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In this study, the alkaline hydrothermal ferric carbon (AHFC), which was prepared by hydrothermal liquefaction method using Fenton iron sludge with NH3·H2O, was used as a skeleton materials for the dewatering of sewage sludge (SS) via thermal hydrolysis. NH2 functional group presented in the AHFC and nano-sized γ-Fe2O3 was anchored on the surface of AHFC. The NH2 functional group notably promoted thermal hydrolysis of SS from the increasing of TOC and TN value. γ-Fe2O3 showed adsorption effect to the water, resulting in decline of the dewatering rate of SS in present condition. When 100% of AHFC was added, dewatering rate of SS was decreased by 19.93% (at 160 °C), 4.50% (at 180 °C) and 8.34% (at 200 °C) respectively. 3D-EEM results showed that the degree of hydrolysis was deepened when AHFC was added for the intensity of soluble microbial products decline. AHFC promoted the decomposition of protein to form heterocycle compounds in the resulting cake according to in situ FTIR results. The nano γ-Fe2O3 catalysis to cake also can be observed for the activation energy was lower than blank in the range of 40˜60%. The study demonstrated concept and the effectiveness the reuse/recycle of the Fenton iron sludge for dewatering of SS.

This study aims to improve the understanding of sources of diesel spray variation, especially employing split injection strategies. The formation and evolution of residual air bubbles and diesel inside the optical real-size diesel nozzle at start and end of injection are successfully captured by a high-speed camera coupled with a micro lens. The corresponding shot-to-shot variations of near-nozzle spray structures are simultaneously obtained by the optical experiments. Furthermore, the numerical models are validated against the experimental results of various near-nozzle spray patterns. Then, the validated numerical models are employed to further investigate the effects of the distributions of the residual air bubbles and initial diesel inside the nozzle on near-nozzle spray patterns. The results indicate that various spray structures are attributed to the interaction between the residual air bubbles and initial diesel, and the radial propagation of the initial jets caused by the air drags. In addition, different positions and sizes of the stagnant air bubbles and diesel exert significant effect on the near-nozzle spray patterns through the mechanisms of the mushroom-like structure and tail.

Gasoline compression ignition mode is one of the low-temperature combustion strategies using gasoline instead of diesel fuel and it is better than the other low-temperature combustion modes in terms of ignition controllability. Difficulty in the ignition at low loads and maximum pressure rise rate during high loads is the main problem in commercializing this engine. In order to solve this problem, hydrogenated catalytic biodiesel is blended with gasoline in different proportions and its combustion and emission characteristics under different working loads are investigated in a single injection mode. Stable combustion is achieved using this gasoline/hydrogenated catalytic biodiesel blends without any combustion assistance and increasing intake temperature. Results show that G70H30 blending fuel illustrates a comprehensively better combustion and emissions performance. However, the high maximum pressure rise rate at high loads and high particulate matter emission are the main problems. Hence, multiple injection strategies are applied for G70H30 to solve the above problem. It reveals that the particulate matter emission for 20% pilot injection ratio is lower than that of single injection mode. The maximum pressure rise rate of 20% or 30% pilot injection ratio can meet the engine limit. While the carbon monoxide and hydrocarbons emissions for double injection mode are higher than that of single injection mode and it increases with increasing pilot injection ratio.

The fast rate of depletion of fossil fuel resources due to increasing demands and the adverse environmental impact by the automotive engines forced researchers to develop alternative strategies to meet the stringent emission norms in terms of oxides of nitrogen and particulate matter. In this regard, low temperature combustion is one of the promising advanced in-cylinder combustion strategies for reducing both oxides of nitrogen and particulate matter emissions simultaneously with a beneficial effect on specific fuel consumption. The low temperature combustion is achieved through homogeneous charge compression ignition, premixed charge compression ignition, reactivity controlled compression ignition and gasoline compression ignition. In this paper, an attempt is made to assemble and summarize a listing of important research articles on low-temperature combustion using a wide variety of conventional and alternate renewable fuels. The effect of low-temperature combustion on engine performance and emission characteristics over a wide range of engine test conditions and the challenges faced in these strategies are also described. From the assemblage of articles on low-temperature combustion using conventional and renewable fuels, it is understood that this strategy can help in achieving better performance, lower cylinder pressure and heat release rate, and simultaneous reductions of nitrogen oxides and particulate matter, but typically with an increase in carbon monoxide and hydrocarbon emissions. This literature review is expected to be useful to the researchers for understanding the concept, challenges, and the state-of-the-art of the different modes of low-temperature combustion using conventional and sustainable alternate fuels.

