The Paper involves experimental and numerical heat transfer analyses of four pin-fin cooling configurations in a rectangular channel. Two design concepts were studied with two separate pin-fin (cylindrical and triangular) geometries. The first design includes a single-wall pin-fin configuration where the coolant flows through an array of full-length cylindrical (PF) and triangular pin fins (TF). The

A torsional thrust stand, calibrated for impulse bits in the range of 0.1–0.5 mN⋅s, was used to measure impulse bits from a metal plasma thruster. Impulse data were obtained on roughly 1400 shots, with metal plasma thruster targets of molybdenum, niobium, palladium, aluminum, and carbon. Model predictions (based on a simple circuit model and published plasma parameters) were validated by data from

Lifetime assessment of hollow cathode (HC) sources is an experimentally demanding process, due to the large amount of hours space qualification requires. In this Paper, we present a one-dimensional orifice model coupled to a global-averaged insert model, developed for lifetime prediction of a HC neutralizer in terms of orifice erosion; a modified sputtering yield curve is derived, similar to a previous

This Paper discusses the results of an experimental study to investigate the performance of a converging nozzle with fluidic thrust vectoring, using secondary-jet injection, through the measurements of various parameters such as thrust, flow rates, and pressures over a range of operating conditions. The thrust coefficient is found to be dependent on the nozzle pressure ratio (NPR) of the primary nozzle

A group of liquid simulants was developed in order to ease the process of cold-flow testing by lowering associated costs and hazards while providing accurate analysis of desired liquid behavior through an injector. Simulants were made with the intention of modeling certain physical properties of the liquid such as density, viscosity, and surface tension. These simulant solutions are capable of modeling

This study investigated the impact of fuel injection distribution on flame stabilization and heat release in a cavity-stabilized scramjet. Experiments were conducted using a hydrogen air heater that provided vitiated air at an average stagnation temperature of 1570 K and stagnation pressure of 12.7 atm, accelerated to a Mach number of 2.2 at the combustor entrance. Ethylene was injected using two fuel

Because of its excellent insulation capability, the usage of a silica-phenolic charring ablator as a nozzle liner is a common practice in the solid rocket motor industry. During the design of a solid rocket motor employing a silica-phenolic nozzle liner, it is desired to conduct an accurate analysis yielding in-depth thermal response and recession characteristics. As the interior ballistics and nozzle

The performance (specific impulse, Isp) of a modular, 150-lbf-class rotating detonation rocket engine (RDRE) was measured with three gaseous fuels (methane, ethane, and ethylene) and gaseous oxygen over a wide range of flow rates and equivalence ratios. All tests exhausted to sea level backpressure and were conducted using a calibrated thrust stand and Coriolis mass flow meters. Configurations tested

Computational fluid dynamics was used to study the flow through a scaled, mixed-compression, high-speed inlet with a rotating cowl at Mach 4.0 conditions. First, steady Reynolds-averaged Navier–Stokes computations were undertaken with a range of popular turbulence models including the Spalart–Allmaras model, the realizable k–ε model, the cubic k–ε model, and the Menter shear stress transport (SST)

The detrended fluctuation analysis, a technique for detecting long-range correlations in fractal time series, is used to characterize thermoacoustic oscillations of impending combustion instabilities. The slope of the linear regime of the structure function with respect to the time scale in a logarithmic plot, referred to as the Hurst exponent, takes a different value across a critical time scale corresponding

Because of their potential reductions of fuel consumption, disruptive propulsion concepts such as boundary layer ingestion have lately earned the attention of the aerospace community. Because of the increased level of interactions brought by the tight airframe–propulsor integration, an accurate assessment of this benefit requires a detailed study of the engine behavior from both an aerodynamics and

This study directly measures the performance of a thruster nozzle using water vapor as propellant in the Reynolds number below 1000. Because of its properties, water is suitable as a propellant for small satellites, often with a low-Reynolds-number flow using a micronozzle. The low Reynolds number of the flow and the phase changes in supersonic vapor flow should affect nozzle performance. It is essential

This paper describes the analysis of the flowfield in a four-stage low-speed axial compressor at the design point investigated both numerically and experimentally, with particular emphasis on the impact of stator hub flow leakage in a section of the machine featuring a change of stator configuration. The goal of the work is to give insight into the effect of the stator hub configuration on the aerodynamic

