Measure of Friction losses on Common Rail Engine

with another direct injection engine equipped with amechanical injection pump, and an indirect injectionengine.4.54<strong>Friction</strong> <strong>losses</strong> comparaisonIDI Complete versionHDI Complete versionThe wearing period was established with a 15 hours cycle<strong>of</strong> different engine speed and load. This cycle wasrepeated until the stability <strong>of</strong> fuel consumption and friction<strong>losses</strong>. This engine was considered stabilized after 100hours.The stage by stage cutting up <strong>of</strong> the Common Rail engineshows the influence <strong>of</strong> the different constitutive parts. Thefriction <strong>losses</strong> repartition is the following:• The moving parts represent 20 % <strong>of</strong> the global friction<strong>losses</strong> and 0.5 % for crankshaft.• The cylinder head, the pumping and the timingrepresent 50 %• The intake and exhaust <strong>losses</strong> represent 20 % and18 % because <strong>of</strong> the turbocharger and the exhaustaerodynamic <strong>losses</strong>• Balance is due to accessories.To be more precise, the tests show that the friction torquegenerated by the top ring can grow up to 2N.m and that itis responsible for 3% <strong>of</strong> the global friction <strong>losses</strong>.Comparison between direct injection, commonrail and indirect diesel engineBecause <strong>of</strong> the accessories and engine parameterdifferences, the comparison between these 3 diesel enginetechnologies is not easy. Nethertheless tests show thatsome implicit rules can be drawn from results.All the results go to prove the importance <strong>of</strong> the <strong>losses</strong> <strong>of</strong>charge generated by swirl formation in a direct injectiondiesel engine (Fig. 6). Intake <strong>losses</strong> <strong>of</strong> charge grow up to20% less at 4000 rpm for an indirect injection engine thanfor a direct one. Even if the difference between the 2 directinjection engine is not huge, one can suppose that higherinjection pressure could decrease the swirl requirements.That could be why the Common Rail pumping <strong>losses</strong> areless important than the DI ones. But this result should beproved by other experiments, especially with a swirlmeasurement in these cylinder heads.As far as the moving parts are concerned, differencesmeasured cannot show any hierarchy between CommonRail and DI engines. Yet the friction <strong>losses</strong> due to themoving parts are less important for a direct injectionengine than for an indirect one.The working principle <strong>of</strong> a direct injection engine inducesthermal stresses that have drawn piston, rod, andcrankshaft to be heavier. As a result, their friction <strong>losses</strong>should be more important. Despite the indirect injectionengine generation is older than the direct one, so one canthink than technological progress have taken the level <strong>of</strong>this trend.M.F.P. (bar)3.532.521.510.50CONCLUSION1500 Engine speed (rpm)4000Fig. 6DI Complete verisonIDI pumping+intake+exhaustHDI pumping+intake+exhaustDI pumping+intake+exhaustIDI cranckshaftHDI cranckshaftDI cranckshaftIDI piston+rod+ringsHDI piston+rod+ringsDI piston+rod+ringsThe study driven on this engine has given data consideringthe choices and the testing means limits. The differencesmeasured during the stage by stage cutting up are sensitiveenough so that experiment planning is not necessary tocompare an engine to similar ones. Nevertheless, if the aim<strong>of</strong> the study is to evaluate mechanical <strong>losses</strong>, which aresmaller than the incertitude <strong>of</strong> repeatability orreproducibility, an experiment planning is unavoidable.Yet other ways can be explored such as amplification <strong>of</strong>phenomenon. For example, in order to compare thefriction <strong>losses</strong> generated by different top ring geometry, itis possible to increase the engine speed <strong>of</strong> the test or to usea special piston equipped with several similar top rings. Acomplementary solution could be the use <strong>of</strong> a torquemeterwhich sensibility is compatible with the measure.Oil and fuel consumption reduction and the correlationwith friction loss simulations will need furtherinvestigations in top ring geometry. To this end, this kind<strong>of</strong> testing bench is appropriated to keep abreast <strong>of</strong> thatdomain.REFERENCES[1] Heywood.J.B – 930p 1988a Mc Graw-Hill – NewYork. Internal combustion enginefundamentals[2] Young Cheng – SAE technical paper 982686 - The online estimation <strong>of</strong> the power performance and mechanical<strong>losses</strong> <strong>of</strong> engines.4