Injection Position Research Articles

The coupling effect of turbulent jet ignition and injection strategy on the combustion performance of a pure methanol rotary engine

Methanol, as an alternative fuel, has significant potential in energy conservation and emission reduction. However, the higher ignition temperature and latent heat of vaporization of methanol fuels also expose engines to the risk of cold-starting difficulties. The turbulent jet ignition (TJI) technology, aimed at enhancing ignition energy, proves effective in improving the ignition and combustion performance of pure methanol. Therefore, this study designed a jet ignition plug to optimize the combustion characteristics of methanol rotary engines. Meanwhile, the influence of injection strategy on the performance of the patterned turbulent jet ignition rotary engine(TJI-RE) was studied for the first time. On this basis, the CFD model of pure methanol TJI-RE was established and validated using relevant experimental data. Results found that the injection angle and position could change in-cylinder fuel distribution during ignition, as well as the quality of fuel entering the pre-chamber, affected by fuel impact position and in-cylinder vortex strength. These factors collectively influenced the combustion characteristics of TJI-RE. Furthermore, the optimal fuel distribution characteristics for TJI-RE included higher fuel concentration in the pre-chamber and increased fuel accumulation in the front of the cylinder Under all calculation conditions, the configuration with the fuel injector positioned 25 mm above the cylinder’s long axis and an injection angle of +50° achieved the highest peak pressure and indicated thermal efficiency for TJI-RE.

Assisting denitrification and strengthening combustion by using ammonia/coal binary fuel gasification-combustion: Effects of injecting position and air distribution

The direct co-firing of ammonia (NH3) with coal is an effective approach for reducing carbon emissions from coal-fired plants. However, the limitations of NH3 combustion, such as its high ignition energy requirement and high NOx emissions, restrict its large-scale co-combustion in coal-fired units. In this study, a self-sustaining gasification–combustion experimental system was employed, and its denitrification performance and combustion strengthening capability for NH3/coal binary fuel under different NH3 injection positions and air distribution methods were evaluated. The results of co-firing 20% NH3 in the gasifier revealed that its operating temperature can be flexibly controlled within the optimal reaction temperature window of SNCR by adjusting the primary air ratio (λ1). Increasing λ1 was beneficial for NH3 and coal conversion and denitrification in the gasifier; at λ1 = 0.53, the conversion rate of NH3 and N2 reached 86.37% and 83.59%, respectively, with no NOx being detected at the gasifier outlet. Furthermore, increasing λ1 promoted the development of gasified char pore structure, thereby improving reactivity. After entering the down-fired combustor (DFC), increasing λ1 promoted NH3 and coal burnout and effectively controlled NOx emissions, reaching a level similar with that of pure coal under λ1 = 0.53. Co-firing 20% NH3 in the DFC also demonstrated that the introduction of inner secondary air was conducive to char burnout, however, increased NH3 slip. The outer secondary air promoted NH3 combustion, however, exacerbated NOx emissions and inhibited gasified char combustion. The uniform air distribution method balanced the combustion of NH3 and gasified char, and effectively controlled NOx emissions. When the same air distribution method was used, co-firing NH3 in the gasifier was more favourable for NOx control, whereas co-firing NH3 in the DFC benefited coal burnout. This study provides innovative ideas and serves as a reference for developing enhanced combustion and low NOx emission technologies for large-scale NH3 co-firing in coal-fired units.

