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Automobile Air Bag Inflation System Using Pressurized Carbon Dioxide Bart Adams New Jersey Institute of Technology

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Automobile Air Bag Inflation System Using Pressurized Carbon Dioxide Bart Adams New Jersey Institute of Technology New Jersey Institute of Technology Digital Commons @ NJIT Dissertations Theses and Dissertations Spring 1998 Automobile air bag inflation system using pressurized carbon dioxide Bart Adams New Jersey Institute of Technology Follow this and additional works at: https://digitalcommons.njit.edu/dissertations Part of the Mechanical Engineering Commons Recommended Citation Adams, Bart, "Automobile air bag inflation system using pressurized carbon dioxide" (1998). Dissertations. 939. https://digitalcommons.njit.edu/dissertations/939 This Dissertation is brought to you for free and open access by the Theses and Dissertations at Digital Commons @ NJIT. It has been accepted for inclusion in Dissertations by an authorized administrator of Digital Commons @ NJIT. For more information, please contact [email protected]. Cprht Wrnn & trtn h prht l f th Untd Stt (tl , Untd Stt Cd vrn th n f phtp r thr rprdtn f prhtd trl. Undr rtn ndtn pfd n th l, lbrr nd rhv r thrzd t frnh phtp r thr rprdtn. On f th pfd ndtn tht th phtp r rprdtn nt t b “d fr n prp thr thn prvt td, hlrhp, r rrh. If , r rt fr, r ltr , phtp r rprdtn fr prp n x f “fr tht r b lbl fr prht nfrnnt, h ntttn rrv th rht t rf t pt pn rdr f, n t jdnt, flfllnt f th rdr ld nvlv vltn f prht l. l t: h thr rtn th prht hl th r Inttt f hnl rrv th rht t dtrbt th th r drttn rntn nt: If d nt h t prnt th p, thn lt “ fr: frt p t: lt p n th prnt dl rn h n tn lbrr h rvd f th prnl nfrtn nd ll ntr fr th pprvl p nd brphl th f th nd drttn n rdr t prtt th dntt f I rdt nd flt. ASAC AUOMOIE AI AG IAIO SYSEM USIG ESSUIE CAO IOIE b rt Ad A novel air bag inflator based on the evaporation of liquefied carbon dioxide was developed. A detailed qualitative model was established on the basis of an extensive experimental study. An integrated quantitative model of this inflator was constructed. The system was studied by discharging the inflator into a tank and measuring pressure and temperature evolution (0-50 ms). The dispersion of the two-phase spray during inflation was investigated by high-speed cinematography. The optimal storage pressure of the liquid CO2 was found to be 2000 psig (at 22 °C). Two distinct inflator behaviors were identified. First, at conditions corresponding to an initial entropy below the critical point, a two-phase evaporating spray was ejected from the inflator into the tank. Second, at an initial entropy above the critical point, the inflation sequence constituted the expansion of a real gas without a significant phase transformation. The minimal flow section in the nozzle was found to control the dynamics of this new inflator. To prevent the formation of solid CO2 during inflation, small amounts of organic liquids were added to the inflator. A significant increase in tank temperature was observed, resulting in a profound improvement in performance. An explanation for the influence of organic liquids was developed based on a 'layered evaporation model'. The qualitative model was based on the