Stochastic determinism for capturing the transition point from laminar flow to turbulence

Naitoh, Ken; Shimiya, Hiromu

doi:10.1007/s13160-011-0033-1

Cited by 41 publications

(14 citation statements)

References 14 publications

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“…As boundary conditions during compression, combustion and expansion processes, Neumann, Dirichlet and no-slip conditions are used for computing pressure, temperature and velocity components on the wall surface, respectively (3,4,9) . Boundary condition of the flame front is also considered (3,4) .…”

Section: Governing Equation and Numerical Methodsmentioning

confidence: 99%

“…The present model enables us to simulate the flow field with random disturbance given at the edges of intake ports during the intake process by using the nonlinear stochastic Navier-Stokes equation with chemical reaction (8)(9)(10) . The computations are done at the inlet disturbance condition of 4.10 % (Crank angle = 90 deg.…”

Section: Cyclic Variations Of Combustion In Stratified-charge Direct mentioning

confidence: 99%

“…The present computational model based on the stochastic Navier-Stokes equation (8)(9)(10) can also simulate the transition point from laminar flow to turbulence in the intake ports of piston engine while atmospheric turbulence level outside the engine system, i.e., turbulence level at the inlet of intake ports, varies. The transition point to turbulence and turbulence intensities in the intake ports have an important influence on cyclic variations of air flows and combustion instabilities.…”

Section: Appendixmentioning

confidence: 99%

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

Shinmura

Kubota

Naitoh

2013

JTST

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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.

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Section: Governing Equation and Numerical Methodsmentioning

confidence: 99%

Section: Cyclic Variations Of Combustion In Stratified-charge Direct mentioning

confidence: 99%

Section: Appendixmentioning

confidence: 99%

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

Shinmura

Kubota

Naitoh

2013

JTST

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“…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.…”

Section: Combustion Computationsmentioning

confidence: 99%

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

Naitoh¹,

Ishida²,

Nonaka³

et al. 2014

50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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A new compression principle based on super multijets colliding with pulsation (Naitoh et al, 2010, 2011, 2012, 2013) has an impressive potential for engendering a new single lightweight engine capable of operating over a wide range of Mach numbers from startup to the hypersonic regime with high thermal efficiency and low noise for hypersonic aircars, while this principle can also improve traditional turbofan and ram-scram jet engines and generates small engines for automobiles and personal power generators with high efficiencies. Flow experiments using a shocktube and combustion tests of two prototype engines, computational fluid dynamics with a chemical reaction model, and theoretical fluid mechanics clarifies the potential of high thermal efficiency and stability of this engine system, although our previous computations (Naitoh et al, 2011, 2012) are very qualitative. Especially, in this report, unsteady three-dimensional computations for this engine system extended with a piston for low subsonic Mach number M< 0.3, computations for transonic operation during various continuous cycles, and computations of combustion for M>3 are shown in details. These computations will reveal the concrete specification including the number and size of nozzles of supermultijets colliding, which is necessary for achieving high thermal efficiency over 60%, even for small engines. Then, primitive testes done for two prototype engines also indicate possibility of combustion occurence. Nomenclature M = Mach number T = Temperature N = The number of nozzles for supermulti-jets colliding D = Combustion chamber diameter d = nozzle diameter of supermulti-jets Ne = Engine speed (Piston revolution per minute: rpm)

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“…Three-dimensional compressible Navier-Stokes equations were solved with a simplified two-step chemical reaction model. The cubic interpolated pseudo-particle (CIP) method [4] applied for the governing equation of the multi-level formulation [5,6,7] was employed, which is suitable for calculating both compressible and incompressible problems.…”

Section: Outline Of the New Single Enginementioning

confidence: 99%

A new cascade-less engine operated from subsonic to hypersonic conditions: designed by computational fluid dynamics of compressible turbulence with chemical reactions

2010

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A new cascade-less engine operated from subsonic to hypersonic conditions: designed by computational fluid dynamics of compressible turbulence with chemical reactions By using our computational fluid dynamic models, a new type of single engine capable of operating over a wide range of Mach numbers from subsonic to hypersonic regimes is proposed for airplanes, whereas traditional piston engines, turbojet engines, and scram engines work only under a narrower range of operating conditions. The new engine has no compressors or turbines such as those used in conventional turbojet engines. An important point is its system of super multijets that collide to compress gas for the transonic regime. Computational fluid dynamics is applied to clarify the potential of this engine. The peak pressure at the combustion center is over 2.5 MPa, while that just before ignition is over 1.0 MPa. The maximum power of this engine will be sufficient for actual use. Under the conditions of higher Mach numbers, the main intake passage located in front of the super multijet nozzles, takes in air more. That results in a ram or scramjet engine for supersonic and hypersonic conditions.

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Stochastic determinism for capturing the transition point from laminar flow to turbulence

Cited by 41 publications

References 14 publications

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

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

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

A new cascade-less engine operated from subsonic to hypersonic conditions: designed by computational fluid dynamics of compressible turbulence with chemical reactions

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