Experimental Thermal and Fluid Science最新文献

{"title":"The effect of low swirl configurations on stability limits and emission characteristics in premixed ammonia-methane-air swirling flames","authors":"Haojie Yang,&nbsp;Chunyu Liu,&nbsp;Boshu Dong,&nbsp;Xuejiao Li,&nbsp;Liang Yu,&nbsp;Xingcai Lu","doi":"10.1016/j.expthermflusci.2024.111361","DOIUrl":"10.1016/j.expthermflusci.2024.111361","url":null,"abstract":"<div><div>Ammonia has recently gained significant attention as a zero-carbon fuel and a carrier of hydrogen. However, its flame instability and emissions remain major challenges. In this study, the effect of low swirl configuration on stability limits and emissions of premixed ammonia-methane-air swirling flames at various equivalence ratios and ammonia blending ratios were investigated. The low swirl configuration was achieved by using three center through-hole swirlers with different mass fluxes ratio (<em>R_m</em>) for non-swirling and swirling flows. The results showed that the flames exhibited thermoacoustic instability at <em>R_m</em> = 0 % and detected higher emissions for all conditions where the ammonia mixing ratios are less than 60 %. By contrast, the swirlers with <em>R_m</em> = 25 % and <em>R_m</em> = 49 % ensured flames stabilization under all operating conditions. The swirler with <em>R_m</em> = 25 % effectively reduced NO_x emissions about 30 % while slightly narrowing the stability limits. CO and unburned NH₃ emissions also decreased significantly, but N₂O emissions increased. This was due to the non-swirling flow reduced the flame temperature, which inhibited the thermal cracking of N₂O. As <em>R_m</em> = 49 %, the stability limits became very narrow, although the emissions decreased further. In conjunction, it is found that increasing <em>R_m</em> caused the flame structure to shift from the V-shape to the W-shape, with the flame obviously lifting and the recirculation zone in the flow field shrinking. These changes are responsible for the transformation of the stability limits and emission with different low swirl configurations, which provide a feasible idea for use of ammonia as a gas turbine fuel to improve combustion efficiency and reduce emissions.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"162 ","pages":"Article 111361"},"PeriodicalIF":2.8,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental investigation on heated spheres entering water vertically at different temperatures","authors":"Hui Qi ,&nbsp;Hao Wu ,&nbsp;Zhiyu Fan ,&nbsp;Sining Li ,&nbsp;Yongbin Jia ,&nbsp;Xianglong Yang ,&nbsp;Shiqi Zhang ,&nbsp;Jing Guo","doi":"10.1016/j.expthermflusci.2024.111360","DOIUrl":"10.1016/j.expthermflusci.2024.111360","url":null,"abstract":"<div><div>Our investigation of spheres entering water at high-temperature reveals that elevated temperatures modify traditional cavitation patterns and trigger novel fluid dynamic phenomena. Experimental analysis of the high-temperature sphere’s water entry process has identified four distinct cavitation morphologies: small cavities, complete cavities, dual cavities, and unstable cavities. These phenomena result from the sphere’s thermal effects altering the local flow dynamics around it, consequently impacting the hydrodynamic coefficients. Notably, thermal conditions cause the contact line from the sphere’s midpoint to transition to its tail, leading to transformations in cavity types. Furthermore, simulations employing the lattice Boltzmann method elucidate how unstable steam films formed on hot surfaces induce boundary slip, reducing pressure drag. This observation provides further insight into established mechanisms of fluid drag reduction. Our study deepens the understanding of how temperature influences water entry dynamics and offers new perspectives on reducing drag during the water entry process of objects.