Injection Conditions Research Articles

CFD unified approach under Eulerian-Lagrangian framework for methanol and gasoline direct injection sprays in evaporative and flash boiling conditions

Innovative synthetic fuels for advanced propulsion systems, such as methanol and ammonia, and synthetic blended fuels (E00, E10, and E30), known for their high volatility, are often injected directly into combustion chambers. It follows that Eulerian-Lagrangian spray models need to accurately capture the spray collapse as a consequence of flash boiling onset and be capable of proficiently handling the preferential evaporation of multi-component fuels in evaporative scenarios.So, we performed the assessment of an Eulerian-Lagrangian CFD code for simulating methanol and E00 gasoline blend sprays in both early and late injection conditions involving flash boiling conditions and preferential evaporation. The adoption of an effervescent breakup model and of a non-equilibrium phase transition model for the discrete phase allows the adoption of a setup that is almost completely free from specific constant tuning, especially for what concerns the breakup model. We validated the simulations using experimental PLV maps of methanol and E00 sprays issued from the ECN Spray M injector. The results highlight a significantly different morphology of the methanol spray compared to the E00 one under late injection conditions. Under stratified combustion, low-volatile fuels are likely to be ignited first, and the flame propagates toward the high-volatile fuels. The spray collapse was also correctly reproduced, inducing the presence of a low-pressure zone and modifying the spray morphology.

Adaptability analysis of H2-rich gas injection and sintered ore performance with different raw material ratios

As a source substitution technology that reduces pollutants emission and optimizes sinter properties, H2-rich gas injection-assisted iron ore sintering holds significant practical value. This study analyzed the adaptability of this technology to different ore blend ratios and basicity levels by comparing sintering indexes, pore structure, mineral phase composition, and metallurgical performance before and after H2-rich gas injection. The carbon emission reduction following H2-rich gas injection was calculated. The results indicate that increasing the proportion of high-silica, low-alumina ore (Ore-A) and basicity, along with H2-rich gas injection, can effectively enhance sinter yield and quality, but shrink the pore structure of sinter. Under H2-rich gas injection conditions, decreasing Ore-A ratios and increasing basicity can augment SFCA phase formation and mineral phase uniformity, thereby improving the anti-pulverization ability and reductivity of the sinter. H2-rich gas injection presents better adaptability to sintered ore with lower Ore-A ratio and basicity, which can achieve greater improvements in the sintering indexes, RDI, and RI. For a 265 m2 sinter plant producing sinter with 18 wt.% Ore-A and 2.0 basicity, annual CO2 emissions can be reduced by approximately 40,000 t.

Simulation study on the cavitation flow characteristics of liquid ammonia in the nozzle under high-pressure injection conditions

In this study, a non-isothermal compressible cavitating flow simulation model for liquid ammonia in high-pressure injector, accounting for the phase change properties, was established. The model was validated using experimental data from existing literature. The cavitation phase change process of liquid ammonia within the injector nozzle was investigated, and the differences in cavitation distribution between ammonia and diesel were explored. The results indicate that with increasing injection pressure, the vapor volume fraction of ammonia increases linearly, while that of diesel fuel shows a rapid initial rise followed by a decelerating trend. In terms of flow coefficient, ammonia is lower than diesel, though the two values converge at higher injection pressures. Under low injection pressure, the heat absorbed by the cavitation phase change of ammonia exceeded the heat generated by the high-speed friction of ammonia flow against the nozzle wall, leading to a temperature drop at the nozzle inlet. Conversely, at high injection pressure, the temperature of ammonia on the nozzle wall increases by more than 20 K, resulting in a rapid rise in saturated vapor pressure and significantly intensifying the cavitation effect. Compared to ammonia, diesel experienced a higher temperature rise within the nozzle but exhibited smaller variations in saturated vapor pressure, making the temperature effect on cavitation less pronounced. Diesel’s higher density and viscosity resulted in lower flow velocities compared to ammonia, leading to more developed cavitation in the lower wall region of the nozzle and creating a higher pressure region on the upper wall of the nozzle, which was more distant from the nozzle inlet and inhibited cavitation development there. The research results provide theoretical support for the design of liquid ammonia injectors.

