Quantitative Evaluation of Aspirating Airbag Inflators

1

• Quantitative Evaluation of Aspirating Airbag
  Inflators
• Department of Mechanical Engineering
• P. B. Butler and L. D. Chen
• Principal Investigators
• The University of Iowa
• Iowa City, IA

2
Statement of Work

• Cold-Flow Sub-scale Model
• Flow Visualization
• Entrainment Measurements
• Hot-Firing Experiments
• Entrainment Measurements
• Canister Measurements
• High-Speed Imaging
• Parametric Investigations
• Occupant Position
• Break-Out Pressure
• Canister Design Parameters

3
Statement of Work

• Modeling
• CFD
• Inflator Jet Structure
• Canister Interior Flow
• Entrainment Predictions
• Design Optimizations
• ISP
• Lumped Parameter Modeling
• Construction of Entrainment Sub-Model for Use in
  Crash Simulation Codes
• Input from Above Items
• ISP
• Dyna3D?

4
Cold-Flow Summary
Visualization area
Particle visualization flow entrainment
streaklines
Smoke visualization flow entrainment
5
Hot-Firing Objectives

• Measurement of Aspiration Mass-Flow Rate
• Limits of Aspiration
• No airbag
• Closed canister
• Canister Pressure History
• Measurement of Aspiration Mass-Flow Rate for
  Various Degrees of Deployment
• Various Occupant Position
• In Progress

6
Hot-Firing Mass-Flow Measurement
Hot-Film Sensor
To Computer
Entrained Air
Mass-flow Measurement
7
Hot-Firing Results
8
Hot-Firing Summary

• Entrainment Mass Measurements
• Standard Unit
• Gross Inflow 29.0 grams
• Net Inflow 12.2 grams
• Without Airbag
• Gross Inflow 573 grams
• Net Inflow 573 grams
• Various Levels of Deployment
• in progress

9
Modeling Inflator Mass-Flow Rate

• Input Pressure (D. Tung, Delphi IL)

• ISP Code (J.Kang J.-T.Wang, 1998)
• Average Temperature Method

10
Modeling Nozzle Exit Temperature (K)

• Gasification 36
• Prop. Mass 440.5 (g) ? 15(g)
• Predicted by ISP Code with Delphi Data

11
Modeling Boundaries Mass-Flow Rate
At Nozzle Inlet P 12.4 (MPa), T 500 (K)
12
Modeling Entrainment
13
Modeling Jet Entrainment
At Nozzle Inlet P 12.4 (MPa), T 500 (K)
14
Modeling Jet Transient Properties
P 12.4 (MPa), T 500 (K)
Time 1 ms
Time 1 ms
Time 1 ms
Time 1 ms
Steady Solution
Mach Number
Static Pressure (Re-Scaled to 80 101 kPa)
15
Modeling Mass-Flow Validation
Coefficient of Momentum Resistance
Porosity
16
Modeling Mass-Flow Validation
Time Dependent Pressure Boundary Values
Calculated Velocity
17
CFD Simulation Summary-to-date

• Prediction of
• Nozzle Exit Temperature
• Inflator Discharge Rate

• Mass Entrainment
• As a Function of Inflator Pressure
• Low Pressure Region Inside of Domain
• Pipe Flow
• Validation of Hot-Firing Measurements
• Air-Mass Entrained into Airbag-Canister

18
Statement of Work - Summary

• Cold-Flow Sub-scale Model
• Flow Visualization
• Entrainment Measurements
• Hot-Firing Experiments
• Entrainment Measurements
• Canister Measurements
• High-Speed Imaging
• Parametric Investigations
• Occupant Position
• Break-Out Pressure
• Canister Design Parameters

19
Statement of Work - Summary

• Modeling
• CFD
• Inflator Jet Structure
• Canister Interior Flow
• Entrainment Predictions
• Design Optimizations
• ISP
• Lumped Parameter Modeling
• Construction of Entrainment Sub-Model for Use in
  Crash Simulation Codes
• Input from Above Items
• ISP
• Dyna3D?