The Effect of In-Cylinder Turbulence on Lean, Premixed, Spark Ignited Engine Performance

2015 ◽  
Author(s):  
Baine Breaux ◽  
Chris Hoops ◽  
William Glewen
Keyword(s):  
High Speed ◽  
Combustion Engine ◽  
Three Dimensional ◽  
Engine Performance ◽  
Small Scale ◽  
Cylinder Wall ◽  
Lean Burn ◽  
Combustion Duration ◽  
Rate Of Heat Release ◽  
Operational Constraints

The intensity and structure of in-cylinder turbulence is known to have a significant effect on internal combustion engine performance. Changes in flow structure and turbulence intensity result in changes to the rate of heat release, cylinder wall heat rejection, and cycle-to-cycle combustion variability. This paper seeks to quantify these engine performance consequences and identify fundamental similarities across a range of high-speed, medium-bore, lean-burn, spark-ignited reciprocating engines. In-cylinder turbulence was manipulated by changing the extent of intake port-induced swirl as well as varying the level of piston-generated turbulence. The relationship between in-cylinder turbulence and engine knock is also discussed. Increasing in-cylinder turbulence generally reduces combustion duration, but test results reveal that increasing swirl beyond a critical point can cause a lengthening of burn durations and greatly reduced engine performance. This critical swirl level is related to the extent of small-scale, piston generated turbulence present in the cylinder. Increasing in-cylinder turbulence generally leads to reduced cycle-to-cycle variability and increased detonation margin. The overall change in thermal efficiency was dependent on the balance of these factors and wall heat transfer, and varied depending on the operational constraints for a given engine and application. Single cylinder engine test data, supported with three dimensional CFD results are used to demonstrate and explain these basic combustion engine principles.

The Effect of In-Cylinder Turbulence on Lean, Premixed, Spark-Ignited Engine Performance

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Baine Breaux ◽  
Chris Hoops ◽  
William Glewen
Keyword(s):  
High Speed ◽  
Combustion Engine ◽  
Three Dimensional ◽  
Engine Performance ◽  
Small Scale ◽  
Cylinder Wall ◽  
Lean Burn ◽  
Combustion Duration ◽  
Rate Of Heat Release ◽  
Operational Constraints

The intensity and structure of in-cylinder turbulence is known to have a significant effect on internal combustion engine performance. Changes in flow structure and turbulence intensity result in changes to the rate of heat release, cylinder wall heat rejection, and cycle-to-cycle combustion variability. This paper seeks to quantify these engine performance consequences and identify fundamental similarities across a range of high-speed, medium-bore, lean-burn, spark-ignited reciprocating engines. In-cylinder turbulence was manipulated by changing the extent of intake port-induced swirl as well as varying the level of piston-generated turbulence. The relationship between in-cylinder turbulence and engine knock is also discussed. Increasing in-cylinder turbulence generally reduces combustion duration, but test results reveal that increasing swirl beyond a critical point can cause a lengthening of burn durations and greatly reduced engine performance. This critical swirl level is related to the extent of small-scale, piston-generated turbulence present in the cylinder. Increasing in-cylinder turbulence generally leads to reduced cycle-to-cycle variability and increased detonation margin (DM). The overall change in thermal efficiency was dependent on the balance of these factors and wall heat transfer, and varied depending on the operational constraints for a given engine and application. Single cylinder engine test data, supported with three-dimensional computational fluid dynamics (CFD) results, are used to demonstrate and explain these basic combustion engine principles.

Engine Capability Prediction for SI Engine Fueled With Syngas

2015 ◽  
Author(s):  
Hui Xu ◽  
Leon A. LaPointe
Keyword(s):  
Natural Gas ◽  
Solid Waste ◽  
Laminar Flame ◽  
Combustion Engine ◽  
Flame Temperature ◽  
Engine Performance ◽  
Nox Emissions ◽  
Lean Burn ◽  
Gaseous Fuels ◽  
Combustion Duration

