Preface 1.General Considerations 2.Basic Processes in Atomization 3.Drop Size Distributions of Sprays 4.Atomizers 5.Flow in Atomizers 6.Atomizer Performance 7.External Spray Charcteristics 8.Drop Evaporation 9.Drop Sizing Methods Index

Atomization and Sprays

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Multi-component vapor-liquid equilibrium model for LES of high-pressure fuel injection and application to ECN Spray A

Mixing is a key point for thrust and efficiency of combustion systems. It becomes crucial in the case Liquid Rocket Engines as large investments are involved. Besides, the pressure in liquid rocket combustion chamber often exceeding the critical point of loaded propellants, mixing becomes an important scientific issue as fluid properties differ from classical ideal gas assumption. In this study, two configurations are studied to evaluate the impact of subgrid models on mixing. Firstly, Mayer's experiments of trans- and super-critical nitrogen jet injection into a warm nitrogen atmosphere have been numerically investigated with a structured numerical code called SiTCom-B. SiTCom-B solves Direct Numerical Simulations and Large Eddy Simulations equations for perfect or real gas equation of states. In this study, Soave–Redlich–Kwong (SRK) and Peng–Robinson equation of state are used with appropriated thermodynamics relations and validated against NIST data. Three-dimensional LES are conducted for two cases (cases 3 and 4 in Mayer et al.'s reference [1] ) with real-gas NSCBC treatment. Several sub-grid scale models are tested and the results are compared to experimental data for density on jet axis: a very good agreement is obtained on a light mesh (11.6 million of points) with the SRK equation of state and standard Smagorinsky model. Flow structures are evidenced with Schlieren snapshots. Secondly, the Mascotte test-bench from ONERA is simulated with SiTCom-B based on Soave–Redlich–Kwong equation of state and Smagorinsky models. The simulated non-reacting case is characterized by a very short liquid oxygen dense core because of the strong density and velocity gradients boosting mixing efficiency.

Large-eddy simulation of supercritical fluid injection

Turbulent flows of liquid nitrogen jets at near-critical and supercritical pressures are investigated by turbulence models (RANS) and a large eddy simulation (LES). To consider real-fluid effects, two real-fluid equations of state (EOS) are implemented into the numerical procedure and the normalized static enthalpy is introduced to describe the turbulent mixing under supercritical conditions. The pressure–velocity–density coupling is obtained by the modified PISO algorithm. The relative performance of six convection schemes and the predictions of four turbulence models for the different EOSs are compared with the available data. From the results, the suitable adoption of real-fluid EOS is more significant than the selection of turbulence model for the numerical performance. Additionally, the effects of SGS models are examined for the LES predictions using the different EOSs. The importance of real-fluid EOS is similarly found in the LES results. The coherent structures are strongly dependent on the different EOSs than SGS models. The results display that the selected RANS models need to be extended for supercritical fluid flows. Finally, the effects of turbulence models and SGS models on the jet spreading rate are discussed.

LES and RANS simulations of cryogenic liquid nitrogen jets

Modeling and analysis of heat and mass transfers of supercritical hydrocarbon fuel with pyrolysis in mini-channel

Thermodynamic modeling based on a generalized cubic equation of state for kerosene/LOx rocket combustion

Combustion characteristics such as combustion performance and combustion stability have been studied experimentally using a small liquid rocket thrust chamber with 19 liquid–liquid swirl coaxial injectors. Data were obtained from static pressure, temperature, and dynamic pressure sensors installed in propellant manifolds and the combustion chamber. While changing the recess length of the injector, characteristic velocity and pressure fluctuation data were collected and analyzed. In addition, chamber pressure was varied between 42 and 54 bar, which covers the sub- and supercritical pressures of oxygen. The results show that the longer recess length generally promotes combustion performance and the spray interaction between injectors in the multielement combustor increases the characteristic velocity. When the chamber pressure is above the critical pressure of oxygen, the recess length scarcely affects the pressure fluctuation. However, when the chamber pressure is below the critical pressure, the shift fro...

Effects of Injector Recess and Chamber Pressure on Combustion Characteristics of Liquid–Liquid Swirl Coaxial Injectors

Effects of injector recess on heat flux in a combustion chamber with cooling channels

An experimental study was carried out to investigate the combustion characteristics of liquid–liquid swirl coaxial injectors in a fuel-rich gas generator. Propellants of liquid oxygen and kerosene (jet A-1) were burned in a range of mixture ratios (0:29 0:38) and chamber pressures (53:6 57:9 bar) in several combustion chambers with differentdiametersandlengths.Aninjectorheadhad37identicalswirlcoaxialinjectorswithlargerecesslengthsand internal-mixingcharacteristics.Theinjectorheadwasconnectedtocombustionchambersandachokednozzleeither with or without an extension pipe. It was found that the combustion characteristic velocity, combustion gas temperature, and combustion dynamics were seldom influenced by the increase of injector recess length in the present fuel-rich conditions. The results of dynamic pressure data and swirl-injector dynamics suggest that the longitudinal-modecombustioninstabilityinthefuel-richgasgeneratorequippedwithbiswirlcoaxialinjectorscould besignificantlyaffected bytherelationship betweenthe resonant frequencyin thecombustion chamberandthe flow dynamics of the swirl injector.

Combustion Dynamics of Swirl Coaxial Injectors in Fuel-Rich Combustion

The dynamic characteristics of fuel-rich combustion have been studied using an experimental combustor simulating a gas generator for a liquid rocket engine. The combustor burns liquid oxygen and fuel (Jet A-1) at a mixture ratio of about 0.32 and a chamber pressure ranging from 4.10 to 7.24 MPa, which covers subcritical to supercritical pressures of oxygen. For the investigation of combustion dynamics, pressure fluctuation measurements using piezoelectric sensors have been a major probe throughout the present study. Two different types of injector heads equipped with biliquid swirl coaxial injectors and either a short nozzle or a turbine manifold nozzle have been used in the study. Fuel-rich combustion of both injector heads with the short nozzle revealed pressure pulsation at frequencies of about 128 Hz, which attenuates along with an increase of a chamber pressure. Combustion tests with the turbine manifold nozzle conducted at chamber pressures lower than the oxygen critical pressure showed combustion instabilities at a frequency of 330 Hz, which has been identified as a longitudinal resonant mode by a linear acoustic analysis. The combustion instabilities seem to be induced by inherent pressure fluctuations from the biliquid swirl coaxial injector when the chamber pressure is below the oxygen critical pressure.

Hwan-Seok Choi

Papers

Thermodynamic modeling based on a generalized cubic equation of state for kerosene/LOx rocket combustion

Effects of Injector Recess and Chamber Pressure on Combustion Characteristics of Liquid–Liquid Swirl Coaxial Injectors

Effects of injector recess on heat flux in a combustion chamber with cooling channels

Combustion Dynamics of Swirl Coaxial Injectors in Fuel-Rich Combustion

Combustion Dynamics and Stability of a Fuel-Rich Gas Generator