 k
turbulent Kinetic energy boundary condition - zero normal gradients Neumann
turbulent dissipation (eps) boundary condition - wall model
2.4.17 spark plug
boundary type - wall
wall motion type - stationary
temperature boundary condition - 550 k
turbulent Kinetic energy boundary condition - zero normal gradients Neumann
turbulent dissipation (eps) boundary condition - wall model
2.5 initial conditions and events
- Region and initialization
- events
2.5.1 region and initialization
2.5.1.1 cylinder region
temperature 1360k
pressure 185731 pa
species as follows
CO2- mass fraction 0.192304
H2O- mass fraction 0.088559
N2- mass fraction 0.719137
2.5.1.2 intake_port_1
temperature 390k
pressure 101325 pa
species as follows
IC8H18- mass fraction 0.02550805
O2- mass fraction 0.201504
N2- mass fraction 0.7729215
2.5.1.3 intake_port_2
temperature 370k
pressure 101325 pa
species as follows
air
2.5.1.4 exhaust_region
temperature 1360k
pressure 185731 pa
species as follows
CO2- mass fraction 0.192304
H2O- mass fraction 0.088559
N2- mass fraction 0.719137
2.5.2 events cyclic and permanent is in between intake port one and two
disconnected triangle form to restrict or allow the flow between A and B
2.5.2.2 cyclic
2.6 physical model
- spray modelling
- combustion modelling
- turbulence modelling
- source/sink modelling
2.6.1 spray modelling
![\"\"](\"https://spray-imaging.com/images/spray%20no%20combustion-01.jpg?crc=3827810998\")
- converge use lagrangian model to capture the physics of parcel (collection of drops) and for heat, mass, moment transfer in discrete and continuous phase Euler model is used.
- converge uses a subgrid model to capture physics of Lagrange parcel.
- Due surrounding flow spray causes some drag force and spray undergoes a breakup
- primary break up
- secondary breakup - primary parcel further divided into a new small parcel
- evaporation - due surround temperature some parcel undergoes evaporation and they are further reducing their radius
- collision and coalescence - some parcels are collided together and form big parcel or they get partially collided
- dop drag - due to drag some parcel undergoes some flat bubble structure.
- turbulent dispersion - It calculates how parcel undergoes fluctuating velocity and change its shape and size?
1- parcel distribution (how to parcel should be distributed along spray cone angle)
In this simulation parcel distributed evenly is selected
2 - turbulent dispersion - amongst O’Rourke model is selected.
3- evaporation model - how the radius of parcel changes with respect to time and how source terms of species term added to it and change the further size of the parcel is calculated by Frosslling and Chinag model
4-selecting the evaporation source
example - consider there to a parcel of multicomponent species C4H8 AND C14H30
4.1 source specified species (multicomponent species evaporates into user-defined species)- C4H8 AND C14H30 Evaporates and form user_defined species
4.2 source all species (multicomponent species evaporates into basic species) - C4H8 Evaporates C4H8 AND C14H30 Evaporates C14H30
4.3 source composite species (multicomponent species evaporates into composite species that is three or four species) C4H8 AND C14H30 Evaporates and form composite species (defined in composite.in)
5 specifying the maximum radius of ODE droplet heating
5.1 if a drop sie exceeds a maximum value, converge will assume a radial varying temperature distribution
5.2 if a drop sie exceeds a maximum value, converge will assume a uniform varying temperature distribution
spray penetration
- If the ambient temperature is too high then mass injected is gets vaporised so to analyse this effect liquid penetration model is introduced, LPL gets increased with respect to time and after some time it reaches steady state, Liquid fuel mass fraction for calculating penetration is 0.98 of the total mass injected.
- 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 centre 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. - CONVERGE also calculates vapour in spray cone and that is calculated by vapour penetration model
- To measure the VPL, CONVERGE requires two parameters in a spray.in the vapour
penetration fraction, vapour penetration factor, and the penetration bin size, penetration bin size. - For each cell inside the spray cone, if the mass fraction of fuel vapour in the cell exceeds the vapour penetration factor and if the cell size does not exceed the penetration bin size, CONVERGE calculates the distance from the centre of the nozzle hole to the centre of the cell.
Collison and drag modelling
collision models are NTC collision algorithm, O’Rourke algorithm and no collision
use a collision mesh should be ticked for better visualization of spray like the above image
drag modelling
There are three options or algorithm to simulate drag parcels drag, spherical drop, dynamic range.
Drop/wall interaction
Three options for modelling drop/wall interaction, as described in the
following sections:
· Rebound/Slide Model - after hitting wall drop getts rebound
· Wall Film Model -use a hybrid approach in between vanish and slide model (used in this simulation)
· Drop Vanish Model - after hitting wall drop get vanished
above image shows Kuhnke model for droplet interaction with the wall
In this simulation O’Rourke used
Injector setup
hear rate shape of graph profile as follows
below graph shows a mass flow rate of IC8H18 is sprayed in a domain for a specified crank angle.
for spark-ignition engines following spray breakup models are used
for time/temp/eps/mass/size
RPM of engine 3000
RPS of engine 3000/60 50
degree per second (1degree per second = 0.00278 revolution second) 18000
second per degree 1/18000 5.555556e-5
second per 720 degrees 720*60/(3000*360) 0.04
total injected mass in kg ( 0.04 * 5.555556e-5) 3e-5
start of injection -480 degree
injection duration 191.2 degree
temperature/eps 330k
Nozzle setup
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
below image shows a calculation of injection of IC8H18 by an injector
2.6.2 combustion modelling
select sage model
fuel species setup IC8H18
start period of combustion as -17 degree
end period of combustion as the 130-degree exhaust valve is opening
combustion temperature cut of 600k
2.6.3 turbulence modelling
select RANS model
2.6.4 source and sink modelling
There are two sources at the same location so it dumping 0.04J together is required in the breakdown stage that is starting of spark and for next -5 degree, only 0.02J energy is needed.
