Simulations of Non-Reacting Transient N-Dodecane Spray in a High-Pressure Combustion Vessel

2015 ◽  
Author(s):  
Rohit Saini ◽  
Ashoke De
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Fuel Injection ◽  
Turbulence Models ◽  
Air Entrainment ◽  
Chemical Mechanism ◽  
Injection Velocity ◽  
Computational Domain ◽  
Diffusion Controlled ◽  
Secondary Breakup

In many combustion systems, fuel atomization and the spray breakup process play an important role in determining combustion characteristics and emission formation. Due to the ever-rising need for better fuel efficiency and lower emissions, the development of a fundamental understanding of its process is essential and remains a challenging task. The Spray-A case of the Engine Combustion Network (ECN) is considered in the study, in which liquid n-Dodecane (Spray-A) is injected at 1500 bar through a nozzle diameter of 90 μm into a constant volume vessel with an ambient density of 22.8 kg / m3 and an ambient temperature of 900 K. The unsteady Reynolds averaged Navier-Stokes (URANS) in conjunction with k-ε turbulence model is used to investigate the flow physics in a two-dimensional axisymmetric computational domain. A reduced chemical mechanism from Wang et al. [1] with 100 species and 432 reactions is invoked to represent the kinetics. The gas and liquid phases are modeled using Eulerian-Lagrangian coupled approach. The present model is validated with the experimental data as well as computational data of Pei et al. [2]. Initially, the effects of various turbulence models with modified constants are examined without introducing the breakup phenomena in the computational physics. Later on, primary and secondary breakup processes of the liquid fuel are taken into account. In the present study, we examine the effects of secondary breakup modeling on the spray under high-pressure conditions using different breakup models, including Wave, Kelvin-Helmholtz and Rayleigh-Taylor (KH-RT) and Stochastic Secondary Droplet (SSD) models. It has been observed that KH-RT model is more dominant in such high-pressure sprays and predict physics more accurately as compared to other models. The dominance of convection as well as diffusion controlled vaporization model is also realized over the diffusion controlled vaporization model. The investigations at different fuel injection pressures are also modeled and validated with the experimental data [3]. The results strongly suggest that applying high-pressure, leads to high injection velocity and momentum which enhances the air entrainment near the injector region and the mixing process.

Flow Field and Hot Streak Migration Through a High Pressure Cooled Vanes With Representative Lean Burn Combustor Outflow

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Tommaso Bacci ◽  
Tommaso Lenzi ◽  
Alessio Picchi ◽  
Lorenzo Mazzei ◽  
Bruno Facchini
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Flow Field ◽  
Fuel Injection ◽  
Leading Edge ◽  
Flame Stabilization ◽  
Lean Burn ◽  
Aero Engine ◽  
University Of Florence ◽  
Hot Streak

Modern lean burn aero-engine combustors make use of relevant swirl degrees for flame stabilization. Moreover, important temperature distortions are generated, in tangential and radial directions, due to discrete fuel injection and liner cooling flows respectively. At the same time, more efficient devices are employed for liner cooling and a less intense mixing with the mainstream occurs. As a result, aggressive swirl fields, high turbulence intensities, and strong hot streaks are achieved at the turbine inlet. In order to understand combustor-turbine flow field interactions, it is mandatory to collect reliable experimental data at representative flow conditions. While the separated effects of temperature, swirl, and turbulence on the first turbine stage have been widely investigated, reduced experimental data is available when it comes to consider all these factors together.In this perspective, an annular three-sector combustor simulator with fully cooled high pressure vanes has been designed and installed at the THT Lab of University of Florence. The test rig is equipped with three axial swirlers, effusion cooled liners, and six film cooled high pressure vanes passages, for a vortex-to-vane count ratio of 1:2. The relative clocking position between swirlers and vanes has been chosen in order to have the leading edge of the central NGV aligned with the central swirler. In order to generate representative conditions, a heated mainstream passes though the axial swirlers of the combustor simulator, while the effusion cooled liners are fed by air at ambient temperature. The resulting flow field exiting from the combustor simulator and approaching the cooled vane can be considered representative of a modern Lean Burn aero engine combustor with swirl angles above ±50 deg, turbulence intensities up to about 28% and maximum-to-minimum temperature ratio of about 1.25. With the final aim of investigating the hot streaks evolution through the cooled high pressure vane, the mean aerothermal field (temperature, pressure, and velocity fields) has been evaluated by means of a five-hole probe equipped with a thermocouple and traversed upstream and downstream of the NGV cascade.

