Меры по уменьшению стука в газовом двигателе внутреннего сгорания

Studies on the influence of applying various technologies for combustion knock reduction have been presented in the paper. Among others, investigation concerning the following: overexpanded cycle, variable valve timing, internal and exhaust gas recirculation, leaning the combustible mixture and cooling the incylinder charge were of the interest. The research works were focused on impact of these technologies on both knock intensity reduction, and engine performance and toxic emissions. Results presented in the paper were coming from experimental investigation based on incylinder combustion pressure data acquisition. Additionally, knock intensity calculation methods were discussed. They are based on incylinder combustion pressure pulsations. Combustion knock intensity expressed by the maximum peak of the in cylinder pressure pulsations shows a strong negative correlation with both the EGR ratio and relative equivalence ratio – lambda. With respect to a catalytic converter installed on the exhaust pipe line, applying EGR appears as better solution for knock reduction then leaning the combustible mixture because the catalytic converter needs stoichiometric mixture for effective NOx reduction. Furthermore, application of the overexpanded cycle to the hydrogen or coke gas fueled IC engine significantly reduces intensity of potential knock by 50 % in comparison to Otto cycle for all loads. Additionally, overexpanded cycle contributes to increase in engine thermal efficiency. Summing up, all the presented measures and technologies can be successfully implemented into practice in stationary engines as well as in traction engines, both of them working on either natural gas or gaseous renewable fuels

Меры по уменьшению стука в газовом двигателе внутреннего сгорания

Studies on the influence of applying various technologies for combustion knock reduction have been presented in the paper. Among others, investigation concerning the following: over-expanded cycle, variable valve timing, internal and exhaust gas recirculation, leaning the combustible mixture and cooling the in-cylinder charge were of the interest. The research works were focused on impact of these technologies on both knock intensity reduction, and engine performance and toxic emissions. Results presented in the paper were coming from experimental investigation based on in-cylinder combustion pressure data acquisition. Additionally, knock intensity calculation methods were discussed. They are based on incylinder combustion pressure pulsations. Combustion knock intensity expressed by the maximum peak of the incylinder pressure pulsations shows a strong negative correlation with both the EGR ratio and relative equivalence ratio – lambda. With respect to a catalytic converter installed on the exhaust pipe line, applying EGR appears as better solution for knock reduction then leaning the combustible mixture because the catalytic converter needs stoichiometric mixture for effective NOx reduction. Furthermore, application of the over-expanded cycle to the hydrogen or coke gas fueled IC engine significantly reduces intensity of potential knock by 50 % in comparison to Otto cycle for all loads. Additionally, over-expanded cycle contributes to increase in engine thermal efficiency. Summing up, all the presented measures and technologies can be successfully implemented into practice in stationary engines as well as in traction engines, both of them working on either natural gas or gaseous renewable fuels.В статье изучается влияние различных технологий на уменьшение детонации при сгорании. Среди рассматриваемых вопросов следует упомянуть следующие: сверхрасширенный цикл, регулируемые фазы газораспределения, внутренняя рециркуляция и рециркуляция отработанных газов, обеднение горючей смеси и охлаждение заряда в цилиндре. Исследования направлены на изучение влияния используемых технологий на снижение интенсивности детонации, вредных выбросов и работу двигателя. Результаты испытаний получены в ходе экспериментальных исследований, основанных на сборе данных о давлении сгорания в цилиндрах. Кроме того, изучались методы расчета интенсивности детонации. Эти методы основаны на пульсациях давления сгорания в цилиндрах. Интенсивность детонации сгорания, выраженная максимальным пиком пульсаций давления в цилиндре, показывает отрицательную корреляцию с отношением как рециркуляции отработанных газов, так и с отношением относительной эквивалентности – лямбда. Что касается каталитического нейтрализатора, установленного на линии выхлопной трубы, применение рециркуляции отработанных газов представляется лучшим решением для уменьшения детонации с последующим обеднением горючей смеси, поскольку каталитическому нейтрализатору требуется стехиометрическая смесь для эффективного подавления окислов азота. При этом применение чрезмерно расширенного цикла к двигателю внутреннего сгорания, работающему на водороде или коксовом газе, снижает интенсивность потенциальной детонации на 50 % по сравнению с циклом Отто при всех нагрузках. Кроме всего прочего, чрезмерно расширенный цикл способствует увеличению теплового коэффициента полезного действия двигателя. Обобщая результаты исследований, можно сказать, что все предложенные меры и технологии могут быть успешно реализованы на практике в стационарных двигателях, а также в тяговых двигателях, работающих на природном газе или газообразном возобновляемом топливе

Influence of the addition of LPG-reformate and H2 on an engine dually fuelled with LPG–diesel, –RME and –GTL Fuels

