Fischer-Tropsch (F-T) diesel fuel is characterized by a high cetane number, a nearzero sulphur content, and a very low aromatic level. In the present paper, the performance and emissions of an unmodified single-cylinder direct injection diesel engine operating on F-T diesel fuel are studied and compared with those of conventional diesel fuel operation. The results show that F-T diesel fuel exhibits a slightly longer injection delay and injection duration, displays an 18.7 per cent average shorter ignition delay, and has a lower peak value of premixed burning rate and a higher peak value of diffusion burning rate than conventional diesel fuel. The engine with F-T diesel fuel has a slightly lower peak combustion pressure and a far lower rate of pressure rise, and consequently a lower mechanical load and combustion noise compared with conventional diesel fuel. In addition, the brake specific fuel consumption is lower and the brake fuel conversion efficiency is higher for F-T diesel fuel operation. The CO 2 , HC, CO, NO x , and smoke emissions with F-T diesel fuel are reduced at all operating conditions when compared with conventional diesel fuel. On average, NO x and smoke emissions are reduced by 16.7 and 40.3 per cent respectively with F-T diesel fuel. The study demonstrates that F-T diesel fuel is an excellent clean alternative fuel for diesel engines.
Effects of Fischer-Tropsch (F-T) diesel fuel on the combustion and emission characteristics of a singlecylinder direct injection diesel engine under different fuel delivery advance angles were investigated. The experimental results show that F-T diesel fuel exhibits shorter ignition delay, lower peak values of premixed burning rate, lower combustion pressure and pressure rise rate, and higher peak value of diffusion burning rate than conventional diesel fuel when the engine remains unmodified. In addition, the unmodified engine with F-T diesel fuel has lower brake specific fuel consumption and higher effective thermal efficiency, and presents lower HC, CO, NO x and smoke emissions than conventional diesel fuel. When fuel delivery advance angle is retarded by 3 crank angle degrees, the combustion duration is obviously shortened; the peak values of premixed burning rate, the combustion pressure and pressure rise rate are further reduced; and the peak value of diffusion burning rate is further increased for F-T diesel fuel operation. Moreover, the retardation of fuel delivery advance angle results in a further significant reduction in NO x emissions with no penalty on specific fuel consumption and with much less penalty on HC, CO and smoke emissions.
In this paper, the in-cylinder mixture formation process of a two-stroke spark-ignition direct-injection(SIDI) diesel engine is simulated and analyzed. The effects of the shape of the combustion chamber, the injection time and the initial temperature of the engine on the mixing process and the performance of the SIDI diesel engine are analyzed. The simulation results show that the offset combustor can obviously improve the fuel economy of the SIDI diesel engine. Under the premise of constant fuel injection quantity, there is an optimal fuel injection time to make the power performance and economy of the SIDI diesel engine optimal. Increasing the initial temperature is beneficial to the atomization of diesel oil and the formation of diesel mixture in cylinder. The results will guide the engineering design of SIDI diesel engine.
According to 8-Mode cycle of measurement methods for non-road diesel engine of China III from GB20891-2014, the effects of the injection parameters on steady emission characteristics were researched on an opposed-piston two-stroke(OP2S) diesel engine. Test results show that nozzle-tip-protrusion(NTP) can’t make a big influence on emission characteristics, but all of the CO, NOx and PM emissions decrease obviously with the increase of injector hole diameter. Moreover, there exists an optimal nozzle hole cone angle, which can lead to a least composite rate emission. Compared with the original engine, the gross emissions of NOx and HC decrease approximately by 17.2% for improved OP2S engine after nozzle parameters optimization matching, and the improved OP2S engine is able to meet non-road diesel engine of China III emission requirement.
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