R&D on New-Generation, Environment-Improved Diesel Fuel Technology

Transcription

1 2001.M4.1.2 R&D on New-Generation, Environment-Improved Diesel Fuel Technology (New Generation Light Oil Group) Mitsuo Tamanouchi, Yasuhiro Kotani, Koichi Tsujimoto, Shigeo Senbokuya, Koichi Doya, Hiroshi Ikezawa, Nobuyuki Takahashi, Masayuki Kagami, AkiraHozumi, Akihiro Misumi, Atsuo Kurokawa, Tsutomu Takahashi, Yoshinori Miyamoto, Hiroshi Kaneko, Hiroaki Hara, Shigemi Yamahira, Katsuhiro Misono, Masafumi Oikawa, Shigeru Suzuki, Eisaku Sato, Takato Fujii, Tomonori Takada, Toshihiko Suetomi, Tetsuo Sanda, Shogo Suzuki 1. Contents of Empirical Research 1.1 Overview Although automobile emissions regulations are being made more and more stringent in an effort to improve air quality, the atmosphere in large urban areas remains unimproved. Following the decision reached in the Amagasaki law suit over pollution in January 2000, the campaign to have no diesel vehicles in Tokyo, and other such developments, demands for the reduction of emissions from diesel vehicles have been intensifying. In the Fourth Report of the Central Council for Environment Control in November 2000, it was recommended that new long-term regulations be brought forward (from 2007 to 2005) and that 50 ppm sulfur diesel fuel be provided by the end of In responding to such changes in social conditions, it is crucial to relate matters to proper quality design based on confirmation of the effectiveness of diesel fuel quality improvements aimed at reducing diesel vehicle emissions. Accordingly, the effectiveness of fuel properties on the reduction of new-type vehicle emissions was investigated. In addition, the effect of fuel properties on exhaust emissions passed after-treatment devices were examined, as were methods of analysis of PM emission composition, etc. In the investigation of effectiveness in reducing new vehicle emissions, the emissions performance of the world s first diesel vehicle equipped with Diesel Particulate Filter (DPF) device (in compliance with Euro III exhaust emission regulations) was evaluated. In order to investigate the effects of fuel injection systems and fuel properties on the PM emission, the effects of fuel properties on injection rate, atomization characteristics, etc., were examined using a constant-volume vessel. In the investigation of after-treatment devices, the DPF devices were attached to vehicles and engines already on the market, and the effect of fuel properties (sulfur content, T90, aromatic content, and poly aromatic hydrocarbons content) before and after DPF attachment were examined. With respect to heavy duty vehicles, the PM reduction effect of continuous regenerating DPF in some engines was investigated together with DPF regeneration by fleet test. The Fuel - Borne Catalyst (FBC), which is believed to be effective in lowering the soot burn off temperature, was also evaluated. 1

2 In an investigation of analysis methods for the PM emission compositions, improvements in the accuracy of analysis of PM compositions when the DPF is attached were considered, as were PM particle diameter measurement methods, etc. This report presents a discussion of the aforesaid topics of investigation. 2. Results of Empirical Research and Analysis Thereof 2.1 Reduction of New Vehicle Emissions by Improving Fuel Properties Exhaust Emissions Performance of the Latest DPF-Attached Diesel Vehicle The world s first diesel vehicle with DPF attached (in compliance with EuroIII exhaust emission regulations) was sold in Europe in May of The vehicle s DPF regeneration technology employs a high-pressure injection pump with a common rail, an oxidation catalyst, DPF of silicon carbide (SiC) material and a Ceria-based FBC, and the DPF can be regenerated by combining these elements. The vehicle s DPF regeneration system is illustrated in Figure It was decided to evaluate the collection of soot and regeneration performances of this DPF system, as well as investigate the effect of fuel properties. Steps were also taken to collect data on initial exhaust emissions performance, on temporal changes in emissions and on road traveling status. Fuel tank High-pressure pump Engine control CPU Sensor Additive tank Silencer Figure DPF Regeneration System for DPF-Equipped Diesel Vehicle (1) Test vehicle specifications The specifications of the DPF-equipped diesel vehicle (in compliance with Euro III exhaust emission regulations) used in testing are presented in Table In this vehicle system, the exhaust gas temperature is elevated by post injection via a common rail fuel injection system and by an oxidation catalyst. In addition, continuous regeneration of DPF is realized by operating the FBC to lower the soot burn off temperature. 2

