Relative Pressure Drop Research Articles

Isothermal Flow Field Characterization of a Full-Scale Sector Combustor at Elevated Pressures

Abstract An experimental investigation in a sector (20 deg) of full-scale annular gas turbine combustor is performed. The sector combustor is optically accessible for the flow and flame visualization of the primary and exit zones of the combustor. The distinctive feature of the experimental setup is that it preserves the geometrical details of an annular combustor that includes the casing, dome and combustor liner. The combustor design features a series of primary and secondary dilution holes with multiple film cooling strips on the outer and inner liner. In the present study, the combustor is operated at inlet Mach numbers of 0.02–0.3 at operating absolute pressures of 1–5 bar. Static pressure measurements are performed at multiple locations in the rig to characterize the pressure drop across the combustor. Two-dimensional particle image velocimetry (PIV) is performed to measure the velocity fields of the primary and exit zones of the combustor simultaneously. The results show the presence of a central recirculation zone (CRZ), high-velocity annular jets, and a pair of dilution jets in the primary zone of the combustor. The steady-state flow structures are invariant of inlet Mach number and pressures. The relationship between the relative pressure drop across the combustor and the combustor inlet condition is obtained. Mass flowrate and momentum flux are calculated for the flow through the swirler, central recirculation zone, the primary dilution jets, and the exit zone. The paper shows how the flow structures in a realistic combustor change with variations in global combustor parameters.

Enhanced Transverse Dispersion in 3D-Printed Logpile Structures: A Comparative Analysis of Stacking Configurations

Three-dimensionally printed logpile structures have demonstrated the tunability of the transverse dispersion behavior, which is relevant in the context of chemical reactor design. The current modeling study aims to further investigate the trade-offs in such structures, extending the range of geometries investigated and addressing the limitations associated with the pseudo-2D nature of previous experiments. The relative transverse dispersion coefficient and pressure drop were determined using computational fluid dynamics simulations in OpenFOAM for structures with different stacking configurations, porosities and scaling of the structures’ unit cell along the secondary transverse axis. The latter could not be varied in previous experiments, but the current results demonstrate that this limitation suppresses vortex shedding in structures with high porosity. These vortices significantly enhance the transverse dispersion. By using a staggered stacking configuration on both transverse axes, an earlier onset of this phenomenon could be realized. Importantly, operation in this regime could be achieved without an equivalent increase in pressure drop, offering a favorable operating trade-off. The findings demonstrate that at low Reynolds numbers, the studied structures consistently outperform randomly packed beds of spheres, highlighting their potential for chemical process intensification.

Optimization and mechanistic analysis of the configurational parameters of a serrated trench for improving film cooling performance

Combinations of trench and holes in film cooling design for turbine blades have been suggested recently. In this work, structural optimization is performed for one of our previously proposed serrated trenches. Geometric parameters including serrated angle, width, and height of the trench, which are the key factors affecting the flow and cooling characteristics, are optimized. The relative area-averaged cooling effectiveness, the relative pressure drop coefficient, and the performance evaluation criterion (PEC) are the optimizing objectives. The multi-objective genetic algorithm is employed as the search strategy to achieve PEC maximization at blowing ratios in the range of 0.5–2.0. The individual variations of each parameter are studied by controlling the variables using the response surface method. It shows that the trench height is the most influential factor on flow and heat transfer; while the trench serrated angle mainly affects the heat transfer; and the trench width has a weak effect on both, depending on the blowing ratio. To achieve maximum PEC, the trench height needs to enlarge with the increase in blowing ratio, while contrary to this, the trench width needs to increase under low blowing ratios and decrease under high blowing ratios, and the optimum trench serrated angle is within the range of 80°–85° at all blowing ratios. The optimum geometry reduces the pressure loss while improves the cooling effectiveness by 8.43 %–17.97 % compared to the baseline trench. This work is instructive for the design and application of practical structures for blade cooling.

