An Experimental Comparative Performance Study of Variable Area Ejectors in Different Operating Conditions

An Experimental Comparative Performance Study of Variable Area Ejectors in Different Operating Conditions | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article An Experimental Comparative Performance Study of Variable Area Ejectors in Different Operating Conditions Virendra Kumar, P M V Subbarao This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3910442/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This research experimentally compares the performance of two variable area ejectors designed based on the Constant Rate of Momentum Change (CRMC) approach and the Constant Rate of Kinetic Energy Change (CRKEC) approach. Ejector systems were designed for specific design and operating conditions to perform experiments. The pressure recovery ratio (PRR) and entrainment ratio (ω) at on-design operating conditions were compared using the experimental results. The study also optimized the entrainment ratio of both systems at off-design conditions. The results indicate that both variable-area ejectors based on CRMC and CRKEC have their own advantages and limitations in terms of performance and suitability for specific applications. CRMC ejectors provide higher entrainment ratios (0.512) and lower pressure recovery ratios (0.178), while CRKEC ejectors provide slightly higher pressure recovery ratios (0.18) and lower entrainment ratios (0.5) at on-design conditions. Furthermore, the study investigated the off-design impact of nozzle exit positions (NXPs) and the pressure of motive and secondary flows on the entrainment ratio of both ejectors. ejector CRMC CRKEC entrainment ratio pressure recovery ratio Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 1. Introduction Ejectors are fluid-handling devices that use the momentum of a high-pressure fluid (issuing from a nozzle) to entrain a low-pressure fluid, thereby increasing the mass flow rate and decreasing the pressure in the system. Ejectors have significant importance in various industrial applications such as refrigeration [ 1 , 2 ], chemical processing [ 3 , 4 ], air conditioning [ 5 , 6 ], and propulsion systems [ 7 , 8 ], to name a few. The benefits of ejectors include their simple design, low cost, and ability to handle fluids with high viscosity, high solids content, and high temperatures [ 9 ]. However, ejectors also have limitations, such as low and high noise levels [ 10 ]. The primary causes of the ejector's significant losses are frictional losses, flow mixing (both primary and secondary), and normal shock. The primary causes of the ejector's significant losses are frictional losses, flow mixing (both primary and secondary), and the typical shock [ 11 , 12 ]. These losses can be mitigated by using physics-based design approaches. The design of supersonic ejectors is generally based on either the empirical [ 13 ] or the physics-based approach [ 14 ]. The empirical approach involves using empirical formulas and correlations to design and assess the ejector’s performance of the ejector. The physics-based approach involves governing equations to model and simulate the performance. The physics-based approach is considered more accurate and reliable than the empirical one. However, it is also more complex and time-consuming. The increased interest in physics-based ejector design techniques in recent years, which simulate the fluid dynamics and heat transfer properties of ejectors using computational fluid dynamics (CFD) simulations [ 15 – 17 ]. A better comprehension of the underlying physics is made possible by physics-based ejector design techniques like CRMC and CRKEC, making it possible to optimise ejector performance across various operating conditions [ 18 , 19 ]. These approaches eliminate thermodynamic shock from the conventionally designed ejector system by varying geometrical profiles. Entrainment is a crucial ejector performance characteristic that is affected by a number of design and operational factors, including the operating temperature [ 20 – 22 ], pressure[ 23 , 24 ], nozzle geometry [ 25 , 26 ] and its exit position [ 27 – 29 ], mixing chamber geometry [ 30 – 33 ], and operating fluids [ 34 ]. The ratio of the entrained mass flow rate of secondary fluid to the motive mass flow rate of primary fluid is known as the entrainment ratio [ 35 ]. The entrainment ratio can be optimized by varying the operating and design parameters[ 12 , 36 , 37 ]. The geometrical parameters of supersonic ejectors have a significant impact on their performance. These parameters include the nozzle area ratio [ 38 ], the mixing area ratio [ 39 ], and the length-to-diameter ratio [ 40 – 42 ]. A greater mass flow rate is produced by a larger nozzle area ratio[ 43 ]. The ratio of the mixing area to the neck area is known as the mixing area ratio. A greater pressure ratio is the outcome of a larger mixing area ratio. The ejector's length-to-diameter ratio is equal to its length divided by its diameter. A higher length-to-diameter ratio results in a higher pressure ratio. The geometric parameters, particularly the suction part height, mixing and diffuser section diameters, might affect the ejector's performance. Research by Zhang J. et al. in 2023 [ 44 ] has shown that ejector performance may be greatly enhanced by expanding the mixing part diameter. The effect of the nozzle's four geometric parameters—throat diameter, divergent angle, convergent angle, and length—on the entrainment performance was examined in research carried out by Feng et al. in 2020 [ 45 ]. According to the findings, the divergent zone's length and angle significantly influenced the entrainment performance. Under low power conditions, a reduced entrainment performance can