3 Table Specifications of DPF-Equipped Diesel Vehicle Engine displacement 2.2L Compression ratio 18.0 Maximum output 98 kw / 4000 rpm Maximum torque 314 Nm / 2000 rpm Fuel injection type a common rail fuel injection system Air supply type Turbo inter cooler Oxidation catalyst Present EGR Present Emissions level Compliance with Euro III exhaust emission regulations (2) Tested fuel The test vehicle was designed on the assumption the use of Euro III diesel fuel (350 ppm sulfur content), and the fuels given in Table were used in testing. Table Tested Fuel Properties (DPF-Equipped Diesel Vehicle Test) Item Fuel A Emissions test C, g / cm Kinematic C, mm 2 / s Sulfur content ppm 298 Distillation properties, C 10% 50% 90% Cetane number 57 Aromatics hydrocarbons content, vol % Monocyclic Bicyclic Tricyclic (3) Test methods Emissions tests were conducted in compliance with the EU test mode (ECE R83: ECE + EUDC) and the test mode (TRIAS ) designated as the emissions test method in Japan. (4) Results EU mode test measurements are given in Table and the mode test measurements appear in Table It was confirmed that emissions levels from the test vehicle satisfy Euro III regulations and that the PM emissions level was extremely low, around one-tenth of the Euro IV regulation value. In the test mode used in Japan, comparisons were made with long-term regulation and new short-term regulation values, and although PM, CO and THC values were satisfactory, the NOx value was high. 3

4 Table EU Mode Test Measurements ECE+EUDC Mode (g / km) CO THC NOx THC + NOx PM Traveling distance km Test vehicle Euro III regulations Euro IV regulations Table Mode Test Measurements Mode (g / km) CO THC NOx THC + NOx PM Traveling distance Test vehicle Long-term regulations Short-term regulations km Temporal changes in each emissions substance are depicted in Figure At approximately 500 km, CO, THC and PM were found to increase temporarily. In the test mode, fuel consumption, which was normally at an average of 14.7 km / l, worsened about 11 % to 13.1 km / l during regeneration. In this way, the DPF regeneration mode by post injection was entered. Data materials on the vehicle prepared by the maker indicate that regeneration by post injection should take place once every km, and regeneration was carried out accordingly. The vehicle was driven on the road for 700 to 1000 km, but emissions were not examined Regeneration Regeneration Traveling distance Traveling distance Regeneration Regeneration Traveling distance Traveling distance Figure Temporal Changes in Emissions From DPF-Equipped Diesel Vehicle (10-15 Mode Test) 4

5 2.1.2 Effect of Fuel Properties on Atomization One automotive measure for reducing the PM involves the use of a high-pressure injection pump, and among these, the common rail, high-pressure, fuel-injection pump, which enables completely free fuel injection, has become widespread. An investigation was made of the effect of fuel properties (e.g., density, kinematic viscosity) on injection time period, injection rate, spray structure (penetration force, spray angle, Sauter s mean diameter), etc. In the current fiscal year, the effect of kinematic viscosity on atomization was investigated. Spray measuring equipment is illustrated in Figure Figure Spray Measuring Equipment (1) Spray measuring equipment and fuel injection pump Atomization was observed using the spray measuring system shown in Figure For observation of atomization in a constant-volume vessel, room temperature and a pressure of 1.0 to 3.5 MPa were established in a nitrogen ambient. Used as fuel injection pump were the mechanical distributor injection pump and common rail, high-pressure injection pump. (2) Sample fuels In order to observe the effect of viscosity, four types of sample fuel were provided for testing with kinematic viscosity set within the range of 1.3 to 5.6 mm 2 / s. The properties of these fuels are given in Table Table Sample Fuel Properties (Spray Test) Item Fuel K (kerosene on market) Fuel L Fuel P Fuel HCG C, kg / m Kinematic C, mm 2 / s Bulk modulus, 103 Mpa Surface tension, mn / m

