| Regeneration of diesel particulate filters using lambda variation -> Monitor Keywords |
|
|
 
Regeneration of diesel particulate filters using lambda variationRelated Patent Categories: Power Plants, Internal Combustion Engine With Treatment Or Handling Of Exhaust Gas, Methods, Anti-pollutionRegeneration of diesel particulate filters using lambda variation description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070157600, Regeneration of diesel particulate filters using lambda variation. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present invention relates to the use of engine modifications to support or create regeneration conditions of diesel particulate filters, and more particularly, the regeneration of preferably catalytically coated diesel particulate filters using lambda variation. [0002] Today's world of internal combustion engines is dominated by two engine versions, gasoline engines and diesel engines. The ongoing development of the two combustion concepts concentrates on reducing emissions for which legal regulations to protect people and the environment are being increasingly tightened. [0003] Compared to combustion in gasoline engines, diesel engines produce low emissions of carbon monoxide, hydrocarbons and nitrogen oxides, but also greatly increased particulate emissions which are typical of diesel engines. Examining these emissions is of particular significance so that generation, prevention and disposal of particulate emissions can be controlled. Generation and prevention of particulates in conventional diesel engines is still very difficult to influence so that the main focus is on disposal. This trend is strongly supported and required by applicable law. [0004] One way to collect most particulates from the exhaust gas of diesel engines is to use so-called diesel particulate filters. These filters are placed in the exhaust-gas line in order to achieve a highest possible filtering rate for the particulates contained in the exhaust gas. [0005] However, this very effective and efficient filtering process leads to a follow-on problem. That is, the filter becomes increasingly loaded with particulate matter. As a result, it is difficult for exhaust gas to flow through the filter, and a pressure increase is generated upstream of the filter which can be considered to be equivalent to increased exhaust work of the engine. This increased exhaust work is reflected in power loss and increased fuel consumption of the engine, respectively. In order to prevent an unnecessarily high increase in pressure upstream of the filter, the filter must be burned free from time to time. This is done by various regeneration measures and strategies, respectively. [0006] It is strongly expected that the structure of the honeycomb filter, also referred to as a ceramic monolithic cell filter, will determine the technology of diesel particulate filters, hereinafter referred to as DPFs. The DPF is a filter having alternately open and closed channels. As a result of this construction, the exhaust gas is forced to flow through the porous channel walls where particulate matter can deposit on the walls. Therefore, such a filter is also called a wall-flow filter. [0007] In addition to these honeycomb filters, there exist also filters which may have a wound construction, for example. In such a filter, the exhaust gas passes through without meeting a direct obstacle. Its construction is similar to a catalyst, i.e., without any closed channels. Compared to the honeycomb filter, which may achieve a filtering effect of more than 99%, the filtration efficiency for particulate matter is in an unacceptable low range, however. [0008] Moreover, there are sintered metal filters, wound fiber filters, knitted fiber filters, braided fiber filters and filter papers as well as non-woven filters. Taking all parameters such as production expenditure and manufacturing cost, physical properties, filtering effect, durability etc. into account, honeycomb filters have advantages over any other filter development. [0009] Regeneration of DPFs (without any additional modifications) is a chemical reaction which may be considered a pure oxygen regeneration (oxidation of soot). It starts at temperatures around 360.degree. C. but only above 550.degree. C. reaction and oxidation rates are achieved that are interesting from a practical point of view. This means that only at those temperatures sufficiently fast regeneration rates can be obtained which constitute an economically acceptable solution with respect to using the DPFs in vehicles. [0010] The following regeneration strategies when employing diesel particulate filters are known: [0011] diesel particulate filters with additive support, [0012] CRT systems, [0013] catalytically coated diesel particulate filters, [0014] electrically supported diesel particulate filters, [0015] diesel particulate filters with burner systems, and [0016] compressed-air purged diesel particulate filters. [0017] In catalytically coated diesel particulate filters, for example, metals are introduced into the surface of the filter. These metals serve as a catalyst lowering the soot ignition temperature below 400.degree. C. Using various noble metals, it is possible to reduce this initial temperature even further to a range below 350.degree. C. In addition, an oxidation catalyst may be provided upstream of the DPF to oxidize NO contained in the exhaust gas to NO.sub.2 using the residual oxygen, thus supporting regeneration. Provided that the exhaust-gas temperatures exceed the initial temperature for a sufficiently long period of time, catalytically coated DPFs may be regenerated sufficiently well. [0018] In intensive test series using catalytically coated diesel particulate filters on engine test benches, dynamic test cycles are being developed to simulate a real driving mode of a motor vehicle. The engine speed and load spectra during these tests are based on standardized exhaust-gas