Flow visualization experiments, pressure and particle image velocimetry (PIV) measurements were conducted in supersonic internal compression inlet models in a Mach 2 flow. In the first phase of the study, the inlet model having a single sharp-edged shock generator on the upper lip of the inlet was investigated. In the second phase, another ramp was added to the floor of the single-ramp inlet model

The response behavior of capillary tube attenuated pressure sensor arrangements is studied using a rotating detonation engine as a nonlinear pressure wave source. The resulting measured pressures are examined as a function of the magnitude of the nonlinear pressure fluctuations, the mean pressure, and the forcing frequency applied to the pressure input port of the sensor. In addition, length and inner

Conventional expressions and definitions describing performance of plasma thrusters, including the thrust, specific impulse, and the thruster efficiency, assume a steady-state plasma flow with a constant flow velocity. However, it is very common for these thrusters that the plasma exhibits unstable behavior resulting in time variations of the thrust and the exhaust velocity. For example, in Hall thrusters

Journal of Propulsion and Power, Volume 37, Issue 1, Page 1-2, January 2021.

A rocket–ramjet combined cycle engine model, embedding twin rocket chambers driven with gaseous hydrogen and oxygen on the top wall side of a scramjet flowpath, was tested in its ejector-mode operation under sea-level static conditions. Gaseous hydrogen was also injected through secondary injector orifices to pressurize a ramjet combustor located downstream of the rocket chambers. Mixing between the

Experimental investigations on the self-pulsation dynamics in a gas-centered swirl coaxial atomizer are conducted using water and air. Experiments are performed in the pulsation regime by precisely varying the momentum flux ratio for different values of swirl number, recess length, and lip thickness. High-speed imaging is used to understand the underlying mechanism of the onset of pulsation. While

The T6 ion thruster is providing in-space propulsion for the BepiColombo mission, currently en route to Mercury. Simulations of the accelerator grid erosion during flight operation were carried out using the CEX2D and CEX3D codes in order to verify that the grid lifetime will be sufficient to impart the 5.75 MN⋅s total impulse per thruster required for the mission. Before calculating in-space erosion

The present paper numerically investigates the rotating stall mechanism in the NASA CC3 transonic centrifugal compressor with wedge-type vaned diffuser. The three-dimensional compressible, unsteady Navier–Stokes equations have been applied to a full-annulus high-speed centrifugal compressor comprising an inlet duct, impeller, and vaned diffuser. The scale-adaptive simulation model is selected as the

This paper discusses the aerodynamic analysis and design of a novel, hubless, contra-rotating, rim-driven fan (RDF) device. Rim-driven thruster technology has been used for marine propulsion for decades, yet RDF technology has not been comparably developed for aerospace applications. This paper demonstrates that an innovative two-stage contra-rotating RDF configuration provides the potential for a

The Photonic Laser Thruster (PLT) efficiently uses photons as propellant and thus promises to enable innovative space endeavors beyond the reach of propellant-based conventional thrusters. Previously, the proof-of-principle demonstration of PLT used a neodymium-doped yttrium aluminum garnet (Nd:YAG) rod gain medium and resulted in the maximum thrust of 35 μN. This Paper reports 100 times scaling up

In recent years, there has been significantly increased interest in using nitrous oxide as an oxidizer in hybrid rocket motor systems. The attraction of nitrous oxide is its low relative toxicity and high vapor pressure, potentially enabling self-pressurizing systems. Its decomposition is highly exothermic with a large energy barrier, typically requiring high temperature (700°C) to achieve appreciable

The paper presents an efficient method for analyzing complex periodic unsteady flows within turbomachinery. The method transforms the original initial value problem of unsteady flows to a boundary value problem by taking advantage of temporal periodicity known a priori. This transform allows a pseudotime marching at all physical time instants to be performed simultaneously, for which the method is

Aging induced changes in the mechanical properties of solid propellant can lead to defects, such as cracks and grain–liner separations, which limit the service lifetime of solid rocket motors. This Paper presents an active sensing in situ identification method based on the electromechanical impedance technique, which is particularly suited for monitoring aging of solid propellants. This Paper first

The lean blow-off (LBO) limits and structure of turbulent premixed flames were investigated with vaporized liquid fuels stabilized by a bluff-body burner. Ethanol, heptane, and two kerosenes were used. To facilitate comparisons to gaseous-fueled flames, results were also obtained from methane flames. The measured LBO limits indicate that, for this burner, the ethanol and heptane flames are more resilient