6 (3) Results Figure illustrates the effect of fuel properties on injection rate. With the mechanical distributor injection pump, the injection timing is delayed in conjunction with a drop in fuel kinematic viscosity; the time period for completion of injection is also prolonged. With the common rail, high-pressure injection pump, the injection rate pattern was unaffected, regardless of the kinematic viscosity of the fuel. An example of the effect of kinematic viscosity on atomization structure is presented in Figure With the common rail, high-pressure injection pump, as compared to the mechanical distributor injection pump, Sauter s mean diameter was smaller. And no effect from kinematic viscosity was manifested. From these findings it was determined that fuel properties do not have a large effect on atomization. The effect of fuel properties on emissions will be investigated in the future. Mechanical distributor injection pump Common rail, high-pressure injection pump Figure Effect on Injection Rate Figure Impact on Sauter s Mean Diameter 2.2 Effect of Fuel Properties on After-Treatment Device Effect of Fuel Properties on Emissions Before and After DPF Attachment to Sold Vehicles Each type of DPF attachment is being investigated from the standpoint of drastically reducing black smoke and PM from vehicles already sold. In the present R&D, an investigation was made of the effect of fuel properties before and after DPF attachment to vehicles already sold. Batch regenerative DPF and continuous regenerative DPF were mounted onto sold vehicles / engines that comply with 1989 regulations and short-term regulations, and the effect of fuel properties on PM reduction was investigated. Respecting continuous regenerative DPF, fleet tests were conducted with two tank lorries, and data were collected on exhaust gas temperature while the vehicle was traveling on the road and on differences in pressure before and after DPF. Table presents a matrix of DPF testing versus sold vehicle. 6

7 Table Matrix of DPF Testing for Sold Vehicles Vehicle test Engine test Fleet test Test vehicle / engine Vehicle A: TC,IDI Passenger car complying with 1989 regulations Vehicle B: NA,IDI Truck complying with short-term regulations Vehicle C: NA,IDI Small truck complying with short-term regulations Engine G: NA,IDI Truck complying with short-term regulations Engine H: NA,IDI Truck complying with 1994 regulations Vehicle I: NA,IDI Truck complying with 1992 regulation Vehicle J: NA,IDI Truck complying with 1996 regulation Batch DPF Continuous regeneration DPF Test fuel Impact of fuel properties given below Sulfur content T90 Aromatic content Poly aromatic hydrocarbons content Uses diesel fuel on the market (Sulfur content of 500 ppm or less) (1) Test vehicle and tested DPF (a) In the evaluation of the batch regeneration DPF (electric heater regeneration method), vehicle A (complying with 1989 regulations), vehicle C (complying with short-term regulations) and engine G (complying with short-term regulations) were used. (b) In the evaluation of the continuous regeneration DPF, engine H (complying with short-term regulations) was used, and in fleet tests two tank lorries were used. The SiC DPF was used for the batch regeneration DPF. For the continuous regeneration DPF, there is oxidation catalyst upstream, and the type in which catalyst is retained in the DPF was used. (2) Tested fuel The nine types of fuel shown in Table were prepared in order to determine the effect of fuel properties (sulfur content, T90, total aromatic content, poly aromatic hydrocarbons content). 7

