The Slowest Rotating Internal Combustion Engines: A Comprehensive Analysis

When discussing the slowest rotating internal combustion engines, one cannot help but be captivated by the diversity of designs and applications across different sectors, from tractors to ships. Each type of engine has its unique characteristics and operational demands, which define their slowest rotational speeds.

The Historical Context of Slow-Rotating Diesel Engines

The slowest rotating internal combustion engines can be found in various historical contexts. For instance, the 'putt-putt' or 'pop-pop' one-cylinder diesel engines, popular in some older applications, might operate at a nominal speed of around 60 revolutions per minute (RPM). However, the true giants among slow rotating engines are found in large-scale industrial applications, such as those in ships.

Steam and Diesel Giants: The True Slow Pockers

There are notable contenders among the slowest rotating internal combustion engines. The Sulzer-designed two-stroke diesel engine, which powers ocean-going ships, is a significant example. This behemoth engine produces over 100,000 brake horsepower and makes about three revolutions per minute. While the exact figures might require verification, these numbers highlight the immense size and capacity of these engines.

Moreover, there are reports of large diesel ship engines running at speeds as low as 100 RPM or even lower. One observer noted the BW Nr. 1 - DieselHouse engine, which redlines at 180 RPM, raising the question of whether this engine could be running slower. Additionally, the Slow Speed Cylinder (SSC) engines, often manufactured by the BWSC or similar companies, are designed to run on heavy fuel oil (Bunker C) and can have rotational speeds as low as 90 RPM.

Unique Features of Slow-Rotating Engines

Apart from sheer size and brute force, these slow rotating engines exhibit unique features that are crucial for their function. For instance, the ability to run backward, demonstrated by a YouTube video of a tractor, suggests the engines can operate at 0 RPM. This feature is particularly advantageous in emergency situations or for maintenance purposes.

Modern Giants: Ship Diesel Engines

Berthold Wilm, a German engineer, designed the RTA96 engine, which powers ships and currently holds the record for the slowest diesel engine. With each cylinder displacing 1,800 liters, the engine redlines at 120 RPM, but it can operate at 25 RPM, a speed that might require a very large flywheel to maintain smooth operation. Each of the 14 cylinders produces 80 megawatts of power, making it an engineering marvel.

Interestingly, many large rail and marine diesel engines run at approximately 600 RPM, while very large shipping engines run around 200 RPM. The Wartsila-Sulzer RTA96-C engine, a candidate for the slowest rotating engine, demonstrates the efficiency and robustness of slow-speed diesel engines. Despite its colossal size, it can achieve a breathtaking 80 MW of power, showcasing the importance of low RPM in marine applications.

Finding the Very Slowest Engine

While exact records for the slowest engines are hard to come by, the RTA96 engine is often cited as a potential contender. However, the true contender for the slowest may be the

Conclusion

The slowest rotating internal combustion engines represent the pinnacle of engineering achievement and efficiency, particularly in industries such as marine transport. As technology advances, the role of these engines continues to evolve, but their unique characteristics remain a testament to human ingenuity and the challenges of engineering on a grand scale.