Numerical Simulation of Nozzle Flow Field with Secondary Injection Thrust Vector Control

A numerical study has been performed to characterize the nozzle flow field of secondary injection thrust vector control (SITVC) and to estimate the performance parameters of SITVC. After validating the CFD turbulence models with an experimental data, a numerical simulation has been conducted in order to investigate the influence of changing the injection location, the injection angle, and the primary nozzle divergence half angle on the SITVC nozzle flow field structure and on the SITVC performance parameters. The secondary mass flow rate was kept constant for all cases during the simulation. The results showed that downstream injection near the nozzle exit Mp=2.75 increases the high-pressure zone upstream the injection leading to an increase in the side force; also, the higher divergence half angle 15° slightly increases the side force and it provides a wide range of deflection without shock impingement on the opposite wall becoming more effective for SITVC. The injection angle in the upstream direction 135° increases the side force, and by decreasing the injection angle to downstream direction 45°, the side force decreases. However, the SITVC performance parameters and the flow field structure are more influenced by the injection location and the primary nozzle divergence half angle while being less influenced by the injection angle.

Numerical investigations have been conducted in order to find appropriate turbulence model and near wall treatments to study the effect of injection angle. For this purpose, different turbulence models such as k- e models (standard, RNG and realizable), and k- ω models (standard and the Shear Stress Transport (SST) model) were examined to solve for the most convenient accurate prediction of the flow field. In addition, two different wall functions (standard wall function and enhanced two-layer wall function were tested and compered with the experimental study at two blowing ratios (0.5, 1) and two injection angles (35o, 55o). It was found that the realizable k–e model with enhanced all treatment (two-layer approach) was in reasonable agreement with experimental data, which proved its advantage as compared with other turbulence models. So the realizable k–e model with enhanced wall treatment (two-layer approach) was selected in this paper to study the effect of injection angle variation. The film cooling geometry in the present paper is similar to that used in a previous study. The coolant flow temperature was kept constant at 188 K at a velocity 6.25 m/s and a constant density ratio of 1.6. The results showed a reduction in effectiveness for the injection angle of 55o as compared to effectiveness for the injection angle of 35o.

An Outer Planets Probe which retains the charred heatshield during atmospheric descent must deploy a sampling tube through the heatshield to extract atmospheric samples for analysis. Once the sampling tube is deployed, the atmospheric samples ingested must be free of contaminant gases generated by the heatshield. Outgassing products such as methane and water vapor are present in planetary atmospheres and hence, ingestion of such species would result in gas analyzer measurement uncertainties. This paper evaluates the potential for, and design impact of, the extracted atmospheric samples being contaminated by heatshield outgassing products. Flight trajectory data for Jupiter, Saturn and Uranus entries are analyzed to define the conditions resulting in the greatest potential for outgassing products being ingested into the probe's sampling system. An experimental program is defined and described which simulates the key flow field features for a planetary flight in a ground-based test facility. The primary parameters varied in the test include: sampling tube length, injectant mass flow rate and angle of attack. Measured contaminant levels predict the critical sampling tube length for contamination avoidance. Thus, the study demonstrates the compatibility of a retained heatshield concept and high quality atmospheric trace species measurements.

The launch vehicle will experience extreme acoustic environment at lift-off, which will cause the invalidation and destruction of the aerospace equipment, and reducing noise is of great significance for improving launch safety. In this paper, the numerical simulation of gas–liquid two-phase flow and its acoustic field is carried out, and the flow field is simulated by the discrete phase model (DPM), second-order Roe format, Scale-Adaptive Simulation (SAS) and three-dimensional Navier–Stokes. Based on the analysis of the flow field, the acoustic analogy integration method (FW-H) is used to predict the jet noise at the observation position. The influence of the water different injection angles and mass flow rate ratios are studied, and the results show that water injection not only reduces the temperature, velocity and vorticity at the gas–liquid interface, and the temperature at the bottom of the jet deflector, it also significantly reduces the jet noise. The total sound pressure level can be reduced to 6.92 dB by appropriate selection of the water injection angles and water injection mass flow rates. The numerical method established in this paper provides a useful tool for the design and analysis of water injection noise reduction for high-thrust multi-nozzle launch vehicle.