This Paper presents the results of a rotating detonation engine rocket sled test demonstration on a 127 mm gauge rail at 100 m long high-speed running track test equipment to evaluate the thrust performance of a stand-alone rotating detonation engine propulsion system. The developed sled test demonstrator contained all onboard subsystems, including engine, gas cylinders, valves, controller, and a data

Gaseous hydrogen/liquid oxygen turbulent shear coaxial flames were subjected experimentally to both pressure antinode (PAN) and pressure node (PN) transverse acoustic forcing as a function of the gas-to-liquid momentum flux ratio. The response of the flow was recorded using simultaneous high-speed imaging of backlit shadowgraphs and OH* chemiluminescence emission. It was observed that a wave amplification

An experimental investigation into small pressure-swirl spill-return atomizers was made to determine the effect of the entry port number, swirl-chamber shape, spill-line design, and the manufacturing precision on the spray quality and stability. The atomizers were studied using phase-Doppler anemometry, high-speed visualization, and mechanical patternation. Jet A-1 fuel was sprayed at inlet pressures

In this study, the effects of fuel port geometry and fuel additives on the performance characteristics of additively manufactured solid fuels in a hybrid rocket are explored. Static rocket motor firings were used to examine the performance characteristics, such as fuel regression rate and C* efficiency. Using a baseline fuel of poly(methyl methacrylate) (PMMA), a traditional center-perforated fuel

Slip in centrifugal compressors arises from imperfect guidance of the flow by the impeller blades and reduces the work input delivered by the impeller. Slip models are used to predict slip in preliminary design. However, slip models are typically calibrated with data that are not representative of modern aerospace compressors (i.e., pumps, turbochargers, or industrial compressors) and do not account

The gasification process of a low-melting fuel (polypropylene) in a high-temperature flow of inert gas (nitrogen) has been studied experimentally, implying the application to solid-fuel ramjets. The mass flow rate of gasification products attained the value of 8 g/s, and the ratio of the mass flow rates of the working gas and gasification products was 4.5. A semiempirical model for calculating the

Journal of Propulsion and Power, Ahead of Print.

A variety of methods have been developed to enhance solid propellant burning rates, including adjusting oxidizer particle size, changing the formulation, modifying the propellant core geometry, and adding catalysts or wires. Fully consumable reactive wires embedded in propellant have been demonstrated to increase the burning rate by increasing the surface area; however, the observation of this effect

Journal of Propulsion and Power, Ahead of Print.

A series of combustion tests was conducted to control and suppress the initiation of low-frequency instability (LFI) by using fuel inserts, through which a small step appeared gradually because of differences in the regression rates of the two materials; polymethyl methacrylate and high-density polyethylene. This small step acts as an artificial block that causes slight changes to the flow characteristics

Lean operation in the primary combustion zone of a gas turbine combustor is advantageous from NOx reduction point of view. The present work deals with the influence of lean primary zone operation on combustion performance, NOx emissions, and flame stability of a model gas turbine combustor with simplex atomizer. Air distribution is varied to operate the primary combustion zone from stoichiometric to

Aluminum (Al)/lithium (Li)-alloy-based fuels can potentially improve composite propellant performance and reduce hydrochloric acid formation. Shattering microexplosions have been observed in Al–Li-based composite propellants at 0.1 MPa; however, combustion characterization of Al–Li-based propellant as a function of pressure has not been performed previously. Measurement of the burning rate of an Al–Li

This paper investigates the influence of liquid jet fuel properties on flame lean blowout (LBO) using an annular coflow spray burner. This behavior has been studied before; however, inconsistent conclusions have been reached regarding the dependency of LBO performance on the properties that influence fuel atomization and mixture formation. LBO limits are measured at three different fuel flow rates

Two analytical models for computing the pumping speed of a vacuum chamber are derived. The models focus on the vacuum systems used for testing electric propulsion devices. The node model is based on a well-known calculation of the effective pumping speed adjusted by the conductance between the pump and the measurement location. The flux model is derived by balancing particle fluxes at two temperatures:

In this study, to reduce oxidizer to fuel ratio (O/F) shifts, which are a serious problem for a hybrid rocket used for launching a satellite, an altering-intensity swirling-flow-type hybrid rocket was developed. It can alter the swirl intensity instantaneously during operation by controlling the ratio of the swirling oxidizer flow rate to the axial oxidizer flow rate using ball valves. Eight firing

Journal of Propulsion and Power, Ahead of Print.

Journal of Propulsion and Power, Ahead of Print.

