Analyzing of in-cylinder flow structures and cyclic variations of partially premixed combustion in a light duty engine

Partially Premixed Combustion (PPC) strategy offers the potential for simultaneously reduction of NOx and soot emissions with high efficiency. This low temperature combustion strategy involves a proper mixing of fuel and air prior to auto-ignition. During ignition delay (ID) the exact amount of premixing is crucial for the combustion behaviour and emission formation.In this article, high-speed particle image velocimetry (HS-PIV) has been applied to characterise the in-cylinder flow and cycle-to-cycle variations in a light-duty optical engine during fired conditions. The engine is operated at 800 rpm and at a constant CA 50 (~ 8 CAD aTDC). Multiple injections strategies (single, double and triple injections) have been applied to investigate their influence on the flow inside the piston bowl and squish region. The 2D velocity fields are evaluated and investigated over a range of crank angles in the compression and expansion strokes in order to understand the cycle-to-cycle variations. To investigate the problem of cyclic- variations on in-cylinder flows the phase-invariant proper orthogonal decomposition (POD) technique was used. The POD decomposition technique provides a classification method based on an energy criterion by which the mean flow is seen as a superposition of coherent structures. From their temporal coefficients it is possible to characterize its dynamical behaviour

Time-resolved in-cylinder PIV measurement in a light duty optical engine under PPC conditions

The understanding of in-cylinder flow field is one of the keys to realize Partially Premixed Combustion (PPC) for internal combustion engines, which has potential to achieve high combustion efficiency with low soot and NOx emissions. In this work, time resolved Particle Image Velocimetry (PIV) was performed to measure the flow field inside the cylinder of a single-cylinder light-duty optical diesel engine.The engine was modified to Bowditch configuration, and was installed with a quartz piston and a transparent cylinder liner, to allow optical access. The geometry of the quartz piston crown is based on the regular combustion chamber design of mass produced diesel engine, including a re-entrant bowl shape. This causes severe distortion on the obtained images, which has to be handled by a distortion correction method before PIV process.The in-cylinder flow structures in a vertical plane at the center of cylinder were obtained both within the piston bowl and within the squish volume, during the compression and expansion stroke. Measurements were performed under three different injection strategies as well as motored engine condition. Both the instantaneous flow field from single cycle and ensemble average flow field calculated from 100 cycles at motored engine condition show a well match with previous studies. The results from fired engine conditions show different Interaction between injected fuel and in-cylinder air at different Crank Angle Degrees (CADs) with different injection strategies.All the results in this study can provide a quantitative dataset being useful to model validation of numerical simulation work to investigate PPC engine more

THE USE OF NDVI PROFILES FOR ESTIMATING THE QUALITY OF ARABLE LANDS (EXEMPLIFIED BY THE BAKSAN REGION IN KABARDINO-BALKARIA)

A new approach to estimating the quality of arable lands was developed as based upon MODIS-derived satellite data. The essence of the approach consists in an expert analysis of NDVI curves created separately for different crop groups in the last 10–12 years as well as the inter-annual variability of the NDVI seasonal maximum, whose value was used as an indicator for the crop state and yield on different fields. The nature of NDVI curves allowed expertly classifying the groups, characterizing the winter, early spring and late spring crops. The approach to estimating the quality of arable lands was approved on the example of the Baksan region in Kabardino-Balkaria. All the arable lands have been comprehensively analyzed in the region, the mask of which was created by visual interpretation of field boundaries using LANDSAT satellite data. The temporary NDVI profiles were obtained by the satellite service VEGA. Based upon the given method all the fields in the region were classified according to the quality of arable lands. The obtained data may be used in cadastre surveys for objective estimate of lands and optimal arrangement of the main agricultural crops in this Republic, being applicable in the other regions of the Russian Federation

Analyzing of in-cylinder flow structures and cyclic variations of partially premixed combustion in a light duty engine