Numerical investigation on combustion performance optimization with strut/wall combined-staged injection strategy within an axisymmetric variable geometry combustor at Mach 3

Numerical simulations were conducted on the strut/wall multistage injection strategy to optimize the combustion performance at Mach 3. Two kinds of the combustion models were used: The Eddy-Dissipation Model (EDM) was used first to highlight the effects of mixing performance on the combustion performance; then the Finite-Rate/Eddy-Dissipation Model (FR/EDM) was used to modify the influence mechanism of wall injection positions by incorporating with finite-rate reaction effects. The combustion process was divided into three stages to analyze the average heat release rate and the contribution of average total temperature change of each stage to identify the key influencing factor of each stage. The results indicated that under low flight Mach number conditions, the finite-rate reaction effects exerted a more pronounced influence on the combustion. The strut/wall multistage injection strategy was found to be an effective means of enhancing combustion, with the positive feedback between the strut flame and the wall flame being particularly influential. Additionally, apart from the mixing efficiency, the distribution of heat release length of each stage also emerged as a critical factor in determining combustion performance. By adjusting the wall injection positions, the better combustion performance and the bigger working stability of the combustor could be achieved. The study elucidated the regulatory strategy of wall injection positions on combustion performance, offering value insights for optimizing combustion performance under low Mach number conditions.

Study on multi-field coupling characteristics of underground coal combustion and nitrogen injection parameter optimization

Underground coal fires, which are widely distributed and cause serious resource waste and environmental hazards, have become a common concern of the international community. This paper aims to reveal the mechanism of coal spontaneous combustion and the expansion law of underground coal fires. A void rate model from the goaf to the ground surface and a multi-field coupling model for underground coal fires were established. Based on which, the combustion process from the beginning of oxidation to the formation of large-scale fire of the remaining coal in goaf was analyzed. Furthermore, the evolution law of underground coal fire after nitrogen injection and the influence of different nitrogen injection parameters were analyzed. The results show that the coal spontaneous combustion can be divided into three stages: slow reaction stage (stage Ⅰ), violent combustion stage (stage Ⅱ), and stable combustion stage (stage Ⅲ), and the transformation of different stages is mainly controlled by the oxidation reaction rate of coal. To obtain the optimal parameters for nitrogen injection for fire suppression, the fire extinguishing efficiency concerning nitrogen injection time, nitrogen injection amount and nitrogen injection position, as well as the distribution law of nitrogen in rock strata were analyzed. Through range analysis, it is determined that the most effective fire extinguishing occurs with the injection rate of 0.15 m3/s in stage I, and the injection position has little influence on the fire extinguishing effect. This understanding contributes to a deeper understanding of the multi-field coupling mechanism of underground coal fires and provides a guidance for extinguishing and preventing underground coal fires.

Experimental study of NO emission in coal-methanol co-combustion under air-staged condition

Application of renewable methanol as an alternative fuel is a promising method for both CO2 and NO emission reduction in thermal power plants fueled by coal. This work gives the first insight into coal-methanol co-combustion from the perspective of NO emission control with a wide range of methanol blending ratio (0%–100 %) involved. Air-staged strategy commonly applied in thermal power plants fueled by coal was considered, and the effects of some key parameters, including burnout air ratio, burnout air injection position and furnace temperature, were analyzed. Experimental results show a significant potential of NO emission reduction in coal-methanol co-combustion, as NO emission from methanol combustion is less than 30 % of that from coal combustion. The correlation between NO emission and methanol blending ratio is approximately linear. Air-staged strategy is still effective for NO emission reduction in coal-methanol co-combustion, and the effects of the key parameter is similar to that in coal combustion. Increase of burnout air ratio and delay of burnout air injection are beneficial, and NO emission can be reduced by more than 70 % compared with that under unstaged condition. Furnace temperature rise is harmful, whereas the corresponding NO emission increase is lower than 30 ppm (@6 % O2).

