DAF Unveils Euro 6 Engines with Common Rail
“The PACCAR MX-13 engine is ultra clean”, says Ron Borsboom, member of the DAF Trucks N.V. Board of Management and responsible for Product Development. “In addition, we’ve gone to great lengths to obtain industry leading fuel efficiency, reliability and sustainability.”
Compared with the current Euro 5 standard, Euro 6 requires that nitrogen oxide (NOx) emissions must be reduced by a further 77%, while soot particle emissions must be cut by 66%. In concrete terms, this means that nitrogen oxide emissions have to be reduced from 2.0 to 0.46 grams/kWh, and soot particle emissions from 0.03 to as little as 0.01 grams/kWh. These are however not the only requirements: Euro 6 engines must meet these stringent requirements for a minimum of seven years or 700,000 km, in all operating conditions. In future, authorities will carry out random checks to ensure that vehicles are compliant with these standards, and new on-board diagnostics systems will warn the driver in the unlikely event that this is not the case.
A quarter of the Kenworth and Peterbilt trucks supplied in the United States since summer 2010 are equipped with the six cylinder 12.9-litre PACCAR MX engine with EPA10 specification. “This engine complies with current North American legislation, of which emission values come close to those set out in Euro 6″, explains Ron Borsboom. “We have therefore been able to build up vast experience of technologies we will now be applying in Europe for Euro 6, such as exhaust gas recirculation (EGR), a turbo with variable geometry and an active soot filter. We have further developed these technologies, focussing in particular on how we can best integrate them into European vehicle concepts. A good example is the higher position of the EGR cooler, which allowed us to place the turbo closer to the block, further reducing the overall size of the engine. This is an important factor when it comes to fitting the engine in our European cab-over-engine vehicle designs: it allows for a low cab floor to ensure ease of entry and maximum cab space. In addition, we will of course also be applying technologies to the Euro 6 PACCAR MX-13 engine that have recently been introduced as part of our ATe programme for Euro 5. An encapsulated exhaust manifold for even better turbo efficiency and optimised piston rings and cooling are just a few examples of these technologies.”
The PACCAR MX-13 engine is characterised by its combination of proven, state of the art technologies and a large number of technical innovations. “The block has been redesigned for even better stiffness and, like the cylinder head, it is made of strong compact graphite iron”, explains Borsboom. “With a view to ensuring maximum reliability and durability, as many functions as possible have been integrated. For example, plumbing has been cast into the cylinder block and head, and the two pump units that generate pressure in the common rail system have been integrated into the block, which means they can be actuated by the same camshaft that drives the valves. The fuel in the central pipe is supplied using smart dosing controls, to ensure optimum efficiency by only compressing the amount of fuel mixture that is really needed. This reduces hydraulic losses to a minimum.”
The common rail system of the new Euro 6 PACCAR MX-13 engine allows high injection pressures of up to 2,500 bar, and provides the opportunity to use pre- and post-injection, or a combination of both. This results in finer atomisation and many more possibilities to optimise combustion, ensuring the lowest possible emission and noise levels, and the lowest possible fuel consumption. “The highly advanced engine software and new sensors and actuators also play an important role in this respect, functioning even faster and more accurately to ensure that the best possible mixture of air, exhaust gases and fuel is injected at all times. This is also key in achieving maximum efficiency and low emissions”, says Borsboom.
The main advantage of using a turbo charger with variable geometry (VTG) is that the engine can rely continuously and across its entire rpm range, on the best turbo settings for maximum performance. “The variable geometry turbo was also required to optimise the effectiveness of exhaust gas recirculation, especially at low rpm”, explains Borsboom. “This technology allows us to carefully set the amount of exhaust gases diverted back into the engine, which also helps fuel efficiency. The application of an advanced turbo also has a positive effect on the MX Engine Brake, which can release more than 75% of its impressive 325 kW at low speeds (1.500 rpm) for maximum efficiency.”
In order to meet the stringent Euro 6 emission requirements, DAF is using a combination of exhaust gas after-treatment technologies, such as an SCR catalytic converter and an active soot filter. “In addition to achieving the right exhaust gas mixture, the aim is to create an optimum temperature in the filter to regenerate the collected soot particles”, says Borsboom. “The starting point is to allow as much passive regeneration as possible by getting the engine to create the ideal circumstances for this to happen. That is why the exhaust manifold, as well as the most essential parts of the exhaust system, have been encapsulated. If, in spite of this, the temperature of the exhaust gases drops too low in any given situation, the engine will switch to active regeneration. A seventh injector, positioned behind the turbo and ahead of the soot filter, has been added to the engine for this purpose. It injects fuel into an oxidation catalytic converter in the exhaust, in order to generate exactly the right amount of heat. Also the SCR catalytic converter has also been optimised for temperature. Thanks to its innovative coating, it is able to achieve maximum effect across a wider range of temperatures, which means that the engine can function optimally and in the most efficient way as much as possible. Anyway we make sure that exhaust gases enter the SCR catalytic converter at the right temperature as much as possible.”
For its Euro 6 technology DAF has implemented important innovations in all areas. New is a single poly-V belt, as well as a fan that is mounted directly on to the crankshaft without a coupling shaft— which save on maintenance costs, improve reliability and reduce weight and fuel consumption. A larger oil sump volume also allows service intervals of 150,000 km with Euro 6. It is made of composite material to reduce weight and noise levels. The fuel filter and water separator have been combined into a single unit, which is mounted directly on the engine for maximum ease of maintenance, and the oil cooler — usefully combined with the oil filter — is now made from stainless steel to further increase its robustness. Still unique in the industry is the fact that the cable harnesses are encapsulated, just as they are in the current Euro 5 engines.
“In addition to reliability and durability, the biggest keyword in DAF’s Euro 6 technology is efficiency”, says Borsboom. “Achieving the ultra-low Euro 6 emission values requires additional technology, and our aim is of course to keep fuel consumption and CO2 emissions at the low levels of our current Euro 5 ATe vehicles”, says Borsboom. “We have done everything to get the very best out of the technology. DAF never aimed to be the first to introduce Euro 6. It was more important for us to use the time available to come up with the best solutions.”
The new 12.9 litre Euro 6 PACCAR MX-13 engine will enter production early 2013, with outputs of 300 kW/410 hp, 340 kW/460 hp and 375 kW/510 hp. “Obviously, the introduction of new and additional Euro 6 technologies will have consequences for our vehicles”, concludes Borsboom. “We will be revealing these at the IAA in Hanover in September. You can be sure that DAF will come up with something beautiful!”
Source: April 5, 2012 – http://www.hgvuk.com/04/05/daf-unveils-euro-6-engines-with-common-rail/