8 Table Tested Fuel Properties (Sold Vehicle DPF Test) Fuel factors Sulfur content T90 Total aromatic Poly aromatic content hydrocarbons content Fuel code SH SL T90H T90L TAH TAL PAH1 PAH2 PAH3 C, g / cm Sulfur content mass ppm Distillation T90 C Aromatic hydrocarbons vol % Total aromatics Monocyclic aromatics Bicyclic aromatics Tricyclic aromatics (3) Test methods Vehicle testing was carried out in accordance with the test mode (TRIAS ), and engine testing in accordance with the 13 test mode (TRIAS ). In fleet testing, the operational method was not specified because the tests are conducted with tank lorries in actual service. (4) Results (a) Results of the batch regeneration DPF Vehicle A: Passenger car complying with 1989 regulations Vehicle C: Truck complying with short-term PM conversion rate, % Engine G: Engine for truck complying with short-term regulations PM conversion rate, % PM conversion rate, % Figure Effect of Fuel Properties on the PM 8

9 Shown in Figure are the effects on the PM of fuel properties before and after DPF in vehicle A, vehicle C and engine G. With a fall in T90, the PM drops a maximum of nearly 30 %, and by lowering total aromatic content by about 10 %, the PM drops nearly 20 %. The levels vary, however, with the vehicle and engine, and the effects are not always constant. Figure shows the PM reduction after attaching the DPF to vehicle A, in which the effect of fuel properties is large, and the effect of fuel properties. The PM drops 90 % or more after attaching the DPF, and there is almost no effect from fuel properties. Similar results were obtained with other vehicles and engines. It was confirmed that the DPF attachment is effective in reducing the PM, exhibiting greater effectiveness than that obtained by improving fuel properties. Figure PM Reduction by Attaching DPF (Vehicle A Results) (b) Results of the continuous regeneration DPF The PM reduction obtained by attaching continuous regeneration DPF are indicated in Figure Although the PM could be reduced drastically by combining low sulfur diesel fuel (50 ppm) with the continuous regeneration DPF, with diesel fuel at 500 ppm sulfur content, the PM increased irrespective of other fuel properties. In other words with 500 ppm diesel fuel, although soot content is lowered, the PM increases because of gains in sulfide and SOF content. In order to reduce the PM in the continuous regeneration DPF using catalyst, the sulfur content in diesel fuel must be lowered. 9

10 Figure PM Reduction by Attaching Continuous Regeneration DPF (Engine H Results) (c) Results of fleet test of the continuous regeneration DPF The continuous regeneration DPF was mounted on tank lorries, and fleet tests were carried out with diesel fuel on the market. The tank lorry operation pattern was as follows: 10 % on expressways, 90 % on regular roads, average vehicle speed at 30km / h and vehicle operation time at about 7 hours / day. In both vehicles used in the tests, the DPF function was lost after traveling about 8500 km and testing was then terminated. Figure illustrates the distribution in exhaust gas temperature. The frequency at which exhaust gas temperature reached 350 C or higher, as required for regeneration, was about 10 %, matching the percentage at which the vehicles were driven on expressways. Fluctuations in differential pressure are represented in Figure Maximum and minimum differential pressures both rise slowly with increases in traveling distance. No.9951 vehicle No.9257 vehicle Total frequency of 300 C or above Frequency, % Total frequency of 350 C or above Exhaust gas temperature, C Figure Frequencies of Exhaust Gas Temperatures 10

