碳基材料氧化烧蚀的快/慢反应动力学问题
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摘要
在前期单/双平台问题研究的基础上~([1]),就学术上和工程应用中关注的碳在空气中燃烧的"快反应"和"慢反应"问题进行了深入分析,研究发现被广泛使用50余年的"慢反应"并不存在,而被弃置的"快反应"则真实存在,且具有重要的应用价值。采用"快反应"动力学数据,同时考虑CO、CO_2两个烧蚀产物,得到的无量纲烧蚀速率随温度的变化曲线存在两个平台,其中,温度稍低情况下出现的第一平台对应的主要烧蚀产物为CO_2,温度稍高情况下出现的第二平台对应的主要烧蚀产物为CO,且第一平台对应的无量纲烧蚀速率恰好是第二平台的1/2。过去常被忽略的CO_2扮演了重要角色,由它产生的第一平台,将以往文献中看似完全独立、毫无关系的"快反应"和"慢反应"曲线建立了联系。理论分析表明:第一平台之前的快速上升段属于从速率控制区到扩散控制区的过渡区,第一平台及其以后的区域都属于扩散控制区(包括两个平台之间的连接线),它是由反应生成物CO与CO_2的分压比δ从0到∞的变化引起的,与表面化学反应动力学条件完全无关。由"双平台"理论得到的从低温到高温、由速率控制区经由过渡区到达扩散控制区的整条烧蚀速率曲线,与实验结果完全吻合。
Based upon our previous research on the single/dual platforms theory for carbonbased material oxidation,it has been found that the generally accepted "slow"reaction model which was presented by Scala in 1962 and has been widely used till now for over fifty years does not exist,while the deserted "fast"reaction model really exists and is of great value in application.Theoretical analysis shows that the "slow"reaction appears only at the boundarylayer-diffusion-rate controlled regime,In this regime,the ablation rate has no business with the chemical reaction rates,so it is a fictitious reaction model and has no physical meanings,although the results from it may be in agreement well with test results.The products of the heterogeneous reactions of carbon with oxygen are CO and CO_2,but CO_2 is usually neglected when the surface temperature is higher than 1000 Kin many literatures.However,from theoretical analysis,author find that CO_2 plays an important role in spanning the reaction range from the reaction-rate controlled regime to the diffusion controlled oxidation regime,and can't be ignored.It has been shown that for the ablation of carbon-based materials in a high speed stream of dissociated air,the"fast"reaction must be used with both products of CO_2 and CO at the same time.There are two different platforms in the diffusion controlled regime.The first platform results from reactions of the predominant CO_2 product,and the other is due to the predominant CO product reactions.With the increases of the surface temperature,the ratio of the mass fraction of CO to CO_2 at the surface rises rapidly from zero to infinity,which causes the oxidation process to change automatically from the nominated "fast"reaction to the so called "slow"reaction lines.The dual platform theory has been confirmed by several experimental results.
Based upon our previous research on the single/dual platforms theory for carbonbased material oxidation,it has been found that the generally accepted "slow"reaction model which was presented by Scala in 1962 and has been widely used till now for over fifty years does not exist,while the deserted "fast"reaction model really exists and is of great value in application.Theoretical analysis shows that the "slow"reaction appears only at the boundarylayer-diffusion-rate controlled regime,In this regime,the ablation rate has no business with the chemical reaction rates,so it is a fictitious reaction model and has no physical meanings,although the results from it may be in agreement well with test results.The products of the heterogeneous reactions of carbon with oxygen are CO and CO_2,but CO_2 is usually neglected when the surface temperature is higher than 1000 Kin many literatures.However,from theoretical analysis,author find that CO_2 plays an important role in spanning the reaction range from the reaction-rate controlled regime to the diffusion controlled oxidation regime,and can't be ignored.It has been shown that for the ablation of carbon-based materials in a high speed stream of dissociated air,the"fast"reaction must be used with both products of CO_2 and CO at the same time.There are two different platforms in the diffusion controlled regime.The first platform results from reactions of the predominant CO_2 product,and the other is due to the predominant CO product reactions.With the increases of the surface temperature,the ratio of the mass fraction of CO to CO_2 at the surface rises rapidly from zero to infinity,which causes the oxidation process to change automatically from the nominated "fast"reaction to the so called "slow"reaction lines.The dual platform theory has been confirmed by several experimental results.
引文
[1]国义军,代光月,桂业伟,等.碳基材料氧化烧蚀的双平台理论和反应控制机理[J].空气动力学学报,2014,32(6):755-760.Guo Y J,Dai G Y,Gui Y W,et al.A dual platform theory for carbon based material oxidation with reaction diffusion rate controlled kinetics[J].Acta Aerodynamica Sinica,2014,32(6):755-760.
