A one-dimensional modeling study on the effect of advanced insulation coatings on internal combustion engine efficiency

Self Cite

To comply with the very strict emissions regulation the automotive industry is succeeding in developing ever more efficient engines, and there is scope for more improvements. In this regard, some investigations have suggested that insulating the combustion chamber walls of an internal combustion engine (ICE) yield low thermal losses. Most of the literature available on this topic presents simplified models that do not allow studying in detail the coating impact on engine efficiency. A more precise approach that consists in the combination of Computational Fluid Dynamics (CFD) and Conjugate Heat Transfer (CHT) simulations is used in this paper to predict the heat losses through the combustion chamber walls of a spark ignition (SI) engine. Two configurations are considered for the single cylinder engine: the metallic case and the same engine with coated piston and cylinder head. The insulation material has a low thermal conductivity ( k[Formula: see text]1.0 W/( mK)). The numerical results are validated by comparison with the results of a 1D heat transfer model and with experimental data for a medium load operation point (3000 rpm −7 bar IMEP). The solutions obtained are analysed in detail in terms of wall temperature distribution and heat transfer. The impact of the coating on the engine efficiency is thus assessed. The CFD-CHT calculations yields very good results in terms of heat transfer prediction during the whole engine cycle.

Section: Methodsmentioning

confidence: 99%

Conjugate heat transfer study of the impact of ‘thermo-swing’ coatings on internal combustion engines heat losses

Broatch

Olmeda

Margot

et al. 2020

Self Cite

“…4 Since the computational power has increased exponentially, computational fluid dynamics (CFD) simulations have become a fundamental solution that complements the experimental measurements for studying some engine phenomena that allow to reduce these emissions. Very different phenomena can be simulated, as heat transfer models, 5 turbocharger unsteady behaviour prediction, 6 internal details of fuel injectors, 7 URANS/LES cylinder simulations 8,9 or noise characterisation. 10,11 One of the most wide and efficient techniques for reducing the emissions is turbocharging the ICE.…”

Section: Introductionmentioning

confidence: 99%

Twin-entry turbine losses: An analysis using CFD data

Galindo

Serrano

Medina

2021

The current paper presents a computational fluid dynamics (CFD) flow behaviour and losses analysis of twin-entry radial turbines in terms of its Mass Flow Ratio ( MFR, the ratio between the flow passing through one of its intake ports and its total mass flow), focusing on the mixing phenomena in the unequal admission conditions cases. The CFD simulations are first validated with experimental data. Then, the losses mechanisms are analysed and quantified in the different parts of the twin-entry turbine in terms of the MFR value. A sudden expansion is found at the junction of both branches in the interspace between volutes and rotor for unequal and partial admission cases. Tracking the flow coming from each of the turbine intake ports, it has been observed that both flow branches do not fully mix with each other within the rotor. Another source of losses has been identified in the contact between both flow branches due to their momentum exchange that depends on the difference between both flow branches velocities. These losses have not been considered before, and they should be included in mean line loss-based models for twin-entry turbine since they are very significant for unequal admission conditions.

“…More recently, the potential of TBCs has however been firmly recognised and also put to use: notably, the Toyota metal-based silica-reinforced porous anodised aluminium (SiRPA Ò ) coating 2 was developed within the last decade. Recent computational studies [7][8][9] have attempted to estimate the efficiency potential of coating solutions in diesel engines. Moreover, more extreme TSMs continue to be investigated: Andrie et al 10 recently report marked efficiency gains with a thin layer of a material that possesses a conductivity and heat capacity nearly an order of magnitude smaller than plasma-sprayed partially stabilised zirconia (PSZ), a conventional TBC material.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of wall heat transfer due to spray combustion in a high-pressure/high-temperature vessel

Keskinen

Vera-Tudela

Wright

et al. 2021

Combustion chamber wall heat transfer is a major contributor to efficiency losses in diesel engines. In this context, thermal swing materials (adapting to the surrounding gas temperature) have been pinpointed as a promising mitigative solution. In this study, experiments are carried out in a high-pressure/high-temperature vessel to (a) characterise the wall heat transfer process ensuing from wall impingement of a combusting fuel spray, and (b) evaluate insulative improvements provided by a coating that promotes thermal swing. The baseline experimental condition resembles that of Spray A from the Engine Combustion Network, while additional variations are generated by modifying the ambient temperature as well as the injection pressure and duration. Wall heat transfer and wall temperature measurements are time-resolved and accompanied by concurrent high-speed imaging of natural luminosity. An investigation with an uncoated wall is carried out with several sensor locations around the stagnation point, elucidating sensor-to-sensor variability and setup symmetry. Surface heat flux follows three phases: (i) an initial peak, (ii) a slightly lower plateau dependent on the injection duration, and (iii) a slow decline. In addition to the uncoated reference case, the investigation involves a coating made of porous zirconia, an established thermal swing material. With a coated setup, the projection of surface quantities (heat flux and temperature) from the immersed measurement location requires additional numerical analysis of conjugate heat transfer. Starting from the traces measured beneath the coating, the surface quantities are obtained by solving a one-dimensional inverse heat transfer problem. The present measurements are complemented by CFD simulations supplemented with recent rough-wall models. The surface roughness of the coated specimen is indicated to have a significant impact on the wall heat flux, offsetting the expected benefit from the thermal swing material.