Throttling Effect on the Performance and Emissions of a Multi-Cylinder Gasoline Fuelled Spark Ignition Engine

Abstract

The throttle mechanism, a regulatory technique of engine output, is accompanied by a loss of some energy. The effect of intake air throttling on the performance and emissions of a multi-cylinder spark ignition gasoline engine was experimentally investigated. The engine was coupled to a hydraulic dynamometer equipped with a customized cooling system for both the engine and dynamometer. Experimental tests were performed for various engine speeds and air-fuel ratios at the WOT and POT conditions with optimized ignition timing. The acquired results recorded that a better engine operation could be achieved with WOT in terms of bmep, bsfc, ηb, CO, CO2 and UHC compared to POT. At the same time, the worst trend at WOT was noticed for the NOx concentration due to the higher conversion efficiency of fuel combustion. In terms of engine speed for both WOT and POT conditions, operating at 3000 rpm represents the minima of ϕ, bsfc, CO and UHC; and the maxima of ηb, CO2 and NOx with some fluctuation on both sides of this point. Maximum recorded values of ηb were about 30.55% and 28. 55%, while the minimum values of bsfc were about 274 and 293 g/kW.h for the WOT and POT conditions, respectively. The maximum bmep was obtained at 2500 rpm at WOT and POT conditions with values of about 940 kPa and 904 kPa, respectively. Maximum recorded values of NOx were about 1525 and 977 ppm for the WOT and POT conditions, respectively.

Throttling effect on the availability and sustainability of a gasoline-fuelled spark ignited multi-cylinder engine

“…Consequently, the concentrations of CO 2 and NO x species increased; while the concentrations of CO and HC species in the exhaust stream decreased. This trend of the emitted gases indices as the throttle opening widen well matches with formerly published data [29]. However, there are inconsistencies in the values of other published works [39,48], which might be mainly owing to the smaller size of their tested engines.…”

“…It can be revealed that there was an increment in entropy generation under the POT condition compared to the WOT condition for all the tested engine speeds, except 2500 and 3500 rpm, which exhibited different trends. Such deviation of the entropy generation trend might be due to the mechanical failure of the throttle controller due to vibration resonance [29]. This trend is seemed to be governed in somewhat by the noticed trend of the AFR (see tables 5 and 6).…”

“…However, the most preferable operation mode for the recovery potential was the WOT condition for all the tested engine speeds except 2500 and 3500 rpm. Such deviation of the recovery potential trend might be due to the mechanical failure of the throttle controller at 2500 and 3500 rpm due to vibration resonance [29]. Again, there is an optimum operating condition for the engine speed, namely 3000 rpm, for both the WOT and POT conditions.…”

“…50% or 100%, using the control knob of the throttle body. A tailored mechanism was in-lab fabricated and tuned to control the throttle body of the carburetor opening [29]. On other hand, the hydraulic dynamometer was manually controlled using a control lever to adjust the applied load on the tested engine.…”

“…While two throttle positions, i.e., 50% and 100% opening, were attained by the throttle lever. Therefore, the imposed load by the dynamometer produced the highest potential torque of the tested engine in each condition [29]. The experimental data were collected for running the tested engine under various rotational speeds, i.e., 1500, 2000, 2500, 3000, 3500, and 4000 rpm.…”