Statistical and Continuous Wavelet Transformation Based Analysis of Combustion Instabilities in a Biodiesel fuelled Compression Ignition Engine

Experimental evaluation of cyclic variability or combustion instabilities of waste cooking oil biodiesel-diesel blends powered compression ignition engine is presented in this article. An advanced in-vehicle combustion analyzer armed with a piezoelectric pressure sensor was used for accurate measurements eradicating the experimental uncertainty. Cyclic variation in the combustion was investigated using the statistical and wavelet analysis method. Results of statistical methods and wavelet analysis were agreeing with each other towards self-validation. Statistical methods were used to calculate the mean and coefficient of variations, while the wavelet method has the potential to analyze the cyclic variation topography together with the intensity of variations in the engine combustion cycle, especially at low engine load conditions. Overall combustion analysis including wavelet analysis and statistical method indicates a more silent and smoother engine operation with biodiesel blending as it enhances combustion stability in unmodified diesel engines in comparison with conventional diesel fuel.

Use of Methane-Free Synthesis Gases as Fuel in an Spark Ignition Combustion Engine

The presented article deals with the use of methane-free synthesis gases in a spark-ignition internal combustion engine. The authors analyse the influence of seven synthesis gases on integral as well as internal parameters of the engine and make comparisons with operation on methane. The main combustible components of the synthesis gas are hydrogen and carbon monoxide and the remainder are inert gases (nitrogen and carbon dioxide). At the operating speed of the combustion engine of 1500 rpm, at which the cogeneration unit operates, in comparison with methane a decrease in power parameters was recorded in the range from 19 to 35%. The increase in the hourly fuel consumption was 6 to 8 times higher. Depending on the gas composition, the optimum start of ignition angle at full load ranged from 17 to 26 °CA BTDC. In terms of analysis of internal parameters, the cyclic variability of the pressure in the engine cylinder, which characterizes the stability of its operation, was in synthesis gases operation mostly at a lower level (from 3.6% to 6.9%) than in methane operation (6.8%). Due to the presence of hydrogen, the main combustion time interval of all synthesis gases has been shorter compared to methane. The presented results serve to better understand the setting of the waste gasification process so that the highest possible energy and economic recovery in the cogeneration unit is obtained.

CAN THE 14C PRODUCTION IN 1055 CE BE AFFECTED BY SN1054?

ABSTRACTAnnually resolved radiocarbon (14C) measurements on tree rings led to the discovery of abrupt variations in 14C production attributed to large solar flares. We present new results of annual and subannual 14C fluctuations in tree rings from a middle-latitude sequoia (California) and a high-latitude pine (Finland), analyzed for the period 1030–1080 CE, to trace a possible impact of the Crab supernova explosion, occurring during the Oort minimum of solar activity. Our results indicate an increase of Δ14C around 1054/55 CE, which we estimate is higher in magnitude than the cyclic variability due to solar activity at a 2σ significance level. The net signal appears to be synchronized in the studied locations. Several sources of this event are possible including γ-rays from the Crab supernova, an unusually weak solar minimum or a solar energetic particle incident. More data are needed to provide more insight into the origin of this 14C event.