CI Core Engine
Compressionignition engine from intake to exhaust port
 Library:
Powertrain Blockset / Propulsion / Combustion Engine Components / Core Engine
Description
The CI Core Engine block implements a compressionignition (CI) engine from intake to the exhaust port. You can use the block for hardwareintheloop (HIL) engine control design or vehiclelevel fuel economy and performance simulations.
The CI Core Engine block calculates:
Brake torque
Exhaust temperature
Airfuel ratio (AFR)
Fuel rail pressure
Engineout (EO) exhaust emissions:
Hydrocarbon (HC)
Carbon monoxide (CO)
Nitric oxide and nitrogen dioxide (NOx)
Carbon dioxide (CO_{2})
Particulate matter (PM)
Air Mass Flow
To calculate the air mass flow, the compressionignition (CI) engine uses the CI Engine SpeedDensity Air Mass Flow Model. The speeddensity model uses the speeddensity equation to calculate the engine air mass flow, relating the engine intake port mass flow to the intake manifold pressure, intake manifold temperature, and engine speed.
Brake Torque
To calculate the engine torque, you can configure the block to use either of these torque models.
Brake Torque Model  Description 

CI Engine Torque Structure Model 
The CI core engine torque structure model determines the engine torque by reducing the maximum engine torque potential as these engine conditions vary from nominal:
To account for the effect of postinject fuel on torque, the model uses a calibrated torque offset table. 
CI Engine Simple Torque Model  For the simple engine torque calculation, the CI engine uses a torque lookup table map that is a function of engine speed and injected fuel mass. 
Fuel Flow
In the CI Core Engine and CI Controller blocks, you can represent multiple injections with the start of injection (SOI) and fuel mass inputs to the model. To specify the type of injection, use the Fuel mass injection type identifier parameter.
Type of Injection  Parameter Value 

Pilot 

Main 

Post 

Passed 

The model considers Passed
fuel injections and fuel injected
later than a threshold to be unburned fuel. Use the Maximum start of injection angle
for burned fuel, f_tqs_f_burned_soi_limit parameter to specify the
threshold.
To calculate the engine fuel mass flow, the CI Core Engine block uses fuel mass flow delivered by the injectors and the engine airflow.
${\dot{m}}_{fuel}=\frac{N\cdot {N}_{cyl}}{Cps\left(\frac{60s}{\mathrm{min}}\right)\left(\frac{1000mg}{g}\right)}{\displaystyle \sum {m}_{fuel,inj}}$
To calculate the fuel economy for highfidelity models, the block uses the volumetric fuel flow.
$${Q}_{fuel}=\frac{{\dot{m}}_{fuel}}{\left(\frac{1000kg}{{m}^{3}}\right)S{g}_{fuel}}$$
The equation uses these variables.
${\dot{m}}_{fuel}$  Fuel mass flow, g/s 
m_{fuel,inj}  Fuel mass per injection 
$$Cps$$  Crankshaft revolutions per power stroke, rev/stroke 
${N}_{cyl}$  Number of engine cylinders 
N  Engine speed, rpm 
Q_{fuel}  Volumetric fuel flow 
Sg_{fuel}  Specific gravity of fuel 
The block uses the internal signal FlwDir
to track the direction of the flow.
AirFuel Ratio
To calculate the airfuel (AFR) ratio, the CI Core Engine and SI Core Engine blocks implement this equation.
$AFR=\frac{{\dot{m}}_{air}}{{\dot{m}}_{fuel}}$
The CI Core Engine uses this equation to calculate the relative AFR.
$\lambda =\frac{AFR}{AF{R}_{s}}$
To calculate the exhaust gas recirculation (EGR), the blocks implement this equation. The calculation expresses the EGR as a percent of the total intake port flow.
$$EG{R}_{pct}=100\frac{{\dot{m}}_{intk,b}}{{\dot{m}}_{intk}}=100{y}_{intk,b}$$
The equations use these variables.
$AFR$  Airfuel ratio 
AFR_{s}  Stoichiometric airfuel ratio 
${\dot{m}}_{intk}$  Engine air mass flow 
${\dot{m}}_{fuel}$  Fuel mass flow 
λ  Relative AFR 
y_{intk,b}  Intake burned mass fraction 
EGR_{pct}  EGR percent 
${\dot{m}}_{intk,b}$  Recirculated burned gas mass flow rate 
Exhaust Temperature
The exhaust temperature calculation depends on the torque model. For both torque models, the block implements lookup tables.
Torque Model  Description  Equations 

