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CFD Simulation on turbulent forced convection of CuO-Water Nanofluids in a horizontal circular pipe

John Deere India Pvt, Ltd.-Nitin Dewangan, Nitin Kattula
  • Technical Paper
  • 2019-28-0131
To be published on 2019-10-11 by SAE International in United States
The present study provides a detailed investigation on simulation of Copper oxide nanofluids in a simple horizontal circular pipe considering turbulent forced convection, with a constant heat flux boundary condition. The simulation is carried out using three different models available in fluent viz. Newtonian single phase model, Eulerian-mixture and Eulerian-Eulerian multiphase models. The Reynold number of the flow is varied along with volume concentration of nanoparticles varying from low to high. Nanofluids rheology is studied by considering standard k-ε two equation turbulence model with enhanced wall treatment considering appropriate wall y+ values. The effective temperature dependent thermo-physical properties for nanofluids were seized from the literatures. The results from the simulation clearly showed an increase in the heat transfer characteristics with the addition of nanofluids compared to that of base fluid alone. Eulerian-Mixture model predicted the Nusselt number near to that of the experimental results from literature. Index terms: Nanofluids, copper oxide, heat transfer, simulation, Nusselt number.
 

How to Improve SI Engine Performances by Means of Supercritical Water Injection

University of Basilicata – Potenza 85100-Antonio Cantiani, Annarita Viggiano, Vinicio Magi
  • Technical Paper
  • 2019-24-0235
To be published on 2019-10-07 by SAE International in United States
The efficiency of ICEs is strongly affected by the heat losses of exhaust gases and engine cooling system, which account for about 60% of the heat released by combustion. Several technologies were developed to recover waste heat in ICEs, from turbochargers to ORCs, Stirling cycles and piezoelectric generation. A promising approach is to transfer the waste heat to a fluid, like water, and inject it into the combustion chamber. In such a way, the recovered energy is partially converted into mechanical work, by improving both engine efficiency and performance. In this work, the engine benefits obtained by using supercritical water as the vector to recover heat losses are analysed. Water has been chosen since it has a relatively high heat capacity and can be extracted directly from exhaust gases. A quasi-dimensional model has been implemented to simulate the ICE work cycle. Specifically, in this paper a spark ignition ICE, four-stroke with port fuel injection (PFI) has been considered. The model accounts for gas species properties (Janaf tables and CoolProp libraries) and includes valves opening/closing laws,…
 

Development and Validation of SI Combustion Models for Natural-Gas Heavy-Duty Engines

Politecnico di Milano-Lorenzo Sforza, Tommaso Lucchini, Giovanni Gianetti, Gianluca D'Errico
  • Technical Paper
  • 2019-24-0096
To be published on 2019-09-09 by SAE International in United States
Flexible, reliable and consistent combustion models are necessary for the improvement of the next generation spark-ignition engines. Different approaches have been proposed and widely applied in the past. However, the complexity of the process involving ignition, laminar flame propagation and transition to turbulent combustion need further investigations. Purpose of this paper is to compare two different approaches describing turbulent flame propagation. The first approach is the one-equation flame wrinkling model by Weller, while the second is the Coherent Flamelet Model (CFM). Ignition is described by a simplified deposition model while the correlation from Herweg and Maly is used for the transition from the laminar to turbulent flame propagation. Validation of the proposed models was performed with experimental data of a natural-gas, heavy duty engine running at different operating conditions. To deeply analyze main differences between Weller and CFM models, a detailed comparison of computed and experimental data was performed in terms of cylinder pressure, heat release rate, wall heat transfer, distribution of progress variable and flame surface density.
 