11 In view of the aforementioned, it is evident that in the conduct of the fleet tests, exhaust gas temperatures were inadequate for DPF regeneration, as were the time periods in which these temperatures were maintained. After traveling approximately 8,500 km, the emission of black smoke from DPF was noted, and it was inferred that DPF function had been lost. Consequently, in the course of the analytical investigation, a portion of the DPF was dissolved away. This loss is ascribed to the fact that the PM, which had slowly accumulated, was suddenly burnt and the DPF thermal resistance temperature was exceeded. This indicates that further investigations must be made of the DPF mountings on sold vehicles. After DPF mounting on 6/27, travel distance is 200 km. After DPF mounting on 7/6, travel distance is 1900 km. After DPF mounting on 7/11, travel distance is 3000 km. Back pressure KPa Back pressure KPa Back pressure KPa Figure Changes in Differential Pressure Before and After DPF Regeneration by the Continuous Regeneration DPF with Oxidation Catalyst As indicated above, in continuous regeneration DPF with oxidation catalyst, the sulfur content of diesel fuel should be reduced. On the other hand, it has been reported that, depending on the type of oxidation catalyst, the diesel fuel sulfur content can cause SO 2 to act catalytically, and the DPF can be regenerated at low temperature. Accordingly, an investigation was made of the DPF in which catalyst believed to have such effect is retained. (1) Test engine and tested DPF Specifications of the tested engine are given in Table The engine was equipped with EGR and oxidation catalyst in compliance with 1998 regulations, but the oxidation catalyst was removed for testing. Table Engine Specifications Engine format L Fiscal year of regulation FY 1998 Bore x stroke, mm Engine displacement, cc 2,184 No.of cylinders - Allocation L4 Combustion chamber format Vortex chamber Compression ratio 22.6 Maximum output, kw / rpm 69 / 4,000 Maximum torque, Nm / rpm 206 / 2,200 Supercharger Present EGR Present Fuel injection pump Distributor type Fuel injection initial pressure, MPa 14.7 After-treatment catalyst Oxidation catalyst (removed before testing) 11

12 Table Specifications of Tested DPF Substrate Carrier Precious metal SiC absent absent SiC SiO2 Pt SiC TiO2 Pt In the DPF provided for testing, as shown in Table 2.2-4, the substrate is silicon carbide (SiC), carriers are SiO 2 and TiO 2, and the precious metal is Pt. (2) Test fuel Test fuel properties are given in Table In the latest investigation, fuel A with approximately 500 ppm sulfur content (diesel fuel on the market) and fuel B with approximately 50 ppm were used because the objective was to confirm the effect of sulfur content in fuel on the PM regeneration. Table Tested Fuel Properties Test item A B Density (g / cm C) Flash point ( C) T10 (vol %) T50 (vol %) T90 (vol %) Kinematic viscosity (mm2 / C) Cetane value poly-aromatic Total (vol %) hydrocarbons by HPLC Monocyclic (vol %) Bicyclic (vol %) Tricyclic + (vol %) Sulfur content (mass ppm) Pour point ( C) Cold filter plugging point ( C) HFRR C) (3) Test method Engine operating conditions were as follows: the speed was constant at 2100 rpm, 60 % of the tested engine s maximum rpm, and load levels were set at 40 %, 60 % and 80 %. Tests were performed in the sequence: 40 %, 60 %, 80 %, 60 %, 40 %, and at each steps, operations lasted for 30 minutes, including the time it took for the engine to stabilize after changing the conditions. (4) Results The results of the DPF without catalyst and of DPF with catalyst (Pt / TiO 2 ) are given in Figure and Figure 2.2-7, respectively. In the figures, the upper levels denote temperature and differential pressure, and the lower level represents emissions. 12

13 Figure DPF Without Catalyst (The 50 ppm Sulfur Content in Tested Fuel) Figure DPF With Catalyst (Pt / TiO 2 ) (The 50 ppm Sulfur Content in Tested Fuel) In the case of the DPF without catalyst, the DPF differential pressure does not decline, but with DPF retaining Pt / TiO 2, a drop in differential pressure was noted at step 3 and the effectiveness of precious metal was confirmed. Figure depicts the effect of sulfur content. At 60 % load, differential pressure was found to drop more with 500 ppm sulfur content than 50 ppm, but the effect of sulfur content was not confirmed. Figure DPF With Catalyst (Pt / TiO 2 ) (The 500 ppm Sulfur Content in Tested Fuel) 13

