Nozzle Throat Research Articles

Numerical Study of the Dynamic Characteristics of Pintle Nozzles for Variable Thrust

Unsteady numerical simulations of pintle nozzles were implemented to investigate dynamic characteristics of various pintle configurations. To take into account the effects of the pintle shape and movement, a sliding mesh method was applied. The physical nozzle throat based on pintle location was analytically investigated and found to compare well with numerical results. The static and dynamic results are verified with the experimental results. The flow separation shock trains as the pintle strokes are analyzed according to the three pintle models. The response lag and sensitivity of the chamber pressure and nozzle performance were evaluated for pintle reciprocation, insertion, and extraction processes to better understand the dynamic performance of the pintle nozzle. The pressure coupling effects of the propellant burning surface during the pintle reciprocation are conducted, which are compared with the cold-flow cases.

Numerical and experimental investigation into passive hydrogen recovery scheme using vacuum ejector

The current work presents a numerical and experimental investigation into a passive ejector for recovering the anode off-gas in a proton exchange membrane fuel cell (PEMFC) system. The proposed ejector is consisted of a convergent-divergent channel and a suction channel, and it is connected with the anode outlet of PEMFC system for recovery the anode off-gas into the main gas supply. Numerical simulations based on a three-dimensional compressible steady-state k−ɛ turbulent model are performed to examine the effects of the inlet mass flow rate and nozzle throat diameter on the pressure, Mach number, temperature, suction channel mass flow rate, outlet channel mass flow rate, and suction channel entrainment ratio, respectively. The numerical results are confirmed by means of an experimental investigation. It is shown that supersonic flow conditions are induced in the ejector; resulting in the induction of a vacuum pressure in the suction channel and the subsequent recovery of the anode off-gas at the outlet of the main channel. In addition, it is shown that the mass flow rate in the suction channel increases with an increasing mass flow rate at the primary channel inlet. Finally, the results show that a higher entrainment ratio is obtained as the throat diameter of the nozzle in the ejector is reduced. Overall, the results presented in this study provide a useful source of reference for developing the ejector devices applied to fuel cell systems while simultaneously avoiding extra energy consumption.

Propulsive performance of a finite-temperature plasma flow in a magnetic nozzle with applied azimuthal current

The plasma flow in a finite-electron-temperature magnetic nozzle, under the influence of an applied azimuthal current at the throat, is modeled analytically to assess its propulsive performance. A correction to the nozzle throat boundary conditions is derived by modifying the radial equilibrium of a magnetized infinite two-population cylindrical plasma column with the insertion of an external azimuthal body force for the electrons. Inclusion of finite-temperature effects, which leads to a modification of the radial density profile, is necessary for calculating the propulsive performance, which is represented by nozzle divergence efficiency and thrust coefficient. The solutions show that the application of the azimuthal current enhances all the calculated performance parameters through the narrowing of the radial density profile at the throat, and that investing power in this beam focusing effect is more effective than using the same power to pre-heat the electrons. The results open the possibility for the design of a focusing stage between the plasma source and the nozzle that can significantly enhance the propulsive performance of electron-driven magnetic nozzles.

Experimental study of hydrogen production from reforming of methane and ammonia assisted by Laval nozzle arc discharge

The production of hydrogen from hydrogen compounds for fuel cell or internal combustion engine applications is a potential method for responding to the energy crisis and environmental problems. In this work carbon dioxide reforming of methane and decomposition of ammonia using a Laval nozzle arc discharge (LNAD) reactor has been exploited at atmospheric pressure without external heating or catalysts. CH4 (or NH3) conversion and H2 selectivity were observed to be negatively correlated with the concentration of CH4 (or NH3) and the flux of CO2 (N2) and positively correlated with voltage and the Laval nozzle throat radius. Power consumption increased with the concentration of methane at the same CO2 flow rate, and the conversion of methane gradually increased with the content of water vapor in the gas mixture. A high conversion rate and fair H2 selectivity were achieved, 51% and 37.5%, respectively, when the methane and carbon dioxide flow rates were 4 L/min and 14 L/min, respectively, and the minimum distance between the two electrodes was 2.5 mm. The LNAD reactor used in this study exhibited a good conversion rate and low energy consumption, which should be suitable for the industrial scale-up of the system.