set parameter of spark ignition parameter
- Start of spark = -15 deg
- Spark duration = 10 deg
- Spark location = -0.003 0 0.0091 In shape tab
- Spark radius = 0.0005m in shape tab
source 1
start of spark as -15 degree
end of spark -14 degree
- Spark location = -0.003 0 0.0091 In shape tab
- Spark radius = 0.0005m in shape tab
- energy 0.02 J
- mode cyclic
source 2
start of spark as -15 degree
end of spark -0.5 degree
- Spark location = -0.003 0 0.0091 In shape tab
- Spark radius = 0.0005m in shape tab
- energy 0.02 J
- mode cyclic
2.7 grid control
- base control 0.004m
- adaptive mesh refinement
- fixed embedding
below image is timing diagram and it shows all grid control setup with respect to crank angle
below image shows embedded regions
2.8 postprocessing
- post variable selection
- output files
- inter region flow rate control
Post-processing
no hydro PFI_SI8 animation angle 1
no hydro PFI_SI8 animation angle 2
Full hydro PFI_si8 with some output file
Full hydro PFI_si8 with a meshing of some output files
Plotting important parameters
Mean temperature vs crank angle
above graph shows the mean of maximum and minimum temperature in-cylinder region
Gamma vs crank angle
value of gamma is not constant throughout cylinder its function of time
Injected mass vs crank angle
above graph shows spray injection of mass as a function of crank angle
Liquid spray drops vs crank angle
above graph shows how a number of liquid spay drops vs crank angle
Hioy soot vs crank angle
a deep black powdery or flaky substance consisting largely of amorphous carbon, produced by the incomplete burning of organic matter.
above graph shows a mass of Hiroy soot passing through the exhaust port
Injected velocity trough nozzle vs crank angle
injected mass as a function of mass flow rate vs crank angle asset before in setup.
pressure vs volume graph
`compression ratio = (max volume )/(min volume)=0.00057422/(5.70294e-05)=10.0688`
max pressure achieved is 3.88MPA
The heat released vs crank angle
total heat released is 1241.16J
RPM of engine 3000
RPS of engine 3000/60 50
degree per second (1degree per second = 0.00278 revolution second) 18000
second per degree 1/18000 5.555556e-5
second per 720 degrees 720*60/(3000*360) 0.04
total injected mass in kg ( 0.04 * 5.555556e-5) 3e-5
calorific value of gasoline = 45Mkg
Combustion efficiency
A fraction of the fuel\'s chemical energy is not released inside the engine during the combustion process it\'s useful to define combustion efficiency.
combustion efficiency = `(Total heat released) /( mass of fuel * calorific value of gasoline)`
= 1241.16/45*30 = 1241.16/1350= 0.9193 = 91.93 %
combustion efficiency is 91.93 %
power calculations
RPM of engine 3000
RPS of engine 3000/60 50
degree per second (1degree per second = 0.00278 revolution second) 18000
second per degree 1/18000 5.555556e-5
second per 240.199 degrees 240.199*60/(3000*360) 0.01334
power in watt 468.446/0.0133443888888889 35104.342649 torque in N.M 35.1043KW/3000 111.73
So torque produced by engine is 111.73N.M
Wall heat transfer models requirement
- Heat transfer is one of the major factors affecting the performance, efficiency, and emissions of internal combustion engines.
- To Design (shape and size) of a combustion engine
- To calculate thermal stress, fatigue and creep stresses in the engine so that accurate material can be selected for manufacturing of engine
- Also to reduce thermal energy loss to the environment so that designed can increase efficiency with this type of analysis
- To predict what type of lubricant is required
- To design of the turbocharger
- To design of an engine in cold, medium and temperature in the region, to reduce pollutant content of burnt gas, etc
Because above mention requirement wall heat transfer model is required.
CONVERGE can calculate wall heat transfer by adding solid.dat and tranfer.dat and adding conjugate heat simulation in the engine.
Assumptions made in the calculation of wall heat models are as follows :
- Flow is parallel to the chamber walls with negligible flow normal to the walls
- Quasi-steady flow with negligible transients
- Constant density and transport properties in the boundary layer
- High Reynolds number flow, very thin laminar shear layer
- Zero pressure gradients along with the flow
- No combustion and chemically inert mixture
Above model is equilibrium wall heat transfer model,
- The assumptions are not accepted because that are not realistic in real-world problem and thus with this assumption, whatever models are present they are under predict wall heat transfer. The first assumption is not true in a real situation because heat may transfer any direction during combustion in the chamber depends on environmental conditions. The third assumption is also highly excepted because there is a large temperature gradient near the wall and thus density does not remain constant.
- To solve this problem non-equilibrium models are required or some assumption has to be relaxed, some models are WernerWengle, Angleberger, Jayatilleke, etc are present.
significance of cA10,CA50,CA90
CA 10,50,90
The crank angle at which the amount of burned fuel reaches 10%,50%,90% of its maximum value for the cycle.
CA10 = 6.8 that this crank angle amount of burned fuel reaches 10 per cent of supplied fuel.
CA50 =18.4
CA90=31.7
Conclusion
Hense we have setup whole design parameter on spark plug ignition parameter and analysed the result. This engine produced the torque of 111.37NM and have a compression ratio of 10.06 with a combustion efficiency of 91.93 percentage.
reference
1 https://spray-imaging.com/spray-description.html
2 converge manual