Diesel Distributor Fuel-Injection Pumps VE - Gnarlodious

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Axial-pistondistributorpumpsHole-type nozzlesApplicationHole-type nozzles are used with in-lineinjection pumps on direct-injection engines.One differentiates between:– Sac-hole, and– Seat-hole nozzles.The hole-type nozzles also vary accordingto their size:– Type P with 4 mm needle diameter,and– Type S with 5 and 6 mm needle diameters.Design and constructionThe spray holes are located on the envelopeof a spray cone (Fig. 4). The numberof spray holes and their diameter dependupon:– The injected fuel quantity,– The combustion-chamber shape, and– The air swirl in the combustion chamber.The input edges of the spray holes canbe rounded by hydro-erosive (HE) machining.Fig. 4Spray coneγ Spray-cone offset angle, d Spray cone.γAt those points where high flow ratesoccur (spray-hole entrance), the abrasiveparticles in the hydro-erosive (HE) mediumcause material loss.This so-called HE-rounding process canbe applied to both sac-hole and seat-holenozzles, whereby the target is:– Prevent in advance the edge wearcaused by abrasive particles in the fueland/or– Reduce the flow tolerance.For low hydrocarbon emissions, it ishighly important that the volume filledwith fuel (residual volume) below theedge of the nozzle-needle seat is kept toa minimum. Seat-hole nozzles are thereforeused.DesignsSac-hole nozzleThe spray holes of the sac-hole nozzle(Fig. 5) are arranged in the sac hole.In the case of a round nozzle tip (Fig. 6a),depending upon design the spray holesare drilled mechanically or by means ofelectrochemical machining (e.c.m.).Sac-hole nozzles with conical tip (Figs.6b and 6c) are always drilled using e.c.m.Sac-hole nozzles are available– With cylindrical, and– Conical sac holesin a variety of different dimensions.Sac-hole nozzle with cylindrical sac holeand round tip (Fig. 6a):This nozzle’s sac hole has a cylindricaland a semispherical portion, and permitsa high level of design freedom withrespect to– Number of spray holes,– Spray-hole length, and– Injection angle.48δUMK1402YThe nozzle tip is semispherical, andtogether with the shape of the sac hole,ensures that the spray holes are ofidentical length.
Sac-hole nozzle with cylindrical sac holeand conical tip (6b):This type of nozzle is used exclusivelywith spray-hole lengths of 0.6 mm. Thetip’s conical shape enables the wallthickness to be increased between thethroat radius and the nozzle-body seatwith an attending improvement of nozzletipstrength.Sac-hole nozzle with conical sac holeand conical tip (Fig. 6c):Due to the conical shape of this nozzle’ssac hole, its volume is less than that of anozzle with cylindrical sac hole. Thevolume is between that for a seat-holenozzle and a sac-hole nozzle with cylindricalsac hole. In order to achieve uniformtip-wall thickness, the tip’s conicaldesign corresponds to that of the sachole.Nozzlesand nozzleholdersFig. 5Sac-hole nozzle1 Pressure shaft, 2 Needle-lift stop face,3 Inlet passage, 4 Pressure shoulder,5 Needle shaft, 6 Nozzle tip,7 Nozzle-body shaft, 8 Nozzle-body shoulder,9 Pressure chamber, 10 Needle guide,11 Nozzle-body collar, 12 Locating hole,13 Sealing surface,14 Pressure-pin contact surface.Fig. 6Sac-hole shapesa Cylindrical sac hole with round tip,b Cylindrical sac hole with conical tip,c Conical sac hole with conical tip.1 Shoulder, 2 Seat entrance, 3 Needle seat,4 Needle tip, 5 Injection orifice,6 Injection-orifice entrance, 7 Sac hole,8 Throat radius, 9 Nozzle-tip cone,10 Nozzle-body seat, 11 Damping cone.a1234511109876bcUMK1403YUMK1650Y49
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Page 66: The ProgramOrder NumberGasoline-eng

Diesel Distributor Fuel-Injection Pumps VE - Gnarlodious

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