Swirl Injector Research Articles

Study Of Wear In Chrome Plated Cylinder Liner In Two Stroke Marine Diesel Engine Lubricated By Hans Jensen Swirl Injection Principle

Over the years, the two-stroke crosshead diesel engine has been the preferred prime mover for large seagoing merchant vessels.The cylinder liner is manufactured from Grey cast iron alloyed with vanadium, titanium and molybdenum. Grey cast iron contains graphite which itself is a decent lubricant and the alloying elements of Grey cast iron help in resisting corrosion and improve its wear resistance at elevated temperatures.And, this cylinder liner, usually, is not chrome plated. Theideaof this work is to study the wearthat occurs inchrome plated cylinder liner and compare it with the non chrome plated cylinder liner when it is lubricatedby Hans Jensen swirl injection principle in the two- stroke marine diesel engine that is available in AMET Majesty cruise ship.Cylinder liner lubrication is one of the major aspects that greatly influences wear in the liner. Consequently, this ventureis also aimed at describing a clear picture of how cylinder liner lubrication is accomplished using Hans Jensen swirl injection principle on two-stroke marine diesel engines.

Research of liquid outflow from low-emission swirl injectors of a low-thrust liquid rocket engine

The paper justifies the possibility of using cold-flow test data to predict the combustion efficiency for a 13.34 N thruster combustion chamber. The results of modeling working liquid (water) flowing through hydraulic passages of single injection elements and coaxial swirl injectors are presented. We performed the simulation using the Reynolds-averaged Navier-Stokes equations that describe a turbulent flow of a two-phase non-compressible liquid. We used both one-velocity and two-velocity flow models. We modeled the turbulence by the BSL isotopic turbulence model on a computational block-structure grid. The computational grid consisted mostly of HEXA elements. The orientation of the elements coincided with the flow direction in the injector hydraulic channels, which improved the flow resolution accuracy in the boundary layer near the solid wall. We compared the results of calculation with the cold-flow test data. The use of the one-velocity flow model in the design area of a single injector and the two-velocity model in the design area of the mixing element yielded the results that agreed satisfactorily with the cold-flow data.

Effects of Swirl Bubble Injection on Mass Transfer and Hydrodynamics for Bubbly Flow Reactors: A Concept Paper

Bubble flow reactors (BFR) are commonly used for various industrial processes in the field of oil and gas production, pharmaceutical industries, biochemical and environmental engineering etc. The operation and performance of these reactors rely heavily on a range of hydrodynamic parameters; prominent among them are geometric configurations including gas injection geometry, operating conditions, mass transfer etc. A huge body of literature is available to describe the optimum design and performance of bubbly flow reactors with conventional bubble injection. Attempts were made to modify gas injection for improved efficiency of BFR's. However, here instead of modifying the geometry of the gas injection, an attempt has been made to generate swirl bubbles for gaining larger mass transfer between gas and liquid. Here an exceptionally well thought strategies have been used in our numerical simulations towards the design of swirl injection mechanism, whose paramount aspect is to inhibit the rotary liquid motion but facilitates the swirl movement for bubbles in nearly stationary liquid. Our comprehension here is that the swirl motion can strongly affect the performance of bubbly reactor by identifying the changes in hydrodynamic parameters as compared to the conventional bubbly flows. In order to achieve this bubbly flow, an experimental setup has been designed as well as computational fluid dynamic (CFD) code was used with to highlight a provision of swirl bubble injection by rotating the sparger plate.

Numerical investigation on liquid sheets interaction characteristics of liquid-liquid coaxial swirling jets in bipropellant thruster

Spray atomization process of a liquid-liquid coaxial swirl injector in bipropellant thruster has been investigated using volume of fluid (VOF) method coupled with large eddy simulation methodology. With fine grid resolution, detailed flow field of interacted liquid sheet has been captured and analyzed. For coaxial swirling jet, static pressure drop in the region between the liquid sheets makes two liquid sheets to approach each other and merge. A strong pressure, velocity and turbulent fluctuations are calculated near the contact position of two coaxial jets. Simulation results indicate that additional perturbations are generated due to strong radial and axial shear effects between coaxial jets. Observation of droplet formation process reveals that the Rayleigh mode instability dominates the breakup of the ligament. Droplet diameter and distribution have been investigated quantitatively. The mean diameter of the coaxial jets is between that of the inner and the outer jets. Compared with the individual swirling jets, wider size distributions of droplets are produced in the coaxial jets.

