Mass Injection Research Articles

Preparation of chiral stationary phase based on a [3+3] chiral polyimine macrocycle by thiol-ene click chemistry for enantioseparation in normal-phase and reversed-phase high performance liquid chromatography

Polyimine macrocycles are a new class of organic macrocycles with cyclic structures, well-defined molecular cavities, and multiple cooperative binding sites, which have recently aroused considerable research interest in molecular recognition and separation. Herein, we report the bonding of a [3+3] chiral polyimine macrocycle (H3L, C78H78N6O3) on thiol-functionalized silica gel using thiol-ene click chemistry to prepare a chiral stationary phase (CSP) for high performance liquid chromatography (HPLC). The fabricated column exhibited excellent chiral separation capability under both normal-phase and reversed-phase conditions. Fourteen and 10 racemates were well resolved on the column in normal-phase mode (using n-hexane/isopropanol as the mobile phase) and reversed-phase mode (using methanol/water as the mobile phase), respectively, including alcohols, esters, ethers, ketones, aldehydes, epoxides and organic acids. Moreover, the column also shows good selectivity toward positional isomers. Six positional isomers (dinitrobenzene, chloroaniline, bromoaniline, iodoaniline, nitrobrobenzene and nitrochlorobenzene) were well separated on the column. In addition, the effects of the injection mass and mobile phase composition on the separation were investigated. The column shows good reproducibility and stability after multiple injections with the relative standard deviation (RSD) (n = 5) of the retention time and resolution being < 0.96 % and 0.65 %, respectively. This study indicates that this type of chiral polyimine macrocycles is a promising chiral selector for HPLC enantioseparation and will push forward the applications of more novel chiral macrocycles for chiral chromatographic separation.

Effect of mass injection on secondary instability of hypersonic boundary layer over a blunt cone

In low environmental disturbances, secondary mechanisms play a crucial role in flow instability and transition. Over the years, researchers have shown the existence of secondary waves prior to nonlinear breakdown and turbulence. In high-speed flows, the vehicles are subjected to extreme thermal loads, and usually, an ablative heat shield is used for protection. The ablative materials eject gaseous products upon heating, significantly affecting flow stability. Mass injection through the surface in the boundary layer loosely replicates the ablation process. Its effect on stability and transition has been explored earlier using experiments, numerical simulation, and Linear Stability Theory (LST). However, the effect of the surface injection on secondary instability, the most viable path to transition, remains uncertain. The present work studies the secondary instability of a hypersonic boundary over a 7° half-angle blunt cone in the presence of mass injection through the surface of the boundary layer. Mean flow over the cone is solved using a high-order shock fitting direct numerical simulation code. Primary instability is studied using the LST, and secondary instability is studied using the secondary instability theory based on the Floquet model. Computations are carried out for different injection rates, and it is found that instability increases with mass injection rate. The mass injection has increased the primary and secondary growth rates. Fundamental modes are more dominant than subharmonic and detuned modes at higher primary wave amplitudes. The mass injection has increased the primary and secondary N-factor, and transitioning behavior is observed at the maximum injection rate.

Thermally Radiant Williamson Nanofluid Flow Over a Permeable Stretching Sheet with Viscous Dissipation and Joule Heating Effects

The present paper focuses on the study of an incompressible flow of a steady two-dimensional electrically conducting thermally radiant Williamson nanofluid over a permeable stretching sheet with viscous dissipation and joule heating effects. The governing partial differential equations are reduced to a couple of nonlinear ordinary differential equations by using suitable transformation equations; these equations are then solved numerically with the use of the conventional fourth-order Runge Kutta method accompanied by the shooting technique. Graphical results of the flow, temperature, and nanoparticles volume fraction profiles are displayed. Effects of the physical parameters on velocity, temperature, nanoparticles volume fraction, skin friction coefficient, and the rates of heat and mass transfer are investigated. The results indicate that the velocity ratio parameter enhances the skin friction coefficient, the velocity profile, and the rate of heat transfer whereas it minimizes the rate of mass transfer. On the other hand, increasing the values of the mass suction parameter results in both the velocity and the temperature boundary layer thickness decrease whereas increasing the mass injection enhances both the velocity and the temperature profiles; but it vigorously enhances the rate of heat transfer. The non-Newtonian parameter fosters the rate of heat transfer whereas it lessens both the velocity and rate of mass transfer of the nanofluid.