The mechanisms of primary product formation on catalytic pyrolysis of seaweed sulfated polysaccharide with ZSM-5 were examined in detail by using Py-GC/MS analysis and subsequent density functional theory. Results showed that furfurals were the main product (50.3%) in bio-oil during the catalytic pyrolysis of sulfated polysaccharides. Furfural (9.1%), 5-(Hydroxymethyl)-2(5 H)-furanone (3.1%) and acetone (3.2%) were defined as typical products of Glucuronic acid unit. 5-methyl furfural (41.2%), 5-methyl-2(3 H)-Furanone (0.5%) and 5-methyl furan (5.4%) can be converted from rhamnose unit. The subsequent density functional theory calculation indicated that the catalytic pyrolysis of sulfated polysaccharides by ZSM-5 catalyst could boost the pyrolysis and upgrade the bio-oil quality since the promotion of hydrodeoxygenation on catalytic reactions and ZSM-5 could promote the formation of 5-methyl furfural. The hydrogen bonding and van der Waals force interactions improved the pyrolysis pathways and decreased the energy barrier, which promoted the pyrolysis. This study confirmed that ZSM-5 had a catalytic influence on pyrolysis of sulfated polysaccharides through theoretical and experimental analysis, which is helpful to understand the formation mechanism of seaweed catalytic pyrolysis products.

A numerical and experimental investigation on gasoline compression ignition (GCI) combustion was performed in a heavy-duty diesel engine using gasoline/hydrogenated catalytic biodiesel (HCB) blends. The effects of HCB blended ratio, initial temperature at intake valve closing ( T IVC ) and start of injection (SOI) on performance of the GCI engine were studied in details. Additionally, the differences between GCI and reactivity controlled compression ignition (RCCI) were also explored. The results show that HCB with high reactivity initiates the combustion of gasoline with lower reactivity, and HCB blended ratio, T IVC and SOI have remarkable impacts on thermodynamic state of the fuel/air mixing and then engine performance. As HCB blended ratio increases, the engine noise, carbon monoxide (CO) and unburned hydrocarbon (HC) emissions can be effectively suppressed with the penalties of the increased nitrogen oxides (NOx) and soot emissions. Retarded SOI results in a stable combustion, lower CO emissions while higher NOx emissions. Overall, the optimized operation range of GCI combustion is mainly limited by the engine noise, which can be relieved by multiple injection. In addition, the RCCI produces much lower engine noise compared to the GCI. However, the RCCI is more sensitive to T IVC with worse fuel economy.

In diesel engines, the cavitating flow in nozzles greatly affects the fuel atomization characteristics and then the subsequent combustion and exhaust emissions. In this paper, with the needle lift curve on the basis of injection rate experimental data, a moving mesh generation strategy was applied for 3D simulation of the nozzle cavitating flow. Based on the third-generation synchrotrons of Shanghai Synchrotron Radiation facility (SSRF), a high-precision three-dimension structure of testing nozzle with detailed internal geometry information was obtained using X-ray radiography for a more accurate simulation. A flow visualization experiment system with a transparent scaled-up vertical multi-hole injector nozzle tip was setup. The experimental data was obtained to make a comparison to validate the calculated results and good qualitative agreement was shown between them. Afterward, the effects of needle movement on development of the cavitating flow and flow characteristics parameters were investigated. Finally, the influence of fuel temperature on development of the cavitating flow was also studied. Research of the flow characteristics for the diesel and biodiesel revealed that the flow characteristics of the biodiesel with a temperature rise of between 50 K and 60 K in injector nozzles will be similar to those of the diesel fuel.

A commercial kitchen is a complicated environment where multiple components of a ventilation system including hood exhaust, conditioned air supply, and makeup air systems work together but not always in unison. And the application of an appropriate ventilation system is extremely vital to keep the catering kitchen comfortable, which consequently promotes the productivity and gains. Application of two systems (traditional mixing ventilation system and thermal displacement ventilation system) is compared in a typical kitchen environment using computational fluid dynamics modeling which was used to investigate the difference between mixing and displacement ventilation (DV). It was reported in two parts, one on thermal comfort and the other one on indoor air quality. The results show that DV can maintain a thermally comfortable environment that has a low air velocity, a small temperature difference between the head and ankle level, and a low percentage of dissatisfied people, and may provide better IAQ in the occupied zone. So it was persuasive that using thermal displacement ventilation in kitchen environment allows for a reduction in space temperature without increasing the air-conditioning system capacity.

