Development of a Semi-implicit Solver for Detailed Chemistry in Internal Combustion Engine Simulations

2006 ◽  
Vol 129 (1) ◽  
pp. 271-278 ◽  
Author(s):  
Long Liang ◽  
Song-Charng Kong ◽  
Chulhwa Jung ◽  
Rolf D. Reitz
Keyword(s):  
Internal Combustion ◽  
Operating Conditions ◽  
Explicit Methods ◽  
Time Step ◽  
Ic Engine ◽  
Specific Internal Energy ◽  
Detailed Chemistry ◽  
Key Species ◽  
Wide Range ◽  
Implicit Solver

An efficient semi-implicit numerical method is developed for solving the detailed chemical kinetic source terms in internal combustion (IC) engine simulations. The detailed chemistry system forms a group of coupled stiff ordinary differential equations (ODEs), which presents a very stringent time-step limitation when solved by standard explicit methods, and is computationally expensive when solved by iterative implicit methods. The present numerical solver uses a stiffly stable noniterative semi-implicit method. The formulation of numerical integration exploits the physical requirement that the species density and specific internal energy in the computational cells must be non-negative, so that the Lipschitz time-step constraint is not present and the computation time step can be orders of magnitude larger than that possible in standard explicit methods. The solver exploits the characteristics of the stiffness of the ODEs by using a sequential sort algorithm that ranks an approximation to the dominant eigenvalues of the system to achieve maximum accuracy. Subcycling within the chemistry solver routine is applied for each computational cell in engine simulations, where the subcycle time step is dynamically determined by monitoring the rate of change of concentration of key species, which have short characteristic time scales and are also important to the chemical heat release. The chemistry solver is applied in the KIVA-3V code to diesel engine simulations. Results are compared to those using the CHEMKIN package, which uses the VODE implicit solver. Good agreement was achieved for a wide range of engine operating conditions, and 40-70% CPU time savings were achieved by the present solver compared to the standard CHEMKIN.

Development of a Semi-Implicit Solver for Detailed Chemistry in I.C. Engine Simulations

2005 ◽  
Author(s):  
Long Liang ◽  
Chulhwa Jung ◽  
Song-Charng Kong ◽  
Rolf D. Reitz
Keyword(s):  
Chemical Kinetic ◽  
Rate Of Change ◽  
Operating Conditions ◽  
Explicit Methods ◽  
Implicit Methods ◽  
Specific Internal Energy ◽  
Detailed Chemistry ◽  
Key Species ◽  
Wide Range ◽  
Implicit Solver

An efficient semi-implicit numerical method is developed for solving the detailed chemical kinetic source terms in I.C. engine simulations. The detailed chemistry system is a group of coupled extremely stiff O.D.E.s, which presents a very stringent timestep limitation when solved by standard explicit methods, and is computationally expensive when solved by iterative implicit methods. The present numerical solver uses a stiffly-stable noniterative semi-implicit method, in which the numerical solution to the stiff O.D.E.s never blows up for arbitrary large timestep. The formulation of numerical integration exploits the physical requirement that the species density and specific internal energy in the computational cells must be nonnegative, so that the Lipschitz timestep constraint is not present [1,2], and the computation timestep can be orders of magnitude larger than that possible in standard explicit methods and can be formulated to be of high formal order of accuracy. The solver exploits the characteristics of the stiffness of the O.D.E.s by using a sequential sort algorithm that ranks an approximation to the dominant eigenvalues of the system to achieve maximum accuracy. Subcycling within the chemistry solver routine is applied for each computational cell in engine simulations, where the subcycle timestep is dynamically determined by monitoring the rate of change of concentration of key species which have short characteristic time scales and are also important to the chemical heat release. The chemistry solver is applied in the KIVA-3V code to diesel engine simulations. Results are compared with those using the CHEMKIN package which uses the VODE implicit solver. Very good agreement was achieved for a wide range of engine operating conditions, and 40∼70% CPU time savings were achieved by the present solver compared to CHEMKIN.