interaction of the flashing process with the two-phase outflow from the inflator. This interaction was manifested in two different waves, namely a forerunner and an evaporation wave which controlled the evacuation of the two-phase mixture from the inflator. The latter was predominantly dispersed according to classical atomization mechanisms. The generated droplets evaporated partially by consuming their own internal energy and by interacting with tank gases. The characteristics of the condensate were evaluated by a detailed thermodynamic analysis. The quantitative description of the inflator involved the development of a transient one-dimensional, two-fluid model. Preliminary simulations show excellent agreement with the expected results. The tank model was formulated on the basis of an empirical correlation for the atomization process, coupled with a simple droplet evaporation model, followed by a model for the mixing of real gases. AUOMOIE AI AG IAIO SYSEM USIG ESSUIE CAO IOIE b rt Ad A rttn Sbttd t th lt f r Inttt f hnl n rtl lfllnt f th rnt fr th r f tr f hlph prtnt f Mhnl. Ennrn M 8 Copyright 0 1998 by Bart Adams ALL RIGHTS RESERVED AOA AGE AUOMOIE AI AG IAIO SYSEM USIG ESSUIE CAO IOIE rt Ad r. Mhd E. bb, rttn Advr rh rfr f Cvl nd Envrnntl Ennrn, r Inttt f hnl, r, r. n Y. Chn, Ctt Mbr t rfr f Mhnl Ennrn, r Inttt f hnl, r, r. l . lr, Ctt Mbr t At rfr f Mhnl Ennrn, r Inttt f hnl, r, r. lph nlr, Ctt Mbr t rtr f Ennrn hnl, rd hnl In., ntn, r. brt . Krhnr, Ctt Mbr t rfr f Mhnl Ennrn, r Inttt f hnl, r, IOGAICA SKEC Athr: rt Ad r: tr f hlph t: M 8 Undrrdt nd Grdt Edtn: • tr f hlph n Mhnl Ennrn, r Inttt f hnl, r, r, 8 • Mtr f Sn n Mhnl Ennrn, r Unvrt f rl, rl, l, 2 • hlr f Sn n EltrMhnl Ennrn, hnl Cll f th Ct f Antrp, Antrp, l, 8 Mjr: Mhnl Ennrn rnttn nd bltn: Ad ., hrdn nd tr f rtl rtn drn Expnn f d CO2Orn Slvnt Mxtr, rntd t th Unvrt f lr, n t th t Clld nd Srf Sn Sp v prnt, brthr nd tr nd Mrnn ACKNOWLEDGMENT I wish to express my sincere thanks to a few of those who assisted me during the course of this work (Spring '95-Spring '98). Most of all, I thank Dr. Mohamed E. Labib for giving me inspiration, guidance and words of encouragement. Also, thanks to Dr. Stanislav S. Dukhin for the hours of stimulating 'small' discussions and to my committee members, Dr. Rong Y. Chen, Dr. Pasquale J. Florio, Dr. Ralph Hensler and Dr. Robert P. Kirchner for their time and comments. I also thank Yacoob Tabani for his help and for starting out as a colleague and ending up as a good friend. The entire staff of Breed Technologies Inc., Boonton, NJ was extremely helpful in providing technical assistance. I would also like to acknowledge Breed Technologies Inc. for their financial support of my project. Furthermore, I thank Dr. R. Dave for allowing me to use the high-speed cinematographic equipment. And last, but certainly not least, I sincerely thank my parents and Marianne for supporting me during the last three years. vi AE O COES Chptr Page 1 INTRODUCTION I 1.1 Objective 1 1.2 General Information about Air Bags 1.2.1 Safety Aspects 3 1.2.2 Components of an Air Bag System 5 1.2.3 Types of Air Bag Systems 6 1.2.3.1 Driver Side Air Bag 8 1.2.3.2 Passenger Side Air Bag 8 1.2.3.3 Side Impact Air Bag 8 1.2.4 Quantifying the Performance of an Inflator 9 1.2.5 General Design Requirements of an Inflator 11 1.2.6 Current Inflator Technology 12 1.2.6.1 Pyrotechnic Inflator 12 1.2.6.2 Stored Gas Inflator 13 1.2.6.3 Hybrid or Augmented Gas Inflator 16 1.2.6.4 Combustible Gas Mixture Inflator 16 1.3 Novel Approach 17 1.3.1 Selection of the Working Fluid 19 1.3.2 General Properties of CO2 20 v AE O COES (Cntnd Chptr Page 1.3.3 Relevant Phenomena in the System 23 1.3.3.1 Phenomena in the Inflator Vessel 25 1.3.3.2 Phenomena in the Release Mechanism and the Nozzle.... 