Optimization of Process Parameters to Improve Form and Orientation Tolerances in EDM of MoSi2-SiC Composites

In this research, an investigation and experimental work were carried out on electric discharge machining (EDM) of intermetallic base MoSi2-SiC ceramic composite with copper electrode. It is extremely difficult to machine MoSi2-SiC composite using conventional machining techniques. However, it can be easily machined by executing spark EDM parameters to induce the correct optimum result. These composites find their application in high-temperature environments, viz. fuel turbo pump rotors, inlet nozzles, combustion chambers, injectors, nozzle throats, and nozzle extensions. The sparking parameters, namely current (I), pulse on time (Ton), pulse off time (Toff), spark gap (SG), and dielectric pressure (DP), were investigated by L18 orthogonal array. The optimal process parameters were determined by the grey relational grade (GRG) obtained through the grey relational analysis (GRA) for multiple performance characteristics, viz. material removal rate (MRR), electrode wear rate (EWR), circularity (CIR), cylindricity (CYL), and perpendicularity (PER). The significant process parameters were obtained by analysis of variance (ANOVA) based on GRG, which showed current, pulse on time, and DP. The results were finally established using a confirmatory experiment, which showed the spark eroding process could effectively be improved.

High-bandwidth scanned-wavelength-modulation spectroscopy sensors for temperature and H2O in a rotating detonation engine

The design and use of two-color tunable diode laser (TDL) absorption sensors for measurements of temperature and H2O in a rotating detonation engine (RDE) are presented. Both sensors used first-harmonic-normalized scanned-wavelength-modulation spectroscopy with second-harmonic detection (scanned-WMS-2f/1f) to account for non-absorbing transmission losses and emission encountered in the harsh combustion environment. One sensor used two near-infrared (NIR) TDLs near 1391.7 nm and 1469.3 nm that were modulated at 225 kHz and 285 kHz, respectively, and sinusoidally scanned across the peak of their respective H2O absorption transitions to provide a measurement rate of 50 kHz and a detection limit in the RDE of 0.2% H2O by mole. The other sensor used two mid-infrared (MIR) TDLs near 2551 nm and 2482 nm that were modulated at 90 kHz and 112 kHz, respectively, and sinusoidally scanned across the peak of their respective H2O transitions to provide a measurement rate of 10 kHz and a detection limit in the RDE of 0.02% H2O by mole. Four H2O absorption transitions with different lower-state energies were used to assess the homogeneity of temperature in the measurement plane. Experimentally derived spectroscopic parameters that enable temperature and H2O sensing to within 1.5–3.5% of known values are reported. The sensor design enabling the high-bandwidth scanned-WMS-2f/1f measurements is presented. The two sensors were deployed across two orthogonal and coplanar lines-of-sight (LOS) located in the throat of a converging-diverging nozzle at the RDE combustor exit. Measurements in the non-premixed H2-fueled RDE indicate that the temperature and H2O oscillate at the detonation frequency (≈3.25 kHz) and that production of H2O is a weak function of global equivalence ratio.

Research on the Molding Condition of 3D Braided Nozzle Throat Fabric

3D braided fabric lining mandrel weaving, throat is the key part of nozzle which should meet the requirements of molding. This paper based on the research between geometry and knitting yarn array of 3D braided nozzle fabric, proposed the basic conditions which influence the molding performance of nozzle. Theoretical derivation the formula of reasonable yarn array and cross-section parameters of yarn. Verify its correctness by actual production of 3D braided nozzle fabric. The CT scan image and the moire pattern of fiber volume percentage showed that the throat size of fabric and roundness well matched with mandrel, fiber volume percentage changed uniform which satisfied the requirement of engineering application.

Measurement of regression rate in hybrid rocket using combustion chamber pressure

An attempt was made in this paper to determine the regression rate of a hybrid fuel by using combustion chamber pressure. In this method, the choked flow condition at the nozzle throat of the hybrid rocket was used to obtain the mass of fuel burnt and in turn the regression rate. The algorithm used here is better than those reported in the literature as the results obtained were compared with the results obtained using the weight loss method and was demonstrated to be in good agreement with the results obtained using the weight loss method using the same motor and the same fuel and oxidizer combination. In addition, the O/F ratio obtained was in good agreement with those obtained using the weight loss method. The combustion efficiencies obtained were in good agreement with the average values.

