Development of an Efficient Conjugate Heat Transfer Modeling Framework to Optimize Mixing-Limited Combustion of Ethanol in a Diesel Engine

2021 ◽  
Author(s):  
Gina M. Magnotti ◽  
Chinmoy K. Mohapatra ◽  
Alireza Mashayekh ◽  
Sameera Wijeyakulasuriya ◽  
Robert Schanz ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Diesel Engine ◽  
Thermal Efficiency ◽  
Conjugate Heat Transfer ◽  
Pressure Rise ◽  
Cfd Modeling ◽  
Modeling Framework ◽  
Percentage Point Increase ◽  
Piston Bowl ◽  
Point Increase

Abstract Mixing controlled combustion of alcohol fuels has been identified as a promising technology based on their low propensity for particulate and NOx production, but the higher heats of vaporization and auto-ignition temperatures of these fuels make their direct use in diesel engine architectures a challenge. To realize the potential of alcohol-fueled combustion, a computational fluid dynamics (CFD) modeling framework is developed, validated and exercised to identify designs that maximize engine thermal efficiency. To evaluate the use of thermal barrier coatings, a simplified 1-D conjugate heat transfer (CHT) modeling framework is employed. The addition of the 1-D CHT model only increases the computational expense by 15% relative to traditional approaches, yet offers more accurate heat transfer predictions over constant temperature boundary conditions. The validated model is then used to explore a range of injector orientations and piston bowl geometries. Using a design of experiments approach, several designs were identified that improved fuel-air mixing, shortened the combustion duration, and increased thermal efficiency. The most promising design was fabricated and tested in a Caterpillar 1Y3700 Single Cylinder Oil Test Engine. Engine testing confirmed the findings from the CFD simulations, and found that the co-optimized injector and piston bowl design yielded over 2-percentage point increase in thermal efficiency at the same equivalence ratio (0.96) and over 6-percentage point increase at the same engine load (10.1 bar indicated mean effective pressure), while satisfying design constraints for peak pressure and maximum pressure rise rate.

Development of an Efficient Conjugate Heat Transfer Modeling Framework to Optimize Mixing-Limited Combustion of Ethanol in a Diesel Engine

2020 ◽  
Author(s):  
Gina M. Magnotti ◽  
Chinmoy K. Mohapatra ◽  
Alireza Mashayekh ◽  
Sameera Wijeyakulasuriya ◽  
Robert Schanz ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Diesel Engine ◽  
Thermal Efficiency ◽  
Conjugate Heat Transfer ◽  
Design Parameters ◽  
Modeling Framework ◽  
Percentage Point Increase ◽  
Piston Bowl ◽  
Point Increase ◽  
Alcohol Fuels

Abstract Long-term petroleum prices and increasingly-stringent emissions regulations are driving manufacturers and users alike to consider alternatives to diesel-fueled engines. Mixing controlled combustion of alcohol fuels, such as ethanol, has been identified as a promising technology based the low propensity for particulate and NOx production, but the higher heats of vaporization and auto-ignition temperatures of these fuels make their direct use in diesel engine architectures a challenge. However, because alcohol fuels do not form appreciable levels of soot even in mixing-controlled (MCCI) mode, and because stoichiometric air/fuel ratios (AFR) can be used to simplify NOx aftertreatment, engine design optimization efforts can be targeted to maximize thermal efficiency. Therefore, to realize the potential of alcohol-fueled combustion, engineering insight is required to understand how design parameters, such as increased engine insulation, piston bowl geometry, or spray targeting, should be optimally utilized. In this work, a computational fluid dynamics (CFD) modeling framework is developed and validated in order to identify pathways to improve the performance of an ethanol-fueled engine operating in an MCCI mode at a stoichiometric AFR. To evaluate the use of TBCs as an engine insulation method, a simplified 1-D conjugate heat transfer (CHT) modeling framework is employed. The CFD model is first validated against baseline engine data over selected inlet air heating temperatures for two piston bowl-injector configurations that define the extrema of the design space. The addition of the 1-D CHT model only increases the computational expense by 15% relative to traditional approaches, yet offers more accurate heat transfer predictions over constant temperature boundary conditions. The model is then used to explore the efficacy of injector orientations and piston bowl geometries in improving the indicated thermal efficiency of alcohol fueled compression ignition engines. Using a design of experiments approach, several candidate designs were identified that improved fuel-air mixing, shortened the combustion duration, and increased thermal efficiency. The most promising design was then fabricated and tested in a Caterpillar 1Y3700 Single Cylinder Oil Test Engine (SCOTE). The engine testing confirmed the findings from the CFD simulations, and found that the co-optimized injector and piston bowl design yielded over 2-percentage point increase in thermal efficiency at the same equivalence ratio (0.96) and over 6-percentage point increase at the same engine load (10.1 bar indicated mean effective pressure), while satisfying design constraints for peak pressure and maximum pressure rise rate.

