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Na J.,Tianjin University of Technology | Liu G.,Tianjin University of Technology | Zhou T.,Tianjin University of Technology | Ding G.,Tianjin University of Technology | And 2 more authors.
Catalysis Letters | Year: 2013

ZSM-5/MCM-41 zeolite composites with varying mesopore sizes were prepared through alkali-desilication and surfactant-directed recrystallization with different chain length of alkyltrimethylammonium bromide. XRD and TEM revealed that the composites possessed the characteristics of both ZSM-5 and mesoporous MCM-41 with hexagonal symmetry. N2-adsorption-desorption, 27Al MAS NMR, NH3-TPD and in situ FT-IR results suggested that the sizes of the mesopores and the accessibility of acid sites could be affected greatly by the chain length of alkyltrimethylammonium bromide used. Catalytic cracking of n-dodecane over ZSM-5/MCM-41 composites was studied in the form of coatings on the inside of a tubular reactor at 550 °C and 4 MPa. The conversion of n-dodecane increased gradually with increasing the mesopore sizes of ZSM-5/MCM-41 composites, implying a positive effect of the mesopores on the diffusion inside pore channels and the accessibility of acid sites by the reactants. © 2013 The Author(s).


Wang L.,National University of Defense Technology | Wang L.,Science and Technology on Scramjet Laboratory | Xia Z.-X.,National University of Defense Technology | Xia Z.-X.,Science and Technology on Scramjet Laboratory | And 3 more authors.
AIAA Journal | Year: 2014

Plasma based actuators are very promising because of their advantages of robustness, simplicity, sufficient bandwidth, and fast response. The actuator is composed of the following components: anode, cathode, trigger electrode, cavity, and a cap with an orifice. Electrodes are fabricated from Tungsten, and the tip was sharpened to decrease the disruptive voltage. Trigger-to-cathode spacing is set to 1 mm, and anode-to-cathode spacing is 3 mm. The body of the cavity and the cap are made of boron nitride, which has a higher insulation and thermal conductivity. The pressurized gas is expelled through the orifice and creates PSJ. The injection effect of the high speed PSJ produces local vacuum in the cavity and draws fluid back into it, and the cavity is recharged for the next pulse. To ensure that the streamer discharge is established between the trigger electrode and the cathode, the spacing of the trigger-to-cathode electrode should be smaller than the trigger-to-anode electrode.


Wang L.,Tianjin University of Technology | Wang Y.,Tianjin University of Technology | Hao J.,Tianjin University of Technology | Liu G.,Tianjin University of Technology | And 2 more authors.
Applied Catalysis A: General | Year: 2013

HZSM-5 zeolite coatings on the inner surface of stainless steel tubes (2 mm i.d., 350 mm length) were prepared by the secondary growth method and characterized by XRD, SEM and in situ FT-IR. The catalytic performance of the resulting HZSM-5 coatings was evaluated using the catalytic cracking of n-dodecane at 4 MPa and 525 C (supercritical conditions) as a model reaction. With the repeated time of the secondary growth from 1 to 4, the mean thickness of HZSM-5 layers increased from 5.74 to 13.75 μm, together with an increase in the density. Over the zeolite coating of the third growth with suitable thickness (11.63 μm) and density, a high conversion of n-dodecane was achieved. The NaOH-treatment on HZSM-5 zeolite layers induced the creation of meso-pores in the HZSM-5 layer, thus enhanced its catalytic activity. These experimental findings demonstrated that a balance between the thickness and diffusivity of the HZSM-5 layer benefits its catalytic activity. © 2013 Elsevier B.V. All rights reserved.


Cai X.,Science and Technology on Scramjet Laboratory | Liang J.,Science and Technology on Scramjet Laboratory | Lin Z.,Science and Technology on Scramjet Laboratory | Zhuang F.,Academy of Equipment Command and Technology | Zhuang F.,Chinese Academy of Sciences
49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference | Year: 2013

The open-source program AMROC, implementing a block-structured adaptive mesh refinement method, was adopted for the fine structure numerical simulation of detonation initiation in quiescent and supersonic combustible mixtures. The effects of various geometry parameters, including the diameter of hot jet, the height of the channel and the location of the hot jet, were considered and analyzed in these simulations. Results showed that for certain kind of hot jet, the energy strength was determined by the diameter of hot jet in quiescent combustible mixtures. There existed a critical diameter of the hot jet. Whether the two-time wall reflection was realized effectively or not was depend on the location of hot jet. The height of the detonation channel was a key factor for the strength of the reflected shock wave and played a important role on the realization of the valid two-time wall reflection. In supersonic combustible mixtures, there existed a critical diameter of hot jet too. The height of detonation channel made important impacts on the shock reflection on the upper wall, and whether the local detonation combustion would be realized directly or not on the upper wall was depend on the strength of reflection shock.