Ethers and esters as alternative fuels for internal combustion engine: A review

2021 ◽  
pp. 146808742110464
Author(s):  
Yang Hua
Keyword(s):  
Alternative Fuels ◽  
Combustion Engine ◽  
Combustion Process ◽  
Pressure Rise ◽  
Engine Performance ◽  
Internal Combustion ◽  
Operating Conditions ◽  
Future Research ◽  
Particulate Emissions ◽  
Ic Engine

Ether and ester fuels can work in the existing internal combustion (IC) engine with some important advantages. This work comprehensively reviews and summarizes the literatures on ether fuels represented by DME, DEE, DBE, DGM, and DMM, and ester fuels represented by DMC and biodiesel from three aspects of properties, production and engine application, so as to prove their feasibility and prospects as alternative fuels for compression ignition (CI) and spark ignition (SI) engines. These studies cover the effects of ether and ester fuels applied in the form of single fuel, mixed fuel, dual-fuel, and multi-fuel on engine performance, combustion and emission characteristics. The evaluation indexes mainly include torque, power, BTE, BSFC, ignition delay, heat release rate, pressure rise rate, combustion duration, exhaust gas temperature, CO, HC, NOx, PM, and smoke. The results show that ethers and esters have varying degrees of impact on engine performance, combustion and emissions. They can basically improve the thermal efficiency of the engine and reduce particulate emissions, but their effects on power, fuel consumption, combustion process, and CO, HC, and NOx emissions are uncertain, which is due to the coupling of operating conditions, fuel molecular structure, in-cylinder environment and application methods. By changing the injection strategy, adjusting the EGR rate, adopting a new combustion mode, adding improvers or synergizing multiple fuels, adverse effects can be avoided and the benefits of oxygenated fuel can be maximized. Finally, some challenges faced by alternative fuels and future research directions are analyzed.

Unsteady Conjugate Heat Transfer Investigation of a Multistage Steam Turbine in Warm-Keeping Operation With Hot Air

2018 ◽  
Author(s):  
Piotr Łuczyński ◽  
Dennis Toebben ◽  
Manfred Wirsum ◽  
Wolfgang F. D. Mohr ◽  
Klaus Helbig
Keyword(s):  
Heat Transfer ◽  
Conjugate Heat Transfer ◽  
Flow Patterns ◽  
Operating Conditions ◽  
Angle Of Incidence ◽  
Time Step ◽  
Hot Air ◽  
Wide Range ◽  
Vortex Systems ◽  
Operating Points

In recent decades, the rising share of commonly subsidized renewable energy especially affects the operational strategy of conventional power plants. In pursuit of flexibility improvements, extension of life cycle, in addition to a reduction in start-up time, General Electric has developed a product to warm-keep high/intermediate pressure steam turbines using hot air. In order to optimize the warm-keeping operation and to gain knowledge about the dominant heat transfer phenomena and flow structures, detailed numerical investigations are required. Considering specific warm-keeping operating conditions characterized by high turbulent flows, it is required to conduct calculations based on time-consuming unsteady conjugate heat transfer (CHT) simulations. In order to investigate the warm-keeping process as found in the presented research, single and multistage numerical turbine models were developed. Furthermore, an innovative calculation approach called the Equalized Timescales Method (ET) was applied for the modeling of unsteady conjugate heat transfer (CHT). The unsteady approach improves the accuracy of the stationary simulations and enables the determination of the multistage turbine models. In the course of the research, two particular input variables of the ET approach — speed up factor (SF) and time step (TS) — have been additionally investigated with regard to their high impact on the calculation time and the quality of the results. Using the ET method, the mass flow rate and the rotational speed were varied to generate a database of warm-keeping operating points. The main goal of this work is to provide a comprehensive knowledge of the flow field and heat transfer in a wide range of turbine warm-keeping operations and to characterize the flow patterns observed at these operating points. For varying values of flow coefficient and angle of incidence, the secondary flow phenomena change from well-known vortex systems occurring in design operation (such as passage, horseshoe and corner vortices) to effects typical for windage, like patterns of alternating vortices and strong backflows. Furthermore, the identified flow patterns have been compared to vortex systems described in cited literature and summarized in the so-called blade vortex diagram. The comparison of heat transfer in the form of charts showing the variation of the Nusselt-numbers with respect to changes in angle of incidence and flow coefficients at specific operating points is additionally provided.