14 2.2.3 Investigation of Fuel Borne Catalyst (FBC) By dosing the fuel borne catalyst (FBC) to the fuel, the soot burn off temperature can be lowered, and this phenomena was investigated as a means of support for the DPF regeneration. It has already been mentioned that in the PSA Peugot-Citroen, a ceria type of FBC is used in the DPF system. In order to clarify the effect of the FBC, an investigation was conducted this fiscal year of another type of iron / strontium of FBC after mounting the SiC DPF in engine that complies with 1989 regulations. (1) Tested FBC and fuel The iron / strontium of FBC provided for testing was dosed at 20 wt ppm, the concentration recommended by the maker as additive to diesel fuel on the market. Major properties of the tested fuel are given in Table Table Regeneration Temperature of DPF and Dosed Concentartion of FBC C, g / cm Distillation properties IBP / 10 % / C 50 % / 90 % / EP Kinematic C, mm 2 / s Total aromatic hydrocarbons content, vol % 23.7 Sulfur content, mass ppm 362 (2) Tested DPF and test conditions The wall-flow type of DPF made of SiC substrate with electric heater was mounted onto a small diesel engine (IDI / supercharge) that complies with 1989 regulations, and used for testing. The test was performed at a constant speed, and loads were modified in order to change exhaust gas temperature. Differential pressure, exhaust gas temperature, and each exhaust emissions were measured before and after the DPF, and the DPF regeneration status was evaluated. (3) Results Results of evaluations of iron / strontium of FBC as compared to the absence of the FBC are shown in Figure and Figure , respectively. 14

15 Differential Pressure (Kpa) Without FBC With FBC Differential Pressure (Kpa) Without FBC With FBC Time Elapsed (sec) Time Elapsed (sec) DPF Inlet Temperature ( C) Without FBC With FBC DPF Inlet Temperature ( C) Without FBC With FBC Figure Time Elapsed (sec) FBC Evaluation Results (Low-speed Condition: 1400 rpm, 80 % Load) Time Elapsed (sec) Figure FBC Evaluation Results (High-speed Condition: 2800 rpm, 80 % Load) At low speeds, the DPF inlet exhaust gas temperature is slightly less than 300 C, and the DPF differential pressure rises gently in the case of FBC presence in fuel as compared to the absence of FBC. At high speeds, on the other hand, the DPF inlet exhaust gas temperature reaches approximately 480 C and clear drop in differential pressure can be seen in fuel with FBC presence. It is suspected that at high speeds, the FBC causes the soot burn off temperature to decline and there is a corresponding drop in differential pressure, thereby manifesting a supportive effect. This effect is scheduled to be confirmed by such means as the measurement of DPF weight. 2.3 Analysis Methods of PM Substance With respect to PM substance that are not yet regulated, methods of analysis must be investigated and steps taken to accumulate data, since such substances could become regulated in the future because of their effects on health. In the current fiscal year, investigations were made for improving accuracy in the measurement of PM at low concentrations, and accuracy in the analysis of poly aromatic hydrocarbons and nitro poly aromatic hydrocarbons, and for determining methods of measuring PM particle size. This report discusses the results of an investigation made of factors effecting on the accuracy of analysis of PM composition in the case of attaching the DPF, as part of an investigation for improving accuracy in the measurement of the PM at low concentrations. 15

16 2.3.1 Improvement of accuracy in measurement of low-concentration PM The PM composition in the case of attaching the DPF was analyzed. The results for the alternate regeneration type of the DPF are shown in Table and the results for the continuous regeneration DPF appear in Table The sum of SOF, sulfate and moisture exceeded the PM magnitude, so that the calculated value of the soot becomes negative. The reasons for this were elucidated. Table Evaluation of Alternate Regeneration Type of the DPF Long-term regulation engine, D-13 mode, Fuel of 500 ppm sulfur content PM composition (%) Measurement values (µg) DPF SOF SO 4 H 2 0 SOOT PM SOF SO 4 H 2 0 SOOT present present absent Table Evaluation of the Continuous Regeneration DPF Long-term regulation engine, D-13 mode, Fuel of 500 ppm sulfur content PM composition (%) Measurement values (µg) DPF SOF SO 4 H 2 0 SOOT PM SOF SO 4 H 2 0 SOOT present present absent Note) SOOT = PM - (SOF + sulfate + moisture) The investigation focused on method of estimating SOF magnitude and method of calculating moisture volume. It was found that the SOF magnitude is estimated excessively (Table 2.3-3) because when SOF is extracted, the filter paper itself diminishes about 90 µg (0.047 wt % at filter paper standard) on average, and when the continuous regeneration DPF is attached, the moisture volume is also estimated in excess of its actual volume by the conventional calculation method (sulfate magnitude x 1.3) (Figure 2.3-1). Table Changes in Filter Paper Weight During SOF Extraction Filter paper Before SOF extraction processing (mg) After SOF extraction processing (mg) Change in weight (mg) Percentage decline (%) A B C D Average

