1. What Will The Ideal Hydrogen ICE Look Like?
Hydrogen is potentially a CO2 free fuel and as such it represents our best option for the future.
So just what does the ideal Internal combustion engine designed, specifically for hydrogen look like???
Lets take a step back.
What Will The Ideal Hydrogen ICE Look Like?
Paul McLachlan
Pivotal Engineering Ltd

2. What is an Internal Combustion Engine
And what does it do? ?

3. I am Paul McLachlan, I am the designer of the Pivotal engine and a director of Pivotal Engineering Ltd. in Christchurch New Zealand.
We have a common interest, to find the best way to convert the energy from hydrogen combustion into mechanical torque, for stationary power and for transportation.

4. High power density? 100 Hp 100 Hp
Actually what we use this power for - makes a difference.
For stationary power we need high thermal efficiency and size and weight, doesn’t usually matter. But for transportation we do not want to carry around any extra mass. 
The engine designed specifically to utilize hydrogen combustion for transportation, must deliver high thermal efficiency and exceptional power for its size and weight.
In fact ‘high power density’ must be designed into every corner of the vehicle. 
Every challenge that we face in using hydrogen for transportation relates back to power density. So it is fortunate indeed that hydrogen offers even higher thermal efficiency and power density than gasoline.
High power density?
100 Hp
100 Hp

5. What is an Internal Combustion Engine ?
So back to the Question – What is an ICE?
(click)
Well it is simply a device. It converts the energy of combustion into mechanical torque or power.
Ask engineers - to run an engine on hydrogen and they will set out to overcome the difficulties that they encounter in the conversion.
However, if asked – to design the best possible hydrogen engine, they would study the characteristics of hydrogen combustion and design a device to meet those demands. The outcome would be different.
What is an Internal Combustion Engine ?
Engine
Fuel
Torque

6. Where do we start ? First establish the criteria
 The design of an ICE is dictated by the characteristics of the fuel it will burn, and we are still, trying to adapt gasoline and diesel engines to operate on hydrogen?
It’s not that the likes of BMW or FORD don’t have very capable and imaginative engineers, of course they do.
But back when these projects started, there wasn’t the urgency that we now face. There wasn’t the need to change the fuel that the world drives on.
The objective then, was to run an engine on hydrogen. So the engineers set out to overcome all the difficulties they encountered as they learnt about hydrogen combustion.
As a result we now have a wealth of knowledge built up from such projects all over the world.
Where do we start ?
First establish the criteria
then design a new engine
that has all the required features

7. A very different fuel requires a very different device
Now we need, the best possible device to convert the energy of hydrogen combustion into mechanical power.   
We need a new device that addresses the specific characteristics of hydrogen combustion.
Hydrogen is not like gasoline or diesel – It is easily ignited, burns very fast and takes up much more space in the combustion chamber, as well as in storage.
These characteristics dictate every aspect in the design of the engine and the vehicle. Lets look at some of these characteristics.
A very different fuel requires a very different device

8. Hydrogen Combustion Characteristics
Hydrogen Combustion Characteristics
It’s a bulky fuel – so it needs to be injected into the combustion chamber after it has been filled with air.
The need for direct injection is well recognized and the complex task of developing ‘long life’ hydrogen injectors is well underway.
Low volumetric power density
Low ignition energy requirement
High flame speed at stoichiometric ratios
High auto ignition temperature
Short quenching distance
High diffusivity

9. Hydrogen Combustion Characteristics
It’s easily ignited – and this is good, but also, it presents a very demanding challenge, as pre-ignition will damage the engine and must be avoided.
To control the timing of combustion, the chamber must be kept free of any contamination and hot spots that could cause the fuel to ignite prematurely.
There must be no protruding sharp edges in the head or the piston crown and low temperature spark plugs must be used.
The surfaces of the head and piston must be maintained at a uniform temperature. Not too hot, not too cold. 
A thermally smooth combustion chamber surface is absolutely essential in the ideal hydrogen engine. 
This means that the exhaust poppet valve that has been developed over years to cope with extreme temperatures –
Has no place in a hydrogen engine.
Hydrogen Combustion Characteristics
Low volumetric power density
Low ignition energy requirement
High flame speed at stoichiometric ratios
High auto ignition temperature
Short quenching distance
High diffusivity

10. High Flame-front Speed
It’s fast burning –(10 times faster than gasoline) perfect for high thermal efficiency, as it pushes more of the pressure over to the working side of TDC, so more of the pressure is applied to the crankshaft when it counts
The reason that we do not get the full benefit of this characteristic on a converted gasoline automotive engine is because the fast burn advantage only comes with hydrogen/air ratios near to stoichiometric and rich hydrogen ratios are more prone to pre-ignite.

11. Hydrogen Combustion Characteristics
Hydrogen Combustion Characteristics
Another positive characteristic of hydrogen is the high octane rating that allows high compression ratios to be employed, further improving the thermal efficiency of the hydrogen ICE.
The ideal hydrogen internal combustion engine will deliver thermal efficiency to more than 45% compared to about 25-28% for a gasoline engine.
What it comes down to - is having the right tool for the job.
Low volumetric power density
Low ignition energy requirement
High flame speed at stoichiometric ratios
High auto ignition temperature
Short quenching distance
High diffusivity

12. Criteria for H2 engine Full thermal control High power density
Thermal control / power density / thermal efficiency -
So how do you incorporate all of these demands in the design of a simple internal combustion engine?
Where do you start?
With an obsolete device, optimized to meet the demands of gasoline or diesel?
Or - with fresh thinking and innovation to create a device that meets our needs in a hydrogen economy.
Full thermal control
High power density
High thermal efficiency
Low parasitic losses
Crankcase flushing
Longevity
Low Cost
Dual fuel capability

13. This engine has the potential to power our vehicles long into the future.
It is a simple, low cost device with few moving parts, therefore extremely low in parasitic friction. 
The piston is fully controlled by the pivot bearings. It drives the crankshaft via the connecting rod with a direct load path.
No need to lubricate the piston, only the compression seals need lubrication. The piston is internally water-cooled with access via the pivot shaft, circulating water out to the piston crown and back to exit at the other side.
With both the piston and head surfaces independently temperature controlled, a thermally smooth combustion chamber is achieved. 
By utilizing the swept area under the piston for air induction we ensure that the crankcase is continually purged of hydrogen.

