Numerical Behaviour of Primary Air Flow Field of a Swirl Injector Under High Pressure and High Temperature Condition

Injector plays pivotal role to meet better combustion performances requirements in terms of combustion efficiency, flame stability, ignition, lower emissions etc. In a multi-swirler injector, the primary swirler mainly dictates the airflow field inside and some extend outside the injector. Present CFD studies have been attempted to characterize the flow field of a swirl injector consisting of conical nozzle fitted with single radial swirler at its upstream. Studies are performed at high pressure and high temperature resulting to high density (increased by around 9 times compared to atmospheric condition) and its impact on the flow field in terms of location of energetic zones useful for fuel atomization. Since direct effect of increase in density lead to increase in turbulence which is helpful for mixing and atomization, this study is helpful to capture the same. Embedded LES based hybrid model has been used where the computational domain divided into 3 zones which are seamlessly connected by capturing the interface fluid dynamics. In LES zone, both the time and spatial scales have been resolved by suitably refining the grids. Analysis is carried out with CFL no. around 2, fixed time step of 1 micro second. The analysis is reasonably able to capture various unsteadiness (PVC, CTRZ, frequencies etc. useful for the atomization of the liquid fuel) which are not available beforehand.

Experimental and Numerical Investigations on the Ignition of RBCC Gas-Oxygen/Kerosene Rocket Ejector

The rocket ejector refers to a core component of a rocket-based combined cycle (RBCC) engine. The ignition is of critical significance for rocket ejection. Reliable and stable ignition crucially determines the normal operation of the engine. In this paper, a thrust chamber with coaxial swirl injector for the RBCC rocket ejection was developed and tested. Gas oxygen (GOX) and kerosene acted as propellants. As revealed from the test results, the process of ignition pressurizing comprised four phases. The oxygen prefilling time before ignition slightly impacted the ignition time, whereas it affected the peak pressure of ignition. In a confined range, the peak pressure decreased as the prefilling time was extended. The ignition was simulated by building a numerical model, and the results well complied with the experimentally achieved results. The numerical model is capable of specifically indicating the position of the kernel of fire and the process of flame propagation. The simulation results reveal that the propellant could form a combustible condition within 4 ms. The kernel was 6 mm away from the injector, located at the oxygen and kerosene mixing interface and approaching the upper wall. The above results reflected the vital role of the central recirculation zone formed by the prefilled oxygen. The ignition energy was transported near the injector under the convection effect, which ignited the stoichiometric mixture, and the entire ignition could reach a stable state within 20 ms. The numerical model which was developed in this paper can help clarify the combustion mechanism.

Vortex Breakdown Control by the Plasma Swirl Injector

Vortex breakdown, observed in swirling flows, is an interesting physical phenomenon relevant to a wide range of engineering applications, including aerodynamics and combustion. The concept of using a plasma swirler to control vortex breakdown was proposed and tested in this study. The effect of plasma actuation on controlling the onset and development of the vortex breakdown was captured by particle image velocimetry. Flowfield measurement results suggested that, by varying the strength of the plasma actuation, the location and size of the vortex breakdown region was controlled effectively. The plasma swirl injector offers a method for optimal control and efficient utilization of vortex breakdown. The method being proposed here may represent an attractive way of controlling vortex breakdown using a small amount of energy input, without a moving or intrusive part.

Injector and Combustion Chamber Design for a Nitrous Oxide and Ethanol Rocket Engine

The basic design of a rocket engine injector and combustion chamber for saturated nitrous oxide and liquid ethanol is presented. At first, an oxidant-fuel mixture is selected based on a thermochemical analysis that explores several existing options and other combinations that have not yet been studied. As a result, nitrous oxide is chosen as an oxidant and ethanol as fuel. Then a simplified methodology is proposed for the design of a pressure-swirl injector responsible for ethanol. Computational fluid dynamics is used to verify the validity of the above-mentioned analysis, using Volume of Fluid (VOF). For the nitrous oxide injector, the flash-boiling phenomenon is investigated, verifying its importance for the ongoing project. The effect is treated analytically using the Dyer model to account for non-equilibrium thermodynamics. Simplified zero-dimensional and one-dimensional combustion models are explored as tools to design the rocket combustion chamber. Furthermore, combustion instability due to acoustic phenomena is studied, with the first spinning tangential mode being computed for the herein developed motor and an ensemble of acoustic cavities being developed to suppress the aforementioned mode. Finally, a diagram of the static test bench which will be used to validate the injectors and the designed engine is also presented.