Analysis of design parameters in anodic recirculation system based on ejector technology for PEM fuel cells: A new approach in designing

In this study, the anodic recirculation system (ARS) based on ejector technology in polymer electrolyte membrane PEM fuel cell is studied with employing a theoretical model. A practical method is presented for selecting or designing the ejector in an ARS, that offers the best selection or design. A comprehensive parametric study is performed on the design parameters of a PEM fuel cell stack and an ARS ejector. Four geometrical parameters consist of cell active area, cell number, nozzle throat diameter, and mixing chamber diameter in the design of ARS are intended. The effect of each contributes to the overall system performance parameters is studied. In this parametric study, the correlation between stack design parameters and ejector design parameters are studied. Eventually, based on the results, two dimensionless parameters are useful in the design process are proposed.

Numerical Simulation of Insulation Layer Ablation in Solid Rocket Motor Based on Fluent

A two-dimensional axisymmetric model was constructed to predict the ablation of the insulation layer in an end burning rocket motor by using the Computational Fluid Dynamics (CFD) software Fluent. The insulation material of graphite was used in the model. The wall surface reactions and discrete phase erosion were applied to simulate the insulation layer ablation. The influence of the burning surface movement was analyzed by using the dynamic mesh method. Numerical results show that the erosion rate increase with the increasing of burning time. The maximum erosion rate occurs at the upstream of the nozzle throat. There has a high erosion rate closing to the burning surface, and it decreases gradually away from the burning surface and becomes zero near the nozzle. It’s found that solid particle deposition appears on the inner surface of combustor closing to the nozzle, and it increases with the increasing of time.

Ejector primary nozzle steam condensation: Area ratio effects and mixing layer development

Recent ejector simulations based on wet steam modeling give significantly different performance figures relative to ideal gas modeling, but the origins of such differences are not clear. This paper presents a numerical investigation of flow in the primary nozzle of a steam ejector to further explore the differences between ideal gas and wet steam analysis of ejector flows. The wet steam modeling was first validated using primary nozzle surface pressure data from three experiments reported in the literature. Ejector primary nozzles with area ratios (AR) of 11, 18 and 25 were then simulated using wet steam and ideal gas models. The wet steam simulations show that nozzle static pressures are higher than those for ideal gas model, and in the AR = 25 case, the static pressure is larger by a factor of approximately 1.7. In contrast, no significant difference exists between the nozzle momentum flux for both ideal gas and wet steam models, except the vicinity of the nozzle throat where nucleation occurs. Enhanced mixing between primary and secondary streams, which arises because primary stream condensation reduces compressibility in the mixing layer, is proposed as an explanation of the increased entrainment ratio observed in recent wet steam ejector simulations.

Infrared laser absorption sensors for multiple performance parameters in a detonation combustor

Laser absorption sensors for temperature and H2O near 1.4 and 2.5μm, CO2 near 2.7μm, and CO near 4.8μm were developed, validated, and deployed in an ethylene-fueled pulse-detonation combustor (PDC). Each sensor was fiber-coupled to enable remote light delivery to the PDC and photo-voltaic detectors were mounted directly to the PDC for improved light collection. Measurements were acquired simultaneously along two orthogonal lines-of-sight (LOS) in both the PDC combustion chamber and the throat of a converging–diverging nozzle located at the PDC exit. Measurements in the nozzle throat were combined with a choked-flow assumption to calculate the time-resolved enthalpy flow rate exiting the PDC. All sensors used first-harmonic-normalized wavelength-modulation spectroscopy with second-harmonic detection (WMS-2f/1f) to account for non-absorbing transmission losses and emission. Furthermore, strong mid-infrared absorption transitions were used to enable improved measurement accuracy and precision. These sensors were validated in non-reactive shock-tube experiments at temperatures and pressures up to 2700K and 50atm. There, these sensors exhibited a nominal accuracy of 3 to 5% with bandwidths from 2 to 20kHz. Measurements in the PDC indicated peak temperatures near 3500K with near-stoichiometric proportions of H2O and incomplete conversion of CO to CO2. The stagnation enthalpy flow rate was highly transient, but repeatable with peak flow rates near 25MW.

