A new LES approach to trans-critical mixing and combustion processes in high-pressure liquid-injectant engines

2020 ◽  
Author(s):  
Akira Umemura ◽  
Junji Shinjo
Keyword(s):  
High Pressure ◽  
Combustion Processes ◽  
Critical Mixing

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.

Spark-Ignition and Combustion Characteristics of High-Pressure Hydrogen and Natural-Gas Intermittent Jets

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
Ali Mohammadi ◽  
Masahiro Shioji ◽  
Yuki Matsui ◽  
Rintaro Kajiwara
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Ambient Pressure ◽  
Direct Injection ◽  
Injection Pressure ◽  
Spark Ignition ◽  
Constant Volume Combustion Chamber ◽  
Si Engines ◽  
Ignition And Combustion ◽  
Combustion Processes

Recently, an in-cylinder injection method has been considered for the improvement of thermal efficiency in natural-gas and hydrogen spark-ignition (SI) engines. However, the SI and combustion processes of gaseous jets are not well understood. The present study aims to provide fundamental data for the development of direct-injection SI gas engines. The ignition, combustion, and flame behavior of high-pressure and intermittent hydrogen and natural-gas jets in a constant volume combustion chamber were investigated. The effects of injection pressure, nozzle size, ambient pressure, and spark location were also investigated for various spark timings and equivalence ratios.

scholarly journals Formation of Soot in Oxygen-Enriched Turbulent Propane Flames at the Technical Scale

Energies ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 191
Author(s):  
Rikard Edland ◽  
Thomas Allgurén ◽  
Fredrik Normann ◽  
Klas Andersson
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
High Temperature ◽  
Oxygen Concentration ◽  
Soot Formation ◽  
Atmospheric Conditions ◽  
Total Flow ◽  
Total Flow Rate ◽  
Partial Pressures ◽  
Combustion Processes

Soot is an important component for heat transfer in combustion processes. However, it is also a harmful pollutant for humans, and strict emissions legislation motivates research on how to control soot formation and release. The formation of soot is known to be triggered by high temperature and high pressure during combustion, and it is also strongly influenced by the local stoichiometry. The current study investigates how the formation of soot is affected by increasing the oxygen concentration in the oxidizer, since this affects both the temperature profile and partial pressures of reactants. The oxygen-to-fuel ratio is kept constant, i.e., the total flow rate of the oxidizer decreases with increasing oxygen concentration. Propane is combusted (80 kWth) while applying oxygen-enriched air, and in-flame measurements of the temperature and gas concentrations are performed and combined with available soot measurements. The results show that increasing the oxygen concentration in the oxidizer from 21% to 27% slightly increases soot formation, due to higher temperatures or the lower momentum of the oxidizer. At 30% oxygen, however, soot formation increases by orders of magnitude. Detailed reaction modeling is performed and the increase in soot formation is captured by the model. Both the soot inception rates and surface growth rates are significantly increased by the changes in combustion conditions, with the increase in soot inception being the most important. Under atmospheric conditions, there is a distinct threshold for soot formation at around 1200 °C for equivalence ratios >3. The increase in temperature, and the slower mixing that results from the lower momentum of the oxidizer, have the potential to push the combustion conditions over this threshold when the oxygen concentration is increased.

High-Pressure Ignition of Oil Sands Samples in Oxygen Atmospheres Containing Various Concentrations of Diluents

1990 ◽  
Vol 112 (4) ◽  
pp. 264-267 ◽  
Author(s):  
S. A. Mehta ◽  
G. A. Karim
Keyword(s):  
High Pressure ◽  
Oil Sands ◽  
Morphological Changes ◽  
Pure Oxygen ◽  
Experimental Program ◽  
Nickel Chromium ◽  
Ignition Characteristics ◽  
Combustion Processes

In-situ recovery of oil from oil sands deposits by combustion requires the injection of vast quantities of oxygen into the bed of deposits. Accordingly, there is a need to establish the ignition characteristics of high-grade Athabasca oil sands in environments containing pure oxygen at high-pressure and including the role of the presence of various diluents with the oxygen. A high-pressure constant volume bomb with a water calorimeter was employed as the test apparatus over the pressure range of 0.1 MPa to 4.0 MPa at ambient temperature. The role of the presence of the diluents, helium, nitrogen and carbon dioxide, with the oxygen, was also considered. Controlled ignition was achieved by employing electrically fusable nickel-chromium wire looped around the sample. Moreover, the presence of an ignition promotor such as benzoic acid was also considered. The paper presents the results of an experimental program that examined the effects of changes in the pressure, amounts of diluents and ignition energy on the ignition limits and subsequent combustion processes at ambient initial temperature. Moreover, the morphological changes to the samples at various stages of the process were also examined and discussed.

Sign in / Sign up

Export Citation Format

Share Document