Cycle Simulation of Coal Particle Fueled Reciprocating Internal-Combustion Engines

The thermodynamic limitation for the maximum efficiencies of internal combustion engines is an important consideration for the design and development of future engines. Knowing these limits helps direct resources to those areas with the most potential for improvements. Using an engine cycle simulation which includes the first and second laws of thermodynamics, this study has determined the fundamental thermodynamics that are responsible for these limits. This work has considered an automotive engine and has quantified the maximum efficiencies starting with the most ideal conditions. These ideal conditions included no heat losses, no mechanical friction, lean operation, and short burn durations. Then, each of these idealizations is removed in a step-by-step fashion until a configuration that represents current engines is obtained. During this process, a systematic thermodynamic evaluation was completed to determine the fundamental reasons for the limitations of the maximum efficiencies. For the most ideal assumptions, for compression ratios of 20 and 30, the thermal efficiencies were 62.5% and 66.9%, respectively. These limits are largely a result of the combustion irreversibilities. As each of the idealizations is relaxed, the thermal efficiencies continue to decrease. High compression ratios are identified as an important aspect for high-efficiency engines. Cylinder heat transfer was found to be one of the largest impediments to high efficiency. Reducing cylinder heat transfer, however, is difficult and may not result in much direct increases of piston work due to decreases of the ratio of specific heats. Throughout this work, the importance of high values of the ratio of specific heats was identified as important for achieving high thermal efficiencies. Depending on the selection of constraints, different values may be given for the maximum thermal efficiency. These constraints include the allowed values for compression ratio, heat transfer, friction, stoichiometry, cylinder pressure, and pressure rise rate.

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CENTRIFUGAL COMPRESSOR PERFORMANCE MAPS TREATMENT FOR INTERNAL COMBUSTION ENGINES OPERATING CYCLE SIMULATION

Internal Combustion Engines ◽

10.20998/0419-8719.2021.1.02 ◽

2021 ◽

pp. 9-15

Author(s):

D. Minchev ◽

R. Varbanets

Keyword(s):

Centrifugal Compressor ◽

Internal Combustion Engines ◽

Internal Combustion ◽

Rotating Stall ◽

Combustion Engines ◽

Operating Cycle ◽

Stable Mode ◽

Cycle Simulation ◽

Compressor Surge ◽

Compressor Performance

Simulation of the supercharged internal combustion engines operation cycle is impossible without correct estimation of the supercharger operating parameters. Standard approach is to use specially prepared performance maps of compressor and turbine of the turbocharger, which are based on the experimental (or manufacturer’s) raw data. Centrifugal compressor performance maps interpolation, extrapolation and treatment provides challenging requirements as it is important to get correct simulation under such special conditions as compressor choke, rotating stall and pumping surge. At the same time it’s important to obtain the fast and stable calculations of the engine’s operating cycle. Blitz-PRO – online internal combustion engines operating cycle simulation service – offers supercharger performance maps preprocessing and implementation. It provides three different modes of compressor surge consideration during calculations: 1) full-scale surge mode using Moore-Greitzer approach; 2) mild surge mode with flexible adjustment; 3) “stable” mode, when the surge is neglected and the compressor constant-speed lines are extended from the rotating stall point to the lower mass flow region with the hyperbolic equation. Using the MAN 8G70ME-E engine 12140 kW, 82 rpm operating point as an example, the calculation results are compared for three modes of compressor surge consideration. The “stable” mode provides the fastest and the most stable calculations, while the calculations under the full-scale surge mode could generate the numerical (nonphysical) instability of calculations, which are caused by the high sensitivity of the two-stroke engines to the gas exchange processes as it is shown. The mild surge mode provides fast and stable enough calculation with the surge consideration ability, which could be assumed as the best solution for the given example. The researcher should choose between provided three modes of the centrifugal compressor surge consideration according to the calculations tasks, preferring “stable” mode for initial model setup and mild surge mode for the surge probability check, while the accurate compressor surge simulation needs further development.

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Empirical soot formation and oxidation model

Thermal Science ◽

10.2298/tsci0903035b ◽

2009 ◽

Vol 13 (3) ◽

pp. 35-46 ◽

Cited By ~ 1

Author(s):

Karima Boussouara ◽

Mahfoud Kadja

Keyword(s):

Internal Combustion Engines ◽

Diffusion Flames ◽

Soot Formation ◽

Internal Combustion ◽

Combustion Model ◽

Diesel Combustion ◽

Combustion Engines ◽

Particulate Emission ◽

Cycle Simulation ◽

Air Mixing

Modelling internal combustion engines can be made following different approaches, depending on the type of problem to be simulated. A diesel combustion model has been developed and implemented in a full cycle simulation of a combustion, model accounts for transient fuel spray evolution, fuel-air mixing, ignition, combustion, and soot pollutant formation. The models of turbulent combustion of diffusion flame, apply to diffusion flames, which one meets in industry, typically in the diesel engines particulate emission represents one of the most deleterious pollutants generated during diesel combustion. Stringent standards on particulate emission along with specific emphasis on size of emitted particulates have resulted in increased interest in fundamental understanding of the mechanisms of soot particulate formation and oxidation in internal combustion engines. A phenomenological numerical model which can predict the particle size distribution of the soot emitted will be very useful in explaining the above observed results and will also be of use to develop better particulate control techniques. A diesel engine chosen for simulation is a version of the Caterpillar 3406. We are interested in employing a standard finite-volume computational fluid dynamics code, KIVA3V-RELEASE2.

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