Optimization Design on Variable Cycle Engine Performance Based on Genetic Algorithm

The article have described the optimization of the engine performance problem as nonlinear multi-objective programming, and have analyzed the operation principle of the variable cycle engine, made models of maximum thrust , maximum unit thrust, minimum oil consumption, and then adopts the genetic algorithm to solve the model, gained the guide vane angle of CDFS,the guide vane angle of low-pressure.Turbine and the nozzle throat area when the performance is optimal . It is a problem about multi-objective optimization, obtained a series of satisfactory solution and then selected a set of approximate optimal solution as the final argument. Lastly, The matlab software is used to illustrate the effectiveness of the results.

The Role of Nozzle Contour on Supersonic Jet Thrust and Acoustics

This work is an experimental and computational investigation of acoustics and performance of a biconical and splined supersonic nozzle to identify the dependencies of noise components on the nozzle design. The convergent section and throat of a biconical supersonic nozzle were optimized with a Reynolds-averaged Navier–Stokes solver to optimize thrust and minimize internal losses. Far-field acoustics and the jet flowfield were measured and studied using large-eddy simulations at design, overexpanded, and underexpanded conditions. The biconical and splined nozzles are designed to be thrust matched at fully expanded conditions. The convergent section and throat contour do not significantly affect the turbulent mixing noise or shock-associated noise at most conditions. Analysis of the jet flowfield shows differences in shock structure, although the “global” shock strength remains relatively unchanged. A comparison of measurements and computations of mean velocity and turbulence shows minor differences in the shear-layer region and near strong shocks. Momentum thrust and pressure thrust were measured and compared with computational results. The contoured throat nozzle provides equivalent thrust with a 4% lower nozzle pressure ratio at the design condition with no acoustic penalty. At equivalent nozzle pressure ratios, the contoured nozzle provides 10% higher thrust with no increase in mixing noise or shock noise.

Genetic algorithm to optimize the design of main combustor and gas generator in liquid rocket engines

A genetic algorithm was used to develop optimal design methods for the regenerative cooled combustor and fuel-rich gas generator of a liquid rocket engine. For the combustor design, a chemical equilibrium analysis was applied, and the profile was calculated using Rao’s method. One-dimensional heat transfer was assumed along the profile, and cooling channels were designed. For the gas-generator design, non-equilibrium properties were derived from a counterflow analysis, and a vaporization model for the fuel droplet was adopted to calculate residence time. Finally, a genetic algorithm was adopted to optimize the designs. The combustor and gas generator were optimally designed for 30-tonf, 75-tonf, and 150-tonf engines. The optimized combustors demonstrated superior design characteristics when compared with previous non-optimized results. Wall temperatures at the nozzle throat were optimized to satisfy the requirement of 800 K, and specific impulses were maximized. In addition, the target turbine power and a burned-gas temperature of 1000 K were obtained from the optimized gas-generator design.

Collection efficiency of round-nozzle impactors with horizontal annular inlet

In this study, a horizontal annular inlet was applied to a round-nozzle impactor in an effort to reduce the cut-off diameter. The collection efficiencies of round-nozzle impactors with either a vertical inlet, which has conventionally been used, or a horizontal annular inlet were investigated both numerically and experimentally. For the comparison, the nozzle width, nozzle-to-plate distance, impaction plate diameter, and flow rate of the aerosol drawn into the impactor were set the same for both the vertical inlet impactor and horizontal annular inlet impactor. A parametric study was performed to analyze the effects of the width of the horizontal annular inlet and nozzle throat length on the collection efficiency of round-nozzle impactors with nozzle Reynolds numbers ranging from 500 to 2600. By replacing the vertical inlet with the horizontal annular inlet, the square root of the Stokes number corresponding to the cut-off diameter could be reduced by approximately 30%. In other words, the value of (Stk50)1/2 was decreased from 0.49 to 0.32 or 0.33 when considering the effect of gravity.

The influence of Laval nozzle throat size on supersonic molecular beam injection

In this study, finite element analysis (FEA) has been used to investigate the effects of different Laval nozzle throat sizes on supersonic molecular beam. The simulations indicate the Mach numbers of the molecular stream peak at different positions along the center axis of the beam, which correspond to local minimums of the molecular densities. With the increase of the throat diameter, the first peak of the Mach number increases first and then decreases, while that of the molecular number density increases gradually. Moreover, both first peaks shift progressively away from the throat. At the last part, we discuss the possible applications of our FEA approach to solve some crucial problems met in modern transportations.