NUMERICAL AND EXPERIMENTAL RESEARCH ON THE DI-CI ENGINE PERFORMANCE CHARACTERISTICS UNDER LPG - DIESEL DUAL FUEL COMBUSTION MODE

Properties of Liquefied Petroleum Gas (LPG) are suitable as an alternative fuel for internal combustion engines. This work aims to combine both numerical optimization analysis of LPG injector placement angle and subsequent experiment with selected mounting injector angle to investigate the effects of using LPG as a parallel-partial substitute fuel with diesel fuel under dual-fuel combustion mode. An electronic injection fuel control system was applied to the modified intake manifold to generate the appropriate LPG injection. Three mounting angle injector positions including 450, 900 and 1350 in the upstream direction of intake air have been defined by Ansys Fluent to take into account efficient LPG-air mixing. Then, the experiment was conducted with LPG-diesel dual-fuel combustion mode (DFC mode) and compared to entirely diesel combustion mode as baseline data. Different load conditions ranging from idle to 4.0 kW were imposed at a constant engine speed of 1700rpm. The obtained results revealed that the injector’s mounting angle position by 45 opposite to the intake air flow showed the correlation with the calculated LPG-air ratio in dual fuel combustion reaction. In DFC mode, the brake thermal efficiency (BTE) decreased on average by 4.6% and the LPG substitution rate gradually decreased while brake-specific fuel consumption (BSFC) increased for all engine loads. The exhaust temperature in the dual-fuel combustion mode was found to be higher than that of full diesel fuel mode at low loads (less than 2.5 kW) and began to decrease at higher loads.

Carbon-free power generation strategy in South Korea: CFD simulation for ammonia injection strategies through boiler burner configurations in tangentially fired boiler

To achieve carbon neutrality in power generation, incorporating ammonia-coal co-firing into coal-fired boilers effectively reduces CO2 emissions. Here, we aimed to optimize ammonia injection methods by investigating the feasibility of 20 % ammonia co-firing in a pulverized coal (PC) boiler through numerical simulations. These simulations aim to analyze the effects of different ammonia injection strategies and burner configurations on the combustion performance and NOx emission characteristics of a 500 MW tangentially fired PC boiler. Results showed that compared to using five burners, single-burner injection reduced outlet NO concentration by 22.72 ppm and unburned carbon content to 0.30 %, which is 0.80 % lower than multi-burner injection and even below the 0.45 % in coal-only combustion. The optimal case (burner A for ammonia injection) achieved a furnace outlet flue gas temperature of 1247.35 K, close to 1241.98 K in coal-only combustion, with the lowest NO emissions (193.89 ppm) among all ammonia co-firing cases. Positioning the single burner for ammonia injection revealed that utilizing the blending method with the ammonia injection burner, such as in the case of upper burner injection, increases both furnace temperature and high-temperature zone areas. However, employing in-boiler blending methods with lower-positioned burner ammonia injection distributes high-temperature zones more extensively. Comparing ammonia injection through coal and auxiliary oil burners, using only the lowest-level burner can significantly reduce NOx emissions while maintaining combustion and thermal efficiencies. This study is the first to simultaneously consider the number, position, method, and type of ammonia injection burners in large-scale commercial coal-fired boilers, providing a valuable reference for future research and practical boiler operations. This comprehensive analysis underscores how ammonia injection strategy and position can optimize ammonia-coal co-firing boiler performance.

Combustion characteristics on ammonia injection velocity and positions for ammonia co-firing with coal in a pilot-scale circulating fluidized bed combustor

Ammonia (NH3) co-firing with coal in thermal power plant offers a viable solution for reducing CO2 emissions. Optimizing the NH3 injection method is crucial to achieving comparable performance and pollutant emissions in NH3–coal co-firing compared to coal only combustion in a circulating fluidized bed combustion system. The impact of NH3 co-firing with coal on the injection velocity and location in related to the NH3 supply method was evaluated. Injection velocity was controlled by varying the number of ammonia supply ports and their heights (0.2 m and 1.8 m from the distributor). Injecting NH3 through one port at a high velocity of 2.4 m/s increases CO emissions while decreasing NO emissions due to the formation of a reducing environment. Conversely, utilizing two ports with low NH3 injection velocity of 1.2 m/s exhibited the opposite trend in CO and NO emissions, achieving the highest combustion efficiency without the formation of N-containing components. This injection velocity promotes better mixing of gases (air and NH3) and solids (bed materials and coal) without hindering coal combustion. Regarding greenhouse gases emissions, the part of CO2 emissions decreased by considering CO2 concentration and flue gas flow rate, while the part of N2O emissions significantly increased due to N-chemistry by > 5 times.