Partially Premixed Combustion (PPC) strategy offers the potential for simultaneously reduction of NOx and soot emissions with high efficiency. This low temperature combustion strategy involves a proper mixing of fuel and air prior to auto-ignition. During ignition delay (ID) the exact amount of premixing is crucial for the combustion behaviour and emission formation. In this article, high-speed particle image velocimetry (HS-PIV) has been applied to characterise the in-cylinder flow and cycle-to-cycle variations in a light-duty optical engine during fired conditions. The engine is operated at 800 rpm and at a constant CA 50 (~ 8 CAD aTDC). Multiple injections strategies (single, double and triple injections) have been applied to investigate their influence on the flow inside the piston bowl and squish region. The 2D velocity fields are evaluated and investigated over a range of crank angles in the compression and expansion strokes in order to understand the cycle-to-cycle variations. To investigate the problem of cyclic- variations on in-cylinder flows the phase-invariant proper orthogonal decomposition (POD) technique was used. The POD decomposition technique provides a classification method based on an energy criterion by which the mean flow is seen as a superposition of coherent structures. From their temporal coefficients it is possible to characterize its dynamical behaviour

Influence of the number of injections on piston heat rejection under low temperature combustion conditions in an optical compression-ignition engine

New combustion concepts are being investigated to develop cleaner engines. One of the most promising is partially premixed combustion. The mechanisms of this combustion mode and its impact on performance and emissions have been studied in the previous years. Nevertheless, little research has been done from the point of view of heat transfer. In particular, the influence of the injection strategy on heat transfer is of great interest in partially premixed combustion. This work presents a method to calculate convective heat transfer to the piston. The method uses a combination of gas velocity models and experimental velocity data measured with the PIV technique. This method was applied to achieve the goal of studying the effect of the number of injections on heat rejection. First, the influence of the injection strategy on gas motion was examined. To do that, an analysis of the velocity components relevant to gas-surface convection was conducted, as well as of the resulting heat transfer coefficient. Next, heat flux results were discussed. The single injection strategy showed the highest heat transfer, followed by triple injection and double injection. Important instantaneous variations of heat flux were observed at different locations of the piston bowl. All findings were associated with concurring conditions of high gas velocity, density and temperature

Time-resolved in-cylinder PIV measurement in a light duty optical engine under PPC conditions

The understanding of in-cylinder flow field is one of the keys to realize Partially Premixed Combustion (PPC) for internal combustion engines, which has potential to achieve high combustion efficiency with low soot and NOx emissions. In this work, time resolved Particle Image Velocimetry (PIV) was performed to measure the flow field inside the cylinder of a single-cylinder light-duty optical diesel engine. The engine was modified to Bowditch configuration, and was installed with a quartz piston and a transparent cylinder liner, to allow optical access. The geometry of the quartz piston crown is based on the regular combustion chamber design of mass produced diesel engine, including a re-entrant bowl shape. This causes severe distortion on the obtained images, which has to be handled by a distortion correction method before PIV process. The in-cylinder flow structures in a vertical plane at the center of cylinder were obtained both within the piston bowl and within the squish volume, during the compression and expansion stroke. Measurements were performed under three different injection strategies as well as motored engine condition. Both the instantaneous flow field from single cycle and ensemble average flow field calculated from 100 cycles at motored engine condition show a well match with previous studies. The results from fired engine conditions show different Interaction between injected fuel and in-cylinder air at different Crank Angle Degrees (CADs) with different injection strategies. All the results in this study can provide a quantitative dataset being useful to model validation of numerical simulation work to investigate PPC engine more

Analyzing of in-cylinder flow structures and cyclic variations of partially premixed combustion in a light duty engine