Large-eddy simulations (LES) of an under-expanded jet with and without fluidic injection have been carried out. Twelve injection nozzles angled at 60 towards the main jet axis are used for fluidic injection. The effect of two injection mass flow rates along with the amount of the fluidic injection are studied. Longitudinal vortices are generated when the micro jets impinge on the main jet and a thicker shear layer is formed when these vortices diffuse and merge together. Fluidic injection reduces shock-cell size and strength, elongates the potential core, and reduces the turbulence kinetic energy. Increasing the injection mass flow rate brings stronger modifications to the main jet. Shock-associated noise and mixing noise are both reduced, and more reduction is found near the region where shock-associated noise is generated. The magnitude of the high-frequency component is increased near the region where longitudinal vortices are present and this increases with the injection flow rate. The results of the larger injection flow rate are also compared with those of a chevron nozzle. The strength of the longitudinal vortices and the increased shear-layer thickness is comparable for both cases and a similar noise reduction is observed.

Model fractures with variable apertures are generated by a statistical method, and water flow and tracer transport in these fractures are calculated. Tracer injection and collection are simulated for parallel and convergent flow fields. The impact of the use of different injection flow rates and the different locations of injection and collection points are studied. The results show that the transport time, dispersion, and the so‐called mass balance fracture aperture are very sensitive to the location of the injection point and the injection flow rate. These anomalous effects appear to be consistent with observations in several recent field experiments. The implications of the calculated results on the analysis of tracer tests are discussed. It is concluded that because of the stochastic nature of variable fracture apertures (and their permeabilities) a point tracer test in a fracture is not sufficient to characterize the properties of the fracture. Dispersivities and apertures calculated from different tracer tests in the same fracture may vary by orders of magnitude depending on the flow rate and the location of the injection. However, a line injection of tracer, averaged over a series of adjacent points, may avoid some of these problems.

Lyapunov-based distributed secondary frequency and voltage control for distributed energy resources in islanded microgrids with expected dynamic performance improvement

Experiments were conducted to validate the building blocks of a fluidically controlled variable area turbine concept that uses injected high-pressure air to effectively reduce the choke area of the turbine inlet. Preliminary results from a simple quasi-1D converging-diverging nozzle, with an injection flow slot upstream of the throat, showed a 2.2:1 ratio between throttled mass flow rate and injected mass flow rate at a constant nozzle pressure ratio. The penetration of the injection flow and corresponding reduction in the primary flow streamtube were successfully visualized using a shadowgraph technique. Building on this success, a representative single passage nozzle guide vane transonic flowpath was constructed to demonstrate feasibility beyond the quasi-1D converging-diverging nozzle. Both secondary slot blowing from the vane pressure surface and vane suction surface just upstream of the passage throat again successfully reduced primary flow. In addition, fluidic vortex generators were used on the adjacent suction surface to reduce total pressure loss and further throttle the primary flow. Implications for application of this active flow control technology to a variable area turbine are considered.

In recent decades, the fluidic thrust vector control technique is one of the core strategies to redirect various aerospace vehicles, such as modern launch rockets, supersonic aircraft, and guided missiles. The fundamental theory of the shock vector control is that the gas is injected into the supersonic part of a conventional convergent–divergent nozzle from the transverse to cause interactions between the shock waves and boundary layers. Then, the deflection of the primary jet can be easily realized by the induced oblique shock waves. It was evident that the shock vector control is a very simple, low weight, low cost, and quick vectoring response technique to gain high thrust vectoring performance. In the present work, computational fluid dynamics studies were performed at different control parameters in a three-dimensional rectangular supersonic nozzle with the slot injector. For the validation of the numerical methodology, computational results were compared with experimental data referred to the NASA Langley Research Center. The static pressure distributions along the upper and lower nozzle surfaces in the symmetry plane were matched with the test data excellently. Numerical simulations were based on the well-assessed shear stress transport k–ω turbulence model. Second-order accuracy was selected to reveal more details of the flow-field as much as possible. Lots of factors were investigated, such as the momentum flux ratio, length-to-width ratio, injection location, and injection angle. The performance variations for different affecting factors were illustrated and some constructive conclusions were obtained to provide the reference for further investigations in fluidic thrust vector control field.

In this paper an exhaust ejector of boiler based on the principle of injection is mentioned. A three-dimensional numerical simulation on the exhaust ejector of boiler was carried out by using software FLUENT. The effect of the induced pipe geometric parameters (the length and outlet width) on the inner flow field with different conditions was obtained. The simulation results show that some factors, such as velocity distribution, static pressure distribution at the outlet of the pipe caused by the induced pipe geometric variation, are significantly related to injection mass flow rate, and the optimum geometry which can leads to the most injection mass flow rate is h=0.05m, b=0.02m.

