Ejector Nozzle Research Articles

Optimized design of annular ejector primary nozzle based on orthogonal test method

Abstract Annular ejectors are widely used in aerospace and other applications, and their performance has a significant impact on the overall system. In this paper, the effects of main nozzle area ratio, contraction section angle and diffusion section angle on the performance of annular ejector are investigated by using computational fluid dynamics combined with one-factor experiments, on the basis of which the L9(33) orthogonal table is established to optimise the structure of main nozzle and to screen the main influencing factors. The results show that the flow field inside the annular ejector is extremely complex. The influence of the main nozzle area ratio on the performance of the annular ejector is very great, and the change of the area ratio will lead to the change of the position of the second excitation sequence as well as the Mach number at the outlet of the main nozzle. However, as with the results of the one-way analysis, the effect of the angle of the constriction section on the exit Mach number is negligible.

Study on the key parameters of ice particle air jet ejector structure

Existing ice particle jet surface treatment technology is prone to ice particle adhesion during application, significantly affecting surface treatment efficiency. Based on the basic structure of the jet pump, the ice particle air jet surface treatment technology is proposed for the instant preparation and utilization of ice particles, solving the problem of ice particle adhesion and clogging. To achieve efficient utilization of ice particles and high-speed jetting, an integrated jet structure for ice particle ejection and acceleration was developed. The influence of the working nozzle position (Ld), expansion ratio (n), and acceleration nozzle diameter ratio (Dn) length-to-diameter ratio (Ln) on the ice particle ejection and acceleration was systematically studied. The structural parameters of the ejector were determined using the impact kinetic energy of ice particles as the comprehensive evaluation index, and the surface treatment test was conducted to verify the results. The study shows that under 2 MPa air pressure, the ejector nozzle parameters of n = 1.5, Dn = 4.0, Ld = 4, and Ln = 0 mm can effectively eject and accelerate the ice particles. The aluminum alloy plate depainting test obtained a larger paint removal radius and resulted in a smoother aluminum alloy plate surface, reducing the surface roughness from 3.194 ± 0.489 μm to 1.156 ± 0.136 μm. The immediate preparation and utilization of ice particles solved the problems of adhesion and storage in the engineering application of ice particle air jet technology, providing a feasible technical method in the field of material surface treatment.

Calibration and validation of a modified non-equilibrium boiling model for transcritical flashing flow in two-phase R744 nozzles

A modified homogeneous non-equilibrium boiling approach (HNB) was proposed for high-fidelity modelling of the trans-critical flashing process in two-phase R744 ejector nozzles. In the modified approach, the method of determining the metastable liquid saturation pressure was improved by integrating the metastable liquid enthalpy. Experimental tests were conducted on two different nozzles to calibrate the lumped accommodation coefficient in the modified HNB. The calibration dataset consisted of 30 trans-critical test points, with the motive inlet pressure ranging from 7.5 MPa to 11.5 MPa and temperature varying from 21 °C to 45 °C. It was demonstrated that the boiling coefficient was strongly related to nozzle inlet pressure and specific enthalpy. The coefficient was therefore fitted as a function of the operating condition. The modified HNB with the fitted function was then validated against another set of test data composed of 29 test points. The results demonstrated that the relative errors of the nozzle mass-flow rates were within 3 %. Finally, the modified HNB with the improved metastable liquid saturation pressure was compared and discussed with the existing HNB approach in the literature.

Three-dimensional characteristics of aerodynamic shockwave and condensation shockwave in steam ejectors

