Application of GT-POWER to Model Failed Parts for On-Board DiagnosticsRohan Gumaste

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Contents

Introduction and MotivationProcess Flow Chart Simulation Process OverviewFRM (Fast Running Model) OverviewClosed Loop Simulations and ResultsSummary

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Introduction : On-Board Diagnostics (OBD)

Systems and algorithms to detect failures which adversely affect emissions

A continuous emissions “test” being conducted by the Engine Control Module (ECM)

Includes Flow Monitor, a model based diagnostics designed to detect various flow system errors (charge flow and EGR flow)

What are On-Board Diagnostics (OBD)?

Purpose:• Identify & isolate hardware issues

that could impact emissions• Alert operators of these issues

• An OBD failed part is a component added to an engine which represent a failure mode.

• An OBD failed parts should be sized such that OBD algorithm set the Fault before emission levels are exceeded.

What is an “OBD failed part”?

Restriction orifice

example : clogged EGR valve

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Motivation: Typical Way OBD Failed Parts Are Sized

Install part which represents OBD

failure mode

Run engine over FTP (Federal Test Procedure) and SET (Supplemental Emissions Test) Cycles

Remove Failed Part

Restore baseline engine

performance

Detection of fault

successful?

Yes

No

Use different size of failed part

Testing needs to be done again : - Change in engine hardware - Change in engine calibration- To check robustness $$

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Objective

Motivation : Develop process to demonstrate

OBD failure using simulation Develop simulation process on

how to size OBD failed Parts for selected errors

Cost-effectively evaluate ECM calibrations by complimenting/reducing engine testing

Improve system robustness to noise-factors

Pure Simulation Model

Engine performance model in GT-POWER coupled to Controls and Systems model in Simulink is used.

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Process Flow Chart

Steady state data, DGM, transient data

Controls Simulink Model

Inputs OutputsCalibrated FRM with

NOx model

Closed loop model

Recommendations for OBD failed part sizes

and engine testing

Start of simulation process

1. Steady state and transient calibration of FRM (open loop)

2. Validation of FRM predictions in closed loop

3. Add parts in FRM which represent OBD failure mode

4. Do simulations for sweep on OBD failed parts

End of simulation process

Details of OBD Failure Modes

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Simulation Process Overview

Actuator values from test data (open loop)

FRM

Engine speed, air handling actuator values and fueling commands, etc.

OBD Flow Monitor (Virtual Sensor)

Pressures, temperatures, flow rates, turbo speed, etc.

OBD Fault DetectionControls model (closed loop)

or

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Introduction : FRM (Fast Running Model)

Convert Detailed GT-POWER Model to FRM (Fast Running Model) by combining flow volumes

Tune friction multiplier and expansion diameter of flow-split to match pressure drop in the system

Tune heat transfer multiplier to match heat transfer and temperatures in the system

Use “FRM Converter” wizard within GT-POWER -> Tools

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Comparison : FRM prediction and test data for steady state points

• Make sure that steady state points selected for FRM calibration cover all operating region of the engine.

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NOx Model within GT-POWER Model

• NOx model within GT-POWER requires predictive combustion model (Di-Pulse is used).• Advanced Direct Optimizer (ADO) is used to calibrate tuning parameter values.

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NOx Model Prediction Comparison

Steady State Points Comparison over HD-FTP Cycle (open loop)

After FRM calibration, NOx model prediction is compared against test data for steady state points and over transient cycle.

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Closed Loop Model

FRM

Controls Model Comparison of air flow prediction and test data over HD-FTP cycle

Controls model in Simulink is coupled to engine performance model in GT-POWER

Time (s)

0 200 400 600 800 1000 12000

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45AirFlow

Test Cell

Simulation

Similar comparison is made for other engine performance parameters for validation of closed loop model.

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Process Flow Chart

Steady state data, DGM, transient data

Controls Simulink Model

Inputs Outputs

Calibrated FRM with NOx model

Closed loop model

Recommendations for OBD failed part sizes

and engine testing

Start of simulation process

1. Steady state and transient calibration of FRM (open loop)

2. Validation of FRM predictions in closed loop

3. Add parts in FRM which represent OBD failure mode

4. Do simulations for sweep on OBD failed parts

End of simulation process

Added orifice in EGR loop in FRM for “EGR Flow Low”

error

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Closed Loop Simulation Results

Closed loop simulation results for “EGR Flow Low” OBD error

Different NOx levels for different failed part sizes

Restriction orifice

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Closed Loop Simulation Results

Instantaneous error = ECM estimated flow rate – GT-POWER flow rate

Fault is set Threshold

Instantaneous OBD Error

Integrated OBD Error

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OBD Failure Modes OBD failure modes which can be easily represented in GT-POWER :

Degradation in turbo performance

Failure in CAC and EGR cooler

Leaks in intake and exhaust manifold

Failure in sensors for pressure, temperature and turbo speed

Failure in actuation of intake throttle, EGR valve, VGT

Restriction in air flow paths

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Summary – Concluding thoughts

Closed loop simulations can be used to size OBD failed parts and reduce engine testing.

Other applications: Closed loop simulations can be used for “OBD Fault Isolation” analysis. Virtual field tests can be performed and help in predicting scenarios for different

component failures and mechanical limit violations and hence, can help in avoiding down-time for parts replacement during actual engine testing. This simulation approach can be extended to after-treatment component failure

modes by adding an after-treatment model in the simulation.

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Thank You!!

Question??