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  1. 1. G.Dinesh kumar, D.Gowri Shankar, D.Balaji / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 1, January -February 2013, pp.1955-1960 Computational evaluation of strut based scramjet engine combustion with different conventional fuel/oxidizer G.Dinesh kumar1, D.Gowri Shankar2, D.Balaji3 Department of Aeronautical Engineering, Hindustan University, IndiaAbstract — The high performance and instability in This type of vehicle, according to current proposals,combustion chamber are the most challenging will use scramjet propulsion system. Both hydrogenrequirements for faster developments and and hydrocarbon fuels are considered depending ontechnical advances in most of the engines. The applications and speed range. Although, hydrogendesign and development challenges of such has attractive features in terms of specific impulse,engines are highly influenced by its combustion ignition characteristics, etc., liquid hydrocarbon fuelbehavior taking place inside the combustion is preferred for volume limited applications in thechamber. Studies on the injection, vaporization lower hypersonic region (M<8). Starting from theand combustion phenomena inside combustion pioneering work of significant advances is made inchamber are a growing challenge and difficult the design of scramjet engines. Over the last fewentities in design and vigorously investigated by decades, great emphases were placed on analytical,researchers. In this domain, the present research experimental and CFD techniques to understand theis formulated for analyzing the combustion mixing and combustion processes in the scramjetperformance of hydrogen/hydrocarbon and combustors. In a recent review, Emerging hypersonicoxygen computationally in a strut based air breathing propulsion systems offer the potential tocombustion chamber. This work leads way to enable new classes of flight vehicles that allow rapididentify the injection flow behavior and the response at long range, more maneuverable flight,hypersonic combustion nature of various fuels better survivability, and routine and assured access towith comparison of different parameters. CFD space. Historically, rocket boosters have been used tosimulations of the hydrogen/hydrocarbon fuelled propel hypersonic vehicles (i.e., those flying fasterstrut based scramjet combustor are performed at than 5 times the local speed of sound) forMach 2 airstream having typical Mach 10 flying applications such as space launch, long-rangeconditions. The primary objective of this study is ballistic flight, and air-defense interceptor numerically evaluate the combustor Air breathing propulsion systems currently underperformance for varying fuels and its injection development will provide a means for sustained andparameters .Mixing and reacting flow accelerating flight within the atmosphere atcharacteristics of the combustor are studied for hypersonic speeds long-range cruise missiles forthe centrally located strut based scramjet attack of time-sensitive targets, flexible high-altitudecombustor solving three dimensional RANS atmospheric interceptors, responsive hypersonicequations k-epsilon turbulence model using aircraft for global payload delivery, and reusablecoupled implicit solver based on finite volume launch vehicles for efficient space access.approach. Salient results of non-reacting and Using kerosene fuel and commercial CFD Beherareacting flow simulations are presented. and Chakraborty1 numerically studied the flow fieldPerformance parameter like mixing efficiency, of a ramp cavity based scramjet combustor. Theirtotal pressure recovery and computational results had shown good agreementhydrogen/hydrocarbon consumption are with experimental values, and the computedcomputed and compared for different cases. The combustion efficiency was near unity, when the fuelcomputation is performed by using a CFD solver equivalence ratio was smallFLUENT and analyzed for LES model of four The requirements of numerical simulation fordifferent fuels. modelling turbulent combusting flows and the problems associated with it were studied by Borgi etKeywords— Hydrogen fuel, Hypersonic al. 2. The author observed that the reactive zonescombustion, Combustion performance, Strut were very thin leads to problems in modelling ofinjector, Air breathing hypersonic vehicle mean reaction rates. The authors found out that the temperature and concentration fluctuations I. INTRODUCTION influenced strongly the chemistry of combustion. The success of an efficient design of a To assess the merits of kerosene and methane forhypersonic air breathing cruise vehicle largely future reusable booster stage was investigated bydepends on the proper choice of propulsion system. Burkhardt et al. 3. They used liquid oxygen as the oxidizer for both fuels. Initially they identified the 1955 | P a g e
