Spark Ignition Engine
Libraries:
Simscape /
Driveline /
Engines & Motors
Description
The Spark Ignition Engine block represents a naturally aspirated, spark-ignited internal combustion engine. The engine can be an arbitrary configuration of one to four cylinders. This block is a composite block that uses a subcomponent implementation of these blocks:
The SI Combustion Cylinder block represents an individual spark ignited combustion cylinder. The Spark Ignition Engine block controls how many SI Combustion Cylinder blocks it uses in the subcomponent implementation based on the value of the Number of cylinders parameter. You can adjust the valve timing to suit traditional gasoline engine applications as well as hybrid electric and plug-in hybrid electric vehicle applications.
The Ignition Trigger block controls the igniter timing for the SI Combustion Cylinder blocks.
The Air Intake block provides the intake manifold pressure to the SI Combustion Cylinder block. To enable the air intake implementation, set Compute air intake dynamics to
On
.The Crank Shaft block connects to each SI Combustion Cylinder block to report the crank-angle-resolved instantaneous torque.
The Exhaust Manifold Thermal block abstracts the thermodynamics of the exhaust manifold and reports the temperature of the exhaust manifold. To compute the exhaust manifold thermal effects, set Compute exhaust manifold temperature to
On
.
Many of the Spark Ignition Engine parameters are identical to the parameters in the subcomponent blocks, and when the block implements subcomponent blocks, it uses the equations from those blocks. You can learn more about how the Spark Ignition Engine block uses each parameter by visiting the reference pages for the subcomponent blocks. You can use this block to learn how to create your own implementations of the subcomponent blocks by viewing the source code.
Equations
The block derives performance information about the engine components using their respective relationship with the crank position, θ, where 0 degrees ≤ θ < 720 degrees. The block defines the crank starting position as the intake stroke at top dead center. For a four-stroke engine, each cylinder is uniquely affiliated with a crank position, where the crank position for a given cylinder i is θi. The block derives the angular velocity from θ as
The block sets the first cylinder θ1 =
θ regardless of how many cylinders you simulate. When you set
Number of cylinders to Two
cylinders
, the block calculates
θ2 as
where Δ is the Spark angle difference parameter.
When you set Number of cylinders to Three
cylinders
, the block assumes that the cylinders are evenly phased
such that
When you set Number of cylinders to Four
cylinders
, the block assumes that the spark angle difference is
180 degrees. You can select the firing order using the Firing
order parameter.
Assumptions and Limitations
The block ignores knocking and other combustion instabilities.
The block ignores internal and external exhaust gas recirculation.
Examples
Single Cylinder Spark Ignition Engine
A crank-angle-resolved, naturally aspirated spark ignition engine. Control inputs such as throttle, intake VVT, air-to-fuel ratio, and spark advance vary during the simulation. You can simulate results from either an Otto cycle engine or an Atkinson cycle engine.
Ports
Inputs
IgSw — Ignitor switch, binary
physical signal
Physical signal output associated with the ignitor, where
0
turns off the ignitor and 1
turns on the ignitor.
Dependencies
To enable this port, set Spark input type to
Fixed
or Spark
angle
.
Pim — Intake manifold pressure input, kPa
physical signal
Physical signal input associated with the intake manifold, in kPa.
When you set Compute air intake dynamics to
Off
, you supply the intake manifold
pressure using this port. You can use this port as an alternative to
providing the throttle command to port Thr.
Dependencies
To enable this port, set Compute air intake
dynamics to Off
.
Thr — Throttle command input, unitless
physical signal
Physical signal input associated with the normalized throttle command,
where 0
represents a fully closed throttle, and
1
represents a fully open throttle. The block
maps this input to a throttle-open angle between 0
and 90
degrees.
Dependencies
To enable this port, set Compute air intake
dynamics to On
.
InVT — Intake Variable Valve Timing input, deg
physical signal
Physical signal input associated with the angle to shift the intake
valve open and close timings, in degrees
. Positive
values advance the timing and negative values delay the timing.
Dependencies
To enable this port, set Intake Variable Valve
Timing to On
.
ExVT — Exhaust Variable Valve Timing input, deg
physical signal
Physical signal input associated with angle to shift the exhaust valve open and close timings, in degrees. Negative values advance the timing and positive values delay the timing.
Dependencies
To enable this port, set Exhaust Variable Valve
Timing to On
.
AfrCmd — Air-fuel ratio command input, unitless
physical signal
Physical signal input associated with the unitless air-fuel ratio
command. Note that this is different from the stoichiometric air-fuel
ratio for gasoline, which the block fixes at
14.6
.
Dependencies
To enable this port, set Input air-fuel ratio
to On
and Input injector pulse
width to Off
.
