scholarly journals He misfire degree and its effects on combustion and pollutant formation of subsequent cycles: A study on a high speed gasoline engine

2021 ◽  
pp. 292-292
Author(s):  
Yangyang Chen ◽  
Qifei Jian ◽  
Banglin Deng ◽  
Kaihong Hou
Keyword(s):  
Flow Field ◽  
Flame Propagation ◽  
High Speed ◽  
Gasoline Engine ◽  
Working Process ◽  
No Emission ◽  
Pollutant Formation ◽  
Combustion Phase ◽  
Lower Temperature ◽  
Final Amount

Misfire has attracted lots of researcher?s attention as a common engine fault, but most researchers focus on misfire diagnosis. For motorcycle engines, misfire is more worth to investigate because of the more extensive operation windows. The misfire degree is detected by experiment and its effect mechanism on subsequent cycles is investigated through simulation. Its effect is analyzed through two aspects: 1) misfire cycle leaves about 10.8% fuels that participate in next cycle working process, leading to richer fuel/air mixture. But 13.8 % lower of in-cylinder peak pressure than normal scenario is observed. Then interaction between flame propagation and flow field is discussed. The effect of misfire on flow field intensity is small, but it changes flow field structure largely. This change evolves persistently during subsequent processes, superimposing the lower temperature brought by misfire of last cycle, resulting in slower flame propagation and thus lower thermal efficiency for misfire scenario. This impact can last 3-4 subsequent cycles until gradually fades away; 2) for pollutants formations, the NO emission is lower for misfire scenario due to the lower in-cylinder temperature, but HC emission is higher. Although higher CO is produced during main combustion phase for misfire scenario, it converts to CO2 more largely during post flame stage, resulting in almost the same final amount relative to normal scenario.

scholarly journals Simultaneous In-Cylinder Flow Measurement and Flame Imaging in a Realistic Operating Engine Environment Using High-Speed PIV

2019 ◽  
Vol 9 (13) ◽  
pp. 2678 ◽  
Author(s):  
Atsushi Nishiyama ◽  
Minh Khoi Le ◽  
Takashi Furui ◽  
Yuji Ikeda
Keyword(s):  
Flow Field ◽  
Flame Front ◽  
Flame Propagation ◽  
High Speed ◽  
Gasoline Engine ◽  
Fuel Injection ◽  
Front Propagation ◽  
Growth Direction ◽  
Flame Imaging ◽  
Cylinder Flow

Among multiple factors that affect the quality of combustion, the intricate and complex interaction between in-cylinder flow/turbulent field and flame propagation is one of the most important. In this study, true simultaneous, crank-angle resolved imaging of the flame front propagation and the measurement of flow-field was achieved by the application of high-speed Particle Image Velocimetry (PIV). The technique was successfully implemented to avoid problems commonly associated with PIV in a combustion environment, such as interferences and reflections, avoided thanks to a number of adjustments and arrangements. All experiments were carried out inside a single-cylinder optical gasoline engine operated at 1200 rpm, using port fuel injection (PFI) with stoichiometric mixtures. It was found that the global vortex location of the tumble motion heavily influences the flame growth direction as well as the flame shape, mainly due to the tumble-induced flow across the ignition source. The flame propagation also influences the flow-field such that the pre-ignition flow can be maintained and the flow of unburned region surrounding the flame front will be enhanced.

Visualization of Different Flashback Mechanisms for H2/CH4 Mixtures in a Variable-Swirl Burner

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Parisa Sayad ◽  
Alessandro Schönborn ◽  
Mao Li ◽  
Jens Klingmann
Keyword(s):  
Flow Field ◽  
Flame Propagation ◽  
Mass Flow ◽  
High Speed ◽  
Vortex Breakdown ◽  
Propagation Speed ◽  
Swirl Burner ◽  
Air Mass ◽  
Auto Ignition ◽  
Fuel Mixtures

Flame flashback from the combustion chamber to the premixing section is a major operability issue when using high H2 content fuels in lean premixed combustors. Depending on the flow-field in the combustor, flashback can be triggered by different mechanisms. In this work, three flashback mechanisms of H2/CH4 mixtures were visualized in an atmospheric variable-swirl burner using high speed OH* chemiluminescence imaging. The H2 mole fraction of the tested fuel mixtures varied between 0.1 and 0.9. The flow-field in the combustor was varied by changing the swirl number from 0.0 to 0.66 and the total air mass-flow rate from 75 to 200 SLPM (standard liters per minute). The following three types of flashback mechanism were observed: Flashback caused by combustion induced vortex breakdown (CIVB) occurred at swirl numbers ≥0.53 for all of the tested fuel mixtures. Flashback in the boundary layer (BL) and flame propagation in the premixing tube caused by auto-ignition were observed at low swirl numbers and low total air mass-flow rates. The temporal and spatial propagation of the flame in the optical section of the premixing tube during flashback was studied and flashback speed for different mechanisms was estimated. The flame propagation speed during flashback was significantly different for the different mechanisms.