14. The Water Cooled Pivotal Piston
The water-cooled Pivotal piston is the very core of the Pivotal engine technology. Without this development we could not meet the requirements for a viable, high power density hydrogen engine.
From this exploded view you can see how the piston, the pivot shaft, arc seals and the skirt make up the piston assembly.
The arc seals slide in to meet at the centre and the skirt is attached at the bottom and floats free at the top to seal off the exhaust port at TDC.
There is a piston circulating in the room so I hope it gets around to everybody.

15. Moving Mass takes Energy
To move mass – energy must be expended
Clearly the objective is - to reduce mass.
It is, however, important to understand that this is not an exercise of merely trimming weight from each component in a vehicle.
It demands a total re-think on what a vehicle is.
More Mass
More Energy
More Fuel
More Emissions

16. Or do we take less car with us?
When you think about it, we have consumed most of our gasoline just moving our car from one parking place to another.
When the primary objective is simply to move people and cargo in safety and comfort.
Do we use our car less?
Or do we take less car with us?

17. An Automotive Comparison
When compared to a conventional gasoline engine the Pivotal engine is half the size and less than half the weight for the same power.
We expect an even greater advantage with hydrogen, as the Pivotal engine will be able to operate at a Stoichiometric fuel ratio.
Toyota V6
Pivotal Opp 4
Capacity (cc /CI)
3000 / 183
2000 /122
Power (hp)
220
Weight (lb)
380
160
Box Size (cu.ft) 12 6

18. Compact Car with 220 HP Pivotal Engine
Here we have the pivotal engine scaled into a compact car. This indicates how the mass of the power train affects the mass of other major components in the vehicle.
A light and compact engine leads to a lighter chassis, lighter engine sub-frame, suspension, wheels, brakes and tyres.
The Pivotal engine will enable us to significantly reduce mass while retaining utility.
The engine is the orange item near the rear wheel

19. Pivotal Engineering has built up considerable expertise over twelve years of continuous development.
This 400 cc engine ran to 11,000rpm and drove the motorcycle to 100mph proving the concept.
However we did not have internal water-cooling in the piston at this stage so piston over-heating was a limiting factor.
The 400cc Motorcycle
400 cc
Twin chamber
11000 RPM
100 MPH

20. One Litre Twin Chamber Engine
We selected a 500cc module for the development program and this one litre twin is our first engine with successful internal water-cooling of the piston.
This enabled us to conduct sustained high load testing to improve performance and durability.
One Litre Twin Chamber Engine
Water-cooled piston
1000cc
twin chamber
100 hp
6200 rpm

21. We fitted our Pivotal engine technology to the crankcase of a Rotax jetski engine.
The Orbital air assisted DI fuel system enabled us to begin experimenting with direct fuel injection.
Pivotal DI Engine
1000 cc
Twin Chamber
Orbital direct injection

22. Pivotal Light Sport Plane Engine
With high power density as our prime advantage, we designed this engine for the Light Sport Plane and Ultralight markets.
It was displayed at the Oshkosh Air Venture in 2003.
This engine has become our core test unit since, and forms the basis of our generator engine product.
Pivotal Light Sport Plane Engine
Power 120 hp.
Weight 120 lb.
TBO 1000 hours.
BSFC ½ lb.per hp/hr

23. This is the 30 kW portable, ‘stand alone’ generator that we are currently optimizing for direct injected JP8 fuel.
This is a cooperative venture with CE Niehoff of Illinois.
Our high power density engine combined with their high power density permanent magnet technology delivers an extremely compact generator unit.
With this engine in series production it will provide us with a supply of development engines to support a program to optimize the pivotal engine for hydrogen fuel.
30 KW Stand Alone Genset
30 KW
250 Kg

24. 2 Litre Opposed Four Engine
This opposed four configuration delivers very high power density as it is inherently balanced with a light crankshaft and compact crankcase. It is a very smooth, low friction engine with low mechanical noise.
It is our first 2.1 litre engine. It delivers 6,000 rpm weighing only 150 lb.
That is 1.5hp for every lb. of engine weight.   
So the Pivotal hydrogen engine will weigh about 30% of the weight of a gasoline engine converted to hydrogen.

25. We are confident that it can be done.
We can develop hydrogen cars that have the performance, range and the level of utility that we expect.
There is no insurmountable technology gap.
The best product that we could make with the hybrid technologies that we have now and a Pivotal engine would be good enough.
If the vehicle was a lightweight PHEV with a battery range of 80km and hydrogen fuel range of 400km and the hydrogen was topped up along with the battery at home. Assuming that the price was reasonable – they would sell.
The Pivotal engine has the potential to power our vehicles long into the future

26. If the investment into the hydrogen highway is going to be the catalyst to a growing network of hydrogen outlets it will require that the public buy these vehicles in large numbers.
It is not such a daunting task and the Pivotal engine presents an exciting commercial opportunity.
The outlook for fuelling our transportation with hydrogen is more than good. We can do it now and there are people in this room who can have a major input to make this happen.
I look forward to talking with you.
The water-cooled Pivotal piston is fundamental to the hydrogen economy.