Development of an Efficient Conjugate Heat Transfer Modeling Framework to Optimize Mixing-Limited Combustion of Ethanol in a Diesel Engine

2021 ◽  
Author(s):  
Gina Magnotti ◽  
Chinmoy K. Mohapatra ◽  
Alireza Mashayekh ◽  
Sameera Wijeyakulasuriya ◽  
Robert Schanz ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Diesel Engine ◽  
Conjugate Heat Transfer ◽  
Modeling Framework ◽  
Heat Transfer Modeling

Development of an Efficient Conjugate Heat Transfer Modeling Framework to Optimize Mixing-Limited Combustion of Ethanol in a Diesel Engine

2021 ◽  
Author(s):  
Gina Magnotti ◽  
Chinmoy K. Mohapatra ◽  
Alireza Mashayekh ◽  
Sameera Wijeyakulasuriya ◽  
Robert Schanz ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Diesel Engine ◽  
Conjugate Heat Transfer ◽  
Modeling Framework ◽  
Heat Transfer Modeling

CFD Modeling of the Hydrogen Fast Filling Process for Type 3 Cylinders and Cylinders Lined With Phase Change Material

2019 ◽  
Author(s):  
Miroslaw Liszka ◽  
Aleksandr Fridlyand ◽  
Ambalavanan Jayaraman ◽  
Michael Bonnema ◽  
Chakravarthy Sishtla
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Phase Change ◽  
Conjugate Heat Transfer ◽  
Cfd Modeling ◽  
Computational Time ◽  
Filling Process ◽  
Transfer Case ◽  
Type 3 ◽  
Experimental Pressure

Abstract A simulation of the fast filling of a 195-liter type 3 tank with hydrogen was completed with ANSYS Fluent as a baseline case for developing a CFD model capable of accurately modeling the hydrogen cylinder filling process. 141-second profiles of mass flow and temperature of the incoming hydrogen flow into the cylinder were prescribed from experimental data previously collected at the Gas Technology Institute (GTI) in Des Plaines, IL. All the simulations were completed with the coupled pressure based algorithm with the K-Omega SST turbulence model and real gas NIST properties (REFPROP) to capture the effects of compressibility of hydrogen during the filling process. Gravity was enabled in the axial direction of the cylinder. The initial pressure and temperature in the cylinder were 124 bar and 292.3 K, respectively, with a target, experimental pressure of 383 bar at the end of the filling. For the initial case, the walls of the cylinder were modelled as adiabatic to reduce the computational effort. The final pressure and temperature of the adiabatic wall case matched the experimental pressure and temperature within approximately 30 bar and 6 degrees, respectively. The overall pressure and temperature profiles over the course of the filling process also provided a good match between the simulation results and experimental data. A conjugate heat transfer case with the aluminum liner as part of the domain and an adiabatic outer wall was attempted in order to capture the heat transfer to the liner. The conjugate heat transfer case provided promising results but was taxing in the computational time needed to simulate the entire filling process. A User Defined Function (UDF) for a simple lumped heat capacitance model was applied at the wall to model the wall temperature and capture the heat transfer occurring to the wall while reducing the time needed to complete the simulation. The final pressure prediction for this case was excellent, within 3 bar of the experimental value, and matched it accurately for the duration of the fill process. The final temperature prediction worsened and exceeded the experimental value by 16 degrees Celsius. The UDF model also allowed the ability to easily explore more exotic liners such as Phase Change Materials (PCM) which were also simulated in this work.

