Impact of Turbocharger Compressor Pressure Ratio on Diesel Engine Performance and Nitrogen Oxides Emissions

Turbochargers is used on several engines since 1962, to gain greater power output. This paper presents a study of the impact of the turbocharger pressure ratio on diesel engine performance and nitrogen oxides (NOX) emissions. A series of simulation experiments were carried out by using Diesel-RK software on variable turbocharger pressure ratio diesel engine. Diesel-RK is known as a very good open source software for youthful researchers, since it is free and talented of simulating combustion and thermodynamics of diesel engines very well. The simulated results showed that, turbocharger pressure ratio (PR) is an important parameter which affects directly on engine performance, engine brake power (BP) increased when pressure ratio increased. At 2500rpm and pressure ratio equal to 1.5 the BP increment about 27.4% when compared to natural aspirated (NA) engine. More increment about 55% is achieved by increasing the pressure ratio to 2.5. Though the specific fuel consumption (SFC) reduced as the pressure ratio increased. At 4000rpm and pressure ratio equal to 1.5 the SFC reduction about 5% when compared to NA engine. More decrement rate in the SFC rate about 7% is achieved by increasing the turbocharger pressure ratio to 2.5. The brake thermal efficiency (BTE) also increased as the pressure ratio increased, due to increase in power. At NA engine and 3000rpm, the BTE is found to be 32.5%, while at PR = 1.5, the BTE is equal to 33.9% and the BTE at the PR equal to 2.5 is increased to 33.8%. On the other hand engine NOx emissions increased as the pressure ratio increased, at 3000rpm and PR equal to 1.5, the NOX rate increased at a rate of 20% when compared to the emissions of NA engine. NOX emissions continuously increased and reached more than 42% with PR equal to 2.5 when compared to NA engine. Turbocharger gives the small displacement engines much more power relative to their size e.g. PR equal to 2.5, turbochargers run off energy of exhaust gases that is always lost by the NA engines, so the recovery of this energy develops the engine efficiency.