scholarly journals Analysis of the effect of bore/stroke ratio and scavenge port angles on the scavenging process in a two-stroke boosted uniflow scavenged direct injection gasoline engine

2017 ◽  
Vol 232 (13) ◽  
pp. 1799-1814 ◽  
Author(s):  
Xinyan Wang ◽  
Jun Ma ◽  
Hua Zhao
Keyword(s):  
Gasoline Engine ◽  
Direct Injection ◽  
Three Dimensional ◽  
Orientation Angle ◽  
Swirl Flow ◽  
Delivery Ratio ◽  
Boost Pressure ◽  
Baseline Design ◽  
Dynamics Simulations ◽  
Scavenging Efficiency

In this study, a two-stroke boosted uniflow scavenged direct injection gasoline (BUSDIG) engine was proposed and researched to achieve aggressive engine downsizing and downspeeding. Compared to loop or cross scavenged two-stroke engines, the BUSDIG engine can achieve excellent scavenging performance and be operated with higher boost pressure as well as the absence of air and fuel short-circuiting. As a fundamental engine geometric parameter, the bore/stroke (B/S) ratio would directly affect the scavenging process in the uniflow scavenged two-stroke engine. Three-dimensional computational fluid dynamics simulations were used to investigate the scavenging process in the BUSDIG engine with different B/S ratios. Four B/S ratios of 0.66, 0.8, 1, and 1.3 were analyzed. The results indicate that a bigger B/S ratio leads to deteriorated swirl flow motion but better delivery ratio, scavenging efficiency, and charging efficiency. In order to fulfil the potential of the BUSDIG engine with different B/S ratios, two key scavenge port angles, i.e. axis inclination angle (AIA) and swirl orientation angle (SOA), were varied from the baseline design (AIA = 90°, SOA = 20°) to study their effects on the scavenging process for each B/S ratio design. Overall, a larger AIA leads to lower swirl ratio (SR) but achieves better scavenge performance, which is crucial for a large B/S ratio design. A small SOA design leads to noticeably lower SR but superior scavenging performances for a small B/S ratio design. An intermediate SOA, e.g. 10 and 20°, is preferred to improve the scavenging for a large B/S ratio design.

scholarly journals Analysis of scavenge port designs and exhaust valve profiles on the in-cylinder flow and scavenging performance in a two-stroke boosted uniflow scavenged direct injection gasoline engine

2017 ◽  
Vol 19 (5) ◽  
pp. 509-527 ◽  
Author(s):  
Xinyan Wang ◽  
Jun Ma ◽  
Hua Zhao
Keyword(s):  
Gasoline Engine ◽  
Direct Injection ◽  
Orientation Angle ◽  
Exhaust Valve ◽  
Direct Injection Gasoline Engine ◽  
Valve Opening ◽  
The Difference ◽  
Cylinder Flow ◽  
Exhaust Valves ◽  
Scavenging Efficiency

In this study, effects of intake scavenge port designs and exhaust valve opening profiles were studied on the scavenging process in a newly proposed two-stroke boosted uniflow scavenged direct injection gasoline engine by detailed three-dimensional engine simulations. As the most important geometric parameters, the axis inclination angle and swirl orientation angle of scavenge ports, as shown in Figure 1, were investigated and optimized for best scavenging performances at first. With the optimal axis inclination angle of 90° and swirl orientation angle of 20°, various combinations of scavenge port opening timing, exhaust valve opening duration and exhaust valve opening timing were then analysed. Four distinct scavenging periods, that is, early backflow period, backflow scavenging period, main scavenging period and post backflow period, were identified and their impacts on the in-cylinder flow motions and scavenging performances were investigated. The results show that the optimal scavenging performance can be achieved with a higher delivery ratio, charging efficiency and scavenging efficiency when the post backflow is just avoided by tuning the difference between the closing timings of scavenge ports and exhaust valves (Δ close) and the overlap between the opening profiles of scavenge ports and exhaust valves (Δ overlap) for a specific exhaust valve opening duration. A longer exhaust valve opening duration can be used to further improve the scavenging performances. In addition, the difference between the opening timings of scavenge ports and exhaust valves (Δ open) can be increased to improve scavenging efficiency. The Δ close also shows strong positive correlation with in-cylinder swirl ratio and negative correlation with tumble ratio. The results presented in this study provide the fundamental knowledge of the scavenging process in the uniflow scavenged two-stroke engine and assist the design of scavenge ports and valve strategies to optimize in-cylinder flow motion and scavenge performances in the two-stroke boosted uniflow scavenged direct injection gasoline engine with a variable valve actuation system for exhaust valves.

