The modern Sulzer RL crosshead diesel engine range, containing the RL 56, RL 66, RL 76, and RL 90, is now complete. This completes the development of a loop-scavenged, low-speed engine series under very largely changed conditions, where the priorities have been dominated by fuel economy and fuel quality aspects.
In the past, the development of two-stroke diesel engines has had two major priority aspects: increase in power and improvement of reliability. During the design evolution of the past 20 years, the output of the Sulzer low-speed engine was increased by 74 percent and, despite a large increase in firing pressures of approximately 55 percent, the reliability was improved substantially as a result of unprecedented development efforts.
The oil crisis in 1973 had a tremendous impact on the philosophy of engine design and development. The relative weight of fuel and lube oil cost out of the total cost has taken such a large share that it is only logical that economical aspects are now predominant criteria for the engine designer.
Major features of the RL type engine include: new type of turbocharger with increased efficiency and pressure ratio range; foundation bolts arranged in one row on the outside; bedplate with integrated thrustblock; single columns; one-piece gear column; simplified scavenge air receiver; one-piece, bore-cooled cylinder cover with eight bolts; bore-cooled (water) piston crown; bore-cooled cylinder liner; enlarged crosshead pin with improved lube-oil feeding system; integrated balancer for 4-, 5-, and 6-cylinder engines (optional); PUP cancel valve (piston underside); and modified fuel injection system with standard variable injection timing mechanism.
The impact of the changed priorities as a result of sharply increased fuel cost on the design of the RL series was very strong. Overall economy is now exploited on a much larger scale than hitherto, and waste heat recovery is an important aspect. As a result of outstanding development efforts, the fuel consumption rates of the loop-scavenged crosshead engine are now extremely low and quite competitive with other systems.
Reliability and simplicity, combined with optimum suitability for low-quality fuel, are the basic assets of this type of engine and will continue to be an extremely important aspect for marine propulsion machinery.
Claim was recently laid to probably one of the lowest specific fuel consumption rates for any long-stroke diesel engine built in series. A 4-cylinder Sulzer RLA 90 engine—converted to the RLB specification — is said to be the first such engine to break the 130 gram fuel barrier. With a specific fuel consumption of 129.1 grams per horsepower-hour, or nearly 3 grams under the guaranteed fuel rate for this series, this crosshead engine built by Sumitoma Heavy Industries in Japan has a maximum continuous rating of 13,600 bhp at 90 rpm.
In its continuous effort to meet all the stringent future demands imposed on diesel engines for both marine and stationary purposes, Sulzer has now further developed its highly successful series of Z 40 medium-speed engines.
All the well-proven inherent advantages of the Z 40 engine design have been incorporated in the new engine, and maximum use has been made of the experience gained from the considerable number of service hours with heavy fuel. The outcome of this development is the ZA 40, one of the most technologically advanced, medium-speed engines on the market. Among other things, this design offers a greatly reduced specific fuel consumption, a better capability to burn low-quality fuels, a highly efficient and economical cylinder lubrication, a greater potential for efficient waste heat recovery, facilitated maintenance, and an increased output.