Abstract
The results of investigations focusing on knock combustion analysis of a hydrogen-fueled engine have been presented in the paper. Knock intensity was determined as the intensity of the in-cylinder combustion pressure pulsations (recorded with a sampling frequency of 100 kHz) and filtered through high-pass filtering with cut-off frequency of 3.5 kHz. The research was conducted on the CFR engine with a variable compression ratio ranging from 6 to 14. The research has shown a rapid increase in pressure pulsations amplitude was observed while the compression ratio was changed from 11 to 12. This was interpreted as a result of in-cylinder hydrogen-air mixture self-ignition at the end of the spark ignition controlled combustion. Supporting this observation the theorem of dual nature of hydrogen knock combustion was postulated. Intensity of the pressure pulsations that accompany normal combustion without hydrogen self-ignition was in an exponential correlation with the compression ratio, which directly translates into a similar correlation of the pulsations and temperature of hydrogen-air mixture at the moment of ignition.
Highlights
The basic disadvantage of fossil fuels in comparison with renewable fuels is their limited resources
Among the potential fuels that can be widely applied in the near future is hydrogen
The engine was fitted with a programmable ECU control module enabling the control and variability of the: – ignition angle, – throttle position, – phases and opening times of the hydrogen injector placed in the intake manifold
Summary
The basic disadvantage of fossil fuels in comparison with renewable fuels is their limited resources. Główną wadą wodoru jako paliwa silnikowego jest jego skłonność do generowania spalania stukowego. Spalanie stukowe jest niepożądanym przebiegiem spalania mieszanki paliwowo-powietrznej w silniku, ponieważ generuje intensywne pulsacje ciśnienia, które oddziaływują udarowo na łożyska układu tłokowo-korbowego i mogą wprawiać w. In literature (Das [1], Swain and others [2]) is characterized by RON (research octane number) with the value of 130 as a fuel of very good resistance to knock combustion. Das [1] oraz Swain i inni [2]) podaje się LOB (liczba oktanowa badawcza) na poziomie 130, charakteryzując wodór, z jednej strony, jako paliwo o bardzo dobrej odporności na spalanie stukowe. W literaturze podaje się wówczas, że odporność wodoru na stuk wyrażona za pomocą LO jest na poziomie około 70 [4, 5, 6]. Ich amplituda w porównaniu do pulsacji z niestabilnego spalania jest co najmniej o rząd większa
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