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RISS 인기검색어
- 검색키워드
- 저자 : Stefano Beccari (검색결과 2 건)
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Model-based optimization of injection strategies for SI engine gas injectors
Stefano Beccari,Emiliano Pipitone,Marco Cammalleri,Giuseppe Genchi 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.8
A mathematical model for the prediction of the mass injected by a gaseous fuel solenoid injector for spark ignition (SI) engines hasbeen realized and validated through experimental data by the authors in a recent work [1]. The gas injector has been studied with particularreference to the complex needle motion during the opening and closing phases. Such motion may significantly affect the amount ofinjected fuel. When the injector nozzle is fully open, the mass flow depends only on the upstream fluid pressure and temperature. Thisphenomenon creates a linear relationship between the injected fuel mass and the injection time (i.e. the duration of the injection pulse),thus enabling efficient control of the injected fuel mass by simply acting on the injection time. However, a part of the injector flow chartcharacterized by strong nonlinearities has been experimentally observed by the authors [1]. Such nonlinearities may seriously compromisethe air-fuel mixture quality control and thus increase both fuel consumption and pollutant emissions (SI engine catalytic conversionsystems have very low efficiency for non-stoichiometric mixtures). These nonlinearities arise by he injector outflow area variation causedby needle impacts and bounces during the transient phenomena, which occur in the opening and closing phases of the injector. In thiswork, the mathematical model previously developed by the authors has been employed to study and optimize two appropriate injectionstrategies to linearize the injector flow chart to the greatest extent. The first strategy relies on injection pulse interruption and has beenoriginally developed by the authors, whereas the second strategy is known in the automotive engine industry as the peak and hold injection. Both injection strategies have been optimized through minimum injection energy considerations and have been compared in termsof linearization effectiveness. Efficient linearization of the injector flow chart has been achieved with both injection strategies, and a similarincrease in injector operating range has been observed. The main advantage of the pulse interruption strategy lies on its ease of implementationon existing injection systems because it only requires a simple engine electronic control unit software update. Meanwhile,the peak and hold strategy reveals a substantial lack of robustness and requires expressly designed injectors and electronic components toperform the necessary voltage commutation.
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A mathematical model for the prediction of the injected mass diagram of a S.I. engine gas injector
Marco Cammalleri,Emiliano Pipitone,Stefano Beccari,Giuseppe Genchi 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.11
A mathematical model of gaseous fuel solenoid injector for spark ignition engine has been realized and validated through experimental data. The gas injector was studied with particular reference to the complex needle motion during the opening and closing phases, which strongly affects the amount of fuel injected. As is known, in fact, when the injector nozzle is widely open, the mass flow depends only on the fluid pressure and temperature upstream the injector: this allows one to control the injected fuel mass acting on the “injection time” (the period during which the injector solenoid is energized). This makes the correlation between the injected fuel mass and the injection time linear, except for the lower injection times, where we experimentally observed strong nonlinearities. These nonlinearities arise by the injector outflow area variation caused by the needle bounces due to impacts during the opening and closing transients [1] and may seriously compromise the mixture quality control, thus increasing both fuel consumption and pollutant emissions, above all because the S.I. catalytic conversion system has a very low efficiency for non-stoichiometric mixtures. Moreover, in recent works [2, 3] we tested the simultaneous combustion of a gaseous fuel ( compressed natural gas, CNG, or liquefied petroleum gas, LPG) and gasoline in a spark ignition engine obtaining great improvement both in engine efficiency and pollutant emissions with respect to pure gasoline operation mode; this third operating mode of bi-fuel engines, called “double fuel” combustion, requires small amounts of gaseous fuel, hence forcing the injectors to work in the non-monotonic zone of the injected mass diagram, where the control on air-fuel ratio is poor. Starting from these considerations we investigated the fuel injector dynamics with the aim to improve its performance in the low injection times range. The first part of this paper deals with the realization of a mathematical model for the prediction of both the needle motion and the injected mass for choked flow condition, while the second part presents the model calibration and validation, performed by means of experimental data obtained on the engine test bed of the internal combustion engine laboratory of the University of Palermo.
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