Paul N. Blumberg

Prediction of NO Formation in Spark-Ignited Engines—An Analysis of Methods of Control

Abstract Lavoie, Heywood and Keck (1970) have recently shown how one can calculate the amount of NO formed during the combustion and subsequent expansion stroke of an IC engine. In this paper we have applied the method of Lavoie el al. to a spark-ignited carburetted IC engine and have incorporated into the computer program the engine variables; fuel type, fuel air equivalence ratio, humidity content of inlet air, % exhaust gas recirculation, inlet manifold temperature, inlet manifold pressure, RPM, compression ratio, piston connecting rod to crank ratio, and duration and position of combustion in the cycle. In addition to NO, we calculate indicated mean effective pressure and indicated specific fuel consumption. Brake specific values are calculated from an empirical correlation. Calculated NO levels show good agreement with data in the literature for the effect of the variables of air-fuel ratio, manifold pressure, spark timing, and humidity. Control methods capable of reducing NO emissions to the 100 ppm...

Phenomenological models for reciprocating internal combustion engines

Abstract In the past 10–15 years there has been a substantial increase in mathematical modeling activity as it relates to improving the design and operation of reciprocating, internal combustion engines. Most of the previous work and a large part of todays efforts center about models which are “phenomenological” in nature. These models attempt to describe complex engine behavior in terms of separate, physically-based submodels of important identifiable phenomena. Typically, they have been built around the First Law of Thermodynamics and involve no explicit spatial dependence. This approach is to be contrasted to the more recent, “detailed” or large scale approach in which the governing conservation equations are solved numerically in either one, two or three dimensions. In the latter approach, the important phenomena should emerge from the rigorous, detailed solution. Given the growing interest in modeling and in the detailed, large scale approach in particular, we have conducted a state-of-the-art review of phenomenological modeling capability to serve as a baseline for future work, be it of a phenomenological or detailed type. For conventional SI engines, stratified charge engines and diesel powerplants we have attempted to indicate those areas in which the phenomenological approach has been or could be successful and those areas in which detailed computations would be of greatest benefit. It is our general conclusion that detailed computations can be most helpful for guiding the development of more sophisticated phenomenological models which can then be used for extensive parametric investigations.

A Fundamental Model for Predicting Fuel Consumption, NOx and HC Emissions of the Conventional Spark-Ignited Engine

Abstract A model of the four-stroke S.I. engine cycle has been developed which predicts fuel consumption, NOx and HC emissions as a function of engine design and operating conditions. The model is primarily thermodynamic in nature containing no formal spatial dependence. The major new features of the model are: first, a treatment of heat transfer which confines heat losses to a boundary layer region surrounding a central adiabatic core; second, an integral boundary-layer analysis of in-cylinder burnup of quenched hydrocarbons; and third, a calculation of exhaust port HC oxidation which considers the temperature history of each element of gas leaving the cylinder. The main adjustable parameters of the model relate to the rate of heat transfer and the ratio of the two-plate quench to the single-wall thickness. An extensive comparison of model predictions with experimental CFR engine data is presented. The results show excellent agreement between predicted and experimental fuel consumption and NOx emissions....

Nitric Oxide Emissions From Stratified Charge Engines: Prediction and Control

Abstract A model is developed for calculating NO emissions for stratified charge engines in which the fuel is completely vaporized prior to combustion. The validity of the model is limited to single chamber geometry as it does not treat bulk gas motion typical of prechamber or divided chamber designs. The parameters of the model are fuel type, humidity of inlet air, overall equivalence ratio, stratification function, per cent EGR, intake manifold pressure, intake manifold temperature, compression ratio, piston connecting rod to crank radius ratio, RPM, and position and duration of combustion in the cycle. Stratification in which the first elements to burn are rich and the last elements to burn are lean is most effective relative to a uniform air-fuel mixture at overall air-fuel ratios near stoichiometric. Under these conditions almost all elements in the uniform charge are being “replaced” by elements of lesser NO-producing air-fuel ratios. On the overall rich side smaller reductions in NO level are possi...

Measurements of NO Emissions From a Stratified Charge Engine: Comparison of Theory and Experiment

Abstract Measurements of NO exhaust emissions have been made on a single-cylinder engine with and without stratification. The results were compared with predictions based on an existing computer model of Blumberg (1973). Combustion duration, a critical parameter of the model, was inferred from experimental pressure-time records for each condition studied. In premixed operation at low NO levels the post-flame Zeldovich kinetics, as used by Lavoie et al, (1970), could not account for the observed concentrations. The discrepancy was ascribed to flame-formed NO, and a correction to the chemical kinetics was made based on the measurements of Fenimore (1970). With this correction good qualitative agreement between theory and experiment was obtained for the premixed case. On the basis of these results the modified kinetics were also employed in the stratified charge calculations. For stratified operation, calculations were made with a number of assumed stratification functions and the results compared with exper...

Modeling of Compressed Air Hybrid Operation for a Heavy Duty Diesel Engine

Internal combustion engines can be modified to operate regenerative braking cycles by using compressed air power. This paper presents a particular air hybridization design from among many possible configurations. The engine cycles are enabled by a highly flexible engine valvetrain, which actuates engine valves to generate desired torque with optimal efficiency. A lumped parameter model is developed first to investigate the cylinder-tank mass and energy interaction based on thermodynamic relationships and engine piston kinematics. Special consideration is given to the engine valve timing and air flow. A high fidelity, detailed model using the commercially available GT-Power software is developed for a commercial 10.8 liter heavy-duty diesel engine with a 280 liter air tank in order to capture the effects of engine friction, heat transfer, gas dynamics, etc. The model is used to develop optimal valve timing for engine control. The established engine maps are incorporated into the ADVISOR vehicle simulation package to evaluate the potential fuel economy improvement for a refuse truck under a variety of driving cycles. Depending on the particular driving cycle, the simulation has shown a potential 4% – 18% fuel economy improvement over the truck equipped with the conventional baseline diesel engine.Copyright