InjPw — Injector pulse width input, ms
physical signal
Physical signal input associated with the duration during which the injector is open to inject fuel, in ms. The block multiplies this signal by the value of the Injector slope parameter to calculate the amount of fuel that the injector releases during one pulse.
Dependencies
To enable this port, set Input air-fuel ratio
to On
and Input injector pulse
width to On
.
SA — Spark angle input, deg
physical signal
Physical signal input associated with the spark angle before top dead center, in deg.
Dependencies
To enable this port, set Spark input type to
Spark angle
.
IgTrig — Ignition trigger input, unitless
physical signal
Physical signal input associated with the ignition trigger. The block
treats a rise from 0
to 1
as a
trigger. The input must return to 0
before the block
accepts another trigger.
Dependencies
To enable this port, set Spark input type to
Spark trigger event
.
Pback — Exhaust back pressure input, kPa
physical signal
Physical signal input associated with the exhaust back pressure, in kPa.
Dependencies
To enable this port, set Input back pressure
to On
.
Outputs
AvrTrq — Cycle-average net indicated torque output, N*m
physical signal
Physical signal output associated with the cycle-average net indicated torque in Nm.
Dependencies
To enable this port, set Cycle-average net indicated torque to
On
.
AvrSpd — Cycle-average speed output, rad/s
physical signal
Physical signal output associated with the cycle-average speed output, in rad/s.
Dependencies
To enable this port, set Cycle-average speed to
On
.
Pim — Intake manifold pressure output, kPa
physical signal
Physical signal output associated with the intake manifold pressure, in kPa.
Dependencies
To enable this port, set Intake manifold pressure to
On
.
crkpos — Crank position output, deg
physical signal
Physical signal output associated with the crank position, in degrees.
Dependencies
To enable this port, set Crank position to
On
.
AirMassFlow — Cylinder air mass flow output, g/s
physical signal
Physical signal output associated with the air mass flow, in g/s.
Dependencies
To enable this port, set Cylinder air mass flow to
On
.
FuelMassFlow — Cylinder fuel mass flow output, g/s
physical signal
Physical signal output associated with the fuel mass flow, in g/s.
Dependencies
To enable this port, set Cylinder fuel mass flow to
On
.
AFR — Air-fuel ratio output, unitless
physical signal
Physical signal output associated with the unitless air-fuel ratio response that the
block attains during operation. Note that this is different from the
stoichiometric air-fuel ratio for gasoline, which the block fixes at
14.6
.
Dependencies
To enable this port, set Air-fuel ratio to
On
.
Vcyl — Cylinder volume output, cm^3
physical signal
Physical signal output associated with the cylinder volume, in cm3.
Dependencies
To enable this port, set Cylinder volume to
On
.
Pcyl — Cylinder pressure output, MPa
physical signal
Physical signal output associated with the cylinder pressure, in MPa.
Dependencies
To enable this port, set Cylinder pressure to
On
.
Tcyl — Cylinder temperature output, K
physical signal
Physical signal output associated with the cylinder temperature, in K.
Dependencies
To enable this port, set Cylinder temperature to
On
.
Conserving
F — Crank shaft driveline connection
mechanical rotational
Mechanical rotational conserving port associated with the crankshaft connection to the driveline. Include friction and inertia here to simulate engine load or directly connect other driveline elements.
Parameters
Mechanical
Number of cylinders — Total cylinder count
Single Cylinder
(default) | Two Cylinders
| Three Cylinders
| Four Cylinders
Number of spark ignition cylinders.
Spark angle difference — Two-cylinder engine spark angle phase
270
deg
(default) | positive scalar
Spark angle difference for two-cylinder engines.
Dependencies
To enable this parameter, set Number of
cylinders to Two
Cylinders
.
Firing order — Ignition order for four cylinder engines
1-3-4-2
(default) | 1-3-2-4
Firing order for four-cylinder engines. Firing order is engine specific, but your selection for this parameter will not affect the block performance. Controller development requires this information.
Dependencies
To enable this parameter, set Number of
cylinders to Four
Cylinders
.
Bore — Cylinder diameter
72.5
mm
(default) | positive scalar
Diameter of the piston cylinder.
Stroke — Piston travel distance
80.5
mm
(default) | positive scalar
Distance the piston head travels within the cylinder.
Connecting-rod length — Length of connecting rod
141
mm
(default) | positive scalar
Length of the piston connecting rod from hole center to hole center.
Compression ratio — Static compression ratio
11.0
(default) | positive scalar
Ratio of the maximum to minimum cylinder volume.
Ambient
Ambient pressure — Reference air pressure
101.325
kPa
(default) | positive scalar
Pressure of the air entering the intake.
Ambient temperature — Reference temperature
298.15
K
(default) | positive scalar
Temperature of the air entering the intake.
Ambient air density — Reference density
1.225
mg/cm^3
(default) | positive scalar
Density of the air entering the intake.