Characteristics of aerodynamic and condensation shockwaves are not clear in steam ejectors as the three-dimensional and non-equilibrium condensation effects in many simulation research are ignored. In the article, a non-equilibrium condensation model was developed to study the three-dimensional shockwave characteristics of steam ejectors. The formation, physical form, occurrence condition, location, quantity, intensity, and asymmetry of aerodynamic and condensation shockwave in different regions of three-dimensional steam ejectors were illustrated from mechanism. The coupling effect and interaction mechanism of aerodynamic and condensation shockwave were investigated. The influences of aerodynamic and condensation shockwaves on the flow field were analyzed. The similarities and differences between aerodynamic and condensation shockwaves were clarified. Results show that non-equilibrium condensation induces the condensation shockwave, but the condensation shockwave inhibits the non-equilibrium condensation. There is mutual inhibition between condensation shock and aerodynamic shock. A condensation shockwave appears downstream of the steam ejector's nozzle throat and another condensation shockwave may appear in the mixing chamber. The condition of the condensation shockwave in the mixing chamber is that the supercooling degree and the supersaturation ratio after the expansion wave exceed their critical values. In the critical condition, the supercooling degree is 19.6 K when the condensation shockwave appears in the mixing chamber.

Advanced Cascaded Recompression Absorption System Equipped with Ejector and Vapor-Injection Enhanced Vapor Compression Refrigeration System: ANN based Multi-Objective Optimization

Although traditional compression absorption refrigeration cycle (CARC) addresses the respective limitations of the Absorption Refrigeration Cycle (ARC) and Vapor Compression Refrigeration (VCR) systems while harnessing their individual strengths. But this arrangement faces challenges related to power wastage, insufficient thermal energy absorption, and high compressor power requirements. To address these issues, in this study, an advanced RAC (Recompression Absorption System) is integrated with enhanced VCR incorporated with ejector to develop advanced proposed Ejector-Compression Recompression Absorption cycle (E-CRAC) and Ejector enhanced Vapor-Injection Compression Recompression Absorption Cycle (EI-CRAC). A computational model is developed in the Engineering Equation Solver (EES) employing energy, mass, and exergy conservation principles to conduct a thorough 1st and 2nd law analysis. An Artificial Neural Network (ANN) model, combined with a Genetic algorithm, enabled multi-objective optimization to pinpoint optimal operational conditions. The COP of the proposed systems is nearly three times higher than the traditional CARC system, showing an improved efficiency in cooling operations. Additionally, EI-CRAC and E-CRAC demonstrate near 10% and 20% COP enhancement, as well as 15% and 25% increase of Exergy efficiency over benchmark basic CRAC respectively. Furthermore, the research highlights the sensitivity of these systems to various operating conditions, such as pressure drop across ejector nozzle, evaporator temperature, condenser pressure, absorber temperature etc., emphasizing the need for precise control to maximize efficiency. The results of this detailed theoretical thermodynamic analysis with optimization provide a comprehensive understanding of the proposed systems while offering valuable insights for further scope of improvements.

Optimal Design of Ejector Nozzle Profile with Internal and External Integrated Flow

Based on the orthogonal experimental method, a simulation case of the flow field of the ejector nozzle was designed to investigate the influence of the structural parameters of the ejector nozzle on the internal and external flow. This study explored the effects of throat area, outlet area, throat position, and ejector nozzle length on the ejector flow rate ratio, thrust coefficient, and net thrust coefficient. Subsequently, flow path geometry optimization was conducted to maximize the thrust coefficient or net thrust coefficient. The results revealed that the throat area ratio and the outlet area of the ejector nozzle are the primary factors affecting the aerodynamic performance. Compared to the baseline ejector nozzle model, the optimal model for thrust coefficient exhibited a 16.333% improvement, while the optimal model for net thrust coefficient demonstrated a significant enhancement of 46.674%.

Optimized design of steam ejector primary nozzle based on orthogonal test method

This paper proposes an orthogonal test method to optimize the design parameters of a steam ejector. The objective of this method is to improve the cooling system’s efficiency and effectiveness. The L9(33) orthogonal table was established to simultaneously optimize the shape curve of the converging portion of the primary nozzle, the length of the throat, and the angle of the diverging portion, and the entrainment rate and the critical backpressure were used as the performance indexes to formulate 9 groups of test schemes with a total of 108 cases, which were simulated under the same conditions. Based on Computational Fluid Dynamics (CFD) technology, the influence order of the three parameters is derived by polar analysis and the flow field is analyzed at the overall as well as the primary nozzle. The results show that the shape curve of converging portion of the primary nozzle is a sensitive factor affecting the performance of the ejector, which should be emphasized in practical production applications; the Mach number shapes at the primary nozzles of different structures show similarity and overlap at a distance of about 0.03 m from the mixing chamber. The Mach number profiles at different back pressures show want similarity.

