Optimal Mixture Ratio Research Articles

Research and Application of Slag–Nanosilica Stabilizer for Silt Subgrade

With the rapid development of construction and road engineering, the accumulation of silting waste soil is becoming more and more serious. In order to recycle the silt, a new type of stabilizer was developed in this study to improve its mechanical properties and applicability on roads. The optimal ratio of stabilizer components was determined by orthogonal test and grey correlation analysis. The effects of stabilizer on the macroscopic mechanical properties of silt were investigated by unconfined compressive strength (UCS) test and split test. The water stability test and freeze–thaw cycle test were carried out to study the durability and road performance of stabilized soil. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods were used to study the effect of the stabilizer on the microstructure and mechanism of silt. The results showed that the optimal mixture ratio of the new type of stabilizer was quicklime: nanosilica: slag = 32:3:65. Adding 10% stabilizer is a reasonable and effective method to strengthen silt, which has the characteristics of high strength and strong durability in the early period. The addition of stabilizer will result in hydration reaction, pozzolanic reaction, and cation exchange on the surface of soil particles with silt, which will enhance the intermolecular force of soil particles, reduce the porosity of soil, and strengthen the connection between soil particles.

Effects of co-substrates’ mixing ratios and loading rate variations on food and agricultural wastes’ anaerobic co-digestion performance

Tunisia is one of the developing countries which faces crucial challenges, the most prominent of which are the production of organic waste, the need for an appropriate waste treatment, and the demand for water and energy conservation. To this end, the present research was designed to develop a technical concept on closed cycle “biowaste to bioenergy” treating food waste (FW) through combined biological processes. In this approach, semi-continuous anaerobic co-digestion (ACoD) of FW, wheat straw (WS), and cattle manure (CM) was tested to investigate the relationship between the effect of the feedstock mixtures and C:N ratio on biogas and digestate generation at different organic loading rates (OLRs) ranging from 2 to 3.6 kg VS/m3.d. Results showed that the mono-digested FW was optimal and reached 565.5 LN/kg VSin at an OLR of 2.4 kg VS/m3.d, and then a drop of biogas production was recorded. However, for co-digested substrates, the optimum mixture ratio was FW:CM 75:25, where 62%, 39.89%, 91.26%, 130.9%, and 119.97% of the biogas yield improved for OLRs ranging from 2 to 3.6 kg VS/m3.d, respectively. Admittedly, the target of this work was to enhance the ACoD process, but it also examined the exploitation of different AD effluents. Therefore, special attention was paid to the generated digestates to decide how it can be efficiently upcycled later. Thus, the closed cycle “biowaste to bioenergy” treatment met two of the major Tunisian concerns: efficient organic waste management and sustainable bioenergy production.

Use fly ash for the production of lightweight building materials

Fly ash is a waste byproduct of thermal power plants or steel plants with a low density. Study on using fly ash to produce lightweight construction materials will is a new application of this material resource. Pha Lai fly ash is a byproduct from Pha Lai Thermal Power Joint Stock Company, in which the main mineral component was mullite (15-20%), quartz (14-16%), carbon (5-7%). The content of the amorphous component was about 67-73%. The chemical composition of Pha Lai mainly was SiO2 (51.73%), Al2O3 (23.22%), Fe2O3 (4.23%). To fabricate the lightweight material from Pha Lai fly ash, the fly ash was mixed with additive materials to create binders following two ways: (1) lime + fly ash and (2) geopolymer technology. For the way of lime + fly ash, with the optimal mixture ratio was fly ash:lime: water = 10:2:1, the lightweight material samples had the bulk density of 1.32g/cm3, the compressive strength of 3.91 MPa, satisfied the Vietnamese standard TCVN 6477-2011 for concrete bricks. Applying the geopolymer technology, with the optimal mixture ratio was fly ash: NaOH/Na2SiO3: Al powder = 100:45:0.15, NaOH/Na2SiO3 ratio = 1:2, the lightweight materials obtained the bulk density of 0,62g/cm3, the compressive strength of 1,54 MPa, satisfied the Vietnamese standard TCVN:9029-2017 for Lightweight concrete - Foam concrete and non-autoclaved concrete products-specification.

