S. Sunil Kumar

• PhD
• Managing Director at Indian Space Research Organization

A crucial factor in the stability of high-pressure rocket-scale combustors is the temperature at which fuel is injected. This study investigates its effect on the stability of supercritical liquid oxygen (LOx)-methane combustion and highlights the impact of shear layer dynamics in cases with lower injection temperatures. The stability features of a...

A crucial factor in the stability of high-pressure rocket-scale combustors is the temperature at which fuel is injected. This study investigates its effect on the stability of supercritical liquid oxygen–methane combustion and highlights the impact of shear layer dynamics in cases with lower injection temperatures. The stability features of a rocke...

The optimization of injector dynamics is crucial for maximizing performance, reliability, and safety in rocket engines. This study investigates the intricate dynamics of an in-house designed co-axial swirl injector in a high-pressure LOx-CH4 rocket system. Introducing a novel methodology for swirl injector design that incorporates both flow and geo...

This work combines complex real gas thermodynamics and the flamelet generated manifold (FGM) combustion model within a large eddy simulation (LES) framework to investigate supercritical liquid oxygen (LOx)-methane injector dynamics. A validated numerical framework, based on the benchmark Mascotte chamber G2 RCM-3 (V04) test case, is utilized in thi...

This paper uses a reactive flow large eddy simulation (LES) and decomposition techniques to study combustion instabilities in a methane-oxygen combustor. This work examines two case scenarios to elucidate the significance of injector-chamber frequency coupling as the cause of thermo-acoustic instability. Initial investigation in a well-known benchm...

This paper uses a reactive flow large eddy simulation (LES) and decomposition techniques to study combustion instabilities in a methane–oxygen combustor. This work examines two case scenarios to elucidate the significance of injector–chamber frequency coupling as the cause of thermo-acoustic instability. Initial investigation in a well-known benchm...

The study explores the optimization of an in-house designed swirl coaxial injector for a LOx-methane rocket engine through computational fluid dynamics (CFD). A numerical framework with real fluid thermodynamics, flamelet-based combustion closure, and SST k-omega turbulence model is invoked to simulate transcritical injection and supercritical comb...

The optimization of injector dynamics is crucial for maximizing performance, reliability, and safety in rocket engines. This study investigates the intricate dynamics of an in-house designed co-axial swirl injector in a high-pressure LOx-CH4 rocket system. Introducing a novel methodology for swirl injector design that incorporates both flow and geo...

In the current scenario of next-generation launch vehicle development, additive manufacturing/3D printing plays an immense role in reducing the complexities of conventional machining and lead times for realization. Injectors are the most important elements that control combustion efficiency. Typically, injectors are realized through precision machi...

This paper presents the computational methodology developed to simulate monomethyl hydrazine/nitrogen tetroxide (MMH/NTO) combustion. A three-dimensional rocket scale combustor domain with multi-element triplet injectors is utilized to study hypergolic flow and flame features. A Eulerian–Lagrangian framework is invoked for continuous phase treatmen...

This paper investigates combustion dynamics in a complex multi-injector element combustor using a flamelet approach in a large eddy simulation (LES) framework. The capability of computationally less expensive chemistry tabulation method to capture the interaction between unsteady heat release and acoustics is investigated. A non-adiabatic steady fl...

Numerical simulation is carried out to understand the effect of impeller exit width on centrifugal pump rise, rotating stall progression and oscillation frequency with variation in flow coefficient. Steady and transient flow simulations of centrifugal pump were carried out for different flow rates. A comparative analysis of simulation results shows...

Computational Fluid Dynamics (CFD) study of liquid oxygen draining in a spinning tank with and without baffles is carried out for hybrid propulsion rocket. The effect of tank spinning and the presence of baffles on the vortex formation and unusable propellant mass is brought out in this work. The interface of the draining propellant is captured usi...

Diffusion combustion finds application in various practical combustion devices such as gas turbine combustors and liquid rocket engines. Liquid rocket engines require a turbo pump for feeding the propellant into the combustion chamber. The turbine of the turbo-pump system operates with high-temperature gas generated by a pre-burner or gas generator...

