Thermal boundary layer thickness in the cylinder of a spark-ignition engine

Modelling the effects of combustion and turbulence on near-wall temperature gradients in the cylinders of spark ignition engines

“…Pan and Sheppard [18] arbitrarily specified end-gas temperature gradients as input into their two-dimensional code for the analysis of the modes of auto-ignition. Min and Cheng [19] computed the thermal boundary layer temperature profile using expressions for the dimensionless temperature profile empirically derived from the measurements of Lucht et al [11] and the thermal boundary layer thicknesses measured by Lydford-Pike and Heywood [10]. Lavoie and Blumberg [20] accounted for the thermal boundary layer in a quasidimensional model by the use of a linear temperature profile.…”

“…for use in the numerical solution of equation (10). Thermal conductivity, ë, is evaluated using a polynomial curve fit to values from tables for air.…”

“…Lydford-Pike and Heywood [10] used schlieren photography to observe significant density gradients near to the cylinder walls of a square, transparent research engine, implying temperature gradients in these regions. Lucht et al [11] used coherent anti-Raman± Stokes scattering (CARS) and Farrell [12] used speckle interferometry to resolve the near-wall temperature gradients in optical access research engines.…”

Fluid flow and heat transfer in a helium gas spring : computational fluid dynamics and experiments

“…Meshing with parameters that would satisfy the Kolmogorov turbulent length scale in every region of the computed domain for even the fastest case presented here, would employ (apart from tedious meshing efforts) an extensive investment in computing costs to perform such simulations. 36 36 Some physicists today dispute the adequacy of Kolmogorov's dimensional reasoning [56]. The complete description of turbulence remains one of the unsolved problems in physics.…”

“…As the operating frequency increases, the boundary layers become narrower and the temperature gradient at the walls steeply rises, becoming completely 'detached' from the central region. Although according to some authors these regions can carry up to 30-40 % of the compressed mass during expansion [36], still the main mass of helium is in the core and the averaged gas temperature will predominantly represent the temperature of the central region. In this situation the temperature of the gas at the wall boundaries thus cannot be directly correlated to the bulk gas temperature, and the steady-state gas-wall heat transfer analogies will fail.…”