Internal Combustion Mapped and Dynamic Engine Models. When you customize a SI or CI reference application, you can use either a dynamic or mapped engine model. The table provides considerations for using either implementation. It is targeted that the students will be able to build/modify/use a simple crank-angle resolved model of a single cylinder IC engine (written in Matlab), a dynamic mean value model (written in Simulink), as well as use a modern multi-cylinder engine simulation software package (GT-Power).
DescriptionThe Generic Engine block represents a general internalcombustion engine. Engine types include spark-ignition and diesel. Speed-power andspeed-torque parameterizations are provided.
A throttle physical signal input specifiesthe normalized engine torque. Optional dynamic parameters include crankshaft inertia andresponse time lag. A physical signal port outputs engine fuel consumption rate based onchoice of fuel consumption model. Optional speed and redline controllers prevent enginestall and enable cruise control. Engine Speed, Throttle, Power, and TorqueThe engine model is specified by an engine power demandfunction g(Ω). The function provides the maximum power availablefor a given engine speed Ω. The block parameters (maximum power, speed at maximumpower, and maximum speed) normalize this function to physical maximum torque andspeed values.The normalized throttle input signal T specifies the actualengine power.
![Simulink Combustion Engine Model Simulink Combustion Engine Model](/uploads/1/2/5/4/125499613/865100265.png)
The power is delivered as a fraction of the maximum power possible ina steady state at a fixed engine speed. It modulates the actual power delivered,P, from the engine:P( Ω, T) =T g( Ω). The enginetorque is τ =P/ Ω. Engine Power DemandThe engine power is nonzero when the speed is limited to the operating range, Ω min ≤Ω ≤Ω max. The absolute maximum engine powerP max definesΩ 0 such that P max =g( Ω 0). Define w ≡Ω/ Ω 0 and g( Ω) ≡P max p( w). Then p(1) = 1 and dp(1)/ dw = 0.
The torque function is:τ =( P max/ Ω 0) p( w)/ w.You can derive forms for p( w) from enginedata and models. Generic Engine uses a third-order polynomial form:p( w) =p 1 w+p 2 w 2–p 3 w 3satisfyingp 1 +p 2 –p 3 = 1,p 1 +2 p 2 –3 p 3 = 0.In typical engines, the p i are positive.This polynomial has three zeros, one at w = 0, and a conjugate pair.
![Simulink Simulink](http://pubs.sciepub.com/ajme/2/7/12/image/fig4.png)
One of the pair is positive and physical;the other is negative and unphysical.Π — Engine throttle.Π i — Input throttle (portT).Π c — Controllerthrottle.ω — Engine speed.ω r — Idle speedreference.ω t — Controller speedthreshold.τ — Controller time constantThe controlled throttle increases with a first-order lag from zero to one whenengine speed falls below the reference speed. When the engine speed rises above thereference speed, the controlled throttle decreases from one to zero. When thedifference between engine velocity and reference speed is smaller than thecontroller speed threshold, the tanh function smooths the timederivative of the controlled throttle. The controlled throttle is limited to therange 0–1.
The engine uses the larger of the input and controlled throttle values.If engine time lag is included, the controller changes the inputbefore the lag is computed. PerformanceTo increase simulation speed, use the default option, No fuelconsumption, for the Fuel consumption modelparameter.If you select any other option for the Fuel consumptionmodel, the block solves a nonlinear equation that is required forcalculating fuel consumption. The block solves the equation even if theFC port, which reports the fuel consumption rate, is notconnected to another block.When the parameter is set to No fuel consumption, theblock does not calculate fuel consumption, even if the FC portis connected to another block. PortDescriptionBRotational conserving port representing the engine blockFRotational Conserving port representing the engine crankshaftTPhysical signal input port specifying the normalized engine throttlelevelPPhysical signal output port reporting the instantaneous engine power,in WFCPhysical signal output port reporting the fuel consumption rate, inkg/sPort T accepts a signal with values in the range 0–1. The signalspecifies the engine torque as a fraction of the maximum torque possible in steady stateat fixed engine speed.