Wei B.,Beihang University | Xu X.,Beihang University | Yan M.,Beihang University | Shi X.,Science and Technology on Scramjet Laboratory | Yang Y.,Beihang University
Journal of Propulsion and Power | Year: 2012

Experimental and numerical study of a novel integrated flush-wall aeroramp injector/gas-pilot flame has been conducted in a scramjet combustor. The aeroramp injector consisted of four flush-wall holes. Downstream of it, the gas-pilot flame as located as igniter and flame holder. The experiment's facilities can deliver a continuous supersonic flow of Mach number 2.0 with a total temperature of 1200 K. In the cold flow tests, schlieren and surface oil-flow visualization pictures in the vicinity of injectors were taken to obtain a qualitative assessment of the injectors flowfields. The detailed characteristics of cold flowfields were numerically simulated, which agreed well with the experimental results. Some important parameters, such as mixing efficiency, penetration depth, and maximum concentration decay, were investigated to analyze the mixing performance. In the hot flow tests, ethylene was injected into the mainstream at jet-to-freestream momentum flux ratios q between 1.2 and 3.9. One-dimensional performance analysis of the test data indicates combustion efficiencies as high as 90% in all cases. This was the first time that the integration of an aeroramp injector/gas-pilot flame for supersonic combustion was studied. The results show that this novel injection and flame holding configuration for supersonic combustion is feasible. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc.


Baoxi W.,Beihang University | Baoxi W.,Science and Technology on Scramjet Laboratory | Bing C.,Beihang University | Minglei Y.,Beihang University | And 3 more authors.
Acta Astronautica | Year: 2012

Performance and operating limits of an ethylene-fueled injection and ignition/flame-holding system consisting of an aerodynamic-ramp injector and a gas-portfire were investigated both experimentally and numerically, using the scramjet direct connect facility at the Beihang University. The experimental operating conditions include (1) the fuel equivalence ratio, (2) the gas-portfire location, and (3) the gas-portfire gas-to-freestream momentum flux ratio (qg). The lean burn limit was at a fuel equivalence ratio of 0.05. The gas-portfire was placed downstream of the injector on the centerline at three different locations in order to ind the best suitable gas-portire/aero-ramp injector geometrical configurations. Results showed that the distance from the gas-portfire to the aero-ramp injector array was a critical parameter which influenced the combustion eficiency obviously. The ignition delay time was sensitive to the qg. When the qg was below 0.55, the ethylene cannot be ignited; when the qg was 0.64, the ignition delay time reached nearly 1 s; the increase of the qg from 0.64 to 1.43 shortened the ignition delay time obviously, but had no influence on the combustion efficiency. The detailed combustion flowfields were investigated by the 3-D numerical study and the numerical results agreed well with the static pressure distributions obtained by experiments (average error < 5%). © 2012 Elsevier Ltd. All rights reserved.


Wang C.-A.,Tsinghua University | Wang M.-F.,Science and Technology on Scramjet Laboratory
Frontiers of Materials Science | Year: 2013

The thermal shock behavior of ZrB2-SiC ceramics was studied with water, air and methyl silicone oil as quenching media, respectively. The temperature of all coolants was room temperature (25°C) and the residual strength of the ceramics after quenching was tested. The strength of the ceramics after water quenching had an obvious drop when the temperature difference, ΔT, was about 275°C, while the residual strength of the specimens quenched by air and silicone oil only varied a little and even increased slightly when the temperature difference was higher than 800°C. The different thermal conductive coefficient of the coolants and surface heat transfer coefficient resulted in the differences in the thermal shock behavior. The formation of oxidation layer was beneficial for improving the residual strength of the ceramics after quenching. © 2013 Higher Education Press and Springer-Verlag Berlin Heidelberg.