Effect of different cooling mediums on mass injection pre-compression cooling

• Related experiments are conducted to explore the cooling effect of mixed organic working mediums, including concentration, liquid–gas ratio, incoming airflow temperature, etc. This part of the research is relatively rare in previous studies. • In the test, a gas analyzer is applied to record and analyze the evaporation rate of ethanol in the test to explore the evaporation characteristic of the organic coolant. • The simulation results are calibrated through the test data to verify the accuracy of the simulation and confirm the accuracy and reliability of the test method. In the process of injection cooling, the selection of working mediums brings different effects. However, most researches still focus on water. Compared with water, the vapor formed by the evaporation of organic cooling mediums such as ethanol can assist combustion in the combustion chamber. The current research on the cooling effect of organic mediums is relatively lacking. Therefore, related tests on the cooling effect of organic working fluids are conducted. The test results show that: as the spray temperature decreases from 45 ℃ to 18 ℃, the cooling effect improves (maximum temperature drop reaches 63 ℃). Ethanol solutions of various concentrations can maintain an evaporation rate of more than 75%, and its evaporation and cooling effect are improved with the concentration increase. Not all organic cooling mediums can bring good temperature drop and evaporation effects, including glycol solution. In working conditions, a higher airflow temperature (up to 150 °C) can enhance the cooling effect of the working mediums, and the liquid–gas ratio (6.62–10.76%) has almost no influence on the temperature drop. Finally, the simulation results are calibrated through the test data to verify the accuracy of the simulation and confirm the accuracy and reliability of the test method.

Performance optimization of pinnate horizontal well in geothermal energy utilization with orthogonal test

• Enhanced geothermal system (EGS) with pinnate horizontal wells is proposed. • Geostress balance is taken into account in numerical model. • Multifactor and multilevel optimization is presented. • Effects of human-made parameters on the heat extraction performance are discussed. Aiming at efficiently utilizing the hot dry rock resources, a potential enhanced geothermal system (EGS) with pinnate horizontal well (PHW) is investigated in present work. The multifactor and multilevel orthogonal tests are performed to probe the combined effect of human-made parameters on the reservoir properties, and to find the optimum operation strategy of PHW EGS. To evaluate the heat extraction performance of PHW EGS, geostress balance method is taken into account in the thermo-hydro-mechanical (THM) coupling model. The main factors of different human-made parameters that affect the heat extraction performance have been ranked based on their effect level, which are injection temperature, injection mass rate, production pressure, well spacing and length. In addition, Enthalpy-exergy is employed to evaluate the maximum available work of the extracted thermal energy. The present results demonstrate that the heat extraction performance of doublet EGS can be significantly improved by 12.57 MW ∼ 13.60 MW when the branch wells are introduced. The fractured region is mainly affected by the tensile stress, and the compressive stress predominates in reservoir margin. The production temperature is significantly affected by the well spacing, while the water loss rate has a strong correlation with production pressure. Under the recommended operation scheme, the maximum available work of PHW EGS ranges from 20.18 MW to 17.31 MW can be obtained, which accounts for from 23.76 % to 26.12 % of the extraction of thermal energy.

Analysis of heat transfer based on complex Embedded Discrete Fracture Network (EDFN) for field-scale EGS