Possibilities of Wall Heat Transfer Measurements at a Supercharged Euro IV Heavy-Duty Diesel Engine with High EGR-Rates, an In-cylinder Peak Pressure of 250 bar and an Injection Pressure up to 2500 bar

Daimler AG-Christian Hennes, Jürgen Lehmann
KIT Karlsruhe Institute Of Technology-Thomas Koch
  • Technical Paper
  • 2019-24-0171
To be published on 2019-09-09 by SAE International in United States
A raise of efficiency is, especially for CV, the strongest selling point concerning the TCO. Accompanied by legislations, with contradictive development demands, satisfying solutions have to be found. The analysis of energy losses in modern engines shows three influencing parameters. The losses resulting from taking real gas properties and non-ideal combustion into account have only a limited potential for gains, wall heat losses are currently believed to have the highest optimization potential. Critical for the occurrence of these losses is the wall heat transfer, which can be described by coefficients. To reduce WHT accompanying losses a decrease of energy transfer between combustion gas and combustion chamber wall is necessary. A measurement of heat fluxes is needed to determine the WHT relations at the combustion chamber of an engine. Methods to reduce the WHT can be developed and their effectiveness can be evaluated. As this is not done before for a heavy-duty engine, with peak pressures up to 250 bar, an increased in-cylinder turbulence and high EGR-rates is presented the following. The different methods to determine…
 

A Review of Spark-Assisted Compression Ignition (SACI) Research in the Context of Realizing a Production SACI Strategy

Clemson University-Dennis Robertson, Robert Prucka
  • Technical Paper
  • 2019-24-0027
To be published on 2019-09-09 by SAE International in United States
Low temperature combustion (LTC) strategies have been a keen interest in the automotive industry for over four decades since they offer improved fuel efficiency compared to conventional spark-ignition (SI) engines. LTC strategies use high dilution to keep combustion temperatures below about 2000 K to reduce heat transfer losses while avoiding locally rich in-cylinder regions that produce high soot. High dilution also enables an efficiency improvement from reduced pumping work and improved thermodynamic properties, though it requires high ignition energy. Combustion can be achieved by triggering autoignition from compression energy. High compression ratios are typically required to produce this level of ignition energy, which further improves fuel efficiency. The timing of the autoignition event is influenced by fuel properties and mixture composition, and is exponentially sensitive to temperature. Control of autoignition timing is difficult without a direct actuator, and has been a significant obstacle for realizing LTC in production. Spark-assisted compression ignition (SACI) addresses this challenge by using a spark plug to initiate chemical reactions that trigger autoignition. The combustion chamber is slightly stratified to promote…
 

Experimental Investigation on the Use of Argon to Improve FMEP Determination Through Motoring Method

Jaguar & Land Rover-Gilbert Sammut
Univ of Malta-Carl Caruana, Mario Farrugia
  • Technical Paper
  • 2019-24-0141
To be published on 2019-09-09 by SAE International in United States
Mechanical friction is still one of the current topics in internal combustion engine research and development. In the ever increasing challenge of developing more efficient and less polluting engines, friction reduction is of significant importance; whose investigation needs an accurate and reliable measurement technique. The Pressurized Motoring method is one of the techniques used for both friction and heat transfer measurements in internal combustion engines. This method is able to simulate mechanical loading on the engine components similar to the fired conditions. It also allows measurement of friction mean effective pressure (FMEP) with a much smaller uncertainty as opposed to that achieved from a typical firing setup. Despite its advantages, this method of FMEP determination is usually criticized over the fact that the thermal conditions imposed in pressurized motoring are far detached from those seen in fired conditions, hence not able to simulate the complete effects on FMEP. The authors have put forward a modification to the method, employing Argon in place of Air as pressurization medium (SAE paper 2019-01-0930). Due to the higher heat…
 

CFD Modeling of Compact Heat Exchangers for I.C. Engine Oil Cooling

Politecnico di Milano-Augusto Della Torre, Gianluca Montenegro, Angelo Onorati
UFI Filters-Roberto Icarelli
  • Technical Paper
  • 2019-24-0179
To be published on 2019-09-09 by SAE International in United States
In the last years, the increase of the specific power of the modern engines has required a parallel improvement of the performances of the cooling system. In this context, also the control of the oil temperature has become an important issue, leading to the introduction of dedicated cooling circuits (air-cooled or liquid-cooled). Among the two, the liquid-cooled solution results in a more compact installation in which the oil-to-liquid heat exchanger is directly mounted on the engine block and integrated in the engine cooling system. It is clear that, in a liquid-cooled solution, the design of the heat exchanger represents an issue of extreme concern, which requires a compromise between different objectives: high compactness, low pressure drop, high heat-transfer efficiency. In this work, a computational framework for the CFD simulation of compact oil-to-liquid heat exchangers, including offset-strip fins as heat transfer enhancer (turbolator), has been developed. The main problem is represented by the need of considering different scales in the simulation, ranging from the characteristic size of the turbolator geometry (tipically µm – mm) to the…
 