Sonosynthesis and characterization of konjac gum/xanthan gum supported ironoxide nanoparticles

In this study, an optimized method was developed for the synthesis of biological macromolecule blend supported iron oxide nanoparticles (IO NPs). The nanostructure was composed of binary polymer blends of konjac gum (KG) and xanthan gum (XG). The synthesized KG/XG@IO NPs were characterized by SEM, EDX, HRTEM, FTIR, XRD, XPS, zeta potential, DLS, TGA, and DSC. According to results, the KG/XG@IO NPs had a spherical shape with an average diameter range of ~40 nm using Scherrer's equation and Williamson-Hall equation. The results of TGA and DSC analysis confirmed that the KG/XG@IO NPs maintained good thermal stability. Our motivation was to determine the effect of the biopolymer blend matrix on the morphology, size, stability, and thermal properties of the green KG/XG@IO NPs. Furthermore, the effects of sonication process time (10–30 min), mass ratio of biological macromolecule blend (KG/XG) (1:1, 1:2, and 1:4), and amplitude frequency (5%–40%) on the rheological parameters of NPs were investigated to optimize the sonochemical process. From optimization analysis, we concluded that the sonication had a role in the size distribution and the formation of nanoparticles with the optimum mixture ratio of binary biopolymer matrix as it provided long-term stability.

Study on the Properties of an Ecotype Mortar with Rice Husks and Sisal Fibers

Adding plant fibers such as rice husks or sisals to the mortar is one of the main methods to reuse the agricultural wastes and reduce the energy consumption of building industry. However, recent research showed some limitation of the mortar mixed with plant fibers. In this paper, sisal fibers and rice husks were added together into cement mortar to investigate its mechanical properties and the optimum mixture ratio of sisal fiber and rice husk by mix ratio test and orthogonal test. The microstructure of the sisal fiber was observed using scanning electron microscopy (SEM) to understand how the properties of the mortar were affected. Results showed that adding sisal fiber and rice husk into cement mortar significantly improved the mechanic property, anticrack performance, and impermeability of the mortar. The highest compressive strength and flexural strength can reach 17.1 MPa and 3.3 MPa. The area of early cracks was reduced by 100%, and the maximum seepage pressure was 0.36 MPa. The microstructure analysis also indicated that adding rice husk and sisal fiber have a positive effect on the mortar. These results support that adding 0.1% volume admixture of 16 mm length sisal fiber with 35% rice husk into mortar is helpful for engineering application.

Experimental Study on Road Base Material of Geopolymer Recycled Concrete

Abstract In order to treat and recycle massive waste concrete, ground waste concrete powder (GWCP) and fly ash (FA) were utilized to produce a geopolymer, a kind of cementitious material. The geopolymer and recycled concrete aggregates (RCAs) were then used to produce geopolymer recycled concrete (GRC), which can be used as a road base material. The feasibility of GRC as a road base material was analyzed by a series of tests, including the mixture ratio test of the geopolymer, road performance test of RCAs, and the tests for mechanical properties of GRC. The test results show that for the geopolymer, the optimum mixture ratio of GWCP to FA was 30/70 (weight/weight), with the concentration of sodium hydroxide (NaOH) solution being 18 mol/L, and the modulus of water glass being 1.5. Except for the slightly large water absorption content, the sludge content, flat and elongated particle content, and the crushing value of RCAs meet the technical requirements for aggregates of road base. The unconfined compressive strength, splitting strength, uniaxial compression modulus, water stability, and dry shrinkage of GRC meet the requirements of the related codes, indicating that it can be used in road base. GRC is not only capable of solving the problems of waste concrete treatment but can also reduce the exploitation of natural stone, the use of cement, and the emission of air pollutants, bringing obvious environmental, economic, and social benefits.