32 1.3.3.3 Phenomena in the Receiving Tank (or Air Bag) 33 1.4 Present Work 36 2 EXPERIMENTAL SET-UP AND PROCEDURES 38 2.1 Introduction 38 2.2 Main Experiments 40 2.2.1 Inflator Vessel 40 2.2.2 Release Mechanism and Nozzle 42 2.2.2.1 Release Mechanism 42 2.2.2.2 Nozzle 45 2.2.3 Receiving Tank 47 2.2.4 Pressure Transducers 48 2.2.5 Thermocouples 49 2.2.6 Data Acquisition System and Computer 50 2.2.7 Gas Booster Compressor 51 2.2.8 Gases 51 v AE O COES (Cntnd Chptr Page 2. rdr f Mn Exprnt 2 2.. Stndrd Exprntl rdr 2 2..2 rdr fr Exprnt t Intl n prtr 4 2.. rdr fr Exprnt t h Intl Infltr prtr 55 2..4 rdr fr CO2Orn d Exprnt 55 2.4 frn Exprnt 6 2. hSpd Cntrph Stp 6 2.. n I 64 2..2 t I 64 2.. zzl Ext I 66 IEA GAS EEIMES A AIAIO O E EOMACE O E MAI EEIMEA SEU 6 . Intrdtn 6 .2 Exprntl lt 68 . hrtl Mdl 75 .4 rfrn f th Mn Exprntl Stp 8 4 EEIMEA SUY O E SOE IQUEIE GAS IAO . 80 4. Intrdtn 80 4.2 Exprntl lt 84 x AE O COES (Cntnd Chptr Page 4.2.1 Influence of Initial Tank Conditions 84 4.2.1.1 Effect of Different Tank Gases 85 4.2.1.2 Effect of Increased Initial Tank Pressure 88 4.2.1.3 Effect of Decreased Initial Tank Temperature 92 4.2.2 Influence of Critical Flow Section 95 4.2.3 Influence of Initial Inflator Conditions 98 4.2.3.1 Effect of Initial Inflator Pressure 98 4.2.3.2 Effect of Initial Inflator Temperature 101 4.2.3.3 Effect of Initial Inflator Size 105 4.2.4 Results of the High-Speed Cinematography 106 4.2.4.1 Observations of the Tank Phenomena during the Main Experiments 107 4.2.4.2 External Spray Characteristics 110 4.2.4.3 Nozzle Exit Recordings 112 4.2.5 Influence of Small Amounts of Organic Liquids 113 4.2.5.1 Effect of Different Amounts of Methanol 114 4.2.5.2 Effect of Different Organic Liquids 116 4.3 Discussion 118 4.3.1 Qualitative Model of the Stored Liquefied Gas Inflator 118 AE O COES (Cntnd Chptr Page 4.3.1.1 Stage 1: Opening of the Release Mechanism and Initial Depressurization 120 4.3.1.2 Stage 2: Passage of the Forerunner and Initial Vapor Generation 121 4.3.1.3 Stage 3: Passage of the Evaporation Wave and Main hr 126 4.3.1.4 Stage 4: Final Discharge 130 4.3.1.5 Equilibration Stage 132 4.3.2 Influence of Initial Inflator Conditions 133 4.3.2.1 Effect of Initial Inflator Pressure 133 4.3.2.2 Effect of Initial Inflator Temperature 136 4.3.3 Influence of Critical Flow Section 140 4.3.4 Influence of Initial Tank Conditions 141 4.3.5 Qualitative Explanation of CO2/Organic Liquid Experiments 145 5 THEORETICAL MODELING ASPECTS 148 5.1 Introduction 148 5.2 Modeling the Behavior of CO2 149 5.2.1 Requirements of the CO2-Model 150 5.2.2 Alternative Models for the Non-Ideal Behavior of a Fluid 150 5.2.3 General Aspects of the CO2-Model 153 x AE O COES (Cntnd Chptr Page 5.2.3.1 Isobaric Specific Heat Capacity, Ideal Gas Enthalpy, Ideal
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