Partially Premixed Combustion (PPC) strategy offers the potential for simultaneously reduction of NOx and soot emissions with high efficiency. This low temperature combustion strategy involves a proper mixing of fuel and air prior to auto-ignition. During ignition delay (ID) the exact amount of premixing is crucial for the combustion behaviour and emission formation.\u3cbr/\u3eIn this article, high-speed particle image velocimetry (HS-PIV) has been applied to characterise the in-cylinder flow and cycle-to-cycle variations in a light-duty optical engine during fired conditions. The engine is operated at 800 rpm and at a constant CA 50 (~ 8 CAD aTDC). Multiple injections strategies (single, double and triple injections) have been applied to investigate their influence on the flow inside the piston bowl and squish region. The 2D velocity fields are evaluated and investigated over a range of crank angles in the compression and expansion strokes in order to understand the cycle-to-cycle variations. To investigate the problem of cyclic- variations on in-cylinder flows the phase-invariant proper orthogonal decomposition (POD) technique was used. The POD decomposition technique provides a classification method based on an energy criterion by which the mean flow is seen as a superposition of coherent structures. From their temporal coefficients it is possible to characterize its dynamical behaviour

Time-resolved in-cylinder PIV measurement in a light duty optical engine under PPC conditions

The understanding of in-cylinder flow field is one of the keys to realize Partially Premixed Combustion (PPC) for internal combustion engines, which has potential to achieve high combustion efficiency with low soot and NOx emissions. In this work, time resolved Particle Image Velocimetry (PIV) was performed to measure the flow field inside the cylinder of a single-cylinder light-duty optical diesel engine.\u3cbr/\u3eThe engine was modified to Bowditch configuration, and was installed with a quartz piston and a transparent cylinder liner, to allow optical access. The geometry of the quartz piston crown is based on the regular combustion chamber design of mass produced diesel engine, including a re-entrant bowl shape. This causes severe distortion on the obtained images, which has to be handled by a distortion correction method before PIV process.\u3cbr/\u3eThe in-cylinder flow structures in a vertical plane at the center of cylinder were obtained both within the piston bowl and within the squish volume, during the compression and expansion stroke. Measurements were performed under three different injection strategies as well as motored engine condition. Both the instantaneous flow field from single cycle and ensemble average flow field calculated from 100 cycles at motored engine condition show a well match with previous studies. The results from fired engine conditions show different Interaction between injected fuel and in-cylinder air at different Crank Angle Degrees (CADs) with different injection strategies.\u3cbr/\u3eAll the results in this study can provide a quantitative dataset being useful to model validation of numerical simulation work to investigate PPC engine more

Effects of injection timing on fluid flow characteristics of partially premixed combustion based on high-speed particle image velocimetry

Partially premixed combustion (PPC) is a promising combustion concept to meet the increasing demands of emission legislation and to improve fuel efficiency. Longer ignition delay of PPC in comparison with conventional diesel combustion provide better fuel/air mixture which decreases soot and NOx emissions. Moreover, a proper injection timing and strategy for PPC can improve the combustion stability as a result of a higher level of fuel stratification in comparison with Homogeneous Charge Compression Ignition (HCCI) concept. Different injection timings affect this level of fuel and combustion stratification which helps to control the combustion timing and the heat release behavior. The scope of the present study is to investigate the fluid flow characteristics of PPC at different injection timings. To better understand this, high-speed Particle Image Velocimetry (PIV) is implemented in a light duty optical engine to measure fluid flow characteristics inside the piston bowl as well as the squish region with a temporal resolution of 1 crank angle degree at 800 rpm. Combustion phasing is kept constant for different injection timings and flow behavior including the mean velocity, turbulent kinetic energy and cycle-resolved turbulence during the injection and combustion phenomena are measured. Two different injectors with 5 and 7 holes are also compared to see their effects on fluid flow and heat release behaviors. Formation of the vortices and turbulence enhance the air fuel interaction, changing the level of fuel stratification and combustion duration. Results well demonstrate how these different turbulent kinetic energies can correlate with heat release behaviors. Furthermore, the research provide a quantitative dataset for validation of numerical simulations