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

It has been recognized in recent years that high-altitude atmospheric ice crystals pose a threat to aircraft engines in flight. It is believed that ice can accrete inside the core compressor, although the mechanism by which this occurs remains poorly understood. To model ice crystal accretion, an estimate of the proportion of the impinging ice and water that sticks to a surface (the sticking efficiency)

This paper presents the use of a conventional computational-fluid-dynamics-based throughflow method to model the effects of a bypass fan in a propulsion system (for example, nacelle) under the restriction that information about the fan blade geometry is unavailable. Instead, the fan body-force model requires fan-performance data at different operating points as input. A simple implementation strategy

The effect of Tandem-Hole configuration on penetration and combustion in supersonic crossflow was studied using three injectors having two tandem holes of 0.7 mm diameter with a spacing of 5, 10, and 14 mm. A Single-Hole injector with the same injection area was studied for comparison. Shadowgraph results in Mach 1.9, Po=2.0 bar, To=305 K flow condition with kerosene as injectant indicated that higher

Aeroelastic instability in turbomachinery is one of the severe problems limiting its performance. Of particular interest is the phenomenon of stall flutter in compressors, which occurs when blades encounter large incidence flows. With the objective to understand the aerodynamics associated with stall flutter, the present experimental study is conducted on a subsonic annular compressor cascade. Five

Boron-containing coatings are actively used to improve the surface properties of mechanical parts of various devices and cutting tools. In this Paper, we demonstrate that deposition of boron-containing coatings by direct electron-beam evaporation of a boron target with a fore-vacuum plasma-cathode electron source can be used to substantially (by a factor of approximately 6–17) improve the lifetime

Journal of Propulsion and Power, Ahead of Print.

The combustion enhancement by ozone has been studied for single-component fuels in many different settings; however, the impact of ozone addition on a multicomponent fuel has been experimentally underexplored. This paper investigates the ozone-assisted flame propagation of a mixture of alkenes and alkanes in a low-pressure Hencken burner over a range of equivalence ratios, ozone concentrations, and

A liquid bipropellant rotating detonation rocket engine was successfully test fired. The 6.5-in.-diam engine operates on a mixture of rocket-grade hydrogen peroxide and triglyme. Ignition is accomplished hypergolically, with the addition of a promoter to the fuel. Eight cases of spontaneously initiated, single-wave, rotating detonations were observed. Detonation wave speeds were near or exceeding Chapman–Jouguet

A high-power nested Hall thruster was operated with cathode flow fractions from 7 to 3% of the total anode flow rate in a two-channel operating configuration at 27 kW total discharge power. The thruster was operated with a state-of-the-art high-current cathode featuring novel external propellant injectors. In stand-alone testing, the cathode has been shown to operate stably up to 300 A with a total

A numerical investigation of the performance of a supersonic combustor designed for a flight Mach 8 is presented. Numerical simulations are used to assess the characteristics and operational limits of the combustor at design and off-design conditions. The combustor design point corresponds to the cruise condition at a Mach number of 8 and an altitude of 30 km. Off-design conditions correspond to a

Three different heat exchangers (copper metal foam, copper disks, and stainless-steel disks) with lower effective surface areas than nominal catalysts used in thrusters were tested for nitrous oxide decomposition. These heat exchangers were preheated to thermal decomposition temperatures using an inductive heating system and placed in a vacuum bell jar to mitigate heat loss to the environment. Testing

Room-temperature ionic liquids offer a potential technological approach for propellant production on Mars using in situ resources. These unique salts can be employed to preferentially capture carbon dioxide (CO2) from the atmosphere of the planet for subsequent processing. To explore this application, CO2 and argon solubility experiments were performed with 1-butyl-3-methylimidazolium trifluoromethanesulfonate

Paraffin-based fuels incorporating solid amine boranes are investigated to identify formulations suitable for use as hypergolic hybrid rocket propellants. Their ignition delays are measured following contact with 90% white fuming nitric acid droplets. The mechanical properties of the paraffin binder and of the melt layer it produces are modified using an alpha-olefin polymer. The tests are carried

Hybrid rockets have several advantages with respect to current propulsion systems like simplicity, safety, reliability, environmental friendliness, and lower cost. To size the combustion chamber, it is fundamental to understand how the length, the external diameter, the volume loading, and the length-to-diameter ratio vary with the design parameters like scale, burning time, average mixture ratio,