Simulation of the Gas Exchange Process of a Two-Stroke Cycle Gasoline Engine

1988 ◽  
Vol 110 (3) ◽  
pp. 369-376 ◽  
Author(s):  
K. Sato ◽  
M. Nakano
Keyword(s):  
Gasoline Engine ◽  
Short Circuit ◽  
Exchange Process ◽  
Effective Means ◽  
Three Dimensional ◽  
Trapping Efficiency ◽  
Delivery Ratio ◽  
Exhaust Pipe ◽  
Full Throttle ◽  
Stroke Cycle

This report deals with a study concerning the scavenging performance of a two-stroke cycle gasoline engine under the following conditions: the throttle of the carburetor is set at variable levels, the delivery ratio is set at a predetermined level, the engine speed is varied, and the scavenging and exhaust ports are set at different heights. If the properly selected factors stipulated for a scavenging model are used, the calculated results can be made as consistent as the measured results of the carburetor set at full throttle, as discussed in the previous reports [1, 2]. The mass diffusion, mixing, and short-circuit factors make up the essential coefficients. The factors represent major characteristics: blow-back, return-blow, and the loss of fresh gases. These phenomena are more clearly illustrated by three-dimensional representations of the gas components in the scavenging passage and exhaust pipe. The analyses of these functions may provide an effective means of improving the scavenging performance, i.e., the delivery ratio, trapping efficiency, and charging efficiency.

Investigating the Effect of Utilizing New Induction Manifold Designs on the Combustion Characteristics and Emissions of a Direct Injection Diesel Engine

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Mohamed A. Bassiony ◽  
Abdellatif M. Sadiq ◽  
Mohammed T. Gergawy ◽  
Samer F. Ahmed ◽  
Saud A. Ghani
Keyword(s):  
Diesel Engine ◽  
Peak Pressure ◽  
Direct Injection ◽  
Three Dimensional ◽  
Engine Performance ◽  
Combustion Characteristics ◽  
Maximum Pressure ◽  
Performance And Emissions ◽  
Di Diesel Engine ◽  
Dynamics Simulations

New induction manifold designs have been developed in this work to enhance the turbulence intensity and improve the mixing quality inside diesel engine cylinders. These new designs employ a spiral-helical shape with three different helical diameters (1D, 2D, 3D; where D is the inner diameter of the manifold) and three port outlet angles: 0 deg, 30 deg, and 60 deg. The new manifolds have been manufactured using three-dimensional printing technique. Computational fluid dynamics simulations have been conducted to estimate the turbulent kinetic energy (TKE) and the induction swirl generated by these new designs. The combustion characteristics that include the maximum pressure raise rate (dP/dθ) and the peak pressure inside the cylinder have been measured for a direct injection (DI) diesel engine utilizing these new manifold designs. In addition, engine performance and emissions have also been evaluated and compared with those of the normal manifold of the engine. It was found that the new manifolds with 1D helical diameter produce a high TKE and a reasonably strong induction swirl, while the ones with 2D and 3D generate lower TKEs and higher induction swirls than those of 1D. Therefore, dP/dθ and peak pressure were the highest with manifolds 1D, in particular manifold m (D, 30). Moreover, this manifold has provided the lowest fuel consumption with the engine load by about 28% reduction in comparison with the normal manifold. For engine emissions, m (D, 30) manifold has generated the lowest CO, SO2, and smoke emissions compared with the normal and other new manifolds as well, while the NO emission was the highest with this manifold.

Flow Dynamics of Unconfined Swirling Flames Under Fuel-Lean Conditions

2006 ◽  
Author(s):  
S. S. Archer ◽  
A. K. Gupta ◽  
K. Kitagawa
Keyword(s):  
Direct Injection ◽  
Air Flow ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Swirl Flow ◽  
Flow Dynamics ◽  
Swirl Number ◽  
Burner Exit ◽  
Swirl Vane

This study provides the role of co- and counter swirl distribution in a experimental double concentric swirl burner that simulates the that simulates one swirl cup of a practical gas turbine combustor. Results of the effect of radial distribution of swirl in a burner under unconfined non-burning and combustion conditions are presented on the flow dynamics of a fuel-lean direct injection (LDI) configuration using propane as the fuel. Three-dimensional (3-D) flowfield data has been obtained immediately downstream of the burner exit to determine the detailed flow dynamics associated with the flow. The fuel was injected radially into the surrounding swirl flow. Flow characteristics, both without and with combustion, have been obtained for the co- and counter-swirl distributions to the combustion air flow under unconfined conditions. Flat vane swirlers have been used to induce swirl to the air flow. Both combustion and swirl distribution significantly influences the resulting flowfield. The resulting swirl number of the flow was calculated using the 3-D velocity data. Results show that swirl distribution in the burner and combustion provides significant effect on the characteristics of the internal and external recirculation zones. The heat release from combustion enhances the inner recirculation zone by increasing its width and length. Combustion causes significant increase to the velocity and vorticity magnitudes in the flow, and promotes flowfield symmetry. Combustion also affects the swirl number of the flow. The swirl number calculated from the geometrical relationships, derived from the swirl vane angle and swirler dimensions, is much different than that determined from the 3-D velocity field data. The entrained mass flow rate is larger for the co-swirl distribution case and this entrainment is further enhanced with combustion. The results provide the role of radial swirl distribution on the mean and turbulence characteristics of flows for the two different shear flow conditions between the inner and outer annulus of the burner.