CFD investigation of structural effects of internal gas intake on powder conveying performance in fuel supply systems for aerospace engines

Optimal design of gas intake in powder fuel supply systems is crucial for performance of aerospace engines. There is little research on the impact of intake structure on powder conveying performance. Three novel internal intakes were proposed, which are spherical, cube-shaped, and dome-shaped. After validation, CFD simulations demonstrate that fluctuation of mass flow rate of powders in the dome-shaped intake is reduced by about 73.3% compared with the annular external one. Variation trends of phase velocities are similar for the spherical and cube-shaped intakes, while those are similar for the annular external and dome-shaped internal intakes. Fluctuation of area of gas zone for the annular external and spherical internal intakes is larger than that for the cube-shaped and dome-shaped internal intakes. Pressure and relative pressure drop in the fluidization chamber have a stable stage, and fluctuation of relative pressure drop is small when dome-shaped internal intake is used.

A correlated multi-observable assessment for vanadium redox flow battery state of charge estimation — Empirical correlations and temperature dependencies

The efficient operation of vanadium redox flow batteries requires the half cell specific monitoring of the state of charge (SOC). Monitoring of the SOC is affected by temperature fluctuations, which need to be distinguished from the SOC signal. Several SOC monitoring approaches have been proposed in the literature and either been evaluated individually or compared to one other approach. The aim of this study is to contribute to SOC sensor development for VRFB by providing a first correlated assessment of several established and new SOC monitoring methods. We perform multi observable measurements of: half cell electrolyte potentials, electrolyte densities, electrolyte volumes, electrolyte viscosity related pressure drops, pH related potentials and UV/Vis absorbances. We determine SOC correlations of these observables in full charge/discharge cycles at constant temperature and derive temperature corrections in additional measurements over a range of 12°C to 32°C at 25%, 50% and 75% SOC. We compare the SOC and temperature sensitivity as well as the accuracy of these monitoring methods at constant and varied temperature. We find that the established half cell electrolyte potentials and UV/Vis absorbances can estimate the SOC at constant temperature with measurement errors of 1.7% and 4%, respectively and with slightly higher errors at varying temperatures. The viscosity related pressure drop and electrolyte density are both suitable for SOC estimation if temperature corrections are included. The pH related potentials for the positive half cell and both half cell electrolyte volumes could be used for a rough SOC estimate, but need accurate temperature corrections and further long term stability evaluation.

An underlying factor of increasing early winter precipitation in the Hokuriku region of Japan in recent decades

AbstractUsing a reanalysis dataset and large‐ensemble simulation results, this study examines a possible factor of increasing trend in early winter precipitation in recent decades in the Hokuriku region of Japan. Monthly precipitation in December has a significant increasing trend after the early 1990s, which is different from those in January and February. The increasing precipitation in December is related to that in the sea surface upward latent heat flux due to intensified winter monsoon circulation and warming sea surface temperatures (SSTs) over the Sea of Japan. December averaged SSTs show a trend pattern in recent decades that is similar to the negative phase of the interdecadal Pacific oscillation (IPO), accompanied by positive trends from the eastern Indian Ocean to the western tropical Pacific. The enhanced trend of convection over the Bay of Bengal is seen; suggesting a combined effect of climatologically high SSTs and IPO‐related warmed SSTs over the region. Trends in recent decades of an upper‐level wavy pattern from South Asia to near Japan along the subtropical jet associated with enhanced convection near the Bay of Bengal and the related pressure drop from Japan to the north are seen, which contribute to intensified winter monsoon circulation.

