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OVERCOMING DPF PROBLEMS IN 2007 ENGINES
It is clear that managements of many trucking fleets have shown a reluctance to purchase 2007 diesel engines, which indicates their serious concerns as to how the 2007 engines will perform.
All 2007 diesel engines will be equipped with Diesel Particulate Filters (DPF), which use has been mandated by the Environmental Protection Agency (EPA), to lower emissions. An ultra-low-sulfur diesel fuel (ULSD) must be used with the DPF. The sulfur content of the ULSD has been reduced from 500 PPM to 15 PPM. The use of ULSD fuel is of major concern to truck owners as there are a number of potential problems associated with using said fuel. Its use results in reduced fuel efficiency, loss of lubricity and higher prices for fuel itself.
The lower energy content of ULSD will cause Truckers to buy more fuel to run the same amount of miles. The stripping of the sulfur from the fuel will result in a power loss of approximately 3%, caused by a reduction in the density of the fuel. Query; can these additional costs be passed onto the customers by way of surcharges? That might prove to be very difficult, since in common practice, contracts do not provide for additional billing, based on additional consumption, because of a change in fuel.
The DPF itself is a cause of great concern, since the filter will operate efficiently, only when it is kept clean. The filter operates by trapping particulate matter and burning it at high exhaust temperatures, keeping its honeycomb structure clean. If the filter becomes clogged, turbocharger failure can result.
In order to keep the DPF clean, the engine manufacturers redesigned their engines to generate higher exhaust temperatures. The result is a substantial increase, approximating 30%, in engine compartment temperatures. Two methods are employed to keep the DPF clean; passive regeneration and active regeneration. Passive regeneration is the most important method, as it will occur up to 85% of the time in typical over the road hauling. By maintaining the exhaust temperature at approximately 650 °F, while in normal driving mode, the DPF will remain basically clean. Active regeneration occurs when the DPF reaches a critical point of clogging that cannot be dealt with by passive regeneration. In this case the temperature in the filter must reach approximately 1200 °F (a process that can take about 40 minutes). The engine manufacturers have developed different technologies to reach the higher temperature, which technologies employ the injection and ignition of additional fuel into the collection chamber.
Using fuel to facilitate filter regeneration will create a 2% to 5% fuel penalty.
Question; where should the DPF be mounted? If it is mounted at a far distance from the engine exhaust, a significant reduction, in temperature, will occur. Studies have shown that the further the DPF is from the engine exhaust, the greater the temperature losses. The loss can be as much as 122 °F for every one inch of pipe exposed to air. It is clear, that additional heat must be created to keep the DPF functioning properly, and consequently, the engine compartment has to be hotter. The higher engine compartment temperatures will heat up the air intake system, which will lead to greater fuel consumption and reduced MPGs, as well as requiring more engine maintenance and parts replacements.
The current temperature at the outlet of the muffler for pre-2007 engines only reaches approximately 275º F. This temperature must be raised to 650ºF for passive regeneration in the DPF to take place. The need to increase the temperature to such a major degree provides a better understanding as to why the overall engine compartment temperatures are increased by some 30% in the 2007 engines.
This understanding gives us better insight into the concerns of the fleet owners with the 2007 diesel engines. The key question is, can these many potential problems be overcome and if so how?
There is one way to overcome these many problems. A Florida based company, American Diesel & Gas, Inc. (AD&G), has developed a solution. AD&G has developed a patented technology called Q-Shield™ . Q-Shield™ is a proprietary composite multi-layered non-conductive insulator, the major function of which is to control heat in the engine compartment.
Since the 2007 diesel engines are expected to generate 30% more heat than the current engines, it is critical that the heat be contained. Q-Shield™ is attached to all the key parts of the engine that generate excessive heat. In this way heat is prevented from impacting various engine parts and causing them to fail prematurely.
The components that are insulated consist of the exhaust manifold, which is the prime source of heat generation; the manifold shield is designed so that the heat is directed downwards, toward the ground, and away from the engine compartment; the turbocharger is partially shielded, so as not to impact the turbocharger’s lubrication system. A shield also covers the top and the side of the compressor, which faces the turbocharger thereby preventing the heat emanating from the side of the turbocharger in affecting the compressor and also reduces the release of heat generated by the compressor.
Protective shields are also applied to the entire air intake system. The air box, if located in the engine compartment, is completely shielded, together with the hot and cold air piping. Shields are also attached to the intercooler, to improve its efficiency. Q-Shield™ has now shielded all the key parts of the engine that generate heat. The total air intake system is protected, resulting in improved MPG.
To prevent heat loss from the exhaust piping that connects to the DPF, AD&G will apply a protective heat shield to the entire exposed piping system. The purpose of the shield is to retain heat in the exhaust piping system and enable exhaust air to reach the DPF at maximum temperature. A critical point is that the higher heat level will keep the DPF from clogging. Should the DPF become clogged, the result could be turbo and compressor failure.
Q-Shield™ technology has been very successful in controlling under hood generation of heat. Field results were formally confirmed in a dynamometer test conducted by a major engine manufacturer, which showed heat reductions ranging from 40% to 50%, in many key engine areas. The test vehicle was a heavy-duty Class 8 truck.
Q-Shield™ heat reduction technology has major advantages on many levels. Firstly, it substantially increases the life of engine components. Secondly, it reduces the amount of required maintenance per vehicle. Thirdly, it allows the shielded air intake system to transmit cooler air into the shielded intercooler system. This allows the intercooler to produce colder denser air, resulting in a more complete combustion thereby increasing MPG by 10% to 20%, as well as increasing the engine’s power by some 20%. The application of Q-Shield™ technology is a viable and proven way to overcome the very serious problem of under hood heat. It is also a way of recovering lost MPG.
The next major problem is ensuring that the temperature in the exhaust area is high enough to allow the DPF to function properly. Again, Q-Shield™ technology provides a viable way to ensure increased heat at the exhaust area where the DPF will be mounted. In an independent dynamometer test, carried out by a major engine manufacturer, the use of these shields, on a class 8 truck, resulted in a temperature increase of some 200% at the outlet of the muffler (in a pre-2007 current diesel engine).
This is a result of a more complete combustion rate of the fuel. The higher combustion rate is due to the air entering the combustion chamber in a cooler and denser state, resulting from the application of Q-Shield™ technology to the entire air intake system, and those elements of the engine that produce excessive heat.
It is critical to mount the DPF as close to the end of the exhaust pipe coming out of the turbocharger as possible, in order to take advantage of the higher heat generated at that point. The further away from the point that the DPF is mounted, the higher the heat loss.
Higher exhaust temperatures generated by the application of Q-Shield™ technology, provides the 2007 diesel engine user with a greater level of protection regarding the placement of the DPF. Currently, there is NO uniform agreement as to where each manufacturer will place the DPF. The ability of AD&G’s Q-Shield™ to generate 200% more heat at the exhaust point would still permit both passive and active regeneration processes to take place successfully in those cases where the filter is mounted some distance away from the point of maximum heat generation.
In conclusion, use of Q-Shield™ technology offers fleet owners, using 2007 diesel engines, viable answers to overcoming their DPF problems, and will do so at a modest cost.