ADIABATIC COMBUSTION IN THE VLB IC ENGINE

Compress any combustible material hard enough, and it will ignite. Contain the reaction, and the combustion will generate more pressure. If the pressure can overcome the restraining forces, the material will rapidly expand, which is to say, it will explode. In the explosive industry's terms, the violence (as in the force / time factor) of the explosion can be described as what is generally called a detonation (which is very fast) down to a propulsion (which can be a relatively slow process).

Any suitable fuel (say, gasoline) if mixed with a suitable reactant (say, oxygen - as contained in air) and then subjected to increasing pressure (as in an IC engine cylinder) will have its temperature raised. If that temperature is allowed to reach the "flash-point" of the mixture, it will ignite. It is the flash-point temperature which instigates the process in an IC engine, not an "absolute" pressure. Temperature and pressure are only directly related if the element of time is ignored. Feed very cold (mountain top) air, mixed with fuel, into a cylinder and rapidly compress it, and the actual pressure at which adiabatic reaction takes places will be greater than with (otherwise proportional) warm (sea-level) air.

If the combustible material is a single substance (say hydrogen) and the pressure of the whole is uniform, the ignition process will be uniform with respect to the generated force and reaction-duration product. Such a monatomic reaction will result in nothing which could be even remotely described as a "flame-front". In fact, even fuel mixtures which rely upon a component which has a lower flash-point to effect an additional pressure / temperature rise to instigate a second component reaction, and so on, will not produce a "flame-front", if the distribution of the mixture is uniform. Such a mixture will, however, produce a slower over-all reaction.

Note: Compound fuels may contain, and / or may have added, relatively small amounts of low flash-point fuels. Such mixtures, in the required ratios, can render many "unlikely" substances suitable as IC engine fuels.

If, as in the case of the conventional diesel engine, the air temperature is raised to, or beyond, the fuel's flash-point prior to injection, the fuel will be ignited as it enters the chamber. Clearly, with such an arrangement, a "flame-front" will be observable. The moving flame-front is manifested by the unburned fuel's progress through the surrounding atmosphere in search (as it were) of oxygen with which to react.

In the case of the VLB engine, the fuel is injected prior to a flash-point pressure being reached, and no combustion is initiated. Then, after the injection is completed, enough of the fuel / air is subjected to an electric arc so that it is ignited, this reaction then giving rise to further pressure, such that the unburned fuel is subjected to adiabatic conditions, causing the whole of the remaining fuel to be consumed spontaneously and during the cycle's low entropy period - thus returning a higher energy yield than any other type of engine.

With this reaction, the arc will generate what could be called a "flame-front", which will move away from the source only as far as is required to provide the additional pressure. (However, no additional flame-fronts, as such, will be generated. I say "as such" because the secondary effects of turbulence can promote an uneven reaction which could – but only by stretching the meaning to its extreme – be labelled "fronts"). In addition, the "flame-front" generated by the arc will be of a very different nature to that which may be observed in a conventional diesel chamber. That is to say, if (as is the case in the VLB engine) the fuel which is ignited by the spark or flame already has more than enough available oxygen, a slow motion replay of the effect will more closely resemble a relatively small flash followed by an instantaneous 'full chamber' flash, rather than a moving front.

Three 'components' are required to accommodate a reasonably wide range of fuels. These are: Variable ignition timing, variable exhaust timing, and the time (as a percentage of the cycle) to make these variables practical. The range can be further extended by providing for a variable compression ratio. Additional variables are also built into the VLB design, but these concern performance rather than the fundamental adiabatic process.

From all this, you may conclude that an engine which is to operate using arc initiated adiabatic combustion, particularly if it is to operate over wide temperature and fuel type ranges, makes demands upon its designer which are far wider, and less tolerant, than any conventional configuration. And you would be perfectly correct. But examine the VLB technology 'as a whole', and you will discover how this 'range' is catered for.

In order for a conventional diesel engine to cope with a wide range of fuels, it would need a high enough compression ratio to burn the fuel which has the highest flash-point. This would impose sufficient extra load upon such an engine, that it would be an unacceptable waste of power when burning low flash-point fuels.

A great deal of the load which is borne by a conventional diesel engine is absorbed (wasted) by the compression process. The "chain reaction" system employed by the VLB engine avoids much of this waste, whilst allowing for an extended fuel range, which includes fuels such as methane (which is abundant and not at all suitable for diesel technology).

Much good work has been done, and much more talked of, regarding the improvement to the dispersion of fuel injected into conventional diesel engines. However, I would challenge anyone to present a full and sound argument to show how the process of injecting fuel into a chamber of air already raised to the fuel's flash-point before TDC, could improve upon the VLB's process of raising premixed air / fuel to a pre-adiabatic pressure by means of cylinder compression, and then on to its flash-point (at, or even post, TDC) by external ignition.

There is another type of adiabatic engine: An engine which compresses premixed air and fuel, and then raises it to its flash-point by compression alone. Such an engine can be made to run. Indeed, as a small boy in the 1940s, I had such an engine in a model aeroplane. However, this configuration can only be effectively harnessed to a workload over a very small range of engine speeds. Furthermore, such an engine is extremely critical to sudden load changes and will readily stall (although a constantly variable gearing system might overcome some of these difficulties). In addition, with any practical fuel, the operational engine speed would be far too low for road vehicles.

Such an engine can burn the fuel properly, with a very lean mix, and produce only insignificant amounts of pollution. It can be a very simple and, properly engineered, should be highly reliable. So it is a pity that it has so few practical applications. Let me make it clear that the VLB engine is not such a design, does not suffer any of the above limitations, and that any similarity between the two technologies is entirely superficial.

Clearly this document does not answer all possible questions which might reasonably be raised with respect to the VLB adiabatic technology - because not all of the technology can be publicly revealed at this time.

John Allen