Full steam ahead for BMW’S clean cars

Yorkshire Post - Motoring - - NEWS -

EVEN the most ef­fi­cient in­ter­nal com­bus­tion en­gine can only con­vert about one-third of the en­ergy de­rived from fos­sil fu­els into the ki­netic en­ergy needed to power a mo­tor ve­hi­cle. En­gi­neers are work­ing flat-out to find im­prove­ments, as the in­dus­try at­tempts to be all things to all men.

At BMW, for ex­am­ple, what it calls Ef­fi­cien­tDy­nam­ics (ie Blue­mo­tion, Green­line, ECOflex etc at other car­mak­ers) has made great im­prove­ments in en­gine ef­fi­ciency, with tech­nolo­gies such as di­rect fuel in­jec­tion, vari­able valve tim­ing, ex­haust­driven tur­bocharg­ers, brake en­ergy re­gen­er­a­tion and the Auto Start Stop func­tion.

How­ever, about 60 per cent of the gen­er­ated en­ergy is still lost as heat. Find­ing ways of re­cov­er­ing this lost heat en­ergy is one of the ma­jor goals be­ing pur­sued by en­gi­neers work­ing on BMW Ef­fi­cien­tDy­nam­ics.

En­ter, the tur­bosteamer. “A heat ex­changer re­cov­ers heat from the en­gine ex­haust, and this en­ergy is used to heat a fluid which is un­der high pres­sure – this heated fluid then turns into steam, which pow­ers an ex­pan­sion tur­bine that gen­er­ates elec­tri­cal en­ergy from the re­cov­ered heat,” ex­plains Jür­gen Rin­gler, team leader for Ther­mal En­ergy Con­vert­ers at BMW Group Re­search and Tech­nol­ogy.

In­tel­li­gent heat man­age­ment can also re­duce con­sump­tion when the ve­hi­cle is be­ing ac­cel­er­ated and driven. Be­fore start­ing the car, in­su­la­tion and en­cap­su­la­tion of the en­gine com­part­ment will shorten the cold start phase.

An ex­haust heat ex­changer will keep gear­box oil warm to re­duce fric­tion and con­sump­tion. The tur­bosteamer will pro­vide elec­tri­cal sys­tems with am­ple power, too.

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