Hypergolic hybrid motors are advantageous for rocket propulsion due to their simplicity, reliability, low weight, and safety. Many hypergolic hybrid fuels with promising theoretical performance are not practical due to their sensitivity to temperature or moisture. Ammonia borane (AB) has been proposed and studied as a potential hypergolic hybrid fuel that provides both excellent performance and storability

During their operation, solid rocket boosters experience axial stresses caused among other things also by fluid mechanical loads from the internal flow. The accurate prediction of the flowfield is mandatory for an accurate prediction of axial stresses and strains during the mission. In the present Paper, a very efficient but still accurate approach is presented to simulate the internal flow featuring

Flame behavior at conditions approaching boundary layer flashback was studied in fuel-lean premixed swirl flames with a central bluff-body flame holder. High-speed OH* chemiluminescence images were collected at over 450 different combinations of fuel composition (hydrogen/methane blends), equivalence ratio, flow rate, and reactant temperature. A selected group of conditions was further examined using

A pulsed electric thruster named Pulsed Electrogasdynamic (PEG) thruster was investigated. In this thruster, the propellant gas is accelerated gasdynamically to high exhaust velocities (10–15 km/s) by pulsed electric discharge. Laboratory models of the PEG thruster were developed and successfully operated for evaluation of performance potentials. The PEG thruster is intended for in-space propulsion

In recent years, phosphor thermography has received increased attention as an alternative to other common temperature measurement techniques (e.g., thermocouples, pyrometry). This technique has been successfully used for surface temperature measurements on coated surfaces (e.g., turbine blades, furnace walls) and, in some cases, mixed with a reacting material. However, this technique has yet to be

This work presents the modeling, control design, and simulation of a Cirrus SR20 with a hybrid electric propulsion (HEP) system composed of a combustion engine and battery-supplied electric drive that operates in one of two modes: 1) battery discharging and electric drive propelling, and 2) battery charging and electric drive generating. Given a supervisory-level system model, two optimization control

A novel diode laser-based ignition technique for hybrid propulsion systems has been developed. In an effort to determine the physical ignition mechanism, a test series was conducted in an optically accessible, slab-burning combustion chamber. High-speed imaging of the ignition event has revealed that high-temperature carbon particles created during laser-induced flash pyrolysis of the solid fuel grain

Journal of Propulsion and Power, Volume 36, Issue 4, Page 639-641, July 2020.

Rotating detonation engines (RDEs) are gaining significant interest as a practical approach to increasing the operating efficiency of propulsion systems through pressure gain combustion. To use RDEs in practical gas turbines, their stability and performance with regard to hydrocarbon fuels need to be tested. Prior experimental work has shown that ethylene/air systems exhibit suppressed wave propagation

The performance of a diode laser igniter as a restart-capable device has been assessed for single-port, poly(methyl methacrylate) (PMMA)/gaseous oxygen (GOX) hybrid motors. For this testing a prototype version of the igniter has been designed and implemented as a substitute to a traditional methane/GOX torch ignition system. Ignition tests have been conducted at atmospheric ambient conditions using

Iron oxide is the most common catalyst in solid rocket propellant. Increased performance of propellant by encapsulating iron oxide particles within ammonium perchlorate (AP) has been previously demonstrated, but only nanoscale particles were used, and encapsulation was only accomplished in fine AP (∼20 microns in diameter). In this study, the size of the particle inclusions were extended to micron

Reactive hydrocode calculations of shock-to-detonation transition in heterogeneous energetic (HE) materials need to be closed with burn models. One requirement of burn models is to supply a macroscale control volume with an energy release rate due to chemical reactions that reflects the subgrid physics of hotspot ignition and growth. Energy localization at hotspots delivers chemical energy at a rate

A generalized flat plate cascade model is developed in this study to predict the unsteady aerodynamics of a blade row with circumferentially nonuniform spacing in subsonic compressible flow. With no constraints on symmetry, this model can be applied to a blade row with any user-specified nonuniform blade spacing pattern. The effect of nonuniform blade spacing on compressor rotor forced response and

Journal of Propulsion and Power, Volume 36, Issue 4, Page 632-638, July 2020.