  2. 2. G.Dinesh kumar, D.Gowri Shankar, D.Balaji / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 1, January -February 2013, pp.1955-1960thermodynamic and chemical properties of kerosene c) Equation of conservation of energy:and methane. They found that methane fueled  propulsive systems are disadvantageous, when cost ( E )  . ( E  p)  t =was considered Grueing and Mayinger 4 carried out an    experimental investigation of supersonic combustion .k eff T   h j J j  ( . eff )  Qof liquid hydrocarbons. They burnt kerosene in air   j   (2.5)flow at Mach 2.5 in a modelled scramjet combustor. d) Equation of state:On comparing the results with hydrogen combustion p = ρRT (2.6)they found that the kerosene combustion by a gas For numerical modelling of multiphase flowsdynamic feedback mechanism strongly affected the existing in the flow field, the above equations aresupersonic combustion process. slightly modified to adjust the effect of the liquid- Town end 5 reported about the best possible vapour mixture.applications of scramjets in the current scenario.Citing several examples he proved the value of 3. Material and Designhydrocarbons for the initial stages of launcher a. Length of strut - 0.39m.acceleration and reduction of bulky tankage by b. Radius of injector - 0.005m.selection of kerosene as the fuel. Through his c. Breadth - 0.01m.findings the author came to a conclusion that the use d. Wedge angle - 100.of hydrocarbons. The above mentioned data’s are the geometric II. CFD ANALYSIS dimensions of channel that is taken for analysis. It is For the ideal thrust chamber, some of the designed using AutoCAD or Gambit in a 2parameters are directly dealt by design parameters dimensional aspect. The purpose of these studies wassuch as combustor geometry, size, and injector to determine the hypersonic combustion analyses ofelement design and nozzle configuration. Here an various fuels are analyzed. This strut is placed alongattempt has been carried out to analyse the sizable the flow distribution with the blunt leading edgeparameters related to thrust chamber design throughnumerical modelling of thrust chamber performance A. Computational Modellingencompassing a wide range of approaches of CFD. The computational domain is created with properHence, the results of the numerical analysis have dimensions. The dimension of the channel is .039 xbeen found out in two major domain of thrust 0.1m with the half wedge angle is 100 and the radiuschamber. of the injector is 0.005m. This 2-D model is designed by using the GAMBIT software. Before design the1) Injection system using strut injector, proper dimension should be selected and after the2) Analysis of various fuels. design is to be meshed. Thus the investigation of combustion andflow behaviour in a propulsion system’s thrust B. Meshing of Modelchamber has been carried out with the help of The grid was generated by using the gambitnumerical scheme using the governing equations as software and size of the meshed file is 0.1 spacingfollows between the grid points. In the figure shown below The mass flow rate of an injector can be rectangular obstacle were used. Similarly for othersdetermined using the continuity equation: the grid was generated. m  U 1 A1  U 2 A2  (2.1) The above mentioned data’s are the geometricand the Bernoulli equation: dimensions of channel that is taken for analysis. It is designed using AutoCAD or Gambit in a 2 U 1 2 U 2 2p 01  p1   p2   p1 2 (2.2) dimensional aspect. The purpose of these studies was 2 2 to determine the supersonic combustion using thisa) Equation of conservation of mass: strut based centrally located injector. Even the   hypersonic combustion analysis of various fuels is  .v   0 (2.3) analyzed. This strut is placed along the flow t distribution with the blunt leading edgeb) Equation of conservation ofmomentum C. Boundary Conditions v     .( )  p  .( )  g  F (2.4) The flow domain has been formed inside the t combustion channel. The dimension of combustion       T   . I     2   channel has been taken as 1600mm × 38mm. Thewhere fuel Injection having diameter 10mm, located at the  3  leading edge of the combustion channel has been 1956 | P a g e
  3. 3. G.Dinesh kumar, D.Gowri Shankar, D.Balaji / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 1, January -February 2013, pp.1955-1960made for computation. The following boundary In this project seeing all these analysis andcondition has been assigned. For modelling purpose numerical simulations we conclude that air breathingoxygen velocity inlet boundary condition has been engine (scramjet engine) found to show better resultassigned for the inlet domain and pressure outlet using kerosene fuel at 8.8 Mach and 21500 Pascalcondition has been assigned to the outlet domain. when fuel injected by strut. The ejection velocityOther boundary condition includes the default hard finally we got near 4400m/s, which comes around 13interior of the wall created using Gambit. The Mach. This shows combustor is performing in Hyper-boundary conditions are given in the table 4.1 for the sonic regimesinlet and outlet. V. FUTURE SCOPE OF WORK III. RESULTS AND DISCUSSIONS The work done gives a satisfactory result A comparative histogram showing exit with present combustor model and for more concisevelocities of scramjet combustor for various fuels are dealing we can change some design parameters. Theshown fig 6.6e. In that plot kerosene found to be future scopes in this work are:most efficient, the next lays ethanol, then methanol. The problem we solved is 2D and singleHydrogen is pollution free fuel but not suitable for air plane mixing is analyzed. In future we can extend tobreathing engines at hypersonic velocities. The plots 3D, and double plane mixing is possible. We canclearly show that kerosene is