Milestones in Diesel Technology

There have been significant advancements in technology since the late 1800s when Rudolf Diesel invented the engine bearing his name. Here is an overview of the diesel engine's evolution.
By Ron Kotrba | July 15, 2009
The world would be a very different place without the diesel engine, the workhorse of the modern era. Imagine how much more expensive goods would be if, rather than transporting products all over the world in diesel-powered 18-wheelers, locomotives and marine vessels, we relied on less efficient gasoline-powered vehicles for the same services.

According to Navistar Engine Group, trains in the early 1900s hauling heavy loads from New York to San Francisco could take more than six months to complete the journey. Once the U.S. intercontinental railroad system began using diesel engines in the mid 1920s though, the trip was cut to about 10 days. Transportation is just one of many industries relying on diesel power today. Over the past century, construction, power generation and agriculture have all come to depend on the durable diesel engine.

Rudolf Diesel patented his design, referred to as a Carnot heat engine named after Nicholas Leonard Sadi Carnot, the French physicist and thermodynamics pioneer, in February 1893. The patent was titled, "Theory and Construction of a Rational Heat-engine to Replace the Steam Engine and Combustion Engines Known Today." Diesel spent the rest of the decade perfecting his design, building prototypes and licensing the engine to manufacturers. Twenty years after his patent was issued, Diesel died a mysterious death, falling overboard a steamship crossing the English Channel.

By 1905, turbochargers were beginning to be manufactured for diesel engines to boost power output. A turbocharger pre-compresses the air to create more air mass for combustion, therefore delivering more power. Turbo intercoolers also debuted around this time. They worked to cool down the compressed air from the turbocharger, like a heat exchanger, and increase density of the air prior to combustion. Early diesel engines were large and bulky, predominantly used as stationary engines for manufacturing.

The German engineer and inventor, Prosper L'Orange, made his mark on diesel technology advancement with German Patent DRP No. 230517-a huge milestone for diesel technology. In that patent was the design for a pre-combustion chamber in the diesel engine, which allowed for partial combustion prior to the introduction to the cylinder, and additional turbulence for a more complete mixing of the fuel and air. L'Orange gained his patent on March 14, 1909. According to Daimler AG, this was an important milestone in diesel technology advancement because it "made possible the development of the diesel engine from being a stationary source of power to one with mobile applications."

L'Orange worked at Benz & Cie. in Mannheim, Germany, from 1908 to 1922. On Daimler's Web site, it states: "The prechamber principal played a key role in the evolution of the diesel engine into a compact, high-speed vehicle drive system. A semispherical chamber was introduced between the injection nozzle and the cylindrical combustion chamber to facilitate rapid combustion at high temperatures. With the prechamber diesel unit it was possible to achieve much higher engine speeds and thus high outputs than with older versions of the compression-ignition engine. Other groundbreaking inventions by L'Orange include the funnel prechamber (1919), the pintle-type injection nozzle (1919) and the variable injection pump (1921)-all of them landmarks along the route taken by the compression-ignition engine towards its application in the automobile and providing at the same time a basis for the first vehicle diesel engines." In 1933, Prosper's son Rudolf founded L'Orange GmbH, now a major world supplier of fuel pumps, injector systems and valves.

Rise of the Engine Manufacturers
In 2008, Navistar Engine Group held its 75th anniversary event at its Huntsville Big Bore Plant in Alabama. Group president Jack Allen said, "It's humbling to consider the efforts so many people put into the development and manufacture of our diesel technology over the past 75 years; all the ideas, the risks and the breakthroughs that generations of workers offered up. For those of you who may not be familiar with our history, Navistar is the direct business descendent of International Harvester. We've been designing, engineering and manufacturing engines, vehicles and equipment for more than 100 years."

Capitalizing on the early conceptual success of diesel design, original equipment manufacturers such as MAN, Navistar, Cummins, Detroit Diesel, Caterpillar and many more, began to form; which brought an onset of OEM suppliers such as L'Orange, Bosch and others. International Harvester first began early experimentation with diesel engine design between 1916 and 1919. By 1929, they were developing injection pumps and a year later pre-combustion chamber work ensued.

Clessie Lyle Cummins founded Cummins Engine Co. in 1919, and after a decade of innovations and upsets, "a stroke of marketing hubris by Clessie Cummins helped save the company," Cummins states. "Cummins mounted a diesel engine in a used Packard limousine and on Christmas Day in 1929 took W.G. Irwin (an investor who helped finance Cummins' start) for a ride in America's first diesel-powered automobile."

Caterpillar Tractor Co. emerged in 1925 resulting from a merger between Holt Manufacturing Co. and C.L. Best Gas Traction Co. After years of attempting to employ other companies' diesel engines in Caterpillar tractors, none of which were thought to be a satisfactory pairing, the company began preliminary engine development in 1930. Later that year, Caterpillar tested its first pre-combustion chamber engine. According to Caterpillar, "A pre-combustion chamber was used because at this time there was no diesel fuel per se.

What was available was a collection of various distillates that varied widely in composition and quality. Any engine would have to be able to burn whatever fuel was available locally.