[2]Scala S M.The ablation of graphite in dissociated air,Part I:Theory[R].AD289298,1962.
[3]Diaconis N S,Gorsuch P D,Sheridan R A.The ablation of graphite in dissociated air,Part II:Experimental investigation[R].AD290051,1962.
[4]Maahs H G.Oxidation of carbon at high temperatures:reaction-rate control or transport control[R].NASA TN D-6310,1971.
[5]Swann R T,Pittman C M,Smith J C.One-dimensional numerical analysis of the transient response of thermal protection systems[R].NASA TN D-2976,1965.
[6]黄振中.烧蚀端头的瞬变外形及内部温度分布[J].空气动力学学报,1981(1):53-65.
[7]卞荫贵,钟家康.高温边界层传热[M].北京:科学出版社,1986.
[8]国义军.炭化材料烧蚀防热的理论分析与工程应用[J].空气动力学学报,1994,12(1):94-99.Guo Y J.An analysis of a charring ablative thermal protection system with its engineering application[J].Acta Aerodynamica Sinica,1994,12(1):94-99.
[9]Milos F S,Chen Y K.Comprehensive model for multicomponent ablation thermochemistry[R].AIAA-97-0141,1997.
[10]黄海明,杜善义,吴林志,等.C/C复合材料烧蚀性能分析[J].复合材料学报,2001,18(3):76-80.Huang H M,Du S Y,Wu L Z,et al.Analysis of the ablation of C/C composites[J].Acta Materiae Compositae Sinica,2001,18(3):76-80.
[11]张志成,潘梅林,刘初平.高超声速气动热和热防护[M].北京:国防工业出版社,2003.
[12]Leeds D H,Welsh W E,Slaughter J I,et al.Air plasma arc materials testing for re-entry[R].AD601808,1964.
[13]Baron J R,Bernstein H.Heterogeneous rate coupling for graphite oxidation[J].AIAA Journal,1971,9(8):1588-1595.
[14]Milos F S.Comparison of ablation predictions for carbonaceous materials using CEA and JANAF-based species thermodynamics[C].Proc of the 35th Annual Conference on Composites,Materials,and Structures.2011.
[15]益小苏,杜善义,张立同.复合材料手册[M].北京:化学工业出版社,2009.
[16]Clark R K.An analysis of a charring ablator with thermal nonequilibrium,chemical kinetics,and mass transfer[R].NASA TN D-7180,1973.
[2]Scala S M.The ablation of graphite in dissociated air,Part I:Theory[R].AD289298,1962.
[3]Diaconis N S,Gorsuch P D,Sheridan R A.The ablation of graphite in dissociated air,Part II:Experimental investigation[R].AD290051,1962.
[4]Maahs H G.Oxidation of carbon at high temperatures:reaction-rate control or transport control[R].NASA TN D-6310,1971.
[5]Swann R T,Pittman C M,Smith J C.One-dimensional numerical analysis of the transient response of thermal protection systems[R].NASA TN D-2976,1965.
[6]黄振中.烧蚀端头的瞬变外形及内部温度分布[J].空气动力学学报,1981(1):53-65.
[7]卞荫贵,钟家康.高温边界层传热[M].北京:科学出版社,1986.
[8]国义军.炭化材料烧蚀防热的理论分析与工程应用[J].空气动力学学报,1994,12(1):94-99.Guo Y J.An analysis of a charring ablative thermal protection system with its engineering application[J].Acta Aerodynamica Sinica,1994,12(1):94-99.
[9]Milos F S,Chen Y K.Comprehensive model for multicomponent ablation thermochemistry[R].AIAA-97-0141,1997.
[10]黄海明,杜善义,吴林志,等.C/C复合材料烧蚀性能分析[J].复合材料学报,2001,18(3):76-80.Huang H M,Du S Y,Wu L Z,et al.Analysis of the ablation of C/C composites[J].Acta Materiae Compositae Sinica,2001,18(3):76-80.
[11]张志成,潘梅林,刘初平.高超声速气动热和热防护[M].北京:国防工业出版社,2003.
[12]Leeds D H,Welsh W E,Slaughter J I,et al.Air plasma arc materials testing for re-entry[R].AD601808,1964.
[13]Baron J R,Bernstein H.Heterogeneous rate coupling for graphite oxidation[J].AIAA Journal,1971,9(8):1588-1595.
[14]Milos F S.Comparison of ablation predictions for carbonaceous materials using CEA and JANAF-based species thermodynamics[C].Proc of the 35th Annual Conference on Composites,Materials,and Structures.2011.
[15]益小苏,杜善义,张立同.复合材料手册[M].北京:化学工业出版社,2009.
[16]Clark R K.An analysis of a charring ablator with thermal nonequilibrium,chemical kinetics,and mass transfer[R].NASA TN D-7180,1973.