Aerospike Nozzle Research Articles

Side-Force Amplification on an Aerodynamically Thrust-Vectored Aerospike Nozzle

Results from computational and coldow experiments on uidic thrust vectoring of a small-scale aerospike thruster are presented. Thrust vectoring is produced by injection of a secondary uid into the primary ow eld normal to the nozzle axis. The experimental aerospike nozzle was truncated at 57% of its full theoretical length. For these tests, carbon dioxide is the working uid. Injection points near the end of the truncated spike produced the highest force ampli cation factors. Explanations are given for this phenomenon. For secondary injection near the end of the aerospike, side force ampli cation factors up to 1.4 and side force speci c impulses up to 55 s were demonstrated. By comparison, the main ow speci c impulse averaged approximately 38s. Secondary side-injection pulses were observed to crisply reproduce side forces with a high degree of delity. Side force levels approach 2.7% of the total thrust level at maximum e ciency. Higher side forces of 4.7% axial thrust were also achieved at reduced e ciency. The side force ampli cation factors were independent of operating nozzle pressure ratio for the range of chamber pressures evaluated in this test series.

Computational and Experimental Simulations of the Flow Characteristics of an Aerospike Nozzle

Single Stage To Orbit (SSTO) missions which require its engines to be operated at varying back pressure conditions, use engines operate at high combustion chamber pressures (more than 100bar) with moderate area ratios (AR 70~80). This ensures that the exhaust jet flows full during most part of the operational regimes by optimal expansion at each altitude. Aero-spike nozzle is a kind of altitude adaptation nozzle where requirement of high combustion chamber pressures can be avoided as the flow is adapted to the outside conditions by the virtue of the nozzle configuration. However, the thrust prediction using the conventional thrust equations remains to be a challenge as the nozzle plume shapes vary with the back pressure conditions. In the present work, the performance evaluation of a new aero-spike nozzle is being carried out. Computational studies are carried out to predict the thrust generated by the aero-spike nozzle in varying back pressure conditions which requires the unsteady pressure boundary conditions in the computational domain. Schlieren pictures are taken to validate the computational results. It is found that the flow in the aero-spike nozzle is mainly affected by the base wall pressure variation. The aerospike nozzle exhibits maximum performance in the properly expanded flow regime due to the open wake formation.

811 数値解析を用いたエアロスパイクノズルの性能評価:圧力比の影響(0S.2 圧縮性流れの基礎と応用3)

811 数値解析を用いたエアロスパイクノズルの性能評価:圧力比の影響(0S.2 圧縮性流れの基礎と応用3)

The Influence of Different Turbulence Models on the FlowField Characteristics of an Aerospike Nozzle

To improve the calculation of the flow properties of an aerospike nozzle, different turbulent models are studied in this research. The primary shape of the nozzle and the plug is determined through utilizing an approximate method. The flow field is then simulated using Navier-Stokes equations for compressible flow. The computational methodology utilizes steady state density-based formulation and a finite volume cell centered scheme to discretize the flow field equations. To accelerate the solution convergence, the flow field is divided into several zones. Each zone is facilitated with proper unstructured grid and appropriate initial conditions are implemented to each zone. The accuracy and the robustness of wall function based turbulence models i.e. standard and RNG k-ε models are compared with those of Spalart-Allmaras (S-A) and k-ω turbulence models.

Parametric Study of Dual-Expander Aerospike Nozzle Upper-Stage Rocket Engine

TheAir Force Institute ofTechnology is studying anewupper-stage rocket engine architecture: the dual-expander aerospike nozzle. The goal of this research is to provide themaximum thrust-to-weight ratio in an engine that delivers aminimumof 50,000 lbf vacuum thrustwith a vacuumspecific impulse of 464 s. Previouswork focused ondeveloping an initial design to demonstrate the feasibility of the dual-expander aerospike nozzle architecture. That work culminated in adesign exceeding the requirements, delivering an estimated 57,000 lbf thrustwith a specific impulse of 472 s by using an oxidizer-to-fuel ratio of 7.03, a total mass flow of 121 lbm=s, and an engine length of 38 in. These results were computed in a numerical model of the engine. Current work expands the model in preparation for optimizing its thrust-to-weight ratio. The changes to the model are designed to support running automated parametric and optimization studies. Parametric studies varying oxidizer-to-fuel ratio, totalmassflow, and chamber length show that a dual-expander aerospike nozzle engine can achieve 50,000 lbf vacuum thrust and 489 s vacuum Isp with an oxidizer-to-fuel ratio of six, a total mass flow of 104 lbm=s (a reduction of 14%), and an engine length of 27.9 in. (a reduction of over 25%), which should equate to a significant weight savings over the original design.