Additionally…any fuel system would have to be nonadjustable or else the company would face a litany of complaints as customers tried to 'improve' engine performance by doing their own fuel system adjustments, a practice that continues today."

Originally designed for tractors, Caterpillar states its early diesel engines had an advantage over other designs. Oil bath air cleaners and enclosed push rods were considered unnecessary luxuries on other designs but came standard on Caterpillars.

As diesels were gaining traction in the early 1930s and becoming popular workhorses globally, widespread catastrophic breakdowns began to occur. Engines began dying after only a few hundred hours in operation. Piston rings were getting stuck in their grooves, resulting in a loss of pressure and power.

As Caterpillar puts it, engine makers were blaming oil companies and vice versa. "It took several years before everyone realized that a new refining process introduced in the early 1930s had removed naturally occurring detergents from the crude oil. With the detergents gone, there was nothing to inhibit the formation of combustion byproducts in the ring grooves, which eventually led to the ring becoming stuck in the groove and not sealing." Thus, the dawn of engine oil additives arrived. Shell Oil identified a chemical detergent and began including as an ingredient in its oil during production. And Caterpillar created the first standards for diesel engine lubricating oil as a result of these experiences.

Fuel injection systems went through an evolution of their own from the beginning, with Diesel's original system using air from large, bulky compressors requiring lots of power to run. Eventually, spring-loaded valves-mechanical injection-took over. According to The Bosch Group, which has been a pioneer in injection technology, diesel injection pumps went into production in late 1927. Bosch states, "At first the pumps were so heavy that they could only be fitted into buses or trucks. But in 1936, Bosch brought out the first diesel injection system for cars."

Mechanical "indirect" fuel injection, which made use of variations of L'Orange's original pre-combustion chamber invention, was common diesel technology all the way through the 1980s. "There was certainly a big period of time before the idea of a direct injection diesel really sank in with a lot of people," says Allen Schaeffer, executive director of the Diesel Technology Forum. "Different engine designs had indirect injection, which were a favorite to some but tended to crank out a little more smoke than their successors. It was a progression from a fairly basic engine design that pretty much stood still, not terribly changed much from early 1900s through the 1960s, when diesel became the predominant source of power for the commercial trucking industry." Schaeffer says in the 1980s, when the onset of emissions regulations by U.S. EPA loomed, direct injection was already becoming increasingly important to better control the environment inside the cylinders.

Modern Era and Beyond
Emissions regulations of the past 20 years sparked a profound progression in diesel technology. EPA puts regulations into place, and engineers figure out how to meet them. EPA was on a long-term mission to obliterate soot (particulate matter), oxides of nitrogen and hydrocarbon emissions from diesels-all diesels, beginning with on-road trucks, to off-road construction and agriculture equipment, to locomotives and marine vessels. "Those regulations drove a lot of design changes and technology solutions, and have really driven just about everything else since then," Schaeffer tells Biodiesel Magazine. "The switch from mechanically controlled engines, meaning they had no computer measuring air or fuel, to the modern electronic controls we know today and have seen predominate the world since 1994-that's been a major change. The introduction of electronic controls was really a way to get better fuel economy and reduce emissions."

In 1994, Bosch made available its first electronic unit injector, and three years later the company introduced its high-pressure common rail injection system, now widely adopted.

According to Bosch, the Common Rail gives engine makers the flexibility to reduce exhaust emissions and lower engine noise. This is because with Common Rail, a combustion cycle can be more controlled with several pre-, main and post-injections, allowing the engine and the injection system to be effectively matched. Through electronic controls and with extreme precision, all the injection parameters-pressures, injection timing and duration, and other functions-can be highly managed. To stress the importance of how evolved diesel engines became in the early 1990s onward, Schaeffer says there's no real ability or point to upgrading engines made prior to 1994. "It's one more thing that should be replaced with a newer engine or scrapped," he says. "There's just not a lot that can be done to drive emissions down in those engines. It's like the difference between analog and digital."

Beginning in model year 2007, diesel trucks, buses and cars sold into the U.S. come equipped with diesel particulate filters, helping in the grand overall scheme to lower NOx and virtually eliminate soot. By 2010, all on-road diesels will be equipped with NOx scrubbers (either adsorbers or selective catalytic reduction systems depending on the vehicle size), eliminating smog-forming NOx compounds. Off road, locomotives and marine emissions reductions all follow suit.

With the elimination of all diesel emissions in sight, Schaeffer says there's a major chapter being closed in the progression of diesel technology. "The new chapter is one that first presumes the engines are very clean, opening up a whole new future looking at energy efficiency and, of course, CO2 control," he says. "Those who know a lot about diesels know it's always been the most energy efficient internal combustion engine out there, that it was founded on renewable fuels-we all know that. Diesel engines right now are about 42 to 45 percent thermally efficient, which is good. In the gas world they're only in the high 20s. There's a move to push diesel thermal efficiency to as high as 55 percent in the next decade onward."

Ron Kotrba is editor of Biodiesel Magazine. Reach him at (701) 738-4942 or
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