Pilot study on coke oven flue gas injection desulfurization using highly active modified calcium hydroxide desulfurizer

AbstractCalcium hydroxide injection desulfurization has attracted extensive attention because of its low cost and recyclable characteristics. The modified calcium hydroxide was prepared on the basis of the digestion of calcium lignosulfonate (wood calcium) aqueous solution with ethanol and used in the pilot test of flue gas injection desulfurization of the coke oven. The injection desulfurization experiment was carried out with calcium hydroxide modified by 50% ethanol and 20% ethanol+0.5% wood calcium. It was found that the injection desulfurization efficiency of the two modified calcium hydroxide was better than that of the unmodified calcium hydroxide under the same injection conditions. The desulfurization efficiency of 20% ethanol+0.5% calcium hydroxide modified by wood calcium can reach more than 93.7% under the condition of 2 and 5 times calcium to sulfur ratio. The XRF analysis of desulfurization product showed that the content of S element in unreturned desulfurization ash was only 1.28%, which increased to 4.46% after 5 times of return. BET results showed that the specific surface area of the returned desulfurization ash decreased from 35.115m2/g to 10.256m2/g and the pore volume decreased from 0.103cm3/g to 0.0433cm3/g.

Importance of Clay Swelling on the Efficacy of Cyclic Steam Stimulation in the East Moldabek Formation in Kazakhstan

Both steam and hot water flooding of high-viscosity oils in the presence of swelling clays are difficult methods for producing oil efficiently because of potential formation permeability reduction. This paper pertains to heavy oil recovery from the East Moldabek formation where the oil API gravity is about 22 and is inundated with swelling clays. To achieve this, we used the IntersectTM reservoir simulator to compare oil recovery economics using both hot water and steam injection as a function of steam cycle duration, temperature, and steam dryness. We also studied clay swelling in the East Moldabek formation where clay poses a significant challenge due to its impact on permeability reduction. In this research, we developed an equation based on experimental data to establish a relationship between water mineralization and permeability in the East Moldabek formation. The equation provides valuable insight on how to mitigate clay swelling which is crucial for enhancing oil recovery efficiency—especially in sandstone reservoirs. Our modeling studies provide the recovery efficiencies for salinities of the hot water EOR versus cyclic steam EOR methods in a formation containing swelling clays. Specifically, the reduction in formation permeability as a function of the distilled water fraction is the controlling parameter in hot water or steam flooding—when the formation water mixture becomes less saline, oil recovery decreases. Our research shows that clay swelling can significantly impact cyclic steam stimulation outcomes, potentially reducing its effectiveness, while hot water flooding may offer a more cost-effective and operationally feasible solution in formations where clay swelling is a concern. Economic analysis reveals the potential for achieving an optimal favorable condition for hot water injection. Therefore, this paper provides a guideline on how to conduct thermal oil recovery for heavy oils in fields with high clay content such as the East Moldabek deposit.

Identification and characteristics of Plesiomonas shigelloides isolated from Mastacembelus armatus

Plesiomonas shigelloides (P. shigelloides), a dominant pathogenic strain identified as YY001, was successfully isolated and characterized from the hepatopancreas of diseased Mastacembelus armatus (M. armatus) for the first time. The strain was identified through a comprehensive approach that included morphological, physiological, and biochemical characterization, as well as 16S rRNA, 23S rRNA, and gyrB gene sequence analysis. Strain YY001 is classified as a Gram-negative bacterium, with optimal growth conditions observed at 28°C and pH 7.0. Results from the bacterium hemolysis test indicated the absence of hemolytic activity in YY001. However, the strain exhibited amplification of nine virulence genes: nanE, waaA, clpP, ssb, actP, aphA, astA, astD, and astB. Drug-resistance testing showed that YY001 displayed resistance only to penicillin G, oxacillin, norfloxacin, and tetracycline, while remaining sensitive to the majority of other antibiotics. Furthermore, nine drug-resistance genes, including emrD, catB, macB, ksgA, tolC, bacA, MdfA, sul1, and DegP, were detected through amplification. Experimental infection demonstrated that YY001 induced symptoms such as abdominal swelling, visceral edema, and hemorrhage, with hepatopancreatic manifestations being particularly severe. The median lethal dosage of strain YY001 in M. armatus was 9.7×108 colony-forming units (CFU)/mL within 48 h, and 4.9×106 CFU/mL within 192 h under the conditions of intraperitoneal injection. The hepatopancreas, gill, and intestine of infected fish showed obvious pathological symptoms, including tissue loosening, hemorrhage, and cell necrosis. The results of this study provided evidence for a more comprehensive understanding of P. shigelloides strain YY001 infection in M. armatus.

