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For the worldwide environmental problems and fuel economy concerns, turbochargers have become essential technology for diesel engines. The number of variable geometry turbocharger turbines which are used for diesel engines instead of conventional fixed geometry or wastegated turbines has increased. The flow range of the variable geometry turbine expands by changing the nozzle exit angle around the turbine wheel. Compressors also require wide flow range and high efficiency to match variable geometry turbines. On the other hand, to improve both the performance at low engine speed and the max output, gasoline engines also require the wide range and high efficiency turbocharger compressors. Almost turbochargers for passenger vehicles are still using conventional fixed geometry compressors. The new variable geometry diffuser whose vanes can be put in and out at the diffuser passage was developed for the turbocharger compressor.

The Lysholm compressors is developed and is produced as a high-efficiency supercharger optimum for use in automotive engines. This paper describes a second-generation Lysholm compressor that has a self-contained lubrication system and a low inertia, and describes the systems connecting the engine and the Lysholm compressor.

In the case of turbocharged heavy duty diesel engines, the total efficiency of the turbocharger is higher than for smaller turbos for passenger cars. It is difficult to recirculate exhaust gas because of higher intake manifold pressure in comparison to exhaust gas pressure. IHI has developed a new turbocharger for exhaust gas recirculation for heavy duty diesel engines. It has a recirculation port at compressor side. The port is connected with a narrow annular slit located at the diffuser inlet, where the static pressure is lower than intake manifold. The result of JIS diesel 13 mode test with this turbocharger showed 26 % lower NOx without significant penalty of fuel consumption.

Recently, passenger cars require better acceleration from low engine speed including starting-up in order to decrease the amount of paticulate matter (PM) of diesel engines or to improve the driver's feeling. However, turbocharged cars generally have worse response than the non turbo cars because it takes a few seconds to get the turbocharger rotate up to high speed, usually called “Turbo-lag”. In order to solve this, various technologies have been developed for a turbocharger itself as well as for charging system such as the sequential system. Here in this paper, we focus on the development of the following turbocharger technology to reduce Turbo-lag and to achieve better transient response. 1. MIXED-FLOW TURBINE IMPELLER 2. TWIN ENTRY TURBINE HOUSING 3. BALL BEARING SYSTEM 4. SEPARATED THRUST BEARING SYSTEM

Reducing the oxides of nitrogen (NOx) and particulate matter (PM) from Diesel engine exhaust gas has become very important problem in view of the protection of environment and the saying energy. But it is difficult to reduce both emissions significantly at the same time by engine modifications and operating condition control. Because, their characteristics have a trade off relation. Therefore many investigators are studying the aftertreatment technique of Diesel engine emissions such as a PM trap filter, EGR, etc. The aftertreatment technique is expected that engine operating condition limits will be loose and engine efficiency will be improved. A few years ago, Iwamoto showed that Zeolite catalyst could reduce the NOx with hydrocarbon reducing agents under oxygen rich condition[1]*. After that, many researchers have been investigating Zeolite catalysts[2]-[4].

In the fields of the internal combustion engines for automobile and marine use, higher output power, higher efficiency and lower fuel consumption are strongly expected. The problems of environment such as a global greenhouse effect or an acid rain is getting worse. Therefore the exhaust gas regulations had been introduced and being strengthen in the USA, Europe and Japan. These regulations demand the reduction of NOx and particulate matter(PM) from diesel exhaust gas at the same time. The turbocharging has been more important technique for these regulations. For automobile engines, it is common to use the pulse turbocharging system for compactness and advantage of response. The characteristics of compressor and turbine are different from under steady state condition by pulsating flow. Especially, it is difficult to estimate the performance of turbine mounted on engine by using the map measured under steady state flow.

Many kinds of turbochargers have been mounted to engines for automotive use. Now, conventional, wastegated, variable geometry turbocharger and many systems are available. These turbocharged engines have many advantages, such as a high specific output power and good efficiency. Diesel engines are more suitable to turbocharging than spark ignition engines. But recently for a growing interest in acid rain and green house effect problems, regulations of engine exhaust gas emission have been tightened in Japan, USA and Europe. NOx and particulate matter from automotive engines must be reduced. In the USA, transient response of boost pressure has been important also for the EPA transient test mode. To cope with these regulations, diesel engine manufacturers demand turbocharger makers to provide far higher boost pressure than ever to supply more air to engines to improve combustion process.

In the field of heavy duty diesel engines for trucks, fuel economy and high output power are required and have been improved. In the past, exhaust gas regulations have mainly applied to spark ignition engines. Recently, their main targets have changed to diesel engines. Especially, the new U.S. reguration in 1991 and 1994 are very severe ones. Engine makers of the world are challenging this new target vigorously. These emission regurations demand more from the turbocharger. In addition to improved efficiency, better air fuel ratio control is required. The variable geometry turbocharger (VGT) gives an improvement in air fuel ratio control, but it's effectiveness can be limited by the control system, IHI has a VGT in production with a 4 step control. The fuzzy control adjusts the vanes continuously and it's development is the subject of this paper. The controller consists of a micro processor, sensors and a stepping motor to drive nozzles.

Turbochargers have become very popular on passenger cars since the first mass-produced turbocharged passenger cars were put on market in Japan in 1979. Turbo lag is one of the most serious problem since the first mass-production started. Several new technologies such as a variable geometry turbocharger, ceramic turbocharger, etc. have been introduced to improve acceleration performance. A variable geometry turbocharger changes the area of gas flow passage and increases exhaust gas speed at low engine speed. A ceramic turbocharger reduces inertia moment of a turbine wheel and shaft. Turbocharger mechanical efficiency has equal importance as compressor efficiency and turbine efficiency. This paper describes the test results of ball bearing turbochargers developed at our company.