The International Steam Pages
The Steam-Powered Quasiturbine in Direct-Drive Railway Propulsion
The electrical generation and drive gear in modern diesel-electric railway locomotives accounts for 30% to 50% of the locomotive capital cost. Non-electric drive systems involving the use of hydraulic transmissions in heavy mainline freight locomotives, began during the early 1960's in the USA. Results at the time were less than promising. Recent interest in using renewable bio-fuels in railway traction has renewed interest in modifying the steam locomotive for use in the modern era. Direct-drive is one of the systems being considered for its lower overall capital cost.
Several advances and breakthroughs have occurred since mainline steam locomotive operation ceased in developed nations. Advances have improved energy efficiency, reduced downtime and have enables modernised steam locomotives to rival diesel-electric locomotives in terms of their availability for service, exhaust pollution and low operating costs. Several new designs of engines have been developed over the past 40-years, including a unique, vibration-free and compact rotary engine called a "quasiturbine" (http://quasiturbine.promci.qc.ca/QTIndex.html).
The quasiturbine can be operated as an internal combustion engine as well as an external combustion engine. By adapting it to steam operation, it could be operated as a bi-directional engine, having a very high level of zero-RPM starting torque when two quasiturbines are mounted at 45-degrees to each other, on a common driveshaft. The combination of high starting torque and bi-directional rotation allows the quasiturbine to operate without the cost or complexity of either an electrical or hydraulic transmission. The compact size of the quasiturbine allows it to be mounted in the same locations as locomotive electric traction motors, that is, in the trucks (bogies) and driving powered axles through reduction gearing.
From information supplied from the webpage, a pair of quasiturbine rotors of 21-inches and 15-inches width, would be mounted on a common shaft at 45-degrees to each other. The overall exterior width would be comparable to that of an electric traction motor that is used on the 4-ft 8.5-inch railway gauge. Steam would enter the quasiturbine through inlet ports located on both sides of the centre of the minimum volume area, along the width of the inner running surface. Inlet valves using adjustable cut-off control, would be located inside the inlet ports. Only one set of inlet ports in each minimum volume area would be open to admit steam, depending on the desired direction of engine rotation. The cut-off control would adjust the duration of the steam inlet from between 15% of maximum expansion volume, up to 80% of maximum expansion volume, in both directions. Inlet valve cut-off control has proven to be the most efficient way to regulate power and speed in positive displacement steam engines, including piston steam engined locomotives.
The ability to adjust the inlet valve cut-off timing to the negative or positive sides of the centre of the minimum volume position, will enable the steam quasiturbine to operate as a bi-directional engine. If one rotor is at the minimum position, the other rotor will be 45-degrees out of phase. The articulation connecting the two rotor surfaces will be located at the centre of the minimum volume area, between the inlet ports. The selection of which set of inlet ports would admit steam, would determine the direction of engine rotation. The engine will start with a very high degree of zero-RPM torque, in either direction. This will enable the engine to operate in locomotive service.
The exhaust ports would be positioned at 90-degrees from the centre between the inlet ports, along the inside width of the rotor housing. Their location would coincide with the centre of the maximum volume position. Valves would be located inside the exhaust ports. The timing of the exhaust valves would be connected to the directional control mechanism of the inlet valves, to enable bi-directional operation. The exhaust valves would open once the rotor has reached the maximum volume position, closing 45-degrees later in either direction. Some residual low-pressure steam will remain inside the chamber and will be heated to superheat by compression, over the 45-degree angle prior to admission of a fresh charge of superheated steam. The rotor surface would be hot, reducing any thermal losses when the fresh charge of steam enters.
The positioning of the exhaust valves at 90-degrees from the centre of the inlet valves, separates the cool side of the engine from the hot side. In conventional steam piston engines, the exhaust valves and inlet valves are located right next to each other, causing an efficiency loss resulting from a cooled cylinder head and piston surface. A uniflow steam piston engine avoids this problem, by using exhaust ports located at the maximum volume position. The quasiturbine steam engine can combine the best features of the uniflow piston steam engine with the conventional engine. The superior leverage capability of the quasiturbine, combined with the separation of inlet and exhaust, will enable it to match the efficiency of a compound expansion steam engine, while using the simplicity of a single expansion system. Theoretically, due to its superior leveraging, the quasiturbine may be able to deliver higher thermal efficiency than a uniflow piston steam engine.
The compact size of the quasiturbine allows for a modern 4-axle or 6-axle diesel locomotive to serve as the basis for a modern steam locomotive. Either 4 or 6 steam powered quasiturbines may be used, depending on the desired power and operating speed of the locomotive. For intercity freight use, a speed of 60-Mi/hr (100-Km/hr) would be desired. The locomotive would use 42-inch diameter driving wheels, rotating at 480-RPM at 60-mi/hr. Insulated quasiturbines turning at 1200-RPM and driving through a 2.5:1 reduction gear may deliver optimal performance. A 300-psig insulated firetube boiler may be used, located above the frame, inside the locomotive carbody. A gas producer combustion system (GPCS) firebox would be used, burning a variety of solid fuels, including bio-renewable solid fuels made from agricultural waste.
The research of Livio Dante Porta, who pioneered the improvements now being used on modernised steam locomotives operating in numerous parts of the world, would be used. The modernised steam locomotive that pulls the New Orient Express across Western Europe, has been measured as emitting 80% fewer pollutants into the atmosphere, that a modern diesel locomotive of equivalent power. Modern research and development has solved practically all of the problems that plagued traditional steam locomotives. A modern, cost-effective and environmentally friendly steam locomotive, using quasiturbine steam engines, could become competitive against modern diesel electric railway locomotives.
Harry Valentine Transportation Researcher, firstname.lastname@example.org
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