be caused by a larger divergent angle, which results in over-expansion. It is advised to employ a supersonic ejector with an appropriate divergence angle and length for proton exchange membrane fuel cell (PEMFC) systems when there are significant entrainment requirements or steady operating circumstances. In contrast, for PEMFC systems with a broad range of operating power, it is recommended to use a primary nozzle that is convergent in shape. Current ejector design approaches, such as the CRMC and CRKEC with frictional effects individually, have been developed to address the limitations of conventional design approaches[ 18 , 19 ] for given design conditions. These design approaches have significantly decreased the geometrical sensitivity of the ejector and have improved the performance in comparison with “constant pressure mixing” and “constant area mixing ejectors”[ 46 , 47 ]. But, their suitability for specific applications, there is a need to compare the performance of physics-based ejector design approaches such as CRMC and CRKEC ejectors. A comparative study of these ejectors can provide insight into their advantages and limitations and help identify suitable design approaches for specific purposes/applications. Therefore, this study aims to experimentally investigate the performance of CRMC and CRKEC ejectors and to compare their performance at on-design and off-design conditions. 2. Experimental Test rig and experimentation The profile of the ejector's components, namely the nozzle and mixing-diffuser section, were computed based on CRMC[ 19 ] and CRKEC[ 18 ] approaches. The design conditions for the computation of the ejector's internal profile are mentioned below. The computed profile of the nozzle and mixing-diffuser sections are shown in Fig. 1 . Design and operating parameters : The design and operating conditions of the primary flow nozzle were as follows: mass flow rate ( \(\dot{{m}_{p}}\) ) = 0.018 Kg/s, total pressure (P o,p ) = 5.7 × 10 5 Pa, and total temperature (T o,p ) = 306 K. At the inlet of the secondary, the total pressure (P o,s ) was 70000 Pa, total temperature (T o,s ) was 300 K, and flow velocity (Vs) was maintained at 50 m/s. The entrainment ratio (ω) was 0.53, and other parameters were individual gas constant (R) of 287 J/Kg K, wall roughness (K) of 1.5 × 10 − 6 m, and ratio of specific heat value (ϒ) of 1.4. The nozzle's exit position was considered at zero (on-design), and the working fluid used in this system was air. These parameters define the system's design and operating conditions, which are essential for its performance and functionality. Figure 2 displays the estimated internal profiles of the ejector's components made with “electro-discharge machining” in aluminium rods. The outer shape of the nozzle was tapered to provide enough space for secondary flow to induce in the suction chamber while moving downstream. In the mixing section, the inlet and exit flanges were made to assemble the suction chamber and diffuser section, respectively. Tapping holes were made at each 0.5 and 1cm respective sections to measure the pressure inside the mixing and diffuser sections, respectively. The nozzle and mixing-diffuser sections were assembled horizontally with the help of nuts and bolts. The 'o’ rings were used to provide airtight assembly joints. The schematic diagram and photograph of the ejector test rig assembly are shown in Figs. 3 and 4 , respectively, along with all the required measuring instruments. Before commissioning the experiment, the safety and air-tight assembly of the ejector system was ensured. The primary flow cylinder and secondary flow chamber pressure were maintained as per operating conditions at the on-design and off-design performance study. The measuring instrument readings were recorded after achieving the steady-state condition of the system. In the first experimentation phase, both CRMC and CRKEC ejectors entrainment (ω) and pressure recovery ratio (PRR) were calculated at on-design operating conditions. The off-design performances were calculated on different operating pressures in the second experimentation phase. 3. Result and Discussion In order to investigate the ejector system's performance under on-design circumstances, the nozzle exit position (NXP) was maintained at zero. Using rotameters, the entrainment ratio (ω) was calculated for a given primary flow mass flow rate,( \({\dot{m}}_{p}\) ), by measuring the secondary entrained mass flow rate ( \({\dot{m}}_{s}\) ). The entrainment was calculated using the following Eq. ( 1 ). The pressure recovery ratio (PRR) of the system was calculated using Eq. ( 2 ) for both ejectors by measuring exit pressure \(\left({P}_{e}\right)\) and secondary flow inlet pressure \(\left({P}_{s}\right)\) . $$\omega =\frac{{\dot{m}}_{s}}{{\dot{m}}_{p}}$$ 1 $$PRR=\frac{{P}_{e}-{P}_{s}}{{P}_{s}}$$ 2 The entrainment ratio and the pressure recovery ratio of both the ejector systems are shown in Fig. 5 . It is clear from the figure that the CRMC ejector has a higher entrainment ratio than the CRKEC ejector. However, the pressure recovery ratio (PRR) of the CRKEC ejector is higher than the CRMC ejector. The CRMC ejector outperforms in entrainment, drawing in the secondary fluid effectively. Conversely, the CRKEC ejector exhibits superior pressure recovery due to its optimized kinetic energy control. These results underline the trade-offs between entrainment and pressure recovery in ejector system design. The off-design performance study of the ejector is important for field-level use and is difficult to obtain using an analytical one-dimensional gas dynamic study. So, a comprehensive set of tests were carried out at off-design conditions to evaluate the performance of both ejectors. NXP is a measure of the distance