Numerical analysis of the hot oxygen rich exhaust gas flow field during the ground test of engine subsystem is carried out in the present paper. The effect of water injection on the hot gas plume and its impingement velocity on the test bay is studied. The effect of the wind conditions such as velocity and directions on the oxygen concentration in...

Impingement of satellite thruster plume on the adjacent surfaces of the satellite generates disturbance torques and heat loads that are undesirable. It is therefore important to configure the spacecraft such that the impingement effects of the thruster plume are minimized. In the present work, Computational Fluid Dynamics (CFD) study of plume expan...

ISRO’s role in delivering cost-effective launch solutions has been known worldwide for quite some time. The LVM3 launch vehicle recently injected multiple satellites into a low earth orbit using its terminal cryogenic stage. The cryogenic stage was re-configured for the short-duration orbital mission with a short mission planning and stage realizat...

The article investigates liquid oxygen (LOx)–methane supercritical combustion dynamics in a multi-element rocket-scale combustor using large eddy simulation (LES). A complex framework of real gas thermodynamics and flamelet-generated manifold (FGM) combustion model is invoked to simulate transcritical oxygen injection and supercritical methane comb...

The article focuses on a comprehensive review and numerical analysis of LOx(Liquid Oxygen)-methane combustion at supercritical pressures. A detailed review of numerical and experimental investigations on LOx-methane combustion is conducted to understand the transcritical injection and supercritical combustion process occurring in a typical high-pre...

This paper presents the computational methodology developed to simulate mono-methyl hydrazine/nitrogen tetroxide (MMH/NTO) combustion. A three-dimensional rocket scale combustor domain with multi-element triplet injectors is utilized to study hypergolic flow and flame features. A Eulerian-Lagrangian framework is invoked for continuous phase treatme...

This paper investigates combustion dynamics in a complex multi-injector element combustor using a flamelet approach in a large eddy simulation (LES) framework. The capability of computationally less expensive chemistry tabulation method to capture the interaction between unsteady heat release and acoustics is investigated. A non-adiabatic steady fl...

The present numerical study investigates the air turbulence intensity effect on soot formation in a confined methane-air turbulent jet diffusion flame. The numerical simulations are conducted using RANS-based modified k-ε concept, whereas the combustion is modeled using a steady laminar flamelet with β-probability density function with GRI 2.11 det...

This paper describes the experimental and numerical works conducted to decipher the phenomenon of direct contact condensation (DCC). DCC, being a homogeneous condensation process, is characterised by extremely high heat transfer coefficient and very high turbulence across the interface. The study was initiated with experiments of steam condensation...

Hysteresis effect on thermal contact conductance due to load cycling is well documented for joints at ambient temperature. However very limited information is available at cryogenic temperature. The thermal cycling of joints to cryogenic temperature is also an unexplored area. In addition, the change in heat flow direction on thermal contact conduc...

This paper invokes a reactive flow large eddy simulation (LES) framework to simulate combustion instabilities in a sub-scale rocket combustion chamber. A model rocket combustor of Purdue University called the continuously variable resonance combustor (CVRC) [1] is used to simulate and understand the mechanisms of thermo-acoustic instability. The ex...

A high thrust liquid oxygen-kerosene fuelled engine is being developed for future launch vehicle applications. Comprehensive hot testing of engine at sea level conditions is required for qualification and acceptance of flight engine and launch vehicle stage. The engine and stage will be tested in a specialized rocket engine and stage hot test facil...

Heat transfer across pressed joint is significantly governed by thermal contact conductance which in turn depends on thermophysical properties of materials in contact, surface properties, contact pressure, working temperature and interstitials present at the interface. Application of interstitials is an effective technique to control thermal contac...

An experimental study has been conducted on Direct Contact Condensation (DCC) of inversely buoyant subsonic steam jet in subcooled water. An z-type Herchellian shadowgraph setup with high speed camera was used to capture steam condensation in water. Steam, a lighter fluid was injected into water, a denser fluid stored in a transparent cuboidal test...