Flow boiling pressure drop correlation in small to micro passages

An accurate and acceptable correlation for the prediction of two-phase pressure drop is considered a crucial step in heat exchanger design. Although many existing models and correlations were developed and proposed in the past, their ability to predict within acceptable error bands when applied in general to flow boiling flows is limited, even within their originally recorded ranges. The discrepancies are worse when predicting two-phase pressure drop in small to micro-scale passages. Therefore, the aim of the work described in this paper is to assess the most well-known models and correlations using a large experimental data-bank. The data-bank includes four refrigerants, namely R134a, R245fa, HFE-7100 and HFE-7200, small to micro heat exchangers made of different metals and different channel configurations. In addition, the data cover a large range of operating conditions, which can allow generally applicability of new correlations developed. This range covers channel hydraulic diameter of 0.46−4.26 mm, heated length of 20−500 mm, system pressure of 1 − 14 bar, mass flux of 50−700 kg/m2 s, wall heat flux ranging from 2 to 234 kW/m2 and exit vapour quality up to one. Twenty six existing models and correlations that were developed and proposed for vertical/horizontal flow, single/multi-channels and circular/non-circular channels were evaluated. Moreover, the effect of using different equations for calculating the two-phase mixture viscosity, void fraction, Fanning friction factor and Lockhart–Martinelli parameter was assessed and discussed. The mean absolute error of the existing correlations when compared with our data-bank was more than 30 %. Therefore, a new correlation for calculating the two-phase multiplier, which was strongly dependent on the Boiling number and the Lockhart–Martinelli parameter, was developed and then the frictional component and total two-phase pressure drop relationships were completed.

Modelling and optimization of a forced convection heat exchanger for Mars waste heat rejection for power cycle and cryocooling applications

A forced convection heat exchanger for waste heat rejection to the Martian atmosphere is modelled for both a power generation and cryogenic refrigeration application. The modeling is based on existing as well as recent, experimentally validated heat transfer and pressure drop correlations for low-Reynolds-number, moderate-Knudsen number finned tube arrays and represents the first detailed examination of optimal heat exchanger design and performance in this regime. These correlations were developed from heat exchanger performance data taken in Mars-like conditions and are described in a separate, companion work [1]. A heat exchanger model based on the effectiveness-NTU method is developed using these correlations and the heat exchanger geometry is optimized using an open-source solver to minimize the overall system mass for a range of candidate heat exchanger materials and heat transfer rates. The optimal heat exchangers generally consisted of shallow, staggered banks of 1–2 mm diameter tubes and 2–4 mm fin spacing, although in some conditions bare tube arrays were optimal. These geometries tended to be preferred due to their low relative pressure drop, a necessity given the power requirement of producing high pressure head in the thin atmosphere. Curve fits that capture the heat exchanger performance are generated based on the input conditions in order to develop a reduced order model that can be used to integrate the heat exchanger model with an existing recuperated Brayton cycle high-temperature gas cooled reactor (HTGR) power cycle model. This power cycle model is used to determine the impact of using convective heat rejection on optimal system mass and compare this approach to radiative heat rejection. For a 40 kWe power output, the optimal overall cycle mass is found to decrease by 78 % when using convective heat rejection compared to a radiator; this is due to the decreased mass of the heat rejection system as well as the lower optimal rejection temperature which results in a lower recuperator mass. The heat exchanger itself has a mass of only 37 kg, a frontal area of 12.7 m2, and requires 2134 W of fan power to operate. The system is shown to perform well over a wide range of Mars ambient conditions. A high-power liquid Oxygen (LOx) reverse Brayton cryocooler cycle is also modeled to determine the benefit of using convective heat rejection for in-situ resource utilization (ISRU) applications. Across a range of power source options and ambient temperatures, using a convective heat rejection system reduced total system mass by up to 43 % and frontal area by up to 95 % compared to a radiator and also reduced the mass-optimal cycle power draw by increasing the optimal cycle efficiency. However, the magnitude of the mass reduction depends strongly on the specific power of the electrical source; the forced convection system provides only a 7 % improvement over a radiator when coupled with a photovoltaic power source due to the increased power demand of the fan. Overall, this technology offers significant performance advantages over radiative heat rejection systems for waste heat rejection applications on Mars and therefore may significantly benefit future crewed Mars missions.