The signal saturates at zero and one. Values below zero areinterpreted as zero. Values above one are interpreted as one.Port FC does not output data when the Fuel consumptionmodel parameter is set to No fuelconsumption.Normalized 3rd-order polynomial matched topeak power — Parametrize the enginewith a power function controlled by power and speedcharacteristics. This is the default option.Tabulated torque data —Engine is parametrized by speed–torque table that youspecify.Tabulated power data —Engine is parametrized by speed–power table that youspecify.Engine typeChoose type of internal combustion engine.
Choose betweenSpark-ignition, the default option, andDiesel.Selecting Normalized 3rd-order polynomial matched to peakpower for the Modelparameterization parameter exposes this parameter.For more information, see the table. Maximum powerMaximum power P max that theengine can output. The default is 150 kW.Selecting Normalized 3rd-order polynomial matched to peakpower for the Modelparameterization parameter exposes this parameter.For more information, see the table. Speed at maximum powerEngine speed Ω 0 at which theengine is running at maximum power.
The default is4500 rpm.Selecting Normalized 3rd-order polynomial matched to peakpower for the Modelparameterization parameter exposes this parameter.For more information, see the table. Maximum speedMaximum speed Ω max at whichthe engine can generate torque. The default is 6000 rpm.During simulation, if Ω exceeds this maximum, thesimulation stops with an error.
The engine maximum speedΩ max cannot exceed theengine speed at which the engine power becomes negative.Selecting Normalized 3rd-order polynomial matched to peakpower for the Modelparameterization parameter exposes this parameter.For more information, see the table. Stall speedMinimum speed Ω min at whichthe engine can generate torque. The default is 500 rpm.During simulation, if Ω falls below this minimum,the engine torque is blended to zero.Selecting Normalized 3rd-order polynomial matched to peakpower for the Modelparameterization parameter exposes this parameter.For more information, see the table. Speed vectorVector of values of the engine function's independent variable, thespeed Ω.
The default is 500, 1000, 2000, 3000, 4000, 5000,6000, 7000 rpm.The first and last speeds in the vector are interpreted as the stallspeed and the maximum speed, respectively. If the speed falls below thestall speed, engine torque is blended to zero.
If the speed exceeds themaximum speed, the simulation stops with an error.Selecting Tabulated torque data orTabulated power data for theModel parameterization parameter exposes thisparameter.For more information, see the table. Torque vectorVector of values of the engine function's dependent variable, thetorque τ. The default is 380, 380, 380,380, 350, 280, 200, 80 N.m.Selecting Tabulated torque data for theModel parameterization parameter exposes thisparameter.For more information, see the table.
Power vectorVector of values of the engine function's dependent variable, thepower P. The default is 20, 40, 78, 120,145, 148, 125, 60 kW.Selecting Tabulated power data for theModel parameterization parameter exposes thisparameter.For more information, see the table. Interpolation methodMethod to interpolate the engine speed–torque or speed–power functionbetween discrete relative velocity values within the range ofdefinition. Choose between Linear, thedefault choice, and Smooth.Selecting Tabulated torque data orTabulated power data for theModel parameterization parameter exposes thisparameter.For more information, see the table.No inertia — Enginecrankshaft is modeled with no inertia.
This option is thedefault.Specify inertia and initialvelocity — Engine crankshaft is modeledwith rotational inertia and initial angular velocity.Engine InertiaRotational inertia of the engine crankshaft. The default is1 kg.m^2.Selecting Specify inertia and initialvelocity for the Inertiaparameter exposes this parameter.For more information, see the table. Initial velocityInitial angular velocity Ω(0) of the engine crankshaft. The default is800 rpm.Selecting Specify inertia and initialvelocity for the Inertiaparameter exposes this parameter.For more information, see the table. Time constantSelect how to model the time lag of the engine response. Choosebetween these options, each of which exposes other options.No lag — Suitable for HILsimulation — Engine reacts with no timelag.