Effect of IC Engine Operating Conditions on Combustion and Emission Characteristics

1993 ◽  
Vol 115 (4) ◽  
pp. 694-701 ◽  
Author(s):  
Jiang Lu ◽  
Ashwani K. Gupta ◽  
Eugene L. Keating
Keyword(s):  
Internal Combustion Engine ◽  
Combustion Chamber ◽  
Internal Combustion Engines ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Operating Conditions ◽  
Emission Characteristics ◽  
Ic Engine ◽  
Pollutants Emission ◽  
Good Agreement

Numerical simulation of flow, combustion, heat release rate, and pollutants emission characteristics have been obtained using a single cylinder internal combustion engine operating with propane as the fuel. The data show that for good agreement with experimental results on the peak pressure and the rate of pressure rise as a function of crank angle, spark ignition energy and local cylinder pressure must be properly modeled. The results obtained for NO and CO showed features which are qualitatively in good agreement and are similar to those reported in the literature for the chosen combustion chamber geometry. The results have shown that both the combustion chamber geometry and engine operating parameters affects the flame growth within the combustion chamber which subsequently affects the pollutants emission levels. The code employed the time marching procedure and solves the governing partial differential equations of multicomponent chemically reacting fluid flow by finite difference method. The numerical results provide a cost effective means of developing advanced internal combustion engine chamber geometry design that provides high efficiency and low pollution levels. It is expected that increased computational tools will be used in the future for enhancing our understanding of the detailed combustion process in internal combustion engines and all other energy conversion systems. Such detailed information is critical for the development of advanced methods for energy conservation and environmental pollution control.

Contactless Shaft Torque Detection for Wide Range Performance Measurement of Exhaust Gas Turbocharger Turbines

2013 ◽  
Vol 136 (6) ◽  
Author(s):  
Bernhardt Lüddecke ◽  
Dietmar Filsinger ◽  
Jan Ehrhard ◽  
Bastian Steinacher ◽  
Christian Seene ◽  
...  
Keyword(s):  
Internal Combustion Engine ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Sensitivity Study ◽  
Operating Conditions ◽  
Measuring System ◽  
Sensor Calibration ◽  
Torque Measurement ◽  
Wide Range ◽  
Shaft Torque

Turbochargers develop away from an auxiliary component—being “off the shelve”—towards an integrated component of the internal combustion engine. Hence, increased attention is paid to the accuracy of the measured turbine and compressor maps. Especially turbine efficiency measurement under engine-relevant operating conditions (pulsed flow) is recently receiving increased attention in the respective research community. Despite various turbine map extrapolation methods, sufficient accuracy of the input test data is indispensable. Accurate experimental data are necessary to achieve high quality extrapolation results, enabling a wide range and precise prediction of turbine behavior under unsteady flow conditions, determined by intermittent operation of the internal combustion engine. The present work describes the first application of a contactless shaft torque measurement technique—based on magnetostriction—to a small automotive turbocharger. The contactless torque measuring system is presented in detail and sensor principle as well as sensor calibration are illustrated. A sensitivity study regarding sensor position influences onto sensor signal proves the robustness and very good repeatability of the system. In the second part of the paper, steady state experimental results from operation on a conventional hot gas test stand over a wide map range are presented. These results are validated against full turbine stage (adiabatic as well as diabatic) CFD results as well as against “cold” efficiency measurements, based on measured inlet and outlet temperatures. The influence and relevance of bearing friction for such measurements is underlined and the improvements on this matter—achieved by direct torque measurement—are demonstrated.

