Improvements in Analyzing High-Speed Fuel/Air Mixing Problems Using Scalar Fluctuation Modeling

2008 ◽  
Author(s):  
Stephen Mattick ◽  
Kevin Brinckman ◽  
Sanford Dash ◽  
Z. Liu
Keyword(s):  
High Speed ◽  
Air Mixing ◽  
Scalar Fluctuation

The Role of Porous Media in Homogenization of High Pressure Diesel Fuel Spray Combustion

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Navid Shahangian ◽  
Damon Honnery ◽  
Jamil Ghojel
Keyword(s):  
High Pressure ◽  
Porous Media ◽  
High Speed ◽  
Fuel Spray ◽  
Compression Ignition Engines ◽  
System Pressure ◽  
Novel Approach ◽  
Air Mixing ◽  
The Media

Interest is growing in the benefits of homogeneous charge compression ignition engines. In this paper, we investigate a novel approach to the development of a homogenous charge-like environment through the use of porous media. The primary purpose of the media is to enhance the spread as well as the evaporation process of the high pressure fuel spray to achieve charge homogenization. In this paper, we show through high speed visualizations of both cold and hot spray events, how porous media interactions can give rise to greater fuel air mixing and what role system pressure and temperature plays in further enhancing this process.

scholarly journals Design and Commissioning of a Combustor Simulator Combining Swirl and Entropy Wave Generation

2020 ◽  
Vol 5 (4) ◽  
pp. 27
Author(s):  
Andrea Notaristefano ◽  
Paolo Gaetani
Keyword(s):  
High Speed ◽  
Turbulent Flame ◽  
Extreme Condition ◽  
The Novel ◽  
Combustion Chambers ◽  
Unsteady Temperature ◽  
Speed Test ◽  
Air Mixing ◽  
Large Heat ◽  
Turbine Design

Modern aero-engine combustion chambers burn a lean and premixed mixture, generating a turbulent flame which involves large heat-release fluctuations, thus producing unsteady temperature phenomena commonly referred to as entropy waves (EWs). Furthermore, to enhance the fuel air mixing, combustion air is swirled, leading to vorticity disturbances. These instabilities represent one of the biggest challenges in gas turbine design. In this paper, the design and testing of a novel entropy wave generator (EWG) equipped with a swirler generator (SG) are described. The novel EWG will be used in future works on the high-speed test rig at Politecnico di Milano to study the combustor–turbine interaction. The paper shows the process of the EWG geometry and layout. The EWG is able to produce an engine-representative EW, the extreme condition is at the maximum frequency of 110 Hz, a peak-to-valley temperature value of 20 °C and swirling angles of ±25° are measured. By virtue of these results, the proposed system outperforms other EWG devices documented in the literature. Furthermore, the addition of a swirling generator makes this device one of a kind.

Partially-Averaged Navier–Stokes Simulations of High-Speed Mixing Environment

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Ravichandra Srinivasan ◽  
Sharath S. Girimaji
Keyword(s):  
High Speed ◽  
Cavity Flow ◽  
Velocity Fields ◽  
Navier Stokes ◽  
High Fidelity ◽  
Variable Resolution ◽  
Air Mixing

Accurate simulation of the fuel-air mixing environment is crucial for high-fidelity scramjet calculations. We compute the velocity fields of jet into supersonic freestream flow and cavity flow typical of scramjet flame-holding applications at different scale resolutions using the partially-averaged Navier–Stokes (PANS) method. We present a sequence of variable resolution computations to demonstrate the potential of PANS method for high-speed mixing environment calculations.

Scaling liquid penetration in evaporating sprays for different size diesel engines

2019 ◽  
Vol 21 (9) ◽  
pp. 1662-1677 ◽  
Author(s):  
Xinyi Zhou ◽  
Tie Li ◽  
Yijie Wei ◽  
Ning Wang
Keyword(s):  
Diesel Engine ◽  
Diesel Engines ◽  
High Speed ◽  
Scaling Laws ◽  
Fuel Injection ◽  
Pollutant Emissions ◽  
Liquid Penetration ◽  
Spray Characteristics ◽  
Penetration Length ◽  
Air Mixing