Power and efficiency optimizations for an open cycle two-shaft gas turbine power plant

In finite-time thermodynamic analyses for various gas turbine cycles, there are two common models: one is closed-cycle model with thermal conductance optimization of heat exchangers, and another is open-cycle model with optimization of pressure drop (PD) distributions. Both of optimization also with searching optimal compressor pressure ratio (PR). This paper focuses on an open-cycle model. A two-shaft open-cycle gas turbine power plant (OCGTPP) is modeled in this paper. Expressions of power output (PP) and thermal conversion efficiency (TCE) are deduced, and these performances are optimized by varying the relative PD and compressor PR. The results show that there exist the optimal values (0.32 and 14.0) of PD and PR which lead to double maximum dimensionless PP (1.75). There also exists an optimal value (0.38) of area allocation ratio which leads to maximum TCE (0.37). Moreover, the performances of three types of gas turbine cycles, such as one-shaft and two-shaft ones, are compared. When the relative pressure drop at the compressor inlet is small, the TCE of third cycle is the biggest one; when this pressure drop is large, the PP of second cycle is the biggest one. The results herein can be applied to guide the preliminary designs of OCGTPPs.

Enhancing radiative efficiency in MHD micropumps using plasma-infused hybrid bioconvective nanofluids for advanced radiative oncology at tertiary level

This research paper investigates the optimization of radiation performance of a plasma-based bioconvective nanofluid integrated Magneto-hydrodynamic (MHD) micropump for radiative oncology. It addresses a literature gap by analysing the radiative impact of blood-based hybrid nanofluids in MHD micropumps. Three blood-based bio-convective radiating hybrid nanofluids—blood—Pt, blood—Au and blood—MWCNT are studied to understand their radiation behaviour in MHD pump while being employed as transportation medium. The investigation employs two non-dimensional parameters, namely Rd (Radiation number) and Ha (Hartmann number), to examine the fluid dynamics, magnetic characteristics, and electrical properties of the MHD micropump. The temperature gradient, velocity distribution, and pressure drop along the flow channel are examined within the specified range of Rd and Ha. Magnetic flux density (MFD) and electric flux intensity (EFI) are evaluated to understand nanoparticle behaviour during drug delivery and blood transportation. Findings highlight that MWCNT and Pt are the most efficient bioconvective nanoparticles for plasma transportation under high radiative conditions. MWCNT-based blood flow exhibits desirable characteristics, including sufficient intake pressure of 4.5 kPa and minimal relative pressure drop of 34%. Coherence between radiation flux and electromagnetic flux reduces pumping power and ensures uniform heat dissipation for improved drug delivery. Au nanoparticles provide moderate magnetic flux density with least fluctuation within the range of Ha and Rd number (2.57 T to 4.39 T), even in highly radiative environments (such as—Rd = 4, Rd = 5), making them suitable for applications like embedded chemotherapy or cell treatment. Au nanoparticles maintain moderate electrical flux intensity with a minimal drop of 16nA, particularly at higher radiative environments influenced by the Radiation number (Rd = 4 to Rd = 5) while Ha values from Ha = 2 to Ha = 4. Conclusively, it has been identified that MWCNT and Au are superior nanofluids for advanced radiative oncological treatments. These nanofluids have the potential to enhance plasma transportation, thermal regulation, and aetilogical disease management. The present study provides significant findings on enhancing the radiation performance in MHD micropumps through utilization of blood-based hybrid nanofluids, thereby offering potential advantages to the domain of biomedical engineering.