scholarly journals Homogeneous Charge Compression Ignition Combustion: Challenges and Proposed Solutions

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Mohammad Izadi Najafabadi ◽  
Nuraini Abdul Aziz
Keyword(s):  
Homogeneous Charge Compression Ignition ◽  
Fuel Efficiency ◽  
Operating Conditions ◽  
Future Research ◽  
Compression Ignition ◽  
Ignition Timing ◽  
Ic Engine ◽  
Hcci Engine ◽  
Wide Range ◽  
Homogeneous Charge

Engine and car manufacturers are experiencing the demand concerning fuel efficiency and low emissions from both consumers and governments. Homogeneous charge compression ignition (HCCI) is an alternative combustion technology that is cleaner and more efficient than the other types of combustion. Although the thermal efficiency andNOxemission of HCCI engine are greater in comparison with traditional engines, HCCI combustion has several main difficulties such as controlling of ignition timing, limited power output, and weak cold-start capability. In this study a literature review on HCCI engine has been performed and HCCI challenges and proposed solutions have been investigated from the point view ofIgnition Timingthat is the main problem of this engine. HCCI challenges are investigated by many IC engine researchers during the last decade, but practical solutions have not been presented for a fully HCCI engine. Some of the solutions are slow response time and some of them are technically difficult to implement. So it seems that fully HCCI engine needs more investigation to meet its mass-production and the future research and application should be considered as part of an effort to achieve low-temperature combustion in a wide range of operating conditions in an IC engine.

Performance and Emissions Characteristics Investigation of a Bi-Fuel SI Engine Fuelled by CNG and Gasoline

2006 ◽  
Author(s):  
Abazar Shamekhi ◽  
Nima Khatibzadeh ◽  
Amir H. Shamekhi
Keyword(s):  
Internal Combustion Engines ◽  
Combustion Engine ◽  
Engine Performance ◽  
Internal Combustion ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Engine Fuel ◽  
Wide Range ◽  
Performance And Emissions ◽  
Pollutant Sources

Nowadays, increased attention has been focused on internal combustion engine fuels. Regarding environmental effects of internal combustion engines particularly as pollutant sources and depletion of fossil fuel resources, compressed natural gas (CNG) has been introduced as an effective alternative to gasoline and diesel fuel in many applications. A high research octane number allows combustion at higher compression ratios without knocking and good emission characteristics of HC and CO are major benefits of CNG as an engine fuel. In this paper, CNG as an alternative fuel in a spark ignition engine has been considered. Engine performance and exhaust emissions have been experimentally studied for CNG and gasoline in a wide range of the engine operating conditions.

Contactless Shaft Torque Detection for Wide Range Performance Measurement of Exhaust Gas Turbocharger Turbines

2013 ◽  
Author(s):  
Bernhardt Lüddecke ◽  
Dietmar Filsinger ◽  
Jan Ehrhard ◽  
Bastian Steinacher ◽  
Christian Seene ◽  
...  
Keyword(s):  
Internal Combustion Engine ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Sensitivity Study ◽  
Operating Conditions ◽  
Measuring System ◽  
Sensor Calibration ◽  
Torque Measurement ◽  
Wide Range ◽  
Shaft Torque

Turbochargers develop away from an auxiliary component — being “off the shelve” — towards an integrated component of the internal combustion engine. Hence, increased attention is paid to the accuracy of the measured turbine and compressor maps. Especially turbine efficiency measurement under engine-relevant operating conditions (pulsed flow) is recently receiving increased attention in the respective research community. Despite various turbine map extrapolation methods, sufficient accuracy of the input test data is indispensable. Accurate experimental data are necessary to achieve high quality extrapolation results, enabling a wide range and precise prediction of turbine behavior under unsteady flow conditions, determined by intermittent operation of the internal combustion engine. The present work describes the first application of a contactless shaft torque measurement technique — based on magnetostriction — to a small automotive turbocharger. The contactless torque measuring system is presented in detail and sensor principle as well as sensor calibration are illustrated. A sensitivity study regarding sensor position influences onto sensor signal proves the robustness and very good repeatability of the system. In the second part of the paper, steady state experimental results from operation on a conventional hot gas test stand over a wide map range are presented. These results are validated against full turbine stage (adiabatic as well as diabatic) CFD results as well as against “cold” efficiency measurements, based on measured inlet and outlet temperatures. The influence and relevance of bearing friction for such measurements is underlined and the improvements on this matter — achieved by direct torque measurement — are demonstrated.

