15 December 1995

in history

Rudolf Diesels place

When was the first diesel engine made and who invented it? Andy Collings takes a look at the history of the diesel engine

DIESEL engines dominate not only the agricultural industry but most other forms of transport where power and economy are a prime requirement.

And we owe it all to Rudolf Diesel. Born of German parents in Paris in 1858, the story of Diesels life and its ultimate tragic ending is a fascinating one.

Responsible in his early career for inventing such diverse apparatus as clear ice-making machines and an ammonia engine, it is the development of the Diesel engine for which his name is inexorably linked.

But first a background to the development of the internal combustion engine generally. Prompted by the recognition that the steam engines efficiency had little to offer the world in the long term – a mere 10% efficiency was all that could be achieved at best – the quest began to develop an internal combustion engine (steam power is an external combustion engine).

From 1825 onwards attempts were made to build gas-fuelled engines with the first patent taken out in 1860 in Paris by one Jean Lenoir. Not over successful, it burnt a 7:1 air/gas mixture with an "erratic electric ignition system".

The teaming up of engineers Nicolaus Otto and Eugen Langen to design and manufacture gas-fuelled engines formed the basis for the present Klockner-Humboldt-Deutz (KHD) company – the oldest manufacturer of internal combustion engines in the world.

Compression idea

And it was Otto who had the idea of compressing air and gas in a cylinder before ignition. The advantages of compression were twofold: Greater efficiency through the preheating of the mixture by compression and secondly, the compression acting as a cushion for the piston as it reaches the end of the stroke and reverses direction. Earlier, non-compression engines had literally knocked themselves to bits due to the violent directional changes of the piston.

Otto then developed the four-stroke engine – intake, compression, ignition and exhaust – a development which was met with derision by those who believed the system to be wasteful to the extreme. Even so, Otto persevered and 1876 saw the launch of the worlds first four-stroke engine – a single cylinder, flame ignited gas engine.

Soon recognised

Quieter, lighter and, for then, reasonably efficient, the design was soon recognised as a significant breakthrough. But a lucrative patent taken out by Otto prevented any exploitation by other manufacturers until it was discovered that a prior patent describing a four-stroke system had been filed in 1862 by a French engineer, Alphonse Beau de Rochas.

With a court case overthrowing Ottos patent in 1886, the gates were open for manufacturers such as Daimler and Benz to exploit the new engine design.

Enter Rudolf Diesel. Working for some years with high pressure gas (his ammonia engine and ice-making machines) led him to the conclusion that engine efficiency depended on high temperature and high pressure at the point of ignition. And then he set about designing an engine based on the high compression of air.

Calculations by Diesel revealed that by using a four-stroke system, and providing a cylinder pressure of about 3620psi, a theoretical efficiency of nearly 70% could be achieved. It is worth noting at this point that Diesel specified that fuel and air was not to be mixed before induction into the cylinder with the fuel only introduced at a set point in the pistons stroke.

Augsberg 1893 and work began on the production of a prototype. Diesel was 35 years old.

First attempt comprised a single cylinder engine having a bore and stroke of 15cm x 40cm. Ungainly by any standard, it stood some 3m tall with the crankshaft and connecting rods totally exposed. Overhead valve gear was operated from push rods riding on a cam driven off the crankshaft.

A major problem was to find material which could act as successful seals to contain the high pressures created.

First tests, with the engine rotated from an external source, created a pressure of nearly 500psi – a long way short of Diesels original aim. This was eventually rectified through a fresh design of piston head – the first one had too deep a combustion chamber.

August 10 proved to be an historic day – the day when Diesel first managed to explode fuel successfully in the cylinder. But even with such initial encouragement development was painfully slow as problems of cooling, sealing and unpredictable combustion were met and gradually overcome.

Biggest problems

One of the biggest problems was to get the fuel into the cylinder at the right time and in the correct amount. It was a problem which Diesel never entirely mastered – his engines used a separate compressor to power the fuel into the cylinder. The modern injection pump owes its development to Robert Bosch who introduced a pump/glow-plug system in 1927.

Deciding on what grade of fuel was also a detail which caused Diesel some sleepless nights. He tried all manner of petroleum grades – from thick viscous oil to much thinner grades.

After countless rebuilds, most an improvement on what had gone before, February 17, 1897 saw the first running of an engine with a 25cm diameter bore and a 40cm piston stroke. It developed 17.5hp and gave an impressive thermal efficiency of 26.2%.

Diesel was rich. Royalties from his engines poured in as the industrial giants fell over themselves for rights to manufacture his new engine.

An undisputed genius in the mechanical world, Diesel appeared to be sadly lacking when it came to finances. Bad investment, large scale spending and the expiry of patents depleted his funds to the extent he was soon badly in debt.

And so it was that in the early hours of September 29, 1913, while on the cross-channel ferry from Antwerp to Harwich, Rudolf Diesel disappeared overboard, his body being found some 11 days later.

Thus ended the life of the man who gave the world the most efficient and widely used engine ever invented – Rudolf Diesel.

Rudolf Diesels

engine cycle

Intake – air at atmospheric pressure is drawn into the cylinder.

Compression – air is compressed by the piston to 3620psi, raising its temperature to about 900C.

Ignition – As the piston passes top dead centre fuel is injected which ignites immediately causing a rapid expansion, driving the piston down.

Exhaust – the piston expels the spent gases as it sweeps up to the top of the cylinder once more.

&#8226 The expansion of the gases as the piston is driven downwards on its power stroke also has a cooling effect – the opposite to the heat generating compression stroke. Diesel theorised that at the end of the stroke, the pressure would have returned to atmospheric pressure with little or no loss of heat – and wasted energy – to the cylinder wall.