Application of Maximum Entropy Principle to Predict Droplet Size Distribution for Swirl Injectors

An existing droplets size distribution function, which was established based on the maximum entropy principle, momentum conservation law and energy conservation law, was used to predict the characteristics of spray field of a swirl injector with small geometry characteristics constant. The experimental system for spray characteristics was built, and an experimental study on the spray characteristics of swirl injectors with different geometries was conducted with phase Doppler particle analyzer (PDPA). It shows a coincidence between the experimental results and the spray characteristics predicted with the maximum entropy principle. The maximum entropy method can be a useful tool for the design of this type of injector.

The instability and droplet size distribution of liquid-liquid coaxial swirling spray: An experimental investigation

An experimental study is performed to study the effect of inner and outer injection pressure on spray characteristics and the detailed structure of interacted liquid sheets of a coaxial swirl injector. A high speed camera is used to visualize the transition merging process of the coaxial swirling liquid sheet. A laser reflection system is set up to analyze the wave frequency of liquid sheet. A Malvern RTSizer is used to measure the droplet size of the coaxial spray. It is found that the structure of the interacted spray is considerably different from the individual spray, the interaction between the inner and outer liquid film promoted the breakup. At the same injection pressure, the temporal instability of a liquid sheet does not change spatially. For both individual and coaxial spray, the wave frequency increase as the injection pressure increase. The individual inner spray is more unstable and easier to breakup. Furthermore, the relationship between the surface instability and the droplet size distribution of the coaxial liquid spray is investigated quantitatively. For both individual spray and coaxial sprays, the Sauter Mean Diameter (SMD) decrease as the inner injection pressure increase. The inner spray has a higher weighing factor that influences the SMD of the coaxial spray. For coaxial spray at low inner injection pressure, the liquid film thickness would be the dominate factor to the SMD.

Experimental study of the effect of tangential swirling injection on diffuser effectiveness

The experimental data on studying the tangential swirling injection effect on the effectiveness of a conical diffuser with an aperture angle of 18° and the expansion ratio equal to four are presented. It has been indicated that the effect becomes maximal for a given diffuser at an insignificant initial thickness of the boundary layer, when the injected jet swirling angle is 15° and the relative injection rate is 7.7%, as a result of which the pressure increases from 0.48 to 0.79 if the injected jet energy is taken into account.

A canonical geometry to study wall filming and atomization in pre-filming coaxial swirl injectors

A coaxial twin counter-rotating air swirl prefilming injector with necessary optical access, is developed to visualize and quantify its internal fluid dynamics. This research injector consists of a simplex nozzle arranged at the center of two coaxial counter-rotating radial air flow swirlers, and two transparent coaxial tubes are attached, one each to the primary and secondary air swirl paths. Spray from the simplex nozzle is swirled by the primary air and impinges on the inner tube—the prefilmer, undergoes filming, and convects to the tube tip to form a liquid rim, which is sheared by the counter-rotating swirl into finer droplets. Stage-wise phase Doppler particle analyzer measurements indicate the final spray to be much finer than the simplex nozzle spray after undergoing the above processes. Time resolved laser induced fluorescence (TR-LIF) imaging techniques are applied to visualize the wall filming and primary atomization inside the injector. The simplex nozzle spray velocity under the influence of air swirl flow is measured using stereo-particle image velocimetry. The precessing vortex core from the primary swirl imparts a precessing motion to the simplex spray, which in turn induces a non-uniform filming on the prefilmer. The droplet impingement on the prefilmer leads to splashing and crater formation on the surface. The crater size distribution is obtained and compared to the droplet size of the injector spray before impingement. The film thickness variation on the prefilmer surface and the rim thickness are estimated from planar LIF experiments along with a long distance microscope. The thickness of the liquid rim is identified as a major factor in determining the final droplet size at the injector exit. These are correlated to SMD at the injector exit at different air flow rates.