The design phase of a rocket combustion chamber relies on the prediction of the wall heat fluxes, in order to optimize the components to prevent thermal damage. Based on the experimental data of a subscale single-injector GCH4/GO2 combustion chamber at elevated pressure, this work thoroughly investigates the validity of a hybrid Reynolds–Averaged Navier–Stokes/Large Eddy Simulation turbulence model

An experimental study of a rotating detonation engine (RDE) operating with natural gas and air at elevated chamber pressures and air preheat temperatures was conducted to quantify its performance at conditions representative of land-based power generation gas turbine engines. The thrust produced by the combustor was measured to characterize its work output potential. High-frequency pressure transducers

This paper evaluates various sources of oxidizer to fuel mass ratio (O/F) shifts in hybrid rockets and paths (physical phenomena) through which these O/F shifts affect flight performance. Moreover, the performance increase of O/F control in hybrid rockets is evaluated. Vertical launches of O/F uncontrolled and O/F controlled of hybrid sounding rockets were simulated under two uncertainty models of

Reactive and nonreactive Reynolds-averaged Navier–Stokes simulations of hydrogen injection into a confined transverse supersonic flow of vitiated air are conducted. The corresponding conditions were studied in the LAPCAT-II combustor. Two operating conditions are considered, which differ in the value of the momentum ratio between the hydrogen and vitiated air inlet streams, thus leading to two distinct

Journal of Propulsion and Power, Ahead of Print.

This Paper explores keeper ignition and discharge characteristic of a hollow cathode center mounted on a Hall thruster to discuss the optimum startup sequence. A strong magnetic field along the hollow cathode in the center-mount configuration is considered to play an important role in the ignition and discharge; however, the characteristics in this configuration has never been reported. The effect

Journal of Propulsion and Power, Ahead of Print.

Bluff-body stabilized turbulent premixed flames represent a challenging canonical configuration for computational simulation and validation. Past simulation results from many research groups on the same bluff-body flame test case demonstrate significant variation that is neither fully understood nor quantified. To identify potential sources of this variation, three categories of sensitivities are assessed

Nondeterministic analyses were performed on a one-dimensional, steady, chemically reacting, reduced-order model for hydrogen peroxide flow through a monopropellant catalyst bed. Polynomial chaos expansion was implemented to decrease sampling time in order to perform the probabilistic analyses including quantification of global sensitivities using Sobol indices, construction of axial property uncertainty

Merging of corotating vortices is of primary interest in the field of supersonic mixing due to the ability of two or more structures to coalesce and form a larger one which enhances the stirring motion and straining in the flow, thus promoting turbulence production and mixing augmentation. During experimental efforts aimed at quantifying mean and fluctuating flowfields produced by the merging of two

An experimental study was performed on an ethylene/oxygen/air pulse detonation engine to examine the effect of frequency and spark delay time on the thrust output and efficiency. Reactants were mixed in a stainless-steel combustion chamber at frequencies ranging from 1 to 40 Hz. Dynamic pressure measurements were recorded throughout the system over the testing interval to determine exhaust velocities

There has been a recent need for rapid response power generation device on aircraft. Current power generators consume a large portion of the aircraft’s usable volume, and they are also extremely heavy relative to their power output; therefore, the need for compact, power-dense auxiliary power units or bleed air turbine (BAT) arose. A solution comes in the form of coupling rotating detonation engines

This Paper investigates the role of microcracks in Hall thruster wall erosion. The formation and growth of microcracks on the surface of M26 grade boron nitride composite due to repeated thermal shock was quantified, and the subsequent impact of microcracks on plasma erosion was assessed. Thermal shock cycles (20 → 800 → 20°C) were provided by a radiation oven to induce thermal stresses similar to

Journal of Propulsion and Power, Ahead of Print.

Oxidizer feed-system coupled instabilities have been observed in several liquid and hybrid propellant rocket engines, although they are not likely to be catastrophic for the latter. However, severe pressure oscillation in hybrid rocket may result in a significant reduction in the performance of the propulsion system restricting the application of the technology. In this research, feed-system coupled

A predictive numerical approach, based on Reynolds-averaged Navier–Stokes simulations including the effects of turbulence, chemistry, fluid/surface interaction, and radiation, has been developed for paraffin-wax/oxygen hybrid rocket engines. A recently fired single-port paraffin-based hybrid rocket engine, with chamber pressures up to 19.1 bar, is taken as reference for the discussion of the results