Aerodynamic effect on atomization characteristics in a swirl cup airblast fuel injector

To investigate the influence of swirling air flow field on the spray characteristics and the droplet behaviors of the swirl cup airblast fuel injector, a single swirler cup and a double swirlers cup airblast injector were operated in a wide range of fuel mass flow rates (mf) and relative air pressure drops (ΔPa). Various laser based diagnostics, including planar Mie scattering, phase-Doppler particle analyzer, and high speed particle imaging velocimetry, were employed to provide the information of spray angle, droplet Sauter mean diameter (SMD), droplet velocity, and air flow velocity. The results show that the air flow field was characterized by central toroidal recirculation zone (CTRZ), the double swirlers cup airblast injector generated stronger CTRZ than single swirlers cup airblast injector. The spray characteristics and the droplet behaviors with different size classes were significantly affected by the air flow field. The larger droplets (25–100 μm) with higher initial momentum were likely to keep its velocity when passing through CTRZ, when the mf increased, more large fuel droplets could pass through the CTRZ and expanded to both sides, resulting an increase in a spray angle. On the other hand, smaller droplets (<25 μm) with lower initial momentum were trend to be enrolled by the CTRZ; therefore, the spray droplets at lower mf were confined in the CTRZ. These droplets trend to coalesce with each other resulting in an increase of SMD in this region.

Hydrodynamics of finite-length pipes at intermediate Reynolds numbers

Extensive studies of the hydraulics of pipes have focused on limiting cases, such as fully-developed laminar or turbulent flow through long conduits and the accelerating flow through an orifice, for which there exist laws relating pressure drop and flow rate. We carry out experiments on smooth, circular pipes for dimensions and flow rates that interrogate intermediate conditions between the well-studied limits. Organizing this information in terms of dimensionless friction factor, Reynolds number and pipe aspect ratio yields a surface$f_D(Re,\alpha )$that is shown to match the three laws associated with developed laminar, developed turbulent, and orifice flows. While each law fails outside its applicable range of$(Re,\alpha )$, we present a hybrid theoretical–empirical model that includes inlet, development and transition effects, and that proves accurate to approximately 10 % over wide ranges of$Re$and$\alpha$. We also present simple formulas for the boundaries between the three hydraulic regimes, which intersect at a triple point. Measurements show that sipping through a straw is an everyday example of such intermediate conditions not accounted for by existing laws but described accurately by our model. More generally, our findings provide formulas for predicting frictional resistance for intermediate-$Re$flows through finite-length pipes.

Improved quantitative evaluation of the fouling potential in spacer-filled membrane filtration channels through a biofouling index based on the relative pressure drop

In this study, a biofouling index based on the relative pressure drop is presented to quantitatively evaluate the amount of fouling in spacer-filled membrane filtration channels. The biofouling index was defined as the inverse of the time to reach a relative pressure drop of 100% and can be interpreted as a fouling rate or cleaning frequency. The index was applied to evaluate biofilm growth in membrane fouling simulators with reverse osmosis membranes and commercial feed spacers operated with different feed water nutrient concentrations and crossflow velocities. Biofilm accumulation on the membrane and feed spacer was characterized in situ using optical coherence tomography. We showed that the biofouling index is directly related to the volume of biofouling independent of the applied crossflow velocity and a suitable tool for improved quantitative comparison of the biofouling rate. Furthermore our results suggest that the pressure drop is better described as function of the velocity at the perimeter of a spacer cell instead of the average velocity in the channel. Although the biofouling index is developed for biofouling, the index may be applied to quantitatively assess mitigation strategies in spacer filled channels for a wider range of fouling types.

Thermal dynamic and failure research on an air-fuel heat exchanger for aero-engine cooling

This paper presents a novel air-fuel heat exchanger used for the cooled cooling air technology in aero-engines. The helical tube heat exchanger weighing 1.1 kg with an area density of 214 m2/m3 can cool the hot air down 260 K at the air flow of 0.3 kg/s with relative airside pressure drop less than 0.6%. Empirical correlations by multiplying a constant of 1.06 and 0.837 can well predict the pressure drop and convective heat transfer coefficient respectively for hot gas cross-flowing helical tube bundles. Furthermore, in the tube failure tests to simulate the fuel control system fault and flight mode conversion, the straight tube can work continuously for more than 360 s under the extremely high tube wall temperature of over 1200 °C in the heat flux sudden increase test, while the bent tube could continue to glow brightly for 30 min. Coke morphology and chemical composition analysis revealed that increased thermal stress caused by gradually thicker coke layer takes a major cause in the heat flux sudden increase test. The secondary flow in bent tubes can effectively improve the convective heat transfer performance and reduce the formation of coke deposition, thereby improving the tube working life.

