Cycle-Resolved Computations of Stratified-Charge Turbulent Combustion in Direct Injection Engine

Abstract

An extremely lean burning engine has been expected to improve fuel consumption rate of engines. To achieve this, stable combustion should be realized for a wide range of operating conditions at air-fuel ratio over 40.0. In direct injection gasoline engines, cyclic variations of combustion derive from some main factors such as those of air flows and spray motions. In this report, we examine the influence of cyclic variations of "Air flows" and "Spray motions" on combustion instabilities, while other variation factors are fixed for each cycle of engine, by using our simulation model. The cyclic variations of stratified-charge turbulent combustion in direct injection gasoline engine can be simulated during ten continuous cycles based on the multi-level formation for the stochastic compressible Navier-Stokes equation and also a spray model. Computational results agree with cycle-averaged experimental data fairly well, while the cyclic variations computed are comparable to experimental ones reported by the other research group. Consequently, the present computational model will reveal an essential factor which generates the cyclic variations and will offer us an effective way to control combustion instabilities on very lean burning conditions.

Fugine: the supermultijet-convergence engine working from startup to hypersonic scram mode and attaining simultaneously light-weight, high-efficiency, and low noise

“…By using the computational code [17][18][19][20], we also started to realize the laminar boundary layer for the airfoils and airframe having the present new engine, because air intakes of supermulti-jets can be set on the airfoils and airframe. [8] The trial of laminar airframe also assists the airvehicle of M>10.…”

“…7, 8, and 12, three-dimensional unsteady compressible Navier-Stokes equations with a weak stochasticity [17][18][19][20] were solved with a simplified two-step chemical reaction model for hydrogen and gasoline. A modified version of simple chemical reaction model, i.e., that slightly modified from the Korobeinikov scheme [25], is employed.…”

Unsteady three-dimensional computations and experiments of compression flow formed by collision of supermulti-jets

“…We used the unsteady three-dimensional compressible Navier-Stokes equations with the formulations for the velocity, pressure, density, and temperature of air in Eqs. (1)-(4) (Naitoh and Kuwahara, 1992;Naitoh and Shimiya, 2011;Shinmura et al, 2013), which include the Re-Normalization Group (RNG) subgrid turbulence model with less arbitrary constants (Yakhot and Orszag, 1986).…”

Deterministic and stochastic computations of mysterious internal flows: based on a nonlinear local correction method with global conservativity

“…Today, thermal efficiency should be improved for various power systems including combustion engines for usage on the ground as well as aerospace. Therefore, thermodynamic quantities must be evaluated accurately by computer simulations because numerical errors of a few percent regarding thermal efficiency as spatially-integral value [11,16] are often comparable to the target values set for improvement of energy systems [27,28]. However, there is a problem that most of traditional computational fluid dynamics for the deterministic compressible Navier-Stokes equation [1,2,3,4,5,6,7,8] does not aim to accurately evaluate the effects of both thermodynamic quantities including thermal efficiency, and fluid-dynamic quantities such as high-speed turbulent jets in power systems including engines, power plants, and fuel cells.…”