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Steam Injection into IC Engines to Suppress Knock - my University Thesis Discovery in 1976

Somehow, about 45 years ago, I was accepted into University College London (UCL) to study Mechanical Engineering. My A Levels were Maths, Physics and Chemistry, because I was less worse at these subjects than I would have been had I chosen others. Put them into a subject mincer, sprinkle on single-minded paternal advice (my dad was a great engineer), and out popped Mech Eng as my passport to a career.

It wasn't long before I realised that I was never going to be a career engineer, but I persevered and scraped into my final year where I encountered two novel features of the UCL course. Firstly that I could choose to add subjects that had little to do with engineering - so I studied stuff like Law, Psychology and the History of Technology. And secondly I had to do a dissertation on a project proposed by one of my professors. The project I chose was titled "Steam injection into an internal combustion (IC) engine to suppress the onset of pre-detonation with unleaded fuel".

I won't go into the science behind this a) because you'll become as bored as I was, and b) I really wasn't a good engineer and will struggle to explain it properly, but here nonetheless is quick and no doubt misleading or plainly erroneous explanation of what we (me and my project partner Pete) were trying to do:

Pre-detonation, otherwise known as 'knock' or 'pinking', can occur in petrol engines and manifests itself as a loud clattering noise. If it isn't prevented, the piston, cylinder head and valves can be damaged. Which isn't good. Basically the fuel/air mix that's being compressed by the piston in the cylinder head can pre-ignite before the spark makes it go bang. This happens because the fuel/air mix gets too hot, especially in more efficient high-compression engines. So in order to prevent the onset of knock, the industry used to add Tetra Ethyl Lead (TEL) to petrol (ie Leaded Fuel). Lead is not a good thing to pump into the atmosphere, so better ways needed to be found to prevent knock.

Our head of faculty, Professor Billett, dredged up from somewhere the notion that by adding water in the form of steam to the fuel/air mixture on its way into engine, it might in some way cool the gas and thereby prevent knock. Our job was to test this theory.

In the basement of the engineering faculty were several laboratories. And in one of these was a car engine. Pete and I designed a device that would enable the very hot exhaust gases it produced to heat water which we could inject as steam in controllable amounts into the carburettor. This mixed the steam with a spray of fuel together with the right amount of air before it was sucked into the engine to be compressed and blown up dozens of times a second. We could increase the amount of fuel going into the engine (just as your foot does when it presses the accelerator pedal) while at the same time increasing the load on the engine (as your car experiences going uphill and when it accelerates), and varying the amount of added water.

Then we would take readings of what happens to the power and efficiency of the engine when we added increasing proportions of water to the fuel mix while listening for the onset of knock. What we had been told to expect was the more water we added, the cooler we would make the explosive gas, the less knock would occur. This proved to be the case, but we could never completely get rid of knock, except.....

When we plotted our data on a graph, there was a huge spike in our results when we added the tiniest of amounts of water. Adding a little bit more returned the results to modest effects on the onset of knock which would then start to become more beneficial, as predicted, when we further increased the amount of water. In fact right up to an incredible 50/50 water to fuel ratio.

Pete and I presented our results to our Prof and a panel of senior lecturers. We showed this massive spike in our graphs but all the experts declared that what we had detected was data error since we were measuring such tiny amounts that our instruments would have struggled to give accurate readings. Pete and I were upset by this slur on our ability to read instruments, but we were both rubbish engineers - and keen to graduate - so we didn't argue.

And that was that. Or so I thought, until about 10 years later when I was chatting to an engineer from Volvo, where I worked in their marketing department. He mentioned that Volvo had been working with the Israeli military, of all people, on the use of steam injection into petrol engines to prevent knock! And what they had discovered was that there was a catalytic effect on the fuel that occurred when trace amounts of water is added. There was a chemical change happening to the fuel, not a physical one, which coincidentally suppressed knock! Pete and I really had discovered something that we, and our genius lecturers, had been unable to explain or accept.

Since then of course, the car industry has found other ways of enabling cars to run on unleaded fuel, so our discovery, to the best of my knowledge, was never deployed or developed into anything useful. But it does make a good story about what might have been, had I had the nerve to stand up to my superiors. But then again, getting a degree was more important than being proved right - I think.


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