Computational Study of Fuel Injection in a Large-Bore Gas Engine

2003 ◽  
Author(s):  
Snehaunshu Chowdhury ◽  
Razi Nalim ◽  
Thomas M. Sine
Keyword(s):  
High Pressure ◽  
Fuel Injection ◽  
Computational Study ◽  
Turbulence Models ◽  
Fuel Flow ◽  
Air Mixing ◽  
Instantaneous Pressure ◽  
Combustion Processes ◽  
High Pressure Injection ◽  
Piston Position

Emission controls in stationary gas engines have required significant modifications to the fuel injection and combustion processes. One approach has been the use of high-pressure fuel injection to improve fuel-air mixing. The objective of this study is to simulate numerically the injection of gaseous fuel at high pressure in a large-bore two-stroke engine. Existing combustion chamber geometry is modeled together with proposed valve geometry. The StarCD® fluid dynamics code is used for the simulations, using appropriate turbulence models. High-pressure injection of up to 500 psig methane into cylinder air initially at 25 psig is simulated with the valve opened instantaneously and piston position frozen at the 60 degrees ABDC position. Fuel flow rate across the valve throat varies with the instantaneous pressure but attains a steady state in approximately 22 ms. As expected with the throat shape and pressures, the flow becomes supersonic past the choked valve gap, but returns to a subsonic state upon deflection by a shroud that successfully directs the flow more centrally. This indicates the need for careful shroud design to direct the flow without significant deceleration. Pressures below 300 psig were not effective with the proposed valve geometry. A persistent re-circulation zone is observed immediately below the valve, where it does not help promote mixing.

Numerical Simulation of the Dynamic Response of a Diesel Fuel Injector Using CFD

2005 ◽  
Author(s):  
Yong Yi ◽  
Aleksandra Egelja ◽  
Clement J. Sung
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Dynamic Response ◽  
Diesel Fuel ◽  
Fuel Injection ◽  
Injection System ◽  
Fuel Injection System ◽  
Fuel Injector ◽  
Diesel Fuel Injection ◽  
Very High

The development of a very high pressure diesel fuel injection system has been one of the key solutions to improve engine performance and to reduce emissions. The diesel fuel management in the injector directly affects how the fuel spray is delivered to the combustion chamber, and therefore affects the mixing, combustion and the pollutants formation. To design such a very high pressure diesel fuel injection system, an advanced CFD tool to predict the complex flow in the fuel injection system is required in the robust design process. In this paper, a novel 3D CFD dynamic mesh with cavitation model is developed to simulate the dynamic response of the needle motion of a diesel fuel injector corresponding to high common rail pressure and other dimensional design variables, coupling with the imbalance of the spring force and the flow force (pressure plus viscous force). A mixture model is used for cavitation resulting from high speed flow in fuel injector. Due to the lack of experimental data, the model presented in this paper is only validated by a limited set of experimental data. Required meshing strategy is also discussed in the paper.

Analysis of the effect of variations in fuel line pressure in high-speed direct injection diesel engines, with high-pressure common rail fuel injection systems on heat release, cylinder pressure, performance, and NOx emissions

2005 ◽  
Vol 219 (3) ◽  
pp. 413-422 ◽  
Author(s):  
F J Wallace ◽  
J G Hawley
Keyword(s):  
High Pressure ◽  
Heat Release ◽  
Diesel Engines ◽  
High Speed ◽  
Fuel Injection ◽  
Direct Injection ◽  
Common Rail ◽  
Injection Velocity ◽  
Engine Simulation ◽  
High Pressure Common Rail