There are increasing interests in converting solid waste or lignocellulosic biomass into gaseous fuels and using reciprocating internal combustion engine to generate electricity. A widely used technique is gasification. Gasification is a process where the solid fuel and air are introduced to a partial oxidation environment, and generate combustible gaseous called synthesis gas or syngas. Converting solid waste into gaseous fuel can reduce landfill and create income for process owners. However it can be very challenging to use syngas on a gaseous fueled spark ignited engine, such as a natural gas (NG) engine. NG engines are typically developed with pipeline quality natural gas (PQNG). NG engines can operate at lean burn spark ignited (LBSI), or stoichiometric with EGR spark ignited (SESI) conditions. This work discusses the LBSI engine condition. NG engines can perform very differently when fueled with nonstandard gaseous fuels such as syngas without appropriate tuning. It is necessary to evaluate engine performance in terms of combustion duration, relative knock propensity and NOx emissions for such applications. Due to constraints in time and resources it is often not feasible to test such fuel blends in the laboratory. An analytical method is needed to predict engine performance in a timely manner. This study investigated the possibility of using syngas on a spark ignited engine developed with PQNG. Engine performance was predicted using in house developed models and PQNG as the reference fuel. Laminar flame speed (LFS), adiabatic flame temperature (AFT) and Autoignition interval (AI) are used to predict combustion duration, engine out NOx and engine knock propensity relative to NG at the target Lambda values. Single cylinder research engine data obtained under lean burn conditions fueled with PQNG was selected as the baseline. LFS, AFT and AI of syngas were computed at reference conditions. Lambda of operation was predicted for syngas to provide the same burn rate as NG at the reference Lambda value for NG. Analysis shows that, using syngas at the selected Lambda, the engine can have less engine out NOx emissions and less knock propensity relative to NG at the same speed and load. Modifications to fuel system components may be required to avoid engine derate.

Flow Simulation in Port and Cylinder of a Small Motorcycle Engine With Inclined Valve

2003 ◽  
Author(s):  
Ma-Ji Luo ◽  
Zhen Huang ◽  
Guo-Hua Chen ◽  
Yuan-Hao Ma
Keyword(s):  
High Speed ◽  
Model Comparison ◽  
Combustion Engine ◽  
Three Dimensional ◽  
Engine Performance ◽  
Flow Simulation ◽  
The Body ◽  
Cylinder Pressure ◽  
Cylinder Flow ◽  
Motorcycle Engine

The in-cylinder flow of an internal combustion engine has great effect on the major engine performance characteristics. To understand the complex intake phenomena in a small high-speed two-valve-per-cylinder motorcycle engine, a numerical analytic model based on the KIVA-3 code is developed for the three-dimensional transient intake flow, including a moving piston and a moving inclined intake valve. The valve model adopts the body-fitted technique and the dynamic grids induced by the moving valve are automatically generated by the grid remeshing method. Turbulence is represented by k-ε model. Comparison with the measured engine cylinder pressure shows that the simulation result is generally in good agreement with the experiment. The calculated results reveal the formation of the in-cylinder tumble motion, the variation of tumble ratios, turbulence kinetic energy and the cylinder pressure. The effects of engine speeds on the intake process are also investigated. The simulation results provide important information for the design of engine intake system.

Engine Capability Prediction for Spark Ignited Engine Fueled With Syngas

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Hui Xu ◽  
Leon A. LaPointe
Keyword(s):  
Natural Gas ◽  
Solid Waste ◽  
Combustion Engine ◽  
Flame Temperature ◽  
Engine Performance ◽  
Nox Emissions ◽  
Si Engine ◽  
Lean Burn ◽  
Gaseous Fuels ◽  
Combustion Duration

Abstract There are increasing interests in converting solid waste or lignocellulosic biomass into gaseous fuels and using reciprocating internal combustion engine to generate electricity. A widely used technique is gasification. Gasification is a process where the solid fuel and air are introduced to a partial oxidation environment, and generate combustible gaseous called synthesis gas or syngas. Converting solid waste into gaseous fuel can reduce landfill and create income for process owners. However, it can be very challenging to use syngas on a gaseous fueled spark ignited (SI) engine, such as a natural gas (NG) engine. NG engines are typically developed with pipeline quality natural gas (PQNG). NG engines can operate at lean burn spark ignited (LBSI), or stoichiometric with exhaust gas recirculation (EGR) spark ignited (SESI) conditions. This work discusses the LBSI engine condition. NG engines can perform very differently when fueled with nonstandard gaseous fuels such as syngas without appropriate tuning. It is necessary to evaluate engine performance in terms of combustion duration, relative knock propensity, and NOx emissions for such applications. Due to constraints in time and resources it is often not feasible to test such fuel blends in the laboratory. An analytical method is needed to predict engine performance in a timely manner. This study investigated the possibility of using syngas on an SI engine developed with PQNG. Engine performance was predicted using in house developed models and PQNG as the reference fuel. Laminar flame speed (LFS), adiabatic flame temperature (AFT), and auto-ignition interval (AI) are used to predict combustion duration, engine out NOx and engine knock propensity relative to NG at the target lambda values. Single cylinder research engine data obtained under lean burn conditions fueled with PQNG was selected as the baseline. LFS, AFT, and AI of syngas were computed at reference conditions. Lambda of operation was predicted for syngas to provide the same burn rate as NG at the reference lambda value for NG. Analysis shows that, using syngas at the selected lambda, the engine can have less engine out NOx emissions and less knock propensity relative to NG at the same speed and load. Modifications to fuel system components may be required to avoid engine derate.