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"162 ","pages":"Article 111360"},"PeriodicalIF":2.8,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A novel resonant mode drives the dynamics of a large-cavity synthetic jet actuator","authors":"L.F. Olivera-Reyes,&nbsp;E.S. Palacios de Paz,&nbsp;S. Sánchez,&nbsp;J.F. Hernández-Sánchez","doi":"10.1016/j.expthermflusci.2024.111356","DOIUrl":"10.1016/j.expthermflusci.2024.111356","url":null,"abstract":"<div><div>Synthetic Jet (SJ) actuators are an intrinsically complex combination of electronics, electric and mechanical systems. When studied theoretically, these elements are often simplified to coupled damped harmonic oscillators (DHO) that induce a pressure field within the cavity and drive momentum exchange. Thus, the dynamics of an SJ actuator result from coupling these DHOs, naturally leading to a few resonant modes. There is good evidence in the specialized literature of two resonant modes developing in SJ actuators: the membrane/piezoelectric mode and the Helmholtz resonance. In this work, we report on the effect of a new resonant mode that dominates the two traditional modes when it develops. We present evidence that the resonant mode develops when the cavity is much larger than the volume displaced by the actuator. The new resonant mode is biased to lower frequencies and has a flatter response along the frequency band than other resonant modes. We show that jet and vortex velocities mimic the sound pressure curve for the low-frequency range. Its effect mitigates for the higher range due to a delve through shorter stroke lengths, characterized through the well-documented formation criteria as a fixed relation between the Reynolds and the Stokes numbers. We further characterize the new resonant mode by comparing its intensity with standard room modes. We also show that the resonant mode may be dimmed and focused by adding an obstacle in different cavity positions for the lower sound intensities. We consider that the large-cavity dynamics is an additional element that, if integrated as design criteria, could extend the applicability of SJs and their optimum response.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"162 ","pages":"Article 111356"},"PeriodicalIF":2.8,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PIV experimental study on dynamic and static interference flow field of multi-operating centrifugal pump under the influence of impeller wake","authors":"Leilei Ji ,&nbsp;Wei Pu ,&nbsp;Wei Li ,&nbsp;Weidong Shi ,&nbsp;Yang Yang ,&nbsp;Cui Xiao ,&nbsp;Fei Tain ,&nbsp;Jie Zhou ,&nbsp;Ramesh Agarwal","doi":"10.1016/j.expthermflusci.2024.111355","DOIUrl":"10.1016/j.expthermflusci.2024.111355","url":null,"abstract":"<div><div>In order to study the influence law of the impeller wake on dynamic and static interference flow field of the centrifugal pump, this paper obtains the dynamic and static interference flow field of the centrifugal pump under different flow conditions (15 m³/h, 50 m³/h, 70 m³/h) based on PIV technology, and analyzes the influence mechanism of the impeller wake change on dynamic and static interference flow field. The results show that rotating stall occurs in the centrifugal pump under low flow condition, but it has little effect on the head loss in the centrifugal pump. In the dynamic and static interference flow field, under the condition of the low flow rate, the impeller wake collides with the baffle tongue, resulting in serious velocity fluctuation, and then there will be the secondary collision with the volute wall, which will eventually cause the wake to dissipate, and the change process of the wake shows the periodic characteristic. In the design condition and the large flow condition, the spacer tongue will have the cutting effect on the wake, and the high-speed accumulation phenomenon will occur in the volute flow path near the spacer tongue. In the side flow path of the volute, under the condition of the low flow, the impeller wake is mainly located at the exit of the impeller, and the end of the impeller wake is easy to fall off and gradually break up under the impact of the main stream. Under the design condition, the flow stability is good, and the wake vortex is close to the trailing edge of the blade, and there is no obvious shedding phenomenon. Under the condition of the large flow rate, the velocity fluctuates sharply, and many large-scale vortex structures appear on the cross section of the flow channel due to the cutting of the wake near the diaphragm tongue. In the impeller passage, the movement and distribution of the wake are significantly affected by changes in flow conditions. The research results provide a basis for optimizing volute channel.