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Experimental studies were performed to investigate the effects of methane addition on the combustion characteristics of Chinese RP-3 kerosene/air mixture. Experiments were in a combustion vessel and the influences of methane addition on the flame propagation characteristic, Markstein length and laminar burning velocity of CH4/RP-3/air mixture at initial temperature of 420 K, initial pressure of 0.1 MPa, equivalence ratios of 0.8-1.3 and methane additions of 0.0-0.8 were investigated. Results show that with the increase of equivalence ratio, the flame front of RP-3/air mixture becomes unstable and a cellular flame structure is observed when the equivalence ratio increases to 1.3, but at the equivalence ratio of 1.3, the increased methane addition can make the flame front stable significantly. With the increase of equivalence ratio from 0.8 to 1.3, laminar burning velocities of CH4/RP-3/air mixture first increase and then decrease; the effect of methane addition on laminar burning velocity is not evident at the equivalence ratios of 0.9-1.1, but when the equivalence ratio is larger than 1.1, laminar burning velocities with methane addition of 0.8 are always the slowest. The Markstein length decreases with the increase of equivalence rati; at equivalence ratio of 0.8 the Markstein length decreases with the increase of methane addition, and with the increase of equivalence ratio the influence of methane addition on Markstein length becomes less significant and irregular. [ABSTRACT FROM AUTHOR]

A reasonable dielectric fluid velocity and better exclusion of debris are very important to obtain a stable machining performance in multi-cutting of WEDM-HS. We investigated the dynamic characteristics of multi-cutting wire electrode in WEDM-HS subjected to working fluid considering the effect of debris. First, a fluid-solid coupling nonlinear vibration model is derived by analyzing the forces acting on the multi-cutting wire which locate in the dielectric fluid. The additional axial force arising from the transverse vibration of the multi-cutting wire is considered as a nonlinear term in the model. Considering that the debris accumulation in discharge gap severely influences the stability of multi-cutting wire electrode, the relationship between the debris volume concentration and debris-working fluid two-phase flow drag coefficient is obtained using the Einstein two-phase flow viscosity theory. Finally, the influences of several parameters on the multi-cutting wire displacement are discussed in detail. [ABSTRACT FROM AUTHOR]