Induction System Effects on Small-Scale Turbulence in a High-Speed Diesel Engine

1987 ◽  
Vol 109 (4) ◽  
pp. 491-502 ◽  
Author(s):  
A. E. Catania ◽  
A. Mittica
Keyword(s):  
Diesel Engine ◽  
Turbulence Intensity ◽  
High Speed ◽  
Engine Speed ◽  
Small Scale ◽  
Cylinder Wall ◽  
System Configuration ◽  
Intake System ◽  
Induction System ◽  
Scale Turbulence

The influence of the induction system on small-scale turbulence in a high-speed, automotive diesel engine was investigated under variable swirl conditions. The induction system was made up of two equiverse swirl tangential ducts, and valves of the same size and lift. Variable swirl conditions were obtained by keeping one of the inlet valves either closed or functioning, and by changing engine speed. The investigation was carried out for two induction system configurations: with both ducts operating and with only one of them operating. Two different engine speeds were considered, one relatively low (1600 rpm) and the other quite high (3000 rpm), the latter being the highest speed at which engine turbulence has been measured up to now. Cycle-resolved hot-wire anemometry measurements of air velocity were performed throughout the induction and compression strokes, under motored conditions, along a radial direction at an axial level that was virtually in the middle of the combustion chamber at top dead center. The velocity data were analyzed using the nonstationary time-averaging procedure previously developed by the authors. Correlation and spectral analysis of the small-scale turbulence so determined was also performed. The turbulence intensity and its degree of nonhomogeneity and anisotropy were sensibly influenced by the variable swirl conditions, depending on both the intake system configuration and engine speed; they generally showed an increase with increasing swirl intensity, at the end of the compression stroke. A similar trend was observed in the cyclic fluctuation of both the mean velocity and turbulence intensity. The micro time scale of turbulence was found to be almost uniform during induction and compression, showing a slight dependence on the measurement point and on the intake system configuration, but a more sensible dependence on the engine speed. No effect of the cylinder wall on turbulence was apparent.

A Novel One-Dimensional–Three-Dimensional Coupled Method to Predict Surge Boundary of Centrifugal Compressors

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Meijie Zhang ◽  
Xinqian Zheng ◽  
Qiangqiang Huang ◽  
Zhenzhong Sun
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Tangential Velocity ◽  
Engine Performance ◽  
Simulation Method ◽  
Dynamic Force ◽  
Centrifugal Compressors ◽  
Compression System ◽  
One Dimensional ◽  
Coupled Method

Compression systems are widely employed in gas turbine engines, turbocharged engines, and industry compression plants. The stable work of compression systems is an essential precondition for engine performance and safety. A compression system in practice usually consists of upstream and downstream pipes, compressors, plenums and throttles. When a compression system encounters the surge, the flows in the compressor present complex three-dimensional patterns but the flows of other components might present relatively simple one-dimensional patterns. Based on these flow characteristics, this paper proposes a novel simulation method, where one-dimensional and three-dimensional (1D–3D) calculations are coupled, to predict the surge boundary of centrifugal compressors. To validate this method, a high-speed centrifugal compressor is studied both by the proposed 1D–3D coupled method and experimentally. The results show that the differences between the predicted and experimentally determined stable flow range are lower than 5% until the Mach number of blade outlet tip tangential velocity reaches around 1.3. Besides, this method can correctly predict the instantaneous compressor performance during the surge cycle, so it can also be used to explore the surge mechanism and evaluate the blade dynamic force response in the future.

scholarly journals Study of dynamic underwater implosion mechanics using digital image correlation

2014 ◽  
Vol 470 (2172) ◽  
pp. 20140576 ◽  
Author(s):  
Sachin Gupta ◽  
Venkitanarayanan Parameswaran ◽  
Michael A. Sutton ◽  
Arun Shukla
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Three Dimensional ◽  
Image Correlation ◽  
Small Scale ◽  
Pressure History ◽  
Time Deformation ◽  
Rate Of Increase ◽  
Cylindrical Tubes

