A regeneratively-cooled or dump-cooled nozzle is a critical component for expansion of hot gases to enable high temperature and performance in liquid rocket engines systems. Regeneratively-cooled ...channel wall nozzles are a design solution used across the propulsion industry as a simplified method to fabricate the nozzle structure with internal coolant passages. The scale and complexity of the channel wall nozzle (CWN) design can be challenging to fabricate which results in extended lead times and higher costs. Some of these challenges include: 1) Unique and high temperature materials, 2) Tight tolerances on large parts during manufacturing and assembly to contain high pressure propellants, 3) Thin-walled features to maintain adequate wall temperatures, and 4) Unique manufacturing process operations and complex tooling. The United States (U.S.) National Aeronautics and Space Administration (NASA) and U.S. specialty manufacturing vendors are maturing modern fabrication techniques to reduce complexity and decrease costs associated with channel wall nozzle manufacturing technology. Additive Manufacturing (AM) is one of the key technology advancements under evaluation for channel wall nozzles. Much of additive manufacturing for propulsion components has focused on laser powder bed fusion (L-PBF), but the scale is not yet feasible for application to large scale nozzles. NASA is evolving directed energy deposition (DED) techniques for nozzles including arc-based deposition, blown powder deposition, and Laser Wire Direct Closeout (LWDC). There are different approaches being considered for fabrication of the nozzle, and each of these DED processes offer unique process steps for rapid fabrication. The arc-based and blown powder deposition techniques are used for the forming of the CWN liner. A variety of materials are being demonstrated including Inconel 625, Haynes 230, JBK-75, and NASA HR-1. The blown powder DED process is also being demonstrated for forming an integral channel nozzle in a single operation in similar materials. The LWDC process is a method for closing out the channels within the liner and forming the structural jacket using a localized laser wire deposition technique. Identical materials mentioned above have been used for this process in addition to bimetallic closeout (C-18150–SS347, and C-18150–Inconel 625). NASA has completed process development, material characterization, and hot-fire testing on a variety of these channel wall nozzle fabrication technique. This publication presents an overview of the various channel wall nozzle manufacturing processes and materials under evaluation including results from the hot-fire testing. Future development and technology focus areas is also discussed relative to channel wall nozzle manufacturing.
•Large scale additive manufacturing for liquid rocket engine nozzles.•Laser Wire Direct Closeout technology for coolant channels.•Blown Powder Directed Energy Deposition for integral channel nozzles.•New additive materials for nozzles including JBK-75 and NASA HR-1.•Completed process development, material characterization, and hot-fire testing.
•Flash boiling fuel spray of twin-orifice nozzle is experimentally investigated.•Effects of superheat degree on in-nozzle bubble development are revealed.•The transformation in jet atomization under ...superheated conditions is studied.•Mechanisms of in-nozzle bubble flow and near-nozzle fuel spray are concluded.
To investigate the flash boiling fuel spray characteristics of the twin-orifice nozzle with aviation kerosene, a two-dimensional transparent slit nozzle is designed and studied under a wide range of superheated conditions. Both internal bubble development and near-nozzle jet atomization under subcooled and superheated conditions are studied via a high-speed camera with backlit measurement and image processing methods, accompanied with numerical simulation on in-nozzle two-phase flow for auxiliary analysis. The results indicate the expansion chamber of twin-orifice can increase the time for bubble nucleation and growth and enhance the bubble collision and aggregation. Also, under a higher superheat degree, the bubble volume fraction in the liquid-bubble interaction zone increases, and the bubbles exhausted from discharge-orifice can initiate from the interior to the edge of fuel jet at transitional flash boiling state. Furthermore, the bubble disruption occurs at the jet edge, which greatly enhances the atomization of fuel jet, leading to narrower liquid-core and wider spray distribution of near-nozzle fuel jet. In addition, the mechanisms of in-nozzle bubble development and near-nozzle spray atomization in the twin-orifice nozzle are concluded, which can be elucidated with more fundamental understanding of flash boiling fuel sprays.
In this study, a method for designing supersonic nozzles with axisymmetric plugs at high temperature has been proposed. The approach is based on the theory of Prandtl-Mayer expansion at high ...temperatures using the method of characteristics. For this purpose, a code in FORTRAN language was developed in order to obtain the nozzle design. Once the latter was obtained, we were interested in the evolution of the thermodynamic parameters of the flow such as pressure, temperature, and Mach number. The results achieved were confronted with those obtained for a perfect gas model. Regarding the design parameters (length, section ratio, thrust coefficient and mass coefficient), we found that the PG model gives very satisfactory results for values of and 0 below 2.00 and 1000 , respectively.
As and 0 increase, this affects performance, requiring the use of our HT model to correct the calculations. In order to minimize the weight of this nozzle, this research is investigating the truncation of the Plug nozzle to increase its performances. All calculations were performed for air.