This study proposed a doublet horizontal well injection enhanced geothermal systems(EGS) model for heat extraction via the embedded discrete fracture network. Thermal-hydraulic(TH) coupling was established and applied in this model. The performance of thermal exploitation by the comparison of four specific models (reservoir without fractures, reservoir with hydraulic fractures, reservoir with discrete fractures, and reservoir with hydraulic and discrete fractures) to optimize the base model were investigated. Meanwhile, the sensitivity analysis of reservoir parameters and injection parameters were conducted. Four specific indexes including fractures permeability, injection temperature, injection mass flow rate and well layout schemes were selected for evaluating the performance of heat extraction. The results shown that increasing the fracture number and improving the connectivity can obtain an excellent heat extraction effect. Firstly, there is a threshold for fracture permeability. Only the adequate stimulation measures were applied to increase the fracture permeability, did the stimulation of thermal power output can be reached. Secondly, increasing injection temperature will induce the enhancement of viscosity and pressure loss, and thus decrease the velocity of fluid and the temperature difference. Which is reflected in the descending of thermal power output finally. Furthermore, increasing the injection mass flow rate will give rise to the thermal power output greatly. However, it will also require greater injection pressure and energy input. Therefore, it is necessary to strike a balance between the injected mass flow and the thermal output power. Finally, the results of simulation in various well layouts illuminate that the area of the fluid flowing through the reservoir determines the temperature of the production fluid. Overall, this study provides reasonable suggestions and guidance for field-well layouts design and analysis, and heat extraction sensitivity parameters optimization under the condition of complex embedded discrete fracture networks.

Thermodynamic modeling and analysis of ammonia injection pre-compressor cooling cycle: A novel scheme for high Mach number turbine engines

Mass injection pre-compressor cooling (MIPCC) is one of the significant technologies to extend the operating envelope of turbine engines. In this paper, a new high Mach number turbine scheme is proposed with liquid ammonia injection instead of water injection. The basic properties of ammonia, especially the boiling point, latent heat of vaporization and auto-ignition temperature, are introduced. To evaluate the engine performance, a thermodynamic model incorporating the ammonia mass injection pre-compressor cooling (Ammonia MIPCC) process is developed. The accuracy of the model is demonstrated by verifying the design point, operating line, and Ammonia MIPCC processes. Simulations show that the Ammonia MIPCC process is mainly suitable for extended operating Mach number envelopes. Ammonia injection should be avoided for normal operating conditions because it causes a decrease in specific impulse. Through liquid ammonia injection, the operating Mach number of the turbine engine is increased from 3.1 to about 3.5. Moreover, the maximum operating Mach number (MOM) limit of the Ammonia MIPCC engine is investigated. Pre-Compressor cooling requirements and combustor heat release limits jointly constrain the amount of ammonia injection, which prevents further expansion of the MOM. Furthermore, the Ammonia MIPCC engine has the advantage of greater specific thrust at the same Mach number compared to water injection, and with Mach numbers greater than 3.36, the Ammonia MIPCC engine has a specific impulse advantage. In general, the Ammonia MIPCC engine is an effective solution for a high Mach number turbine.

Numerical study on jet noise suppression with water injection during one-nozzle launch vehicle lift-off

The launch vehicle will experience extreme acoustic environment at lift-off, which will cause the invalidation and destruction of the aerospace equipment, and reducing noise is of great significance for improving launch safety. In this paper, the numerical simulation of gas–liquid two-phase flow and its acoustic field is carried out, and the flow field is simulated by the discrete phase model (DPM), second-order Roe format, Scale-Adaptive Simulation (SAS) and three-dimensional Navier–Stokes. Based on the analysis of the flow field, the acoustic analogy integration method (FW-H) is used to predict the jet noise at the observation position. The influence of the water different injection angles and mass flow rate ratios are studied, and the results show that water injection not only reduces the temperature, velocity and vorticity at the gas–liquid interface, and the temperature at the bottom of the jet deflector, it also significantly reduces the jet noise. The total sound pressure level can be reduced to 6.92 dB by appropriate selection of the water injection angles and water injection mass flow rates. The numerical method established in this paper provides a useful tool for the design and analysis of water injection noise reduction for high-thrust multi-nozzle launch vehicle.

