Automotive spark-ignited direct-injection gasoline engines

More documents

Recommendations

Info

540 F. Zhao et al. / Progress in Energy and Combustion Science 25 (1999) 437–562 • spark plug located slightly away from the center of the combustion chamber; • piston and bowl—deep-bowl-in-asymmetrical-crown; • intake port—one helical port with VVT-i system and SCV; • injector located under the straight intake port; • fuel injector—high-pressure swirl; two-stage injection; solid-cone spray; • common-rail fuel system using a variable fuel rail pressure from 8 to 13 MPa; • four-mode operation: stratified, semi-stratified, lean, and stoichiometric; • part-load mode—late injection at the air–fuel ratio of up to 50; • high-load mode—early injection; • torque transition between stratified-charge and homogeneous-charge operations controlled by two-stage injection and an electronic throttle control system; • NOx reduction—electronically controlled EGR, NOx storage-reduction catalyst, and standard three-way catalyst; • NO x storage catalyst regeneration frequency: once ever 50 s during lean operation; • octane requirement—91 RON; • power—107 kW at 6000 rpm; • torque—196 N m at 4400 rpm. As illustrated in Fig. 62, a special two-stage injection process is used for the transition between light-load and Fig. 108. Toyota GDI engine system [21]. heavy-load operation. This process creates a weakly stratified mixture in order to achieve a smooth transition of torque from ultra-lean operation to either lean or stoichiometric operation. The Toyota D-4 GDI engine operates using four operating regimes having distinctively different mixture strategies and/or distributions. The first is stratified-charge operation using an air–fuel ratio range of 25– 50. The vehicle operates in this ultra-lean zone under steady light-load, for road-loads of up to 100 km/h. The second operating regime is a transitional, semi-stratified zone with Fig. 109. Detailed SCV operating map of the Toyota GDI engine [21].
F. Zhao et al. / Progress in Energy and Combustion Science 25 (1999) 437–562 541 the air–fuel ratio ranging from 20 to 30. Within this zone, fuel is injected twice within each engine cycle, once during the intake stroke and once during the compression stroke. The third operating regime utilizes injection during the intake stroke to operate the engine in the homogeneous combustion mode using a lean air–fuel ratio of 15–23. The fourth regime is denoted as the stoichiometric power zone, and is similar to the third, except that the air–fuel ratio range is from 12 to 15. The common-rail fuel pressure is adjusted by the control system from 8 to 13 MPa in order to optimize the injection rate for short fuel pulse widths. It is also reported that another low-pressure fuel injector is employed in an auxiliary throttle body in order to enhance cold startability. The Toyota D-4 GDI engine also incorporates an electronic-throttle-control system that was reported to reduce the harshness of torque transitions, thus improving the driveability. The VVT-i technology is used to maximize torque in the low to mid-speed ranges, and to maximize power at high speed. The VVT-i varies intake valve opening and closing by 20. At low engine loads the intake valves are opened earlier, increasing the overlap between the intake and exhaust valves. This results in internal EGR, which was reported to increase the total EGR ratio while requiring less EGR from the external system. As a result, the VVT-i system also contributes to NOx emissions reduction. With the VVT-i system and an increase in the compression ratio to 10:1, about 10% more torque is obtained from the D-4 engine in the low to mid-rpm ranges than is obtainable with the conventional PFI engine. With the electrically controlled throttle valve, the manifold vacuum pressure at the throttle valve is halved from 67 kPa for a conventional PFI engine to 39 kPa at idle. At a steady 40 km/h speed, it is only 11 kPa, which is very close to a wide-open throttle manifold vacuum. The D-4 GDI engine, which is officially designated as the 3S-FSE, shares the basic dimensions of the conventional 3S- FE, dual-overhead-camshaft, four valves per cylinder, inline, four-cylinder engine that was first installed in the Japanese Corona Premio compact sedan. Two small converters, each with 0.5 L volume, are situated immediately downstream from the exhaust manifold. These catalysts have the function of keeping the exhaust temperature high enough for efficient operation of the 1.3 L underfloor catalytic converter. A lean-NOx catalyst that is designed for NOx storage and cleaning is used with the D-4 engine. This catalyst contains rhodium for storage and release, and platinum for cleaning, both on an alumina bed, and stores NOx during periods of lean-burn operation. The stored NOx is converted at intervals of 50 s during lean operation by utilizing very brief periods of stoichiometric operation. These required cleaning periods are less than one second, and degrade fuel economy by an estimated 2%. It is claimed that the emission levels of oxides of nitrogen are reduced by as much as 95% on the Japanese test cycle. The fuel economy of the D-4 engine, when utilized with a four-speed automatic transmission, is Fig. 110. The Nissan GDI combustion system [99]. reported to be about 30% better than that of the conventional PFI engine. For operation on the Japanese urban 10/15mode cycle, a fuel consumption of 17.4 km/l was achieved, as compared to 13 km/l for the conventional PFI engine. The vehicle acceleration was also reported to be improved by approximately 10%, reaching 100 km/h from a standstill in less than 10 s. 6.4. Nissan combustion system The Nissan GDI engine, NEODi (Nissan Ecology Oriented performance and Direct Injection), is designed with a centrally mounted spark plug; and with the injector located underneath the intake port and between the two intake valves [23–27,66,99,100,138,191,192,210,262– 266,339,340,377]. The combustion chamber layout, engine and SCV control maps and system diagram are shown in Figs. 110–112. The engine can operate in both the stratifiedcharge mode and the homogeneous-charge mode, and a 30% reduction in cold-start UBHC emissions relative to the baseline PFI engine was reported. The engine could be operated with stable combustion using a mixture leaner than an air– fuel ratio of 40, resulting in a 20% improvement in fuel economy when compared with a baseline PFI engine that operates with a stoichiometric mixture. The principal features of the Nissan prototype I4 GDI combustion system are summarized as follows: • four cylinders; • four-valve pentroof combustion chamber; • bore × stroke—82:5 × 86:0mm;
Page 1 and 2:
PERGAMON Automotive spark-ignited d
Page 3 and 4:
F. Zhao et al. / Progress in Energy
Page 5 and 6:
Page 7 and 8:
Page 9 and 10:
Page 11 and 12:
Page 13 and 14:
Page 16 and 17:
452 and investigated. A schematic r
Page 18 and 19:
454 F. Zhao et al. / Progress in En
Page 20 and 21:
Page 22 and 23:
Page 24 and 25:
Page 26 and 27:
Page 28 and 29:
Page 30 and 31:
Page 32 and 33:
Page 34 and 35:
470 3. Combustion chamber geometry
Page 36 and 37:
472 In general, a rotating flow str
Page 38 and 39:
Page 40 and 41:
Page 42 and 43:
Page 44 and 45:
Page 46 and 47:
Page 48 and 49:
Page 50 and 51:
Page 52 and 53:
Page 54 and 55: 490 F. Zhao et al. / Progress in En
Page 58 and 59: 494 ◦ reduced valve size; ◦ pos
Page 80 and 81: 516 was achieved for the unthrottle
Page 96 and 97: 532 because both the exhaust flow a
Page 100 and 101: 536 Many new mixture-preparation an
Page 108 and 109: 544 valve, with some of the fuel be
Page 110 and 111: 546 A motor/generator is attached t
Page 112 and 113: 548 • vertical, near-centrally mo
Page 114 and 115: 550 pre-chamber and the combustion
Page 116 and 117: 552 6.17. Orbital combustion system
Page 126: 562 F. Zhao et al. / Progress in En
show all

Automotive spark-ignited direct-injection gasoline engines

Create successful ePaper yourself

Delete template?

Save as template?