A Novel 1D Co-Simulation Framework for the Prediction of Tailpipe Emissions Under Different IC Engine Operating Conditions

Aristotle University of Thessaloniki-Grigorios Koltsakis, Zissis Samaras
EMPA-Panayotis Dimopoulos Eggenschwiler, Viola Papetti, Jakub Rojewski, Patrik Soltic
  • Technical Paper
  • 2019-24-0147
To be published on 2019-09-09 by SAE International in United States
The prediction of the pollutants emitted by internal combustion engines during driving cycles has been a challenge since the introduction of the emission regulation legislation. During the last decade, along with the more tightening limits and increased public concern about the matter of air quality, the possibility of simulating various driving tests with cost effective computing facilities has become a key feature for modern simulation codes. Many 1D simulation tools are available on the market, offering real time models capable of achieving the simulation of any driving cycle in limited time frames. These approaches are based on the extreme simplification of the engine geometry and on the adoption of engine maps, which, for any engine operating condition, give the engine output in terms of power, or torque, and of exhaust gas composition. Specific fluid dynamic models are used to track the composition along the exhaust system and, with the aid of ad-hoc modules, to evaluate the conversion efficiency of after-treatment devices, such as TWC, GPF, DPF, DOC, SCR and so on. This work is based…
 

Performance and Emissions of an Advanced Multi-Cylinder SI Engine Operating in Ultra-Lean Conditions

Renault SA-Cédric LIBERT
University of Naples “Federico II”-Fabio Bozza, Daniela Tufano, Enrica Malfi, Luigi Teodosio, Vincenzo De Bellis
  • Technical Paper
  • 2019-24-0075
To be published on 2019-09-09 by SAE International in United States
Along the design process of a new engine, the calibration phase at the test bench usually involves a relevant percentage of the overall time-to-market. Each control variable, in fact, needs to be properly selected to optimize the performance and emissions, complying with thermal and mechanical stresses limits of the engine. This issue is still more critical for advanced engine architectures, which include additional control variables, such as valve phasing, turbocharger control, EGR level, etc. The aim of this work is the development of a numerically performed calibration procedure, applied to a prototype multi-cylinder Spark Ignition (SI) engine, designed to operate at very lean mixtures. To this aim, an active Pre-Chamber ignition system is considered. The required air flow rate is indeed provided by a Low-Pressure (LP) variable geometry turbocharger group, coupled to a high-pressure e-compressor. A Variable Valve Timing (VVT) device is also selected to reduce pumping losses at low load and for knock control at high-load. For the above engine, seven control variables have to be fixed in each operating condition, namely the Air/Fuel…
 

Validation and Analysis of Heat Losses Prediction Using Conjugate Heat Transfer Simulation for an Internal Combustion Engine

CMT- Universitat Politècnica de València-Alberto Broatch, Xandra Margot, Jorge Garcia-Tiscar, Johan Escalona
  • Technical Paper
  • 2019-24-0091
To be published on 2019-09-09 by SAE International in United States
New technologies are required to improve engine thermal efficiency. For this it is necessary to use all the tools available nowadays, in particular computational tools, which allow testing the viability of different solutions at reduced cost. In addition, numerical simulations often provide more complete and precise information than experimental tests. Such is the case for the study of the heat transfer through the walls of an engine. Conjugate Heat Transfer (CHT) simulations permit precise calculations of the heat transfer rate from gas to walls throughout the whole engine cycle, and thus it is possible to know such details as the instantaneous heat losses and wall temperature distribution on the walls, which no experiment can give. Nevertheless, it is important to validate CHT calculations, either with some experimental measurements or with some other reliable tool, such as 0D-1D modelling known to work well. The proposed work is based on the CHT simulation of the heat transfer to the walls of an engine piston during an entire cycle to determine the parameters that permit obtaining good results.…