Design of a Stepped Tube Exhaust Primary for High Performance Applications Using Unsteady Computational Fluid Dynamics

ASME 2012 Internal Combustion Engine Division Fall Technical Conference ◽

10.1115/icef2012-92102 ◽

2012 ◽

Author(s):

Justin D. Callies ◽

David E. Anderson ◽

Robert G. Prucka

Keyword(s):

Gas Exchange ◽

High Performance ◽

Internal Combustion Engines ◽

Exchange Process ◽

Pressure Waves ◽

Step Size ◽

Exchange Performance ◽

Effective Use ◽

Performance Gains ◽

Scavenging Efficiency

High performance naturally-aspirated internal combustion engines require effective use of exhaust pressure waves during the gas exchange process to maximize volumetric efficiency and torque. Under certain conditions sudden increases, or steps, in exhaust runner diameter are used to control pressure wave reflections to provide appropriately timed low pressure waves to the cylinder that reduce pumping work and improve air scavenging. This research evaluates gas exchange performance for an exhaust port and an attached stepped-tube primary using unsteady conditions with 1-D and 3-D CFD. The objectives of this research are to (1) discuss the importance of using unsteady flow simulations in the design of high performance exhaust systems, (2) describe the use of stepped-runners to provide performance gains, and (3) discuss the influence of runner step geometry and the number of steps on gas exchange. Simulations are correlated with experimental data to ensure accuracy of the results. A correlation is found between the step size and the magnitude as well as phase of tuning effects. The number of steps is also found to have a direct impact on tuning. The pumping work of the cycle was significantly affected by the stepped primary design, while the scavenging efficiency was not.

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

International Journal of Engine Research ◽

10.1177/14680874211036613 ◽

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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Modifications to the Method of Characteristics for the Analysis of the Gas Exchange Process in Internal Combustion Engines

Proceedings of the Institution of Mechanical Engineers Part D Transport Engineering ◽

10.1243/pime_proc_1986_200_189_02 ◽

1986 ◽

Vol 200 (4) ◽

pp. 259-266 ◽

Cited By ~ 17

Author(s):

F Payri ◽

J M Corberán ◽

F Boada

Keyword(s):

Gas Exchange ◽

Internal Combustion Engines ◽

Method Of Characteristics ◽

Exchange Process ◽

Internal Combustion ◽

Linear Interpolation ◽

Combustion Engines ◽

The Method Of Characteristics ◽

Grid Points ◽

Gas Exchange Process

Some modifications to the method of characteristics for the analysis of the gas exchange process in internal combustion engines are presented in this paper. The modifications are related to the calculation of the path lines and the Riemann characteristic lines at the grid points. Regarding the path lines, the algorithm for the generation and elimination of path lines has been improved, mainly for the cases in which the fluid motion passes from being null or going out of the pipe to going into the pipe. In those cases the algorithm proposed by Benson can cause some mistakes in the entropy level field of the duct. An alternative method is proposed: the duplication ofpath lines. The other modifcation proposed is related to assuming a linear interpolation for the pressure and the volume flowrate between the nearest grid points, rather than assuming a linear interpolation of the value of the Riemann characteristics. These modijcations substantially improve the results obtained in the calculation of the fluid flow in manifolds of reciprocating internal combustion engines.

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Paper 11: Computing the Gas Exchange Process of Pressure Charged Internal Combustion Engines

Proceedings of the Institution of Mechanical Engineers Conference Proceedings ◽

10.1243/pime_conf_1967_182_364_02 ◽

1967 ◽

Vol 182 (12) ◽

pp. 109-118 ◽

Cited By ~ 3

Author(s):

M. Ryti

Keyword(s):

Gas Exchange ◽

Internal Combustion Engines ◽

Exchange Process ◽

Computing Time ◽

Linear Wave ◽

Combustion Engines ◽

Practical Application ◽

Wide Range ◽

Gas Exchange Process ◽

Wave Phenomena

Numerous problems associated with pressure charging can only be solved numerically by analysing the gas exchange process. The extensive practical application of step by step calculations of the process has only become possible with the advent of digital computers. For fundamental investigations the data provided by quasi-steady-state calculations are quite adequate, the amount of computing time being only a fraction of that needed for calculations in which allowance is made for non-linear wave phenomena. The Turbocharger Department of Brown Boveri utilizes a digital computer for calculations involving the gas exchange process in conjunction with its consulting activity for the benefit of customers. The program can be adapted to solve a very wide range of problems. The procedure is briefly described and possible applications discussed with reference to the following practical examples. Optimization of valve timing. Assessment of the results from various aspects. Performance and design for high pressure turbocharging and for high-altitude installations. Two-stage turbocharging. Mixture control for dual-fuel and gas engines.