between a nozzle exit and the mixing section inlet. In the downstream from the inlet plane of the mixing section, it is considered positive NXP, while moving upstream away from it is negative NXP. The zozzle exit locations were adjusted in stages of one centimetre upstream and downstream to investigate the impact on entrainment. All other operating parameters were kept constant as on-design for this measurement. Figure 6 illustrates that the CRMC ejector is more sensitive to NXP than the CRKEC ejector. The CRMC ejector records marginally higher entrainment at NXP = 1cm than its on-design entrainment. However, beyond this point, the entrainment ratio drastically decreases. On the other hand, the entrainment of CRKEC ejector remains almost constant between NXP − 1 cm to 1 cm, gradually decreasing beyond that range. Therefore, it can be concluded from this study that the overall ejector performance is good between the NXP − 1 cm and 1 cm range, regardless of the design approach. The reason for the variation in entrainment is due to the expansion of the jet in the entrainment area, which is a area between the nozzle exit and the entrance to the mixing region. This area is not directly modeled in the CRMC or CRKEC gas dynamic ejector design models, but the NXP controls the jet expansion region and the converging space for secondary flow entrainment. As the nozzle moves downstream, the expansion angle and space decrease. The compression effect increases, attracting more secondary flow, but the primary jet moves away from the suction port, decreasing the inducing phenomenon. Beyond NXP = 1cm, the entrainment ratio decreases. Initially, the entrainment ratio increases with + ve NXP but then decreases. To study the primary flow total pressure impact over entrainment other operational parameters were kept constant as on-design settings. The results, as shown in Fig. 7 , suggest that a rise in the primary flow total pressure causes the primary flow at the nozzle exit to gain mass and momentum. The entrainment process in the mixing region is accelerated by this increased motion. However, beyond the on-design operating primary flow total pressure (i.e., 5.7 bar), the entrainment in both ejectors begins to significantly decrease. In the secondary flow total pressure study all other operating parameters were kept constant as on-design conditions. The result, which is shown in Fig. 8 , indicate that as the total pressure of the secondary flow increases, the entrainment ratio of both ejectors also increases. However, the rate of increase gradually decreases beyond the on-design operating pressure (i.e., 0.7 bar). The study was conducted to determine the entrainment ratio of different NXPs and primary flow total pressures while keeping the secondary flow total pressures constant at 0.7 bar. The results in Fig. 9 indicate that the maximum possible entrainment for both ejectors occurs at their on-design condition. Increasing the primary flow total pressure beyond the on-design condition reduces the entrainment ratio at all NXPs. However, other than the on-design condition, the maximum entrainment ratio for different primary flow pressures may vary with NXPs. Figure 10 shows how the entrainment ratio varies with NXPs and secondary flow total pressures. To analyze this effect, the primary flow total pressure was kept constant at on-design conditions (5.7 bar). The results indicate that increasing the secondary flow total pressure increases the entrainment ratio for both ejectors, regardless of NXPs. However, the maximum entrainment for different secondary flow total pressures may differ depending on the NXPs. 4. Conclusions In conclusion, this research delved into the performance characteristics of two distinct ejector systems, CRMC and CRKEC, under on-design and off-design conditions. The key findings can be summarized as follows: The CRMC ejector design approach optimizes the geometry of the mixing chamber to maximize the entrainment ratio, while the CRKEC ejector design approach optimizes the kinetic energy control to maximize the pressure ratio. The study revealed the inherent trade-offs between entrainment and pressure recovery in ejector system design. The CRMC ejector displayed higher sensitivity to nozzle exit position changes (NXP) than the CRKEC ejector. Both ejectors performed robustly between NXP − 1 cm and 1 cm, with entrainment remaining relatively constant within this range. Primary flow total pressure increases initially accelerated entrainment but decreased beyond the on-design operating pressure. An increase in secondary flow total pressure led to augmented entrainment, but the rate of increase tapered off beyond the on-design pressure. Entrainment ratios decreased with deviations in primary flow total pressure from on-design conditions. In summary, this comprehensive study advances our understanding of ejector behaviour, shedding light on critical parameters affecting entrainment and offering valuable insights for designing and operating physics-based CRMC and CRKEC ejector systems in diverse engineering applications. These findings provide a solid foundation for optimizing ejector performance in practical scenarios and contribute to this field's broader body of knowledge. Declarations Ethical Approval: Not applicable Funding: There was no funding to carry out this research. Author Contribution Virendra Kumar: Conceptualization, Methodology, Investigation, Writing- Original draft preparation WritingP M V Subbarao: Supervision, Reviewing and Editing Acknowledgement: We acknowledge the invaluable support of the Indian Institute of Technology, Delhi, especially the Turbomachine Lab in the Mechanical Engineering Department, for facilitating this experimental study. 