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The effects of diesel fuel properties (aromatic content, cetane index and T90), cetane improver, oxygenates, high boiling point hydrocarbons and aromatics distribution on diesel exhaust emissions were studied under the Japanese 10-15 test cycle and the ECE+EUDC test cycle. The test vehicle was a TOYOTA COROLLA with a natural aspirated, 2.0L displacement, IDI diesel engine. It was demonstrated that particulate emissions are highly correlated with T90 and that NOx is affected by the aromatic content of fuel. A reduction in particulates emissions was observed in fuel with a lower cetane number by adding cetane improver, but this reduction was limited. Cetane improver had no effect on NOx emissions in the 45 # 60 cetane number range. Oxygenates reduced particulate emissions remarkably but had little effect on NOx emissions. A decrease in the soot in particulates was particularly observed.

Recently, the California Air Resources Board (CARB) has proposed a new set of evaporative emissions and “Useful Life” standards, called LEVII EVAP regulations, which are more stringent than those of the enhanced EVAP emissions regulations. If the new regulations are enforced, it will become increasingly important for the carbon canister to reduce Diurnal Breathing Loss (DBL) and to prevent deterioration of the canister. Therefore, careful studies have been made on the techniques to meet these regulations by clarifying the working capacity deterioration mechanism and the phenomenon of DBL in a carbon canister. It has been found that the deterioration of working capacity would occur if high boiling hydrocarbons, which are difficult to purge, fill up the micropores of the activated carbon, and Useful Life could be estimated more accurately according to the saturated adsorption mass of the activated carbon and the canister purge volume.

The emission characteristics of hydrocarbons during the cold start and the warm-up have been investigated. Timed sampling of hydrocarbon emissions upstream and downstream of a close-coupled catalytic converter have been carried out. The experimental results show that the emission characteristics of hydrocarbons are influenced by both the engine operating conditions and the heating characteristics of the catalytic converter. In the case of engine-out hydrocarbons, the total amount of hydrocarbons drastically decreases but the percentage contribution of the C2-C4 olefins to the engine-out hydrocarbons increases as the warm-up proceeds. Since these olefins have relatively high maximum incremental reactivity (MIR) factors, the specific reactivity (SR) of the engine-out hydrocarbons gradually increases during the warm-up. The adsorption and desorption processes of the engine-out hydrocarbons on the catalyst occur before the catalyst light-off.

The design of the newly developed Toyota AZ series 4 cylinder engine has been optimized through both simulations and experiments to improve heat transfer, cooling water flow, vibration noise and other characteristics. The AZ engine was developed to achieve good power performance and significantly reduced vibration noise. The new engine meets the LEV regulations due to the improved combustion and optimized exhaust gas flow. A major reduction in friction has resulted in a significant improvement in fuel economy compared with conventional models. It also pioneered a newly developed resin gear drive balance shaft.

A new heating strategy for electrically heated catalysts has been developed which reduces power consumption while achieving the desired hydrocarbon conversion. The relationship between catalyst volume and power consumption is presented. Observations of catalytic reactions by a thermoviewer camera and mathematical simulations are used to optimize the heating pattern. Significant reductions in power consumption, while maintaining conversion efficiency, are reported by heating only the front face of the catalyst. However, prior to mass production additional work is required to improve durability, and reliability and to resolve manufacturing issues.

In order to satisfy future demands of low exhaust emission vehicles (LEV), a new fuel injection control system has been developed for SI engines with three-way catalytic converters. An universal exhaust gas oxygen sensor (UEGO) is mounted on the exhaust manifold upstream of the catalytic converter to rapidly feedback the UEGO output signal and a heated exhaust gas oxygen sensor (HEGO) is mounted on the outlet of the converter to achieve an exact air fuel ratio control at stoichiometry. The control law is derived from mathematical models of dynamic air flow, fuel flow and exhaust oxygen sensors (HEGO and UEGO). Experimental results on FTP (Federal Test Procedure) exhaust emissions show a dramatic reduction of HC, CO and NOx emissions and a possibility of practical low emission vehicles at low cost.

In order to reduce tail-pipe hydrocarbon emissions from SI gasoline engines, rapid catalyst warm-up and improvement of catalyst conversion efficiency are important. There are many reports which have been published by manufacturers and research institutes on this issue. For further reduction of tail-pipe hydrocarbon emissions, it is necessary to reduce engine-out hydrocarbon emissions and to improve after treatment, during the time the catalyst is not activated. This paper quantitatively analyzed the fuel amount of intake port and cylinder wall-wetting, burned fuel and engine-out hydrocarbon emissions, cycle by cycle in firing condition, utilizing a specially designed analytical engine. The effect of mixture preparation and fuel properties for engine-out hydrocarbon emissions, during the cold engine start and warm-up period, were quantitatively clarified.