17 With continuous regeneration DPF Moisture volume Without DPF Sulfate volume Figure Correlation Between Sulfate and Moisture Volumes Based on these findings, the PM composition was corrected and / or recalculated as follows. <SOF magnitude correction method> [SOF magnitude] = [Decline in extraction of PM-collecting filter paper] [Decline in filter paper] [Decline in filter paper] = [Weight of filter paper used] x / 100 * 0.047; percentage reduction (%) in weight of filter paper itself upon SOF extraction Note) Applied for both DPF alternate regeneration format and continuous regeneration format. <Moisture volume calculation method> [Moisture volume] = x [Sulfate magnitude] Note) Applied for continuous regeneration DPF only. As a result, it became possible to represent all compositions for both alternate regeneration type of the DPF and the continuous regeneration DPF with positive numbers (Tables 2.3-4, 5). It was discovered that the main reason soot assumes a negative value is that with alternate regeneration type of the DPF, the SOF magnitude is estimated to excess because of a decline in the magnitude of filter paper upon the SOF extraction. With the continuous regeneration DPF, it was found that the moisture volume is estimated in excess by means of the conventional calculation method. 17

18 Table Correction - Recalculation Results (Alternate Regeneration DPF) PM composition (%) Long-term regulation engine, D-13 mode, Fuel of 500 ppm sulfur content Measurement values (µg) SOF SO 4 H 2 0 SOOT PM SOF SO 4 H 2 0 SOOT Before correction After correction Note) Figures in bold are corrected SOF volumes Table Correction - Recalculation Results (Continuous Regeneration DPF) Long-term regulation engine, D-13 mode, Fuel of 500 ppm sulfur content PM composition (%) Measurement values (µg) SOF SO 4 H 2 0 SOOT PM SOF SO 4 H 2 0 SOOT Before correction After correction Note 1) Figures in bold are corrected SOF volumes. Note 2) Slanted figures in bold denoted recalculated moisture volume. 3. Results of Empirical Research 3.1 Reduction of New Vehicle Emissions by Improving Fuel Properties Emissions Performance of the Latest DPF-Attached Diesel Vehicle The new DPF-equipped diesel vehicle sold in Europe fully satisfies the EuroIII exhaust emission regulations in Europe in its emissions performance. The PM is 0.003g / km, about one-tenth lower than the Euro IV regulation value of 0.025g / km. It was also confirmed that a DPF regeneration operating mode is entered into for several minutes each time the vehicle travels about 500 km. During regeneration, The CO, HC and PM worsen temporarily, but they soon return to normal emissions levels. This is ascribed to temporary post fuel injection due to DPF regeneration Effect of Fuel Properties on Atomization The effect of fuel properties (kinematic viscosity) on mechanical distributor injection pump and on common-rail, high-pressure injection pump was investigated. With the former, the injection timing is prolonged with a drop in the kinematic viscosity of the fuel; the injection completion time period is also prolonged. With the later, on the other hand, the injection rate pattern is unaffected regardless of the kinematic viscosity of the fuel. The effect of fuel kinematic viscosity on atomization structure was also investigated. With the common-rail, high-pressure injection pump, Sauter s mean diameter, which indicates fuel spray atomization, was small in comparison to the mechanical distributor injection pump. Kinematic viscosity was not found to have any effect on Sauter s mean diameter in either type of fuel injection pump. 18