Temperature and pressure variations in salt compressed air energy storage (CAES) caverns considering the air flow in the underground wellbore

The flow of compressed air in the wellbore affects the thermodynamic performance in the salt compressed air energy storage (CAES) cavern and this effect is still uncharted. In this study, a coupled explicit finite difference model considering the wellbore flow is proposed to obtain thermodynamic performance of the compressed air in the cavern. It is found that the thermodynamic performance is directly determined by the air temperature and pressure at the wellbore outlet, which are changed by the flow in the wellbore. A sensitivity study shows that the injection mass rate is the key parameter and significantly increases the air temperature and pressure in the cavern. The injection temperature and wellbore length are secondary factors. A high injection pressure is beneficial for energy storage. The inner diameter, roughness and thermal conductivity of the wellbore influence the performance slightly. The developed combined model is a more accurate tool for predicting the thermodynamic performance of a deep CAES cavern.

Comparing and Optimizing RNA Extraction from the Pancreas of Diabetic and Healthy Rats for Gene Expression Analyses.

Advanced differential gene expression analysis requires high-quality RNA. However, isolating intact pancreatic RNA is challenging due to abundant pancreatic ribonucleases, which limits efficient downstream gene expression analysis. RNAlater treatment reduces endogenous ribonucleases effects through either pre-organ excision via organ mass or bile duct direct injection or organ mass injection post-isolation. We compared RNA extraction protocols to establish a reproducible and effective pancreatic RNA extraction method to obtain high RNA integrity number (RIN) values from healthy and streptozotocin (STZ)-induced diabetic rats for gene expression analyses. Different methods were tested focusing on RNase activity inhibition using RNAlater (Qiagen) pre-harvest of the pancreatic tissue, and extracted RNA quality and concentration were analyzed using NanoDrop spectrophotometer, Agilent Bioanalyzer, and RT-PCR. Inclusion of several pre- and post-excision modifications in the RNeasy Mini Kit (Qiagen) protocol resulted in RIN values more than two-fold higher compared to those using the standard protocol. Additionally, RT-PCR amplification of the housekeeping gene, β-actin, revealed no differences in extracted RNA quality from healthy and STZ-induced diabetic rats. We compared and developed a more effective and reproducible pancreatic RNA extraction method from healthy and diabetic rats, which resulted in RNA of superior quality and integrity and is suitable for complex molecular investigations.

Oxidation Response of Transpiration-Cooled on a Hypersonic Stagnation Point

This work presents the oxidation response of a transpiration-cooled hypersonic stagnation point made of porous . Low-order models are used to calculate the surface temperature and oxygen concentration for a given flight condition. An analytical material oxidation model computes the surface recession and oxide layer thickness. A 500 s steady-state trajectory at 44 km altitude and velocity is found to lead to 2.2 mm recession of the 3 mm nose radius. A constant mass injection at a blowing parameter of 0.6 reduces the recession to just 0.21 mm. The displacement of freestream oxygen by transpiration cooling has a significant effect on oxidation. Not accounting for the displacement of oxygen at the surface would increase the recession by up to 197%. The recession along the transient trajectory of an envisioned hypersonic vehicle with a 3 mm nose radius is found to exceed 0.94 mm with no mass injection. It is shown that nitrogen and helium injection at a blowing parameter of 0.6 can reduce the recession to 0.13 and 0.075 mm, respectively.

Turbulent mass transfer near gas-liquid interfaces in water and shear-thinning dilute polymer solution

Turbulence is known to enhance gas-liquid mass transfer and mixing of high Schmidt number dissolved gases in water by deforming the concentration boundary layer that develops at the interface. Fundamental mechanisms of surface renewal and injection have been progressively evidenced throughout the last decades, via fundamental experiments of low mean shear turbulence interacting with flat interfaces in water. However, and despite the obvious influence of non-Newtonian behaviours on gas liquid mass transfer in industrial and environmental applications, not such study exists (to the best of the author’s knowledge) on whether and how these mechanisms apply in shear-thinning dilute polymer solutions (DPS). Following a previous work on near surface hydrodynamics, turbulent mass transfer and mixing is studied in a weakly shear-thinning fluid, and compared to the Newtonian, water case. Stereoscopic Particle Image Velocimetry (SPIV) and Inhibited Planar Laser Induced fluorescence are used simultaneously to measure the local liquid phase velocity and dissolved gas concentration fields respectively. Coupled measurements are used to estimate the turbulent mass fluxes, which are interpreted using a conditional quadrant analysis. Results show that in DPS as well as in water, surface renewal is the most frequent mechanism, but injection events are the most efficient in terms of mass transfer. Even at a low concentration, the polymer significantly modifies the signature of those mass transfer events, by enhancing scalar stretching and injection mass transfer outside of the viscous sub-layer, altering classical gradient models.