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"161 ","pages":"Article 111355"},"PeriodicalIF":2.8,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142700110","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of a perforation on the flow characteristics of corrugated wall","authors":"Linmeng Yu ,&nbsp;Jiao Sun ,&nbsp;Kangfu Sun ,&nbsp;Pengda Yuan ,&nbsp;Wenyi Chen","doi":"10.1016/j.expthermflusci.2024.111358","DOIUrl":"10.1016/j.expthermflusci.2024.111358","url":null,"abstract":"<div><div>The flow characteristics on a corrugated wall and the variations caused by a perforation are investigated experimentally based on two-dimensional particle image velocimetry (PIV), and the passive control mechanism of the perforation on the corrugated wall is studied. The corrugated wall has an amplitude-to-wavelength ratio 2<em>a</em>/<em>λ</em> = 0.1, with the wavelength Reynolds number Re<em>_λ</em> = 14400 and bulk Reynolds number Re<em>_b</em> = 17500. The perforation is located on the eleventh cycle of the corrugated wall. The results show that perforation increases the area of the recirculation zone, reduces the effect of frictional resistance, weakens the turbulence intensity and the Reynolds normal stress on the corrugated wall, but enhances the Reynolds shear stress. The POD and the Finite-Time Lyapunov Exponent(FTLE) are used to analyze the vortex structures. From the FTLE result, it can be seen that the perforation disturbs the original shear layer and redistributes the vortex structure of the flow field. The instantaneous fluctuating flow field of the first 50 % and the last 50 % of the energy content after POD mode decomposition is reconstructed to study the effect of perforation on on large and small scale structures in the flow field. It is found that the impact of perforation on small-scale structures is greater than that on large-scale structures.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"161 ","pages":"Article 111358"},"PeriodicalIF":2.8,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142699783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The oscillation of a falling ferrofluid droplet induced by a nonuniform magnetic field","authors":"Guiye Wen ,&nbsp;Yongqing He ,&nbsp;Feng Jiao","doi":"10.1016/j.expthermflusci.2024.111351","DOIUrl":"10.1016/j.expthermflusci.2024.111351","url":null,"abstract":"<div><div>Understanding the droplet size and shape control mechanism in a magnetic field is critical for precisely manipulating ferrofluid droplets. Here, we conducted an experimental investigation on the dynamic behavior of a falling ferrofluid droplet under a nonuniform magnetic field produced by current coils. We observed an interesting phenomenon: the uneven distribution of the magnetic field and the jump in magnetic properties at fluid interfaces will cause the Laplace pressure difference on the droplet surface, stimulating the droplet’s oscillation. We also use the Laplace pressure difference equation and the interfacial tension coefficient correlation to model the deformation of ferrofluid droplets and determine the oscillation frequencies and deflection angles. The droplets’ oscillation frequency is related to the magnetic Bond number: <em>f</em>∼<span><math><mrow><msubsup><mrow><mi>Bo</mi></mrow><mrow><mi>m</mi></mrow><mrow><mo>-</mo><mn>0.523</mn><mspace></mspace><mo>∼</mo><mo>-</mo><mn>0.501</mn></mrow></msubsup></mrow></math></span>. The deflection angle of the droplet is further diminished by the superposition of a viscous shear moment and a magnetic moment (7.41^°∼12.90^°). Our research lays the groundwork for precise ferrofluid droplet manipulation in drug delivery and soft robots.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"161 ","pages":"Article 111351"},"PeriodicalIF":2.8,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lagrangian analysis of fluid transport in pulsatile post-stenotic flows","authors":"Xing Han,&nbsp;Kai Zhang","doi":"10.1016/j.expthermflusci.2024.111342","DOIUrl":"10.1016/j.expthermflusci.2024.111342","url":null,"abstract":"<div><div>A comprehensive experimental study was performed to characterize the fluid transportation processes in pulsatile post-stenotic flows. This study aims to understand the effect of pulsatility on the transportation dynamics of post-stenotic flows and to establish a non-dimensional number to quantify transportation effectiveness in these flows. Two-dimensional particle tracking velocimetry measurements were conducted in a close flow loop with a symmetric stenosis model. A pathline extension algorithm is then applied to the obtained