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Yadav, G. Singhal, Numerical assessment on the performance of variable area single- and two-stage ejectors: A comparative study, Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering. (2021). https://doi.org/10.1177/09544089211033129 . A. Petrovic, J. Svorcan, A. Pejcev, D. Radenkovic, A. Petrovic, Comparison of novel variable area convergent-divergent nozzle performances obtained by analytic, computational and experimental methods, Appl Math Model. (2018). https://doi.org/10.1016/j.apm.2018.01.016 . Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3910442","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":270663441,"identity":"9c226742-6e6e-4b2c-98c7-275eb7782285","order_by":0,"name":"Virendra Kumar","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA70lEQVRIiWNgGAWjYNACAwkGhgMMDMwMFUAOM3MDUVokIFrOgLQwEqOFgQGihbENxCagxeB487EPDAUWdXzXDh/8XDivNpq/HajlR8U23FrOHEueAXKY5O20ZOmZ247nzjjM2MDYc+Y2Ti2SM3KMwX4xuJ1jxsy77VhuA1AL0IV4tMx//xmqJf8bM++cY7nzCWnhl+BhhtnCxszbUJO7gaAWnjRjhgQDCcmZt9OMpXmOHcjdCNRyEJ9f2NgPP2b48KeOn+928sPPPDV1ufPOHz744EcFbi1gkIBgHgaTB/CrRwV1pCgeBaNgFIyCEQIASQFUcw82Fq8AAAAASUVORK5CYII=","orcid":"","institution":"Harcourt Butler Technical University","correspondingAuthor":true,"prefix":"","firstName":"Virendra","middleName":"","lastName":"Kumar","suffix":""},{"id":270663442,"identity":"e06b04f2-de12-458e-8ea6-82e7fa8e4fb4","order_by":1,"name":"P M V Subbarao","email":"","orcid":"","institution":"Indian Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"P","middleName":"M V","lastName":"Subbarao","suffix":""}],"badges":[],"createdAt":"2024-01-30 11:46:01","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3910442/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3910442/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":50640583,"identity":"48557c10-fb15-4270-9f16-9836c1ab05aa","added_by":"auto","created_at":"2024-02-05 05:25:32","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":19820,"visible":true,"origin":"","legend":"\u003cp\u003eProfile of ejector's component (a) nozzle and (b) mixing-diffuser.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-3910442/v1/685b9d0bb966812af6c292f6.png"},{"id":50640881,"identity":"b6f94b48-67ca-4d98-91ce-b5be985301b1","added_by":"auto","created_at":"2024-02-05 05:33:32","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":432922,"visible":true,"origin":"","legend":"\u003cp\u003ePhotographs of ejector’s components, (a) CRMC, and (b) CRKEC\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-3910442/v1/281c4fbc2588bb886f023df5.png"},{"id":50640584,"identity":"4de518a9-f63e-4687-aaab-46e5f14d01e9","added_by":"auto","created_at":"2024-02-05 05:25:32","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":97091,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of physics-based variable area ejector test rig\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-3910442/v1/f437722e80fce0622603350a.png"},{"id":50640884,"identity":"0d286519-4d1c-4ed8-b8b4-c9e3ea4e09df","added_by":"auto","created_at":"2024-02-05 05:33:32","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":700855,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental Test Rig Photograph[18]\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-3910442/v1/5735f68052baafa36732d161.png"},{"id":50640585,"identity":"8ba770de-7572-4c07-8a04-0af32c5ca0d4","added_by":"auto","created_at":"2024-02-05 05:25:32","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":15144,"visible":true,"origin":"","legend":"\u003cp\u003eOn-design performance; entrainment ratio (ω) and Pressure recovery ratio (PRR).\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-3910442/v1/887a13983261eecc18f1a519.png"},{"id":50640587,"identity":"0575f10d-5cba-4498-ab3b-ca400af0938f","added_by":"auto","created_at":"2024-02-05 05:25:32","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":22492,"visible":true,"origin":"","legend":"\u003cp\u003eVariation in entrainment ratio with nozzle exit position (NXP)\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-3910442/v1/69d29ae7db8381591e18dc3d.png"},{"id":50640967,"identity":"97b2c96a-ff79-4679-a3ea-eeb2662fe42f","added_by":"auto","created_at":"2024-02-05 05:41:32","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":23725,"visible":true,"origin":"","legend":"\u003cp\u003eVariation in entrainment ratio with primary flow total pressure.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-3910442/v1/447248bd9da35f1214929028.png"},{"id":50640883,"identity":"3b47ad52-493d-4186-9d7d-22b1740a722b","added_by":"auto","created_at":"2024-02-05 05:33:32","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":25245,"visible":true,"origin":"","legend":"\u003cp\u003eVariation in entrainment ratio with secondary flow total pressure.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-3910442/v1/be0c29fa12a11898f061f71c.png"},{"id":50640591,"identity":"51e7213b-7f7c-4e5f-ba40-7dad864bb1d2","added_by":"auto","created_at":"2024-02-05 05:25:32","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":47939,"visible":true,"origin":"","legend":"\u003cp\u003eVariation in entrainment ratio at different NXPs and primary flow total pressures\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-3910442/v1/146cac7e97a739c9d6a96422.png"},{"id":50640590,"identity":"11b80a11-7a05-403c-a622-3be98034f592","added_by":"auto","created_at":"2024-02-05 05:25:32","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":49614,"visible":true,"origin":"","legend":"\u003cp\u003eVariation in entrainment ratio at different NXPs and secondary flow total pressures\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-3910442/v1/729a921d0d73206c368acf47.png"},{"id":51168395,"identity":"0e036e07-d16c-445a-b5db-d9202adaafc3","added_by":"auto","created_at":"2024-02-15 10:09:08","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1541685,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3910442/v1/148d5896-1347-47ca-aeb9-96449819222e.