DIESEL PIS­TONS

LOOK­ING FOR­WARD TO THE FU­TURE…

Ultimate Diesel Builder's Guide - - Urbg News -

Mahle’s new Top­weld steel pis­tons, the first of their kind, are de­signed to im­prove fuel econ­omy and re­duce CO² emis­sions, as well as cut pro­duc­tion costs. “The Top­weld pis­ton is the in­dus­try’s first laser-welded steel pis­ton for high-vol­ume se­ries pro­duc­tion,” said Jochen Adel­mann, head of Light Ve­hi­cle Prod­uct Tech­nol­ogy at Mahle. “The tech­nol­ogy ini­tially was de­vel­oped for use in mid-range and high-per- for­mance diesel-pow­ered pas­sen­ger cars, but there will be com­mer­cial-ve­hi­cle ap­pli­ca­tions for it as well.”

Mahle’s laser process is up to twice as fast and con­sumes con­sid­er­ably less en­ergy than fric­tion weld­ing, the join­ing tech­nol­ogy tra­di­tion­ally used to pro­duce steel pis­tons Adel­mann added that laser weld­ing also en­ables a va­ri­ety of pis­ton de­sign mod­i­fi­ca­tions that per­mit higher peak cylin­der pres­sures, in­crease engine ef­fi­ciency and re­duce op­er­at­ing tem­per­a­tures. A solid-state laser is used to join the up­per and lower por­tions of Mahle’s Top­weld high-strength pis­ton. Com­pared to fric­tion weld­ing, laser-welded seams can be po­si­tioned for op­ti­mal per­for­mance. In ad­di­tion, weld seams—which hin­der oil flow in a pis­ton’s cool­ing gallery—can be elim­i­nated. The re­sult is a bet­ter, less ex­pen­sive diesel pis­ton that achieves the im­pos­si­ble: bet­ter emis­sions and im­proved fuel econ­omy, while also be­ing stronger and lighter!

3D printed pis­tons are ac­tu­ally a thing! Why, you ask, would any­one want to print pis­tons? Ac­cord­ing en­gi­neer­ing com­pany IAV, print­ing stain­less steel pis­tons us­ing 3D ad­di­tive man­u­fac­tur­ing tech­nol­ogy is needed to meet emis­sions re­quire­ments and in­creas­ing in-cylin­der loads of up to 300 bar. Their so­lu­tion, the not-so-novel part, is to im­prove the mix of fuel and air in the com­bus­tion cham­ber. To get there re­quired a new type of pis­ton ge­om­e­try, one with un­der-cuts to ex­tend the length of in­jec­tor spray. The pis­ton has a star­shaped re­cess as a re­sult, and it’s there that the un­der­cuts oc­cur. Ad­di­tion­ally, th­ese pis­tons have a light­weight hon­ey­comb struc­ture and in­clude built-in sodium-filled cool­ing chan­nels. While that con­cept worked well in the com- puter, such in­no­va­tion re­quired 3D print­ing to ac­tu­ally build.

Pis­tons are nor­mally cast or forged from steel or an alu­minum al­loy, and each de­sign it­er­a­tion takes weeks and months. 3D print­ing re­quires only days from the CAD (com­puter aided de­sign) phase un­til a fin­ished pro­to­type of stain­less steel is com­pleted. IAV says the pro­to­type has the same qual­ity as a pro­duc­tion pis­ton. The com­pany notes that th­ese pro­to­types are also stronger and stiffer thanks to the hon­ey­comb struc­ture, as well as lighter. For now, 3D print­ing is too ex­pen­sive for pro­duc­tion vol­umes. How­ever, prices have been fall­ing for five years, so it’s not out of the realm of re­al­ity to ex­pect to see some­thing in a pro­duc­tion engine some­time rel­a­tively soon. For now, 3D printed pis­tons live only in pro­to­type en­gines.

Mahle is now on its sec­ond it­er­a­tion of this much-im­proved steel pis­ton de­signed specif­i­cally for small-medium-large diesel en­gines. As you see, pis­ton de­signs vary con­sid­er­ably based on engine size and de­mand.

Given all the ad­vances in engine tech­nol­ogy, par­tic­u­larly diesel en­gines, pis­tons like th­ese from en­gi­neer­ing com­pany IAV may hold a place in the fu­ture. For that to hap­pen, ad­di­tive man­u­fac­tur­ing must be­come main­stream.

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