Reduction of COD and ammoniacal nitrogen from stabilized landfill leachate by using green mussel and zeolite as composite adsorbent

ABSTRACT Landfill leachate is a liquid generated due to rainwater percolation through the waste in a landfill or dumping site that may contain high levels of organic matter, both biodegradable and non-biodegradable, which are the major sources of water pollution. Chemical oxygen demand (COD) and Ammoniacal Nitrogen (NH3-N) contents have been relevant indicators of severity and pollution potential of landfill leachate. The reductions of COD and NH3-N were investigated in this study using different combinations of media ratios of green mussel (GM) and zeolite (ZEO). Generally, ZEO is considered as a renowned adsorbent but with a relatively high in cost. In Malaysia, mussel shell is abundantly available as a by-product from the seafood industry, is regarded as waste, and is mostly left at the dumpsite to naturally deteriorate. Its quality and availability make GMs a cost-effective material. In this research study, leachate samples were characterized and found to contain high concentrations of COD and NH3-N. The adsorption process was conducted to find out the best combination media ratio between GM and ZEO. The removing efficiency was determined at different amounts of composite media ratios. The optimal adsorbent mixture ratios between (GM: ZEO) of 1.0:3.0 and 1.5:2.5 were considered as a more efficient technique in removing COD and NH3-N compared to exploiting these adsorbents individually. The optimal extenuation removal reduction was found at an approximately 65% of COD and 78% of NH3-N. The adsorption Isotherm Langmuir model exhibited a better fit with high regression coefficient for COD (R2 = 0.9998) and NH3-N (R2 = 0.9875), respectively. This means that the combination of GM: ZEO adsorption of landfill leachate in this analysis is homogeneous with the monolayer. The mixture of GMs and ZEO was observed to provide an alternative medium for the reduction of COD and NH3-N with comparatively lower cost. Implications: The concentration of organic constituents (COD) and ammoniacal nitrogen in stabilized landfill leachate have significantly strong influences of human health and the environment. The combination of mixing media green mussel and zeolite adsorbent enhancing organic constituents (COD) and ammoniacal nitrogen reduction efficiency from leachate. This would be greatly applicable in future research as well as conventionally minimizing high cost materials like zeolite, thereby lowering the operating cost of leachate treatment.

Optimisation of recycled moulding sand composition using the mixture design method

ABSTRACT In the cast iron industry, mould sand quality and the most efficient recovery of used sand into the system are critical. For this purpose, the optimum values of the factors (humidity, active bentonite and coal dust) affecting the green strength, gas permeability and shear strength of the mould sand were determined in this study. The optimum mixture ratio, which makes the green strength, gas permeability and shear strength of the mould sand the best, was made by using the mixture design method. As a result of the studies, optimum casting sand composition; the percentage of moisture content, the percentage of coal dust, the percentage of active bentonite and the percentage of recycle sand were determined as 3.92%, 0.05%, 0.30% and 95.73%, respectively. The green compression strength(B1) 23.5 N/cm2, shear strength(B2) 7.7 N/cm2 and gas permeability (B3) 91 mmWS of the conventional cast sand prepared in this optimum composition were measured.

Effect of pumice powder and artificial lightweight fine aggregate on self-compacting mortar