Effect of Piston Bowl Shape and Swirl Ratio on Engine Heat Transfer in a Light-Duty Diesel Engine

2014 ◽  
Author(s):  
Helgi Skuli Fridriksson ◽  
Martin Tuner ◽  
Oivind Andersson ◽  
Bengt Sunden ◽  
Hakan Persson ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Diesel Engine ◽  
Swirl Ratio ◽  
Piston Bowl ◽  
Light Duty

scholarly journals Assessing the optimum combustion under constrained conditions

2018 ◽  
Vol 21 (5) ◽  
pp. 811-823 ◽  
Author(s):  
Pablo Olmeda ◽  
Jaime Martín ◽  
Ricardo Novella ◽  
Diego Blanco-Cavero
Keyword(s):  
Heat Transfer ◽  
Diesel Engine ◽  
Heat Release ◽  
Engine Speed ◽  
Direct Injection ◽  
Pressure Rise ◽  
Maximum Pressure ◽  
Low Load ◽  
Negative Effect ◽  
Constrained Conditions

This work studies the optimum heat release law of a direct injection diesel engine under constrained conditions. For this purpose, a zero-dimensional predictive model of a diesel engine is coupled to an optimization tool used to shape the heat release law in order to optimize some outputs (maximize gross indicated efficiency and minimize NO x emissions) while keeping several restrictions (mechanical limits such as maximum peak pressure and maximum pressure rise rate). In a first step, this methodology is applied under different heat transfer scenarios without restrictions to evaluate the possible gain obtained through the thermal isolation of the combustion chamber. Results derived from this study show that heat transfer has a negative effect on gross indicated efficiency ranging from −4% of the fuel energy ( ṁfHv), at high engine speed and load, up to −8% ṁfHv, at low engine speed and load. In a second step, different mechanical limits are applied resulting in a gross indicated efficiency worsening from −1.4% ṁfHv up to −2.8% ṁfHv compared to the previous step when nominal constraints are applied. In these conditions, a temperature swing coating that covers the piston top and cylinder head is considered obtaining a maximum gross indicated efficiency improvement of +0.5% ṁfHv at low load and engine speed. Finally, NO x emissions are also included in the optimization obtaining the expected tradeoff between gross indicated efficiency and NO x. Under this optimization, cutting down the experimental emissions by 50% supposes a gross indicated efficiency penalty up to −8% ṁfHv when compared to the optimum combustion under nominal limits, while maintaining the experimental gross indicated efficiency allows to reduce the experimental emissions 30% at high load and 65% at low load and engine speed.

scholarly journals PERFORMANCE AND EXHAUST EMISSIONS OF DIRECT‐INJECTION DIESEL ENGINE OPERATING ON RAPESEED OIL AND ITS BLENDS WITH DIESEL FUEL

Transport ◽  
2005 ◽  
Vol 20 (5) ◽  
pp. 186-194 ◽  
Author(s):  
Gvidonas Labeckas ◽  
Stasys Slavinskas
Keyword(s):  
Diesel Engine ◽  
Thermal Efficiency ◽  
Rapeseed Oil ◽  
Direct Injection ◽  
Brake Specific Fuel Consumption ◽  
Fuel Blend ◽  
Engine Operation ◽  
Point Increase ◽  
Smoke Opacity ◽  
Co Emission

During engine operation at 1 400, 1 800 and 2 200 min‐1 the brake specific fuel consumption has on an average been increased by 0,104 %, 0,134 % and 0,156 % for every 1 % point increase in RO inclusion into DF. The maximum thermal efficiency values remain within 0,37–0,39 intervals. The maximum NOx emission increases with the mass percent of oxygen in the fuel blend and for RO and its blends RO75 and RO50 are higher by 9,2 %, 20,7 % and 5,1 %, respectively. Emissions of NO2 increase with an increasing content of RO premixed into DF. When operating on pure RO and its blends RO75 and RO50 the maximum CO emission reduces by 40,5 % ‐52,9 % and 7,2 %‐15,0 %, respectively. The smoke opacity generated from RO and its blends is also by 27,1% ‐34,6 % and 41,7 % ‐51,0 % lower. Emissions of HC remain on a considerably low level ranging between 8 to 16 ppm whereas during engine operation on pure RO they approach to about a zero level. Emissions of CO2 for RO and fuel blend RO75 are slightly higher.

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