Effects of relative position of injectors on the performance of ammonia/diesel two-stroke engines

A numerical study was conducted to investigate the impact of the relative position of injectors on the performance of ammonia/diesel two-stroke engines under typical marine operating conditions characterized by a 50 % load and a high ammonia energy ratio of 80 %. The results show that there are three combustion modes as the relative position of the diesel injectors changes. In the first combustion mode, the ammonia/diesel injectors are positioned adjacently, with the diesel injectors upstream. As the ammonia/diesel injectors are repositioned further apart, there is a slight reduction in indicated thermal efficiency and an increase in NOx emissions, accompanied by a slight rise in unburned ammonia and greenhouse gas emissions. In the second combustion mode, the ammonia/diesel injectors are spaced further apart. The fully developed diesel flame front end ignites its downstream ammonia spray, and its upstream ammonia spray is difficult to ignite, resulting in increased unburned ammonia and greenhouse gas emissions. In the third combustion mode, the ammonia/diesel injectors are positioned adjacently with the diesel injectors downstream. As the ammonia/diesel injectors are closer, the indicated thermal efficiency shows a significant decrease trend, with an increase in NOx emissions, while unburned ammonia and greenhouse gas emissions remain at lower levels.

Experimental and numerical studies of NO reduction by ammonia in different methane flame positions

Blending ammonia with methane for combustion can reduce carbon emissions and improve the flame characteristics of ammonia combustion. However, blending ammonia with methane can easily lead to high concentrations of NOx emissions. This study investigates the impact of different ammonia and methane blending methods on the flame structure and NOx emission by experiments and CFD numerical simulation. The results indicate that simultaneous injection of ammonia and methane through the central fuel tube significantly alters the combustion flame structure and leads to high concentrations of NOx emission. As the ammonia ratio increases, the flame structure transitions from a bright flame to a layered flame with an inner yellow conical small flame surrounded by a light-colored outer flame. When the ammonia ration increases from 0 % to 20 %, NOx emission increase from 15 ppm to 323 ppm, nearly 22 times higher. When ammonia is injected into the methane flame from flame side, the flame above the injection position appears as an orange flame, and a significant reduction in NOx emission is obtained. When the ammonia ratio is 20 % and injected at heights of 20 mm 40 mm, and 60 mm above the fuel exit, the outlet NOx concentrations are 183 ppm, 140 ppm, and 153 ppm respectively, this represents reductions of 43.3 %, 56.6 %, and 52.6 %, respectively. The numerical simulation results indicate that the injection of ammonia leads to the formation of higher concentrations of NH2 and super-vapor H2O, resulting in an orange color flame. The gas temperature and oxygen concentration play a crucial role in NOx emissions. NOx emission is lowest when ammonia is injected into the higher temperature, lower oxygen environment at 40 mm.

Development of a Graded Early Warning Index System and Identification of Critical Temperatures for Coal Spontaneous Combustion Using Composite Gas Characteristics.

Conventional single gas alarm method and coal spontaneous combustion three-stage alarm method have become increasingly inadequate to meet complex underground conditions. To address this issue, this study focuses on the coal in the goaf of the Z109 working face in the Donggucheng Mine as the research object. Through program-controlled heating experiments, the production of carbon monoxide and hydrocarbon gases during the coal oxidation process was determined, and the variation characteristics of gas ratios with temperature were further analyzed. The coal spontaneous combustion process was subdivided into seven small stages, and a quantitative composite parameter coal spontaneous combustion grading warning system was formulated. Based on its characteristics, measures to be taken under different warning levels were proposed, and it was determined that 120, 140, and 160 °C are the key temperatures for coal spontaneous combustion prevention and control in the Z109 working face of Donggucheng Mine. By using numerical simulation, the optimal nitrogen injection position for the working face was determined and the on-site fire prevention and extinguishing measures were optimized, providing insights into the establishment of a coal mine spontaneous combustion warning system.