Microscopic Experiments to Assess the Macroscopic Sweep Characteristics of Carbon Dioxide Flooding

The Lunnan oilfield in the Tarim Basin, one of China’s major onshore oilfields with substantial geological reserves, faces particular challenges due to the complexity of its reservoir environment and the dispersion of remaining oil. Carbon dioxide, a greenhouse gas, presents an opportunity for enhanced oil recovery (EOR) and geological storage. In this context, the use of carbon dioxide for EOR can simultaneously address environmental concerns and improve oil recovery rates. This study focuses on the TI reservoir in the No. 2 well area of the Lunnan oilfield, employing advanced techniques to analyze the micro- and macro-characteristics of carbon dioxide flooding. Results: From the microscopic point of view, carbon dioxide flooding is mainly miscible with crude oil, which has a strong component exchange effect and can be displaced in the form of full pores, and the microscopic displacement efficiency is close to 100%. Macroscopically, under the combined injection and production of different injected hydrocarbon pore volume multiples (HCPVs), it is injected at the upper and lower layers of the interlayer and produced far away from the lower layer of the interlayer, with a total recovery rate of 52.83%. With the increase in the HCPV, the recovery increased rapidly at first and then slowly, and the HCPV at the demarcation point was 0.5, while the oil production rate increased in a wave-like manner and then decreased rapidly, and the HCPV at the breakthrough point of TI gas was 0.5. However, when the upper and lower layers far away from the interlayer are injected at the same time, the upper and lower layers of the interlayer are produced at the same time, and the total recovery rate can reach 83.02%. With the increase in the HCPV, the recovery rate increases rapidly at first and then slowly, and the HCPV at the turning point is 6.52. The oil production rate increases in a wave-like manner, then decreases rapidly, rises rapidly, and then decreases slowly in a wave-like manner. The HCPV at the breakthrough point of TI gas is 0.63, and the HCPV at the injection–production transition point is 0.63. The total recovery rate of carbon dioxide miscible displacement can reach 88.68% under the condition of separate injection and combined production with different injected hydrocarbon pore volume multiples. With the increase in the HCPV, the recovery increased rapidly at first and then slowly. The HCPV at the demarcation point was 6.5, the oil production rate increased in a wave-like manner, then decreased rapidly, increased rapidly, and then decreased slowly in a wave-like manner. The HCPV at the breakthrough point of TI gas was 0.63, and the HCPV at the injection–production transition point was 6.5. The research results provide data support for the physical reality of the microscopic and macroscopic sweep characteristics of carbon dioxide flooding in the Lunnan oilfield, Tarim Basin.

Comparative Study of Temperature and Pressure Variation Patterns in Hydrogen and Natural Gas Storage in Salt Cavern