An experimental program was conducted to investigate the fresh properties, mechanical properties and durability characteristics of the self-compacting mortars (SCM) produced with pumice powder and Artificial Lightweight Fine Aggregate (aLWFA). aLWFA was produced by using fly ash. A total of 16 different mixtures were designed with a constant water-binder ratio of 0.37, in which natural sands were partially replaced with aLWFA and pumice powder at different volume fractions of 5%, 10% and 15%. The artificial lightweight aggregates used in this study were manufactured through cold bonding pelletisation of 90% of class-F fly ash and 10% of Portland cement in a tilted pan with an ambient temperature and moisture content. Flowability tests were conducted on the fresh mortar mixtures beforehand, to determine the self-compacting characteristics on the basis of EFNARC. To determine the conformity of the fresh mortar characteristics with the standards, mini-slump and mini-V-funnel tests were carried out. Hardened state tests were conducted after 7, 28 and 56 days to determine the flexural strength and axial compressive strength respectively. Durability, sorptivity, permeability and density tests were conducted at the end of 28 days of curing time. The test results showed that the pumice powder replacement improved both the fresh state and the hardened state characteristics of the mortar and the optimum mixture ratio was determined as 15%, considering other studies in the literature. In the aLWFA mixtures used, the mechanical and durability characteristics of the modified compositions were very close to the control mixture. It is concluded in this study that mixtures with pumice powder replacement eliminated the negative effects of the aLWFA in the mortars and made a positive contribution.

Reciprocating friction and wear performances of nanometer sized‐TiO2 filled epoxy composites

AbstractNanometer‐sized particles, for example, TiO2, have gradually gained the attention to improve the mechanical and tribological properties of epoxy composite coatings. In the present paper, TiO2 with the size of 300 nm was applied to improve the reciprocating friction and wear performances of an epoxy composite. The effects of TiO2 content and sample preparation methods on the mechanical and tribological performances were investigated experimentally. It was found that the optimal mixture ratio of TiO2 was 4 wt%, and the tensile strength of composite increased by up to 30% compared with the control sample. The TiO2 nanoparticles were treated with polyvinylpyrrolidone (PVP) and then mixed into epoxy resin with three‐roll mill grinding technique. The PVP molecules could surround a single TiO2 to form super‐monomer, which produced repulsive force to aim to disperse nanoparticles, and the three‐roll mill grinding could utilize the compression of axis surfaces and friction at different speeds to reduce the size of agglomerations of more than 5 microns. The results showed that the PVP molecules treatment could improve tensile strength and modulus, and three‐roll mill grinding technique could enhance the elongation at break. In addition, the reciprocating wear rate and frictional coefficient of the epoxy composite plates also were reduced remarkably owing to the pretreatment of TiO2 particles, for example, and the frictional coefficient of epoxy composite decreased from 0.09 to 0.04 for the optimal ratio of TiO2, and special wear rate also decreased by 87.5% compared with the control sample. This was because the TiO2 nanoparticles acted as the stress transfer medium and could undertake part of loading to relieve stress directly into the epoxy matrix. There was a thin transfer film in which the particles acted as a membrane skeleton to avoid matrix further being torn. Because of the hardness and nanoeffect of particles, TiO2 could fill the defects in the wear interface to form a protective film and improve surface fatigue resistance property. The more uniform dispersion of TiO2 particles brought about the obvious improvement of wear resistance of composites.

Sustainable Implementation of Glass Manufacturing Waste and Geogrids in the Improvement of Fine-Grained Soils

Recently, utilization of wastes has become increasingly important in aspects of sustainability and waste disposal. The aim of this study is to investigate the feasibility of using glass manufacturing waste (GMW) for the first time in the relevant literature, geogrids and GMW-geogrid reinforcement to increase the load bearing capacity of a clayey soil (CS) by large-scale model experiments. Initially, optimum water ratios were determined for different ratios of GMW and CS. Secondly, the optimum mixing ratio of GMW was determined. Next, the optimum soil depth improved with GMW and the optimum number of geogrids were investigated. Consequently, a bearing capacity ratio (BCR) increase of 2.23 times was acquired and the optimum mixture ratio was attained for 25% GMW addition. Improvement depth (Rd) and optimum number of geogrids (N) were obtained as 1.75D (D: diameter of the model foundation) and 3, respectively. The highest degree of improvement was reached for geogrids-GMW combination and a minimum waiting period of 7 days was advised in the sequel of such soil improvement work. Out of the observation of micro-structural analyses results, both physical and chemical interactions were encountered throughout the occurrence period of bearing capacity improvements.