Experimental research on the rotating detonation in gaseous fuels–oxygen mixtures

An experimental study on rotating detonation is presented in this paper. The study was focused on the possibility of using rotating detonation in a rocket engine. The research was divided into two parts: the first part was devoted to obtaining the initiation of rotating detonation in fuel–oxygen mixture; the second was aimed at determination of the range of propagation stability as a function of chamber pressure, composition, and geometry. Additionally, thrust and specific impulse were determined in the latter stage. In the paper, only rich mixture is described, because using such a composition in rocket combustion chambers maximizes the specific impulse and thrust. In the experiments, two kinds of geometry were examined: cylindrical and cylindrical-conic, the latter can be simulated by a simple aerospike nozzle. Methane, ethane, and propane were used as fuel. The pressure–time courses in the manifolds and in the chamber are presented. The thrust–time profile and detonation velocity calculated from measured pressure peaks are shown. To confirm the performance of a rocket engine with rotating detonation as a high energy gas generator, a model of a simple engine was designed, built, and tested. In the tests, the model of the engine was connected to the dump tank. This solution enables different environmental conditions from a range of flight from 16 km altitude to sea level to be simulated. The obtained specific impulse for pressure in the chamber of max. 1.2 bar and a small nozzle expansion ratio of about 3.5 was close to 1,500 m/s.

Performance Characteristics of an Annular ConicalAerospike Nozzle with Freestream Effect

An experimental investigation has been carried out to study the performance and base pressure characteristics of a Mach 2.0 annular conical aerospike nozzle with and without freestream flow. The effect of cowl length, plug length, and plug contour variation on the nozzle performance and base pressure characteristics is studied. It is observed that the overexpansion shock from the internal nozzle, overexpansion shock on the spike surface, and the expansion fan from the cowl lip of the internal nozzle dominate the overall flowfield development. The presence of freestream flow reduces the nozzle performance by approximately 4% relative to static conditions. Base pressure characteristics are observed to be strongly influenced by the movement of these shocks on the plug surface, and their subsequent interaction with the inner shear layer controls the base-wake closure. Relative to the conical plug conflguration, the contoured plug shows considerably enhanced base pressure characteristics. Real-time pressure measurements on the spike reveal highly unsteady flow in the intermittent region of separation.

Aerospike nozzle contour design and its performance validation

A simplified design and optimization method of aerospike nozzle contour and the results of tests and numerical simulation of aerospike nozzles are presented. The primary nozzle contour is approximated by two circular arcs and a parabola; the plug contour is approximated by a parabola and a third-order polynomial. The maximum total impulse from sea level to design altitude is adopted as objective to optimize the aerospike nozzle contour. Experimental studies were performed on a 6-cell tile-shaped aerospike nozzle, a 1-cell linear aerospike nozzle and a 3-cell aerospike nozzle with round-to-rectangle (RTR) primary nozzles designed by method proposed in present paper. Three aerospike nozzles achieved good altitude compensation capacities in the tests and still had better performance at off-design altitudes compared with that of the bell-shaped nozzle. In cold-flow tests, 6-cell tile-shaped aerospike nozzle and 1-cell linear aerospike nozzle obtained high thrust efficiency at design altitude. Employing gas H 2/gas O 2 (GH 2/GO 2) as propellants, hot-firing tests were carried out on a 3-cell aerospike nozzle engine with RTR primary nozzles. The performance was obtained under two nozzle pressure ratios (NPR) lower than design altitude. Efficiency reached 92.0–93.5% and 95.0–96.0%, respectively. Pressure distribution along plug ramp was measured and the effects of variation in the amount of base bleed on performance were also examined in the tests.

B213 NO-LIF及びPSPを用いたりニアエアロスパイクノズル側壁の最適形状に関する実験的解析

Aerospike nozzles have been expected as thrust nozzles for SSTO vehicles, because they show high performance in wide range of altitude or pressure ratio. Sidewalls for linear aerospike nozzles are indispensable to prevent the undesirable spanwise expansion of jets, which reduces the thrust. However, oversized sidewalls increase the weight of nozzles, and it is important to optimize the shape and the size of sidewalls. In this study, the flow field structures around the linear aerospike nozzles are visualized by using the laser induced fluorescence (LIF) technique and the pressure distributions on the nozzle spike are analized by the pressure sensitive paint (PSP) technique. The optimized shape of sidewalls is suggested by comparing the pressure distributions on the nozzle spike with three types of sidewalls and that without sidewalls.