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"An Experimental Comparative Performance Study of Variable Area Ejectors in Different Operating Conditions","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eEjectors are fluid-handling devices that use the momentum of a high-pressure fluid (issuing from a nozzle) to entrain a low-pressure fluid, thereby increasing the mass flow rate and decreasing the pressure in the system. Ejectors have significant importance in various industrial applications such as refrigeration [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], chemical processing [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], air conditioning [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], and propulsion systems [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], to name a few. The benefits of ejectors include their simple design, low cost, and ability to handle fluids with high viscosity, high solids content, and high temperatures [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. However, ejectors also have limitations, such as low and high noise levels [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe primary causes of the ejector's significant losses are frictional losses, flow mixing (both primary and secondary), and normal shock. The primary causes of the ejector's significant losses are frictional losses, flow mixing (both primary and secondary), and the typical shock [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. These losses can be mitigated by using physics-based design approaches. The design of supersonic ejectors is generally based on either the empirical [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] or the physics-based approach [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The empirical approach involves using empirical formulas and correlations to design and assess the ejector\u0026rsquo;s performance of the ejector. The physics-based approach involves governing equations to model and simulate the performance. The physics-based approach is considered more accurate and reliable than the empirical one. However, it is also more complex and time-consuming.\u003c/p\u003e \u003cp\u003eThe increased interest in physics-based ejector design techniques in recent years, which simulate the fluid dynamics and heat transfer properties of ejectors using computational fluid dynamics (CFD) simulations [\u003cspan additionalcitationids=\"CR16\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. A better comprehension of the underlying physics is made possible by physics-based ejector design techniques like CRMC and CRKEC, making it possible to optimise ejector performance across various operating conditions [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. These approaches eliminate thermodynamic shock from the conventionally designed ejector system by varying geometrical profiles.\u003c/p\u003e \u003cp\u003eEntrainment is a crucial ejector performance characteristic that is affected by a number of design and operational factors, including the operating temperature [\u003cspan additionalcitationids=\"CR21\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], pressure[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], nozzle geometry [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] and its exit position [\u003cspan additionalcitationids=\"CR28\" citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e], mixing chamber geometry [\u003cspan additionalcitationids=\"CR31 CR32\" citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], and operating fluids [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. The ratio of the entrained mass flow rate of secondary fluid to the motive mass flow rate of primary fluid is known as the entrainment ratio [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. The entrainment ratio can be optimized by varying the operating and design parameters[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe geometrical parameters of supersonic ejectors have a significant impact on their performance. These parameters include the nozzle area ratio [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e], the mixing area ratio [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e], and the length-to-diameter ratio [\u003cspan additionalcitationids=\"CR41\" citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. A greater mass flow rate is produced by a larger nozzle area ratio[\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. The ratio of the mixing area to the neck area is known as the mixing area ratio. A greater pressure ratio is the outcome of a larger mixing area ratio. The ejector's length-to-diameter ratio is equal to its length divided by its diameter. A higher length-to-diameter ratio results in a higher pressure ratio.\u003c/p\u003e \u003cp\u003eThe geometric parameters, particularly the suction part height, mixing and diffuser section diameters, might affect the ejector's performance. Research by Zhang J. et al. in 2023 [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e] has shown that ejector performance may be greatly enhanced by expanding the mixing part diameter. The effect of the nozzle's four geometric parameters\u0026mdash;throat diameter, divergent angle, convergent angle, and length\u0026mdash;on the entrainment performance was examined in research carried out by Feng et al. in 2020 [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. According to the findings, the divergent zone's length and angle significantly influenced the entrainment performance. Under low power conditions, a reduced entrainment performance can be caused by a larger divergent angle, which results in over-expansion. It is advised to employ a supersonic ejector with an appropriate divergence angle and length for proton exchange membrane fuel cell (PEMFC) systems when there are significant entrainment requirements or steady operating circumstances. In contrast, for PEMFC systems with a broad range of operating power, it is recommended to use a primary nozzle that is convergent in shape.