Experimental Investigation on the Mixture Ratio and Diffusion Performance of Grouting Materials for Water Bursting Prevention in Coal Mines

Grouting is a common and important technique for water bursting prevention in coal mines; the success of grouting in coal mines depends highly on the flowability of grouting materials and the strength of the hardened body as well. In this paper, a series of performance tests, in terms of the water‐cement ratio, viscosity, drainage rate, presetting time, final setting time, compressive strength, and permeability were conducted on the cement‐fly ash‐based grout at various mixture ratios. The evolution of these performances versus different mixture ratios was analyzed; targeting at the reasonable flowability and hardened strength of grouting materials, an optimized mixture ratio was recognized for water bursting prevention in coal mines. Furthermore, the diffusion experiments of optimized grout material were designed taking into account the influence of confining and hydraulic pressure in the porous medium. As a result, the confining and hydraulic pressures have a linear negative correlation with the diffusion distance of grout materials. These results have guiding significance to water bursting prevention in coal mines.

Research on Ignition Property of Reduced-Toxicity Hypergolic Bipropellant

Ignition property of reduced-toxicity hypergolic bipropellant was investigated under the condition that various parameters such as concentration, mixture ratio, propellant temperature were changed. 3-Methylaminopropylamine doped with sodium borohydride was used as a fuel, and propellant grade hydrogen peroxide was used as an oxidizer. As a result, it was found that this bipropellant has two ignition mode. Under the condition that concentrations of hydrogen peroxide and sodium borohydride are higher than certain values, ignition delay times are less than 4msec and do not depend on mixture ratio. On the other hand, ignition delay times become larger as mixture ratio increases under the condition of lower concentration. Even in the former ignition mode, it was observed that the growth of flame almost stopped for a while just after ignition under the high mixture ratio conditions. It was also found that temperature of hydrogen peroxide has some effect on ignition delay time, whereas that of fuel has little effect. Considering from these experimental results, ignition model formed by three phases was proposed. In this model, the cooling effect by unreacted hydrogen peroxide in condensed phase is considered to have potent effect on ignition delay time and post ignition behavior. This feature is caused by high optimum mixture ratio and exothermic self-decomposition property of hydrogen peroxide.

The Effects of Concentration Ratios on the Particle Size of CHI-ALG-CaCl2 Nanocarriers

Nanotechnology is highly desirable in numbers of industry including cosmeceutical and pharmaceutical. However, the nanoparticle size is greatly varied by the method of synthesising them such as the addition of calcium chloride. Hence, the present study was carried out to investigate the effect of calcium chloride concentration on nanoparticle size when added to the chitosan and alginate nanocarriers. For this purpose, we have performed the preliminary study on the antioxidant activities of Cymbopogon sp. extracts obtained through decoction and infusion method. From this preliminary study, the optimal mixture ratio of extract, including five different ratios of CHI-ALG/CaCl2 nanocarriers which were prepared with ratio of 1:3:0, 1:3:2, 1:3:5, 1:3:10 and 1:3:20 was used to formulate the nanocarrier. Comparing both methods, decoction gives the highest antiradical activity which indicating strong antioxidant potential compared to infusion, are selected to be formulated into nanoparticle. CHI-ALG/CaCl2 nanocarriers were then synthesised to encapsulate antioxidant extracts for topical delivery. Each sample of nanoparticles was evaluated for its size distributions, polydispersity index (PdI) and zeta potential by dynamic light scattering using DelsaMax Pro (Beckman Coulter, USA). The experiment was conducted with five different ratios of CHI-ALG/CaCl2 nanocarriers which were prepared with ratio of 1:3:0, 1:3:2, 1:3:5, 1:3:10 and 1:3:20 in a volume of 50 ml with 1:3:0 acts as a negative control. The best particle size was observed at 1:3:2 mixture ratio with 0.76-fold change (350.47 ± 36.12 nm) from the control (460.03 ± 107.17 nm) which falls in the acceptable range of desirable size of nanoparticles. The nanoparticles produced in this study showed PdI values less than 1, showing good uniformity. The zeta potential value for the all mixture ratios are high (>20 mV) which is able to prevent aggregation of the nanoparticle. As a conclusion, addition of calcium chloride at 1:3:2 to chitosan and alginate has improved the size of nanoparticles containing antioxidant extract of Cymbopogon sp.