Stochastic Model of Liquid Fuel Spraying at High Pressures and High Reynolds Numbers

The paper describes the main features of the combustion of liquid fuel injections, developed a stochastic model for the atomization of liquid fuels injected into the combustion chamber at high pressures and high Reynolds numbers. A mathematical model for the combustion of liquid injections at high pressures and high Reynolds numbers is presented, which includes: the equations of continuity, motion, internal energy, the K-ε model of turbulence, a system of equations describing the processes of evaporation, mixing, rupture and coalescence of liquid fuel droplets. A stochastic model of atomization of liquid fuels injected into a combustion chamber at high pressures and high Reynolds numbers has been developed. On the basis of the proposed model, computational experiments were carried out to study the combustion of liquid fuel depending on the injected mass in the combustion chamber under given initial conditions in full. When studying the effect of the mass of liquid fuel on the processes of ignition and combustion at high pressures and high Reynolds numbers, the mass values for octane 6 mg and for dodecane 7 mg were taken as the most optimal. A further increase in the injection mass, both for octane and dodecane at optimal pressures, worsens the combustion process. The results obtained are of fundamental and practical importance and can be used to develop the theory of combustion of gaseous and liquid fuels.

Application of machine learning to optimize the combustion characteristics of RCCI engine over wide load range

The objective of this study is to investigate, optimize, and compare the combustion features and intake variables affecting the kinetics of gasoline/diesel RCCI engine by applying the genetic algorithm. Six decision variables include the fuel flow rate (FFR), premixed fuel rate (PFR), exhaust gas recirculation (EGR) rate, first injection mass ratio (IMR1), and the first and the second start of injection (SOI1 and SOI2). The objective of the optimization was to simultaneously maximize the engine gross indicated efficiency (GIE), the second law efficiency (SLE), and minimize exhaust emissions and the maximum pressure rise rate. The optimal space filling design of experiment method was applied to evaluate the effect of the decision variables on the objective functions with a minimum number of numerical experiments. The relationships between the decision variables and objective functions were approximated by the genetic aggregation response surface model. Finally, the non-dominated sorting genetic algorithm II was employed to find the optimum values. In the optimal case GIE, SLE, and Fmerit increased by 1.56%, 1.25%, and 15.14% while NOx concentration and engine noise reduced by 16.67% and 33.45%, respectively. The best range of SOI2 for GIE is between –22 and −14 degrees ATDC, while for improving SLE, SOI2 should be advance. Sensitivity analysis shows that PFR and FFR are the most influential variables to moderate the combustion kinetics and increasing IMR1 has the proper effect on combustion by creating more opportunities for a homogeneous charge and reducing hot spots.

Mechanism and prediction of flow oscillation based on counter-flow jet for drag reduction in hypersonic flow

The counter-flow jet, which is utilized for drag reduction in high-speed aircraft, creates an extremely unstable flow mode known as the long penetration mode (LPM) when the injection mass flow rate is low. Although the LPM provides a high drag reduction efficiency, it can cause an unstable condition that disrupts aircraft control owing to the oscillation characteristics. In this study, the oscillation mechanism of the LPM was investigated through experiments and computational simulations. It was confirmed that fluid impulse is the main factor affecting the LPM flow behavior, and that the recirculation region pressure determines the fluid impulse variation. To validate the effect of the fluid impulse, the frequency of the LPM oscillation was predicted based on the analyzed mechanism using a mass-spring model. The results showed that the applied modeling predicts the oscillation frequency satisfactorily. Therefore, the results confirmed that fluid impulse is a dominant factor that affects the LPM flow oscillation. In addition, the condition under which the flow structure undergoes a transition was investigated via fluid impulse. Based on some physical assumptions, the transition condition was analyzed. It was confirmed that the fluid impulse and static pressure in the recirculation region impose a dominant effect on the flow oscillation and the transition from LPM to SPM.

