Search Results

The new Diesel Particulate active Reduction (DPR) system was developed for a medium-duty commercial vehicle as a deNOx catalyst combined with the conventional DPR system to achieve the Japan Post New-Long-Term (JPNLT) emissions regulations. It consists of a catalyst converter named as the new DPR cleaner, a fuel dosing injector, NOx sensors, temperatures and pressure sensors. The new DPR cleaner was constructed from a Front Diesel Oxidation Catalyst (F-DOC), a catalyzed particulate Filter (Filter), and a Rear Diesel Oxidation Catalyst (R-DOC). A newly developed Hydrocarbon Selective Catalyst Reduction (HC-SCR) catalyst was employed for each catalyst aiming to reduce NOx emissions with diesel fuel supplied from the fuel dosing injector. While the total volume of the catalyst was increased, the compact and easy-to-install catalyst converter was realized through the optimization of the flow vector and flow distribution in it by means of Computational Fluid Dynamics (CFD) analysis.

Environmental protection is now one of the most important social concerns in the world. In 1998, emission controls in the US required the reduction of NOx by 20% from the 1994 limit. Hino Motors has developed new J-series medium-duty diesel engines for trucks that meet the US 1998 emissions regulations. The engines comprise turbocharged and aftercooled 4- and 6-cylinder engines of the same cylinder bore and stroke. The engines feature a 4-valve system, OHC valve train design, centered nozzle arrangement, and an optimum combustion chamber design, which achieved uniform combustion. With these features, the maximum combustion temperature was decreased, and hence reduced the NOx, smoke, and PM emissions. A muffler integrated with a catalytic converter (catalytic muffler) was adopted to reduce PM emissions further. The engines with the catalytic muffler have successfully met the US 1998 emissions regulations.

Diesel particulate trap systems are one of the effective means for the control of particulate emission from diesel vehicles. Hino has been researching and developing various diesel particulate trap systems for city buses. This paper describes two of the systems. One uses a wall flow filter equipped with an electric heater and a sensing device for particulate loading for the purpose of filter regeneration. Another makes use of a special filter named “Cross Flow Filter” with an epoch-making regeneration method called “Reverse Jet Cleaning”, by which it becomes possible to separate the part for particulate burning from the filter. Both systems roughly have come to satisfy the functions of trap systems for city buses, but their durability and reliability for city buses are not yet sufficient.

Diesel Particulate active Reduction system (DPR) is a system that traps particulate matter in diesel exhaust gas with a particulate filter and actively regenerates the filter when PM accumulates to a specific level. In 2003, DPR was installed on Hino's light-, medium-, and heavy-duty diesel engines, and about 50,000 units of these DPR-equipped diesel engines are currently on the market. This paper reports results of further progress made on optimization of the active regeneration function of DPR. The goal of successful development of DPR is to optimally control the system under various engine-operating conditions to regenerate the filter without producing abnormal combustion of PM and to minimize the amount of unburned PM to keep the filter from clogging. To improve the control of DPR, the combustion phenomena of PM collecting on the filter were studied through visualization, and the factors influencing combustion were determined.

DPR is a particulate-emissions reduction system that has been developed to reduce particulate emissions in production commercial vehicles and consists of a multiple fuel-injection system, an engine electronic control unit, and a DPR-Cleaner which includes an oxidation catalyst, a catalyzed particulate filter, and silencers. DPR performs active regeneration to accelerate the regeneration of the filter under engine operating conditions where regeneration by passive regeneration alone is not sufficient. Thus, DPR makes it possible to regenerate the filter regardless of the exhaust gas temperature and enables significant reduction of particulate in commercial vehicles to levels below 0.027 g/kWh under Japan's D13 mode operating conditions. The authors describe development results of the DPR.

Urea selective catalyst reduction (SCR) systems have a high NOx conversion rate because the ammonia formed by the hydrolyzing urea solution reacts with NOx efficiently as a reducing agent. Systems combining urea-SCR and a diesel particulate filter (DPF) have been adopted in heavy duty vehicles to meet the post new long term emissions regulations in Japan. This study examined the emissions reduction performance of these systems after 160,000 km. The emissions that were examined included both regulated emissions (NOx, PM, HC, and CO) and unregulated emissions. As a result, the cleanness of diesel emissions from a urea-SCR and DPF system was confirmed.

Diesel Particulate Filter (DPF) is a very effective aftertreatment device to limit particulate emissions from diesel engines. As the amount of soot collected in the DPF increases, the pressure loss increases. Therefore, DPF regeneration needs to be performed. Injected fuel into the exhaust line upstream of the Diesel Oxidation Catalyst (DOC), hydrocarbons are oxidized on the DOC, which increases the exhaust gas temperature at the DPF inlet. It is also necessary that the injected fuel is completely vaporized before entering the DOC, and uniformly mixed with the exhaust gases in order to make the DOC work efficiency. However, ensuring complete evaporation and an optimum mixture distribution in the exhaust line are challenging. Therefore, it is important that the fuel spray feature is grasped to perform DPF regeneration effectively. The purpose of this study is the constructing a simulation model.

Approximately 200,000 units of Hino J-series diesel engine were produced for 7 years. The J-series engines had a reputation all over the world for their performance, reliability, lightweight, and installation ability. They are composed of 4, 6 cylinders engines and unique 5-cylinder engine J07C. In 2002, newly modified J-series engines, which met the Japan 2001 noise emission regulations, were developed and J07C-TI, 5-cylinder TI engine, equipped with a common-rail fuel injection system was added in the J-series. Common-rail fuel injection system was equipped in order to achieve the emission targets in the future as well as to meet the current emission regulations. Achieving higher injection pressure level through the all engine speed, include excess low speed, was effective in reduction of PM emissions and in increasing of low engine speed torque drastically.

In order to reduce diesel NOx emissions, aftertreatment methods including LNT (Lean NOx Trap) and urea SCR (Selective Catalytic Reduction) have been researched. One of the shortcomings of urea SCR is its NOx reduction performance degradation at low exhaust gas temperatures and possible emission of unregulated byproducts. Here, a new type of a urea-dosing device to overcome these shortcomings is studied. This dosing device actively produces ammonia without depending upon the exhaust gas temperature, and designed for onboard application. The device incorporates an electrically heated bypass with a hydrolysis catalyst. An injector supplies urea solution into the bypass. The bypass is heated only when thermolysis is needed to produce ammonia (NH3). The hydrolysis catalyst further assists in the production of NH3. The ammonia gas obtained is then mixed with the main exhaust gas flow.