A Comparative Study of Cycle Variability of Laser Plug Ignition vs Classical Spark Plug Ignition in Combustion Engines

The paper presents the results of the experimental research on the combustion process inside the cylinder of a large piston radial aircraft engine with dual spark plug ignition. The tests were carried out on the ASz-62IR-16X radial engine equipped with a double, electronically controlled ignition system with two spark plugs in each cylinder. The constant engine speed tests allowed for comparing the combustion processes with ignition carried out with different ignition advance angle offset between both spark plugs. In the test, the ignition advance angle for one spark plug was changed while leaving the ignition advance angle for the other spark plug. The tests performed for two engine operating points were to change the angle of the front spark plug and the rear spark plug. The analyses were based on the recorded pressure signal from one of the engine cylinders. It has been shown that the ignition advance angle offset significantly affects the combustion process. The obtained results indicate the leading role of the rear spark plug in initiating the combustion process. When ignition is carried out with a steady rear spark plug advance angle, the combustion process practically does not change when the ignition advance angle of the front spark plug changes. However, changing the rear spark plug advance angle at a constant front spark plug ignition advance angle significantly changes the combustion process.

Pre-chamber jet ignition is a promising way to improve fuel consumption of gasoline engine. A small volume passive pre-chamber was tested at a 1.5L turbocharged GDI engine. Combustion and emission characteristics of passive pre-chamber at low-speed WOT and part load were studied. Besides, the combustion stability of the passive pre-chamber at idle operation has also been studied. The results show that at 1500 r/min WOT, compared with the traditional spark ignition, the combustion phase of pre-chamber is advanced by 7.1°CA, the effective fuel consumption is reduced by 24 g/kW h, and the maximum pressure rise rate is increased by 0.09 MPa/°CA. The knock tendency can be relieved by pre-chamber ignition. At part load of 2000 r/min, pre-chamber ignition can enhance the combustion process and improve the combustion stability. The fuel consumption of pre-chamber ignition increases slightly at low load, but decreases significantly at high load. Compared with the traditional spark ignition, the NO x emissions of pre-chamber increase significantly, with a maximum increase of about 15%; the HC emissions decrease, and the highest decrease is about 36%. But there is no significant difference in CO emissions between pre-chamber ignition and spark plug ignition. The intake valve opening timing has a significant influence on the pre-chamber combustion stability at idle operation. With the delay of the pre-chamber intake valve opening timing, the CoV is reduced and can be kept within the CoV limit.

The use of laser energy to ignite gas and liquid based fuel-air mixtures has been the subject of a number of studies and laboratory experiments at a fundamental level over the past 30 years. The practical implementation of this laser application has still to be fully realized in a commercial automotive application. Laser Ignition (LI), as a replacement for Spark Ignition (SI) in the Internal Combustion (IC) engines of automotive vehicles, offers several potential advantages including extending lean burn capability, reducing the cyclic variants between combustion cycles and reducing the overall ignition package costs, weight and energy requirements. This paper reports on the current research being undertaken which examines the effects of engine combustion performance and stability when specific laser parameters (beam energy, minimum spot size and focal length/volume) are varied. A Q-switched Nd: YAG laser operating at the fundamental wavelength 1064 nm was used to ignite gasoline and air mixtures.

The influence of fatty acid methyl ester profiles on inter-cycle variability in a heavy duty compression ignition engine

Cylinder pressure reconstruction based on complex radial basis function networks from vibration and speed signals

The influence of fluorinated hydrocarbons on the combustion of gaseous mixtures in a closed vessel

Cold-start NOx emissions: Diesel and waste lubricating oil as a fuel additive

<div class="htmlview paragraph">The early flame kernel development period has a strong influence on the ultimate performance and emission characteristics of spark ignition engines. The fibre-optic instrumented spark plug, <span class="small-caps">FOSP</span>, is a tool used to characterise the early flame kernel development period without the need to modify production engines. Simultaneous in-cylinder pressure, fibre-optic spark plug and secondary ignition system voltage measurements have been made in the <span class="small-caps">GM</span> 2.8 L and the high swirl 3.1 L production engines modified to run on a single cylinder. The secondary ignition system voltages indicate that restrikes are occurring and that spark anemometry is a promising tool to extract information about the flow near the spark plug at the time of ignition. Further development of the technique is, however, required. In regard to <span class="small-caps">FOSP</span> data processing, it was found that i) the flame growth rate should be measured relative to the ignition point instead of the flame kernel centroid to account for the presence of restrikes, and ii) the <span class="small-caps">FOSP</span> measures a mass-weighted convection velocity. Normalisation of the measured convection velocity by the mean piston speed and unburned gas density at the time of ignition accounts for a large part of the convection velocity variations with engine speed and load; the so-normalised velocity was found to decay during the compression stroke. The initial flame growth rate was found to be strongly dependent on the convection velocity, and to increase during the compression stroke. Cyclic variations in the flame growth rate were found to correlate well with <span class="small-caps">LPP</span> and the 0-1% and 0-50% mass burn durations.</div>

Calorific value enhancement of fusel oil by moisture removal and its effect on the performance and combustion of a spark ignition engine

