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The Pivotal engine has features that present new options for internal combustion engine design.

The advantages of the water-cooled pivotal piston are particularly beneficial when applied in a two/stroke engine. The high level of thermal control of the water-cooled piston and thermally smooth head surface the Pivotal engine is very suited to running on a wide range of fuels such as Diesel CNG LPG and JP5. The advantages of the water-cooled piston to the development of an ideal hydrogen fuel IC engine is clear. In a hydrogen IC engine it is important to avoid peak and localized high temperatures which cause pre-ignition or high NOx creating conditions.

What do these new options mean to engine designers and how will this technology benefit the manufacturer and the end user?

By breaking through the inherent barriers against the use of two-stroke engines the pivotal engine technology brings low cost and high power density to mobility applications. In recent years the automotive industry invested heavily in two/stroke engine development in a effort to capture the benefits of higher power density and lower manufacturing cost. The reduction of engine size and weight brings many benefits to total vehicle efficiency. A compact and light weight power unit is an advantage in all mobility/transport engine applications. The flow on effect of a high power density engine presents weight savings extending through the vehicle to the engine sub-frame, the suspension, brakes and wheels. Less room dedicated to the engine bay means more room for the passengers and cargo or a smaller, lighter vehicle.

A reduction in total vehicle mass is the first priority toward achieving fuel efficiency.

The size and weight of the Pivotal engine make it an ideal power unit for automotive use including hybrid systems where the saving of space and weight is particularly important. The Pivotal engine offers an increase in power of up to 100% per kg. or half of the size and weight of a modern four/stroke automotive engine. This compact engine creates flexibility for vehicle designers to locate the power unit closer to the driving wheels to improve weight distribution.

There is increasing pressure on manufacturers to lower prices and reduce the time it takes to bring products to the market. A smaller number of components reduces both the cost of manufacture and the lead time required to develop a new product. The Pivotal engine is developed into complete single chamber modules which are then configured into families of engine products. The fully modular assembly further reducing the cost of manufacture. This also reduces engine component inventory and the time required to bring a new engine configuration to the market place. The same components can be placed together to create the engine for a small car with a one litre twin chamber engine, to a four litre eight chamber high performance sports car. With perhaps minor changes, the same components can equally well be used in a motorcycle or outboard engine.

Conventional two/stroke engines tend to be limited in size as their shortcomings become more evident when the piston/cylinder size is increased as it becomes increasingly difficult to cool the larger piston. The rate at which heat can be dissipated from the crown of the piston, via the piston skirt, into the cylinder is a limiting factor for any engine, two/stroke or four/stroke. At high load a piston gains heat faster than it can be dissipated. Consequently maintaining high load for more than a short period will cause a high performance engine to fail. Direct water cooling of the piston can provide piston cooling to the degree required. This is especially useful in applications where it is desirable to run the engine at full power for a long duration, such as with light aircraft or marine applications. The temperature of the water-cooled pivotal piston is directly and independently controlled so it is possible to maintain uniform combustion chamber surface temperatures to provide an optimum combustion environment.

Jet ski, outboard boat engine and snow mobile manufacturers are under pressure to greatly reduce the amount of oil consumed and emitted. For some years now there has been rising concern about the oil contaminating water ways from two/stroke outboard boat motors. The conventional two/stroke engine requires a large amount of oil to lubricate the sliding piston in the cylinder, this presents a very difficult task to limit the amount of oil escaping the engine with the exhaust gas. The low demand for lubrication as a result of restraining the piston at the pivot shaft bearings reduces oil consumption to 10% of a conventional two/stroke engine greatly reducing to cleaner exhaust emissions.

The Pivotal engine can be used in stationary engine applications such as power/heat co-generation where low mechanical noise is required. As the piston is restrained by bearings there is no sound caused by the piston rocking against the cylinder wall. Other applications where high power density is important include equipment which must be transported to site such as mobile fire pumps and emergency generators. This equipment needs to be easy to carry with the ability to sustain high loads for prolonged periods.

The Pivotal engine was first conceived to overcome the durability and reliability difficulties of a Grande Prix motorcycle engine and is more than suited for use in both commuter scooters and high performance sports motorcycles.

The Hydrogen IC engine Potential.

High power density and low cost could make the internal combustion engine the common power unit for mobility in a hydrogen economy. The ideal hydrogen IC engine may have a lower thermal efficiency than a fuel cell yet still perform efficiently in a vehicle due to its high power density and the 'flow on' of weight savings which extend throughout the vehicle.

The development of water-cooled pivotal piston technology has matured at a time when the necessity for a suitable hydrogen fuel IC engine is increasingly evident. The prospect of the hydrogen age presents an opportunity to take a fresh look at new IC engine design to maximize the characteristics of hydrogen combustion.

To deliver high power density a near stoichiometric air/hydrogen ratio must be used and the hydrogen must be injected directly into the combustion chamber. This will demand that all combustion chamber surfaces are thermally controlled and uniform. With these considerations paramount an internally water-cooled piston in a water-cooled two/stroke engine could be the most suitable engine for hydrogen fuel.

(Author Paul A. McLachlan)

Paper from the Hydrogen Conference Washington DC. 30/3/05
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