 Exhaust temperature lookup table is a function of the injected fuel mass and engine speed. 
${T}_{exh}={f}_{Texh}(F,N)$ 
Torque Structure 
The nominal exhaust temperature, Texh_{nom}, is a product of these exhaust temperature efficiencies:
The exhaust temperature, Texh_{nom}, is offset by a post temperature effect, ΔT_{post}, that accounts for post and late injections during the expansion and exhaust strokes. 
$\begin{array}{l}{T}_{exhnom}=SO{I}_{exhteff}MA{P}_{exhteff}MA{T}_{exhteff}O2{p}_{exhteff}FUEL{P}_{exhteff}Tex{h}_{opt}\\ {T}_{exh}={T}_{exhnom}+\Delta {T}_{post}\\ \\ SO{I}_{exhteff}={f}_{SO{I}_{exhteff}}\left(\Delta SOI,N\right)\\ MA{P}_{exhteff}={f}_{MA{P}_{exhteff}}\left(MA{P}_{ratio},\lambda \right)\\ MA{T}_{exhteff}={f}_{MA{T}_{exhteff}}\left(\Delta MAT,N\right)\\ O2{p}_{exhteff}={f}_{O2{p}_{exhteff}}\left(\Delta O2p,N\right)\\ Tex{h}_{opt}={f}_{Texh}(F,N)\end{array}$ 
The equations use these variables.
F  Compression stroke injected fuel mass 
N  Engine speed 
Texh  Exhaust manifold gas temperature 
Texh_{opt}  Optimal exhaust manifold gas temperature 
ΔT_{post}  Post injection temperature effect 
Texh_{nom}  Nominal exhaust temperature 
SOI_{exhteff}  Main SOI exhaust temperature efficiency multiplier 
ΔSOI  Main SOI timing relative to optimal timing 
MAP_{exheff}  Intake manifold gas pressure exhaust temperature efficiency multiplier 
MAP_{ratio}  Intake manifold gas pressure ratio relative to optimal pressure ratio 
λ  Intake manifold gas lambda 
MAT_{exheff}  Intake manifold gas temperature exhaust temperature efficiency multiplier 
ΔMAT  Intake manifold gas temperature relative to optimal temperature 
O2P_{exheff}  Intake manifold gas oxygen exhaust temperature efficiency multiplier 
ΔO2P  Intake gas oxygen percent relative to optimal 
FUELP_{exheff}  Fuel rail pressure exhaust temperature efficiency multiplier 
ΔFUELP  Fuel rail pressure relative to optimal 
EO Exhaust Emissions
The block calculates these engineout (EO) exhaust emissions:
Hydrocarbon (HC)
Carbon monoxide (CO)
Nitric oxide and nitrogen dioxide (NOx)
Carbon dioxide (CO_{2})
Particulate matter (PM)
The exhaust temperature determines the specific enthalpy.
${h}_{exh}=C{p}_{exh}{T}_{exh}$
The exhaust mass flow rate is the sum of the intake port air mass flow and the fuel mass flow.
${\dot{m}}_{exh}={\dot{m}}_{intake}+{\dot{m}}_{fuel}$
To calculate the exhaust emissions, the block multiplies the emission mass fraction by the exhaust mass flow rate. To determine the emission mass fractions, the block uses lookup tables that are functions of the engine torque and speed.
$$\begin{array}{l}{y}_{exh,i}={f}_{i\_frac}({T}_{brake},N)\\ {\dot{m}}_{exh,i}={\dot{m}}_{exh}{y}_{exh,i}\end{array}$$
The fraction of air and fuel entering the intake port, injected fuel, and stoichiometric AFR determine the air mass fraction that exits the exhaust.
$${y}_{exh,air}=\mathrm{max}\left[{y}_{in,air}\frac{{\dot{m}}_{fuel}+{y}_{in,fuel}{\dot{m}}_{intake}}{{\dot{m}}_{fuel}+{\dot{m}}_{intake}}AF{R}_{s}\right]$$
If the engine is operating at the stoichiometric or fuel rich AFR, no air exits the exhaust. Unburned hydrocarbons and burned gas comprise the remainder of the exhaust gas. This equation determines the exhaust burned gas mass fraction.
$${y}_{exh,b}=\mathrm{max}\left[(1{y}_{exh,air}{y}_{exh,HC}),0\right]$$
The equations use these variables.
${T}_{exh}$  Engine exhaust temperature 
${h}_{exh}$  Exhaust manifold inletspecific enthalpy 
$C{p}_{exh}$  Exhaust gas specific heat 
${\dot{m}}_{intk}$  Intake port air mass flow rate 
${\dot{m}}_{fuel}$  Fuel mass flow rate 
$${\dot{m}}_{exh}$$  Exhaust mass flow rate 
$${y}_{in,fuel}$$  Intake fuel mass fraction 
y_{exh,i}  Exhaust mass fraction for i = CO_{2}, CO, HC, NOx, air, burned gas, and PM 
$${\dot{m}}_{exh,i}$$  Exhaust mass flow rate for i = CO_{2}, CO, HC, NOx, air, burned gas, and PM 
T_{brake}  Engine brake torque 
N  Engine speed 
y_{exh,air}  Exhaust air mass fraction 
y_{exh,b}  Exhaust air burned mass fraction 
Power Accounting
For the power accounting, the block implements equations that depend on Torque model.
When you set Torque model to Simple Torque Lookup
, the block implements these equations.
Bus Signal  Description  Equations  