This option is the default.Specify time constant and initialvalue — Engine reacts with a time lag.Selecting Specify time constant and initialvalue exposes other parameters.For more information, see the table.Engine time constantEngine time lag. The default is 0.2 s.Selecting Specify time constant and initialvalue for the Time constantparameter exposes this parameter.For more information, see the table. Initial normalized throttleInitial normalized engine throttle T(0), rangingbetween zero and one. The default is 0.Selecting Specify time constant and initialvalue for the Time constantparameter exposes this parameter.For more information, see the table.No fuel consumption —The default option.Constant per revolution.Fuel consumption by speed andtorque.Brake specific fuel consumption by speed andtorque.Brake specific fuel consumption by speed andbrake mean effective pressureSome options expose other parameters.
For more information, see thetable. No fuel consumptionThe block does not calculate fuel consumption even when theFC port, which reports the fuel consumptionrate, is connected to another block. Selecting this option increasessimulation speed. Fuel consumption per revolutionEnter the volume of fuel consumed in one crankshaft revolution.
Thedefault is 25 mg/rev.Selecting Constant per revolution for theFuel consumption model parameter exposes thisparameter.For more information, see the table. Displaced volumeEnter the volume displaced by a piston stroke. The default is400 cm^3.Selecting Brake specific fuel consumption by speed andbrake mean effective pressure for the Fuelconsumption model parameter exposes thisparameter.For more information, see the table. Revolutions per cycleEnter the number of crankshaft revolutions in one combustion cycle— e.g. 2 for a four-stroke engine, or1 for a two-stroke engine.
The default is2.Selecting Brake specific fuel consumption by speed andbrake mean effective pressure for the Fuelconsumption model parameter exposes thisparameter.For more information, see the table. Speed vectorEnter vector of engine speeds used in lookup table parameterizations.Vector size must match Torque vector size.
Thedefault is 1000, 2000, 3000, 4000, 5000, 6000 rpm. Selecting Fuel consumptionby speed and torque, Brake specific fuelconsumption by speed and torque, or Brakespecific fuel consumption by speed and brake mean effectivepressure for the Fuel consumptionmodel parameter exposes this parameter.For more information, see the table.
Torque vectorEnter vector of engine torques used in the lookup tableparameterizations. Vector size must match Speedvector size.
The default is 0, 80, 160, 200,240, 320, 360, 400 N.m. Selecting Fuel consumptionby speed and torque or Brake specificfuel consumption by speed and torque for theFuel consumption model parameter exposes thisparameter.For more information, see the table. Fuel consumption tableEnter matrix with fuel consumption rates corresponding to engine speedand torque vectors. The number of rows must equal the number of elementsin the Speed vector.
The number of columns mustequal the number of elements in the Torque vector.The default is.5,.9, 1.4, 1.6, 1.9, 2.7, 3.4, 4.4; 1, 1.7,2.7, 3.1, 3.6, 5, 6, 7.4; 1.4, 2.7, 4, 4.8, 5.6, 7.5, 8.5, 10.5; 2,3.6, 5.8, 6.7, 8, 10.4, 11.7, 13.3; 2.5, 4.8, 7.9, 9.4, 10.8, 14,16.2, 18.6; 3.1, 6, 10.3, 11.9, 13.8, 18.4, 22, 26.5 g/s.Selecting Fuel consumption by speed andtorque for the Fuel consumptionmodel parameter exposes this parameter.For more information, see the table. Brake mean effective pressure vectorEnter vector of brake mean effective pressure (BMEP) values. Thedefault is 0, 250, 500, 625, 750, 1000, 1150, 1250 kPa. The BMEP satisfies the expression.T — Output torque.n c — Numberof cycles per revolution.V d — Cylinderdisplaced volumeSelecting Brake specific fuel consumption by speed andbrake mean effective pressure for the Fuelconsumption model parameter exposes thisparameter.For more information, see the table. Brake specific fuel consumption tableSelecting Brake specific fuel consumption by speed andtorque or Brake specific fuel consumptionby speed and brake mean effective pressure for theFuel consumption model parameter exposes thisparameter.For more information, see the table.For the Brake specific fuel consumption by speed andtorque fuel model, enter the matrix with brakespecific fuel consumption (BSFC) rates corresponding to engine speed andtorque vectors. BSFC is the ratio of the fuel consumption rate to theoutput power. The number of rows must equal the number of elements inthe Speed vector.
