Effect of injection position on fuel spray and mixture preparation of a free-piston linear engine generator

2020 ◽  
Vol 234 (8) ◽  
pp. 1161-1174
Author(s):  
Chenheng Yuan ◽  
Jiahui Li ◽  
Liange He ◽  
Yituan He
Keyword(s):  
Gas Exchange ◽  
Fuel Injection ◽  
Coupling Effect ◽  
Good Choice ◽  
Fuel Spray ◽  
Mixture Formation ◽  
Free Piston ◽  
Homogeneous Combustion ◽  
Large Injection ◽  
Process Coupling

Fuel spray and mixing in linear engines is coupled by dynamics, combustion, and gas exchange, which differs from that in conventional engines. This work presents a system simulation to reveal the multi-process coupling effect of injection position on the fuel spray and mixing of a free piston linear diesel engine (FPLE). A full-cycle fuel spray model which couples with dynamic, combustion, and gas exchange is established to predict the coupled effect on mixture formation. The results indicate that the variable injection position changes the FPLE motion through multi-process coupling effect, resulting in different boundary conditions for fuel spray and mixing. Relatively large injection advance position leads to more residual gas, fast speed, intense turbulence, low gas pressure, and temperature at the moment of injection for mixture formation. The earlier fuel injection generally makes the longer spray penetration, smaller Sauter mean diameter of droplets, less fuel impingement, faster fuel evaporation rate, and more evaporated fuel mass. However, too early injection does not support the above results. Suggesting that in order to achieve homogeneous combustion mode, the large injection advance position injection schedule operation is a good choice for the FPLE due to its long ignition delay duration for fuel atomization, evaporation, and mixing.

Modeling Mixture Formation in a Gasoline Direct Injection Engine

2005 ◽  
Vol 73 (6) ◽  
pp. 931-939 ◽  
Author(s):  
Rossella Rotondi
Keyword(s):  
Flow Field ◽  
Fuel Injection ◽  
Direct Injection ◽  
Operating Conditions ◽  
Gasoline Direct Injection ◽  
Injection System ◽  
Fuel Spray ◽  
Computational Domain ◽  
Mixture Formation ◽  
Wide Range

Mixture formation and combustion in a gasoline direct injection (GDI) engine were studied. A swirl-type nozzle, with an inwardly opening pintle, was used to inject the fuel directly in a four stroke, four cylinder, four valves per cylinder engine. The atomization of the hollow cone fuel spray was modeled by using a hybrid approach. The most important obstacle in the development of GDI engines is that the control of the stratified-charge combustion over the entire operating range is very difficult. Since the location of the ignition source is fixed in SI engines the mixture cloud must be controlled both temporally and spatially for a wide range of operating conditions. Results show that the volume of the spark must be considered when discretizing the computational domain because it highly influences the flow field in the combustion chamber. This is because the volume occupied by the plug cannot be neglected since it is much bigger than the ones used in port fuel injection engines. The development of a successful combustion system depends on the design of the fuel injection system and the matching with the in-cylinder flow field: the stratification at part load appears to be the most crucial and critical step, and if the air motion is not well coupled with the fuel spray it would lead to an increase of unburned hydrocarbon emission and fuel consumption

Free-Piston Compressor-Engines

1947 ◽  
Vol 156 (1) ◽  
pp. 253-271 ◽  
Author(s):  
H. O. Farmer
Keyword(s):  
Fuel Injection ◽  
Piston Compressor ◽  
Gas Generator ◽  
Compression Pressure ◽  
Compression Ignition Engine ◽  
Free Piston ◽  
Alternative Scheme ◽  
Free Piston Engine ◽  
New Type ◽  
Commercial Work

