(2-03) A Study on Direct Injection Gasoline Combustion using Constant Volume Combustion Vessel : Diagnostics of Stratification Degree affected by Major Design Factors((SI-1)S. I. Engine Combustion 1-Direct Injection Engines)

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Stratification features of DI gasoline combustion were studied, using a constant volume combustion vessel system shown in Fig. I. Indicated pressure analysis and high speed combustion observation were carried out. Though the heating efficiency η_h obtained was very low because of constant volume combustion, the relative diagnosis of initial mixture formation among design factors was judged to be possible. The factors studied were spray cone angle, swirl ratio SR and ambient temperature Ta. Ambient pressure Pa was kept constant. The effects of injection-sparking interval τ_<int> were examined. The ignition delay τ_d, defined as the time from sparking to ignition, plotted against τ_<int> were greatly scattered. This also caused the great scattering in both η_h and maximum pressure rise rate (dp/dt)_<max>. These scattering, however, were significantly reduced by plotting the data against total ignition delay τ_<tot>(=τ_<int>+τ_d), as shown in Fig. II. Clearly, both η_h and (dp/dt)_<max> decrease against τ_<tot>, and (dp/dt)_<max> decreases more rapidly than η_h. A maximum volumetric burning velocity (Sv)_<max>, which closely correlates with (dP/dt)_<max>, was proposed as the stratification degree, based on a thermodynamic consideration under such concept that higher stratification degree brings wider area of stoichiometric mixture and this result in higher burning velocity as well as less amount of unburned fuel. Fig. III compares the best values of both (Sv)_<max> and η_h, given at the shortest τ_<tot> as shown in Fig. II. for each design factor. It is noteworthy that, as spray cone angle is widened, (Sv)_<max> become higher and less affected by SR.
一般社団法人日本機械学会の論文
2001-07-01

(2-03) A Study on Direct Injection Gasoline Combustion using Constant Volume Combustion Vessel : Diagnostics of Stratification Degree affected by Major Design Factors((SI-1)S. I. Engine Combustion 1-Direct Injection Engines)

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