Experimental investigation into the effect of main stage swirl on flow and spray characteristics inside a stratified partially premixed combustor

Lean combustion has been applied in gas turbine combustors to meet increasingly stringent regulations for pollutant emissions. As a representative low-emission technology, stratified partially premixed (SPP) combustion is capable of effectively reducing NOx emissions while still providing robust flames. In this work, the flow and spray processes inside an SPP combustor were experimentally investigated to further reveal the role of main stage swirl in flow development and fuel placement. Particle image velocimetry (PIV) and Planar Mie scattering (PMie) techniques were applied to provide the velocity distributions and droplet distributions under isothermal conditions with a relative pressure drop ranging from 1% to 5%. A spray post-processing algorithm was developed to acquire the characteristic parameters of the sprays without clear boundaries. Results show that the strong swirl from the main stage leads to the radial flow of pilot air streams and dominates the formation of central toroidal recirculation zone (CTRZ). With the addition of the main stage swirl, a proper flow structure including jet zones, recirculation zones and shear layers is formed, which promotes the widening of droplet radial distribution and the increase of the spray cone angle. The spray distribution therefore transforms from a bubble shape into a cone shape. The findings and conclusions could promote the understanding of interactions between pilot and main stage swirls for stage combustors and contribute to the optimization of such SPP injectors.

Genesis of Antibiotic Resistance (AR) LXXVIII: Turbulence Modeling of Hemodynamics in Simplified Severe Sepsis Protocol‐2 (SSSP‐2)‐NCT01663701(ERP‐EGDT): Correlation of time (& fluid bolus) dependent pressure drop in boundary layer separation with adverse pressure gradient (APG) in tandem with exacerbated in‐hospital mortality(ihm)

The objective is to identify the underlying hemodynamic alteration in usual care group registered with 5 patients @ 100% ihm; vs the sepsis protocol cohort registered with 11 patients @ 90.05% ihmwith a median hospital stay of 5 days; GCS 3‐8(SAPS3≥56, (Ref: Fig 3) NCT01663701(PMID: 28973227). Cause for Concern: The pivotal clinical indices such as, i. antibiogram, ii.drug resistance index(DRI), iii.resistance map(RM), iv.antibiotic resistance footprint (ARF), v.AR stewardship data, and vi. Global Antimicrobial Resistance and Use Surveillance System (GLASS) data, for the entire patients’ cohorts before and after admitting to ED as a part of baseline characteristics, not presented. Rationale: Based on the aforesaid factor, it is inferred that patients in any given ERP‐EGDT, are: i. pre‐disposed to unknown level of infectious diseases burden with AR clinical persister(s)(ARClPrs); ii. activation of leucocytes, platelets, and erythrocytes forming LPE aggregates; iii. unknown extent of laceration in the precapillary arterioles, and post‐capillary venules, and iv. deposition of LPE aggregates on the pre‐capillary/post‐capillary vessels, w/o intravascular (loss of glycocalyx), in the cerebral/coronary/pulmonary/hepatic pre‐capillary arterioles, Fig 3.1 to 3.3; Fig 3.4, Derived rheological factors based on the data from Table 2: elements of sepsis resuscitation p1238; Fig 3: Risk of In‐hospital Mortality, p1239; predicted to be PI <1.05%, SpO2≦95%, PaO2 of 55 mmHg, SaO2<90%, SvO2<90%, StO2 below normal, DO2I below normal range, FiO2 <0.21(21%), PaCO2< 38 – 42 mmHg and PaO2/FiO2 <200mmHg. Derivation inclusive of CC, MCC (major complication or comorbidity), DDx:Pulmonary Edema, hypoxemia, tachypnea, and respiratory failure. GCS 3‐8: Coma Grade IV‐ unconscious, deep sleep, vestibular ocular reflex(VOR) negative, craniocaudally loss of brainstem reflexes, no reaction to pain, flabby tone, pupil dilated & fixed). Geometry: Blood flow network and mother‐daughters branching several generation of arterioles (or venules) with specific mean blood flow velocity (Vn), arbitrary generation (g) where rn = vessel radius of generation(n), r1 and v1 = radius, Fig 3.4 (p90 ISBN13‐978‐0128024089). Hypothesis & Governing Equation: eq: 3.2; eq 3.3; eq 3.4; Poiseuille eq (to determine and analyze the cause & effect relationship of flow pressure drop in a long cylindrical pipe/pre‐capillary vessels): DP=8mLQ /p R4 where DP = pressure difference between the two ends, m = dynamic viscosity, L=length of pipe, Q = volumetric flow rate, p = the dynamic viscosity, R = pipe radius (http://hyperphysics.phy‐astr.gsu.edu/hbase/ppois.html). Prospect: Simulation efforts are in progress to determine the sequence of fluid flow within the time scale of <0hrÛEDÜ120hrs>, pseudo‐plastic fluidÜdilatantÜBingham plasticÜ Hershel‐BuckleyÜ ThixotropicÜ Rheopectic)and its role in physiological (capillary) shunt augmented ihm.