Experimental and Numerical Investigations of a Bypass Dual Throat Nozzle

The bypass dual throat nozzle (BDTN) is a new kind of fluidic vectoring nozzle. A bypass is set between the upstream convergent section and upstream minimum area based on the conventional dual throat nozzle (DTN). The BDTN shows a minimum or even no penalty on the nozzle's thrust performance, while it would be able to produce steady and efficient vectoring deflection similar to the conventional DTN. A BDTN model has been designed and subjected to experimental and computational study. The main results show that: (1) BDTN does not consume any secondary injection from the other part of the engine, while it can produce steady and efficient vectoring deflection. (2) Under the same condition, it can provide the maximum thrust vectoring efficiency of all the known fluidic thrust vectoring concepts reported in the literature. (3) The thrust vector angle is also greater than that of the conventional DTN that has been reported up to now. Especially, under NPR = 10, the thrust vector angle of BDTN can reach 21.3 deg. (4) For a wide NPR range from 2 to 10, the BDTN generates the best thrust vectoring performance under NPR = 4. Above all, the BDTN is well suited to produce vectored thrust for nozzles.

Preliminary tests of silicon carbide based concretes for hybrid rocket nozzles in a solar furnace

This research is part of the PERSEUS project, a space program concerning hybrid propulsion and supported by CNES. The main goal of this study is to characterise silicon carbide based micro-concrete with a maximum aggregates size of 800μm, in a hybrid propulsion environment. The nozzle throat has to resist to a highly oxidising polyethylene (PE)/N2O hybrid environment, under temperatures ranging up to 2980K.The study is divided into two main parts: the first one deals with the thermo-mechanical characterisation of the material up to 1500K and the second one with an investigation on the oxidation behaviour in a standard atmosphere, under a solar flux up to 13.5MW/m2.Young’s modulus was determined by resonant frequency method: results show an increase with the stabilisation temperature. Four point bending tests have shown a rupture tensile strength increasing with stabilisation temperature, up to 1473K. Sintering and densification processes are primary causes of this phenomenon. Visco-plastic behaviour appears at 1373K, due to the formation of liquid phases in cement ternary system.High-temperature oxidation in ambient air was carried out at PROMES-CNRS laboratory, on a 2kW solar furnace, with a concentration factor of 15,000. A maximum 13.5MW/m2 incident solar flux and a 7–90s exposure times have been chosen. Optical microscopy, SEM, EDS analyses were used to determine the microstructure evolution and the mass loss kinetics. During these tests, silicon carbide undergoes active oxidation with production of SiO and CO smokes and ablation. A linear relation between mass loss and time is found. Oxidation tests performed at 13.5MW/m2 solar flux have shown a mass loss of 10mg/cm2 after 15s. After 90s, the mass loss reaches 60mg/cm2.Surface temperature measurement is a main point in this study, because of necessity of a thermo-mechanical-ablative model for the material. Smokes appear at around 5.9MW/m2, leading to the impossibility of useful temperature measurements by optical pyrometry.Micro-concrete is really interesting for the nozzle realisation, thanks to its workability, and its thermo-mechanical properties. After 30s, mass loss in micro-concrete is one half of pure α-SiC. This result is really interesting to study SiC-based concretes in oxidising environments, instead of sintered α-SiC.

Numerical Design and Performance Analysis of 450 kW Segmented Arc Heater

A 450 kW segmented arc heater facility is designed and its performance is analyzed using a computational code named ARCFLO4. The constrictor length is set to 46.2 cm, which allows a proper constrictor diameter and a nozzle throat diameter of 1.4 and 1.2 cm, respectively, considering the stability of arc discharge. It is shown that the calculated mass-averaged enthalpy values are within the range from 12.3 to . The ratio of the centerline enthalpy to the mass-averaged enthalpy in the nozzle throat region is about 1.22, which signifies a fairly uniform total enthalpy distribution. The wall heat fluxes are also calculated to provide the information needed for designing the cooling system.