MAN low speed engines

Low speed marine diesel engines built by Maschinenfabriek Augsburg-Nurnberg (MAN) were of single-acting two-stroke crosshead design exploiting loop scavenging. The programme was phased out after the German company's acquisition of Danish-based rival Burmeister & Wain in 1980 and replaced by the MAN B&W MC series (Chapter 10). MAN's KSZ design (Figure 15.1) was introduced in the mid-1960s and followed progressively by the KSZ-A, KSZ-B and KSZ-C types, each embodying refinements to promote greater reliability and fuel economy. The KSZ-C and KSZ-CL types represented the last examples of MAN loop-scavenged engine design technology.

MAN engines had some notable features to promote simplicity of design, ease of maintenance and low specific fuel consumption, not least the pioneering application—albeit only on the testbed—of electronic fuel injection to a marine diesel engine.

MAN two-stroke engines employ constant pressure turbocharging (Figure 15.2) and are scavenged according to the loop scavenging system. The cylinder exhaust ports are located above the scavenging ports on the same side of the liner, occupying approximately one-half of its circumference. The scavenging air is admitted through the scavenge ports, passing across the piston crown and ascending along the opposite wall to the cylinder cover, where its flow is reversed. The air then descends along the wall in which the ports are located, expelling the exhaust gases into the exhaust manifold. The piston closes the scavenging ports and then, on its further upward travel, also closes the exhaust ports compressing the charge of pure air in the cylinder.

When the KSZ series was introduced it followed the traditional two-stroke engine construction technique of cylinder blocks mounted on 'A' frames which sat on a cast bedplate, the three structural items held by a series of long tie-rods. However, this method of erection was abandoned when MAN introduced the KSZ-B type with the so-called box-type construction which was retained for the later KSZ-C and KEZ-B types. (This latter type was identical to the KSZ models but featured electronic fuel injection—described below—instead of the traditional mechanical fuel pump arrangement; however, it never

Figure 15.1 Cross-section of KSZ 90/160 engine with older constant pressure parallel injector supercharging system
Figure 15.3 K8SZ 90/160 B/BL engine on the testbed

Speed (rev/min)

Figure 15.4 Performance curves for the K8SZ 90/160 engine

Speed (rev/min)

Figure 15.4 Performance curves for the K8SZ 90/160 engine entered production.) In general design details the KSZ-B and KSZ-C engines are basically similar but for the longer piston strokes of the latter series and other refinements to achieve a considerable reduction in the specific fuel consumption.

Figure 15.5 Cutaway drawing of K8SZ 90/160B/BL engine
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