Stability of a confined swirling annular liquid layer with heat and mass transfer

A linear temporal stability of confined swirling annular liquid layers involving heat and mass transfer at the gas–liquid interface is presented in this paper. A normal-mode stability analysis that includes the effect of both swirling and heat transfer is performed. The flow in a gas-center coaxial swirl injector gives rise to the flow configuration explored in this work. The effects of various non-dimensional parameters on the instability of the flow are discussed. The heat transfer at the interface has been characterized by introducing a heat flux ratio between the conduction heat flux and the evaporation heat flux. The heat and mass transfer at the interface are found to destabilize the flow. Increasing confinement destabilizes the flow, which is opposite to the condition without heat and mass transfer.

Combustion and exhaust emission characteristics of low swirl injector

The present experimental study aims to investigate the combustion and emission characteristics of the flow through a low swirl injector (LSI). An experimental study was carried out on the flame structure, the temperature distribution and the exhaust emission of low swirl pre-mixed combustion under the condition of different swirl number and different fuel composition. In order to qualitatively analyze the flame structure, the velocity distribution of the non-reacting flow through the LSI was measured using the particle image velocimetry (PIV) technique. Experimental results indicated that: (i) the LSI can generate a blue lift-off “W” type flame which consists of four clusters of flames connected together and holds up a long yellow pulsating flame, (ii) the blue flame structure converts the “W” type flame into the “broom” type flame and the distance between the front of the flame and the nozzle shortens with increasing swirl number, (iii) there exist high temperature region flanked by two peaks on the temperature profiles in the blue flame while uniform higher temperature in yellow pulsating flame, (iv) the NOx and CO emission level of the LSI mainly depends on the gas composition and thermal load.

Numerical simulation of the internal flow of swirl atomizer under ambient pressure

This paper presents the simulation study of internal flow of open-end swirl injectors under steady and oscillating ambient pressures. A two-dimensional swirl axisymmetric model based on the volume of fluid method was developed to study the effect of ambient pressure on the internal flow of open-end swirl injectors. The response of injector flow to the ambient pressure oscillation was investigated by superimposing periodical oscillation of ambient pressure at the spout outlet. The results show that the variation of ambient pressure affects the liquid phase volumetric fraction within the gas–liquid shear layer. The spray angle near the wall remains constant independent of the ambient pressure. The velocity distribution on different axial sections rarely varies with ambient pressure. When the ambient pressure oscillated, the ambient pressure oscillation would cause the flow rate oscillation at the spout. The phase delay between the flow rate oscillation at spout and the ambient pressure oscillation is proportional to the oscillation frequency.

Mixing Characteristics of Kerosene-Lox in a Swirl Injector at 100 bar

The The turbulent mixing characteristics of Kerosene-LOx in a coaxial swirl injector 100 bar have been numerically investigated. Turbulent model is based on large eddy simulation with real-fluid transport and thermodynamics. The effects of equation of state (EOS), chamber pressure are evaluated in a point of the mixing efficiency and pressure fluctuations. The dominant frequency is same as the hairpin vortex shedding frequency generated by film wave at the LOx post.

Urea-SCR용 스월 인젝터의 니들 리프트 형상에 따른 유동특성에 대한 연구

Urea-SCR용 스월 인젝터의 니들 리프트 형상에 따른 유동특성에 대한 연구

Application of maximum entropy principle for estimation of droplet-size distribution using internal flow analysis of a swirl injector

The maximum entropy principle is one of the first methods, which have been used to predict droplet size and velocity distributions of liquid sprays. Due to some drawbacks in this model, the predicted results do not match well with the experimental data. This paper presents a different approach for improving the maximum entropy principle model. It is suggested to improve the available energy source in the maximum entropy principle model equation by numerical solution of flow inside the injector based on the computational fluid dynamics technique. This will enhance the calculation accuracy of the turbulent kinetic energy of the output spray. Application of this procedure enhances the model predictions. The liquid sheet properties resulted from the analysis are also applied for calculation of the momentum source in the maximum entropy principle model. The proposed model is applied to predict the droplet size distribution of a hollow-cone spray formed by a swirl injector. The results show a better agreement with the available experimental data than the results of prior models.

