Post Processing JLR PowertrainCFD using EnSight17th October 2006

Dr Steven PiersonPrincipal Technical Specialist

Agenda

Introduction. CFD software strategy. Case studies:

> Fuel slosh.> Intercooler.> Crankcase windage & ventilation.

Conclusions.

Introduction

PT (Powertrain) Analysis is a multidiscipline CAE group responsiblefor Jaguar Land Rover PT related analysis:

> Dynamics & durability.> Tribology & fuel systems.> Performance & sound quality.> CFD.

CFD is applied to a wide range of applications:> Base engine: In-cylinder, coolant systems, intake manifolds, etc.> PT installed: Air intake systems, catalysts, fuel tanks, etc.

JLR PowertrainCFD Code Strategy

Multiple solvers for optimum analysis capability:> Fluent, StarCD, MESIM (In-Cylinder).> RADIOSS (Fluid Structure Interaction).

Common pre & post processors to minimise complexity. EnSight predominantly used for advanced post processing:

> Interrogating transient data (flow, sprays & free surfaces).> Animations.> Path lines.> Multiple data sets.

Ease of use. Scripting utilised for semi/automatic post processing.

Case Study 1

Fuel Slosh Analysis - Background Fuel slosh has been identified as a potentialsource of customer annoyance.

Two potential mechanisms for noise generation:> Turbulence induced noise.> Bulk fuel impacting the tank surfaces (dominant source).

NVH vehicle test simulated using transient CFD (VOF). Body forces wereapplied to simulate a 0.25g deceleration from 25 kph.

Preventative action taken to minimise fuel slosh induced noise using tankbaffles.

EnSight used to interrogate data & create animations. Results presented are from the final design with and without tank baffles.

Fuel Tank SloshPressure Vs Time

99900

100100

100300

100500

100700

100900

0 1 2 3 4 5 6

Time (seconds)

Pres

sure

(N/m

2 )

Sensor 1Sensor 2

Sensor 1

Sensor 2

0.25 g deceleration Stopped

1.1 +/- 0.1

Seconds

Time (Seconds)

Accelerometer positions

SloshEvents

Acc

eler

atio

n m

/s2Case Study 1

Fuel Slosh Analysis - Correlation

1.1 S 1.2 S

Methodology developed using prototypevehicle test data.

Correlated qualitatively against moviesof a transparent tank and accelerometerdata.

The repetition rate from the measuredaccelerometer data and predictedpressure data show reasonablecorrelation.

No Baffles

Fuel does not reach equilibrium duringbreaking period.

Once the vehicle has stopped, the fuel sloshesfrom front to back and vice versa, rolling up thefront corners.

Baffled Tank

The fuel sloshes forward during thedeceleration period and quickly reaches anequilibrium position.

Likewise, once the vehicle has stopped thefuel sloshes backwards and the motion isquickly damped out.

Case Study 1

Fuel Slosh Analysis - Results

A correlated methodology for modelling fuel slosh has been developed.

> The results were consistent with clear tank observations & thepredicted and measured repetition rates showed good agreement.

Fuel slosh results have been presented on a tank both with and withoutbaffles in place.

Without baffles in place the fuel the fuel sloshes back to front and doesnot reach equilibrium during the breaking period. Once the vehicle hasstopped, the fuel sloshes from front to back and vice versa, rolling up thefront corners and impacting the front and upper surfaces.

Introducing baffles significantly reduces the degree of slosh present in thetank. The baffle reduces the fuel motion during both the deceleration andstationary periods, reducing the pressure loading seen on the tank frontand rear surfaces.

Case Study 1

Fuel Slosh Analysis - Conclusions

AJV8 uses water to air intercoolers tocool the high temperature and pressuresupercharger air:

> Increase air density and mass flow,and hence increase engine power.

Steady state & transient CFD used tooptimise the design:

> Minimal airside pressure drop.> Maximum airside cooling.> Minimal port-to-port temperaturevariation.

EnSight used to display multiple datasets and to interrogate transient data.

Results shown are from the final design.