Flow characteristics of ejector nozzles with different auxiliary intake valves

The ejector nozzle requires a third auxiliary airflow to improve its thrust performance at transonic speed. However, different auxiliary air intake structures will affect the third auxiliary flow, which in turn may change its thrust performance and internal flow field characteristics. Herein, we simulated four nozzles with different intake valve structures (sector angles of the open-close interval structure were 30°, 22.5°, 18°, and 15°, respectively) at transonic speed (Ma = 1.2). The results show that there is significant lateral flow inside the nozzle, which induces a multi-pair vortex. In addition, the nozzle with an open-close sector angle of 30° has the largest flow rate of 9.352 kg/s, which produces the largest thrust and the slowest dissipating flow vortex, but the distortion of the flow field in nozzles is the most obvious. However, with the reduction of the sector angle of the open-close intake valves (i.e., 22.5°, 18°, and 15°), the flow rate and the thrust of the nozzle decrease. Meanwhile, the dissipation of the flow vortex is accelerated, resulting in a weakening of the flow field distortion.

Quasi One-Dimensional characteristic analysis of ejector nozzle for turbofan propulsion system

To investigate the impact of the ejector characteristics of the exhaust system on the overall performance of a turbofan engine, this paper presents a study on the overall performance of the turbofan engine equipped with an ejector nozzle, focusing on its characteristics. Firstly, the design of the ejector exhaust system is presented and its ejector characteristics are analyzed through two-dimensional computational fluid dynamics simulations. Subsequently, a one-dimensional theoretical analysis of the ejector is conducted, and the pump suction and ejector nozzle’s thrust characteristics are determined based on the analysis results. Furthermore, a two-dimensional interpolation method is proposed to calculate the ejector coefficient, which utilizes the ejector's pump suction characteristics. By applying the matching principle of the ejector coefficient, a component-level model of the turbofan engine with an ejector nozzle is established. Based on this model, a method for predicting the backward infrared radiation intensity of the ejector exhaust system is proposed to investigate the influence of the ejector nozzle characteristics on the overall engine performance and infrared signature. The results demonstrate that the installation of the ejector exhaust system leads to a slight decrease in the overall engine performance, in which the average decrease of thrust is about 1.5%, and the average increase in fuel consumption is about 0.5%.but significantly reduces the infrared stealth characteristics, the average reduction is about 20%, which has good infrared stealth effect.

A novel relaxation drift model for simulating liquid-vapor momentum non-equilibrium in two-phase ejectors

A novel relaxation drift model (RDM) was proposed to simulate the interphase momentum non-equilibrium (slip) inside two-phase work-recovery CO2 ejectors. The RDM was validated using the experimental data of 5 different ejectors under 15 trans-critical conditions in total. The proposed model was compared with the existing homogeneous model (HM) and algebraic slip model (ASM) through case studies. The effects of ejector mixer design and nozzle expansion state were also disclosed. The results showed that the prediction errors of ejector performance by the RDM were within 17 %, which was smaller than the maximum error of 23 % predicted by the HM and the ASM. The numerical results demonstrated that the liquid droplets had lower velocities than the vapor when the liquid-vapor mixture accelerated, but the droplets travelled faster than the vapor during deceleration of the mixture. It was also revealed that the velocity slip would affect the shock pattern at the diffuser inlet if the mixer was choked. The effects of slip, however, became insignificant when the mixer was designed too large. In addition, the RDM might overestimate the ejector performance if the motive nozzle was strongly under-expanded. This study facilitates understanding of interphase velocity slip in two-phase CO2 ejector flow.