\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eCurrent ejector design approaches, such as the CRMC and CRKEC with frictional effects individually, have been developed to address the limitations of conventional design approaches[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] for given design conditions. These design approaches have significantly decreased the geometrical sensitivity of the ejector and have improved the performance in comparison with \u0026ldquo;constant pressure mixing\u0026rdquo; and \u0026ldquo;constant area mixing ejectors\u0026rdquo;[\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e, \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. But, their suitability for specific applications, there is a need to compare the performance of physics-based ejector design approaches such as CRMC and CRKEC ejectors. A comparative study of these ejectors can provide insight into their advantages and limitations and help identify suitable design approaches for specific purposes/applications. Therefore, this study aims to experimentally investigate the performance of CRMC and CRKEC ejectors and to compare their performance at on-design and off-design conditions.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"2. Experimental Test rig and experimentation","content":"\u003cp\u003eThe profile of the ejector's components, namely the nozzle and mixing-diffuser section, were computed based on CRMC[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] and CRKEC[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] approaches. The design conditions for the computation of the ejector's internal profile are mentioned below. The computed profile of the nozzle and mixing-diffuser sections are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cem\u003eDesign and operating parameters\u003c/em\u003e: The design and operating conditions of the primary flow nozzle were as follows: mass flow rate (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\dot{{m}_{p}}\\)\u003c/span\u003e\u003c/span\u003e)\u0026thinsp;=\u0026thinsp;0.018 Kg/s, total pressure (P\u003csub\u003eo,p\u003c/sub\u003e)\u0026thinsp;=\u0026thinsp;5.7 \u0026times; 10\u003csup\u003e5\u003c/sup\u003e Pa, and total temperature (T\u003csub\u003eo,p\u003c/sub\u003e)\u0026thinsp;=\u0026thinsp;306 K. At the inlet of the secondary, the total pressure (P\u003csub\u003eo,s\u003c/sub\u003e) was 70000 Pa, total temperature (T\u003csub\u003eo,s\u003c/sub\u003e) was 300 K, and flow velocity (Vs) was maintained at 50 m/s. The entrainment ratio (ω) was 0.53, and other parameters were individual gas constant (R) of 287 J/Kg K, wall roughness (K) of 1.5 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e m, and ratio of specific heat value (ϒ) of 1.4. The nozzle's exit position was considered at zero (on-design), and the working fluid used in this system was air. These parameters define the system's design and operating conditions, which are essential for its performance and functionality.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e displays the estimated internal profiles of the ejector's components made with \u0026ldquo;electro-discharge machining\u0026rdquo; in aluminium rods. The outer shape of the nozzle was tapered to provide enough space for secondary flow to induce in the suction chamber while moving downstream. In the mixing section, the inlet and exit flanges were made to assemble the suction chamber and diffuser section, respectively. Tapping holes were made at each 0.5 and 1cm respective sections to measure the pressure inside the mixing and diffuser sections, respectively.\u003c/p\u003e \u003cp\u003eThe nozzle and mixing-diffuser sections were assembled horizontally with the help of nuts and bolts. The 'o\u0026rsquo; rings were used to provide airtight assembly joints. The schematic diagram and photograph of the ejector test rig assembly are shown in Figs.\u0026nbsp;3 and \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e, respectively, along with all the required measuring instruments.\u003c/p\u003e \u003cp\u003eBefore commissioning the experiment, the safety and air-tight assembly of the ejector system was ensured. The primary flow cylinder and secondary flow chamber pressure were maintained as per operating conditions at the on-design and off-design performance study. The measuring instrument readings were recorded after achieving the steady-state condition of the system.\u003c/p\u003e \u003cp\u003eIn the first experimentation phase, both CRMC and CRKEC ejectors entrainment (ω) and pressure recovery ratio (PRR) were calculated at on-design operating conditions. The off-design performances were calculated on different operating pressures in the second experimentation phase.\u003c/p\u003e"},{"header":"3. Result and Discussion","content":"\u003cp\u003eIn order to investigate the ejector system's performance under on-design circumstances, the nozzle exit position (NXP) was maintained at zero. Using rotameters, the entrainment ratio (ω) was calculated for a given primary flow mass flow rate,( \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\dot{m}}_{p}\\)\u003c/span\u003e\u003c/span\u003e), by measuring the secondary entrained mass flow rate (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\dot{m}}_{s}\\)\u003c/span\u003e\u003c/span\u003e). The entrainment was calculated using the following Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The pressure recovery ratio (PRR) of the system was calculated using Eq.