Evolution of Jupiter‐Style Critical Latitudes: Initial Laboratory Altimetry Results

AbstractThis is a laboratory zonal‐jet study using a rotating water tank. The bottom topography has a tent‐shaped radial cross section designed to generate two critical latitudes, that is, two positions whereβe, the radial gradient of the potential vorticity (PV), changes sign. This configuration is motivated by observations indicating that Jupiter and Saturn have not only multiple zonal jets, but multiple stable critical latitudes. It is known that “supersonic” critical latitudes (with respect to Rossby waves) are stable, whereas “subsonic” critical latitudes are posited to be unstable. Because Rossby waves are unidirectional, “supersonic” critical latitudes come in two varieties: Rossby Mach numberMR &gt; 1 and &lt; 0, where the latter holds when the waves are directed downstream. Experiments focus on: (a) how do zonal jets emerge from localized forcing in a system with alternating PV gradients? and (b) what differences are there between the evolution of various types of critical latitudes? The water is forced by mass injection along one radius. Laboratory altimetry provides accurate, unobtrusive records of the circulations that reveal the emergence of counter‐propagatingβ‐plumes (Rossby‐wave envelopes), which expand into tank‐encircling zonal jets. The tank's negativeβezone (annulus) is characterized byMR∼ 1. The weaker critical latitude adjusts its position by about 4% of the tank radius and maintainsMR∼ 1, similar to the state surmised for Jupiter and Saturn, whereas the stronger critical latitude vacillates while maintaining |MR| ≪ 1 and may be relevant to steep oceanic seamounts.

Performance of enhanced geothermal system with varying injection-production parameters and reservoir properties

The injection-production parameters and reservoir properties significantly affect the heat extraction performance of the enhanced geothermal system (EGS), while quantitative rankings of the effecting parameters have been yet unknown. This paper is devoted to investigating numerically the heat extraction performance of EGS by three-dimensional reservoir models under the influence of varying injection-production parameters and reservoir properties. A thermal-hydro-mechanical (THM) coupled model is used to quantify the complicated heat extraction process of EGS. Three-dimensional geothermal reservoir models containing random fracture networks are established based on the Monto Carlo algorithm to quantify the effect of fracture numbers in the process of heat extraction. The parameter sensitivity of the injection-production parameters (injection mass flow rate and injection temperature) and the reservoir properties (rock matrix porosity, fracture permeability, and rock matrix permeability) on the heat extraction performance are ranked and evaluated over the Qiabuqia enhanced geothermal system. It is found the heat extraction performance shows non-monotonic relationships with the fracture numbers in the three-dimensional reservoir model, which indicates the necessity of EGS fracture optimization. The injection mass flow rate turns out the first while the fracture permeability and injection temperature are the secondary dominating factors affecting the heat extraction performance among the evaluated parameters. The outcomes are beneficial to the high-efficiency construction, operation, and optimization of the EGS especially those with similar conditions to the Qiabuqia EGS.

Experimental Research on Seepage Law and Migration Characteristics of Core-Shell Polymeric Nanoparticles Dispersion System in Porous Media.