Orthogonal analysis method for multi – Objective optimization of CO2 nozzle thermodynamic performance

In this study, the structural parameters of the converging diverging (CD) nozzle in a subcritical or supercritical CO2 cycle system were optimized by L16 (44) orthogonal design. The established model was used to analyse the effect of divergence length Ld, divergence angle θ, convergence angle α and throat diameter Dth on the nozzle thermodynamic performance, and further optimization of CD nozzle structural parameters was carried out using comprehensive evaluation coefficients and comprehensive scores. The results indicate that Ld is the primary factor, and while the effects of θ and Dth were inconsistent in different application scenarios, attention should be paid to the size parameters of the nozzle divergence part during design. For CD nozzles with supercritical inlet pressure, there is a linear relationship between Ld and exergy destruction, while for subcritical CD nozzles, the effect of Ld is reduced. For a CD nozzle used in subcritical or transcritical cycles, the outlet exergy and exergy efficiency of the modified nozzle could be increased by 16.4% and 16.2%. For supercritical nozzles used in the Brayton cycle, the optimized exergy destruction was relatively reduced by 37%. The mass flow rate of the nozzle before and after optimization was reduced, with a maximum decrease of 22.7%, which is beneficial for improving the entrainment ratio of the ejector. In addition, it was found that considering this in the modelling process would lead to conservative optimization results. These research results could provide a reference for the design of the CO2 nozzle or motive nozzle of ejector.

Optimization and performance investigation of confocal twin-nozzle ejector for PEMFC hydrogen supply and recirculation system under actual variable operating conditions

The actual operating boundary conditions under different Proton Exchange Membrane Fuel Cell (PEMFC) power outputs are considered to evaluate the performance of a confocal twin-nozzle ejector and optimize its geometric parameters through the experimentally verified 3D Computational Fluid Dynamics model. The effects of primary and outlet pressures, anode gas relative humidity (RH), and nitrogen mole fraction (XN2) on its recirculation ratio are investigated. Besides, two key geometric parameters, mixing chamber diameter Dm and length Lam, are optimized under variable operating conditions. The results show that the two-nozzle (TN) mode can operate over a wider range of outlet pressure variation than single-nozzle (SN) mode, and an optimum primary pressure exists for both two modes. Considering the overall performance of SN and TN modes over the entire investigated PEMFC power range, the optimal Dm and Lam are 5.50 and 22.00 mm, respectively. The recirculation ratio at the rated power of 84 kW is improved by 14.10% compared to the initial structure. The ejector's total recirculation capability is positively correlated with both RH and XN2, while the hydrogen recirculation capability is negatively correlated with them. The impact of RH on the recirculation ratio of confocal twin-nozzle ejector is consistent with that of the conventional nozzle ejector. This work may provide useful ways for designing novel-type nozzle ejectors to expand the narrow operating range of ejectors used for PEMFC hydrogen supply and recirculation systems.

Patterns of air mixture movement in the operating area for the annular ejector of pneumatic transportation system

Purpose. To establish the regularities of two-phase flow of “gas-solid particles” in the operating area of an annular ejector where the following processes take place: air mixture ejecting, compressed air outflow from the ejector nozzle, air mixture flows mixing in the transport pipeline. In the work, the velocity distribution is also examined for dispersed phase and air phase of air mixture during its loading and accelerating in the transport pipeline of the pneumatic transport system. Methodology. The research is based on the fundamental approaches of mass point dynamics, aerodynamics, the theory of jet flows and iteration methods of numerical solution of equations. Findings. The mechanics of the air mixture flow under the ejection and aerodynamic force in the operating area of an annular ejector and at the beginning of transport pipeline is analyzed using the method of iterations. The impact of air mixture flow in the operating area of an annular ejector on energy performance of the pneumatic transport system is evaluated. Originality. The originality is that, for the first time, the regularities describing two-phase “gas–solid particles” flow at the loading area of the pneumatic transport system with an annular ejector have been obtained. This made it possible to characterize the velocity distribution of the dispersed and air phases of the air mixture during their loading and aerodynamic acceleration in the transport pipeline. Also, an innovative approach to the effectiveness of the use of pipeline pneumatic transport is the assessment of the energy indicators of the use of ejector-type pneumatic transport equipment depending on the rate of compressed air outflow from the ejector. Practical value. The implementation of the results in the modernization of existing and in the creation of new pneumatic transport systems with an annular ejector makes it possible to increase the efficiency of their use in the technological processes of moving dispersed materials at mining and metallurgical enterprises and in other areas of technology.