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Experimental investigation of scavenging in two-stroke engines using continuous CO2 sampling

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1177/09544070211041329 ◽

2021 ◽

pp. 095440702110413

Author(s):

Abdullah U Bajwa ◽

Mark Patterson ◽

Timothy J Jacobs

Keyword(s):

Gas Exchange ◽

Equivalence Ratio ◽

Internal Combustion Engines ◽

Combustion Products ◽

Exhaust Emissions ◽

Residual Fraction ◽

Simultaneous Occurrence ◽

Operation Speed ◽

Residual Gas ◽

Scavenging Efficiency

In internal combustion engines, the chemical composition of the trapped fuel-air-residual gas mixture controls the nature of combustion, which, in turn, determines the characteristics of the ensuing emissions and work production processes. Therefore, knowledge of the trapped mixture’s composition is critical for reliably predicting and controlling engine performance, emissions, and efficiency. A good index of the overall trapped mixture composition is the trapped equivalence ratio. Unfortunately, in two-stroke engines, it is unfeasible to accurately determine the trapped equivalence ratio using traditional intake flow measurements and exhaust emissions data. This limitation arises from the simultaneous occurrence of intake and exhaust processes in two-stroke engines, which causes: (1) exhaust emissions to be diluted by excess fresh air that was supplied for achieving effective gas exchange, that is trapping inefficiencies and (2) a significant fraction of combustion products to stay back in the cylinder as residual gas, that is scavenging inefficiencies. The current paper presents an experimental study carried out on a cross-scavenged, lean-burn, natural-gas, two-stroke engine to characterize its scavenging performance, thus paving the way for trapped equivalence ratio computation. CO2 is used as a tracer for combustion products, and its concentration is tracked in the combustion chamber and exhaust manifold on a crank-angle-resolved basis using high-speed nondispersive infrared sensors. The changes in cylinder CO2 concentration before and after gas exchange are used to determine the trapped residual fraction and various features of the exhaust CO2“wave” are used to explain the temporal progression of the gas exchange process. The presented results show the effects of changes in engine operation (speed, load, and spark-timing) on the engine’s scavenging efficiency. Speed and load changes are found to have the most pronounced effects, which result from changes in port open duration and phasing of reflected waves in the exhaust.

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A high-fidelity realization of the Euclid code comparison N-body simulation with Abacus

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz634 ◽

2019 ◽

Vol 485 (3) ◽

pp. 3370-3377 ◽

Cited By ~ 8

Author(s):

Lehman H Garrison ◽

Daniel J Eisenstein ◽

Philip A Pinto

Keyword(s):

Power Spectrum ◽

High Performance ◽

High Fidelity ◽

Step Size ◽

Time Step ◽

Code Comparison ◽

Force Accuracy ◽

Integration Errors ◽

Better Than ◽

Good Agreement

Abstract We present a high-fidelity realization of the cosmological N-body simulation from the Schneider et al. code comparison project. The simulation was performed with our AbacusN-body code, which offers high-force accuracy, high performance, and minimal particle integration errors. The simulation consists of 20483 particles in a $500\ h^{-1}\, \mathrm{Mpc}$ box for a particle mass of $1.2\times 10^9\ h^{-1}\, \mathrm{M}_\odot$ with $10\ h^{-1}\, \mathrm{kpc}$ spline softening. Abacus executed 1052 global time-steps to z = 0 in 107 h on one dual-Xeon, dual-GPU node, for a mean rate of 23 million particles per second per step. We find Abacus is in good agreement with Ramses and Pkdgrav3 and less so with Gadget3. We validate our choice of time-step by halving the step size and find sub-percent differences in the power spectrum and 2PCF at nearly all measured scales, with ${\lt }0.3{{\ \rm per\ cent}}$ errors at $k\lt 10\ \mathrm{Mpc}^{-1}\, h$. On large scales, Abacus reproduces linear theory better than 0.01 per cent. Simulation snapshots are available at http://nbody.rc.fas.harvard.edu/public/S2016.

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Alterations in Gas Exchange and Oxidative Metabolism in Rice Leaves Infected by Pyricularia oryzae are Attenuated by Silicon

Phytopathology ◽

10.1094/phyto-10-14-0280-r ◽

2015 ◽

Vol 105 (6) ◽

pp. 738-747 ◽

Cited By ~ 26

Author(s):

Gisele Pereira Domiciano ◽

Isaías Severino Cacique ◽

Cecília Chagas Freitas ◽

Marta Cristina Corsi Filippi ◽

Fábio Murilo DaMatta ◽

...