Scaled model experiments can greatly reduce the cost, time and energy consumption in diesel engine development, and the similarity of spray characteristics has a primary effect on the overall scaling results of engine performance and pollutant emissions. However, although so far the similarity of spray characteristics under the non-evaporating condition has been studied to some extent, researches on scaling the evaporating sprays are still absent. The maximum liquid penetration length has a close relationship with the spray evaporation processes and is a key parameter in the design of diesel engine spray combustion system. In this article, the similarity of maximum liquid penetration length is theoretically derived based on the hypotheses that the spray evaporation processes in modern high-pressure common rail diesel engines are fuel–air mixing controlled and local interphase transport controlled, respectively. After verifying that the fuel injection rates are perfectly scaled, the similarity of maximum liquid penetration length in evaporating sprays is studied for three scaling laws using two nozzles with hole diameter of 0.11 and 0.14 mm through the high-speed diffused back-illumination method. Under the test conditions of different fuel injection pressures, ambient temperatures and densities, the lift-off law and speed law lead to a slightly increased maximum liquid penetration length, while the pressure law can well scale the maximum liquid penetration length. The experimental results are consistent with the theoretical analyses based on the hypothesis that the spray evaporation processes are fuel–air mixing controlled, indicating that the local interphase transports of energy, momentum and mass on droplet surface are not rate-controlled steps with respect to spray evaporation processes.

scholarly journals Inter-plume aerodynamics for gasoline spray collapse

2017 ◽  
Vol 19 (10) ◽  
pp. 1048-1067 ◽  
Author(s):  
Panos Sphicas ◽  
Lyle M Pickett ◽  
Scott A Skeen ◽  
Jonathan H Frank
Keyword(s):  
Ambient Temperature ◽  
High Speed ◽  
Direct Injection ◽  
Engine Performance ◽  
Operating Conditions ◽  
Momentum Exchange ◽  
Flow Recirculation ◽  
Plume Region ◽  
Image Velocimetry ◽  
Air Mixing

The collapse or merging of individual plumes of direct-injection gasoline injectors is of fundamental importance to engine performance because of its impact on fuel–air mixing. However, the mechanisms of spray collapse are not fully understood and are difficult to predict. The purpose of this work is to study the aerodynamics in the inter-spray region, which can potentially lead to plume collapse. High-speed (100 kHz) particle image velocimetry is applied along a plane between plumes to observe the full temporal evolution of plume interaction and potential collapse, resolved for individual injection events. Supporting information along a line of sight is obtained using simultaneous diffused back illumination and Mie-scatter techniques. Experiments are performed under simulated engine conditions using a symmetric eight-hole injector in a high-temperature, high-pressure vessel at the “Spray G” operating conditions of the engine combustion network. Indicators of plume interaction and collapse include changes in counter-flow recirculation of ambient gas toward the injector along the axis of the injector or in the inter-plume region between plumes. The effect of ambient temperature and gas density on the inter-plume aerodynamics and the subsequent plume collapse are assessed. Increasing ambient temperature or density, with enhanced vaporization and momentum exchange, accelerates the plume interaction. Plume direction progressively shifts toward the injector axis with time, demonstrating that the plume interaction and collapse are inherently transient.

Mixture Quality of a Vortex Generator Premixer and Alternative Premixer Designs in the Auto-Ignition Regime of Hydrogen Air Flames

2017 ◽  
Author(s):  
Stefan Bauer ◽  
Simon Bäßler ◽  
Balbina Hampel ◽  
Christoph Hirsch ◽  
Thomas Sattelmayer
Keyword(s):  
Gas Turbines ◽  
High Speed ◽  
Current Knowledge ◽  
Flux Ratio ◽  
Vortex Generator ◽  
Inlet Temperature ◽  
Air Temperatures ◽  
Auto Ignition ◽  
Air Mixing ◽  
Thermodynamic Conditions

The application of vortex generator premixers (VGPs) is particularly challenging for highly reactive fuels in recuperated gas turbines, because high combustor inlet temperature leads to a potential risk of premature self-ignition and flame flashback. As current knowledge does not extend to the temperature range far above the self-ignition temperature, an experimental investigation of the operational limits of VGPs is conducted at the Thermodynamics Institute of the Technical University of Munich. The study is particularly focused on highly reactive fuels and the thermodynamic conditions present in recuperated gas turbines with pressure ratios of 4–5. The present study is focuses on fuel-air mixing at the corresponding high air temperatures. A fuel-air mixing device is required to achieve sufficient mixing quality without excessive premixer length. Vortex generators are known to be effective in augmenting the distribution of fuel injected from the tube wall over the cross section of the tube. In the range of typical gas turbine combustor inlet temperatures, the performance of VGPs has already been investigated for methane as well as for hydrogen-methane blends. The limits of operating a VGP under auto-ignition relevant conditions were presented in a previous study. In this study, the VGP’s mixture quality under these conditions is experimentally investigated. For this purpose, the existing test rig has been modified to conduct high speed PIV and MixPIV measurements. Measurements at different positions inside and downstream of the injector have been performed. Two other mixer types in addition to the VGP are investigated to determine the influence of mixture quality on auto-ignition behavior in a future study and to validate MixPIV measurements. The influence of the momentum flux ratio on mixture quality is presented for the three mixer types. Comparison shows that the VGP exhibits significantly better mixture homogeneity at the mixer exit than do the two other mixer types.