Lagrangian data, such that fluid parcels are continuously tracked as they flow through the region of interest. Pulsatile flows at Reynolds numbers <span><math><msub><mi>Re</mi><mi>m</mi></msub><mo>=</mo><mn>1000</mn><mo>,</mo><mspace></mspace><mn>2000</mn><mo>,</mo><mspace></mspace><mn>4000</mn></math></span>, Strouhal number <span><math><mi>St</mi><mo>=</mo><mn>0.05</mn><mo>,</mo><mspace></mspace><mn>0.1</mn><mo>,</mo><mspace></mspace><mn>0.15</mn></math></span> and amplitude ratio <span><math><mrow><mi>λ</mi><mo>=</mo><mn>0.4</mn></mrow></math></span> and 0.8 are systematically investigated to understand the influence of pulsatility on the transport and mixing dynamics. The flow structures, such as the formation and evaluation of vortex rings, Kelvin-Helmoltz instabilities, jet meandering and breakdown, are clearly revealed by the lifespan parcel trajectories and the particle residence time (PRT). These structures are closely related to the transportation behaviours of the post-stenotic flows. Using the obtained Lagrangian results, the transportation effectiveness of the post-stenotic flows is further quantified by the depletion efficiency. The results demonstrate that while post-stenotic flows transport most residual fluids under a higher amplitude ratio, the depletion efficiency itself is insensitive to the amplitude ratio. The flow system operates more efficiently with high pulsatile frequencies (<span><math><mrow><mi>St</mi><mo>=</mo><mn>0.8</mn></mrow></math></span>). Additionally, a transportation effectiveness parameter, <span><math><mrow><mi>Te</mi></mrow></math></span>, is defined to evaluate the transport performance by comparing the transportation efficiency to the pressure drop. The <span><math><mrow><mi>Te</mi></mrow></math></span> value is optimized at a high pulsatile frequency (<span><math><mrow><mi>St</mi><mo>=</mo><mn>0.8</mn></mrow></math></span>) and a low amplitude ratio (<span><math><mrow><mi>λ</mi><mo>=</mo><mn>0.4</mn></mrow></math></span>), with <span><math><mrow><mi>Te</mi></mrow></math></span> being up to twice as high as its counterpart in the steady flow.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"161 ","pages":"Article 111342"},"PeriodicalIF":2.8,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of leaflet shape on the left ventricular blood flow pattern in BMHVs","authors":"Yan Qiang ,&nbsp;Zhixiong Li ,&nbsp;Minzu Zhang ,&nbsp;Tianci Duan ,&nbsp;Liang Qi ,&nbsp;Liejiang Wei ,&nbsp;Wenqi Zhong","doi":"10.1016/j.expthermflusci.2024.111343","DOIUrl":"10.1016/j.expthermflusci.2024.111343","url":null,"abstract":"<div><div>When a bileaflet mechanical heart valve is surgically implanted into the body, the downstream left ventricular blood flow pattern becomes complex, which is directly related to many postoperative complications. To investigate the hemodynamic properties associated with mechanical heart valve design, we built a left heart circulatory pulsatile flow generation system to simulate left ventricular flow and pressure under physiological conditions. We used time-resolved particle image velocimetry to study left ventricular blood flow downstream of two types of bileaflet mechanical heart valve: one with planar leaflets and one with cambered leaflets. Blood flow downstream of two different bileaflet mechanical valve shapes was assessed. The experimental results show that the bileaflet valve with a triple-jet pattern creates a three-dimensional vortex ring with a complex topology. In addition, the robust jet mode can introduce high shear stresses into the ventricular blood flow. Compared with the planar valve, the jet produced by the cambered valve has a more uniform velocity distribution, its vortex structure moves farther, and its shear stress distribution is more straightforward and continuous. Furthermore, the channel formed between the cambered valve vortex structure and the left ventricle wall surface is highly favorable for scouring the apical position and facilitating the transport of blood to the aortic orifice. Therefore, the shape of the leaflets of a bileaflet mechanical valve can significantly impact the left ventricular blood flow pattern and the blood transport process. Rational optimization of the design of the leaflet shape and improvement of the mechanical valve’s hemodynamic characteristics can reduce complications after valve replacement.