Combustion Engine Exhaust Systems Research Articles

Low-temperature cordierite ceramics with porous structure for thermal shock resistance products

This article shows the results of the study of low-temperature (1100−1150 °C) porous ceramics of cordierite composition. The technological manufacturing parameters, the features of the microstructural and phase composition of ceramics have been studied. A decrease in the sintering temperature is achieved by appending a part of components using eutectic glass of MgO–Al2O3–SiO2 pseudoternary system. The principle of reactive formation of the structure of the ceramic sample is implemented in the process of its low-temperature firing. The formation of α-cordierite occurs in the process of firing ceramics by means of intensive interaction between eutectic glass components and crystalline fillers, as well as in the result of glass crystallization. By means of the thin layers of the glassy phase, cordierite crystals form a hard base with a branched system of interconnected open pores (30.0−31.3 %). The cordierite-phase crystals, forming the structure of ceramics, have a particle size ranging from 0.2 to 0.3 μm to 1.0−2.0 μm. The specific surface area of the porous cordierite ceramics is in the range of 4.2–4.7 m2/g. The developed cordierite ceramics is characterized by its low coefficient of linear temperature expansion (1.7–2.6)·10−6 °С−1, which determines its high thermal shock resistance (1000−1150°С). The ceramics may be used as filtering elements in high-temperature filtering units, as well as catalyst carriers in the exhaust systems of combustion engines for discharging the sooty component.

Investigation of surface interactions between volatile chromium species and ceramics

Stainless steels are often used in high temperature (≥500°C) applications such as solid oxide fuel cells (SOFCs), combustion engine exhaust systems, and in power/chemical plant process equipment. At high temperature and in oxidizing conditions, chromium containing oxides, such as chromia, may form protective surface layers on the underlying alloy. Reactive evaporation of chromium, however, may occur from the protective surface layers given these conditions, resulting in the formation of volatile chromium species such as CrO2(OH)2. These volatile chromium species may then interact with surrounding materials, potentially resulting in hazardous compound formation, or having detrimental effects on system performance, as in the case of SOFCs. To better understand the interaction of volatile chromium condensation/deposition on material substrates, volatile chromium species were generated from chromia powder at 500°C to 900°C and flowed past coupons of alumina and mica and quartz wool at temperatures ranging from 150°C to 900°C for 24‐ and 100‐hour exposures. The ceramic surfaces were characterized as a function of these exposures using X‐ray photoelectron spectroscopy (XPS). Analysis of Cr 2p3/2peak positions revealed the influence of temperature, material, and exposure time on the oxidation states of surface chromium compounds and extent of chromium deposition. Potential mechanisms are proposed to help explain the observed trends.

Concept of the exhaust system of combustion engines used in underground mining

Analyses the problems occurring in the exploitation combustion engines used in mining have been presented in article. Design solutions used at present to protect the intake and exhaust systems of internal combustion engines operated in underground hard coal mines have been also described. A new design concept of exhaust system have been presented.

Dynamic properties of contact thermometers for high temperatures

Temperature sensors used in exhaust systems of combustion engines have to measure enormous temperature differences within the shortest periods of time. This serves to protect the engine parts with respect to their temperature stability and to govern the energy efficient operation of the engine. Numerical calculations with the Finite Elements Method are used to estimate static-thermal measurement errors and dynamic characteristics primarily concerning medium specificity and construction of the temperature sensors. New test equipment requires comparing various thermometers under real conditions (high temperature steps and velocity). Prediction models are used to correct the dynamic behavior and to predict the fluid temperature faster accurately.