Effect of Primary Intake Runner Tapers and Bellmouths on the Performance of a Single Cylinder Engine

The present experimental study investigates systematically the effects of primary intake runner configurations on a firing single cylinder research engine. Twelve different intake configurations were fabricated to investigate runners with tapers and bellmouths. For each configuration, the length from the base of the test configuration to the start of the inlet radius and pressure measurement locations were retained in an effort to isolate the effect of runner geometry only. Each configuration is presented against a baseline case with constant cross-sectional area and a ratio of inlet radius, R_i, to internal diameter, D, of 0.35. For the seven tapered runners, the length of the taper varied from 25% to 100% of the overall length of the test piece, and the taper area ratios (TAR) varied from 1.5 - 3; all tapers retained the inlet radius of the baseline. The four bellmouth runners had a constant cross-sectional area, and varying inlet radii from R_i/D = 0.05 to 1.0. The time-averaged quantities such as volumetric efficiency and brake power, and time-resolved intake pressures are presented for each configuration. For the bellmouth runners, R_i/D > 0.20 was found to be most beneficial to volumetric efficiency, and a TAR larger than 1.5 was detrimental to the intake tuning for higher-speed tuning peaks.