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"161 ","pages":"Article 111343"},"PeriodicalIF":2.8,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Implementation of a high-frequency phosphor thermometry technique to study the heat transfer of a single droplet impingement","authors":"Victor A. Martinez,&nbsp;Alfonso Ortega","doi":"10.1016/j.expthermflusci.2024.111338","DOIUrl":"10.1016/j.expthermflusci.2024.111338","url":null,"abstract":"<div><div>Contributing to a better understanding of spray cooling systems, the heat transfer process underlying the event of a droplet impinging onto a uniformly heated stainless steel surface (SS304) was experimentally investigated. Since the heat transfer process is linked to the droplet’s hydrodynamics, high-speed videos were recorded to measure the deformation of the droplet. A series of isothermal and non-isothermal impacts were performed for Weber numbers (<span><math><mrow><mi>W</mi><mi>e</mi></mrow></math></span>) within the range <span><math><mrow><mn>17</mn><mo>.</mo><mn>7</mn><mo>≤</mo><mi>W</mi><mi>e</mi><mo>≤</mo><mn>58</mn><mo>.</mo><mn>2</mn></mrow></math></span>. A strong relationship between the maximum spreading ratio reached by the droplet and its initial kinetic energy was found. The surface temperature directly affects the droplet hydrodynamic during the impact by promoting an oscillatory behavior of the droplet after the maximum spreading is reached. Given the spatial–temporal resolution of the heat transfer process, a high-frequency phosphor thermometry technique was implemented, finding that the temperature drop upon droplet impact was independent of impact velocity. The sharp temperature drop results in an intense thermal interaction that occurred during the first 10 ms of the impact. The maximum average heat flux registered was 98.56 <span><math><mrow><mi>W</mi><mo>/</mo><mi>c</mi><msup><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math></span> with a cooling effectiveness of 3.5%.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"161 ","pages":"Article 111338"},"PeriodicalIF":2.8,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of sub-atmospheric pressure on appearance and pollutant formation of inverse diffusion flame within a confined space","authors":"Jingkun Zhang ,&nbsp;Yongbo Du ,&nbsp;Qiong Xu ,&nbsp;Yaodong Da ,&nbsp;Siyu Zong ,&nbsp;Lei Deng ,&nbsp;Defu Che","doi":"10.1016/j.expthermflusci.2024.111340","DOIUrl":"10.1016/j.expthermflusci.2024.111340","url":null,"abstract":"<div><div>Gas-fired boilers operating at high-altitude regions often suffer from inadequate output, decreased thermal efficiency, and excessive NO<em>_x</em> emissions. The effect of sub-atmospheric pressure on flame appearance and pollutant formation is the main reason for those problems, and thus needs to be clarified particularly under furnace combustion conditions with a fixed excess air coefficient. Inverse diffusion is a widely employed fuel–air configuration in burners of gas-fired boilers, and therefore the flame appearance, CO generation, and NO generation were experimentally investigated in this paper by adopting a low-pressure quartz tube reactor. Results show that the flame is elongated from reducing pressure under fuel-lean conditions, mainly due to the reduced oxygen mass concentration and the elevated jet velocity. Under fuel-rich combustion conditions, however, the flame is shorted at sub-atmospheric pressure from the suppressed soot formation. The reduced pressure leads to an increase in the global strain rate, making the flame more prone to uplift. With decreasing pressure, the increased air–fuel mixing and flame length facilitate the gas burnout, thus decreasing CO generation. The sub-atmospheric pressure could evidently reduce the NO generation under fuel-rich conditions, but slightly increase it under fuel-lean conditions. Under fuel-lean conditions, the NO major pathways (prompt, thermal, NNH, and N₂O) are promoted which leads to an increase in NO generation with decreasing pressure. Under fuel-rich conditions, however, NO formation is suppressed from the decreased rate of reaction <span><math><mrow><mtext>N2</mtext><mo>+</mo><mtext>CH</mtext><mo>↔</mo><mtext>HCN</mtext><mo>+</mo><mtext>N</mtext></mrow></math></span>.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"161 ","pages":"Article 111340"},"PeriodicalIF":2.8,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}