19 3.2 Effect of Fuel Properties on After-Treatment Device Effect of Fuel Properties on Emissions Before and After DPF Attachment to Sold Vehicles An investigation was made of the effect of fuel properties (sulfur content, T90, aromatics, poly aromatic hydrocarbon content) on sold vehicles and engines and on emissions when the DPF has been attached. With a decrease in T90, a decline in PM of about 30 % at the maximum is noted, but it was indicated that this decline varies with the vehicle and / or engine. In the case of the DPF mounting, the PM exhibits a decline of 90 % or more irrespective of fuel properties. The DPF mounting showed greater effectiveness in reducing the PM than did changing the fuel properties. Attaching of the continuous regeneration DPF, combined with low-sulfur diesel fuel (50 ppm), produced a sharp decline in the PM. With diesel fuel having a 500 ppm sulfur content (current level), on the other hand, the PM increased irrespective of other fuel properties. This is due to an increase in sulfate, and it indicated that with the continuous regeneration DPF just examined, a low-sulfur (50 ppm) diesel fuel is required for lowering PM. Fleet testing was also carried out with the same type of DPF, and anomalies appeared in the DPF after the vehicle traveled about 8,500 km. In the DPF breakdown investigation, it was discovered that a portion of the DPF had been dissolved and lost. Data on exhaust gas temperature, differential pressure, etc., indicated that regeneration does not take place adequately; and it is suspected that the dissolution took place because the PM, which slowly accumulated, was burnt suddenly and the thermal resistance temperature of the DPF material was exceeded Regeneration by Continuous Regeneration DPF with Oxidation Catalyst It has been reported that, depending on the type of the DPF oxidation catalyst, diesel fuel sulfur content causes SO 2 to act catalytically, which is effective in PM burn off. Accordingly, the DPF retaining Pt / SiO 2 and Pt / TiO 2 catalysts, which are expected to demonstrate such effectiveness, was investigated in terms of regeneration effect. It was found that the regeneration effect is higher with Pt / TiO 2 catalyst retaining DPF than with Pt / SiO 2 catalyst. As for the effect of sulfur content on regeneration, although a drop in differential pressure was noted under some operating conditions, it was not enough to be confirmed as the effect of sulfur content Investigation of FBC An evaluation was made of FBC, which has the effect of lowering the PM burn off temperature by about 100 C. In the latest instance, iron / strontium type of the FBC was evaluated, and at low exhaust gas temperature and at low speed, the effectiveness of the FBC was slight. At high speed, on the other hand, the exhaust gas temperature reached approximately 480 C at the DPF inlet, and a drop in differential pressure was noted in fuel with the DPF. In this way it was verified that the FBC has a supportive effect. 19

20 3.3 Analysis Methods of PM Substance An investigation was made of measures for improving accuracy in the analysis of PM composition, which was found to be problematic when using the continuous regeneration DPF. The reasons that the soot content becomes a negative value were determined as follows: when the SOF is extracted, the filter paper itself diminishes about 90 µg on average, and the SOF magnitude is estimated excessively. Moreover, when the continuous regeneration DPF is attached, the moisture volume is also estimated in excess of its actual volume by the conventional calculation method (sulfate magnitude 1.3). Accordingly, the correction formula for SOF magnitude and the moisture content calculation method were revised in consideration of the decline in filter paper so that the soot magnitude can be expressed as a positive number. 4. Synopsis In the Fourth Report of the Central Council for Environment Control in November 2000, it was recommended that the new long-term regulations on diesel emissions, which were introduced in the Third Report as being scheduled for implementation from 2007, should be brought forward to In developing automotive technology to meet these new long-term emissions standards, the introduction of after-treatment devices will be indispensable, and in order to promote introduction of such technology, it was decided that provision of 50 ppm low sulfur light oil will begin from Since emissions regulations have been made stricter and compliance timetables have been revised, the development of technology for reducing diesel emissions now requires urgent attention. The course of development of such technology is complex, but new engine technologies, including after-treatment systems, and low-sulfur diesel fuel will have to be obtained rapidly and performances will have to be evaluated. The effect levels of fuel properties will also have to be investigated. Copyright 2001 Petroleum Energy Center all rights reserved. 20