Clarifying the distribution of temperature and pressure in the wellbore and cavern during hydrogen injection and extraction is crucial for quantitatively assessing cavern stability and wellbore integrity. This paper establishes an integrated flow and heat transfer model for the cavern and wellbore during hydrogen injection and withdrawal, analyzing the variations in temperature and pressure in both the wellbore and the cavern. The temperature and pressure parameters of hydrogen and natural gas within the chamber and wellbore were compared. The specific conclusions are as follows. (1) Under identical injection and withdrawal conditions, the temperature of hydrogen in the chamber was 10 °C higher than that of natural gas, and 16 °C higher in the wellbore. The pressure of hydrogen in the chamber was 2.9 MPa greater than that of natural gas, and 2.6 MPa higher in the wellbore. (2) A comparative analysis was conducted on the impact of surrounding rock’s horizontal and numerical distance on temperature during hydrogen and natural gas injection processes. As the distance from the cavity increases, from 5 to 15 m, the temperature fluctuation in the surrounding rock diminishes progressively, with the temperature effect in the hydrogen storage chamber extending to at least 10 m. (3) The influence of rock thermal conductivity parameters on temperature during the processes of hydrogen injection and natural gas extraction is also compared. The better the thermal conductivity, the deeper the thermal effects penetrate the rock layers, with the specific heat capacity having the most significant impact.

Flow-field analysis and performance assessment of rotating detonation engines under different number of discrete inlet nozzles

This study explores in depth rotating detonation engines (RDEs) fueled by premixed stoichiometric hydrogen/air mixtures through two-dimensional numerical simulations including a detailed chemical kinetic mechanism. To model the spatial reactant non-uniformities observed in practical RDE combustors, the referred simulations incorporate different numbers of discrete inlet nozzles. The primary focus here is to analyze the influence of reactant non-uniformities on detonation combustion dynamics in RDEs. By systematically varying the number of reactant injection nozzles (from 15 to 240), while maintaining a constant total injection area, the study delves into how this variation influences the behavior of rotating detonation waves (RDWs) and the associated overall flow field structure. The numerical results obtained here reveal significant effects of the number of inlets employed on both RDE stability (self-sustaining detonation wave) and performance. RDE configurations with a lower number of inlets exhibit a detonation front with chaotic behavior (pressure oscillations) due to an increased amount of unburned gas ahead of the detonation wave. This chaotic behavior can lead to the flame extinguishing or decreasing in intensity, ultimately diminishing the engine's overall performance. Conversely, RDE configurations with a higher number of inlets feature smoother detonation propagations without chaotic transients, leading to more stable and reliable performance metrics. This study uses high-fidelity numerical techniques such as adaptive mesh refinement (AMR) and the PeleC compressible reacting flow solver. This comprehensive approach enables a thorough evaluation of critical RDE characteristics including detonation velocity, fuel mass flow rate, impulse, thrust, and reverse pressure waves under varying reactant injection conditions. The insights derived from the numerical simulations carried out here enhance the understanding of the fundamental processes governing the performance of RDE concepts.

Longitudinal combustion instability in a hypergolic liquid bipropellant combustor with single dual-swirl coaxial injector

Self-excited longitudinal combustion instabilities were investigated in a hypergolic liquid bipropellant combustor, which applied single dual-swirl coaxial injector. Hot-fire tests were conducted for four different injector geometries, while extensive tests on injection conditions were carried out for each injector geometry. The synchronous measurement of the pressure and heat release rate was applied, successfully capturing the process of the pressure and heat release rate enhanced coupling and developing into in-phase oscillation. By calculating Rayleigh index at the head and middle section of the chamber, it is shown that Rayleigh index of the middle section is even higher than that of the head, indicating a long heat release zone. When the combustion instability occurs, the pressure in propellant manifolds also oscillates with the same frequency and lags behind the oscillation in the combustor. Compared to the oscillation in the outer injector manifold, the oscillation in the inner injector manifold shows a higher correlation with that in the chamber in amplitude and phase. Based on numerical simulations of the multiphase cold flow inside the injector and combustion process in the chamber, it is found that injector geometries affect longitudinal combustion instability by changing spray cone angle. The spray with small cone angle is more sensitive to the modulation of longitudinal pressure wave in combustion simulations, which is more likely to excite the longitudinal combustion instability. Meanwhile, the combustion instability may be related to the pulsating coherent structure generated by the spray fluctuation, which is determined by injection conditions. Besides, a positive feedback closed-loop system associated with the active fluctuation and passive oscillation of the spray is believed to excite and sustain the longitudinal combustion instability.