Thermo-economic performance and sensitivity analysis of ternary hybrid nanofluids

The thermo-economic performance of the Al2O3-TiO2-Cu/water ternary hybrid nanofluid was investigated experimentally. The shear stress, viscosity, and thermal conductivity were measured at 0.005–1 vol% over temperature range of 20–60 °C. The morphology and stability of nanofluids were characterized by SEM and UV–Vis spectrophotometer analyses. To obtain the optimum nanoparticle mixture ratio, sensitivity analysis of viscosity and thermal conductivity was conducted for 1 vol% mixtures with five different nanoparticle mixture ratios. The results showed that the optimum mixture ratio with the highest thermal conductivity and lowest viscosity was found to be 40:40:20 (Al2O3:TiO2:Cu). Following this, the experimental data were compared with literature data for the corresponding single nanofluids and hybrid nanofluids. Due to different sizes of nanoparticles in ternary hybrid nanofluids, small and densely-packed clusters will result in relatively higher thermal conductivity and lower viscosity compared with single and binary hybrid nanofluids. Economic analysis revealed that Al2O3-TiO2-Cu/water ternary hybrid nanofluids with 0.7 vol% and 1 vol% are the most efficient working fluids in the laminar and turbulent flow regimes, respectively. These results highlight the strong potential of ternary hybrid nanofluids for use in industrial heat transfer applications

Proportion optimization of grouting materials for roadways with soft surrounding mass

ABSTRACT Severe deformation and failure frequently occur in roadways with soft or weak surrounding rock and have greatly influenced safe and efficient mining of coal in many coal mines. Using portland cement, emery and fly ash as main raw materials, through laboratory tests, effect of water/binder ratio, cement/sand ratio, water/sodium silicate ratio, water-reducing agent, fly ash/cement ratio, and various performance indexes of grout of fluidity, viscosity, setting time, bleeding rate, compressive strength, concretion rate, and various performance indexes were systematically analyzed. An optimized mixture ratio of the main raw materials added in the grouting material proportion was determined through uniform design method, an optimal mixture ratio was determined by regression analysis. The results show that: 1) The flow performance is significantly affected by change of sodium silicate and water reducer, the compressive strength of grouting material increases significantly with increase in emery content, and decreases significantly with increase in water reducer. 2) An optimized mixture ratio among water-cement ratio, cement-sand ratio, water/sodium silicate ratio, water-reducing agent, fly ash/cement ratio in the grouting material is 0.75, 1.2, 0.08, 0.03, and 0.18, respectively. Field test demonstrated that the material has better performance in reinforcing weak and broken rock mass.

Leaching assessment of aerated concrete made of recycled shale gas drilling cuttings: Particular pollutants, physical performance and environmental characterization

This research aims to study how feasible it is to apply water-based drilling cuttings (WDC), Phosphogypsum (PG) and fly-ash in a coordinated way in aerated concrete, while also adopting non-autoclaved technology which can greatly save energy consumption. So the physiochemical properties, analysis of the microstructure and the environment performance of the WDC were analyzed. In the meantime, the process of hydration of all products of non-autoclaved aerated concrete including WDC were studied by using XRD, FT-IR and SEM. The findings revealed that the benzene series of WDC is all non-detected, and the heavy metals’ results of single factor index method and potential ecological environment risk were all meet the standard. The contents of heavy metals in WDC are under the level of national standard. As well as, the WDC are rich in calcium, silicon and aluminium, and the particle size is concentrated in 30 μm. This chemical and particle characteristic makes them have the basic conditions as mineral admixtures. So, the optimum mixture ratio of aerated concrete is 2.7-13.6% for WDC, 13.6-27.3% for fly-ash, 20% for cement, 11.8% for quicklime and 1.8% for phosphogypsum, and premise condition is W/S is 0.62, curing temperature and time are 80 °C and 12 h, respectively. The unit weight together with the mechanical properties of the aerated concrete that has 40% WDC (instead of 40% fly-ash) all satisfy the B06, A3.5 GB/T11968-2006 standards. Other tests were carried out to determine its environmental performance. It established that the production of aerated concrete with 40% WDC does not result in any secondary contamination. Also, based on these properties of WDC aerated concrete we propose main technology and process route of the industrial practice.