Liu Z.,National University of Defense Technology | Liu Z.,Science and Technology on Scramjet Laboratory | Liang J.,National University of Defense Technology | Liang J.,Science and Technology on Scramjet Laboratory | And 2 more authors.
Journal of Thermophysics and Heat Transfer | Year: 2014

An efficient procedure for evaluating the thermodynamic and transport properties of real fluids was presented. Block-structured adaptive mesh refinement was used toconstruct the equationsof state look-up table, which provides uniform accuracy over a selected thermodynamic plane with fewer grids. An overlapping uniform index domain was developed to provide fast search capability. Properties can be evaluated by bilinear, bicubic, and biquintic interpolation to achieve different levels of function continuity and thermodynamic consistency. Reconstruction discontinuity may appear across the interface of unequally sized blocks, but the level of discontinuity decreases when reconstruction is based on structured grids on each block. The effectiveness and efficiency of the method was demonstrated by comparing the storage, data retrieval, and computational fluid dynamics samples. The storage requirement decreases by 20 to 80% comparedto the table constructed with uniform mesh. The overlapping uniform index domain is 14 to 19% faster than the tree data-structure in computational fluid dynamics calculations with the table of 0.1% accuracy. When reconstructed property is within 0.1% of the exact value, the degree of discontinuity is small enoughtoobtainaconvergent solutionincomputational fluid dynamics cases.Anequationofstate table look-up method is as efficient as ideal gas equations of state and two orders of magnitude faster than the complex thermodynamic database. Copyright © 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.


Li G.,Zhejiang University | Kuang Y.,Zhejiang University | Hu S.,Science and Technology on Scramjet Laboratory
Shiyou Xuebao, Shiyou Jiagong/Acta Petrolei Sinica (Petroleum Processing Section) | Year: 2015

The formation process and mechanism of ZSM-5 coating on stainless steel substrate prepared by using in-situ hydrothermal synthesis were studied. The influences of several factors on the preferential orientation of the crystals in the coating were discussed. The results showed that a-oriented ZSM-5 coating was formed on the upward side, while no continuous coating formed on the downward side of stainless steel substrate, when it rested in the autoclave at an angle. Under the same hydrothermal conditions, randomly oriented crystals were formed on the substrate which was positioned horizontally at the bottom of the autoclave, and after ultrasonic washing in deionized water for 20 min, however, some a-oriented crystals also appeared. Continuous a-oriented ZSM-5 coating was successfully obtained on the horizontally positioned substrate, when a reaction mixture with a small amount of ethanol was employed. a-Oriented ZSM-5 coating was shown to be transformed from an amorphous coating on the substrate in two steps, in which b-oriented crystals were first formed from the amorphous coating, followed by the formation of a-oriented crystals on the (010) face of these b-oriented crystals. On the horizontally positioned substrate, a-oriented ZSM-5 coating was also formed first, and then was covered subsequently with randomly oriented crystals which were formed in the solution. ©, 2015, Science Press. All right reserved.


Guo Y.,Zhejiang University | Yang Y.,Zhejiang University | Fang W.,Zhejiang University | Hu S.,Science and Technology on Scramjet Laboratory
Applied Catalysis A: General | Year: 2014

Ni-B nano-amorphous alloys have been successfully fabricated with an average diameter of 20 nm, where c-undecyl calix[4]resorcinarene was used as surfactant layers to counter attractive interparticle forces and prevent agglomeration. Resorcinarene-encapsulated Ni-B nanoparticles can be stably and highly dispersed in the JP-10 for its quasi-homogeneous catalytic cracking. Campared with thermal decomposition, catalytic reaction of JP-10 on Ni-B nanoparticles exhibits obvious enhancement in conversion, even about 20% higher in low temperature region. Nevertheless, catalyst has no significant effect on the selectivity of alkene. Liquid products distribution are consistent with the mechanism proposed by Olivier. The coke deposits were investigated by temperature-programmed oxidation (TPO) method. In the present work, the catalyst samples are characterized, respectively, by means of X-ray diffraction (XRD), Transmission electron microscopy (TEM), UV-vis spectroscopic measurements, Inductively coupled plasma spectroscopy (ICP), Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). The investigated results indicate that resorcinarene are well capped on the Ni-B nanoparticles. © 2013 Elsevier B.V. All rights reserved.

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