AbstractDual fuel compression ignition engine has been proposed as one approach to reduce diesel engine regulated emissions (NOX and Soot) and to also allow the utilisation of other non-traditional fuels in transportation, in order to improve fuel security and CO2 emissions. In an attempt to improve the combustion characteristics of the LPG–diesel dual fuelled engine the influence of the (a) hydrogen and reformate (H2 and CO) additions and (b) properties of the in-cylinder injected diesel fuel, in this case diesel, biodiesel and synthetic diesel fuel were investigated.Improvements on engine thermal efficiency and HC (including particular HC species) emissions with the reformate and further improvements on CO, soot and particulate matter with hydrogen with respect to LPG–diesel dual fuel combustion were obtained. However, an increase in NOX was obtained due to the high in-cylinder temperature as a result of the shorter advanced premixed combustion. Moreover, the RME’s oxygen content, different injection (i.e. different high bulk modulus) and combustion characteristics as a result of its properties modified the combustion process and hence produced even lower HC, CO, soot and PM emissions. On the other hand, the lower density of GTL has changed the diesel fuel injection and combustion characteristics in dual fuelling mode which resulted in the increased regulated (HC and CO) and unregulated emissions. However, LPG–GTL dual fuelling with reformate and H2 addition showed better smoke-NOX trade-off compared to that of ULSD and RME

Thermodynamic analysis of combustion events in the natural gas fuelled SI engine with VVT

The main aim of the research was to investigate influence of overlap of the natural gas fuelled spark ignited engine on the following parameters: Indicated Mean Effective Pressure (IMEP), heat rate release including combustion phases (ignition lag, main combustion phase). The content of the study includes results from processing in-cylinder pressure measurements, heat release rate analysis, combustion phases, and finally the conclusions. The tests were carried out on the test bed including the single cylinder research engine with a displacement volume of 550 cm3. The engine was equipped with independent cam phasors for both intake and exhaust valves, but for this investigation, the exhaust valve timing was fixed (the exhaust cam centre line was fixed at -95 crank angle (CA) deg before Top Dead Centre) and intake valve timing was changed (the intake cam centre line was varied from 90 to 150 CA deg after Top Dead Centre). The overlap was changed in the range from 85 to 25 CA deg. 8 tests series were performed, each singular series consisted of 300 consecutive engine combustion cycles. As observed, by varying the valve overlap it contributes to significant change in the peak combustion pressure, peak of heat release rate, and combustion phases. Summing up, variable valve timing affects compression and expansion strokes by changing polytropic indexes due to various amounts of exhaust residuals trapped in the cylinder. It affects not only engine volumetric efficiency but also the heat release rate and IMEP, so it does engine performance. Thus, variable valve timing can be considered as valuable tool that can be applied to the natural gas fuelled internal combustion engine

Hydrogen rich gases combustion in the IC engine

Experimental results of combusting three different syngases in an internal combustion (IC) spark ignition engine are presented in this paper. The syngases used for tests varied each from the other with hydrogen content, which was of 10,15 and 60%. Other combustible gases as CO and CH4 were also changed. Thus, the lower heating value of the syngases was of 2.7, 4.6 and 17.2 MJ/nm3, respectively. Combustion tests were performed at stoichiometric ratio of syngas-air mixture, with variable spark timing and constant compression ratio of 10. On the basis of in-cylinder combustion pressure histories the indicated mean effective pressure (IMEP) was computed and presented versus spark timing and vs location of the middle combustion phase expressed by the 50% of mass fraction burned (MFB). Additionally, the 0-10% MFB and 10-90% MFB were also determined. Furthermore, the paper contains theoretical determination of the three fuel quantities, which can affect combustion duration and heat release rate during burning the syngases in the IC engine. They are as follows: laminar flame speed, ignition delay and adiabatic flame temperature. Final results does not show satisfactory correlation between LFS computed at NTP and real combustion phasing. Furthermore, both long combustion duration and long 0-10% MFB leading to unstable combustion were observed for the syngas with the lowest LHV of 2.7 MJ/nm3

The effect of methanol-diesel combustion on performance and emissions of a direct injection diesel engine

The results of CFD modelling a dual fuel diesel engine powered with both methanol and diesel fuel is presented in the paper. Modelling was performed with 20 and a 50% energetic share of methanol in the entire dose. The analysis was conducted on both the thermodynamic parameters and exhaust toxicity of dual fuel engine. It was found that the various share of methanol influences the ignition delay of the combustion process and after start of main phase of combustion, the process occurs faster than in case of the diesel engine. It was found that the time of 10-90% burn of the fuel is much shorter than it is in the diesel engine. The dual fuel engine was characterized by higher indicated mean pressure in the whole range of diesel fuel injection timings. While analysing toxic exhaust emission from the dual fuel engine powered with methanol, it was found that the rate of NO formation was significantly higher than from the diesel engine. The combustion process in the dual fuel engine occurs more rapidly than in the conventional diesel engine, which contributes to form areas with high temperature, and in combination with presence of oxygen from the air and oxygen bonded in the methanol, promotes the NO formation. In the case of the dual fuel engine, it was found that soot emission was reduced. The engine running with diesel injection start at 8.5 deg before TDC, the soot emissions were more than twice lower in the dual fuel engine, while the emission of NO was much higher