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An optically-accessible research engine, image acquisition, and a control system are designed to acquire two-dimensional images of a pilot and main Diesel fuel sprays. This paper presents the engine-based apparatus, image acquisition techniques, and preliminary results of analysis performed upon interacting Diesel fuel sprays. The engine is a single-cylinder compression-ignition two-stroke with optically-accessible head mounted on a high speed CFR engine crankcase. It is equipped with a special dual-injection system for production of in-cylinder interacting sprays (main and pilot) with a high degree of adjustability with regard to the sprays fuel quantities and injection timings. The engine construction permits illumination of the sprays by a thin sheet of laser light from a pulsed Nd:YAG laser frequency doubled to operate at the visible wavelength of 532 nm.

To better understand the complex scavenging process in ported two-stroke engines, velocity measurements were taken at the exit of an intake port of a motoring and firing single-cylinder propane-fueled two-stroke engine by Laser Doppler Velocimetry (LDV). The radial velocity component was measured at the center of one port at engine speeds of 600, 900, and 1200 rpm. Cylinder pressure was also recorded for both motoring and firing cycles. When plotted versus crankangle, it was observed that the intake flow ensemble-averaged mean velocities have a characteristic two-end-peak profile with peaks occurring just after the piston exposes or is about to block the measurement volume. The two peaks occurred at approximately the same crankangle in both the motoring and firing engines. At 600 rpm the two velocity end peaks in the fired engine are larger than the corresponding motored values by a factor of 1.73 to 2.26.

An optically-accessible single-cylinder compression-ignition two-stroke research engine equipped with dual-injection system, image acquisition, and control system have been designed to acquire two-dimensional images of the pilot and main diesel fuel sprays. The engine construction permits illumination of the sprays by a thin sheet of laser light from a pulsed Nd:YAG laser frequency tripled to operate at the ultraviolet wavelength of 355 nm. The liquid fuel was decane with TMPD-naphthalene dopant dispersed in it. Upon ultraviolet excitation by the pulsed laser, liquid fuel regions fluoresced with a spectrum centered at the wavelength of 380 nm, while vapor regions fluoresced with a spectrum centered at 470 nm. This approach, called Exciplex technique, was applied to permit simultaneous acquisition of the liquid and vapor fuel regions in the cup-in- head geometry of the combustion chamber.

The net heat release rate and net heat release fraction for a spark-ignited (SI) single-cylinder two-stroke, production engine were analyzed using the one-zone model. Three different throttle positions and four engine speeds for each position were considered for this study. The method used required cylinder pressure and crank-angle data which were obtained from a pressure transducer mounted in the cylinder head and a shaft encoder connected to the crankshaft. An effective routine referred to as the overlap method was used to smooth undesirable oscillations on the heat release rate curves after investigation of several different approaches. Parameters such as maximum heat release rate, rapid burn angle, combustion duration, maximum heat release rate angle, imep, bmep, etc. were calculated and discussed.