Thermal Studies in the Exhaust System of a Diesel-Powered Light-Duty Vehicle

Alkidas, A. C.; Battiston, Paul A.; Kapparos, David J.

doi:10.4271/2004-01-0050

Cited by 14 publications

(4 citation statements)

References 12 publications

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“…However, it provides a sufficient first approach to reach the instantaneous heat transfer coefficient variation inside the context of the present experimental investigation. Different approaches on gas temperature prediction constitute the models presented by Alkidas et al in [43] and also by Ranganathan et al in [44].…”

Section: The Simulation Modelmentioning

confidence: 98%

Experimental Assessment of Instantaneous Heat Transfer in the Combustion Chamber and Exhaust Manifold Walls of Air-Cooled Direct Injection Diesel Engine

Mavropoulos¹,

Rakopoulos²,

Hountalas³

2008

SAE Int. J. Engines

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An experimental analysis is carried out to investigate several heat transfer characteristics during the engine cycle, in the combustion chamber and exhaust manifold walls of a direct injection (DI), air-cooled, diesel engine. For this purpose, a novel experimental installation has been developed, which separates the engine transient temperature signals into two groups, namely the longand the short-term response ones, processing the respective signals in two independent data acquisition systems. Furthermore, a new pre-amplification unit for fast response thermocouples, appropriate heat flux sensors and an innovative, object-oriented, control code for fast data acquisition have been designed and applied. Experimentally obtained cylinder pressure diagrams together with semi-empirical equations for instantaneous heat transfer were used as basis for the calculation of overall heat transfer coefficient. On the other hand, one-dimensional heat conduction theory with Fourier analysis techniques combined with an iterative procedure between calculated and measured temperature data are implemented, in order to calculate the instantaneous local engine cylinder heat transfer coefficients in the cylinder head surfaces. For the exhaust manifold, the local gas temperature was calculated based on a thermal-zone model approach developed. Analysis of experimental results revealed significant differences between the overall and local peak heat transfer coefficient values in the cylinder head surface. The effect of engine speed and load as well as the effect of air-swirling motion on cylinder head heat transfer coefficient variation are presented and quantified, revealing the significant influence of turbulence on local heat transfer conditions. The effect of valve motion on instantaneous heat transfer is also depicted and quantified. Analysis of the results for the instantaneous wall temperatures and heat transfer coefficient on the exhaust manifold reveals interesting details regarding the flow of exhaust gases, both in the blowdown and displacement phases of the engine exhaust stroke. From the results it is concluded that the instantaneous heat transfer coefficient variation for engine combustion chamber is highly non-uniform, unlike its values calculated from standard correlations that assume spatial uniformity. This is very important, since especially for air-cooled diesel engines limited relevant information seems to exist in the literature.

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Section: The Simulation Modelmentioning

confidence: 98%

Experimental Assessment of Instantaneous Heat Transfer in the Combustion Chamber and Exhaust Manifold Walls of Air-Cooled Direct Injection Diesel Engine

Mavropoulos¹,

Rakopoulos²,

Hountalas³

2008

SAE Int. J. Engines

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“…For what concerns precision, studies show that there is good agreement between the two above-illustrated acquisition techniques [40]. However, for the present case, thermocouples were chosen.…”

mentioning

confidence: 97%

Torque Prediction Model of a CI Engine for Agricultural Purposes Based on Exhaust Gas Temperatures and CFD-FVM Methodologies Validated with Experimental Tests

et al. 2021

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A truly universal system to optimize consumptions, monitor operation and predict maintenance interventions for internal combustion engines must be independent of onboard systems, if present. One of the least invasive methods of detecting engine performance involves the measurement of the exhaust gas temperature (EGT), which can be related to the instant torque through thermodynamic relations. The practical implementation of such a system requires great care since its torque-predictive capabilities are strongly influenced by the position chosen for the temperature-detection point(s) along the exhaust line, specific for each engine, the type of installation for the thermocouples, and the thermal characteristics of the interposed materials. After performing some preliminary tests at the dynamometric brake on a compression-ignition engine for agricultural purposes equipped with three thermocouples at different points in the exhaust duct, a novel procedure was developed to: (1) tune a CFD-FVM-model of the exhaust pipe and determine many unknown thermodynamic parameters concerning the engine (including the real EGT at the exhaust valve outlet in some engine operative conditions), (2) use the CFD-FVM results to considerably increase the predictive capability of an indirect torque-detection strategy based on the EGT. The joint use of the CFD-FVM software, Response Surface Method, and specific optimization algorithms was fundamental to these aims and granted the experimenters a full mastery of systems’ non-linearity and a maximum relative error on the torque estimations of 2.9%.