Studies on Aerodynamic Behavior and Performance of Aerospike Nozzles

Experimental and numerical studies are carried out on a 6-cell tile-shaped aerospike nozzle, a 6-cell aerospike nozzle with round-to-rectangle primary nozzles and a 1-cell linear aerospike nozzle. Good altitude compensation capacities and high efficiencies are obtained in the tests. The efficiencies of 6-cell tile shaped aerospike nozzle and 1-cell linear aerospike nozzle at design altitude approach to 100%, and that of 6-cell aerospike nozzle with round- to- rectangle primary nozzles in the same condition is about 95% due to the imperfect cell contour and manufacturing defects. Numerical results are in good agreements with test data. The effects of ambient pressure on exhaust and then on base behavior are analyzed. The effects of variation in the amount of base bleed on performance are also examined in the tests.

クラスター型リニアエアロスパイクノズル噴流のＮＯ−ＬＩＦ及びＰＳＰを用いた実験的解析

完全再使用型宇宙往還機の推進用ノズルとして期待されるクラスター型リニアエアロスパイクノズルの実用化のため，本研究では噴流の干渉による複雑なノズル周りの流れ場をNO-LIF（レーザー誘起蛍光法）による任意断面での可視化によって詳細な解析を行うとともに，ノズル表面の複雑な圧力分布の解明やノズル表面に加わる圧力から推力の算出を可能にするためにPSP（感圧塗料）を適用して詳細な圧力分布計測を行った．その結果，NO-LIFによる可視化画像及びPSPにより得られた圧力分布から，隣接した噴射口より膨張する噴流同士の干渉を含んだ複雑な噴流構造を3次元的に解明するとともに，圧力比（貯気室圧力と膨張室圧力の比）が高い場合には，ノズル切断面直後で噴流が強く干渉して切断面に向かう流れが生じ，切断面の圧力が上昇することを明らかにした．この圧力上昇がスパイク切断による推力損失を補填すると思われる．

B310 NO-LIF及びPSPを用いた側壁付きリニアエアロスパイクノズルの評価

An aerospike nozzle has been expected as a candidate for an engine of reusable space shuttle to respond to growing demand for rocket-launching and its cost reduction. It has been reported that sidewalls of linear-type aerospike nozzles can suppress undesirable sideward flow expansion.In this study, the flow field around the linear-type aerospike nozzle with sidewalls and the nozzle without sidewalls are compared to confirm the effect of the sidewalls experimentally. Laser induced fluorescence is used to visualize and analyze flow fields around the nozzles. PSP is also applied to measurement of pressure distribution on the nozzle surfaces. The nozzles are set into a vacuum chamber to achieve larger pressure ratios PR (P s: source pressure in a reservoir, P a: ambient pressure in a vacuum chamber) because jet structures are affected mainly by pressure ratios.

Flow Field and Performance Analysis of Aerospike Nozzles with Simplified Clustered Modules

The fundamental characteristics of simplified clustered aerospike nozzles are analyzed by the computational fluid dynamics approach. Several types of aerospike nozzles, having 6, 12 and 24 inner nozzle modules with the same area ratio and total flow rate, are examined. The interactions of the exhaust flows from the neighboring modules create shock waves, which produce high-pressure regions on the nozzle surface. The base regions of the cluster-type aerospike nozzles are not influenced by the clustering of the modules and show features similar to axisymmetric-type aerospike nozzles. The base pressure is nearly equal to the environmental pressure when the pressure ratio is low and suddenly attains a constant pressure when the pressure ratio is high. The computed results show that the number of modules influence the thrust performance, and the major reason for the decrease in thrust performance with a smaller number of modules is due to thrust loss in the ramp region.

D110 クラスター型リニアエアロスパイクノズル噴流のNO-LIF及びPSPを用いた実験的解析

An aerospike nozzle has been expected as a candidate for an engine of a reusable space shuttle to respond to growing demand for rocket-launching and its cost reduction. It has been reported that flows of linear aerospike nozzles have three-dimentional structures. In this study, the flow field structures around the linear aerospike nozzles with and without sidewalls are analyzed and compared. Laser induced fluorescence (LIF) technique is applied to visualization of the flowfields in any cross sections. Since the flow field structure is affected mainly by pressure ratio (Ps/P a), the linear aerospike nozzle is set inside a vacuum chamber to carry out the experiments in the wide range of pressure ratios from 75 to 250. Pressure sensitive paint (PSP) of PtTFPP bound by poly-IBM-co-TFEM is also applied successfully to measurement of the complicated pressure distribution on the nozzle surface.