\u0026nbsp;(\u003cspan refid=\"Equ2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) for both ejectors by measuring exit pressure \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\left({P}_{e}\\right)\\)\u003c/span\u003e\u003c/span\u003e and secondary flow inlet pressure \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\left({P}_{s}\\right)\\)\u003c/span\u003e\u003c/span\u003e.\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\omega =\\frac{{\\dot{m}}_{s}}{{\\dot{m}}_{p}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$PRR=\\frac{{P}_{e}-{P}_{s}}{{P}_{s}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe entrainment ratio and the pressure recovery ratio of both the ejector systems are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e. It is clear from the figure that the CRMC ejector has a higher entrainment ratio than the CRKEC ejector. However, the pressure recovery ratio (PRR) of the CRKEC ejector is higher than the CRMC ejector. The CRMC ejector outperforms in entrainment, drawing in the secondary fluid effectively. Conversely, the CRKEC ejector exhibits superior pressure recovery due to its optimized kinetic energy control. These results underline the trade-offs between entrainment and pressure recovery in ejector system design.\u003c/p\u003e \u003cp\u003eThe off-design performance study of the ejector is important for field-level use and is difficult to obtain using an analytical one-dimensional gas dynamic study. So, a comprehensive set of tests were carried out at off-design conditions to evaluate the performance of both ejectors.\u003c/p\u003e \u003cp\u003eNXP is a measure of the distance between a nozzle exit and the mixing section inlet. In the downstream from the inlet plane of the mixing section, it is considered positive NXP, while moving upstream away from it is negative NXP. The zozzle exit locations were adjusted in stages of one centimetre upstream and downstream to investigate the impact on entrainment. All other operating parameters were kept constant as on-design for this measurement.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e illustrates that the CRMC ejector is more sensitive to NXP than the CRKEC ejector. The CRMC ejector records marginally higher entrainment at NXP\u0026thinsp;=\u0026thinsp;1cm than its on-design entrainment. However, beyond this point, the entrainment ratio drastically decreases. On the other hand, the entrainment of CRKEC ejector remains almost constant between NXP \u0026minus;\u0026thinsp;1 cm to 1 cm, gradually decreasing beyond that range. Therefore, it can be concluded from this study that the overall ejector performance is good between the NXP \u0026minus;\u0026thinsp;1 cm and 1 cm range, regardless of the design approach. The reason for the variation in entrainment is due to the expansion of the jet in the entrainment area, which is a area between the nozzle exit and the entrance to the mixing region. This area is not directly modeled in the CRMC or CRKEC gas dynamic ejector design models, but the NXP controls the jet expansion region and the converging space for secondary flow entrainment. As the nozzle moves downstream, the expansion angle and space decrease. The compression effect increases, attracting more secondary flow, but the primary jet moves away from the suction port, decreasing the inducing phenomenon. Beyond NXP\u0026thinsp;=\u0026thinsp;1cm, the entrainment ratio decreases. Initially, the entrainment ratio increases with +\u0026thinsp;ve NXP but then decreases.\u003c/p\u003e \u003cp\u003eTo study the primary flow total pressure impact over entrainment other operational parameters were kept constant as on-design settings. The results, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e, suggest that a rise in the primary flow total pressure causes the primary flow at the nozzle exit to gain mass and momentum. The entrainment process in the mixing region is accelerated by this increased motion. However, beyond the on-design operating primary flow total pressure (i.e., 5.7 bar), the entrainment in both ejectors begins to significantly decrease.\u003c/p\u003e \u003cp\u003eIn the secondary flow total pressure study all other operating parameters were kept constant as on-design conditions. The result, which is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e, indicate that as the total pressure of the secondary flow increases, the entrainment ratio of both ejectors also increases. However, the rate of increase gradually decreases beyond the on-design operating pressure (i.e., 0.7 bar).\u003c/p\u003e\u003cp\u003eThe study was conducted to determine the entrainment ratio of different NXPs and primary flow total pressures while keeping the secondary flow total pressures constant at 0.7 bar. The results in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e9\u003c/span\u003e indicate that the maximum possible entrainment for both ejectors occurs at their on-design condition. Increasing the primary flow total pressure beyond the on-design condition reduces the entrainment ratio at all NXPs. However, other than the on-design condition, the maximum entrainment ratio for different primary flow pressures may vary with NXPs.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e10\u003c/span\u003e shows how the entrainment ratio varies with NXPs and secondary flow total pressures. To analyze this effect, the primary flow total pressure was kept constant at on-design conditions (5.7 bar). The results indicate that increasing the secondary flow total pressure increases the entrainment ratio for both ejectors, regardless of NXPs. However, the maximum entrainment for different secondary flow total pressures may differ depending on the NXPs.