Altitude-adapted nozzles are designed to facilitate flow adaptation during rocket ascent in the atmosphere, without requiring mechanical activation. As a consequence, the performance of the nozzle is ...significantly improved. The aim of this study is to develop a new profile of axisymmetric supersonic nozzles adapted at altitude (Dual Bell Nozzle with Central Body), which is characterized by an E-D nozzle as a basic profile. The performances obtained for this nozzle (E-D Nozzle) are then
compared to those of a Plug nozzle. The E-D nozzle shows significant performance advantages over the Plug nozzle, including a 13.02% increase in thrust, knowing that the length of the E-D nozzle is half
that of the Plug nozzle under the same design conditions. Finally, viscous calculations using the k-ω SST turbulence model were conducted to compare the performance of the dual bell nozzle with central body (DBNCB) and the E-D nozzle with the same cross-sectional ratio, and to assess the impact of nozzle pressure ratio (NPR) variations on the operation mode of the DBNCB. The results obtained show that the DBNCB offers the best performance in most phases of flight.
Two novel supersonic nozzles – Tip Ring Supersonic Nozzle and Elliptic Sharp Tipped Shallow (ESTS) Lobed Nozzle have been developed to enhance mixing at high speeds which is beneficial to supersonic ...ejectors. A circular ring protruding at the exit of a conical nozzle forms the tip ring nozzle. The innovative ESTS lobed nozzle comprising of four elliptic lobes with sharp tips that do not protrude deep into the core supersonic flow is produced by a novel yet simple methodology. A comparative experimental study is conducted between a conical nozzle, an ESTS lobed nozzle and a tip ring nozzle with exit Mach number of 2.3. For the first time, the three dimensional flow structure from ESTS lobed nozzle and tip ring nozzle is revealed from laser scattering flow visualization experiments on the free jet. A doubling of jet spreading rate is observed in the ESTS lobed nozzle. When applied to a supersonic ejector, both nozzles achieve a 30% increase in entrainment of secondary flow. The loss of compression ratio is 15% for the ESTS lobed nozzle while it is 50% for the tip ring nozzle. Further, the behavior of wall static pressure profile corroborates mixing enhancement.
•Two novel supersonic nozzles are developed for higher mixing with minimal losses.•ESTS lobed nozzle has an easily producible, exotic elliptic lobed geometry.•Tip ring nozzle uses a ring at the exit of the nozzle.•Three dimensional flow structure is explained by flow visualizations of the free jet.•Testing in a supersonic ejector, the nozzles enhance entertainment and mixing by 30%.
•Research methodology of rapid expansion of moist air in nozzles is proposed.•Analytical, numerical and experimental investigations of water vapour condensation.•A developed numerical tool in the ...form of a numerical code solving RANS equations.•In-house experimental facility for testing transonic flows is presented.•Good agreement was achieved between theoretical, CFD and experimental results.
Atmospheric air always contains a certain amount of water vapour being an element of the Earth's hydrological cycle. This content, which can be defined by relative humidity for example, has a significant impact on the transonic flow field. What happens then is the water vapour rapid condensation, due to a non-equilibrium process of spontaneous condensation, followed by evaporation of the resulting liquid phase on shock waves arising in a transonic flow. These two phenomena, related to the moist air flow and the heat transfer between the gaseous and the liquid phase on the condensation wave and on the shock wave, are analysed numerically and experimentally. The analyses were conducted using in-house numerical methods and an in-house experimental facility for testing transonic flows. The investigations focused mainly on geometries of convergent-divergent nozzles, which best represent transonic, i.e. subsonic and supersonic, flows.
•Static pressure profiles of vortex flashing R134a flow have been measured.•A 1D model for the estimation of nozzle flow vapor qualities was developed.•Inlet vortex increases the pressure drop across ...the nozzle divergent part.•Inlet vortex increases the vapor generation in the nozzle divergent part.•Inlet vortex can increase the nozzle isentropic efficiency.
Vortex control is a novel two-phase convergent–divergent nozzle restrictiveness control mechanism which achieves flow control by adjustable nozzle inlet vortex strength. It can potentially provide flow control with less sacrifice of nozzle efficiency, which is important for two-phase ejector cooling cycle performance. It is also less vulnerable to clogging. However, the underlying mechanism behind vortex control is still unclear. In this study, static pressure profiles of vortex flashing R134a flow expanded through nozzles under various conditions have been measured. A 1D model for the estimation of vapor qualities in the initially subcooled flashing nozzle flow based on the measurement results was also developed. It was found that after the introduction of inlet vortex to the initially subcooled flashing nozzle flow, the pressure drop across the divergent part has been increased, which is caused by the increased vapor generation in the divergent part. The elevated nozzle throat pressure results in the nozzle behaving like being more restrictive. When the inlet vortex is applied to flashing nozzle flow with two-phase at the nozzle inlet or single-phase liquid nozzle flow, the influence of inlet vortex on the nozzle restrictiveness and the nozzle pressure profile is insignificant. The nozzle isentropic efficiency can be significantly increased by applying inlet vortex, which could be beneficial to ejector performance when the vortex nozzle is used in ejectors. In order to achieve satisfactory vortex control range and high nozzle isentropic efficiency, the vortex nozzle divergent part length as well as the divergent angle need to be appropriately sized.
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