The Pescara free-piston engine has been developed in France during the last twenty years, and the paper gives a description of a portable air compressor which has been proved in commercial work, and is now in production. An explanation is given of those characteristics in which this engine differs from the orthodox engine-driven crankshaft compressor. The power unit is an opposed-piston two-stroke compression-ignition engine, the compressor piston being directly attached to one of the engine pistons, while the cushion piston is directly attached to the other. The cushion piston gives stability, ensures that the energy available for the return stroke is constant for any conditions of operation, and thus gives a constant compression pressure in the combustion cylinder. The velocity characteristics of the pistons during the inward and outward strokes are described with their effect on the compressor and other sections. The fuel injection gear and also an alternative scheme is described; and indicator diagrams show the results obtained. The output of the compressor is controlled by the governor; the governor controls the fuel injected and thus determines the stroke of the pistons and thereby the quantity of air delivered. The efficiency of the combustion section is given, with the specific fuel consumption loop of the compressor as a whole. Methods of starting, by use of a spring or compressed air, are given to illustrate the characteristics dealt with. The development of the free-piston compressor has led to the development of the power gas-generator, in which the combination of free-piston compressor and turbine forms a new type of prime mover.

Analysis of Mixture Formation and Flame Development of Diesel Combustion Using a Rapid Compression Machine and Optical Visualization Technique

2013 ◽  
Vol 315 ◽  
pp. 293-298 ◽  
Author(s):  
Amir Khalid ◽  
Bukhari Manshoor
Keyword(s):  
Fuel Injection ◽  
Injection Pressure ◽  
Exhaust Emissions ◽  
Combustion Characteristics ◽  
Diesel Combustion ◽  
Rapid Compression Machine ◽  
Mixture Formation ◽  
Optical Visualization ◽  
Flame Development ◽  
Rapid Compression

Mixture formation plays as a key element on burning process that strongly affects the exhaust emissions such as nitrogen oxide (NOx) and Particulate Matter (PM). The reductions of emissions can be achieved with improvement throughout the mixing of fuel and air behavior. Measurements were made in an optically-accessible rapid compression machine (RCM) with intended to simulate the actual diesel combustion related phenomena. The diesel combustion was simulated with the RCM which is equipped with the Denso single-shot common-rail fuel injection system, capable of a maximum injection pressure up to 160MPa. Diesel engine compression process could be reproduced within the wide range of ambient temperature, ambient density, swirl velocity, equivalence ratio and fuel injection pressure. The mixture formation and combustion images were captured by the high speed camera. Analysis of combustion characteristics and observations of optical visualization of images reveal that the mixture formation exhibit influences to the ignition process and flame development. Therefore, the examination of the first stage of mixture formation is very important consideration due to the fuel-air premixing process linked with the combustion characteristics. Furthermore, the observation of a systematic control of mixture formation with experimental apparatus enables us to achieve considerable improvements of combustion process and would present the information for fundamental understanding in terms of reduced fuel consumption and exhaust emissions.

scholarly journals Effects of Flooding on Physiology and Growth of Four Woody Ornamental Species in Marl Soil of South Florida

2010 ◽  
Vol 28 (3) ◽  
pp. 159-165
Author(s):  
Cliff G. Martin ◽  
Bruce Schaffer ◽  
Catharine Mannion
Keyword(s):  
Gas Exchange ◽  
Adventitious Roots ◽  
Calcareous Soil ◽  
Leaf Gas Exchange ◽  
Good Choice ◽  
South Florida ◽  
Heavy Clay ◽  
Ornamental Species ◽  
Periodic Flooding ◽  
Flood Prone Areas

Abstract In south Florida nurseries, trees are often grown in marl soil, which is heavy, clay-like, calcareous soil that is slow to drain and prone to periodic flooding during the rainy season. Green buttonwood, mahogany, pond apple and Surinam cherry are grown in this soil. We tested effects of flooding on leaf gas exchange and growth of these four species to determine their flood tolerances in marl soil. Green buttonwood, mahogany, and Surinam cherry each had consistently lower leaf gas exchange and plant growth in flooded than in non-flooded marl soil, which suggests low tolerance to flooding. In contrast, flooding had little or no effect on leaf gas exchange and growth of pond apple, indicating that this species was tolerant of flooding in marl soil. Green buttonwood and pond apple had larger stem diameters and more hypertrophic stem lenticels when flooded than when not flooded. Flooded green buttonwood also developed adventitious roots. Pond apple appears to be a good choice for planting in low-lying areas in marl soil typical of outdoor nurseries in south Florida. In contrast, care should be taken to avoid planting green buttonwood, mahogany, and Surinam cherry in marl soil in flood-prone areas.

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