Combustion characteristics analysis and performance evaluation of a hydrogen engine under direct injection plus lean burn mode

Direct injection plus lean burn technology can effectively control combustion processes and reduce carbon emissions of hydrogen engines. Hence, hydrogen direct injection strategy optimization is a key means to improve engine performance and achieve low emissions. Thus, a three-dimensional transient calculation model coupled chemical reaction mechanism is established, and its reliability and accuracy are systematically evaluated using experimental data. Then, the effects of hydrogen direct injection strategies on the hydrogen-air mixing and combustion process are investigated. The results indicate that the ideal mixture stratification law is that the gas fuel concentration is gradually stratified from the ignition center to the periphery region. The maximum indicated work is obtained for the B-60° scheme which its injection position is near the intake side and 7.5 mm from the cylinder center on the X-axis. The optimal hydrogen injection angles vary with different injection positions by evaluating engine performance, specifically, 60° is optimal for injection position B, while 30° is best for injection position C which is between intake and exhaust and 40 mm from the cylinder center on the Y-axis. Finally, the achieved maximum thermal efficiencies of 41% and indicated power of 4.29 kW for the B-60° scheme, and its nitric oxide can meet the Europe V emission standards (7.5 g/kWh). This research can offer theoretical guidance for designing and optimizing fuel injection strategies for hydrogen energy engines, and it is relevant for promoting carbon neutrality and cleaner production.

Progress and challenges in the design of ITER's polarimetric Thomson scattering diagnostic system.

Polarimetric Thomson scattering (PTS) is a technique that allows for accurate measurements of electron temperature (Te) in very hot plasmas (Te > 10 keV, a condition expected to be regularly achieved in ITER). Under such conditions, the spectral region spanned by the TS spectrum is large and extends to low wavelengths, where the transmission of the collection optics decreases, available detectors are less efficient, and the high level of plasma background light perturbs the measurements. This work presents the recent developments in the design of a PTS system for ITER, along with the challenges posed by the complex machine design. The system performance is assessed for an updated geometry (with respect to previous publication), showing that, with a scattering angle θscat = 167°, the expected signal is strongly reduced. Potential alternatives are analyzed: (1) a system employing a different laser injection position, allowing for a more favorable scattering angle and (2) a recently proposed dual-polarization laser pulse technique. The latter is evaluated for the possible ITER geometry, again showing that a more favorable scattering angle is needed for a robust performance.

Effect of incoming flow conditions on air lubrication regimes

Different air phase regimes are formed by controlled air injection in a spatially developing flat plate turbulent boundary layer (TBL). The air is introduced via a slot type injector without the use of a backward-facing step or cavitator upstream of the air injection position. The effect of different incoming liquid flow characteristics on the different regimes is investigated by varying both the liquid freestream velocity and the incoming TBL thickness. The latter is realized through changing the position of the air injection along the length of the water tunnel facility. That resulted in a downstream distance based Reynolds number from 1 to 5 million. Three different air phase regimes are identified under different air flow rates and freestream velocities: the bubbly regime, the transitional, and the air layer regime. The morphological differences of each one are described and quantitative analysis is performed based on the non-wetted area in each condition. The incoming TBL as well as the flow around the air layer are measured with planar particle image velocimetry. The latter enabled the determination of the air layer thickness. In addition, the ratio of the air layer to the incoming boundary layer thickness tair/δ is also calculated (≈ 0.04 – 0.5). This is a significant dimensionless parameter for scaling, which indicates the extent to which the air layer is embedded within the incoming TBL. Depending on the incoming flow conditions, a two or three branch air layer is formed. The length of the air layer is found to increase with increasing liquid freestream velocities. A good agreement between the air layer length and a half gravity wave predicted by the dispersion relation is found. An increase of the air layer length is observed with a decreasing incoming TBL thickness. This is attributed to a decrease in the local mean velocity at the air–water interface due to the TBL growth. Finally, increasing the incoming TBL thickness delays the onset of the air layer regime.