Evaluation of Two Measurement Techniques to Quantify Fuel–Air Mixing of a Gas Turbine Premixer at Atmospheric Conditions

2015 ◽  
Vol 138 (5) ◽  
Author(s):  
Wessam Estefanos ◽  
Mahmoud Hamza ◽  
Umesh Bhayaraju ◽  
San-Mou Jeng
Keyword(s):  
Reynolds Number ◽  
Momentum Flux ◽  
High Speed ◽  
Measurement Techniques ◽  
Flux Ratio ◽  
High Temporal Resolution ◽  
Atmospheric Conditions ◽  
High Concentration ◽  
Fuel Mass ◽  
Air Mixing

In the present study, two measurement techniques are adopted to evaluate the fuel–air mixing under atmospheric conditions using an industrial fuel–air premixer. These techniques are CO2 mixing and planar laser induced fluorescence (PLIF) in water. In these techniques, CO2 and fluorescent dye are injected as fuel simulants. CO2 measurements are used to validate PLIF in water. In the CO2 technique, CO2 concentrations are converted to fuel mass fractions, whereas in the PLIF technique, a modified post processing method is used to convert the LIF signal into fuel mass fraction. The experiments are conducted at the same Reynolds number and momentum flux ratio for two injection strategies. To study the effect of the flow aerodynamics on the mixing results, high-speed particle image velocimetry (PIV) measurements are conducted in water at the same Reynolds number. A comparison of fuel concentrations measured with the CO2 and PLIF techniques shows good quantitative agreement at all momentum flux ratios. However, deviations between the two techniques are observed at locations of high fuel concentration gradients. The unsteady mixing is evaluated using the PLIF technique with high temporal resolution. Analysis of PIV and PLIF data shows that unsteady mixing is lower at regions of high fluctuations in velocity. Moreover, it is found that there is high unsteady mixing at locations of high concentration gradient.

Macro Characteristics of the Spray from Intersecting Hole Nozzles

2011 ◽  
Vol 110-116 ◽  
pp. 343-349
Author(s):  
Xian Yin Leng ◽  
Kun Peng Qi ◽  
Wu Qiang Long ◽  
Sheng Li Wei
Keyword(s):  
High Speed ◽  
Internal Combustion Engines ◽  
Ambient Pressure ◽  
Direct Injection ◽  
High Speed Photography ◽  
Spray Penetration ◽  
Exit Surface ◽  
Front Angle ◽  
Ambient Room Temperature ◽  
Air Mixing

The formation method of the intersecting hole nozzle, each hole is formed by the converging of two or more child holes, is proposed, for the purpose of accelerating the fuel-air mixing process of direct injection internal combustion engines. In order to examine the macro characteristics of intersecting hole nozzles, three single-orifice intersecting hole nozzles, with the intersecting point of the axes of child holes locating inside, outside, and right at the exit surface, were manufactured. And high speed photography was employed to visualize, thus to quantify the angle and penetration of, the spray from these intersecting hole nozzles in a vessel under ambient room temperature and pressure of 0.1 to 2.0 MPa. The experimental results showed that the spray from intersecting hole nozzles were fan-shaped, which were beneficial for prompting the fuel-air mixing. Particularly, when the intersecting points of the axes of child holes locate right at the exit surface, the longest spray penetration was obtained, and the spray front angle is slightly smaller than side angle. While the intersecting points of the axes of child holes locate inside or outside the exit surface, the spray penetration is shorter, and the spray front angles are extremely larger than side angles under pressure of 0.1 to 2.0 MPa. With the rising of ambient pressure, the differences between front angle and side angle of all the three intersecting hole nozzles become smaller in different degrees.

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