scholarly journals Online biophysical predictions for SARS-CoV-2 proteins

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Luciano Kagami ◽  
Joel Roca-Martínez ◽  
Jose Gavaldá-García ◽  
Pathmanaban Ramasamy ◽  
K. Anton Feenstra ◽  
...  
Keyword(s):  
Protein Sequence ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Static Structure ◽  
Homologous Proteins ◽  
Structure Based Drug Design ◽  
Protein Protein Interaction ◽  
Link Type ◽  
Dynamics Simulations ◽  
Β Sheet

Abstract Background The SARS-CoV-2 virus, the causative agent of COVID-19, consists of an assembly of proteins that determine its infectious and immunological behavior, as well as its response to therapeutics. Major structural biology efforts on these proteins have already provided essential insights into the mode of action of the virus, as well as avenues for structure-based drug design. However, not all of the SARS-CoV-2 proteins, or regions thereof, have a well-defined three-dimensional structure, and as such might exhibit ambiguous, dynamic behaviour that is not evident from static structure representations, nor from molecular dynamics simulations using these structures. Main We present a website (https://bio2byte.be/sars2/) that provides protein sequence-based predictions of the backbone and side-chain dynamics and conformational propensities of these proteins, as well as derived early folding, disorder, β-sheet aggregation, protein-protein interaction and epitope propensities. These predictions attempt to capture the inherent biophysical propensities encoded in the sequence, rather than context-dependent behaviour such as the final folded state. In addition, we provide the biophysical variation that is observed in homologous proteins, which gives an indication of the limits of their functionally relevant biophysical behaviour. Conclusion The https://bio2byte.be/sars2/ website provides a range of protein sequence-based predictions for 27 SARS-CoV-2 proteins, enabling researchers to form hypotheses about their possible functional modes of action.

scholarly journals Polymer cyclization for the emergence of hierarchical nanostructures

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chaojian Chen ◽  
Manjesh Kumar Singh ◽  
Katrin Wunderlich ◽  
Sean Harvey ◽  
Colette J. Whitfield ◽  
...  
Keyword(s):  
Self Assembly ◽  
Three Dimensional ◽  
Hierarchical Structures ◽  
Structural Similarity ◽  
Vital Role ◽  
Nanomaterial Synthesis ◽  
Wide Range ◽  
Linear Poly ◽  
Polymer Folding ◽  
Dynamics Simulations

AbstractThe creation of synthetic polymer nanoobjects with well-defined hierarchical structures is important for a wide range of applications such as nanomaterial synthesis, catalysis, and therapeutics. Inspired by the programmability and precise three-dimensional architectures of biomolecules, here we demonstrate the strategy of fabricating controlled hierarchical structures through self-assembly of folded synthetic polymers. Linear poly(2-hydroxyethyl methacrylate) of different lengths are folded into cyclic polymers and their self-assembly into hierarchical structures is elucidated by various experimental techniques and molecular dynamics simulations. Based on their structural similarity, macrocyclic brush polymers with amphiphilic block side chains are synthesized, which can self-assemble into wormlike and higher-ordered structures. Our work points out the vital role of polymer folding in macromolecular self-assembly and establishes a versatile approach for constructing biomimetic hierarchical assemblies.

Experimental research on scavenging process of opposed-piston two-stroke gasoline engine based on tracer gas method

2021 ◽  
pp. 146808742110366
Author(s):  
Fukang Ma ◽  
Wei Yang ◽  
Yifang Wang ◽  
Junfeng Xu ◽  
Yufeng Li
Keyword(s):  
Gas Exchange ◽  
Exchange Process ◽  
Delivery Ratio ◽  
Tracer Gas ◽  
Piston Motion ◽  
Trapped Air ◽  
Exchange Performance ◽  
Gdi Engine ◽  
Gas Exchange Process ◽  
Scavenging Efficiency

The scavenging process of two stroke engine includes free exhaust, scavenging, and post intake process, which clears the burned gas in cylinder and suctions the fresh air for next cycle. The gas exchange process of Opposed-Piston Two-Stroke (OP2S) engine with gasoline direct injection (GDI) engine is a uniflow scavenging method between intake port and exhaust port. In order to investigate the characteristics of the gas exchange process in OP2S-GDI engine, a specific tracer gas method (TGM) was developed and the experiments were carried out to analyze the gas exchange performance under different intake and exhaust conditions and opposed-piston movement rule. The results show that gas exchange performance and trapped gas mass are significantly influenced by intake pressure and exhaust pressure. And it has a positive effect on the scavenging efficiency and the trapped air mass. Scavenging efficiency and trapped air mass are almost independent of pressure drop when the delivery ratio exceeds 1.4. Consequently, the delivery ratio ranges from 0.5 to 1.4 is chosen to achieve an optimization of steady running and minimum pump loss. The opposed piston motion phase difference only affects the scavenging timing. Scavenging performance is mainly influenced by scavenging timing and scavenging duration. With the increased phase difference of piston motion, the scavenging efficiency and delivery ratio increased gradually, the trapping efficiency would increase first and decrease then and reaches its maximum at 14°CA.

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