Coherent structures in a swirl injector at Re = 4800 by nonlinear simulations and linear global modes

The large-scale coherent motions in a realistic swirl fuel-injector geometry are analysed by direct numerical simulations (DNS), proper orthogonal decomposition (POD), and linear global modes. The aim is to identify the origin of instability in this turbulent flow in a complex internal geometry. The flow field in the nonlinear simulation is highly turbulent, but with a distinguishable coherent structure: the precessing vortex core (a spiralling mode). The most energetic POD mode pair is identified as the precessing vortex core. By analysing the fast Fourier transform (FFT) of the time coefficients of the POD modes, we conclude that the first four POD modes contain the coherent fluctuations. The remaining POD modes (incoherent fluctuations) are used to form a turbulent viscosity field, using the Newtonian eddy model. The turbulence sets in from convective shear layer instabilities even before the nonlinear flow reaches the other end of the domain, indicating that equilibrium solutions of the Navier–Stokes are never observed. Linear global modes are computed around the mean flow from DNS, applying the turbulent viscosity extracted from POD modes. A slightly stable discrete $m=1$ eigenmode is found, well separated from the continuous spectrum, in very good agreement with the POD mode shape and frequency. The structural sensitivity of the precessing vortex core is located upstream of the central recirculation zone, identifying it as a spiral vortex breakdown instability in the nozzle. Furthermore, the structural sensitivity indicates that the dominant instability mechanism is the Kelvin–Helmholtz instability at the inflection point forming near vortex breakdown. Adjoint modes are strong in the shear layer along the whole extent of the nozzle, showing that the optimal initial condition for the global mode is localized in the shear layer. We analyse the qualitative influence of turbulent dissipation in the stability problem (eddy viscosity) on the eigenmodes by comparing them to eigenmodes computed without eddy viscosity. The results show that the eddy viscosity improves the complex frequency and shape of global modes around the fuel-injector mean flow, while a qualitative wavemaker position can be obtained with or without turbulent dissipation, in agreement with previous studies. This study shows how sensitivity analysis can identify which parts of the flow in a complex geometry need to be altered in order to change its hydrodynamic stability characteristics.

Numerical analysis of combustion characteristics of hybrid rocket motor with multi-section swirl injection

This paper is aimed to analyse the combustion characteristics of hybrid rocket motor with multi-section swirl injection by simulating the combustion flow field. Numerical combustion flow field and combustion performance parameters are obtained through three-dimensional numerical simulations based on a steady numerical model proposed in this paper. The hybrid rocket motor adopts 98% hydrogen peroxide and polyethylene as the propellants. Multiple injection sections are set along the axis of the solid fuel grain, and the oxidizer enters the combustion chamber by means of tangential injection via the injector ports in the injection sections. Simulation results indicate that the combustion flow field structure of the hybrid rocket motor could be improved by multi-section swirl injection method. The transformation of the combustion flow field can greatly increase the fuel regression rate and the combustion efficiency. The average fuel regression rate of the motor with multi-section swirl injection is improved by 8.37times compared with that of the motor with conventional head-end irrotational injection. The combustion efficiency is increased to 95.73%. Besides, the simulation results also indicate that (1) the additional injection sections can increase the fuel regression rate and the combustion efficiency; (2) the upstream offset of the injection sections reduces the combustion efficiency; and (3) the fuel regression rate and the combustion efficiency decrease with the reduction of the number of injector ports in each injection section.

Dynamic characteristics of a cryogenic swirl flow under supercritical conditions

The dynamic characteristics of a cryogenic swirl flow under supercritical conditions were experimentally investigated using a mode decomposition method. Cryogenic liquid nitrogen was injected into a high-pressure chamber through a simplex swirl injector under subcritical to supercritical conditions of nitrogen. High-speed photography with backlight imaging was used to obtain images of the temporally changing flow. The set of images was analyzed by proper orthogonal decomposition (POD) technique. Superposed instability structures and vortex ring structures were found in the instantaneous flow image. The spray angle decreased under supercritical conditions because of the unusual phase change of the injectant inside the injector. Two kinds of modes were deduced by a POD analysis of the flow images. The analysis showed that two types of modes exist: a symmetric/tilted ring-shaped mode and an anti-symmetric-shaped mode. The Kelvin–Helmholtz instability mechanism generated the symmetric mode. The anti-symmetric structure was created by helical instability, which was generated by the instability of the liquid film inside the injector under subcritical conditions. However, under supercritical conditions, the precessing vortex core in the central toroidal recirculation zone determined the unstable behavior of the flow. A spatial and temporal analysis of the POD modes supported this explanation for the instability. Meanwhile, the spatial characteristics of the coherent structures became similar in the downstream region or under supercritical conditions, which implicates the strong influence of the state of the injectant in flow behavior.

