Challenges and perspectives of green-like lignocellulose pretreatments selectable for low-cost biofuels and high-value bioproduction.

Enzymes and enzymatic mechanisms in enzymatic degradation of lignocellulosic biomass: A mini-review.

Abstract Plant cellulose microfibrils are increasingly employed to produce functional nanofibers and nanocrystals for biomaterials, but their catalytic formation and conversion mechanisms remain elusive. Here, we characterize length-reduced cellulose nanofibers assembly in situ accounting for the high density of amorphous cellulose regions in the natural rice fragile culm 16 ( Osfc16 ) mutant defective in cellulose biosynthesis using both classic and advanced atomic force microscopy (AFM) techniques equipped with a single-molecular recognition system. By employing individual types of cellulases, we observe efficient enzymatic catalysis modes in the mutant, due to amorphous and inner-broken cellulose chains elevated as breakpoints for initiating and completing cellulose hydrolyses into higher-yield fermentable sugars. Furthermore, effective chemical catalysis mode is examined in vitro for cellulose nanofibers conversion into nanocrystals with reduced dimensions. Our study addresses how plant cellulose substrates are digestible and convertible, revealing a strategy for precise engineering of cellulose substrates toward cost-effective biofuels and high-quality bioproducts. 

/pdf/single-molecular-insights-into-the-breakpoint-of-cellulose-170u1ey2.pdf

Single-molecular insights into the breakpoint of cellulose nanofibers assembly during saccharification

High density cellulose nanofibrils assembly leads to upgraded enzymatic and chemical catalysis of fermentable sugars, cellulose nanocrystals and cellulases production by precisely engineering cellulose synthases complexes

Status and strategies for fabricating flexible oxide ceramic micro-nanofiber materials

Distinct cellulose nanofibrils generated for improved Pickering emulsions and lignocellulose-degradation enzymes secretion coupled with high bioethanol production in natural rice mutant

Structural parameters and inlet preswirl have great influences on the static and dynamic characteristics of honeycomb seals. In this paper, a multifrequency elliptical vortex dynamic model of a honeycomb seal was established by an unsteady dynamic grid technique. Based on verification of the numerical model, the effects of honeycomb cell size, axial length, and inlet preswirl on seal performance were investigated. Rotor–bearing–seal stability experiments were carried out to measure the logarithmic decrement rate of the rotor system under different rotational speeds, and the stability of the rotor system was further analyzed. The results showed that with increasing hole depth, leakage of the honeycomb seal increased initially due to the increasing airflow rate in response to vortex formation, and thereafter decreased, caused by the intense dissipation effect of turbulence. With increasing opposite-edge distance of core cell and decreasing axial length, the decreasing number of honeycomb cores on stator surfaces weakened the dissipation capacity of the turbulence, resulting in increases of leakage. Inlet preswirl had little effect on the leakage. However, it had a lower absolute value of tangential airflow excitation force and a lower effective damping coefficient under a higher inlet preswirl, indicating a lower dynamic characteristic of the honeycomb seal. Compared with other seals with different parameters, the honeycomb seal with structural parameters of B3H3L96 showed a higher effective damping coefficient under different inlet/outlet pressure ratios and different vortex frequencies and a higher logarithmic decrement rate under different rotational speeds, indicating a better stability of the rotor system. 

Influence Factors of Honeycomb Seal Performance and Stability Analysis of Rotor System

In order to study the oil–gas two-phase flow characteristics of an aero-engine bearing chamber and improve the scavenge effect of lubricating oil, the two-phase flow solution model of a bearing chamber based on the Euler–Euler method was established. Three improvement schemes were proposed for the ventilation structure and scavenge structure of the bearing chamber. The flow characteristics and scavenge characteristics of a conventional bearing chamber and three improvement schemes under different working conditions were analyzed in depth. The results show that after the conventional bearing chamber ventilation structure is embedded (Embed) and improved, with the increase in the embedding depth, the oil in the cavity is further blocked in the cavity, the amount of oil flowing out from the vent is further reduced, and the scavenge efficiency is further improved. After the slope improvement of the scavenge structure of the conventional bearing chamber, due to the increase in the depth of the oil return groove, the drag effect of the air shear force in the cavity on the oil in the oil return groove is further weakened, and the oil accumulation area on the right side of the scavenge port is further suppressed. The volume fraction of the oil in the cavity is further reduced, and the scavenge efficiency is further improved. The combined improvement scheme (ES) can take into account the advantages of embedding and slope improvement schemes, and further improve the scavenge efficiency. Compared to the conventional bearing chamber, when the oil flow rate is 200 L/h and the speed is 15,000 r/min, the oil return efficiency of the embedded (h = 12 mm), slope (l = 56 mm) and combined improvement schemes are increased by 20.19%, 13.43%, and 37.94%, respectively. 

Research on Oil–Gas Two-Phase Flow Characteristics and Improvement of Aero-Engine Bearing Chamber

Theoretically, a solution model for the static and rotordynamic characteristics of a segmented annular seal based on the local differential quadrature (LDQ) method was established. The impacts of node density and the number of local support domain nodes on the accuracy of the algorithm were analyzed. A test rig for the leakage of segmented annular seals was designed and built. The leakage results measured on the test rig were compared with the theoretical analysis results to demonstrate the accuracy of the local differential quadrature method. The influence of structural and operating parameters on the seal static and rotordynamic characteristics was analyzed Based on the work carried out above. The research results indicate that when the number of local support domain nodes is equal to 3, the static and rotordynamic characteristics of the segmented annular seal can be obtained accurately based on the solution model. As the rotational speed increases, the segmented annular seal's lift force, leakage, stiffness coefficient, and damping coefficient increase. As the pressure ratio increases, the lift force and leakage of the segmented annular seal significantly increase while the stiffness and damping coefficients decrease. As the depth and width of the pocket increase, the lift force, stiffness coefficient, and damping coefficient of the segmented annular seal first increase and then decrease. As the length of the pocket increases, the lift force, stiffness coefficient, and damping coefficient of the segmented annular seal increase. The influence of the pocket depth, width, and length on the leakage is minimal. 

Investigation of static and rotordynamic characteristics of the segmented annular seals based on the differential quadrature method

Study on adaptive concentric performance of floating self-concentric seals

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