This paper is a further development of work previously reported on a wholly analytical approach to heat release modelling and is applicable to high-speed direct injection (HSDI) diesel engines operating with high-pressure common rail fuel injection systems under conditions of predominantly mixing-controlled combustion. The key variable in this treatment is the fuel preparation or combustion rate factor WH which, in conjunction with the primary injection variables, i.e. rail pressure, injection velocity and duration, defines the shape and amplitude of the heat release curve. It was shown in a previous paper that by expressing the fuel preparation rate factor WH as a function of time rather than crank angle, i.e. WHt instead of WHθ, the former can be presented as a nearly linear function of the square of injection velocity, i.e. WHt is directly proportional to the kinetic energy of the injected fuel spray, the latter evidently being the primary influence on the rate of the fuel-air mixing process. The analytical treatment developed in the authors' previous paper then allows heat release rates in the engine, dQ/dθ, to be calculated over a wide range of engine speeds and loads, with the aid of the existing engine simulation code ODES (Otto diesel engine simulation) to predict the associated engine performance and emissions, without resorting to further engine testing.

Flow Field and Hot Streak Migration Through High Pressure Cooled Vanes With Representative Lean Burn Combustor Outflow

2018 ◽  
Author(s):  
T. Bacci ◽  
T. Lenzi ◽  
A. Picchi ◽  
L. Mazzei ◽  
B. Facchini
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Flow Field ◽  
Fuel Injection ◽  
Leading Edge ◽  
Flame Stabilization ◽  
Lean Burn ◽  
Aero Engine ◽  
University Of Florence ◽  
Hot Streak

Modern lean burn aero-engine combustors make use of relevant swirl degrees for flame stabilization. Moreover important temperature distortions are generated, in tangential and radial directions, due to discrete fuel injection and liner cooling flows respectively. At the same time, more efficient devices are employed for liner cooling and a less intense mixing with the mainstream occurs. As a result, aggressive swirl fields, high turbulence intensities and strong hot streaks are achieved at the turbine inlet. In order to understand combustor-turbine flow field interactions, it is mandatory to collect reliable experimental data at representative flow conditions. While the separated effects of temperature, swirl and turbulence on the first turbine stage have been widely investigated, reduced experimental data is available when it comes to consider all these factors together. In this perspective, an annular three-sector combustor simulator with fully cooled high pressure vanes has been designed and installed at the THT Lab of University of Florence. The test rig is equipped with three axial swirlers, effusion cooled liners and six film cooled high pressure vanes passages, for a vortex-to-vane count ratio of 1:2. The relative clocking position between swirlers and vanes has been chosen in order to have the leading edge of the central NGV aligned with the central swirler. In order to generate representative conditions, a heated mainstream passes though the axial swirlers of the combustor simulator, while the effusion cooled liners are fed by air at ambient temperature. The resulting flow field exiting from the combustor simulator and approaching the cooled vane can be considered representative of a modern Lean Burn aero engine combustor with swirl angles above ±50°, turbulence intensities up to about 28% and maximum-to-minimum temperature ratio of about 1.25. With the final aim of investigating the hot streaks evolution through the cooled high pressure vane, the mean aerothermal field (temperature, pressure and velocity fields) has been evaluated by means of a five hole probe equipped with a thermocouple and traversed upstream and downstream of the NGV cascade.

NUMERICAL INVESTIGATION OF INFLUENCE OF HEAT EXCHANGER СHANNEL CURVATURE ON HEAT TRANSFER

2016 ◽  
Vol 6 (4) ◽  
pp. 134-138
Author(s):  
Ekaterina N. MENYALKINA ◽  
Anna A. TSINAEVA
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Turbulence Models ◽  
Software Systems ◽  
Computational Domain ◽  
Tetrahedral Grids ◽  
Turn Radius ◽  
Account Heat

In this paper the infl uence of the curvature of the portion of the heat exchanger on heat exchange with the use of software systems Salome Meca and Code Saturne is numerically studied the verifi cation of the numerical model by comparing with experimental data of other researchers without taking into account heat exchange is made. The solution is held for an average fl ow rate equal to 11 m/s. To investigate the infl uence on heat transfer of the curvature of the channel carried out the construction of the computational domain in the form of the heat exchanger of the same length with diff erent turn radius. For discretization of the computational domain were used tetrahedral grids containing approximately 850 thousand of elements with local refi nement near the surface of the channel. As a result of simulation values of the fl ow temperature at the outlet of the channels are obtained. It is revealed that the design of heat exchanger channel, of course, aff ects the heat transfer, as well as data on the applicability of diff erent turbulence models for this type of task are collected.