Dynamic Characteristics of Open-Type Swirl Injector with Varying Geometry

Combustion instabilities in a liquid rocket engine are generated by coupling between the heat release oscillations and the acoustic pressure oscillations in the combustion chamber. These instabilities from the combustion chamber can affect the injector and the feed line, which are in front of the combustion chamber. These oscillation transfers could influence the combustion instability in liquid rocket engines. A properly designed injector can be used to prevent these transfers and suppress combustion instability. For this reason, the dynamic characteristics of the injectors must be studied. Open-type swirl injectors were designed to investigate the dynamic characteristics through experimental study. The injectors were designed with replaceable parts to change the swirl chamber length, swirl chamber diameter, tangential entry number, and manifold diameter. A hydrodynamic mechanical pulsator that produces pressure oscillations in the feed line was installed in front of the manifold of the open-type swirl injector. The pressure in the manifold, the liquid film thickness, and the pressure at the exit of the open-type swirl injector were measured to understand the dynamic characteristics of the open-type swirl injector. As a result, the open-type swirl injector’s response characteristics to pressure fluctuation inputs with different geometries were obtained. The tendencies of the output parameters acquired in the study could be used to adjust the injector design to suppress combustion instability in liquid rocket engines.

Swirl Injection Effects on Hybrid Rocket Motors

In the last decades, hybrid rocket engines have been increasingly studied and used in space vehicles. However, the low regression rates and specific impulses still represent major drawbacks to this technology. The objective of this study was to quantify the relative improvement of regression rate values with the use of a swirling flow injector in comparison to an axial injector. Seven tests were conducted with axial injection and seven with swirl injection. Regression rate results were compared, and it was found that swirl injection improved regression rates in 50% for mass fluxes higher than 45 kg∙s -1 ∙m -2 . It was possible to see radiation, kinetic and diffusion theory on the logarithmic plot of regression rate per oxidizer flux yielded by both injectors. A strong agreement with experimental findings of regression rates in the literature parameters is reported.

Effect of Slot Injection and Effusion Array on the Liner Heat Transfer Coefficient of a Scaled Lean-Burn Combustor With Representative Swirling Flow

International standards regarding polluting emissions from civil aircraft engines are becoming gradually even more stringent. Nowadays, the most prominent way to meet the target of reducing NOx emissions in modern aero-engine combustors is represented by lean-burn technology. Swirl injectors are usually employed to provide the dominant flame stabilization mechanism coupled to high-efficiency fuel atomization solutions. These systems generate very complex flow structures, such as recirculations, vortex breakdown, and processing vortex core, which affect the distribution and therefore the estimation of heat loads on the gas side of the liner as well as the interaction with the cooling system flows. The main purpose of the present work is to provide detailed measurements of heat transfer coefficient (HTC) on the gas side of a scaled combustor liner highlighting the impact of the cooling flows injected through a slot system and an effusion array. Furthermore, for a deeper understanding of the interaction phenomena between gas and cooling flows, a standard two-dimensional (2D) particle image velocimetry (PIV) technique has been employed to characterize the combustor flow field. The experimental arrangement has been developed within EU project LEMCOTEC and consists of a nonreactive three sectors planar rig installed in an open-loop wind tunnel. Three swirlers, replicating the real geometry of a GE Avio partially evaporated and rapid mixing (PERM) injector technology, are used to achieve representative swirled flow conditions in the test section. The effusion geometry is composed by a staggered array of 1236 circular holes with an inclination of 30 deg, while the slot exit has a constant height of 5 mm. The experimental campaign has been carried out using a thermochromic liquid crystals (TLCs) steady-state technique with a thin Inconel heating foil and imposing several cooling flow conditions in terms of slot coolant consumption and effusion pressure drop. A data reduction procedure has been developed to take into account the nonuniform heat generation and the heat loss across the liner plate. Results in terms of 2D maps and averaged distributions of HTC have been supported by flow field measurements with 2D PIV technique focussed on the corner recirculation region.