Specific gas constant of dry air — Specific gas constant of dry air
288.1965
J/(K*kg)
(default) | positive scalar
Specific gas constant of dry air.
Air Intake
Compute air intake dynamics — Option to compute air intake dynamics
On
(default) | Off
Whether to compute the air intake dynamics. Setting this parameter to
On
enables these parameters:
Throttle response time constant
Throttle rest angle
Throttle plate diameter
Throttle leakage area
Intake manifold volume
Throttle response time constant — Throttle response time constant
0.1
s
(default) | positive scalar
Time constant associated with the response rate of the engine to the throttle command.
Dependencies
To enable this parameter, set Compute air intake
dynamics to On
.
Throttle rest angle — Released throttle position
3
deg
(default) | positive scalar
Radial distance from the resting throttle position to
0
degrees.
Dependencies
To enable this parameter, set Compute air intake
dynamics to On
.
Throttle plate diameter — Throttle plate diameter
5
cm
(default) | positive scalar
Diameter of the butterfly valve disc in the throttle body.
Dependencies
To enable this parameter, set Compute air intake
dynamics to On
.
Throttle leakage area — Throttle leakage area
1
cm^2
(default) | nonnegative scalar
Cumulative area of the throttle leakage.
Dependencies
To enable this parameter, set Compute air intake
dynamics to On
.
Intake manifold volume — Intake manifold volume
1000
cm^3
(default) | positive scalar
Volumetric capacity of the intake manifold.
Dependencies
To enable this parameter, set Compute air intake
dynamics to On
.
Valves
Discharge coefficient for intake valve — Intake valve discharge coefficient
0.9
(default) | positive scalar
Ratio of actual discharge to ideal discharge for the intake valve.
Intake valve open before TDC — IVO crank position
15
deg
(default) | scalar in the range [-360,360]
Crank position before top dead center at which the intake valve opens. Measure from top dead center to the crank position in the opposite direction of the crank rotation.
Intake valve close after BDC — IVC crank position
50
deg
(default) | scalar in the range [-360,360]
Crank position after bottom dead center at which the intake valve closes. Measure from bottom dead center to the crank position in the same direction of the crank rotation.
Exhaust valve open before BDC — EVO crank position
55
deg
(default) | scalar in the range [-360,360]
Crank position before bottom dead center at which the exhaust valve opens. Measure from bottom dead center to the crank position in the opposite direction of the crank rotation.
Exhaust valve close after TDC — EVC crank position
10
deg
(default) | scalar in the range [-360,360]
Crank position after top dead center at which the exhaust valve closes. Measure from top dead center to the crank position in the same direction of the crank rotation.
Intake Variable Valve Timing — Intake variable valve timing option
On
(default) | Off
Option to control the intake valve timing. Set this parameter to
On
to enable the
InVT port.
Exhaust Variable Valve Timing — Exhaust variable valve timing option
On
(default) | Off
Option to control the exhaust valve timing. Set this parameter to
On
to enable the
ExVT port.
Fuel
Lower heating value for gasoline — Fuel net calorific value
44.3
MJ/kg
(default) | positive scalar
Lower heating value for gasoline. This value is also known as the fuel net calorific value.
Input air-fuel ratio — Air-fuel ratio parameter option
On
(default) | Off
Option to specify the air-fuel ratio by using the Air-fuel ratio parameter or the AfrCmd port.
Air-fuel ratio — Air-fuel ratio
14.6
(default) | positive scalar
Mixture ratio of air to fuel.
Dependencies
To enable this parameter, set Input air-fuel
ratio to Off
.
Input injector pulse width — Pulse width parameterization
On
(default) | Off
Option to specify the injector pulse width.
Dependencies
To enable this parameter, set Input air-fuel
ratio to On
.
Injector slope — Injector slope
6.5
mg/ms
(default) | positive scalar
Slope of the fuel injector mass flow rate.
Dependencies
To enable this parameter, set Input air-fuel
ratio to On
and
Input injector pulse width to
On
.
Combustion
Spark input type — Spark input type
Fixed
(default) | Spark angle
| Spark trigger event
Whether to parameterize the spark input using a fixed value, spark angle, or spark trigger events.
Spark advance BTDC — Spark advance before top dead center
20
deg
(default) | positive scalar
Spark advance before top dead center.
Combustion duration — Combustion duration
50
deg
(default) | positive scalar
Duration of combustion as a portion of the crank shaft rotation.
Cylinder pressure slow decay time constant — Cylinder pressure slow decay rate
60
s
(default) | positive scalar
Time constant for the cylinder pressure slow decay.
Cylinder temperature slow decay time constant — Cylinder temperature slow decay rate
600
s
(default) | positive scalar
Time constant for the cylinder temperature slow decay.
