The Square Piston Engine (SPEC) represents the next stage in the evolution of the reciprocating internal combustion engine. It is a two-stroke engine with a square piston. In essence, the SPEC has a superior power-to-weight ratio compared to existing two-stroke engines. However, more importantly, it has significantly reduced emissions achieved by more complete combustion and a closed-loop oiling system. The engine is also modular in design, which provides significant manufacturing flexibility. The SPEC engine leverages existing two-stroke engine technology (lightweight, powerful, three moving parts only, cheap to manufacture, etc.) and at the same time eliminates the disadvantages. The port placement delays the opening of the exhaust port on the power stroke, yielding more torque and much lower emissions. A number of prototypes have been constructed and have operated on a variety of fuels. One such prototype has run in excess of 500 hours. Further development work is required to enhance engine efficiency through software modeling of port placement.
Technology Benefits Description
The SPEC engine provides a number of benefits over existing engine design. These include:
- The engine is two-stroke by design, providing a superior power to weight ratio over comparable four-stroke engines. It leverages existing engine technologies but eliminates the inherent disadvantages of current two-stroke engines.
- The engine has the same three moving parts as a conventional two-stroke engine (crank, gudgeon and piston) and remains simple in its design. This means it has a low cost to manufacture and is simple to maintain.
- The engine is modular by design. Multi-cylinder engines are simply a collection of single cylinder engines bolted together with a common crankshaft. This feature provides flexibility and a lower cost manufacture.
- The delayed opening of the exhaust port on the power stroke provides a cleaner more complete burn of the fuel. This means the engine has lower exhaust and noise emissions and more engine torque than conventional two-stroke engines. This advantage extends to the compression stroke, where the trapped volume is a higher percentage of the swept volume. Current loop scavenge engines trap about 50% whereas with porting on all four walls this engine should trap around 80%.
- The closed loop engine oiling system that replaces the conventional two-stroke total loss system, provides for significant increase in the durability of components, reduced hydrocarbon consumption (and no blue smoke) and increased fuel flexibility.
- The basic design of the engine lends itself to other manufacturing techniques, for example, extrusion. This will yield lower manufacturing costs.
Technology Differentiation and Uniqueness
The engine is unique in a number of ways. These include:
- The engine oiling system is wholly contained within the piston itself. This provides the closed loop system.
- The cylinder and piston used in this engine are square. This provides for increased flexibility of design and a lower cost of manufacture.
- The base design lends itself to other manufacturing techniques and materials.