Assessment of co-composting of sewage sludge, woodchips, and sawdust: feedstock quality and design and compilation of computational model.

Composting process of sewage sludge requires a preprocessing step in order to prepare the appropriate mixture of dewatered sludge (Xs) with amendment (Xa), bulking agent (Xb), and/or recycled materials (Xr). This research aimed to develop a novel mathematical model for finding an optimal mixture ratio of dewatered sludge with the aforementioned influencing elements on co-composting process. Seven feasible scenarios were presented and the best one was selected in viewpoint of technical and economic perspectives. The optimum mixture was prepared and its quality was evaluated in the terms of physical, chemical, and microbial characteristics. The optimum mixture was loaded in an aerated static pile composting reactor in order to evaluate the quality of the final compost product. If the test results were not in compliance with the USEPA standards, the model was iteratively modified to fulfill the desired objective. The model was validated using the experimental results. The mixture of Xs:Xa:Xb:Xr with a weight ratio 7.4:1.0:1.4:2.3 allowed optimal moisture content (59.8 ± 0.5%), organic matter (80.0 ± 2.6%), dry matter (40.2 ± 0.6%), C/N ratio (28.0 ± 1.6), and free air space (> 30%) across the composting pile. The final product of compost met the heavy metal and microbial requirements for land application. It can be concluded this mathematical model is a promising method for selecting the optimal amount and type of materials for preparing the initial mixture of co-composting process.

Effects of the O/F Ratio on the Performance of a Low Thrust LOX/Methane Rocket Engine with an ElecPump-fed Cycle

Recently, electrically driven pump-fed cycle rocket engines (i.e., ElecPump engines) have received considerable attention. ElecPump engines are superior to pressure-fed engines and will likely replace gas generator cycle engines under a 100 kN thrust level. This study focuses on LOX/methane ElecPump engines with a low-thrust level and estimates the nominal operation point of the engine. The objective variable was set to the maximum velocity increment of the stage. The mixture ratio and combustion pressure were explored as the design variables. Thus, the optimal mixture ratio was proposed as the design variable, considering not only the engine weight but also the structural weight.

Effects of long-term acclimatization on the optimum substrate mixture ratio and substrate to inoculum ratio in anaerobic codigestion of food waste and cow manure

The effects of long-term acclimatization on the optimum food waste to cow manure ratio (FW/CM) and substrate to inoculum ratio (S/I) in anaerobic codigestion with FW and CM were investigated by batch trials. For the unacclimated sludge, the highest CH4 yields of 646.6 and 653.4 mL/g VS were achieved under the optimum FW/CM (2.5 VS/VS) and S/I (0.07 VS/VS) ratios, respectively. After more than 550 days of acclimatization, the optimum FW/CM and S/I of the acclimated sludge were improved to 3.4 and 0.68 VS/VS with more anaerobic digestion enzymes and lignocellulose, respectively. Based on high-throughput sequencing analysis, the microbial community structures of bacteria, fungi, and archaea were changed, which was the main reason for the change in the optimum FW/CM and S/I. Therefore, the FW/CM and S/I should be periodically optimized during the long-term operation of codigestion to improve the codigestion efficiency for biogas production.