A high thrust liquid oxygen-kerosene fueled engine is being developed for future launch vehicle applications. The engine will undergo hot tests under sea level conditions for flight qualification and acceptance of launch vehicle stage. The engine and stage will be tested in flame deflector facility and rocket plume is sufficiently cooled before imp...

All engines of launch vehicles are extensively tested before being inducted into the flight. The sea level test stand of high thrust semicryogenic engine has flame deflector pit lined with metallic plates to divert the high temperature supersonic engine exhaust away from the test stand. The flame deflector is cooled by injecting large quantity of w...

The study brings out the use of geysering effect by introducing a parallel heated line, through feedline looping method, in a cryogenic tank. Geysering in cryogenic feedline occurs due to exposure of continuous heat in-leak during launch phase. The ambient and aerodynamic heat in-leak into the feedlines during the lift-off phase of launch vehicles...

The flow rate regulator (FRR) is employed in liquid rocket engine to control the fuel flow rate to the pre-burner and in effect, to control the engine thrust. The fuel flow rate regulator keeps the mass flow rate of fuel as required by adjusting the area of opening according to pressure fluctuations at the outlet. A comprehensive mathematical model...

Cryogenic engine based launch vehicles carry liquid oxygen (LOX) as oxidizer and liquid hydrogen (LH2) as fuel. These propellants are stored in large tanks having low structural mass for gaining payload advantage. LOX and LH2 are stored at sub-cooled temperatures of 77K and 20K, respectively. One of the downside of sub-cooling the cryogenic tank is...

Propellant combinations such as Liquid Oxygen (LOx)-hydrogen and LOx-kerosene are commonly used in liquid rocket engines. Recently, LOx-methane combination has attracted considerable attention for future development of reusable launch vehicles (RLV). Methane is widely accepted as an alternative fuel for new generation propulsion systems because of...

In recent years, LOX-Methane propellant combination has attracted lot of attention because of its various advantages compared to typical LOX-hydrogen/kerosene rocket engines. Medium to high thrust class methane engines are envisioned to replace existing propulsion system in launch vehicles. It is prerequisite to understand combustion characteristic...

Our current and upcoming liquid rocket engines operate at high pressures, which are generally above the critical pressure of propellants. At supercritical conditions, rocket propellants exhibit liquid like densities and gas like diffusivities, with no clear inter-phase boundary. In such conditions, inter-molecular forces and surface tension diminis...

India's mission to Mars was a huge success considering first interplanetary endeavor undertaken by the country. As per the mission plan, LAM and eight AOCS engines were operated on blow-down mode during MOI. The propellant tank pressure falls continuously due to blow down operation, resulting ullage cooling. This may lead to propellant freezing if...

The upcoming Chandrayaan-2 mission of ISRO is planned to deploy a lunar lander and rover on a specified lunar site. The mission objective is to ensure a safe and soft landing of lander module on the lunar surface. The lander-craft will be released from lunar orbit, which will further undergo various lunar bound phases like de-boosting, rough brakin...

In recent years, LOX-Methane propellant combination has attracted lot of attention because of its various advantages compared to typical LOX-Hydrogen rocket engines. ISRO is currently envisioning a 10T class methane engine to replace existing propulsion system in its launch vehicles. Transcritical methane experience large thermodynamic and transpor...

A transient, thermodynamic flow model is developed to simulate pressure oscillations in cryogenic fluid occurring due to sudden closing of valves, a phenomenon commonly known as fluid-hammering. The effects of line dimensions and flow rate changes on amplitude and frequency of these oscillations are investigated using numerical analysis. The model...

Cryogenic tanks used for space applications are filled with sub-cooled cryogenic propellants, whose liquid-vapor interface remains undisturbed for long periods of time prior to launch. During this period, substantial amount of heat leaks into the tank from external sources such as solar and ambient convective fluxes, even though the tank is well in...

Thermal Contact Conductance (TCC) at low temperature is of keen interest to researchers in the fields of aerospace, superconductivity, high speed semiconductor devices, cryogenic interfaces etc. Change in thermal contact conductance at low temperature is associated with different factors like improved mechanical properties, differential contraction...

