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Technical Paper

Energy Regeneration of Heavy Duty Diesel Powered Vehicles

1998-02-23
980891
The objective of this study is to improve fuel economy and reduce carbon dioxide emissions in diesel-electric hybrid automotive powertrains by developing an exhaust gas turbine generator system which utilizes exhaust gas energy from the turbocharger waste gate. The design of the exhaust gas turbine generator was based on a conventional turbocharger for a direct-injection diesel engine. Data from steady-state bench tests using air indicates about 50% of the turbine input energy can be converted to electric energy. Turbine generator output averaged 3 kW, while a maximum of about 6 kW was observed. Based on this data, we estimate that energy consumption in a vehicle could be reduced between 5% and 10%. Engine tests were conducted under both steady-state and transient conditions. These tests revealed that optimal performance occurred under high-speed, high-load conditions, typical of highway or uphill driving, and that performance at low-speed, low-loads was relatively poor.
Technical Paper

Combustion Control Method of Homogeneous Charge Diesel Engines

1998-02-23
980509
Under heavy load condition, single fuel operation with diesel fuel was studied experimentally for the homogeneous charge diesel combustion (HCDC) method. HCDC engine, in which pre-mixture was formed by fuel injected into an intake manifold and mixed with air beforehand then ignited by small amount of fuel directly injected into a cylinder, can reduce NOx and smoke simultaneously from the diesel engine. In HCDC the higher the premixed fuel ratio was, the lower the emissions were. Accordingly, it was indicated that homogeneous pre-mixture contributed to improvement of exhaust emissions. However, a diesel knocking due to uncontrolled self-ignition may occur under high premixed fuel ratio conditions in the case of operating heavy loads. Thus, the maximum amount of premixed fuel was restricted by these knocking limits.
Technical Paper

Methane and Nitrous Oxide (N20) Emission Characteristics from Automobiles

1996-02-01
960061
Exhaust gases discharged from automobiles are noticed as one of the reasons for resent increase in atmospheric methane (CH4) and nitrous oxide (N2O) concentration, which have been considered as greenhouse effect gas. In order to make an accurate estimation of methane and nitrous oxide discharged from automobiles, measurement methods of them were experimentally developed and their emissions were measured for different kinds of automobiles under various driving conditions. Then, we have tried to estimate the annual global emissions from automobiles using these measurement results and statistical data such as the number of automobiles, the total annual mileage, and the total annual fuel consumption etc. As results, their emissions from passenger vehicles which have been estimated from global number of automobiles were 477.263 t/year for methane and 313.472 t/year for nitrous oxide. These numbers are higher than what had been estimated.
Technical Paper

Exhaust Purification of Diesel Engines by Homogeneous Charge with Compression Ignition Part 1: Experimental Investigation of Combustion and Exhaust Emission Behavior Under Pre-Mixed Homogeneous Charge Compression Ignition Method

1997-02-24
970313
A homogeneous Charge Compression Ignition Diesel Combustion (HCDC) system has been experimentally studied for it's effect on exhaust purification of diesel engines. In this system, most fuel is injected into the intake manifold to form homogeneous pre-mixture in the combustion chamber beforehand and the pre-mixture is ignited with a small amount of fuel directly injected into the cylinder by a conventional injection system. Because this system performs homogeneous lean-burn, it can realize low emission which cannot be realized by conventional diesel engines without impairing ignition controllability in the operations ranging from idle to full load. In particular, although the operating regions were strictly limited, extremely low Nox emission levels of as low as 10 to 40 ppm were realized with maintaining low smoke emissions, when the ratio of pre-mixed fuel was increased up to approx. 98%.
Technical Paper

Exhaust Purification of Diesel Engines by Homogeneous Charge with Compression Ignition Part 2: Analysis of Combustion Phenomena and NOx Formation by Numerical Simulation with Experiment

1997-02-24
970315
An experimental and a numerical analysis wereconducted based on the concept of homogeneous charge diesel combustion (HCDC), in which most of the fuel is supplied for pre-mixed homogeneous charge which is compressed in the cylinder and then ignited by small amount of diesel fuel directly injected into a cylinder. At the previous report, It was indicated that simultaneous improvement of NOx and smoke were possible. Especially under a certain condition, NOx was extremely reduced. This report describes the preliminary analysis for the cause of this emission improvement with HCDC method. As result, direct optical observation of the combustion phenomena and numerical analysis using KIVA2 code suggested that low NOx combustion may be caused by lowered combustion temperature and reduced combustion period due to the uniform lean combustion.
Technical Paper

Search for Optimizing Control Method of Homogeneous Charge Diesel Combustion

1999-03-01
1999-01-0184
As a method for reducing exhaust emissions from diesel engines, we have experimented on a homogeneous charge diesel combustion technique (HCDC) whereby a portion of fuel is supplied into the intake port to form a homogeneous premixture, this is then fed into the cylinder from the intake port before ignition of the diesel fuel, which is injected directly into the cylinder. Our results have indicated possibilities of substantially reducing both NOx and smoke emissions. If diesel fuel is premixed with air, the premixture under-goes excessively early self-ignition, making it difficult to maintain ignition timing near top dead center and hence limiting the engine operating conditions. While an important target in emission reduction is to realize stable low-emission combustion during a high-load operation, the actual operation of diesel engines mostly involves partial-load conditions.
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