Cool diesel con­cept

Trio of in­jec­tors cut the hot air and in­crease the mileage

The Witness - Wheels - - INDUSTRY - AARON TURPEN — Giz­mag.

DIESEL en­gines are some of the sim­plest com­bus­tion con­cepts in use to­day, with a de­sign that has not changed much in half a cen­tury.

But what has changed is the com­plex­ity of the sys­tems that sur­round the diesel en­gine block to over­come in­her­ent in­ef­fi­cien­cies in emis­sions.

A re­search team at the New Ace In­sti­tute in Ja­pan has de­vel­oped a new diesel com­bus­tion en­gine con­cept us­ing mul­ti­ple fuel in­jec­tors that doesn’t re­quire waste heat re­duc­tion.

With a brake ther­mal ef­fi­ciency of greater than 50%, the new en­gine could re­duce en­gine man­u­fac­ture costs.

Waste heat re­cov­ery ( WHR) is com­monly used as a method of cap­tur­ing the en­gine’s heat to main­tain a tem­per­a­ture in a par­tic­u­late fil­ter and other emis­sions’ con­trol sys­tems.

WHR is rel­a­tively ex­pen­sive, but aids the ve­hi­cle’s over­all ef­fi­cien­cies in both fuel use and emis­sions re­duc­tions.

The au­to­mo­tive re­search team at New Ace sought a way to op­ti­mise com­bus­tion that over­comes the com­plex trade- offs be­tween emis­sions, brake ther­mal ef­fi­ciency ( BTE) and en­ergy losses on con­ven­tional diesel com­bus­tion.

The team’s en­gine uses three fuel in­jec­tors in a vari­ant of the Sa­bathe cy­cle. This lim­ited pres­sure, dual cy­cle con­trols heat by hold­ing con­stant vol­ume and pres­sure in the cylin­der.

The mod­i­fi­ca­tion with this new con­cept is to con­trol fuel in­jec­tion to tem­po­rar­ily cre­ate an iso­la­tion be­tween the pre­mixed com­bus­tion area and dif­fu­sion com­bus­tion area of the cylin­der, which en­ables con­sec­u­tive heat re­lease.

This is ac­com­plished by fit­ting the cylin­der with three in­jec­tors.

One is mounted ver­ti­cally at the cen­tre and two more are po­si­tioned at an an­gle on ei­ther flank at the pis­ton cav­ity’s cir­cum­fer­ence.

The side- an­gled sprays are di­rected along the swirl di­rec­tion of the air­flow, im­prov­ing mix­ing and pre­vent­ing spray in­ter­fer­ence and im­pinge­ment on the cav­ity wall.

This im­proves air mix­ing at the cen­tre of the cav­ity, which cre­ates a more dense com­bus­tion point.

Shap­ing of the pis­ton cav­ity ( crown) helps pre­vent in­jec­tion in­ter­fer­ence be­tween in­jec­tors.

By con­trol­ling in­jec­tion tim­ing and du­ra­tion un­der con­stant fuel pres­sure, heat can be con­trolled at a va­ri­ety of com­pres­sion ra­tios and op­er­at­ing tem­per­a­tures.

The cen­tre in­jec­tor fires first, fol­lowed by the pre­ci­sion tim­ing of the side in­jec­tors. Ex­per­i­men­tal re­sults for the en­gine con­cept showed that fric­tion and heat losses were re­duced. This pro­duced lower smoke and NOx emis­sions when com­pared to con­ven­tional diesel com­bus­tion.

The New ACE In­sti­tute plans to fur­ther de­velop this en­gine con­cept.

PHOTO: SUP­PLIED

Ja­panese engi­neers have de­vel­oped a diesel en­gine with mul­ti­ple fuel in­jec­tors that doesn’t re­quire cut­ting waste, thus in­creas­ing fuel use and cut­ting emis­sions.

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