Mixture preparation is a key contributor to both the combustion and emissions of the automotive gasoline engine. The air-fuel ratio near the spark plug may have an effect on combustion characteristics, especially at low load, since it is related to flame development. Therefore, measurements of the cycle-resolved equivalence ratio near the spark plug are particularly important for a better understanding of their contribution to combustion and emissions. This paper describes how the in-cylinder equivalence ratio was determined from the measured hydrocarbon concentrations near the spark plug using a fast response flame ionization detector (FRFID). The procedures established were then applied to a limited range of engine operating conditions, and the cycle-resolved equivalence ratio near the spark plug was determined from the measured hydrocarbon concentration. The results showed that with premixed propane fuel the cyclic variation in equivalence ratio near the spark plug was quite small and corresponded to the overall equivalence ratio from the universal exhaust gas oxygen (UEGO) sensor signal. However, with gasoline fuel the equivalence ratio near the spark plug varied by up to 10 per cent and did not coincide with the UEGO sensor signal on a cyclic basis. The variation in equivalence ratio near the spark plug affected the heat release rate, which in turn affected the indicated mean effective pressure (i.m.e.p.). The equivalence ratio excursions and its effects during acceleration and deceleration are strongly related to the exhaust emissions, fuel economy and so on. With this in mind, the quantitative measurement method using the measured hydrocarbon concentrations was studied for detailed analysis during transient conditions. It was also observed that cyclic variation in the equivalence ratio near the spark plug might be one cause of cycle-by-cycle variation.

Grain and soybean dust explosion was investigated in order to determine the conditions that can cause an explosion to take place in a closed space such as in side a grain elevator, conveyor, miller and silo. The main parameters, which were investigated, were minimum ignition temperature, minimum explosible dust concentration, explosion pressure, dust particle size and moisture content. In all the materials and at all moisture contents, a concentration of about 1,000 g/m^3 was observed to give the maximum explosion pressure and maximum rate of pressure rise. The delayed time at this concentration was minimum. At any given dust particle size the ignition temperature was highest in rice husks followed by wheat, corn, milled rice and soybean in ascending order. However, in terms of maximum pressure and maximum rate of pressure rise, the order was from wheat, rice husks, soybean, corn to milled rice in descending order. It was observed that dust particle size played a major role on the explosibility of any dust material. Moisture content affected the ignition temperature and the maximum rate of pressure rise, but did not affect the maximum explosion pressure and delayed time of explosion.

Experimental investigation and Artificial Neural Network modelling of combustion pressure parameters of dual spark plug SI engine

Compressed natural gas (CNG) is an alternative fuel for internal combustion engines. The operation of the diesel engine in dual-fuel mode with CNG give rise to changes in the engine combustion process. These changes reflect on the engine noise emissions, because as the burn process is their main source. This article presents an experimental results related to the influence of CNG on the noise of a single-cylinder diesel engine operating on a dual-fuel mode. The variations in the engine noise are assessed by measuring the sound pressure level with four sound-level meters, with microphones positioned one meter from the engine. The in-cylinder pressure rise rate is also registered. A quantitative assessment of the sound pressure level and maximum in-cylinder pressure rise rate variation while the engine operating on diesel-CNG dual-fuel mode is made. The evaluation is performed by comparing the engine noise and the maximum in-cylinder pressure rise rate in function of: CNG mass ratio at constant engine speed and means effective pressure; mean effective pressure at constant engine speed and CNG mass ratio; engine speed at constant mean effective pressure and CNG mass ratio.

Based on the theoretical analyses, a set of experimental equipment, which consisting of a 20-litre closed spherical container, a gas distribution system, an ignition system, a heating system and a data acquisition system, was adopted to experimentally investigate the effects of the different environmental temperatures on the gas explosion pressure and the maximum pressure rise rate. The experimental results show that when the other conditions remain unchangeable, the maximum explosion pressure gradually decreases with the increase of the environmental temperature and its attenuation is linear with the reciprocal of the environmental temperature. With the increase of the environmental temperature, the chemical reaction rate quickens, and the time that the explosion pressure reaches its peak shortens. The maximum pressure rise rate of the gas explosion is nonlinear with the increase of the environmental temperature, but it basically remains unchanged in the 298-473 K environmental temperature range.

ABSTRACTIn the present article, the evolution of explosion pressure for 50%H2–50%CO syngas–air mixtures with a wide range of equivalence ratio in various turbulent ambience had been experimentally studied in a 28.73-L fan-stirred explosion vessel. Equivalence ratio varied from 0.4 to 3.0, and the turbulent intensity varied from 0 to 1.309 m/s. The results indicated that explosion indices (including maximum explosion pressure, explosion duration, and the maximum rate of pressure rise) were not monotonous to equivalence ratio, and the inflection equivalence ratio for different indices was different. The maximum explosion pressure was attained at the equivalence ratio of 1.2 for the reasons about maximum adiabatic flame temperature, the minimum explosion duration was attained at the equivalence ratio of 2.0 for the reasons about fastest laminar burning velocity, and the maximum rate of pressure rise was attained at the equivalence ratio of 1.6 for the competition effects of laminar burning velocity and adiabatic flame temperature. With the increase of turbulent intensity, the maximum explosion pressure and the maximum rate of pressure rise were raised albeit the growth tendencies were different for different ranges of equivalence ratio; the major reason to the growths was the heat transferred the wall during explosion had been reduced. Furthermore, with the increase of turbulent intensity, the value of deflagration index significantly rose even the values were higher than 30 MPa m/s for most cases in a weaker turbulent ambience; the results indicated that keeping the ambience quiescent is one better safety protection to syngas.