A transient two-phase numerical model is developed to investigate insulation performance of cryogenic propellant tanks using finite difference method. The model includes the mathematical formulations for convective and radiative heat transfer from the ambient, heat and mass transfer across liquid-vapor using two- phase formulations. The model is va...

A computational model is developed using SINDA/FLUINT code to investigate chilling performance of cryogenic turbo pump bearing coolant cavity. The chilldown study is carried out with coolant gas flow followed by two-phase cryogenic propellant flow. The model includes the mathematical formulation for the complex two-phase flow process and predicts t...

Cryogenic fluid entering a warm feedline absorbs heat and undergoes rapid flash evaporation leading to pressure surges which can retard the flow inside the feedline. It may have serious repercussion in operation of the rocket engine during start up. Experimental and numerical studies are carried out to examine the effect of inlet pressure and initi...

A numerical model to investigate chilling performance of cryogenic feed systems is developed using finite difference formulation. The model includes the mathematical formulation of complex two-phase flow phenomena during chilling and predicts chilling time, transient pressure and flow evolution in cryogenic feedlines. Model captures the pressure su...

Sloshing in the cryogenic propellant tank of spacecrafts is a significant phenomenon which is considered during the design of structural and thermal systems. A study is carried out to determine the effect of sloshing on pressure and temperature in ullage space of cryogenic propellant tank. A transient thermodynamic slosh model is developed using fi...

In a cryogenic launch vehicle system, reduction in propellant tank pressure during engine operation may cause engine pump cavitation and thrust degeneration. Analytical study is carried out to determine the effect of pre-pressurant helium gas and its temperature on the evolution of tank pressure during flight considering the effect of sloshing. A t...

An experimental study to investigate heat transfer characteristics of kerosene/alumina nanofluid at turbulent flow regime is carried out. The study intends to explore the potential use of kerosene-alumina nanofluid in semi-cryogenic rocket thrust chamber for regenerative cooling. The study involves measurement of thermal conductivity, viscosity and...

The present work investigates kerosene-alumina nanofluid for its stability, thermal conductivity and viscosity at low volume concentration of nanoparticles. The study intends to explore the possible application of using kerosene-alumina nanofluid in regenerative cooling channels of semi-cryogenic rocket engine. Nanofluid is prepared and characteriz...

Transient numerical simulations are carried out to investigate the liquid-gas interface characteristics associated with liquid film cooling flows. A two-dimensional axisymmetric multi-phase numerical model using finite volume formulation is developed. The model has been validated against available experimental data for liquid-film cooling flows ins...

The flow field associated with cylindrical coolant jets inclined in tangential and azimuthal direction employed inside a circular pipe has been studied. Numerical results are compared with in-house experimental data for a row of circumferential film cooling holes with two distinct geometric configurations. Results provide insight into the film cool...

Experimental and numerical investigations are carried out to analyze the effect of tangential coolant injection on overall film cooling performance in a cylindrical test section simulating a high curvature surface. Experiments are conducted using hot air as core gas and nitrogen gas as coolant injected through cylindrical holes inclined at 30-degre...

A thorough experimental investigation of the thermophysical properties (thermal conductivity, viscosity, and specific heat), heat transfer performance, and pressure drop characteristics of aviation turbine fuel (ATF)-based Al 2O 3, TiO 2, and CuO nanofluids was carried out for potential regenerative cooling application in semicryogenic rocket engin...

Experimental and computational results are presented that describe gaseous film-cooling performance of straight cylindrical cooling holes inside a cylindrical test section similar to a rocket combustion chamber. Experiments were performed using hot air as the core gas and gaseous nitrogen as the film coolant. A three-dimensional multispecies comput...

Nanofluids are suspensions of high thermal conductivity nanoparticles in a base fluid, and offer potential to enhance the thermal conductivity and heat transfer performance of the base fluid. The present work measures the thermo-physical properties, heat transfer performance and pressure loss characteristics of Aviation Turbine Fuel (ATF)-titanium...

