Turbulent Flow in Spark Ignition Engine Combustion Chambers

Turbulent flame propagation and combustion in spark ignition engines

“…(27) can be combined with Eqs. (23)- (26) to obtain the relations (28) and (29) For (R + r e -rb) < rb, which is the case at maximum burning rate, (R + re -rb)ab ------0r/2)(V--vb), (30) and for Ou/Pb approximately constant as shown in A plot of 0a as a function of 0B' for all cycles is shown in Fig. 17a and a plot of the ratio 0B'/0 B as a function of re* is shown in Fig.…”

A correlation for turbulent combustion speed accounting for instabilities and expansion speed in a hydrogen-natural gas spark ignition engine

“…First, the flow is nonstationary, but markedly cyclic because of the reciprocating piston motion. Second, the flow velocities inside the combustion chamber are proportional to the average piston speed [10][11][12] . These velocities are generated mainly by intake and compression processes.…”

“…These velocities are generated mainly by intake and compression processes. Correspondingly, the turbulence intensity is proportional to the engine speed [12][13][14][15] . Third, the combustion chamber walls confine the flow and the distance between them determines the integral length scale [10 , 14 , 16] .…”

“…The amplitude of the instabilities, A , depends on the rate of growth, ω, but also on the time elapsed since the instability had a certain initial amplitude A 0 . Choosing a characteristic time as the time that the flame front takes to travel the integral length scale eddy, L I / S l , an initial amplitude equal to the thickness of the flame front, δ l , and an instability wavelength equal to the integral scale, L I , the amplitude of the instability would have the expression of L I (12) This increased thickness of the flame front, δ l e ω L I S l , can replace the laminar flame front thickness in Eq. ( 11) and be used to obtain an expression of S t / S l of the form of Eq.…”

Discussion: “A One-Dimensional Variable Area Computer Simulation of Combustion in a Divided Chamber, Stratified Charge Engine” (Boni, A. A., Chapman, M., and Schneyer, G. P., 1976, ASME J. Eng. Power, 98, pp. 441–446)

“…However, two features of spatial models restrict their usefulness-the necessary specification of both the mean turbulence field within the engine cylinder and the chemical kinetics that control combustion of hydrocarbon fuels. It is known that, in general, the turbulence field is highly nonisotropic [20,21] and dependent on many engine design and operating parameters. Similarly, more detailed chemical kinetics will be necessary to simulate such phenomena as engine knock for which preflame reactions are important.…”