A coupled LES-LBM-IMB-DEM modeling for evaluating pressure drop of a heterogeneous alternating-layer packed bed

• A LES-LBM-IMB-DEM (LLID) model was established. • The LLID model was carefully calibrated and validated. • Interface characteristics and resistance loss mechanisms of HAL beds were revealed. • A new correlation was proposed for evaluating the pressure drop of HAL beds. Packed beds composed of a heterogeneous alternating-layer (HAL) granular exist in many practical applications, such as blast furnaces of the ironmaking industry. Insights into HAL beds are significant to process performance but are still challenging and not fully understood. A coupled LES-LBM-IMB-DEM (LLID) model is established to directly obtain the interphase closure of fluid–solid systems and evaluate the pressure drop of HAL beds. The LLID model particularly involves pores turbulent flow of particle-resolved scale using the multiple-relaxation-time lattice Boltzmann model (MRT-LBM) with large eddy simulation (LES), tracking the interaction of particle–particle/walls using discrete element method (DEM), and coupling fluid-granular system using immersed moving boundary (IMB). The model was carefully calibrated concerning lattice resolution, sub-grid numbers, collocations of collision term and weight function, relaxation time, Smagorinsky constant. Also, it was verified via flowing past a particle, regular packed bed, and HAL bed, and found reasonable agreements achieved. Furthermore, the model was applied to investigate HAL beds, especially the interface characteristics, velocity and pores distribution, mechanism of interface resistance loss, and revealed the relationship of specific pressure drop between the interface region and bulk layer section. Finally, a new correlation of pressure drops for HAL beds was proposed via linking the interface pressure drop to the bulk layer.

Cryogel‐based co‐culture of Lactobacillus paracasei and Lactobacillus buchneri towards phenyllactic acid bioproduction: fundamental hydrodynamics and biotransformation characteristics

