J. C. Dent

Phenomenological Diesel Combustion Model Including Smoke and NO Emission

An existing phenomenological model for combustion in quiescent and swirl assisted direct injection diesel engines developed by the authors has been extended to incorporate sub-models for exhaust smoke and nitrogen oxide emissions, based on published mechanisms for the formation of these two pollutants. Prediction of exhaust smoke and NO emission over a range of engine operating conditions including the effects of exhaust gas recirculation, has been undertaken for two quiescent and one swirl assisted engine. The predictions show well the general trend in emissions behaviour when compared with experiment, giving the possibility of using the model (with some calibration) for parametric studies.

Particle image velocimetry measurements of in-cylinder flow in a multi-valve internal combustion engine

Particle image velocimetry (PIV) has been used here to characterize the formation and breakdown of barrel swirl or tumble in a production geometry, four-stroke, four-valve motored optical internal combustion (IC) engine. The engine was motored at 1000 r/min at wide open throttle. Double exposed images were recorded from a plane parallel to the cylinder axis which passed through the centre-lines of an inlet and exhaust valve. Particle image velocimetry images from a range of crank angles between inlet valve closure and the ignition point were interrogated by digital autocorrelation to give two-dimensional maps of instantaneous velocity. The in-cylinder flow is characterized by the formation of an ordered barrel swirl or tumbling vortex, which is shown to persist throughout the majority of the compression stroke with maximum velocities of the order of three times the mean piston speed and a high velocity bulk flow at the time of ignition near the spark plug. With respect to the PIV technique itself, image labelling and cross correlation are considered essential to improve measurement dynamic range, valid data rate and tolerance to velocity gradients in the turbulent flows encountered near top dead centre (TDC).

Full‐field IC engine flow measurement using particle image velocimetry

Particle image velocimetry (PIV) has been used to study the in-cylinder flow within a single-cylinder optical spark ignition engine. The engine had a standard four-valve pentroof cylinder head geometry, a compression ratio of 10.5:1, and was motored at a crank speed of 1000 rpm. Double exposed PIV images were recorded from a range of vertical and horizontal measurement planes within the engines glass cylinder. The images were interrogated using digital autocorrelation to give maps of two-dimensional instantaneous velocity. Successful PIV measure- ments have also been made under firing conditions in the unburned gas ahead of the flame front, with the engine being skip-fired using a propane/air mixture. The use of PIV for the characterization of realistic in-cylinder flow fields under a variety of inhospitable conditions has therefore been demonstrated. Limitations in the current technique are briefly discussed and methods for overcoming these limitations are described.

Particle image velocimetry analysis of IC engine in-cylinder flows

Abstract This paper discusses the use of particle image velocimetry for measuring in-cylinder flows in multi-valve IC engines. The techniques and their limitations are discussed with special reference to the study of large-scale flow structures in a four valve optical IC engine exhibiting significant barrel swirl. Examples of velocity vector maps derived by digital autocorrelation are presented for a range of crank angles through the induction and compression strokes from both horizontal and vertical measurement planes. The evident strengths and limitations of the current technique for in-cylinder applications are discussed with respect to spatial resolution, velocity gradients and dynamic range. Recent developments for overcoming the limitations are also reviewed.

Diesel Engine Modelling Under Steady and Transient Conditions Using a Transputer Based Concurrent Computer

The work presented describes the development of an interactive model to simulate a direct injection diesel engine under both steady and transient conditions, based on the application of concurrent process computing methods. Starting with the modelling of the engine under steady operating conditions, in which induction, injection, air entrainment, fuel air mixing, combustion, emission and mechanical friction processes are considered, the fuel pump, governor, engine crankshaft and external load dynamics are also investigated to model the transient behaviour of the engine and its associated load. [Continues.]

Modelling the Origins of Combustion Noise in the Indirect Injection Diesel Engine

The Computational Fluid Dynamics (CFD) Code KIVA II has been applied to model combustion pressure oscillations in the Indirect Injection Diesel Engine. These oscillations are attenuated and transmitted by the engine structure to the surroundings as noise. The computational model was used to evaluate changes in design and operating characteristics of an engine, and the effect of these on the intensity of gas pressure oscillation. The results in general corroborate the trends of published experimental measurements of combustion noise. A 40% increase in grid resolution showed minor changes in the magnitude of cylinder pressure oscillation and approximately 0.5{degree} crank angle phase advance in the oscillation cycle compared with the grid used for the results presented here. 18 refs., 18 figs.