Local-Variable-Based Transition Model for Hypersonic Flows Considering Wall Mass Injection

Pyrolysis gas injection during the ablation process will affect the hypersonic boundary-layer transition. This paper proposes a three-equation γ-Reθ-fb transition model that considers wall mass injection. First, the boundary conditions of wall mass injection are established and verified. Second, based on analysis of the compressible boundary-layer solutions under wall mass injection, new transition correlations are developed. This allows an injection factor transport equation to be constructed using strictly local variables, and this equation is coupled with the γ-Reθ transition model. Additionally, to model the wall mass injection effects in the fully turbulent zone, the wall boundary conditions for the specific turbulence dissipation rate are amended. The results of numerical simulations show that the transition onset locations and the changes in the heat transfer rate are reasonably consistent with experimental data.

Fracture propagation characteristics driven by liquid CO2 BLEVE for coalbed methane recovery

Fracture propagation induced by liquid CO2 phase transition blasting (LCO2-PB) is the major reason for the spotty fracturing performance of LCO2-PB for enhancing coalbed methane (ECBM). Measures to effectively control the fracture propagation are of significant importance for ECBM recovery. Many researches to date have conducted the responses of the fracture propagation upon the CO2 fracturing under various injection conditions, and some have found that the thermodynamic state of CO2 can dominate the cracks distribution to some extent. This study therefore investigates the effect of various operated parameters of LCO2-PB on the fracture propagation alteration of coal seam subjected to the thermodynamic state of CO2 with different reservoir conditions. A series of fracture process simulations were performed based on the pressure–temperature-phase coupling model, and results indicate that high temperature of CO2 flow in the fracture process greater fracture expansion; the fracture width decreased around by 66.8 % from smaller smash district to larger one, especially for low CO2 flow rate; high elastic modulus and the temperature of coal seam favors greater length reduction and extensive crack connection, and as temperature of CO2 induces the interlaced fractures earlier formation in the higher reservoir temperature.

Experimental Investigations of Assessment of Acute Toxicity of Drilling Mud.

At present, the main technological stages of oil production related to drilling operations require the use of a wide variety of drilling mud, which has a complex, multicomponent chemical composition. The drilling mud used and the resulting drilling waste must be safe for human health and the environment. The toxicity and hazard of drilling mud at this point in time remain poorly understood scientific problems and require detailing and studying in toxicological terms. The real degree of hazard and toxicity of drilling mud can only be determined by an experimental method, since its composition, which changes depending on the nature of the technological process and its degree of depletion, is not constant, which can change the toxicological properties. In an experiment conducted on adult male rats, under conditions of a single intragastric injection of drilling mud, new data were obtained regarding the parameters of its toxicity and hazard. The use of a wide variety of methods for determining lethal doses of drilling mud, including the probit analysis method, made it possible not only to substantiate the mean lethal dose of drilling mud but also other parameters of toxicity and survival of animals in the experimental groups. Features of eating behavior and body weight dynamics and the nature of the behavioral reactions revealed by the number and duration of stands and frequency and duration of grooming also indicate the presence of dose-dependent effects.

Numerical study on enhanced-diffusion characteristics of kerosene jet in supersonic crossflow

The enhanced-diffusion characteristics of kerosene jet in supersonic crossflow under different supersonic mainstream and kerosene injection conditions were discussed in this paper. Numerous numerical simulations were conducted under varying shock wave intensities, injection momentum flux ratio conditions based on Euler-Lagrangian method. The influence of low-enthalpy (Tt=300 K) and high-enthalpy (Tt=1680 K) supersonic inflow conditions on kerosene diffusion was also involved. The results indicate that the momentum flux ratio caused by injection and evaporation jointly determines the diffusion ability of kerosene. The increase of injection momentum flux ratio and shock wave intensity promotes both the penetration ability and evaporation gain. However, the relative growth rate of penetration depth decreases, and the relative growth rate of evaporation penetration gain increases. As the jet momentum flow ratio decreases and the shock wave intensity increases, the mixing efficiency and relative growth rate of kerosene increase. A judicious design of injection measures proves to be an effective approach for enhancing the diffusion and mixing of kerosene, which holds significant importance in further enhancing the performance of supersonic combustors.

