C&R TECHNOLOGIES

C&R TECHNOLOGIES303.971.0292

Fax 303.971.0035www.crtech.com

Modeling IC Enginesand

Turbochargers

Using SINDA/FLUINT and Sinaps®

Sinaps, C&R Thermal Desktop, RadCAD and FloCADare registered trademarks of C&R Technologies.

SpaceClaim is a registered trademark of SpaceClaim Corporation.

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Overview

Detailed (high temporal fidelity) IC Engine Model Inline 6 cylinder, atmospherically aspirated Seeking temperature/pressure/flow histories over a cam cycle as a

function of RPM Turbocharged IC Engine Model

Add compressor, turbine, intercooler, waste gate, pop-off valve Modify intake and exhaust Seeking:

Parametric sweeps, including TC speed vs. Engine speed Fast Transient: TC performance over a cam cycle (pressure waves) Slow Transient: Engine speed variations (boost lag, valve responses)

Full documentation and models are available at www.crtech.com

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Wave Propagation

SINDA/FLUINT is a finite difference, finite volume solver, not a method of characterisics (MOC) solver Can handle much more complex phenomena than

can MOC The solution is implicit: can take large time steps.

So time steps must be constrained to capture wave motions

Waves appear, even though they aren’t explicitly modeled

Coarse axial resolution is OK for demonstration and preliminary design* Easy to increase resolution at any time

Can choose to neglect high-frequency terms at any point in the fluid network Can opt instead for quasi-steady solutions for

faster run times

* For liquid systems, low resolution is tolerable even for detailed design work.

100mm long by 10mm diameter dead-endtube with sinusoidal and step function excitations

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Sample Engine Specs.

4-cycle inline 6 cylinder, with SOHC 3.7L displacement 9:1 compression ratio (CR) Firing sequence: 1, 5, 3, 6, 2, 4 Fixed valve lift profile

Easy to vary if needed

Intake and Exhaust Intake manifold

85x110x210 mm box, with 500mm long by 45mm diameter runners, with notional air filter losses

Exhaust manifold blended runners, 356mm long by 41.3mm diameter,

with a 305mm long 6-1 transition section

Exhaust pipe 3.05m long by 57.2mm diameter with notional muffler

and catalytic converter losses

Intake valve lift profile from 0 TDC

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Simplifying Assumptions

Simplified Combustion Event Cylinder was a boundary condition, not a focus of the model Instant heating by 2200K over intake manifold temperature at 0 TDC

Cylinder Heat Transfer Convective and radiative heat transfer used, adjusted to yield roughly 1/3rd total loss to engine

block Piston Motion

Pure sinusoid was used Could easily apply more realistic motion given crank and rod lengths

Valve Flow Resistance Sharp annular gap assumed, modeled as an effective orifice Verified that within-cylinder axial fluid motions (e.g., knocking) could be neglected for this

model: the cylinder could be a single control volume Engine RPM

Prescribed as an input: no vehicle/load model used Manifolds

Coarse axial resolutions (L/D ~ 5) were used, with few additional irrecoverable losses. These could be easily modified based on an actual design.

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PostprocessedSinaps Network

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Parametrically Defined

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Sample ResultsCylinder Temps at 4000RPM

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Sample Results:Pressures and Flows at 6000RPM, Cylinder

#1

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Next Model:Turbocharged

Intake Modifications 150mm long by 50mm diameter intake runners 610mm long by 100mm diameter pipe as manifold

Waste Gate Details of servo line, dynamic stem motions etc. could have been included, but

were neglected since this is not the focus Proportional control valve, open at 2.2 bar (intake manifold), closed at 2.0 bar

Proportional control (vs. bang-bang) used for convenience: allows steady state solutions

Pop-off Valve Proportional control valve, open at 2.4 bar, closed at 2.2 bar

Intercooler Notional/place-holder, despite heat exchangers being a forté: this was not the

focus Achieved minimal cooling, had minimal flow resistance

5 Compressors and 6 Turbines were evaluated CompAero and TurbAero software (www.turb-aero.com) employed

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Compressor

Design Point: 70000 RPM Pratio = 2.5 4000 RPM engine

0.245 kg/s

25°C, 86kPa inlet (total)

Design Summary: Centrifugal with basic

volute-type outlet, 49mm inlet diameter

Vaneless vaned compressors

were also evaluated

72% efficiency (T-T)

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Turbine

Design Point: 70000 RPM Pratio = 2.61 (T-S) 4000 RPM engine

0.245 kg/s

695K, 324kPa inlet (total) 124kPa exit (static) 110% of est. power required

by compressor Design Summary:

Radial, 94mm blade tip diameter

Vaneless vaned compressors were also

evaluated

82% efficiency (T-S)

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Turbocharger Dynamics

Rotational inertia (I) of whole turbocharger subsystem was estimated to be 7.68e-3 kg-m2

Notional friction (f) as a function of RPM Current net torque (Tnet) used to co-solve

1st order ODE:Tnet – f*w = I*dw/dt

Can also use in a sizing mode parametrically sweep w to find the balance point (zero net

torque)

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System Network:Detailed Model

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Sample Results Pressures at 3000RPM, Cylinder #1

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System Network:Simplified Model

Replace engine with steady-flow, steady heating model based on averages of

detailed model as a function of RPM

Change focus from small to large time scale including steady state

Used to generate TC speed at balance point For use as an initial

condition in detailed model

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Sample Results:Parametric Sweeps

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Sample Results:Engine Transient

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Sample Results:Engine Transient

Compressor surges

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Geometry (CAD/FDM/FEM) Model Development

Sinaps® is nongeometric SINDA/FLUINT models can be

created from CAD geometry too use any combination of:

lumped parameter (network) finite difference finite element

C&R Thermal Desktop®

FloCAD for fluid modeling Includes turbomachinery,

rotating passages (secondary flows)

RadCAD for radiation

CRTech SpaceClaim®

CAD import or generation healing, defeaturing, meshing

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Conclusions

CRTech tools are applicable to: IC engine fuel/air system design studies Turbocharger design (including IC engine interactions)

at both short and long time scales

Basic models are available as starting points Possible Extensions

Exhaust Gas Recirculation (EGR) integration Waste gate control systems and detailed design Variable geometry turbines (VGT) Multiple turbochargers (parallel or series) In-system turbine and compressor design optimization

Requires development cooperation with meanline analysis software