The heat transfer of water in a vertically heated tube at 24.52 MPa is numerically simulated by computational fluid dynamics software of FLUENT. The IAPWS-IF97 formulation is applied to obtain the water properties, which vary substantially at supercritical condition. The two-dimensional axi-symmetric model using RNG k-ε turbulence model with enhanced wall treatment gives fine prediction of wall temperature and heat transfer coefficient. The mesh size near the wall adapted smaller when at high heat fluxes for the accuracy of computed results. The wall heat fluxes were set to be 233, 698, 930 and 1100 kW/m2 to match the simulation with experiment performed by Yamagata. It is found that k-ε turbulence model with enhanced wall treatment can give outstanding prediction of heat transfer enhancement and heat transfer deterioration. The heat transfer coefficient value reaches a maximum near the pseudocritical point and it decreases with increase of heat flux.

For an asymmetric scroll compressor for heat pump application, a numerical simulation was carried out to investigate the effects of injection port design on the compressor's performance under gas injection. To validate the simulation, the numerical results were compared with experimental results obtained from a scroll compressor with a base injection port design. There was good agreement between simulation and experimental results, with around a 1% difference in the injection mass flow rate when the injection pressure was below <TEX>$12kgf/cm^2A$</TEX> for the heating mode. Various injection port angular positions were numerically tested to yield better injection performance. The largest improvement in heating capacity was obtained at angles of <TEX>$240^{\circ}$</TEX> and <TEX>$200^{\circ}$</TEX> inward from the scroll wrap end angle for low-temperature and standard heating conditions, respectively, while the maximum COP improvement was at <TEX>$365^{\circ}$</TEX> and <TEX>$280^{\circ}$</TEX>, respectively. A considerable improvement in cooling capacity was also found at the injection port angle of <TEX>$240^{\circ}$</TEX>.

Parametric study on the sonic transverse jet in supersonic crossflow and analysis of the jet-crossflow interaction instability

Aerospike nozzles represent an interesting solution for Single-Stage-To-Orbit or clustered launchers owing to their self-adapting capability, which can lead to better performance compared to classical nozzles. Furthermore, they can provide thrust vectoring in several ways. A simple solution consists of applying differential throttling when multiple combustion chambers are used. An alternative solution is represented by fluidic thrust vectoring, which requires the injection of a secondary flow from a slot. In this work, the flow field in a linear aerospike nozzle was investigated numerically and both differential throttling and fluidic thrust vectoring were studied. The flow field was predicted by solving the Reynolds-averaged Navier–Stokes equations. The thrust vectoring performance was evaluated in terms of side force generation and axial force reduction. The effectiveness of fluidic thrust vectoring was investigated by changing the mass flow rate of secondary flow and injection location. The results show that the response of the system can be non-monotone with respect to the mass flow rate of the secondary injection. In contrast, differential throttling provides a linear behaviour but it can only be applied to configurations with multiple combustion chambers. Finally, the effects of different plug truncation levels are discussed.

In the present paper, an experimental and numerical investigation of fluid flow and heat transfer in the case of wall injection besides main flow through a circular sudden enlargement are studied. The injected flow is achieved through an annular slot placed around the inner side wall of the step. The static pressure variation along the sudden enlargement length is measured and calculated at different values of injection ratio ( Q ) and injection flow angles. The average heat transfer with Reynolds number (ReJ) of injected flow at different values of the inlet flow angle is obtained. The velocity, turbulent kinetic energy and temperature contours are presented in this study. Reynolds number of injected flow is varied between 320 and 840, Reynolds number of main flow is between 5895 and 8450 and the injection flow angles are 0 o , 15 o , 30 o , 45 o and 60 o . In the injection case, the results indicate that, the pressure recovery coefficient increases by decreasing the injection ratio and increasing the flow angle. The average heat transfer coefficient increases as both injection Reynolds number and the injection flow angle increase. The numerical results showed that two recirculation zones generate behind the step between the injection flow and the main flow. The size of these recirculation zones decreases by increasing the injection flow rate. The turbulent kinetic energy increases within region between the recirculation zones and main zone also, it decays by injecting flow in the recirculation zone. The length for higher value of flow temperature decreases by injecting flow in the recirculation zone, and that length increases as the injection flow rate increases. The comparison between the experimental results and the numerical results gives good agreement using the k-e model with Leschziner and Rodi correction.