In this study, based on the CO conversion rate obtained with a monolith honeycomb catalyst and adsorbed surface species identified with in-situ FTIR for powdered catalyst, detailed CO oxidation surface reaction mechanisms on Pd/Al₂O₃ have been developed. As a result, it is found that CO absorbs onto Pd by linear and bridge regime, which is not detected for Pt and Rh in previous work. Based on those results, thermodynamically consistent detailed surface reaction mechanism for CO/O₂ reaction on Pd is developed. Further, combining the CO / O₂ surface reaction mechanism for Pd with previously developed mechanisms for Pt and Rh, CO conversion rate on bimetal catalysts of Pt/Rh, and furthermore, tri-metal catalyst of Pt/Pd/Rh are simulated and compared with experimental results for several PGM ratios. Results of numerical simulation for various Pt/Pd/Rh ratios as well as CO/O₂ ratios quantitatively agreed with experimental results.

This study investigated the influences of a small obstacle upon an unstable detonation front using the smoked-foil technique. In the present experiments, a stoichiometric propane–oxygen diluted with nitrogen mixture at initial pressure of 30 or 70 kPa was used as an explosive gas mixture and four types of obstacles were used: forward-facing steps and slopes and backward-facing steps and slopes. We used the propane-fuel gas mixture, because its non-dimensional activation energy is larger than that of the hydrogen-fuel gas mixture used in our previous study. In the cases of forward-facing steps and slopes, the detonation front structure was not significantly affected similarly to the previous study of hydrogen–oxygen diluted with argon mixture. The shock-tube model shows that the reflected shock wave from the forward-facing step does not drive a transverse wave obviously stronger than the intrinsic transverse wave. On the other hand, the detonation re-activation phenomena were observed in the vicinity of the sidewall downstream of the backward-facing steps and slopes. Although the cellular pattern was similar to the case of hydrogen gas mixture as a whole, the transverse waves were more attenuated behind the diffracted shock wave in the propane gas mixture. Moreover, the detonation re-activation also occurred in a far region from the sidewall in this study. However, noteworthy was that the distance between the backward-facing step and the re-activation position z_ra was expressed by the height of the step |h| and the CJ detonation cell width λ_CJ as z_ra/λ_CJ = 2.9(|h|/λ_CJ)^0.84 and this empirical formula well describes also the results of hydrogen gas mixture and many other mixtures, showing that the non-dimensional activation energy has little effect on the position where the detonation re-activation occurs. This implies that the detonation re-activation on the sidewall is predominantly governed by the transition from the regular reflection to the Mach reflection on the sidewall of the diffracted shock wave decoupled with chemical reaction through the slip-line formation, where the degree of the decay of the diffracted shock wave is influenced not by the stability of the detonation-front cellular structure but by λ_CJ, representing the induction-zone length between the leading shock wave and the subsequent exothermic reaction.

The shape, size, and performance of microfluidic chip heaters are designed to fit the housing of microfluidic chips and channels. During the heating process, some of the heat is transferred to the surrounding environment where the microfluidic chip is located, which is typically undesirable. In order to better control the heating of the fluid within the microfluidic channel, this study examines a heating wire placed coaxially inside the channel. The fluid flows through the annular space between the channel and the heating wire, which maintaining a constant heat flux and minimizing heat transfer to the environment. To provide a basis for comparison, an analysis of fluid flow within a straight channel chip with a heat source of constant temperature is also conducted. The methodology used combines analytical modeling with experimental testing. Thermal entropy and entransy flow rate during fluid flow within the microfluidic channel are studied in relation to changes in volumetric flow rate, the temperature of the microfluidic chip housing, and the heat transfer from the heating wire. Additionally, a modified irreversibility ratio is used to further describe the relationship between thermal entropy and entransy flow rate. The results show that the fluid heated in the annular microfluidic channel exhibits lower thermal entropy and higher entransy flow rate compared to the straight channel chip.

In this study, a microscopic visualization of the pyrolysis of woody biomass is conducted using the BL20B2 beamline at SPring-8, a large synchrotron radiation facility. Changes in the shape and internal structure of the woody biomass are visualized using ultra-high-speed X-ray computed tomography (CT). The specimens are Japanese cypress, ramin, and bamboo with a height of 5 mm and diameter of 5 mm. Infrared halogen heater is used as the heat source to achieve a high heat flux. The specimens expand under a high heat flux. Compared with the experimental results under a low heat flux obtained in a previous study (Daitoku, 2017), a completely different aspect is observed. In a nitrogen atmosphere, the internal structure of the specimens during transient pyrolysis are visualized using ultra-high-speed X-ray CT.

One of effective paths to achieve net zero energy-related CO₂ emissions by 2050 is to shift away from coal. A reforming technology that combines torrefaction treatment with densification molding is considered to be the promising production method for solid biofuels to replace coal and coal coke. In the study, an optimum combination condition of wet torrefaction (WT) and densification molding is investigated to improve energy properties of solid biofuels such as higher heating value (HHV) and char yield (CY). HHV of wet torrefied samples is correlated with mass ratio of biomass to water (B/W) as well as solid mass yield (SMY), and HHV for B/W =1/20 is 3 to 4% lower than that for B/W =1/5 for the same SMY. From the proposed model to estimate HHV of wet torrefied sample, it is found that the change in fixed carbon content due to B/W results in the change in HHV. Particle density of densified biofuel with wet torrefied sample (WTB-fuel) in the SMY range above 0.6 is equal or higher than that with raw sample. But the advantage of densification molding of wet torrefied sample is not observed in the SMY range lower 0.6. For the same WT condition, the increase in CY due to densification molding is closely related to the suppression of volatile matter generation, which is confirmed by the increase in activation energy. From the investigation results on both effects of wet torrefaction and densification molding on improvement of char yield of WTB-fuel, it is found that enhancement factor of fixed carbon (EFC) for any molding temperature reaches a maximum at SMY of around 0.8, and the maximum EFC is obtained at molding temperature of 200 ℃. Therefore, it is concluded that the optimum combination conditions to produce WTB-fuel are wet torrefaction in the SMY range between 0.7 and 0.8 at higher B/W and densification molding at molding temperature of 200 ℃.