The number of columns must equalthe number of elements in the Torque vector.For the Brake specific fuel consumption by speed andbrake mean effective pressure fuel model, enter thematrix with brake specific fuel consumption (BSFC) rates correspondingto engine speed and brake mean effective pressure (BMEP) vectors. BSFCis the ratio of the fuel consumption rate to the output power. Thenumber of rows must equal the number of elements in the Speedvector. The number of columns must equal the number ofelements in the Brake mean effective pressurevector.For both fuel-consumption models, the default is 410, 380,300, 280, 270, 290, 320, 380; 410, 370, 290, 270, 260, 270, 285,320; 415, 380, 290, 275, 265, 270, 270, 300; 420, 390, 310, 290,285, 280, 280, 285; 430, 410, 340, 320, 310, 300, 310, 320; 450,430, 370, 340, 330, 330, 350, 380 g/hr/kW.
Interpolation methodSelect the interpolation method used to calculate fuel consumption atintermediate speed-torque values. Methods areLinear andSmooth.
Outside the data range, fuelconsumption is held constant at the last value given in the lookuptable. Selecting Fuel consumption by speed andtorque, Brake specific fuel consumptionby speed and torque, or Brake specificfuel consumption by speed and brake mean effectivepressure for the Fuel consumptionmodel parameter exposes this parameter.For more information, see the table.Off — Omit idle speedcontroller. Throttle input is used directly. This option is thedefault.On — Include idle speedcontroller to prevent engine stalling. This option exposes otherparameters. For more information, see.Idle speed referenceEnter the value of the speed reference below which speed increases,and above which speed decreases. The default is 1000 rpm.Selecting On for the Idle speedcontrol parameter exposes this parameter.For more information, see the table.
Controller time constantEnter the value of the time constant associated with an increase ordecrease of the controlled throttle. The constant value must bepositive. The default is 1 s.Selecting On for the Idle speedcontrol parameter exposes this parameter.For more information, see the table. Controller threshold speedParameter used to smooth the controlled throttle value when theengine’s rotational speed crosses the idle speed reference.
For moreinformation, see. Largevalues decrease controller responsiveness. Small values increasecomputational cost. This parameter must be positive.
The default is1 rpm.Selecting On for the Idle speedcontrol parameter exposes this parameter.For more information, see the table. Redline controlSelect redline control model.
Options includeOff andOn.Off — Omit redlinecontroller. Throttle depends only on the idle speed controller.This option is the default.On — Include redlinecontroller to prevent excessive speed. This option exposes otherparameters.For more information, see the table.Redline speedEnter the value of the speed reference above which the redline controlactivates. The default is 5000 rpm.Selecting On for the Redlinecontrol parameter exposes this parameter.For more information, see the table.
Redline time constantEnter the value of the time constant associated with an increase ordecrease of the controlled throttle. The constant value must bepositive. The default is 1 s.Selecting On for the Redlinecontrol parameter exposes this parameter.For more information, see the table. Redline threshold speedSpecify the width of the region around the redline speed where thecontroller goes from fully enabled to not enabled. The block uses thisparameter for smoothing the controlled throttle value when the engine’srotational speed crosses the redline speed reference. Large valuesdecrease controller responsiveness.
Small values increase computationalcost. This parameter must be positive. The default is1 rpm.Selecting On for the Redlinecontrol parameter exposes this parameter.For more information, see the table.