Experimental investigation of steam and carbon dioxide influence on methane filtration combustion in a reversal flow porous media reactor

A reverse flow porous medium reactor with premixed and non-premixed flames was experimentally investigated to evaluate the influence of steam and carbon dioxide on methane (CH4) filtration combustion for syngas production. Premixed, non-premixed, and non-premixed with steam were the tested cases for different injection configurations. Thermal profiles, combustion products, hydrogen (H2) and carbon monoxide (CO) yields for several equivalence ratios are analyzed. Non-premixed case exposed higher maximum temperatures due to the reactant accumulation at the crosswise injection position, with a temperature of 1615 K. The lack of homogenization of the reactants in this configuration leads to low H2 and high CO concentrations compared to the premixed case. The maximum CO yield was 92.81% for the non-premixed configuration with alternated air injection, while the maximum H2 yield was 37.8% for the premixed air-methane-steam case. It was found that the air-methane-carbon dioxide mixtures had lower temperatures, combustion wave velocities, and H2 and CO concentrations, compared to the air-methane, and air-methane-steam mixtures, but higher CH4 and CO2 concentrations. The premixed configuration with air-methane-carbon dioxide mixture showed higher temperatures, and H2 and CO concentrations, compared to the non-premixed configuration. Further studies are necessary to optimize the operation of these types of reactors.

Numerical simulation of hydrogen co-firing distribution on combustion characteristics and NOx release in a 660 MW power plant boiler

The article discussed the influence on furnace temperature distributions, combustion characteristics, and NOx release when hydrogen, coal, and sludge co-firing in a 660 MW power plant boiler by CFD. Non-premixed combustion model was chosen as the gas combustion model. As the height of the hydrogen injection position rises, the temperature difference in the main combustion region decreases from 297.22 K to 94.72 K. The co-combustion of hydrogen inhibits solid fuels' combustion. As hydrogen nozzles' height decreases, the NOx mass at the furnace outlet increases from 98.41 % to 160.38 %. When the excess air coefficient changes from 1.15 to 1.35, the temperature in the main combustion region significantly increases, while the temperature in the upper furnace decreases, and the heat flux of the main combustion region increases by 11.10 %, the heat flux of the total furnace decreases by 1.39 %, the NOx mass at the furnace outlet increases by 31.67 %. The optimum co-combustion method is injecting the hydrogen from the top hydrogen nozzles and the excess air coefficient is 1.15, the overall impact on the furnace is minimal in this way. The fundamental reason hydrogen affects co-combustion is the fuel characteristics’ difference between hydrogen and solid fuels.

Numerical research on refrigerant injection for motor cooling of screw compressor for heat pump with large temperature lift

In the screw compressor for heat pump with large temperature lift, the large load on the motor makes the motor heat up severely. The stability and safety of the motor directly affects the operation of the compressor. High motor temperatures or strong impact on winding will destroy the insulating coating on the copper wires of the motor winding, which could cause the motor to burn out. Refrigerant injection for motor cooling is an effective way of motor cooling. There is a lack of research on this method. In this paper, a computational fluid dynamics model containing evaporation–condensation and conjugate heat transfer is developed. In order to reasonably simulate the evaporation–condensation process, the physical parameters varying with temperature of the refrigerant are taken into account. The temperature field of the screw compressor by refrigerant injection for motor cooling is predicted, and the accuracy of the model is verified through experiments of an R134a heat pump with large temperature lift. The maximum discrepancy between the simulation results and the experimental results under four working conditions does not exceed 3.0%. Next, the effects of the injection pressure and the injection position on motor cooling, impact caused by refrigerant injection and temperature uniformity are investigated. The results show that by adjusting the injection pressure to make the refrigerant two-phase mixture, the impact caused by refrigerant injection is reduced by 57.0%, while the cooling effect is reduced by only 9.0%. By choosing the injection position appropriately, the cooling effect is increased by 12.0% and the impact caused by refrigerant injection is reduced by 21.2%. In addition, the temperature in the middle of the motor is the highest before refrigerant injection, so the motor temperature sensor should be arranged in the middle of the motor winding.

