When you write about a technology enough you sometimes forget what people who casually follow the science know and don't know. Recently, while getting some dental work done (at my age you can always find something that need work) I got into a short conversation with the dentist.
We were joking that the nitrous oxide he uses is the same gas we're trying to get rid of from diesel emissions. Of course the chemical composition may be a little different, but the name's the same. That's when the dentist asked if diesel engines would even still be viable these days.
That's an interesting question to me, since for those of us in ag diesel is the ONLY way to go. But for the casual observer, the diesel engine has a bad reputation.
That got me thinking about how diesel engines have changed, and how they will change even more in the future. The advent of the common rail design in diesel engines is perhaps the biggest infrastructure change in the system.
The common rail idea first appeared as far back as the 1940s in locomotive engines and even in submarine engines as early as 1916. Today's common rail designs, which first started appearing in the mid-1990s, offered the benefits of electronics too.
This approach provides fuel at a constant pressure along a common "rail" which allows the injecting system to tap that fuel flow at any time during a combustion cycle. At first engineers stuck with the single combustion even during a compression, but these days a single compression cycle could have four or five injection events into the cylinder head. Manufacturers don't talk much about that, the number of combustion events in a cycle is considered proprietary.
A common rail design paired with computer-controlled injectors created this approach. Pushing fuel into the cylinder during different parts of the compression cycle can help with noise, emissions and fuel efficiency. Just that change, which is also an important part of the clean diesel tech that's in a lot of European cars, has significantly enhanced these engines.
Diesels, which have always been able to run a variety of fuels, could be the engine of choice for all cars and trucks too. Trouble is, clean air rules in the U.S. are different than in Europe. But engines are catching up. Those Interim Tier 4 engines you'll be seeing later this year on some new-model equipment will be clean burners. Chalk it up to the common rail system (and a big filter and some exhaust gas recirculation) as a big innovation that will keep diesels burning cleanly for years to come.
As for my dentist? I was too numb to talk about the benefits of common rail design, but I think he heard my enthusiasm in our discussion about the benefits of new clean diesel technology. These machines get more miles per gallon for consumers using a fuel with a better greenhouse gas profile, and these engines should be part of our more fuel-efficient future.