Case Study 2 - AJV8 SuperchargedIntercooler Analysis - Background

300

310

320

330

340

350

Outlet 1 Outlet 2 Outlet 3 Outlet 4 Outlet 5 Outlet 6 Outlet 7 Outlet 8

Tem

per

atu

re (

K)

Measured

CFD (Transient)

CFD (Steady State)

Top tanks

Superchargerexit

Heat exchangercores

Case Study 2 - AJV8 SuperchargedIntercooler Analysis - Results

Steady state CFD is used to gaininsight into the flow behaviour.

Intercooler design is heavilypackage constrained.

Top tank shape optimised for flowuniformity:

> Minimise flow bias towardsrear of the brick.

> Eliminate charge air beingdrawn up the 1st two channels.

> Minimise contra-rotatingrecirculation regions on thebrick upper surface.

Case Study 2 - AJV8 SuperchargedIntercooler Analysis - Results

Transient CFD provides insightinto dynamic flow behaviour:

> Similarities in flow structurebetween steady state andtransient results.

> Charge robbing betweencylinders evident.

> Charge robbing betweenbanks also evident.

Transient CFD used to quantifyintercooler performance:

> Port to port temperaturevariation now dominated byfiring order and cam timing.

A combined approach using steady state and transient CFDanalysis has been adopted to optimise the AJV8 superchargerintercoolers:

> Steady state CFD provides insight into the flow structure.> Transient CFD is used to quantify the cooler performance.

Through careful shaping of the intercooler top tank the flowuniformity has been optimised within the package constraints.

Charge robbing between cylinders and across bank is now thedominant contributor to port to port temperature variation and canbe optimised through cam timing.

Case Study 2 - AJV8 SuperchargedIntercooler Analysis - Conclusions

Significant effort is spent optimising air intake systems, exhaustsystems, intake/exhaust ports and manifold to ensure good enginebreathing.

Comparatively little effort is spent optimising crankcasebreathing/ventilation and crank windage, although restricting crankcaseinterbay breathing can consume considerable power.

A practical methodology has been developed using CFD to simulatecrankcase breathing to:

> Predict crankcase ventilation (pumping) losses.> Predict crank windage losses.> Provide insight into the flow field to guide block/crank/windage traydesigns for reduced ventilation losses.

> Assess windage tray performance. EnSight utilised to interrogate transient data and create animations.

Case Study 3 Crankcase Ventilationand Windage - Background

-40

-20

0

20

40

0 0.01 0.02

Time (s)

Velo

cit

y (

m/s

)

SlidingBoundariesPistons - Time

dependent velocityboundaries

Rotating mesh

Crank nose -rotating wall

boundary

Front cover &drain backs -

Pressureboundaries

Case Study 3 CrankcaseVentilation Analysis

Modelling crankcasebreathing is a non trivialexercise comprisingcomplex geometry, meshmotion and transient twophase flows.

A practical approach wastherefore adopted:

> Oil mist representedas an active scalar.

> Blow-by and PCVgases are ignored.

Results presented are froman early prototype.

Crankcase gases forced through breatherholes and between the bulkhead and windagetray at high velocity (> 100 m/s).

Crank-weights restrict the flow through boththe breather holes and beneath the bulkheadfor c. 1/3rd engine cycle.

The lower breather holes are virtuallyblocked off by the crank weight.

Case Study 3 CrankcaseVentilation Analysis - Results

The scraper may provide greater pressure relief for the cylinderson A bank.

The angular flow momentum induced by the crank may restrictgas transfer from B to A bank.

Significant flow activity seen beneath the windage tray. Crankcase gases are forced under the windage tray via the scraper on ABank.

Case Study 3 CrankcaseVentilation Analysis - Results

A practical method has been developed to model crankcaseventilation and windage within programme timescales. Themethodology continues to be refined.

The method has been applied on new engine programmes toprovide insight and design direction.

Analysis of the engine confirmed ventilations losses to besignificant. The losses were compounded by the 8 weight crankrestricting flow through the breather holes and beneath thebulkhead.

Design modifications were implemented to reduce the ventilationlosses to an acceptable level.

Case Study 3 CrankcaseVentilation Analysis - Conclusions

EnSight supports JLR PTs multiple code CFD strategy.

EnSight is used for advanced post processing:

> Post processing multiple data sets at once.> Animations of transient flow analysis, sprays & free surfacemodelling.

> Ease of use.> Scripting utilised to auto-create animations & plots.

EnSight has been and continues to be applied to PT CFDapplications:

>