scholarly journals A study of charge exchange in a residual-effected HCCI gasoline engine

2011 ◽  
Vol 145 (2) ◽  
pp. 25-34
Author(s):  
Jacek HUNICZ
Keyword(s):  
Charge Exchange ◽  
Gasoline Engine ◽  
Exchange Process ◽  
Charge Composition ◽  
Cylinder Pressure ◽  
Charge Exchange Process ◽  
Variable Valve Actuation ◽  
Negative Valve Overlap ◽  
Variable Valve ◽  
Valve Overlap

An in-cylinder charge exchange process in a gasoline homogeneous charge compression ignition (HCCI) engine operated in a negative valve overlap (NVO) mode was studied. Research was performed using a single-cylinder research engine with fully variable valve actuation. Combination of in-cylinder pressure traces processing and fluid flow model enables cycle-by-cycle analysis of charge composition and temperature. It allows forecasting of in cylinder pressure volume and temperature-volume histories and can be used for physical-based engine control. In this paper influence of valves timings and valves lifts on the gas exchange process was analyzed. Special attention was paid to the effects of backflows of the in cylinder charge to an intake port.

Low Temperature Phase Transition (Pt) and Defect Formation (Df) in Silicon with Dioxide Inclusions Under X-Ray Irradiation

1995 ◽  
Vol 396 ◽  
Author(s):  
SH.M. Makhkamov ◽  
S.N. Abdurakhmanova
Keyword(s):  
Phase Transition ◽  
Charge Exchange ◽  
Defect Formation ◽  
Exchange Process ◽  
Temperature Phase ◽  
X Rays ◽  
Charge Exchange Process ◽  
X Ray ◽  
Temperature Phase Transition ◽  
A Charge

AbstractStudies of galvanomagnetic and electrical parameters of p- type Si : SiO2 in the temperature range 80 – 400 K have shown that X-ray irradiation at 80 K (Mo Ka,β and braking radiation hvmax. = 50 heV) leads to various transformations of the spectrum of electron- hole states in the band gap of such material, depending on the flux density of the X-rays. Two main processes are observed: the defect (vacancy and divacancy) formation and a charge exchange of native defects localized at the Si – SiO2 interface. The charge exchange process is rather collective and stimulated one because it is in response to an X-ray-induced ferroelectric phase transition in the SiO2- phase.

Numerical study on combustion characteristics of six-stroke-cycle gasoline compression ignition engine with continuously variable valve duration valve technology

2019 ◽  
Vol 22 (1) ◽  
pp. 165-183 ◽  
Author(s):  
Oudumbar Rajput ◽  
Youngchul Ra ◽  
Kyoung-Pyo Ha ◽  
You-Sang Son
Keyword(s):  
Numerical Study ◽  
Power Stroke ◽  
Compression Ignition ◽  
Ignition Timing ◽  
Compression Ignition Engine ◽  
Engine Operation ◽  
Wide Range ◽  
Negative Valve Overlap ◽  
Variable Valve ◽  
Valve Overlap

Engine performance and emissions of a six-stroke gasoline compression ignition engine with a wide range of continuously variable valve duration control were numerically investigated at low engine load conditions. For the simulations, an in-house three-dimensional computational fluid dynamics code with high-fidelity physical sub-models was used, and the combustion and emission kinetics were computed using a reduced kinetics mechanism for a 14-component gasoline surrogate fuel. Variation of valve timing and duration was considered under both positive valve overlap and negative valve overlap including the rebreathing of intake valves via continuously variable valve duration control. Close attention was paid to understand the effects of two additional strokes of the engine cycle on the thermal and chemical conditions of charge mixtures that alter ignition, combustion and energy recovery processes. Double injections were found to be necessary to effectively utilize the additional two strokes for the combustion of overly mixed lean charge mixtures during the second power stroke. It was found that combustion phasing in both power strokes is effectively controlled by the intake valve closure timing. Engine operation under negative valve overlap condition tends to advance the ignition timing of the first power stroke but has minimal effect on the ignition timing of second power stroke. Re-breathing was found to be an effective way to control the ignition timing in second power stroke at a slight expense of the combustion efficiency. The operation of a six-stroke gasoline compression ignition engine could be successfully simulated. In addition, the operability range of the six-stroke gasoline compression ignition engine could be substantially extended by employing the continuously variable valve duration technique.

scholarly journals Modeling of the Hα Emission from ADITYA Tokamak Plasmas

Atoms ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 95
Author(s):  
Ritu Dey ◽  
Malay B. Chowdhuri ◽  
Joydeep Ghosh ◽  
Ranjana Manchanda ◽  
Nandini Yadava ◽  
...  
Keyword(s):  
Charge Exchange ◽  
Molecular Hydrogen ◽  
Neutral Particle ◽  
Exchange Process ◽  
Neutral Hydrogen ◽  
Spatial Profile ◽  
Charge Exchange Process ◽  
Neutral Particle Transport ◽  
Particle Penetration ◽  
Hα Emission

The spatial profile of Hα spectrum is regularly measured using a high-resolution multi-track spectrometer in ADITYA tokamak to study the neutral particle behavior. The Monte Carlo neutral particle transport code DEGAS2 is used to model the experimental Hα spectral emissions. Through the modeling of the spectral line profile of Hα, it is found that the neutral hydrogen, which is produced from molecular hydrogen and molecular hydrogen ion dissociation processes contributes 56% to the total Hα emission, and the atoms which are produced from charge-exchange process have 30% contribution. Furthermore, the experimentally measured spatial profile of chord integrated brightness was modeled for the two plasma discharges having relatively high and low density to understand the neutral particle penetration. The presence of neutrals inside the core region of the ADITYA tokamak is mainly due to the charge-exchange process. Furthermore, it is observed that neutral particle penetration is lower in higher density discharge.

Assessment of Residual Mass Estimation Methods for Cylinder Pressure Heat Release Analysis of HCCI Engines With Negative Valve Overlap

2011 ◽  
Author(s):  
Elliott A. Ortiz-Soto ◽  
Jiri Vavra ◽  
Aristotelis Babajimopoulos
Keyword(s):  
Heat Release ◽  
State Equation ◽  
Operating Conditions ◽  
Exhaust Valve ◽  
Estimation Methods ◽  
Cylinder Pressure ◽  
Hcci Engines ◽  
Release Analysis ◽  
Negative Valve Overlap ◽  
Valve Overlap

Increased residual levels in Homogeneous Charge Compression Ignition (HCCI) engines employing valve strategies such as recompression or negative valve overlap (NVO) imply that accurate estimation of residual gas fraction (RGF) is critical for cylinder pressure heat release analysis. The objective of the present work was to evaluate three residual estimation methods and assess their suitability under naturally aspirated and boosted HCCI operating conditions: i) the Simple State Equation method employs the Ideal Gas Law at exhaust valve closing (EVC); ii) the Mirsky method assumes isentropic exhaust process; and iii) the Fitzgerald method models in-cylinder temperature from exhaust valve opening (EVO) to EVC by accounting for heat loss during the exhaust process and uses measured exhaust temperature for calibration. Simulations with a calibrated and validated “virtual engine” were performed for representative HCCI operating conditions of engine speed, fuel-air equivalence ratio, NVO and intake pressure (boosting). The State Equation method always overestimated RGF by more than 10%. The Mirsky method was most robust, with average errors between 3–5%. The Fitzgerald method performed consistently better, ranging from no error to 5%, where increased boosting caused the largest discrepancies. A sensitivity study was also performed and determined that the Mirsky method was most robust to possible pressure and temperature measurement errors.

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