The nanoparticles dispersion system has complex migration characteristics and percolation law in porous media due to the interaction between the nanoparticles and porous media. In this paper, lab experiments were carried out to characterize the morphology, particle size distributions, and apparent viscosities of SiO2/P(MBAAm-co-AM) polymeric nanoparticle solution, investigate its migration characteristics in porous media, and probe its capability of enhanced oil recovery (EOR) in the reservoirs. Quartz microtubule, sand pack, and etched glass micromodels were used as the porous media in the flow and flooding experiments. Gray image-processing technology was applied to achieve oil saturation at different flooding stages in the micromodel for calculating the EOR of the SiO2/P(MBAAm-co-AM) polymeric nanoparticle solution. The results show that The SiO2/P(MBAAm-co-AM) polymeric nanoparticles are spherical with diameters ranging from 260 to 300 nm, and the thicknesses of the polymeric layers are in the range of 30–50 nm. As the swelling time increases from 24 to 120 h, the medium sizes of the SiO2/P(MBAAm-co-AM) polymeric nanoparticles increase from 584.45 to 1142.61 nm. The flow of the SiO2/P(MBAAm-co-AM) polymeric nanoparticles has obvious nonlinear characteristics and a prominent scale effect at a low-pressure gradient, and there should be an optimal matching relationship between its injection mass concentration and the channel size. The flow tests in the sand packs demonstrate that the SiO2/P(MBAAm-co-AM) polymeric nanoparticles can form effective plugging in the main flow channels at different permeability areas and can break through at the throat to fulfill the step-by-step profile control. Moreover, the profile control of the SiO2/P(MBAAm-co-AM) polymeric nanoparticles strengthens with an increase in their swelling time. The microscopic flooding experiment in the etched glass micromodel confirms that the SiO2/P(MBAAm-co-AM) polymeric nanoparticles can block dynamically and alternatively the channels of different sizes with the form of loose or dense networks to adjust the fluid flow diversion, improve the sweep efficiency, and recover more residual oil. The SiO2/P(MBAAm-co-AM) polymeric nanoparticles can achieve an enhanced oil recovery of 20.71% in the micromodel.

Parametric study of the impact of EGR and fuel properties on diesel engine performance using a predictive thermodynamic model

This paper presents a detailed quasi-dimensional model that can assist in the design process as it allows predicting the performance and emissions of compression ignition (CI) engines functioning with different fuels, such as kerosene and Diesel. The proposed model includes a new dedicated fuel injection mass flow rate sub-model that is coupled to the multi-zone spray packet concept for spray development. Moreover, fuel spray development and its interaction with in-cylinder swirl is considered and allows studying the influence of combustion chamber design, fuel injection strategy, as well as fuel properties. The model is validated against single and double injection strategies using kerosene and diesel fuels and is shown to be capable of predicting engine performance with a good accuracy. The results obtained from the parametric studies have shown proper trend with respect to the effect of the bowl-to-bore diameter ratio, EGR rate and temperature or fuel properties. This latter predicts that fuels with higher lower heating values (LHVs) can decrease NO and soot emissions by using retarded injection timing, while the boiling temperature has a small effect on the evaporation and mixture formation process. Finally, a fuel with a high enthalpy of vaporization can achieve lower soot emissions by increasing the swirl ratio or increasing the injection timing although doing so is detrimental to the power output.

The Role of Disk Tearing and Precession in the Observed Variability of Pleione

Abstract We acquired Hα spectroscopic observations from 2005 to 2019 showing Pleione has transitioned from a Be phase to a Be-shell phase during this period. Using the radiative transfer code hdust, we created a grid of ∼100,000 disk models for Pleione. We successfully reproduced the observed transition with a disk model that varies in inclination while maintaining an equatorial density of ρ 0 ( r ) = 3 × 10 − 11 ( r / R eq ) − 2.7 g cm − 3 , and an Hα-emitting region extending to 15 R eq. We use a precessing disk model to extrapolate the changing disk inclination over 120 yr and follow the variability in archival observations. The best-fit disk model precesses over a line-of-sight inclination between ∼25° and ∼144° with a precessional period of ∼80.5 yr. Our precessing models match some of the observed variability but fail to reproduce all of the historical data available. Therefore, we propose an ad hoc model based on our precessing disk model inspired by recent smoothed particle hydrodynamics simulations of similar systems, where the disk tears due to the tidal influence of a companion star. In this model, a single disk is slowly tilted to an angle of 30° from the stellar equator over 34 yr. Then, the disk is torn by the companion’s tidal torque, with the outer region separating from the innermost disk. The small inner disk returns to the stellar equator as mass injection remains constant. The outer disk precesses for ∼15 yr before gradually dissipating. The process repeats every 34 yr and reproduces all trends in Pleione’s variability.