tests. These test cycles include both urban and extra-urban operation. The engine speed and load spectra occurring differ in that the percentage utilization of the engine in urban operation is very low (refer to FIG. 1). By comparison, the engine load in extra-urban operation is relatively high. Directly related to this percentage utilization of the engine is its exhaust-gas temperature. Accordingly, high temperatures in the exhaust gas are reached at high utilization in extra-urban operation, while relatively low temperatures are reached in urban operation (refer to FIG. 2). [0019] The reason for simulating the real driving mode on the engine test bench is that the pressure loss behavior of a DPF may be predicted for later employment on a vehicle. [0020] The engine's exhaust-gas temperatures are directly related to its percentage load (refer to FIGS. 1 and 2). As described above, this leads to very low temperatures in urban operation and very high temperatures in extra-urban operation. FIG. 3 depicts the temperature curve for urban operation. This curve may be plotted at any position in the exhaust-gas line and is thus regarded as a temperature spectrum in the exhaust-gas line. FIG. 4 shows the same situation for extra-urban operation. [0021] Various engine speed levels are used for extra-urban operation during the test series. Thus, various temperature characteristics are obtained. As a result, temperature levels at which practically acceptable regeneration occurs may be determined for different filters. [0022] The main conclusion from the results of the dynamic test cycles may be divided into two parts. One conclusion to be drawn is that the temperature spectra in extra-urban operation may be sufficient in order to force regeneration of the filter. This is achieved in an acceptable range as regards time. The second conclusion is that urban operation, due to its low temperature spectrum, fails to generate practically usable regeneration conditions. [0023] These conclusions may be understood from FIGS. 5 and 6. These figures indicate the pressure loss described above. In persistent urban operation, this pressure loss increases with the duration of the test due to the rising filter loading (FIG. 5). [0024] The regeneration conditions in extra-urban operation may be generated in such a satisfactory manner that a decrease in pressure loss is possible after only a short period of time. As an example, FIG. 6 shows a dynamic test involving a combination of both modes of operation. During extra-urban operation, which is very brief compared to urban operation, a rapid decrease in pressure loss is generated so that a falling pressure loss may be achieved over the entire duration of the test. [0025] In summary, satisfactory regeneration of the filter may be achieved in extra-urban operation, but not in urban operation. [0026] For the technology of diesel particulate filters to be interesting for all vehicle applications, the regenerative capacity must be provided in every operating mode of the corresponding vehicle. Development and application of the urban test cycle, which can simulate the driving mode for buses, garbage trucks or taxicabs, for example, has already shown that this "condition" cannot be met without any further modifications. [0027] Accordingly, it is an object of the present invention to provide a method enabling regeneration of the filter at any point of time irrespective of the load profile (operating mode) of the vehicle. This type of regeneration will be referred to as regeneration on demand. [0028] This object is solved with the features according to the claims. [0029] In conventional diesel engines, quality-controlled combustion takes place. This means that the quality of the supplied mixture of air and fuel is controlled. This principle is implemented by controlling the fuel flow rate depending on the operating point of the engine (load/torque increase is achieved by raising the fuel flow rate). The air supply remains unaffected at all times. This results in different ratios of air and fuel which can be expressed using the dimensionless quantity lambda: .lamda. = air .times. .times. flow .times. .times. rate .times. [ kg .times. / .times. h ] 14.6 * fuel .times. .times. flow .times. .times. rate .times. [ kg .times. / .times. h ] [0030] In a conventional diesel engine, the air flow rate is constant when the engine speed is fixed. Thus, lambda may only be influenced by the fuel flow rate. Combustion in diesel engines operates with excess air, i.e., more air is present than would be necessary for combustion. Therefore, lambda does not fall below 1. Further, if combustion in diesel engines falls below a lambda value of 1, it meets its functional and misfire limit, respectively. Looking at characteristic maps of diesel engines, the lowest lambda values are found at full load, as the fuel flow rate is largest in this case. Continue reading about Regeneration of diesel particulate filters using lambda variation... Full patent description for Regeneration of diesel particulate filters using lambda variation Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Regeneration of diesel particulate filters using lambda variation patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Regeneration of diesel particulate filters using lambda variation or other areas of interest. ### Previous Patent Application: Method for operating a compression-ignition internal combustion engine Next Patent Application: Tank system with a main tank and a melting device having a melt tank Industry Class: Power plants ### FreshPatents.com Support Thank you for viewing the Regeneration of diesel particulate filters using lambda variation patent info. IP-related news and info Results in 0.15725 seconds Other interesting Feshpatents.com categories: Computers: Graphics , I/O , Processors , Dyn. Storage , Static Storage , Printers 174 |
 * Protect your Inventions * US Patent Office filing 
PATENT INFO |
|
