Enlarged engine control complexity made the full-factorial steady-state testing approach extremely time consuming and hardly applicable under actual industry demands. Slow dynamic slope (SDS) method is one of many approaches with a potential for considerable testing time savings, with its own benefits and drawbacks. This paper puts in focus SDS approach and evaluates its applicability, potentials and accuracy for fast estimation of engine steady-state maps. The presented research is based on an extensive experiment conducted on a small passenger car compresion ignition engine. Being the method that uses quasi-stationary sweeping of the engine, SDS test cycle durations in the range from 120-600 seconds are used in order to test the method and draw conclusions on its applicability. It is shown that well shaped SDS testing cycle can provide a rather good estimate of the steady-state operating points very quickly, with a negligible or very small loss of accuracy. The analysis is conducted both on fast responding variables and those that are heavily influenced by process inertia. This led to some suggestions on how to form a criterion for the SDS gathered data quality evaluation and SDS testing cycle correction.
Engine control optimization, with its always growing complexity, is in permanent focus of engine researchers and developers all over the world. Automotive engines are dominantly used in dynamic conditions, but generally, steady-state operating points are used for building up mathematical models which are later subject to the numerical optimization. For this purpose, a large amount of steady-state regimes needs to be evaluated through experimental work at the engine test stand, which is an extremely time and funds consuming process. Consequently, the methodology for data gathering during engine dynamic excitation could lead to significant savings at the expense of acceptable data accuracy loss. The slow dynamic slope method starting from a stationary operating point was evaluated by several authors in the past. In this paper, slow dynamic slope method with exclusively transient excitation will be presented drawing attention to some of its advantages and drawbacks. The rate of change of engine load as a main control parameter during dynamic test is of great importance for the quality of the final data and for total test duration. In this regard, several tests of different duration were applied for fixed engine speed values to cover engine speedload usage domain. An approximation of stationary testing results obtained in this way could be used for evaluation of the map gradients and thus as a guideline for additional stationary tests based on design of experiment method.
A syngas-fueled engine work cycle simulation has been conducted in the AVL BOOST environment in order to gain some insights into the expected engine performance and efficiency parameters. The study also provides the energy balance that will dictate the design of engine coolant and exhaust gas heat recuperation systems. A turbocharged six-cylinder gas engine serves as the basis on which the numerical studies have been conducted. A Vibe-based heat release model, customized to take into account the effect of excess-air ratio and ignition timing variations on the combustion duration and MFB curve shape is used to predict the heat release rate. A simple methodology for determining the total engine displacement for a given fuel production rate is also presented. The resulting brake mean effective pressure and efficiency parameters are lower than on a comparable natural gas-fueled engine but syngas is still an interesting alternative, particularly for cogeneration units.
A dynamic programming optimization algorithm has been applied on a transit bus model in MATLAB in order to assess the fuel economy improvement potential by implementing a hydraulic hybrid powertrain system. The numerical model parameters have been calibrated using experimental data obtained on a Belgrade's public transport bus. This experiment also provided the representative driving cycle on which to conduct simulation analyses. Various functional parameters of a hydraulic hybrid system have been evaluated for obtaining the best possible fuel economy. Dynamic programming optimization runs have been completed for various hydraulic accumulator sizes, preload values and accumulator foam quantities. It has been shown that a fuel economy improvement of 28% can be achieved by implementing such a system.
This paper presents an unconventional approach in a fast estimation of the overall engine inertia based on engine testing under transient condition (acceleration and deceleration) with simultaneous in cylinder working process analysis and friction losses estimation. The presented procedure is based on a single slow dynamic slope full load engine speed sweep test which, coupled with a simple lumped-mass engine dynamometer model, provides correct overall engine inertia estimation. Compared with the more conventional approaches in deriving information on engine inertia, besides its speed and accuracy, presented procedure provides more in depth information on both engine's dynamic response and friction as a surplus.
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