\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eIn conclusion, this research delved into the performance characteristics of two distinct ejector systems, CRMC and CRKEC, under on-design and off-design conditions. The key findings can be summarized as follows:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eThe CRMC ejector design approach optimizes the geometry of the mixing chamber to maximize the entrainment ratio, while the CRKEC ejector design approach optimizes the kinetic energy control to maximize the pressure ratio.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eThe study revealed the inherent trade-offs between entrainment and pressure recovery in ejector system design.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eThe CRMC ejector displayed higher sensitivity to nozzle exit position changes (NXP) than the CRKEC ejector.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eBoth ejectors performed robustly between NXP \u0026minus;\u0026thinsp;1 cm and 1 cm, with entrainment remaining relatively constant within this range.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ePrimary flow total pressure increases initially accelerated entrainment but decreased beyond the on-design operating pressure.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eAn increase in secondary flow total pressure led to augmented entrainment, but the rate of increase tapered off beyond the on-design pressure.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eEntrainment ratios decreased with deviations in primary flow total pressure from on-design conditions.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eIn summary, this comprehensive study advances our understanding of ejector behaviour, shedding light on critical parameters affecting entrainment and offering valuable insights for designing and operating physics-based CRMC and CRKEC ejector systems in diverse engineering applications. These findings provide a solid foundation for optimizing ejector performance in practical scenarios and contribute to this field's broader body of knowledge.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eEthical Approval:\u003c/h2\u003e \u003cp\u003eNot applicable\u003c/p\u003e\u003ch2\u003eFunding:\u003c/h2\u003e \u003cp\u003eThere was no funding to carry out this research.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eVirendra Kumar: Conceptualization, Methodology, Investigation, Writing- Original draft preparation WritingP M V Subbarao: Supervision, Reviewing and Editing\u003c/p\u003e\u003ch2\u003eAcknowledgement:\u003c/h2\u003e \u003cp\u003eWe acknowledge the invaluable support of the Indian Institute of Technology, Delhi, especially the Turbomachine Lab in the Mechanical Engineering Department, for facilitating this experimental study.\u003c/p\u003e \u003cp\u003e The authors declare that there is no conflict of interest regarding the publication of this article.\u003c/p\u003e\u003ch2\u003eAvailability of data and materials:\u003c/h2\u003e \u003cp\u003eUpon request, we will provide access to our research data.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eV. 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Pejcev, D. Radenkovic, A. Petrovic, Comparison of novel variable area convergent-divergent nozzle performances obtained by analytic, computational and experimental methods, Appl Math Model. (2018). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.apm.2018.01.016\u003c/span\u003e\u003cspan address=\"10.1016/j.apm.2018.01.016\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"ejector, CRMC, CRKEC, entrainment ratio, pressure recovery ratio","lastPublishedDoi":"10.21203/rs.3.rs-3910442/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3910442/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis research experimentally compares the performance of two variable area ejectors designed based on the Constant Rate of Momentum Change (CRMC) approach and the Constant Rate of Kinetic Energy Change (CRKEC) approach. Ejector systems were designed for specific design and operating conditions to perform experiments. The pressure recovery ratio (PRR) and entrainment ratio (ω) at on-design operating conditions were compared using the experimental results. The study also optimized the entrainment ratio of both systems at off-design conditions. The results indicate that both variable-area ejectors based on CRMC and CRKEC have their own advantages and limitations in terms of performance and suitability for specific applications. CRMC ejectors provide higher entrainment ratios (0.512) and lower pressure recovery ratios (0.178), while CRKEC ejectors provide slightly higher pressure recovery ratios (0.18) and lower entrainment ratios (0.5) at on-design conditions. Furthermore, the study investigated the off-design impact of nozzle exit positions (NXPs) and the pressure of motive and secondary flows on the entrainment ratio of both ejectors.\u003c/p\u003e","manuscriptTitle":"An Experimental Comparative Performance Study of Variable Area Ejectors in Different Operating Conditions","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-02-05 05:25:27","doi":"10.21203/rs.3.rs-3910442/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"244caf2d-9f59-42e5-af77-fb22e4f64c7d","owner":[],"postedDate":"February 5th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-02-15T10:08:47+00:00","versionOfRecord":[],"versionCreatedAt":"2024-02-05 05:25:27","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3910442","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3910442","identity":"rs-3910442","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}