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“…The outer surfaces of Al 2 O 3 substrates have been considered as the thermal boundary for simulation. A constant heat flux of ∼10 4 W/m 2 (observed between the takedown inlet and tailpipe exit of the automobile exhaust 39 ) under the isoflux condition and a fixed temperature of T h = 773 K under the isothermal condition have been applied at the hot side of the module. Further, the optimized 36 p−nmultilegged TEG (Figure 1(c)) has been simulated in order to compare its performance with the p-legged TEG.…”

Section: ■ Introductionmentioning

confidence: 99%

Performance Analysis and Optimization of a SnSe-Based Thermoelectric Generator

Bhattacharya

Ranjan

Kumar

et al. 2021

ACS Appl. Energy Mater.

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The thermoelectric generator (TEG) is considered as one of the most promising technologies for clean energy generation. But performance optimization with respect to its design and architecture is required for wide-scale commercialization. In this study, we have carried out finite element modeling (FEM) of a SnSe-based thermoelectric generator (TEG) considering electrical contact loss and various heat losses under isothermal and isoflux heat boundary conditions. The conventional Π-architecture comprising both p- and n-legs often results in overall poor performance due to the inferior efficiency of the n-leg TE module compared to its p-counterpart even though SnSe holds high ZT values (≥2). To counter that, we have strategized to design only a p-legged architecture and evaluated its performance in terms of power output and efficiency. Step-by-step optimization of internal and system level parameters for a multiple p-legged as well as traditional p–n-legged TEG has been carried out. Further, Al-based fins have been used to increase the net heat capturing area in the case of the isoflux heat boundary condition. The incorporation of fins facilitates us to redefine an internal parameter called fill fraction (FF) in terms of system level parameters, which leads to easier optimization of the TEG. Keeping in mind the practical application of a TEG in automobile exhaust, simulation of multiple p-legged architecture has resulted in maximum power output of 6.61 and 3.45 W under the isothermal and isoflux heat boundary conditions, respectively. In the FEM considering various thermal and electrical losses under the isothermal heat boundary condition, a maximum efficiency of 4.8% has been obtained in the case of Π-architecture, which is slightly higher than that obtained in the multiple p-legged TEG (3.48%). However, under the isoflux scenario, which is more commonly found in practical waste-heat sources, a maximum efficiency of 17.5% has been achieved for multiple p-legged architecture, which is 14 times higher than that attained for Π-architecture (1.24%). Also, a huge surge (500%) in maximum power output has been observed for the proposed multiple p-legged TEG compared to Π-architecture in our FEM considering various thermal and electrical losses in the isoflux heat source condition. Furthermore, the investigation of thermal and mechanical stability in terms of generated von Mises stress and deformation due to a significant temperature difference has revealed that multiple p-legged architecture is indeed more stable as compared to a Π-architecture TEG under both of the heat boundary conditions.

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Thermal Studies in the Exhaust System of a Diesel-Powered Light-Duty Vehicle

Cited by 14 publications

References 12 publications

Experimental Assessment of Instantaneous Heat Transfer in the Combustion Chamber and Exhaust Manifold Walls of Air-Cooled Direct Injection Diesel Engine

Experimental Assessment of Instantaneous Heat Transfer in the Combustion Chamber and Exhaust Manifold Walls of Air-Cooled Direct Injection Diesel Engine

Torque Prediction Model of a CI Engine for Agricultural Purposes Based on Exhaust Gas Temperatures and CFD-FVM Methodologies Validated with Experimental Tests

Performance Analysis and Optimization of a SnSe-Based Thermoelectric Generator

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