best efficient fuel for predict the flow at each nook and corner ofour combustor model. The exit velocity found to combustor.increase with respect to time in fig .13 We analyzed for a fuel velocity of 660m/s. In From the plot, the next efficient fuel is ethanol, future we shall do it by changing velocities of fuelhaving 6 hydrogen bonds. Based the number of and air flow. It may give a better understanding ofhydrogen bond, the performance is rated. The fuel performance at various ranges.numerical investigation also shows a similar result. New type of injector other than strut such asMethanol having 4 hydrogen bonds showing results aerodynamic, ramp based or cantilever shall belesser than ethanol. Hydrogen stands last in the employed to see results.analysis. The performance results of analysis shows a We defined our fuel temperature at injector.very lower velocity magnitude for hydrogen fuel. In alternate we can specify the interior and exterior wall temperature of the combustor. IV. CONCLUSION Designs for hypersonic engines have been REFERENCESaround since the early 1900’s. Ramjet technology [1] Ahmed, A., and Briec, E., ―Overview ofhas been developing over the past eight decades and, CFD in automotive engine combustion‖,except for marginal improvements, has been shown Network Newsletter, Vol-1, No.-3, Dept.ofto be suited for atmospheric flight speeds up to Mach Engine Engineering, Renault, January, 2002,5. The desire for faster, more efficient engines gave pp. 17-20.birth to the idea of a scramjet, utilizing supersonic [2] Ananias, T., ―A numerical approach for thecombustion and potentially expanding the speed simulation of non-premixed counter flowenvelope to the Mach 15 range. The promise of flames and reacting mixing layer‖,covering the entire planet at high speed from Institution for Mathematics and it’shorizontal takeoff for both civil and military aircraft Applications Publication,Vol-3, 1999-2000,is an attractive prospect. However, along with new pp. and discoveries also come new obstacles [3] Arunajatesan, S., and Sinha, N., ―Large eddyto be addressed. simulations of supersonic impinging jet flow In order to study the establishment of the fields‖, AIAA 2002-4287, proceedings of 38major flow features in a generic scramjet combustor AIAA/ASME/SAE/ASEE Joint Propulsionseveral numerical simulations were carried out. A Conf. and Exhibit, Vol-1, July 7-10, 2002,question still prevails in efficient fuel for hypersonic pp. 1-9.regions. We considered 4 fuels for our analysis [4] Bai, H.C, Le, J.L, Zhang, Z.C, Goldfield,(Hydrogen, kerosene, ethanol & methanol). M.A, Nestoulia, R.V., and Starov, A.V, “ On comparing performance of all the fuels, Methodical aspects of investigation ofwe concluded that kerosene has higher ejection kerosene ignition and combustion in avelocity. The reason is number of hydrogen bonds. scramjet model”,Report of Centre ofBreaking up of hydrogen bonds releases heat energy, Aerodynamic Research andsince kerosene has several hydrogen bonds (C12H23) Development,China, Vol-13,July, 2002, pp.the energy released is much higher than other fuel 101-105.under specified operating conditions. [5] Behera, and Chakraborty, D “Numerically studied the flow field of a ramp cavity based 1957 | P a g e
  4. 4. G.Dinesh kumar, D.Gowri Shankar, D.Balaji / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 1, January -February 2013, pp.1955-1960 scramjet combustor”, AIAA Paper No. 2006–3895 2010. [6] Bhatia, R., and Sirignano, W.A., “One- dimensional analysis of liquid fuelled combustion instability”, Jr. of Prop. and Power, Vol. 7, No. 6, November-December, 1991, pp. 652-660. [7] Bogdanoff, D.W., “Advanced injection and mixing techniques for scramjet combustors”, Jr. of Prop. and Power, Vol. 10, No.2, March-April, 1994, pp. 183-187. 111 [8] Broadbent, E.G., “Calculation of inviscid 3- Fig.4 Contours of Velocity Magnitude after d supersonic flows with heat and mass Combustion addition”, Phil. Trans. Royal Soc. London,A (1999) 357, 1999, pp. 2379- 2386 [9] Burkhardt, H., Sippel, M., Herbertz, A., and Klevanski, J., “Comparative study of kerosene and methane propellant engines for reusable liquid booster stages”, Proceedings of 4th Intl. Conf. on Launcher Tech., December 3-6, 2002, pp. 1-12 [10] Charles. M., Gokhale, S.S, and Jayaraj, S., “The Nonreactive mixing study injector of a scramjet swept-strut fuel injector”, Jr. of Aerospace Sciences and Technologies , Vol 58, No 4, November, 2006, pp. 1-711. Table and Figure Fig.5 Contours of Velocity Magnitude after CombustionFig.1 A generic scramjet combustor with centrallylocated Fuel injector strut. (From NASA Contractor Fig.6 Contours of Mass Fraction of co2Report 187467) Fig.3 Combustor boundary conditions Fig.7 Contours of Mass Fraction of H2 o 1958 | P a g e
  5. 5. G.Dinesh kumar, D.Gowri Shankar, D.Balaji / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 3, Issue 1, January -February 2013, pp.1955-1960 Fig.8 Contours of Mass Fraction of O2 Fig. 12 Plot of Velocity Magnitude of Methanol Fig.9 contour of Arrhenius rate of reaction Fig.13 Plot of Velocity Magnitude of Kerosene Fig.10 Plot of Velocity Magnitude of Ethanol Fig. 14 Static temperature of kerosene as fuel Fig. 11 Plot of Velocity Magnitude of Hydrogen 1959 | P a g e
  6. 6. Fig. 15 Histogram comparing velocity of all fuel 1960 | P a g e