 Intake heat flow  ${\dot{m}}_{intk}{h}_{intk}$ 
PwrExhHeatFlw  Exhaust heat flow  ${\dot{m}}_{exh}{h}_{exh}$  
PwrCrkshft  Crankshaft power  ${T}_{brake}\omega $  
 PwrFuel  Fuel input power  ${\dot{m}}_{fuel}LHV$  
PwrLoss  All losses  ${T}_{brake}\omega {\dot{m}}_{fuel}LHV{\dot{m}}_{intk}{h}_{intk}+{\dot{m}}_{exh}{h}_{exh}$  
 Not used 
When you set Torque model to Torque Structure
, the block implements these equations.
Bus Signal  Description  Equations  



 Intake heat flow  ${\dot{m}}_{intk}{h}_{intk}$ 
PwrExhHeatFlw  Exhaust heat flow  ${\dot{m}}_{exh}{h}_{exh}$  
PwrCrkshft  Crankshaft power  ${T}_{brake}\omega $  
 PwrFuel  Fuel input power  ${\dot{m}}_{fuel}LHV$  
PwrFricLoss  Friction loss  ${T}_{fric}\omega $  
PwrPumpLoss  Pumping loss  ${T}_{pump}\omega $  
PwrHeatTrnsfrLoss  Heat transfer loss  ${T}_{brake}\omega {\dot{m}}_{fuel}LHV{\dot{m}}_{intk}{h}_{intk}+{\dot{m}}_{exh}{h}_{exh}+{T}_{fric}\omega +{T}_{pump}\omega $  
 Not used 
h_{exh}  Exhaust manifold inletspecific enthalpy 
h_{intk}  Intake port specific enthalpy 
${\dot{m}}_{intk}$  Intake port air mass flow rate 
${\dot{m}}_{fuel}$  Fuel mass flow rate 
$${\dot{m}}_{exh}$$  Exhaust mass flow rate 
ω  Engine speed 
T_{brake}  Brake torque 
T_{pump}  Engine pumping work offset to inner torque 
T_{fric}  Engine friction torque 
LHV  Fuel lower heating value 
Ports
Input
Output
Parameters
References
[1] Heywood, John B. Internal Combustion Engine Fundamentals. New York: McGrawHill, 1988.