Aviation Turbine Fuel (ATF)-Al2O3 nanofluids are investigated for better heat transfer performance in a potential application of regeneratively cooled semi-cryogenic rocket engine thrust chambers. The volume concentration of Al2O3 nanoparticles is varied between 0 and 1%. To ensure a realistic evaluation, all properties of the nanofluids are experi...

The effect of Alumina nanoparticle size on thermophysical properties, heat transfer performance and pressure loss characteristics of Aviation Turbine Fuel (ATF)-Al2O3 nanofluids is studied experimentally for the proposed application of regenerative cooling of semi-cryogenic rocket engine thrust chambers. Al 2O 3 particles with mean diameters of 50...

An experimental investigation is conducted to bring out the effects of coolant injector configuration on film cooling effectiveness, film cooled length and film uniformity associated with gaseous and liquid coolants. A series of measurements are performed using hot air as the core gas and gaseous nitrogen and water as the film coolants in a cylindr...

The effectiveness of Molybdenum-sulphide (MoS2) coating on aluminum stainless steel contacts at different interface temperatures and loads was determined. The thermocouples were calibrated between 200 and 300 K using a high-accuracy, dual-temperature, dry-block calibrator. Higher conductance is obtained with MoS2 coated over aluminum than with stai...

The effect of evaporation on stratification in large liquid hydrogen storage tanks of different aspect ratios is computed. A homogeneous two-phase model is used and the continuity, momentum and energy equations for the two phases are solved. Evaporation at the liquid–vapor interface is incorporated through a source term for mass transfer. The amoun...

Experiments were conducted to determine the variation of interface temperatures during the storage and draining of liquid nitrogen from large containers in the presence of the non-condensable gas. A chilled layer was seen to be formed at the interface in the presence of the non-condensable gas and this layer advanced into the warm liquid at speeds...

The influence of variations of interface temperature in the range 50–300 K on the thermal contact conductance between aluminium and stainless steel joints was determined. Predictions were done by modeling the deformation at the interface for different values of surface finish and contact pressure over the range of interface temperatures. Both elast...

A prediction methodology based on Monte-Carlo simulation model, developed for flat conforming surfaces in contact, is modified and extended to predict contact conductance between curvilinear surfaces like cylinders and spheres. Experiments are also conducted in vacuum for the measurement of contact conductance between stainless steel and aluminium...

The effect of surface roughness, waviness and flatness deviations on thermal contact conductance is predicted. Threshold values of the surface parameters which do not adversely influence thermal contact conductance are determined. Flatness deviations less than ten times the average roughness and waviness less than about four times the average rough...

A theoretical model is formulated to determine the instability of flow of subcritical liquids supplied from a reservoir to warm pipelines. The model predicts the waveform of the oscillations to get clipped for certain lengths of pipeline and a range of forced convective heating. Clipped oscillations are obtained when the ratio of residence time of...

Experiments were conducted for condensation taking place over thick layer of moving subcooled liquid. Measurements were done over a wide range of liquid subcool temperatures and Reynolds numbers. The measured values of condensation heat transfer coefficients were correlated with Reynolds number, Prandtl number and the degree of subcooling. The role...

Predictions of thermal contact conductance between two conforming Rat surfaces in vacuum are carried out. The prediction model considers heat flow through the contact zones of asperities on the surfaces by conduction, The probability of occurrence of contact between the surface asperities is evaluated using a Monte Carlo simulation, ii Gaussian dis...

Predictions are carried out for radiation heat flux incident on a base surface from a gaseous conical plume with radial and axial temperature variations. A forward Monte Carlo method is developed and validated by comparing the results of an isothermal cylindrical plume, a conical plume with axial temperature variations, and a cylindrical gas-filled...

The present study considers a space radiator with uniform area fins standing vertically on a nonisothermal parent surface to enhance heat transfer. The numerical study shows that the finned radiator exhibits an optimum number of fins for which the heat lost from the finned radiator is a maximum, for given values of NR−C, NF−C, ε, andrOPT. The numer...