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The instantaneous frictional torque (IFT) of the engine and the piston-ring assembly frictional force (PRAFF) were determined during cranking and starting of a direct injection single cylinder diesel engine. The measurements included the cylinder gas pressure, the instantaneous torque of the electric starter, the angular velocity of the crankshaft and the axial force on the connecting rod. The engine and piston friction were determined every crank angle degree for all the cycles from the time the starter was engaged to the time the engine reached the idling speed. The data was analyzed and a comparison was made between the friction in successive cycles.

The UBHC emissions during cold starting need to be controlled in order to meet the future stringent standards. This requires a better understanding of the characteristics of the time resolved UBHC signal measured by a high frequency FID and its phasing with respect to the valve events. The computer program supplied with the instrument and currently used to compute the phase shift has many uncertainties due to the unsteady nature of engine operation during starting. A new technique is developed to measure the in-situ phase shift of the UBHC signal under the transient thermodynamic and dynamic conditions of the engine. The UBHC concentration is measured at two locations in the exhaust manifold of one cylinder in a multicylinder port injected gasoline engine. The two locations are 77 mm apart. The downstream probe is positioned opposite to a solenoid-operated injector which delivers a gaseous jet of hydrocarbon-free nitrogen upon command.

An experimental and numerical study was carried out to simulate the diesel spray behavior during cold starting conditions inside two single-cylinder optically accessible engines. One is an AVL single-cylinder research diesel engine converted for optical access; the other is a TACOM/LABECO engine retrofitted with mirror-coupled endoscope access. The first engine is suitable for sophisticated optical diagnostics but is constrained to limited consecutive fuel injections or firings. The second one is located inside a micro-processor controlled cold room; therefore it can be operated under a wide range of practical engine conditions and is ideal for cycle-to-cycle variation study. The intake and blow-by flow rates are carefully measured in order to clearly define the operation condition. In addition to cylinder pressure measurement, the experiment used 16-mm high-speed movie photography to directly visualize the global structures of the sprays and ignition process.

An experimental method for determining the Instantaneous Frictional Torque (IFT) using pressure transducers on every cylinder and speed measurements at both ends of the crankshaft is presented. The speed variation measured at one end of the crankshaft is distorted by torsional vibrations making it difficult to establish a simple and direct correlation between the acting torque and measured speed. Using a lumped mass model of the crankshaft and modal analysis techniques, the contributions of the different natural modes to the motion along the crankshaft axis are determined. Based on this model a method was devised to combine speed measurements made at both ends of the crankshaft in such a way as to eliminate the influence of torsional vibrations and obtain the equivalent rigid body motion of the crankshaft. This motion, the loading torque and the gas pressure torque are utilized to determine the IFT.

Many problems can develop from the uncontrolled fuel injection during cranking and starting of diesel engines. Some of the problems are related to excessive wear as a result of the high peak pressures reached upon combustion after misfiring, the relatively low rotating speeds and the lack of formation of a lubricating oil film between the interacting surfaces. Another problem is the emission of high amounts of unburned hydrocarbons and white smoke. Experimental results are given for a single cylinder and a multicylinder diesel engine, for the instantaneous angular velocity and cylinder pressures from the starter-on point until the engine fires. The causes of misfiring during cranking are investigated. The role of the increased blow-by gases on the autoignition process at the low cranking speeds is analyzed both analytically and experimentally. The contribution of the instantaneous angular velocity at the time of injection, on the autoignition process is investigated.

An experimental study was carried out to visualize the spray and combustion inside an AVL single-cylinder research diesel engine converted for optical access. The injection system was a hydraulically-amplified electronically-controlled unit injector capable of high injection pressure up to 180 MPa and injection rate shaping. The injection characteristics were carefully characterized with injection rate meter and with spray visualization in high-pressure chamber. The intake air was supplied by a compressor and heated with a 40kW electrical heater to simulate turbocharged intake condition. In addition to injection and cylinder pressure measurements, the experiment used 16-mm high-speed movie photography to directly visualize the global structures of the sprays and ignition process. The results showed that optically accessible engines provide very useful information for studying the diesel combustion conditions, which also provided a very critical test for diesel combustion models.