Investigation of models for predicting the effectiveness of acid treatments in carbonate deposits

This article presents the results of an analysis of the available literature data on the acid treatment of carbonates based on the solution approach. The analysis of various acid treatment liquids, the choice of additives and modeling procedures was also carried out in order to optimally design the process of acid treatment of carbonates. Although theoretical models are designed to predict the effectiveness of acid treatments, their practical applicability for scaling at the field level remains uncertain. Scaling laboratory data to the optimal rate does not always lead to results corresponding to the usual values of processing at the field. In modern models, it is proposed to use the geometry of the pipe to calculate the dominant penetration of wormholes and take into account the competition between them, introducing the density of wormholes in a porous medium. However, assigning values that are sensitive to the rock structure and injection conditions is a major difficulty. Instead of predicting the length of dominant wormholes, it is preferable to focus on estimating the permeability resulting from acid injection. However, the permeability assessment is not possible without first calculating the dissolution coefficient. The simulation results demonstrate that the existence of various zones of recesses or cracks in the formation has a significant impact on the acidification process, especially on the direction of wormhole propagation. This direction can be partially controlled by adding deflecting or retarding agents.

Experimental study on the mechanism of associated gas generation by heavy oil aquathermolysis and thermal cracking during steam injection

Previously, we proposed an innovative method for heavy oil recovery known as the ISSG-SAGD (in-situ solvent generation enhanced steam assisted gravity drainage) technique. This technology can improve heavy oil recovery efficiency, reduce steam consumption, and mitigate acid gas emissions. However, the reaction kinetic model used in numerical simulation was derived from literature reports and reasonable assumptions, lacking experimental validation. This study addresses this gap by conducting a series of experiments to investigate the mechanism of associated gas generation under steam injection conditions. We differentiated the reaction temperature window of aquathermolysis and thermal cracking based on the quantity and composition of the associated gas generated. The study revealed that aquathermolysis, occurring at 240–280℃, produces a small amount of associated gas (gasification degree of 0.32 %), predominantly CO2 (about 68 %). In contrast, thermal cracking, occurring at temperatures up to 380℃, significantly increases gas generation (gasification degree of 14.33 %), with light hydrocarbons (C1–5) constituting about 80 % of the gas produced. The reaction rate was found to be proportional to the reaction temperature and time. The SARA analysis showed that saturates and aromatics content increased, while resins and asphaltenes decreased after both reactions. A kinetic model for associated gas generation was established, and kinetic parameters such as activation energies and frequency factors were derived using the Arrhenius method. For example, the activation energy for CO2 generation increased from 18.19 kJ/mol during aquathermolysis to 147.58 kJ/mol during thermal cracking. This study provides a comprehensive understanding of the associated gas generation mechanisms and characteristics under steam injection, supporting the feasibility and potential application of the ISSG-SAGD technique in heavy oil recovery.

Investigating the Impact of Steam Enhancement on Combustion in a Swirl-Assisted Jet-Stabilized Gas Turbine Combustor

Abstract A newly developed gas turbine combustor system based on the swirl-assisted jet-stabilized concept using Jet A-1 and natural gas as reference fuel is tested under wet conditions to evaluate its combustion characteristics in the presence of steam. The effect of steam injection into the gas turbine combustor under both spray and superheated liquid fuel injection conditions is studied experimentally on an atmospheric test rig. To evaluate the effect of steam injection on combustion performance, the water-to-gas ratio (WGR) is varied from 0 to 32%. With increasing WGR = 0 to 16% and at stoichiometric condition, NOx reductions of -82% to -100% were observed during Jet A-1 and natural gas combustion, respectively. It is shown that the reduction of the combustion zone temperature due to the steam acting as a heat sink is the main cause of the NOx decrease. The operating range of the burner remained fairly constant for Jet A-1 until WGR = 20%, while it decreased significantly with increasing WGR for natural gas combustion. While the effect of the WGR on CO was modest, the greatest effect of the WGR was on the heat release zone intensity at a constant air to fuel ratio. In reducing the NOx levels of Jet A-1 and natural gas combustion, both thermal and chemical effects of steam injection were observed. However, steam acting as a heat sink and lowering the flame temperature, thereby reducing the thermal NO formation rate, was the dominant factor in NOx reduction.

