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.
"DISCUSSION ON THE POTENTIAL OF THE WATER-COOLED PIVOTAL
PISTON H2ICE TO EXTEND POWER DENSITY AND TOTAL VEHICLE EFFICIENCY."
(Author Paul A. McLachlan)
Paper from the Hydrogen Conference Washington DC. 30/3/05
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