Exhaust
Exhaust gas temperature decay time constant — Exhaust temperature decay rate
5
ms
(default) | positive scalar
Time constant for the exhaust gas temperature decay.
Input back pressure — Back pressure input option
On
(default) | Off
Option to input the back-pressure pressure constant and speed constant.
Back-pressure pressure constant — Pressure constant for back pressure
50
kPa
(default) | positive scalar
Back-pressure pressure constant.
Dependencies
To enable this parameter, set Input back
pressure to Off
.
Back-pressure speed constant — Speed constant for back-pressure
6000
rpm
(default) | positive scalar
Back-pressure speed constant.
Dependencies
To enable this parameter, set Input back
pressure to Off
.
Compute exhaust manifold temperature — Option to compute exhaust manifold temperature
On
(default) | Off
Whether the block computes the exhaust manifold temperature. Setting
this parameter to On
enables these parameters:
Surface area of exhaust wall
Mass of exhaust wall
Heat capacity of exhaust wall
Time constant of exhaust heat flow
Convective heat transfer coefficient for the outer side of exhaust
Radiation constant
Stefan-Boltzmann constant
Surface area of exhaust wall — Exhaust wall surface area
1
m^2
(default) | positive scalar
Surface area of the exhaust wall. This is only the surface area of the internal wall that makes contact with the exhaust.
Dependencies
To enable this parameter, set Compute exhaust manifold
temperature to On
.
Mass of exhaust wall — Exhaust wall total mass
5
kg
(default)
Mass of the exhaust wall.
Dependencies
To enable this parameter, set Compute exhaust manifold
temperature to On
.
Heat capacity of exhaust wall — Exhaust wall heat capacity
100
J/(K*kg)
(default) | positive scalar
Heat capacity of the exhaust wall.
Dependencies
To enable this parameter, set Compute exhaust manifold
temperature to On
.
Time constant of exhaust heat flow — Exhaust heat flow time constant
10
s
(default) | positive scalar
Time constant for the rate of exhaust heat flow.
Dependencies
To enable this parameter, set Compute exhaust manifold
temperature to On
.
Convective heat transfer coefficient for the outer side of exhaust — Exhaust external convective heat transfer coefficient
100
W/(K*m^2)
(default) | positive scalar
Convective heat transfer coefficient for the outer side of the exhaust.
Dependencies
To enable this parameter, set Compute exhaust manifold
temperature to On
.
Radiation constant — Exhaust radiation constant
0.3
(default) | positive scalar
Radiation constant of the exhaust.
Dependencies
To enable this parameter, set Compute exhaust manifold
temperature to On
.
Stefan-Boltzmann constant — Stefan-Boltzmann constant of exhaust
5.7e-8
W/(K^4*m^2)
(default) | positive scalar
Stefan-Boltzmann constant for the total exhaust.
Dependencies
To enable this parameter, set Compute exhaust manifold
temperature to On
.
Simulation
Initial intake manifold pressure — Initial pressure inside intake manifold
101.325
kPa
(default) | positive scalar
Intake manifold pressure at the start of the simulation.
Initial crank position (0-720 CAdeg) — Initial crank position
0
deg
(default) | scalar in the range [0,720]
Crank position at the start of the simulation.
Initial engine speed — Initial engine speed
0
rpm
(default) | nonnegative scalar
Rotational speed of the engine at the start of the simulation.
Engine speed simulation limit — Maximum engine speed
8500
rpm
(default) | positive scalar
Maximum engine speed allowed during the simulation. If the block exceeds this value, it will generate an error and stop the simulation.
Output
Engine outlet gas energy flow — Option to output engine outlet gas energy flow
Off
(default) | On
Whether to output engine outlet gas energy flow from physical signal port Weo.
Cylinder volume — Option to output the cylinder volume
On
(default) | Off
Whether to output the cylinder volume from physical signal port Vcyl.
Cylinder pressure — Option to output cylinder pressure
On
(default) | Off
Whether to output the cylinder pressure from physical signal port Pcyl.
Cylinder temperature — Option to output cylinder temperature
On
(default) | Off
Whether to output the cylinder temperature from physical signal port Tcyl.
Air/fuel ratio — Option to output the air-to-fuel ratio
On
(default) | Off
Whether to output the air-to-fuel ratio from physical signal port AFR.
Air mass flow — Option to output cylinder air mass flow
On
(default) | Off
Whether to output the intake manifold pressure from physical signal port AirMassFlow.
Fuel mass flow — Option to output fuel mass flow
On
(default) | Off
Whether to output the fuel mass flow from physical signal port FuelMassFlow.
Version History
Introduced in R2022aR2024b: Simulate an Atkinson cycle
When you adjust the intake and exhaust valve timings to align with the Atkinson cycle, the block demonstrates the expected engine behavior.
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