Neural Network Based Automotive Clutch Model for Dynamic Engagement Analysis With Variable Time Steps

2000 ◽  
Author(s):  
M. Cao ◽  
K. W. Wang ◽  
Y. Fujii ◽  
W. E. Tobler
Keyword(s):  
Neural Network ◽  
Automatic Transmission ◽  
Operating Conditions ◽  
Hybrid Network ◽  
Time Step ◽  
Neural Network Approach ◽  
Time Pattern ◽  
Variable Time ◽  
Powertrain System ◽  
Wide Range

Abstract The lubricated clutch in an automatic transmission plays an important role in the performance and comfort of passenger vehicles. Therefore, an accurate and easy-to-implement dynamic clutch model is necessary for powertrain system design and performance studies. A neural network approach recently developed by Parvataneni et al. [1999] for clutch modeling has illustrated some very promising results. However, this model has complex architecture that may cause slow training and testing. Also, due to the lack of time information, the network cannot adapt to time step variations. Therefore, it cannot be easily integrated with powertrain system models, which in general require variable time steps for a superior numerical integration performance. In this paper, a new first-principle-based hybrid network clutch model is derived for dynamic engagement analysis with variable time steps. With improvement over the previous work by Parvataneni et al. [1999], the time pattern information is added to the inputs and a simpler architecture is developed through more explicit utilization of the physical laws. A second order training algorithm with dynamic derivatives is also used to improve the training efficiency and accuracy. With these new features, this model can significantly outperform the previous approach in terms of accuracy and efficiency. The network is trained and tested using experimental data as well as analytical results. It is shown that this new model can compensate for time step variations and can predict the clutch torque accurately for a wide range of operating conditions.

On the Sensitivity of the Asperity Pressures and Temperatures to the Fluid Pressure Distribution in Mixed-Film Lubrication

1999 ◽  
Vol 122 (1) ◽  
pp. 77-85 ◽  
Author(s):  
L. Chang ◽  
Yongwu Zhao
Keyword(s):  
Pressure Distribution ◽  
Fluid Pressure ◽  
Practical Interest ◽  
Operating Conditions ◽  
Asperity Contact ◽  
Time Duration ◽  
Time Step ◽  
Wide Range ◽  
Mixed Film ◽  
Film Lubrication

This paper studies the sensitivities of the asperity pressures and temperatures to the fluid pressure distribution in concentrated contacts operating in the regime of mixed-film lubrication. Two fluid pressure distributions are used in the study. One is a Hertz-like distribution that neglects micro-EHL responses of the lubricant, and the other models the micro-EHL effects with significant pressure rippling. The asperity pressures and temperatures are deterministically calculated in time by numerically solving the asperity-contact and the transient energy equations as the two surfaces move relative to each other. The contact is simulated for sufficient time duration until the samples of the calculated asperity variables reach a statistical equilibrium that reflects the random-process nature of the problem. Parametric analyses are carried out that cover a wide range of operating conditions of practical interest. The results obtained consistently suggest that the asperity pressures and temperatures are not sensitively related to the fluid pressure. This insensitivity supports the use of any fluid pressure distribution consistent with the underlying mixed-film problem, rather than determining it by numerically solving the Reynolds equation at every time step of the simulation process. The study lays a foundation on which to advance modeling of the mixed-film contacts with a proper balance among model robustness, computational efficiency and solution accuracy. [S0742-4787(00)01101-2]

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