Surface Pressure Measurement of Truncated, Linear Aerospike Nozzles Utilising Secondary Injection for Aerodynamic Thrust Vectoring

A cold-gas test campaign has been conducted at the DLR’s P6.2 test bench in Lampoldshausen, with the objective of investigating the linear aerospike nozzle flow in interaction with secondary injection thrust vector control (SITVC). In this campaign, the influence of nozzle truncation, injection position and injection pressure on the nozzle surface and base pressure is analysed using pressure probes and Schlieren flow-visualisation techniques. The effects of injection position and truncation on the nozzle surface pressure development are comparable for all geometric variations, resulting in a locally increased static pressure upstream and a locally decreased static pressure downstream of the injection. The magnitude and dimension of these high- and low-pressure regions are correlated with the injection pressure. However, the influence of injection position and truncation on the base pressure is not entirely predictable by the named parameters, indicating an interdependence between both geometric parameters. Finally, the required pressure ratio of injection to the primary flow to ensure sonic injection has been analysed on TUD’s cold-gas test bench. This allows the respective injection position-dependent threshold to be identified. The analysis reveals that these experiments have been conducted under transsonic injection conditions.

Novel design of multi-point injection system for laboratory simulation of Martian low-pressure dust devils

The Martian surface is frequently traversed by dust devils, presenting formidable challenges to exploration missions and posing significant safety risks. Establishing a ground-based simulation device for low-pressure Martian dust devils is essential for conducting reliability testing and research on extreme environments relevant to Mars rovers. This study introduces a Martian dust devil simulator comprising a simulation cabin and multi-point injectors. This apparatus facilitates the investigation of velocity and pressure distribution patterns within the flow field under varying operational conditions by adjusting injector positions, inlet pressure, and internal pressure. The simulator's design allows it to replicate Martian dust devil velocity fluctuations from 0 to 50 m/s and pressure variations spanning 100–1500 Pa, thereby meeting crucial criteria for simulating Martian atmospheric conditions. Through computational fluid dynamics (CFD) simulation, we analyzed the characteristics of dust devils generated by the simulation device and scrutinized the flow field properties following the coupling of sand-dust particles with airflow. The observed dust devil flow field closely resembles the Vastitas Borealis vortex. Additionally, experimental research was conducted. Comparing experimental, simulated, and theoretical models revealed a high degree of consistency in the internal flow field characteristics of the simulated dust devils. The apparatus's versatility extends to simulating various dust devil morphologies, offering significant potential for conducting model experiments pertinent to Martian probes and facilitating future crewed Mars exploration endeavors.

Influence of Incident Shock on Fuel Mixing in Scramjet

During the operation of hypersonic vehicles, a reciprocal coupling effect is manifested between the inlet and the combustion chamber. This results in an unavoidable non-uniformity of conditions at the combustion chamber’s entrance, which, in turn, influences the fuel mixing within the chamber. The present study employed the Reynolds-averaged Navier–Stokes (RANS) equations to perform a numerical simulation of an X-51-like vehicle, with a focus on examining the impact of isolation section length and multi-injection strategies on the fuel mixing characteristics within the combustion chamber under conditions of non-uniform inflow. The findings indicated that a supersonic non-uniform inlet triggers incident shock waves, leading to a non-uniform pressure distribution across the flow section. Moreover, the position of injection was found to be pivotal in regulating penetration depth and mixing efficiency. The incident shock wave, bow shock, and boundary layer separation shock interacted with each other to increase local pressure. The coupling of high and low pressures generated an adverse pressure gradient that led to boundary layer separation, which further enhanced fuel penetration depth.