AbstractBACKGROUNDPhenyllactic acid is an important monomer for bioplastics, food preservative, feed additive and pharmaceutical agent. However, bioproduction of phenyllactic acid suffers drawbacks regarding the high cost of substrates, poor efficiency and yield of fermentation or conversion, and therefore new bioproduction strategies need to be investigated.RESULTSIn this work, bioproduction of phenyllactic acid was developed by employing semi‐hydrophobic cryogels as cell entrapment matrices to co‐culture Lactobacillus paracasei and L. buchneri strains, and the obtained cell‐loaded cryogels were used as biocatalysts in the biotransformation from phenylalanine. Flow characteristics and permeabilities of fermentation broths through cryogels, co‐culture performance and biotransformation characteristics were studied. Permeabilities of cell‐free fermentation broths through the cryogel bed were correlated as a function of concentrations of glucose and metabolites of organic acids. The flow rate versus pressure drop relationships for these bio‐based broths through cryogels were predicted successfully with a capillary‐based model. The cell growth was enhanced by cryogels and the maximum cell production of 40.6 g L−1 was achieved with cryogels. The maximum yield from phenylalanine of 1.0 mg mL−1 to phenyllactic acid was 39.6%, which was higher than that of 31.4% by co‐culture of L. casei and L. paracasei.CONCLUSIONFlow of fermentation broths through cryogels is crucial to develop a novel cryogel‐based bioproduction strategy for phenyllactic acid and can be characterized by capillary‐based modeling. Semi‐hydrophobic cryogels could be an interesting class of immobilization matrices for high‐cell‐density co‐culture towards the green strategy with these new biocatalysts in phenyllactic acid bioproduction and thus have potential applications in industries. © 2022 Society of Chemical Industry (SCI).

Experiment on the influence of flow number of the pilot-stage centrifugal atomizer on ignition performance of internally staged combustor

Ground ignition and high-altitude ignition are important performance indexes of a combustor. In this study, an internally-staged combustor and five pilot-stage centrifugal atomizers with engineering scale were developed. Flow characteristics of these atomizers were studied under the atomizer pressure drop of 0.3 MPa-3.50 MPa, and the flow number of atomizers was obtained. Under the combustor relative air pressure drop of 1.5%-5.5%, the ignition performance of the internally-staged combustor was studied at normal inlet temperature with both normal and negative inlet pressures. In the ignition experiment, only the pilot-stage atomizer worked in the fuel system. The results indicated that, at normal inlet temperature and normal inlet pressure, the lean ignition fuel/air ratio kept increasing as the combustor relative air pressure drop increased from 1.5% to 5.5%. With the same relative air pressure drop, the ignition envelope could be widened by reducing the pilot-stage flow number. On the other hand, under normal inlet temperature and negative inlet pressure, only the pilot-stage flow numbers of 5.0 and 7.3 at the relative air pressure drop of 1.5% showed successful ignition, while ignition was not successful in other conditions or with other pilot-stage flow numbers. Based on the Lefebvre ignition model, an empirical correlation with prediction errors less than 5% was proposed for lean ignition fuel/air ratio of various pilot-stage flow numbers in the internally-staged combustor at normal inlet temperature and normal inlet pressure.

Numerical study on flow and heat transfer characteristics of a novel Tesla valve with improved evaluation method

Tesla valve is check valve with no-moving-part, which cannot completely suppress reverse flow but has better reliability and flexibility than check valve with moving-part. Diodicity is most traditional and typical evaluation method used to evaluate the performance of Tesla valve. However, Diodicity decreases with increase of inlet/outlet section length, which fails to normatively evaluate performance of different Tesla valves. Therefore, standardized evaluation method for Tesla valve is conducive to its further application. In this paper, two improved parameters (Relative pressure drop ratio and Absolute pressure drop ratio) are proposed to make up for defect of Diodicity. Besides, a novel Tesla valve with special tapering/widening structure is designed, analyzed and compared with other type of Tesla valves, which shows superior absolute pressure drop ratio. Influences of multi related factors (inlet/outlet section length, inlet velocity, number of stage, property of fluid) on flow characteristics of fluid inside Tesla valve are investigated based on ANSYS Fluent 19.0 with realizable k-epsilon model and verified by experiments. Heat transfer performance of Tesla valve is also sufficiently studied and maximum temperature difference between forward and reverse flows can be 12.10 K, which has the potential to realize a new way for real-time thermal management.