About the lab

Combustion and Thermal Fluid

Featured research (45)

Methylcyclohexane (MCH) and n-heptane (nC7) were used to perform experimental studies in high-temperature oxidation pretreated STS304 reactor (ϕ2 × 0.5 × 1000 mm) at 873–1073 K, 1.0 MPa, and 1.0 mL/min feed rate. The heat sinks of the two fuels were calculated based on the conversion and product distribution. MCH was found to have difficulty in achieving high heat sink at low and high temperatures. The formation pathways of ethylene and benzene were then compared. Results showed their main precursors were similar, but the contribution proportion of each path was different affected by initial cracking reactions of MCH and nC7. The coking rate of MCH was lower than that of nC7 at low temperatures, while the trend was the opposite at high temperatures. The variation in C/H ratio of coke for MCH and nC7 with temperature was the same, whereas the C/H ratio of the former was significantly lower. The unique unimolecular demethylation and intramolecular stepwise dehydrogenation reactions of MCH caused its coking rate to be higher than that of nC7. An experimental method was proposed to determine the coking active site density based on composition and structure of coke. Finally, a coking mechanism based on the growth of spherical coke particles was proposed.
The flame propagation processes involving deflagration-to-detonation transition (DDT) and detonation propagation in a novel millimetre-scale spiral channel (MSDC) are studied experimentally. The channel is of 3.0 mm in width and 5.2 m in length, embedded in a stainless-steel plate. In particular, a tiny gap of 0.02-mm width is reserved between the upper cover plate and the channel. Stoichiometric propane/hydrogen/air mixtures were adopted as the reactant. The combustion modes are investigated with various initial pressure (P0) and hydrogen blend ratio (XH), ranging from 100 to 500 kPa and 0.6 to 1.0, respectively. For lower P0 and XH, the flame gradually develops into an isobaric flame owing to significant thermal losses in narrow channels. With the increase of P0 and XH, the excess-enthalpy effect plays an important role, and a quantity of high-temperature burned gas in the inner turn enter the outer turn through the gap resulting in a spontaneous flame ahead of the wave front. It promotes the flame acceleration and the onset of local explosion. In subsequent detonation propagation process after DDT, multiple flame combination between the detonation wave and the secondary flame arise and the displacement speed of leading front dramatically increases, even more than 3 DCJ. Furthermore, benefited from excess enthalpy effect and the compact structure of MSDC, the displacement between the DDT location and the ignition spark is of the order of as small as 10 mm. It is of a great potential in application to miniature detonation engines, in which rapid DDT in narrow channels is of strong demand.
In this study, a theoretical model of biomass char gasification reactivity was developed, focusing on the catalytic effect of inorganic elements on the char gasification process. A comparison with previous research results shows that the catalytic ability of K in a fixed bed reactor is stronger than that of Ca, while the catalytic ability of Ca in a fluidised bed reactor is stronger than that of K. The migration and transformation of K and Ca in a fixed bed reactor and fluidised bed reactor are compared. In the fluidised bed reactor, a larger proportion of Ca is transformed into an ion-exchanged state than K, which is contrary to the experimental results in the fixed bed reactor. Then, according to the equivalent-volumetric impregnation method, the saturated loading ratio of K was determined to be 35%, and the full catalytic ratio of K was determined experimentally. Finally, eight typical biomass char samples were selected to perform experiments at different temperatures in the micro fluidised bed reactor to determine the char gasification reactivity, and the results were compared with the calculated values of the model. Results show that the model can effectively predict the char gasification reactivity both in trend and accuracy.
The effects of channel curvature on the flame propagation are examined for premixed flames in micro channels. Previous studies have shown that curved channels can enhance the flame stretching, which can significantly increase the flame propagation speed. In this study, the effect of flame stretching was excluded by the narrow channel limit in order to study the effects of channel curvature on the flame propagation. An asymptotic approach was first extended to include the effects of channel curvature. Accordingly, the two-dimensional problem was reduced to an effective one-dimensional problem with a clear physical meaning of curvature. A parametric study of curvature was then performed to investigate its effects on the flame propagation. It was found that curvature inhibits both the convection and diffusion processes. An increase in the curvature results in a significantly reduced flame thickness and a significantly increased reaction rate. Furthermore, the initial flame propagation speed is smaller in the channel with a larger curvature, but its growth rate is higher under the same ignition condition. With a large channel curvature, the flame has a smaller propagation speed of the steady compressibility-driven flame and a shorter distance to reach the steady state.
The paper revealed the in-depth stabilization mechanisms of a novel vortex-tube combustion technique by using ethanol as fuel, which is implemented by a stratified vortex-tube combustor (SVC). The stability properties of the SVC are investigated, showing that the SVC has a wide stability limit and low-pressure fluctuation amplitudes with a uniform flame front. The equivalence ratio at the lean flammability limit is always below 0.2 and the amplitude of pressure fluctuation is less than 2000 Pa, indicating a highly steady combustion process. The non-premixed flame structure guarantees high mass concentrations near the reaction zone, whilst the vortex flow also decreases the local flow velocity, inhibiting flame blow-out, thus providing good self-adjusting capacity under various global equivalence ratios. The vortex-flame interaction transports the interior high-enthalpy burnt gas to the exterior unburnt gas region thereby promoting ignition. The exterior unburnt gas is also transported to the flame front where it promotes reaction and yields an intensified combustion. The large tangential velocity and density gradient result in the large values of Richardson number, which suggests that laminarization of the flow occurs and results in good aero-dynamic and thermo-dynamic stabilities. The small values of the Rayleigh number indicate good flame-dynamic stability. Therefore, the resultant good self-adjusting capacity and three types of dynamic stabilities are the intrinsic causes of the ultra-steady combustion process in this combustor.

Lab head

Xiaohan Wang
Department
  • Guangzhou Institute of Energy Conversion
About Xiaohan Wang
  • combustion physics and chemistry; micro combustion and utilization system

Members (15)

Liqiao Jiang
  • Guangzhou institute of energy conversion, chinese academy of science
Haolin Yang
  • Chinese Academy of Sciences
Xing Li
  • Chinese Academy of Sciences
Tao Li
  • Chinese Academy of Sciences
Qianshi Song
  • Chinese Academy of Sciences
Hang Su
  • Chinese Academy of Sciences
Shoujun Ren
  • Imperial College London
Fan Li
  • Chinese Academy of Sciences
Liqiao Jiang
Liqiao Jiang
  • Not confirmed yet
Liqiao Jiang
Liqiao Jiang
  • Not confirmed yet
D.-Q. Zhao
D.-Q. Zhao
  • Not confirmed yet
Jiepeng Huo
Jiepeng Huo
  • Not confirmed yet
Jing Zhang
Jing Zhang
  • Not confirmed yet
Weibin Yang
Weibin Yang
  • Not confirmed yet
Weibin Yang
Weibin Yang
  • Not confirmed yet
Q. He
Q. He
  • Not confirmed yet