Mixture working fluids can reduce effectively energy loss at heat sources and heat sinks, and therefore enhance the organic Rankine cycle (ORC) performance. The entropy and entransy dissipation analyses of a basic ORC system to recover low-grade waste heat using three mixture working fluids (R245fa/R227ea, R245fa/R152a and R245fa/pentane) have been investigated in this study. The basic ORC includes four components: an expander, a condenser, a pump and an evaporator. The heat source temperature is 120 &deg, C while the condenser temperature is 20 &deg, C. The effects of four operating parameters (evaporator outlet temperature, condenser temperature, pinch point temperature difference, degree of superheat), as well as the mass fraction, on entransy dissipation and entropy generation were examined. Results demonstrated that the entransy dissipation is insensitive to the mass fraction of R245fa. The entropy generation distributions at the evaporator for R245/pentane, R245fa/R152a and R245fa/R227ea are in ranges of 66&ndash, 74%, 68&ndash, 80% and 66&ndash, 75%, respectively, with the corresponding entropy generation at the condenser ranges of 13&ndash, 21%, 4&ndash, 17% and 11&ndash, 21%, respectively, while those at the expander for R245/pentane, R245fa/R152a and R245fa/R227ea are approaching 13%, 15% and 14%, respectively. The optimal mass fraction of R245fa for the minimum entropy generation is 0.6 using R245fa/R152a.

The multi-holes orifice plate are simple hydrodynamic devices which can be used for intensification of liquid-liquid heterogeneous micro-mixture for preparing bio-diesel or emulsified diesel. In this study,a flow visualization experiment system with a transparent hydrodynamic cavitation reactor was setup to investigate the cavitation in the orifice plate and the outlet of the orifice plate. The effect of upstream pressure and cavitation number were investigated. The experimental results show that with the increasing of upstream pressure the caviation occurs in the orifice plate and the outlet of the orifice plate which are correspond with the numerical results.The numerical results also show that cavitation cloud shedding are the source of the cavitation of the outlet of the orifice plate.

The pyrolysis mechanisms of the main components of seaweed (soluble polysaccharides, proteins, and ash) were investigated in this study using characterization analysis and thermogravimetric analysis–mass spectrometry. XPS analysis indicated that most of the metal ions existed in the ash, while substituents of Na and K ions were found in polysaccharides. Oxygen-containing functional groups in Enteromorpha were found to exist mainly in the following forms: -OH/C-O in polysaccharides, COO- in proteins, and inorganic oxygen in the ash. Pyrolysis thermogravimetric (TG) curves of the components of Enteromorpha indicated that the thermogravimetric analysis ranges of polysaccharides and proteins were 175–310 °C and 300–350 °C, respectively. During the pyrolysis process, due to the effects of metal ions, the maximum thermal weight loss rate was found to increase, while the pyrolysis temperature also increased. CO2 was generated from the decarboxylation of uronic acids and the decomposition of inorganic carbonates ...

In diesel engines, the cavitating flow in nozzles greatly affects the fuel atomization characteristics and then the subsequent combustion and exhaust emissions. At present the biodiesel is a kind of prospective alternative fuel in diesel engines, the flow characteristics for the biodiesel fuel need to be investigated. In this paper, based on the third-generation synchrotrons of Shanghai Synchrotron Radiation facility (SSRF), a high-precision three-dimension structure of testing nozzle with detailed internal geometry information was obtained using X-ray radiography for a more accurate physical model. A flow visualization experiment system with a transparent scaled-up vertical multi-hole injector nozzle tip was setup. A high resolution and speed CCD camera equipped with a long distance microscope device was used to acquire flow images of diesel and biodiesel fuel, respectively. Then, the characteristics of cavitating flow and their effects on the fuel atomization characteristics were investigated. The exper...

The large eddy simulation was applied for the internal turbulent flow in diesel nozzles. Computational results were compared with those obtained from RANS(RNG k~e ) model. The influence of the meshing size on the simulation results were studied. The results showed that the meshing size has little effect on the flow structure when the model is adopted. Compared to the k~e model, the LES model results showed the obvious asymmetry and more complex turbulent flow structure. Furthermore, the LES model can capture a much wider range of vertical structures than the k~e model.

As an important component of the internal combustion engine intake system, the air filter directly affects its performance. Numerical simulation of the aerodynamics and acoustic characteristics for the air filter are carried out in this study. Afterwards, when the inlet pipe is extended to inside of the filter for structural optimization, the influence of it on the flow resistance loss, the filter flow uniformity and transmission loss is analyzed. The simulation results show that the flow loss will decrease and transmission loss will increase, while the flow resistance will also decrease, when the inlet pipe is extended. With the increase of the extended length, the filter flow uniformity will go down. The length of the extended pipe will efficiently reduce the noise of different frequency bands.

The swirling turbulent non-premixed methane flame, was numerically simulated with the Renormalization Group (RNG) k~e model of the Fluent software. The predicted distribution of temperature, concentrations of species, as well as the recirculation zone all agree well with experimental data got from the Sandia National Lab. , USA, which further verify the RNG model's reliability. The influence of the different swirl numbers on the shape of flame, concentrations of species and emission of NO was also investigated. It is found that, the temperature is low in the center of outlet of the swirling burner and tend to high at downstream locations, while the concentrations of CO2, CO, H2O and H2 follow a similar distribution to the temperature profiles. Increasing the swirl number increases the turbulent mixing rates in the primary recirculation zone, but leads to higher levels of NO.

