Ducted Rocket Research Articles

Effects of momentum ratio on turbulent nonreacting and reacting flows in a ducted rocket combustor

A numerical study of turbulent nonreacting and reacting flows in a ducted rocket combustor with an ASM turbulence model and a finite-rate combustion model is reported. In addition, detailed measurements of flow velocities and turbulence parameters have been conducted by use of a four-beam two-color LDV system. Three different values of the ratio of fuel momentum to air momentum were selected to investigate its effects on the turbulent flow structure, mixing and combustion characteristics. It is found that the momentum ratio has strong effects on the number, size and rotational direction of dome region recirculation zones, reattachment length, axial fuel-jet spreading rate and penetration ability, flame temperature distributions and total pressure loss in the ducted rocket combustor. A useful correlation between the reattachment length and momentum ratio is derived. Moreover, a moderate value of the momentum ratio is recommended for better combustion performance and lower total pressure loss. The reported data are believed to provide valuable guidelines for practical design of combustors.

Burning Behaviour of Gas Generators with High Boron Content

AbstractGas generators with high boron content of interest for ducted rockets were prepared and characterized. The parameters tested were: combustion residue pressure exponent flow and temperature of the ejected boron particles mechanical properties. The results of the experments (optical bomb, high speed camera, two‐color pyrometer, thermal analysis, tensile test) are presented and discussed.

Effect of Boron Particle Surface Coating on combustion of solid propellants for ducted rockets

AbstractCombustion behavior of B/MA/AP/HTPB fuel rich propellants containing different coated boron particles was studied with several diagnostic facilities such as windowed strand burner, CO2 laser ignition facility, rapid depressurization quenched device, thermal analyzer and micromotor static test. Materials selected for boron coating include LiF, Viton A and silane. Baseline propellant containing uncoated boron was also studied for comparison Results from windowed strand burner and static test show that LiF‐propellant exhibits the most remarkable overall behavior. Ignition study indicates that LiF‐propellant gives the shortest while Viton A‐propellant gives the longest ignition time under the same heat flux. Moreover, mechanisms were proposed to elucidate the experimental results and the observed combustion phenomena.

Combustion of Energetic Fuel for Ducted Rockets (I)

AbstractEnergetic solid fuels composed of modified GAP (glycidyl azide polymer) propellants were formulated in order to obtain optimized combustion characteristics for variable flow ducted rockets. Burning rate in a primary combustor and the combustion efficiency in a secondary combustor were studied and evaluated as a function of the mixture ration of fuel and air. The energetic fuels consisting of – N3 groups in its chemical structure burned very rapidly even though the combustion temperature was low when compared with conventional solid propellants for rockets. The pressure exponent of the burning rate was optimized to gain wide range of mass generation rate. The combustion gases generated in the primary combustor burned very efficiently in a secondary combustor. The effective specific impulse of the ducted rockets was obtained to be about 780 s.

Numerical study of turbulent reacting flows in solid-propellant ducted rocket combustors

A theoretical model has been developed to investigate turbulent mixing and combustion processes in the main combustion chamber of a solid-propellant ducted rocket. The formulation is based on Favre-averaged conservation equations with a two-step chemical reaction scheme and is solved by a semi-implicit finite-difference method. Turbulence closure is achieved using a well-known k-e two-equation model. Calculated flow structures show good agreement with preliminary experimental results obtained from the schlieren flow-visualization study. The influences of various parameters, including dome height and inlet flow angle, on the propulsive performance of the system are investigated in detail.

Mixing, chemical reaction, and flowfield development in ducted rockets

Calculations have been made of the three-dimensional mixing, chemical reaction, and flowfield development in a typical ducted rocket configuration. The governing partial differential equations are numerically solved by an iterative finite-difference solution procedure. The physical models include the A; ~ e turbulence model, onestep reaction, and mixing controlled chemical reaction rate. Radiation is neglected. The mean flow structure, fuel dispersal patterns, and temperature field are presented in detail for a base configuration with a 0.058 m dome height, 45-deg side-arm inclination, and with gaseous ethylene injected from the dome plate at an eccentric location. In addition, the influences of the geometrical parameters, such as dome height, inclination of the side arms, and location of the fuel injector, are studied.

Investigation of a dual inlet side dump combustor using liquid fuel injection

The characteristics of a dual-inlet side-dump combustor configuration suitable for ducted rocket missiles was investigated by injecting a liquid fuel (JP-4) into the two rectangular inlet ducts upstream of the dump plane. Cold flow water tunnel simulations were obtained by injecting small air bubbles into the inlet arms of a plexiglas model and illuminating these by a high intensity slit light source. Combustor performance was obtained by testing a similar stainless steel model on a combustor thrust rig. Combustion efficiency, combustor total pressure loss, lean blow-out limits, combustor pressure oscillations, and surface heating patterns were obtained. A threedimensional computer code using the k-e turbulence model was used to predict the corresponding cold flowfields with good agreement.

Boron Combustion Characteristics in Ducted Rockets

Abstract A test program was performed with the objective of experimentally investigating the boron reaction characteristics in a ducted rocket by systematically varying the primary chamber conditions. In order to vary the primary chamber conditions a test device was used which burned boron powder and gaseous propellants (hydrogen or carbon monoxide, oxygen and nitrogen) in the primary motor. The reaction characteristics in the secondary chamber were observed by color photography through quartz windows of the secondary chamber. In the tests the following parameters were varied: (1) primary chamber temperature, (2) mixture ratio of the gaseous fuel in the primary chamber from below stoichiometric to above stoichiometric at different primary chamber temperature levels in order to vary the afterburning capability of the gaseous exhaust in the secondary chamber, and (3) secondary chamber pressure. At primary motor conditions which approximated propellants with high boron and low oxidizer/fuel content the boron particle temperature at the primary nozzle exit was not sufficient to initiate self-sustained boron combustion in the air. In order to farther heat up and cause ignition of the boron particles in the secondary chamber it was necessary to burn additional gaseous fuel in the secondary chamber. It was also demonstrated that the hot (probably reacting, but not ignited) boron particles were necessary for triggering the gaseous fuel ignition in the air.