The purposes of this paper are to develop a new laboratory oxidation stability testing method and to clarify factors relative to the viscosity increase of engine oil. Polymerized products, obtained from the oil after a JASO M333-93 engine test, were found to consist mainly of carboxyl, nitrate and nitro compounds and to increase the oil viscosity. A good similarity between the JASO M333-93 test and the laboratory simulation test was found for the polymerized products. The products were obtained not by heating oil only in air but by heating oil while supplying a synthetic blowby gas consisting of fuel pyrolysis products, NO, SO2 and air. The laboratory test has also revealed that the viscosity increase depends on oil quality, organic Fe content and hydrocarbon composition in the fuel. Moreover, it has been found that blowby gas and organic Fe accelerate ZnDTP consumption and that aromatics concentration in the fuel correlates with the viscosity increase of oil.

A new hybrid system has been developed which features a highly efficient, clean gasoline engine, and a high performance exhaust catalyst system. The new system meets the strictest low emission standards in the world, while realizing a major reduction in CO2 emissions. The Toyota Hybrid System (THS) has improved engine performance, transaxle transmission efficiency, and various vehicle improvements for improving fuel consumption. It also employs a high performance catalyst, a rapid catalyst warm-up strategy, Toyota HC Adsorber and Catalyst System (Toyota-HCAC-System) and a Vapor Reducing Fuel Tank System. These combined technologies allow for the achievement of U.S. California SULEV, European Step 4 and Japanese J-ULEV emission requirements. It has also lowered the CO2 level to less than 120g/km in EC European mode.

The original Toyota Hybrid System (THS) was installed in the Prius and was introduced in 1997 as the world's first mass-produced hybrid passenger car. THS has been continuously improved. In 2003 THS-II (marketed as Hybrid Synergy Drive [HSD]), was installed in a new larger Prius. In 2005 HSD was installed in two SUVs: the RX400h and Highlander Hybrid. This system achieved both V8 engine power performance and compact class fuel economy with outstanding emissions performance. In 2006, the HSD line-up is expanded to front-engine rear-wheel (FR) drive in the Lexus GS450h. This paper will explain this hybrid system which achieves both 4.5-liter class power performance and compact class fuel economy, while meeting the most stringent emission standard SULEV.

The original Toyota Hybrid System (THS) was installed in the Prius and was introduced in 1997 as the world's first mass-produced hybrid passenger car. Since then, THS has been continuously improved. In 2003 THS-II (marketed as Hybrid Synergy Drive [HSD]), was installed in a new larger Prius. In 2006 HSD was installed in a Rear Wheel Drive Vehicle: the LEXUS GS450h. This system achieved both 4.5-liter class power performance and compact class fuel economy with outstanding emissions performance. In 2007, this system is expanded to a mechanical all-wheel-drive(AWD) in the LEXUS LS600hL(with new V8 engine). This paper will explain this hybrid system which achieved both V12 class power performance and mid-size class fuel economy, while meeting the most stringent emission standard SULEV as a full-size vehicle.

Ignition and combustion control of HCCI (Homogeneous Charge Compression Ignition) in DI (Direct Injection) Diesel Engine were examined. In this study, double injection technique was used by Common Rail injection system. The first injection was used as an early injection for fuel diffusion and to advance the changing of fuel to lower hydrocarbons (i.e. low temperature reaction). The second injection was used as an ignition trigger for all the fuel. It was found that the ignition of the premixed gas could be controlled by the second injection when the early injection was maintaining low temperature reaction. It was found that as the boost pressure increased, ignition timing advanced slightly and the rate of pressure increase markedly decreased. The rate of pressure increase is one of the factors concerning operation limit in this combustion. Therefore, the VNT (Variable Nozzle Turbo-charger) was applied to the production engine to allow boost pressure control.

Precise analytical methods for characterizing diesel fuel yielding the lowest particulate emissions were developed. The methods consist of preparative-scale high pressure liquid chromatography (HPLC), field ionization mass spectrometry (FIMS), analytical-scale HPLC, and carbon-13 nuclear magnetic resonance spectrometry (13C-NMR). A diesel fuel was first separated into an aliphatic fraction and an aromatic fraction by semipreparative-scale HPLC. Then, the aliphatic fraction was analyzed by FIMS and the spectrum was compared with that of the whole fuel. The aromatic fraction was analyzed by analytical-scale HPLC to obtain the chromatogram of the aromatic hydrocarbons with a high S/N. In addition to these analyses, the fuel was analyzed by 13C-NMR to obtain the concentration of the carbon atoms of the straight chain, branched chain and aromatic-ring in hydrocarbons.

