Assessing the optimum combustion under constrained conditions

Self Cite

In recent years, the interests on transient operation and real driving emissions have increased because of the global concern about environmental pollution that has led to new emissions regulation and new standard testing cycles. In this framework, it is mandatory to focus the engines research on the transient operation, where a Virtual Engine has been used to perform the global energy balance of a 1.6-L diesel engine during a World harmonized Light vehicles Test Cycle. Thus, the energy repartition of the chemical energy has been described with warmed engine and cold start conditions, analyzing in detail the mechanisms affecting the engine consumption. The first analysis focuses on the “delay” effect affecting the instantaneous energy balance due to the time lag between the in-cylinder processes and pipes: as a main conclusion, it is obtained that it leads to an apparent unbalance than can reach more than 10% of the cumulated fuel energy at the beginning of the cycle, becoming later negligible. Energy split analysis in cold starting World harmonized Light vehicles Test Cycle shows that in this condition the energy accumulation in the block is a key term at the beginning (about 50%) that diminishes its weight until about 10% at the end of the cycle. In warmed conditions, energy accumulation is negligible, but the heat transfer to coolant and oil are higher than in cold starting conditions (21% vs 28%). The lower values of the mean brake efficiency at the beginning of the World harmonized Light vehicles Test Cycle (only about 20%) is affected, especially in cold starting, by the higher mechanical losses due to the higher oil viscosity and the heat rejection from the gases. The friction plays an important role only during the first half of the cycle, with a percentage of about 65% of the total mechanical losses and 10% of the total fuel energy at the end of the World harmonized Light vehicles Test Cycle. However, at the end of the cycle, it does not affect dramatically the mean brake efficiency which is about 31% both in cold starting and warmed World harmonized Light vehicles Test Cycle.

Section: Introductionmentioning

confidence: 99%

Analysis of the energy balance during World harmonized Light vehicles Test Cycle in warmed and cold conditions using a Virtual Engine

Olmeda

Martín

Arnau

et al. 2019

Self Cite

“…For doing a more exhaustive analysis, it was necessary to obtain some results from thermodynamic diagnosis by means of a zero dimensional model. 22,23 This tool, very used in a wide type of works related to the optimization of the combustion process 29 or for studying constructive parameters of the engine, such as the in-cylinder swirl air movement, on the engine efficiency 30 or on both the engine heat rejection and efficiency, 31 it has been used for determining both the indicated and pumping works.…”

Section: Resultsmentioning

confidence: 99%

Effect of the use of a thermoelectric generator on the pumping work of a diesel engine

Ezzitouni

Fernández-Yáñez

Rodríguez

et al. 2019

Approximately a third part of the energy intake of a light-duty diesel engine is wasted through the exhaust system. Rising awareness of environmental issues together with fuel economy has encouraged research upon energy recovery in internal combustion engines. This article focuses on the application of thermoelectric generators in light-duty diesel vehicles. Most studies available in the literature tend to focus on maximizing the recovered electrical power, not always considering the increase in engine pumping work or testing conditions similar to those of a vehicle. The goal of this article is to evaluate the consequences of the modification of the cross-sectional area in the exhaust pipe that adding a thermoelectric generator implies and to compare them with the electrical power produced by the thermoelectric generator. The effect on the indicated and pumping parameters of the engine under common urban driving conditions is presented. From the results, it can be drawn that within the limits of engine speed and torque tested, the modification of the cross-sectional area does not have a significant negative effect on the engine pumping efficiency. This means that there is potential for the employment of this technique in energy recovery from light-duty vehicles.

“…Wave motion across the chamber was successfully resolved and compared with theoretical cylinder modes. However, no realistic initial flow field or combustion model were used, 23 introducing instead small regions of high pressure simulating the ignition points. More recent studies 24,25 included realistic flow conditions and combustion modeling in the loop.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the effects of turbulence modeling on the prediction of compression-ignition combustion unsteadiness

Broatch

Novella

García-Tíscar

et al. 2021

Adverse effects of global warming due to the greenhouse gas emissions is changing the actual paradigm for the use energy resources. In the absence of a mid-term solution for reducing these emissions in transportation, internal combustion (IC) engines are going to coexist in the social spheres in the foreseeable future. Therefore, the study of other IC engine-related problems remains relevant to ensuring the health of the society. In this investigation, a numerical methodology for comprehensive understanding of Noise, Vibration and Harshness in internal combustion engines is proposed. Due to its inherent complexity and lack of awareness, the main objective is to evaluate the impact of the turbulence modeling framework on the in-cylinder acoustic field recreation. Modal decomposition methods have been applied to isolate the coherent flow structures and to analyze how they change with the turbulence approach. Results demonstrate that the choice of the turbulence model is a critical aspect for noise modeling. Unsteady Reynolds-Averaged Navier-Stokes schemes predict a raw estimation of the internal acoustic field with the added value of being computationally less expensive. However, the use of more complex turbulence approaches such us large eddy simulation offers an accurate prediction of the acoustic structures and their cyclic dispersion.