With the spray combustion visualization test unit, researches have been made on the spray development process under different injection pressures with STD nozzles, VOC nozzles and IMPROVED nozzles of diesel engines. The result shows that with the rise of injection pressure, the spray cone angle increases slightly, and corresponding to the same injection moment, the penetration enlarges accordingly with the rise of injection pressure. The cone angle is narrow for STD type, while it becomes wider for VCO type, but meanwhile the penetration decreases and the spray shape is sharply changed. The IMPROVED nozzle combines features from both STD and VCO nozzles, promising the excellent performance of STD nozzle with virtually no penetration decrease and spray shape change.

The centrifugal pump is one of the most widely used pumps. Lower efficiency, worse cavitation performance and stronger unsteady flow are three main problems for the low-specific-speed centrifugal pumps. Due to unsteady flow within pumps, pressure is fluctuant, which further induces vibration and noise. For a centrifugal pump with different impellers, its characteristics of unsteady flow are also different. In this paper, five different impellers were designed adopting low-specific-speed design method, splitter-blades design method and velocity-coefficient method with a set of performance parameters (Q = 25m3/h, H = 10m, n = 1450r/min). 3D unsteady turbulent flow field within the centrifugal pump was simulated. The periodic fluctuation phenomenon and the unsteady flow characteristics were investigated. The static pressure fluctuation in the volute and at the volute outlet and the instantaneous head changes were showed for the pumps with five different impellers operated at design and off-design conditions. The pressure fluctuation is the strongest near the tongue and is slighter at the volute outlet section. The transient head fluctuation increases with the flow rate. The transient head fluctuation of the pump with the low-specific-speed designed impeller is the biggest, while that of the pump with the normal-designed impeller is the smallest. Among the three splitter-blade impellers, the transient head fluctuation of the impeller with splitter blades leaned to the corresponding suction side of the long blades is the smallest. Eventually, the different design schemes were evaluated using the unsteady flow analysis. These conclusions from this paper can supply some references for the design of low-specific-speed centrifugal pumps considering its pressure fluctuation and flow-induced vibration and noise.

The presence of cavitation and turbulence in a diesel injector nozzle has significant effect on the subsequent spray characteristics. However, the mechanism of the cavitating flow and its effect on the subsequent spray is unclear because of the complexities of the nozzle flow, such as the cavitation phenomena and turbulence. A flow visualization experiment system with a transparent scaled-up vertical multi-hole injector nozzle tip was setup for getting the experimental data to make a comparison to validate the calculated results from the three dimensional numerical simulation of cavitating flow in the nozzle with mixture multi-phase cavitating flow model and good qualitative agreement was seen between the two sets of data. The critical conditions for cavitation inception were derived as well as the relationship between the discharge coefficient and non-dimensional cavitation parameter. After wards, the testified numerical models were used to analyze the effects of injection pressure, back pressure, cavitation parameter, Reynolds number, injector needle lift and needle eccentricity on the cavitating flow inside the nozzle. Combined with visual experimental results, numerical simulation results can clearly reveal the three-dimensional nature of the nozzle flow and the location and shape of the cavitation induced vapor distribution, which can help understand the nozzle flow better and eventually put forward the optimization ideas of diesel injectors.Copyright © 2010 by ASME

The cavitating flow in nozzle holes is thought to be a very important factor to affect diesel fuel spray characteristics. In order to study the effect of cavitation on the internal flow of diesel nozzle, the 3d numerical simulation of cavitating flow developed fully in holes of a vertical four-hole VCO nozzle with mixture multi-phase cavitating flow model was carried out. The effects of injection pressure, needle lift, hole entrance curvature radius and hole inclination angle on the cavitating flow in nozzle holes were achieved. The investigation shows that the nozzle discharge coefficient depends mainly on cavitation number rather than on Reynolds number and the nozzle geometry heavily affects critical cavitation number, while injection pressure and needle lift has weaker effect on it.

In this study, combustion experiments of green algae granulations (Enteromorpha clathrata) (EN) were carried out in a bench-scale fluidized bed. The particle diameter was kept constant during the combustion process and combustion model was described as a shrinking core model. Model was divided into water ball, volatile-matter ball, and carbon ball. Ash ball radius was assumed to be the same during the combustion and carbon ball was burned layer by layer. Simulation of single-particle combustion process consists of process of water evaporation, release of volatile matters and combustion, and the process of char combustion. Finally, a mathematical model was established for the combustion of EN single particle in the fluidized bed, validated by the experiment data. The model can be applied for the design of the combustion devices for the combustion of seaweed particles with high content of ash.