EN Thermodynamic analysis of the ethylene reliquefaction system on LEG carriers when replacing throttle devices with ejectors

LEG carriers’ energy efficiency can be increased by improving the boil-off gas (BOG) reliquefaction installation processes in its components. In this study, it is proposed to replace the conventional reliquefaction process (CRP) of a LEG carrier “ANTIKITIRA” actual installation equipped throttle devices with an ejector reliquefaction process (ERP) having two-phase ejectors as expansion devices to increase the energy efficiency of the installation. Expansion devices EV2E and EV2R were replaced with two-phase ejectors in the proposed system. The ejector efficiencies are ensured by additional components (separators and the precooler in the bottoming stage of the cascade). Separators maintain a constant pressure at the compressor inlets, and the precooler reduces the load on the condenser-evaporator. An ejector model has been developed to analyze the proposed system. The design pressure at the ejector nozzle outlet is determined based on multivariate calculations. Energy and exergy analyses of ERP and CRP systems were carried out. According to the exergy analysis results, each component's influence on the energy efficiency of the CRP and ERP systems is estimated. The exergy losses in each ERP component are lower than the corresponding values in the CRP components. The exergy losses in the condenser and precooler of the CRP system are lower than in the ERP system. The total power consumption is the same in both cycles, and the cooling capacity of the ERP cycle has increased by 29.1 kW. Replacement of throttle devices led to a decrease in absolute exergy loss from 9.75 to 4.95 kW. The energy efficiency of the ERP cycle increased by 24%, and the exergy efficiency increased by 16%. The most significant exergy losses in both cycles are observed during compression in a two-stage cargo compressor of the bottoming stage of the cascade (29.0-34.1%). It is concluded that the proposed ERP cycle meets IMO requirements for vessel energy efficiency but requires additional capital investments

Conjugate Heat Transfer in Thermal Inkjet Printheads

The mass of individual droplets ejected from a thermal inkjet printhead increases with increasing local temperature near the ejector nozzles. The amount of ink deposited on the page and so the printed image density depends on the droplet mass. Thus, printhead temperature nonuniformity results in printed image density variations that can be unacceptable to the end users of the printed output. Such temperature variations arise from a combination of the ink fluid flow and the heat transfer in both the ink and the solid components in the printhead. Conjugate heat transfer (CHT) in thermal inkjet printheads is investigated here using validated numerical simulations. A typical thermal inkjet printhead is considered here for the first time, with cold ink drawn through the solid structural components by the ejector nozzle refill. The effect of the width of the feedhole above the printhead chip on the temperature field within the chip is analyzed. Validation of the simulation model required the derivation of novel analytical solutions for the relatively simple problems of fully developed forced convection in a differentially heated planar channel and conduction against convection in plug flow. The results from numerical simulations of these two problems are found to compare well with the newly derived analytical solutions. CHT in flow over a backward-facing step with a heated downstream wall was also simulated as part of the validation process, and good agreement was observed with earlier numerical studies. For the main part of the study, it was found that increasing the width of the feedhole reduces the gradients in temperature on the surface of the printhead chip, thus reducing temperature-related printing defects.

Micro Turbojet Engine Nozzle Ejector Impact on the Acoustic Emission, Thrust Force and Fuel Consumption Analysis

This paper explores the implementation of an ejector to a micro turbojet engine and analysis of the advantages in terms of acoustic and thrust/fuel consumption. Starting with the analytical equations and a series of numerical simulations, the optimal ejector geometry for maximum thrust was obtained. The ejector was manufactured and integrated with the Jet Cat P80 micro turbo engine for testing. The purpose of this article is to report on an improved geometry that results in no significant increase in the frontal area of the turbo engine, which could increase drag. The tests were completed using various functioning regimes, namely idle, cruise and maximum. For each of them, a comparative analysis between engine parameters with and without an ejector was performed. During the experiments, it was observed that, when the ejector was used, the thrust increased for each regime, and the specific consumption decreased for all regimes. The stability of the engine was tested in transient regimes by performing a sudden acceleration sequence, and one carried out the operating line and the modification of temperature values in front of the turbine for both configurations. For each regime, the acoustic noise was monitored at a few points that were different distances from the nozzle, and a decrease was identified when the ejector was used. The advantages of using the ejector on the Jet Cat P80 turbo jet engine are an increased thrust, a lower specific consumption and a reduced noise level, and at the same time, the integrity of the engine in stable operational states and transient operating regimes is not affected.