The compositions of hydrocarbons in diesel fuel, exhaust gas and particulates were analyzed and the relationships among them were determined. It was found that the compositions of the hydrocarbons in the exhaust gas were almost the same as that of the fuel, and that the hydrocarbons in the particulates corresponded to their heavy fractions. When the engine condition was fixed, both the soluble organic fraction (SOF) and insoluble fraction ( ISF) showed positive correlation coefficients versus HC×R310, where HC denotes the hydrocarbon emission and R310 denotes the backend fraction, as measured by the fraction of fuel boiling above 310°C. On the other hand, when the engine condition was varied, ISF had negative correlation coefficients versus HC×R310, while SOF showed positive correlation coefficients.

The properties of diesel fuels were investigated in terms of particulate emissions to clarify the specification of such a diesel fuel for minimizing particulate emissions. Diesel fuels were analyzed using thin layer chromatography (TLC), and gas chromatography/mass spectrometry (GC/MS). These analysis revealed the entire composition of hydrocarbons in diesel fuels according to molecular formula. The entire composition of hydrocarbons in diesel fuels could be expressd on a three-dimensional graph: the X-axis as carbon number, the Y-axis as H/C ratio and the Z-axis as the amount of hydrocarbons of identical molecular formula. By using the graph, the properties reported so far were investigated. Also, simplified images of the fuel sprayed into a cylinder and its flame were derived from the observational results previously reported.

The effects of the phosphorus and sulfated ash contents of engine oils on the deactivation of monolithic three-way catalysts and oxygen sensors were studied. The effect of temperature was evaluated as well. The catalysts and oxygen sensors were poisoned in a 100-hour engine bench test. As a result, it was learned that engine oils with higher phosphorus contents showed a higher concentration of phosphorus on the catalyst surfaces, and the ability of the catalysts to convert carbon monoxide and oxides of nitrogen decreased. However, the phosphorus content was not observed to have any effect on hydrocarbons. The sulfated ash reduced the phosphorus concentration on the catalyst surface, but it also had a negative effect on the catalytic activity. The deactivation of the catalysts was much more noticeable at 800°C than at 720°C. In the tests at 720°C and 800°C, no deactivation of the oxygen sensors was observed, regardless of the composition of the engine oil.

In response to various reformulated gasoline regulations, several studies have been conducted to evaluate the relationship between fuel properties and vehicle exhaust emissions. These studies, however, have focused on the fuel effect and have not examined the most promising advanced technology emission control systems on low emission vehicles. Toyota's reformulated gasoline research first set out to study the effect fuel compositions has on 2 different emission control systems. On both systems, non-methane hydrocarbon (NMHC) emissions were significantly affected by the 50% and 90% distillation temperature (T50 and T90). A correlation was also found exhaust olefine content and the amount of MTBE contained in the fuel. Research was also conducted on the specific ozone reactivity (SOR) of exhaust hydrocarbons. Various fuels with similar specifications but blended from different feedstocks were evaluated.

The effect of the chemical reactivity of diesel fuel on PM formation was investigated using a flow reactor and a shock tube. Reaction products from the flow-reactor pyrolysis of the three diesel fuels used for the engine tests in Part 1(1) (“Base”, “Improved” and Swedish “Class-1”) were analyzed by gas chromatography. At 850C, Swedish “Class-1” fuel was found to produce the most PM precursors such as benzene and toluene among the three fuels, even though it contains very low amounts of aromatics. The chemical analyses described in Part 1 revealed that “Class-1” contains a large amount of branched and cyclic structures in the saturated hydrocarbon portion of the fuel. These results suggest that the presence of such branched and ring structures can increase exhaust PM emissions.

Combustion and exhaust emission characteristics were compared among three representative diesel fuels called “Base (corresponding to a Japanese market fuel)”, “Improved” and Swedish “Class-1” using both a modern small and an optically accessible single-cylinder DI diesel engines. In these tests, the relative amount of PM collected in the exhaust was “Base” >“Class-1” >“Improved” at almost all of the operating conditions. This means that “Class-1” generated more PM than “Improved”, even though “Class-1” has significantly lower distillation temperatures, aromatic content, sulfur, and density compared with “Improved”. There was little difference in combustion characteristics such as heat release rate pattern, mixture formation and flame development processes between these two fuels. However, it was found that “Class-1” contained more branches in the paraffin fraction and more naphthenes.

Vehicle emissions tests were conducted using a 1992 model year Toyota Camry for California under the 1975 Federal Test Procedure. Nine fuels of different composition were prepared. Effects of gasoline composition and sulfur content on tailpipe and engine-out emissions were investigated. Exhaust mass emission test results indicated that gasoline distillation properties and sulfur content have large effect on non-methane organic gas emissions. Furthermore, fuel, engine-out, and tailpipe hydrocarbons were speciated and the relationship between fuel and exhaust specific ozone reactivity analyzed. From these studies, it is concluded that aromatics are the largest contributor to the specific ozone reactivity of exhaust emissions and these aromatics, in emissions, are mainly unburned and partly oxidized aromatics from the fuel. Fuel MTBE correlates with exhaust olefins and oxygenates.