Effect of Irradiation of the Extraction Mixture with 30% TBP in ISOPAR-M on the Lower Temperature Limit of Flame Propagation

2020 ◽  
Vol 62 (6) ◽  
pp. 723-729
Author(s):  
A. V. Rodin ◽  
I. V. Skvortsov ◽  
E. V. Belova ◽  
K. N. Dvoeglazov ◽  
B. F. Myasoedov
Keyword(s):  
Flame Propagation ◽  
Temperature Limit ◽  
Lower Temperature Limit ◽  
Lower Temperature ◽  
Extraction Mixture

scholarly journals Cross-Flow Tidal Turbines with Highly Flexible Blades—Experimental Flow Field Investigations at Strong Fluid–Structure Interactions

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 797
Author(s):  
Stefan Hoerner ◽  
Iring Kösters ◽  
Laure Vignal ◽  
Olivier Cleynen ◽  
Shokoofeh Abbaszadeh ◽  
...  
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Cross Flow ◽  
Speed Ratio ◽  
Fluid Structure Interactions ◽  
Dimensional Parameter ◽  
Fluid Structure ◽  
Passive Flow Control ◽  
Tidal Turbines ◽  
Tidal Turbine

Oscillating hydrofoils were installed in a water tunnel as a surrogate model for a hydrokinetic cross-flow tidal turbine, enabling the study of the effect of flexible blades on the performance of those devices with high ecological potential. The study focuses on a single tip-speed ratio (equal to 2), the key non-dimensional parameter describing the operating point, and solidity (equal to 1.5), quantifying the robustness of the turbine shape. Both parameters are standard values for cross-flow tidal turbines. Those lead to highly dynamic characteristics in the flow field dominated by dynamic stall. The flow field is investigated at the blade level using high-speed particle image velocimetry measurements. Strong fluid–structure interactions lead to significant structural deformations and highly modified flow fields. The flexibility of the blades is shown to significantly reduce the duration of the periodic stall regime; this observation is achieved through systematic comparison of the flow field, with a quantitative evaluation of the degree of chaotic changes in the wake. In this manner, the study provides insights into the mechanisms of the passive flow control achieved through blade flexibility in cross-flow turbines.

Experimental Study of Turbulent Macroinstabilities in an Agitated System with Axial High-Speed Impeller and with Radial Baffles

1996 ◽  
Vol 61 (6) ◽  
pp. 856-867 ◽  
Author(s):  
Oldřich Brůha ◽  
Ivan Fořt ◽  
Pavel Smolka ◽  
Milan Jahoda
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
High Speed ◽  
Experimental Results ◽  
Turbulent Regime ◽  
Frequency Of Occurrence ◽  
Visualization Method ◽  
Entire Flow

The frequency of turbulent macroinstability occurrence was measured in liquids agitated in a cylindrical baffled vessel. As it has been proved by preceding experimental results of the authors, the stochastic quantity with frequency of occurrence of 10-1 to 100 s-1 is concerned. By suitable choosing the viscosity of liquids and frequency of impeller revolutins, the region of Reynolds mixing numbers was covered from the pure laminar up to fully developed turbulent regime. In addition to the equipment making it possible to record automatically the macroinstability occurrence, also the visualization method and videorecording were employed. It enabled us to describe in more detail the form of entire flow field in the agitated system and its behaviour in connection with the macroinstability occurrence. It follows from the experiments made that under turbulent regime of flow of agitated liquids the frequency of turbulent macroinstability occurrence is the same as the frequency of the primary circulation of agitated liquid.

Numerical Simulation of Flowfield around High Speed Trains Passing by each other at the same Speed

2011 ◽  
Vol 97-98 ◽  
pp. 698-701
Author(s):  
Ming Lu Zhang ◽  
Yi Ren Yang ◽  
Li Lu ◽  
Chen Guang Fan
Keyword(s):  
Numerical Simulation ◽  
Wind Tunnel ◽  
Flow Field ◽  
Point Source ◽  
High Speed ◽  
Stokes Equations ◽  
Field Structure ◽  
Vehicle Speed ◽  
Mesh Method ◽  
High Speed Trains

Large eddy simulation (LES) was made to solve the flow around two simplified CRH2 high speed trains passing by each other at the same speed base on the finite volume method and dynamic layering mesh method and three dimensional incompressible Navier-Stokes equations. Wind tunnel experimental method of resting train with relative flowing air and dynamic mesh method of moving train were compared. The results of numerical simulation show that the flow field structure around train is completely different between wind tunnel experiment and factual running. Two opposite moving couple of point source and point sink constitute the whole flow field structure during the high speed trains passing by each other. All of streamlines originate from point source (nose) and finish with the closer point sink (tail). The flow field structure around train is similar with different vehicle speed.

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