The physical processes associated with the implosion of cylindrical tubes in a hydrostatic underwater environment were investigated using high-speed three-dimensional digital image correlation (3D DIC). This study emphasizes visualization and understanding of the real-time deformation of the implodable volume and the associated fluid–structure interaction phenomena. Aluminium 6061-T6 cylindrical tubes were used as the implodable volumes. Dynamic tourmaline pressure transducers were placed at selected locations to capture the pressure history generated during each implosion event. A series of small-scale calibration experiments were first performed to establish the applicability of 3D DIC for measuring the deformation of submerged objects. The results of these experiments indicated that the effects of refraction due to water and the optical windows can be accounted for by evaluation of the camera's intrinsic and extrinsic parameters using a submerged calibration grid when the surface normal of the optical windows is collinear with the camera's optical axis. Each pressure history was synchronized with its respective high-speed DIC measurements. DIC results showed that the highest rate of increase in contact area correlates to the largest pressure spike during the implosion process. The results also indicated that, for a given diameter, longer implodable volumes generated higher pressure spikes.

Effects of Humidity and Ambient Temperature on Engine Performance of Lean Burn Natural Gas Engines

2006 ◽  
Author(s):  
Andreas Wimmer ◽  
Eduard Schnessl
Keyword(s):  
Natural Gas ◽  
Fuel Consumption ◽  
Engine Performance ◽  
Optimal Operation ◽  
Nox Emission ◽  
Engine Fuel ◽  
Ambient Conditions ◽  
Lean Burn ◽  
Combustion Duration ◽  
Burn Rate

High demands are placed on large gas engines in the areas of performance, fuel consumption and emissions. In order to meet all these demands, it is necessary to operate the engine in its optimal range. At high engine loads the optimal operation range becomes narrower as the engine comes closer to the knocking or to the misfire limit. The ambient conditions are of increasing importance in this range of operation. Variations in humidity influence the engine’s burn rate characteristics. An increase in humidity reduces the burn rate and increases the combustion duration. This increase in combustion duration has the same effect as retarding the time of ignition. Thus the thermal efficiency is reduced. Additionally, the engine is more likely to misfire as humidity increases. The cylinder temperature affects the engine fuel efficiency, knocking, exhaust gas temperature and particularly NOx emission. An increase in manifold air temperature results in higher NOx emission, heat transfer and knocking tendency. To avoid knocking, the time of ignition must be retarded resulting in lower engine efficiency. In this paper the effects of changes in humidity and temperature of the intake air on engine performance were examined in a lean burn pre-chamber natural gas engine. Tests on a single cylinder research engine were carried out. Effects on knocking and misfire limit, NOx emissions and fuel consumption were investigated depending on engine load. The interpretation of the results was supported by an extended analysis of losses.

High-speed brightfield 3-D imaging and 3-D image analysis of thick and overlapped cell clusters in cytological preparations

1994 ◽  
Vol 52 ◽  
pp. 218-219
Author(s):  
Robert W. Mackin
Keyword(s):  
Image Analysis ◽  
High Speed ◽  
Three Dimensional ◽  
Image Data ◽  
Ccd Camera ◽  
Objective Lens ◽  
Array Processor ◽  
Vaginal Smears ◽  
Low Contrast ◽  
Computer Controlled

This paper presents two advances towards the automated three-dimensional (3-D) analysis of thick and heavily-overlapped regions in cytological preparations such as cervical/vaginal smears. First, a high speed 3-D brightfield microscope has been developed, allowing the acquisition of image data at speeds approaching 30 optical slices per second. Second, algorithms have been developed to detect and segment nuclei in spite of the extremely high image variability and low contrast typical of such regions. The analysis of such regions is inherently a 3-D problem that cannot be solved reliably with conventional 2-D imaging and image analysis methods.High-Speed 3-D imaging of the specimen is accomplished by moving the specimen axially relative to the objective lens of a standard microscope (Zeiss) at a speed of 30 steps per second, where the stepsize is adjustable from 0.2 - 5μm. The specimen is mounted on a computer-controlled, piezoelectric microstage (Burleigh PZS-100, 68/μm displacement). At each step, an optical slice is acquired using a CCD camera (SONY XC-11/71 IP, Dalsa CA-D1-0256, and CA-D2-0512 have been used) connected to a 4-node array processor system based on the Intel i860 chip.

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