Energy and exergy analysis of a novel ejector-expansion refrigeration system based on condenser outlet split cycle

BackgroundIn this paper, the possibility of performance enhancement of a new Condenser Outlet Split (COS) cycle with the presence of two ejectors working in different temperatures is investigated. In order to enhance the cycle performance, an auxiliary ejector-expansion refrigeration cycle equipped with a separator and a secondary ejector has been employed, resulting in further performance improvement on both exergy and energy analyses on the different condenser and evaporator temperatures. MethodsThe thermodynamic equations of each component in the standard and proposed cycles have been solved in EES software. Significant FindingsThe auxiliary cycle boosted the pressure at the inlet of the secondary nozzle of the main ejector leads to a better performance of the proposed cycle. Through energy analysis, compressor work recovery increased by 12% and the coefficient of performance showed up to 14.1% enhancement. Through exergy analysis, our proposed cycle have been produced 6.8% reduction in exergy destruction compared to the standard cycle, and the total exergy performance of the given system can be increased from 8.2 to 14%.

Development of ejector nozzle for high-pressure cold spray application: a case study on copper coatings

Development of ejector nozzle for high-pressure cold spray application: a case study on copper coatings

A streamlining method for ejector nozzle profile optimization based on polynomial function

In this study, ejector performance was optimized by streamlining the primary nozzle profile using polynomial functions. Thirteen streamline nozzle profiles with different initial and exit expansion half-angles which determined by quadratic and cubic functions were established, and their performance are discussed. The results indicate that the nozzle profiles designed by cubic function have the best performance than quadratic function. To improve the effective working range, the ejector should have an initial expansion half-angle that is as small as possible and an exit expansion half-angle that is as large as possible. To enhance the entrainment ratio, the ejector should have a constant exit expansion half-angle and a minimum initial expansion half-angle of 1°. An excessive initial expansion half-angle caused a sealed Mach number contour inside the nozzle, which wasted energy to reduce the velocity and increase the static pressure, decreasing the working efficiency of the primary flow. In addition, the entrainment ratio significantly decreased with a large exit expansion half-angle (greater than 17°).

Optimization of the primary nozzle for design a high entrainment ejector in spacesuit portable life support system

In looking forward to the future of human space exploration, it is increasingly stringent for the ventilation circuit subsystem in terms of reliability, simplicity and energy-efficient. Considering this requirement, the ejector, with the advantages of miniature size, no parasitic energy consumption and high reliability, is considered an appropriate alternative to the ventilation fan because it simultaneously implements the functions of mixing, entraining, and lifting pressure. This paper proposed a high entrainment ejector for application in spacesuit portable life support systems. The optimizations of the ejector nozzle geometrical parameters and nozzle exit position (NXP) were performed using a validated three-dimensional numerical model under various operating conditions. The results show that the NXP has a more significant effect on entrainment performance than other geometrical parameters in spacesuit portable life support systems, and the optimum NXP are not impacted by changes of the primary flow pressure and mixing chamber diameter, which similarly obtained the optimal entrainment ratio at the nozzle exit position of 2 mm. The maximum increments of entrainment ratio with the NXP varying from −4 mm to 8 mm are 0.2945 and 0.7664 under different primary flow pressures and mixing chamber diameters, respectively. Compared with the nozzle exit position, the most effects of nozzle converging angle and length on entrainment ratio are just 0.0864 and 0.0445. The optimum ejector extends the oxygen service duration by 12 min compared to the original one for the same volume of an oxygen tank, which is vital for the astronauts to conduct extravehicular activities in outer space.