Numerical investigation on direct water injection characteristics under different injection and ambient conditions within oxygen/argon atmosphere

Improving efficiency and reducing emissions are essential to achieve carbon neutrality in transportation sector. The hydrogen-fueled argon power cycle (H2-APC) is a novel power system with high efficiency and zero emission by utilizing argon-oxygen mixture as working fluids. However, knock suppression is a problem within H2-APC engines. Direct water injection (DWI) is an effective method to inhibit detonation. Spray morphology greatly influences the effectiveness of DWI, the investigation of spray characteristics in oxygen/argon atmosphere is critical. This paper established a computational model based on experimental data to investigate DWI characteristics under different injection and ambient conditions within oxygen/argon atmosphere. The results reveal increased jet temperature leads to stronger superheated jet spray collapse, while Sauter mean diameter (SMD) decreases and atomization improves. Increasing jet pressure effectively reduces spray SMD and improves atomization effect and evaporation rate. Higher ambient temperature reduces ambient gas density, spray SMD and penetration are decreased and increased, respectively. Moreover, spray evaporation rate and evaporated mass are dropped with higher ambient pressure for both superheated and subcooled sprays. As ambient density rises, the capacity for jet perturbation and fragmentation is enhanced, and spray SMD decreases. The research results can provide an effective guide for the DWI strategy of H2-APC engines.

Experimental research on gas flow and aerosol scrubbing characteristics under low Weber number pool scrubbing conditions

Radioactive aerosol may be released from the molten core during a severe accident in a nuclear power plant. Pool scrubbing, a representative aerosol scrubbing process incorporated in several severe accident scenarios, has been modeled in MELCOR. Under gas injection conditions with a low Weber number, gas flow regimes above the nozzle are globule and swarm. Based on visual scrubbing experiments, we investigated the gas flow and aerosol scrubbing characteristics under low-Weber-number injection conditions. We systematically analyzed the relationship between scrubbing efficiency and gas flow behavior through experiments and the applicability of the aerosol scrubbing model in MELCOR to different pool scrubbing conditions. Also, the variation of the globule and swarm shapes with the inlet pressure was obtained to evaluate the applicability of the gas flow model in MELCOR. Additionally, the bubble size distribution and Sauter average diameter were used to characterize the swarm flow characteristics based on the image processing results. Finally, we used a modified scrubbing model to compare the experimental results and evaluate the most suitable swarm characterization parameters.

Real-time fault-tolerant guidance for launch vehicle ascending flight under thrust drop failure

This paper presents a real-time fault-tolerant guidance method, which solves the autonomous rescue problem in the event of thrust drop failure during the final stage flight of launch vehicles. The core of the method is the online and optimal reconstruction of both the degraded target orbit and the subsequent flight trajectory. Aiming at achieving satisfied onboard computing performance and making the best use of the launcher’s residual energy, a unique relaxation-penalization model transformation method for the nonlinear orbit injection conditions is proposed, and a successive convexification algorithm is developed to solve the problem. Furthermore, both the two classic thrust drop failure situations, that is the mass flow rate drop and the specific impulse drop problems, can be resolved by the proposed algorithm. The average run-time of this orbit-trajectory joint optimization algorithm is below 150ms in an embedded ARM processor @1.5 GHz, which is adequate for onboard use. Using the above algorithm as a central infrastructure, a receding-horizon-strategy-based fault-tolerant guidance method is proposed. By performing the optimization repeatedly at a high frequency, the effects of parameter deviations and external disturbances can be absorbed for the most part, for example, the guidance algorithm is verified to be capable of tolerating at least ±5% thrust deviations. Comprehensive numerical and hardware-in-the-loop simulations are performed to demonstrate the computational performance, accuracy, and reliability of the proposed algorithms.