Numerical and Experimental Investigation As Applied to Effects of Labyrinth-Type Casing Treatments on Performance of High-Loaded Compressor First Stage

2018 ◽  
Author(s):  
V. I. Mileshin ◽  
V. V. Zhdanov ◽  
A. M. Petrovitchev
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Pressure Ratio ◽  
Turbulence Models ◽  
Lower Efficiency ◽  
Stall Margin ◽  
Casing Treatment ◽  
Smooth Flow ◽  
Casing Treatments ◽  
Good Agreement

In connection with the development of a new family of high-pressure HPC with ultra-high pressure ratio and the number of stages 10–11, a special attention should be paid to the development of the first high-load stage, because compressor performance directly depends on its excellence. Despite the fact that the stage at nominal rotational speeds can have optimal performance, stall margins at intermediate rotational speeds can decrease because of a sizable IGV closure. One of the ways to increase stall margins is the use of labyrinth-type casing treatments. The Stage “A-1” studied in this work is a full-scale first stage in a six-stage high-pressure compressor (HPC) for a core demonstrator. The primary design task for the labyrinth-type casing treatment (CT) is to keep performance at design rotational speeds (n = 100%) or improve them, if possible, and increase stall margins at intermediate speeds (n = 70% and n = 80%). The labyrinth-type CT consisting of 3 circumferential grooves located above the middle of the blade chord projection is specially designed and manufactured for this stage. Our computations show that the use of the labyrinth-type CT leads to a shift of performance towards higher airflow and efficiency that is a good agreement with experimental data. An increase in stall margins without changes in efficiency is found by calculations, whereas the test, on the contrary, shows no influence on stall margins and an increase in efficiency by ∼1.5% (the same as at rated speeds). Both investigated turbulence models (SST and k-ε) do not provide good agreement with the experimental data. The SST model captures CT influence, but decreases stall margin. The k-ε model show agreement with the test in stall margin, but cannot capture CT influence. In addition, both models show lower efficiency compared with the experimental data. To verify the NUMECA Fine Turbo (version 11.1) mathematical model and numerical method, calculated and experimental characteristics of the Stage A-1 with a smooth flow passage and a labyrinth-type CT are compared. The NUMECA Autogrid 5 grid generator is used to build the grid.

An equilibrium phase spray model for high-pressure fuel injection and engine combustion simulations

2017 ◽  
Vol 20 (2) ◽  
pp. 203-215 ◽  
Author(s):  
Zongyu Yue ◽  
Rolf D Reitz
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Phase Equilibrium ◽  
Diesel Engine ◽  
Internal Combustion Engines ◽  
Fuel Injection ◽  
Equilibrium Phase ◽  
Experimental Studies ◽  
Operating Conditions ◽  
Engine Combustion

High-pressure fuel injection impacts mixture preparation, ignition and combustion in engines and other applications. Experimental studies have revealed the mixing-controlled and local phase equilibrium characteristics of liquid vaporization in high injection pressure diesel engine sprays. However, most computational fluid dynamics models for engine simulations spend much effort in solving for non-equilibrium spray processes. In this study, an equilibrium phase spray model is explored. The model is developed based on jet theory and a phase equilibrium assumption, without modeling drop breakup, collision and finite-rate interfacial vaporization processes. The proposed equilibrium phase spray model is validated extensively against experimental data in simulations of the engine combustion network Spray A and in an optical diesel engine. Predictions of liquid/vapor penetration, fuel mass fraction distribution, heat release rate and emission formation are all in good agreement with experimental data. In addition, good computational efficiency and grid-independency are also seen with the present equilibrium phase model. The examined operating conditions cover wide ranges that are relevant to internal combustion engines, which include ambient temperatures from 700 to 1400 K, ambient densities from 7.6 to 22.8 kg/m3 and injection pressures from 1200 to 1500 bar for diesel sprays.

Sign in / Sign up

Export Citation Format

Share Document