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In this study, a new EGR control technique, based on the estimate of the oxygen concentration in the intake manifold, was firstly investigated through numerical simulation and then experimentally tested, both under steady state and transient conditions. The robustness of the new control technique was also tested and compared with that of the conventional EGR control technique by means of both numerical simulation and experimental tests. Substantial reductions of the NOx emissions under transient operating conditions were achieved, and useful knowledge for controlling the EGR flow rate more accurately was obtained.

An electronic instrument for the measurement of fuel consumption in reciprocating internal combustion engines for light aircraft has been designed, manufactured and tested. The operating principle of the measuring device is based on the simple, theoretically supported and experimentally verified observation that the fuel mass flow rate is almost exactly proportional to the product of the intake manifold air pressure “pc” and the engine revolution speed “n”. Therefore, only two sensors are needed, and no fuel pipe cutting is required for installation and operation. This feature represents a major point in favor of simplicity, reliability and safety. The aim of the instrument is to provide a fuel consumption indication which can be used during cruising. The instrument is not intended as a replacement for the usual on-board fuel level gauge, but can be used to integrate the flight information with the overall and instantaneous fuel consumption data.

The residual gas fraction prior to ignition at the vicinity of the spark plug in a single cylinder, two-valve spark ignition engine was measured with a fast-response flame ionization hydrocarbon detector. The technique in using such an instrument is reported. The measurements were made as a function of the intake manifold pressure, engine speed and intake/exhaust valve-overlap duration. Both the mean level of the residual fraction and the statistics of the cycle-to-cycle variations were obtained.

A detailed description of flow rate measurement technique for automotive exhaust is presented. The system consists of a sector field mass spectrometer for continuous analysis of helium concentration in the exhaust gas and a mass flow controller which injects pure helium at a constant rate into the intake manifold of an engine. The exhaust flow rate can be calculated by helium injection flow rate dividing by the concentration since the concentration value is a measure of the ratio of helium dilution taking place in the engine. The advantages of the technique consist of (1) no disturbance from strong pulsed flow present when an engine is idling, (2) easy time alignment with gas analyzers, and (3) measurement of dry based flow rate that can be directly multiplied by dry based gas concentration to obtain mass emission rate.

Diesel engines with their embedded control systems are becoming increasingly complex as the emission regulations tighten, especially concerning NOx pollutants. The combustion and emission formation processes are closely correlated to the intake manifold O2 concentration. Consequently, the performance of the engine controllers can be improved if a model-based or sensor-based estimation of the O2 concentration is available. The paper addresses the modeling of the O2 concentration in a turbocharged diesel engine. Dynamic models, compared to generally employed steady state maps, capture the dynamic effects occurring over transients, when the major deviations from the stationary maps are found. Dynamic models positively affect the control system making it more effective and, exploiting information coming from sensors, they provide a more robust prediction performance. Firstly, a Nonlinear Output Error model (NOE), with simulation focus, fed with four inputs is presented.

The liquid fuel entry into the cylinder and its subsequent behavior through the combustion cycle were observed by a high speed CCD camera in a transparent engine. The videos were taken with the engine firing under cold conditions in a simulated start-up process, at 1,000 RPM and intake manifold pressure of 0.5 bar. The variables examined were the injector geometry, injector type (normal and air-assisted), injection timing (open- and closed-valve injection), and injected air-to-fuel ratios. The visualization results show several important and unexpected features of the in-cylinder fuel behavior: 1) strip-atomization of the fuel film by the intake flow; 2) squeezing of fuel film between the intake valve and valve seat at valve closing to form large droplets; 3)deposition of liquid fuel as films distributed on the intake valve and head region. Some of the liquid fuel survives combustion into the next cycle.

An analysis method for characterizing fuel behavior during spark-ignition engine starting has been developed and applied to several sets of start-up data. The data sets were acquired from modern production vehicles during room temperature engine start-up. Two different engines, two control schemes, and two engine temperatures (cold and hot) were investigated. A cycle-by-cycle mass balance for the fuel was used to compare the amount of fuel injected with the amount burned or exhausted as unburned hydrocarbons. The difference was measured as “fuel unaccounted for”. The calculation for the amount of fuel burned used an energy release analysis of the cylinder pressure data. The results include an overview of starting behavior and a fuel accounting for each data set Overall, starting occurred quickly with combustion quality, manifold pressure, and engine speed beginning to stabilize by the seventh cycle, on average.