Keyword(s):

Gas Exchange ◽

Photochemical Efficiency ◽

Pyricularia Oryzae ◽

Gas Exchange Parameters ◽

Photosynthetic Gas Exchange ◽

Exchange Performance ◽

Rice Leaves ◽

Maximum Photochemical Efficiency ◽

Important Disease ◽

Exchange Parameters

Rice blast, caused by Pyricularia oryzae, is the most important disease in rice worldwide. This study investigated the effects of silicon (Si) on the photosynthetic gas exchange parameters (net CO2 assimilation rate [A], stomatal conductance to water vapor [gs], internal-to-ambient CO2 concentration ratio [Ci/Ca], and transpiration rate [E]); chlorophyll fluorescence a (Chla) parameters (maximum photochemical efficiency of photosystem II [Fv/Fm], photochemical [qP] and nonphotochemical [NPQ] quenching coefficients, and electron transport rate [ETR]); concentrations of pigments, malondialdehyde (MDA), and hydrogen peroxide (H2O2); and activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), and lypoxigenase (LOX) in rice leaves. Rice plants were grown in a nutrient solution containing 0 or 2 mM Si (−Si or +Si, respectively) with and without P. oryzae inoculation. Blast severity decreased with higher foliar Si concentration. The values of A, gs and E were generally higher for the +Si plants in comparison with the −Si plants upon P. oryzae infection. The Fv/Fm, qp, NPQ, and ETR were greater for the +Si plants relative to the −Si plants at 108 and 132 h after inoculation (hai). The values for qp and ETR were significantly higher for the –Si plants in comparison with the +Si plants at 36 hai, and the NPQ was significantly higher for the –Si plants in comparison with the +Si plants at 0 and 36 hai. The concentrations of Chla, Chlb, Chla+b, and carotenoids were significantly greater in the +Si plants relative to the –Si plants. For the –Si plants, the MDA and H2O2 concentrations were significantly higher than those in the +Si plants. The LOX activity was significantly higher in the +Si plants than in the –Si plants. The SOD and GR activities were significantly higher for the –Si plants than in the +Si plants. The CAT and APX activities were significantly higher in the +Si plants than in the –Si plants. The supply of Si contributed to a decrease in blast severity, improved the gas exchange performance, and caused less dysfunction at the photochemical level.

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Gas Exchange Process of Four-Stroke Spark Ignition Engines under the Condition of Partial Load at Medium or Low Speed : 4th Report

Bulletin of JSME ◽

10.1299/jsme1958.23.561 ◽

1980 ◽

Vol 23 (178) ◽

pp. 561-566

Author(s):

Hidenori TSAKA ◽

Shin MATSUOKA

Keyword(s):

Gas Exchange ◽

Exchange Process ◽

Spark Ignition ◽

Spark Ignition Engines ◽

Low Speed ◽

Partial Load ◽

Gas Exchange Process

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Desulfurization Behavior of Incoloy® 825 Superalloy by CaO-Al2O3-MgO-TiO2 Slag

Metallurgical and Materials Transactions B ◽

10.1007/s11663-021-02338-9 ◽

2021 ◽

Author(s):

Jin Hyung Cho ◽

Johan Martinsson ◽

Du Sichen ◽

Joo Hyun Park

Keyword(s):

Mass Transfer ◽

Transfer Coefficient ◽

Mass Transfer Coefficient ◽

Nuclear Power ◽

High Performance ◽

Internal Combustion Engines ◽

Sulfide Capacity ◽

Metal Phase ◽

High Temperature Strength ◽

Desulfurization Rate

AbstractNi-based superalloy, which has excellent high-temperature strength and corrosion resistance, is mainly used in aviation materials, high-performance internal combustion engines, and turbines for thermal and nuclear power generation. For this reason, refining the impurities in Ni-based superalloys is a very important technical task. Nevertheless, the original technology for the melting and refining of Ni-based superalloys is still insufficient. Therefore, in this study, the effect of the CaO-Al2O3-MgO-TiO2 slag on the removal efficiency of an impurity element sulfur in Incoloy® 825 superalloy, one of the representative Ni-based superalloys, was investigated. The desulfurization behavior according to the change of TiO2 content and CaO/Al2O3 (=C/A, basicity) ratio as experimental variables was observed at 1773 K (1500 °C). Although the TiO2 content in the slag increases to 15 mass pct, the mass transfer coefficient of sulfur in molten alloy showed a constant value. Alternatively, under the condition of C/A > 1.0 of slag, the mass transfer coefficient of sulfur showed a constant value, whereas under the condition of C/A < 1.0, the mass transfer coefficient of sulfur greatly decreased as CaO decreased. Hence, in the desulfurization of Incoloy® 825 superalloy using the CaO-Al2O3-MgO-TiO2 slag, the TiO2 content in the slag does not have a considerable effect on the desulfurization rate and desulfurization mechanism (metal phase mass transfer controlled regime), but the basicity of the slag has a significant effect on desulfurization mechanism. When the slag basicity decreases below the critical level, i.e., C/A < 1.0, which is corresponding to sulfur distribution ratio, Ls < 200, it was confirmed that the desulfurization mechanism shifts from the metal phase mass transfer-controlled regime to the slag phase mass transfer-controlled regime due to the variation in the physicochemical properties of the slag such as viscosity and sulfide capacity. In addition, the different desulfurization rates between steel and Ni alloy melts were discussed by employing the diffusivity of sulfur in both systems.

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