クラスター型リニアエアロスパイクノズル噴流の可視化と構造解析

Aerospike nozzles have been expected as a candidate for an engine of reusable space shuttles to respond to growing demand for rocket-launching and its cost reduction. In this study, the flow field structure in any cross sections around the linear-type aerospike nozzle are visualized and analyzed, using laser induced fluorescence (LIF) of NO seeded in the carrier gas N2. Since the flow field structure is affected mainly by the pressure ratio (P/P), the linear-type aerospike nozzle is set inside the vacuum chamber to carry out the experiments in the wide range of pressure ratios from 75 to 250. Flow fields are visualized in several cross-sections, demonstrating the complicated three-dimensional flow field structures. Pressure sensitive paint (PSP) of PtTFPP bound by poly(TMSP) is also applied successfully to measurement of the complicated pressure distribution on the spike surface.

B308 斜め平板に衝突する円形多孔ジェットのPSP解析

This study was conducted for an aerospike nozzle and to analyze the phenomena of the jet impingement, which was spout out from a circular nozzle with four or eight holes to a flat plate. The impingment was undertaken to be perpendicular and oblique to the plate. If the distance between the flat plate and the nozzle becomes close, an usual PSP analysis is difficult because the source of light, a camera and the nozzle can not be set up for the PSP measurements. Therefore, the pressure on the plate was observed from the back side of the a flat plate. Furthermore, the visualization of the impingement jet flow was studied by the oil film method.

側壁付きリニアエアロスパイクノズルのNO-LIFおよびPSPによる実験的解析(GS-13噴流・後流・対流)

側壁付きリニアエアロスパイクノズルのNO-LIFおよびPSPによる実験的解析(GS-13噴流・後流・対流)

Analytical and Experimental Studies of Tile-Shaped Aerospike Nozzles

In search of an engine for space propulsive application that has higher performance and easier implementation, a new aerospike nozzle with axisymmetric thrust cells and concave plugs is studied. Numerical and experimentalstudies were carried out for such a nozzle with an area ratio of thrust cells of 3.24 and an overall expansion ratio of 22.15. The theoretical formulations was based on three-dimensional Reynolds-averaged Navier-Stokes equations. Turbulence closure was achieved using a low Reynolds number k-e equation model. The companion experimental study utilized gaseous oxygen and alcohol as propellants. Results indicate that the tile-shaped plug resulted in a better flow force leading to a less restricting force-bearing condition for tile-shaped plug. For the tested model, a maximum nozzle efficiency of 0.95 near the design pressure ratio was obtained, and it has an obvious potential to increase performance by some percentage. Although the tile-shaped aerospike nozzle needs to be studied further, it is clear that it has high performance, has good altitude compensation ability, has case of implementation, and should be attractive for use in future propulsion systems.

A109 クラスター型リニアエアロスパイクノズル噴流の可視化および構造解析

Aerospike nozzles have been expected as a candidate for an engine of reusable space shuttles to respond to growing demand for rocket-launching and its cost reduction. In this study, the flow field structure in any cross sections around the linear-type aerospike nozzle are visualized and analyzed, using laser induced fluorescence (LIF) of NO seeded in the carrier gas N2 Since the flow field structure is affected mainly by the pressure ratio (Ps/Pa), the linear-type aerospike nozzle is set inside the vacuum chamber to carry out the experiments in the wide range of pressure ratios from 75 to 250. Flow fields are visualized in several cross-sections, demonstrating the complicated three-dimensional flow field structures. Pressure sensitive paint (PSP) of PtTFPP bound by poly(TMSP) is also applied successfully to measurement of the complicated pressure distribution on the spike surface.

Flow Field and Performance Analysis of an Annular-Type Aerospike Nozzle with Base Bleeding

Aerospike nozzle flow fields are computationally analyzed by Navier-Stokes simulations. The secondary flow from the base surface is induced for the purpose of increasing total thrust. The computed result shows that base pressure efficiently increases when base bleeding is induced from the tip region of the base surface and injected radially inward towards the nozzle axis. The base bleeding induced at the tip of the base and injected horizontally with the axis produces maximum base thrust because the momentum thrust does not produce any divergence loss and the base pressure is kept high. Base bleeding induced against the existing recirculation flow results in lower base pressure distributions. Base bleeding that produces maximum thrust interacts with the exhaust flow and creates shock waves that emanate from the tip of the base. The shear layer is squeezed more towards the nozzle axis when base bleeding is induced and forces the stagnation point to move closer to the base surface.