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A study of the influence of dilution, attained by air excess, upon the dynamic stage of combustion - the nucleus of a work producing cycle - in a diesel engine, is reported as a sequel of SAE 2000-01-0203. While the latter has been restricted to variation in dilution obtained by bleeding air compressed by the supercharger, here the scope of engine tests was expanded by incorporating an additional stage of compression. Besides revealing the mechanism of the dynamic stage, the paper demonstrates that its effectiveness is a linear function of the air excess coefficient, irrespectively how it is attained.

An ultrahigh injection pressure, common rail fuel injection system was designed, fabricated, and evaluated. The result was a system suitable for high-power density diesel engine applications. The main advantages of the concept are a very short injection duration capability, high injection pressure independent of engine speed, a simplified electronic control valve, and good packaging flexibility. Two prototype injectors were developed. Tests were performed on an injector flow bench and in a single cylinder research engine. The first prototype delivered 320 mm3 within 2.5 milliseconds with a 2600 bar peak injection pressure. A conventional minisac nozzle was used. The second prototype employed a specially designed pintle nozzle producing a near-zero cone angle liquid jet impinging on a 9-mm cylindrical target centered on the piston bowl crown (OSKA-S system). The second prototype had the capability to deliver 316mm3 in 0.97ms.

The present study extends our previous methane flame chemistry to methane autoignition based on most recent shock-tube experiments. It results in a detailed mechanism that consists of 128 elementary reactions among 31 species and that can be applied to predicting methane autoinginition times for temperatures between 1000 K and 2000 K, pressures between 1 bar and 250 bar and equivalence ratios between 0.4 and 3. A 9-step short mechanism is derived from this detailed mechanism with the objective of predicting knock in dual-fuel engines for equivalence ratio between 0.5 and 1.5 with temperature ranging 800 to 1200 K and pressure from 50 to 150 bar.

Experimental results are reported on spray characterization of gasoline pintle injectors A and B; the former with swirl vanes while the latter without swirl vanes upstream the pintle seat. Injection system was common rail with accumulator unit injector and pressure fuel metering. Spray tip penetration length was measured by laser beam attenuation technique. Time-resolved droplet axial and radial velocity components and droplet diameter were measured at many probe positions in both axial and radial directions by a two-component phase Doppler particle analyzer (PDPA). The measurement covered detailed spray structures of both injectors under rail pressures ranged from 8 to 14 MPa and with fuel delivery from 11 to 42 mm3/inj for Injector A and from 4 to 28mm3/inj for Injector B. Correlations of droplet velocity and diameter with arrival time to the PDPA probe volume are discussed.

Hydraulically intensified medium pressure common rail (MPCR) electronic fuel injection systems are an attractive concept for heavy-duty diesel engine applications. They offer excellent packaging flexibility and thorough engine management system integration. Two different concepts were evaluated in this study. They are different in how the pressure generation and injection events are related. One used a direct principle, where the high-pressure generation and injection events occur simultaneously producing a near square injection rate profile. Another concept was based on an indirect principle, where potential energy (pressure) is first stored inside a hydraulic accumulator, and then released during injection, as a subsequent event. A falling rate shape is typically produced in this case. A unit pump, where the hydraulic intensifier is separated from the injector by a high-pressure line, and a unit injector design are considered for both concepts.

An electronically-controlled, two-stage high pressure diesel unit injector is the focus of a study of injection characteristics. The fourteenth order nonlinear mathematical model of the injector is developed and a computer simulation written. The simulation is verified by good agreement between predicted and measured accumulator pressure histories and fuel deliveries for fuel and water tests over a range of rail pressure settings. Stroboscopic flash photographic and dynamic laser attenuation measurements of spray penetration distance and spray cone angle are obtained for the injector operating at peak injection pressures of 80, 110 and 145 MPa. The experiments are performed with water injection into quiescent air at laboratory conditions. At the highest value of peak injection pressure of 145 MPa, the penetration length history exhibits a slope of approximately 250 m/s with a corresponding spray cone angle of 16°.