Analysis of Low and High Temperature Heat Release in Dual-Fuel RCCI Engine and its Relationship with Particle Emissions

This study presents the influence of low-temperature heat release (LTHR) and high-temperature heat release (HTHR) on the combustion and particle number characteristics of the RCCI engine. The study investigates the relationship between the amount of LTHR, HTHR, and particle number emission characteristics. In this study, gasoline and methanol are used as low reactivity fuel (LRF), and diesel is used as a high reactivity fuel (HRF). The LRF is injected into the intake manifold using a port-fuel injection (PFI) strategy, and HRF is directly injected into the cylinder using a direct injection strategy. A particle sizer is used to measure particle emission in size ranging from 5 to 1000 nm. Firstly, the LTHR and HTHR are analyzed for different diesel injection timing (SOI) for RCCI operation. Later, the variation of particle emissions with LTHR and HTHR is characterized. Additionally, empirical correlations are developed to understand the relation between the LTHR and HTHR with particle emission. Two-staged auto-ignition of charge has been observed in RCCI combustion. Results depict that LTHR varies with diesel injection timing and the phasing of HTHR depends on the amount and location of LTHR. Results also showed that HTHR and LTHR significantly influence the formation of particle number concentration in RCCI combustion. The developed empirical correlation depicts a good correlation between diesel SOI and the ratio of HTHR to LTHR to estimate total particle number concentration.

Density-functional-theory predictions of mechanical behaviour and thermal properties as well as experimental hardness of the Ga-bilayer Mo2Ga2C

Mo2Ga2C is a new MAX phase with a stacking Ga-bilayer as well as possible unusual properties. To understand this unique MAX phase structure and promote possible future applications, the structure, chemical bonding, and mechanical and thermodynamic properties of Mo2Ga2C were investigated by first-principles. Using the “bond stiffness” model, the strongest covalent bonding (1162 GPa) was formed between Mo and C atoms in Mo2Ga2C, while the weakest Ga-Ga (389 GPa) bonding was formed between two Ga-atomic layers, different from other typical MAX phases. The ratio of the bond stiffness of the weakest bond to the strongest bond (0.33) was lower than 1/2, indicating the high damage tolerance and fracture toughness of Mo2Ga2C, which was confirmed by indentation without any cracks. The high-temperature heat capacity and thermal expansion of Mo2Ga2C were calculated in the framework of quasi-harmonic approximation from 0 to 1300 K. Because of the metal-like electronic structure, the electronic excitation contribution became more significant with increasing temperature above 300 K.

The Calculation of Double Nonlinearity and Material Anisotropy Influence on the Temperature Distribution in the Cylinder Under High Temperature Heat Exchange

At the present stage of the development of technology, it is necessary to ensure the strength, reliability and durability of the structure that successfully functions under conditions of high-temperature heat exchange as maximum as possible. In this regard, graphite structural elements are widely used, and they are also applied for parts of space and aircraft, jet and rocket engines. The transversely isotropic graphite cylinder used in this work has a unique set of qualities that make it indispensable for problems in nuclear physics and power engineering; however, in the calculation of thermal engineering practice, it has not been studied enough, since it contains a large scatter of thermophysical characteristics for various grades of graphite. The aim of the study, including the basis of the developed method for solving boundary value problems of doubly nonlinear unsteady thermal conductivity, is to consider the effect of temperature dependences of the thermophysical characteristics of the material on temperature, zonal radiative-convective heat transfer and anisotropy on the distribution of temperature fields along the length, at the center and surface of a semi-infinite solid cylinder. The essence of this method is that the Goodman’s and Kirchhoff’s transformations are applied to the problem posed converted to a dimensionless form, then the relative temperature and functions from it, are expanded in the series of sines on the a priori interval, then the superposition principle is applied, after which the original setting is converted to a set of linearized problems with reduced thermophysical characteristics. Linear problems are solved by the method of integral transformations, which are summed up. The upper limit of the priori interval is determined from the condition that the relative temperature obtained from the solution of the problem Fo ® ¥ takes the value of the upper limit of the a priori interval. A large number of numerical calculations in the Matlab environment graphically show changes in the relative temperature on the axis and surface of the cylinder in a wide range of Fourier criteria. It is found that with an increase in the Fourier criterion, the character of heating changes qualitatively from the axis to the surface of the cylinder, both in terms of nonlinearities and anisotropy. For the case of double nonlinearity, the location of the temperature fields at different anisotropies in comparison with an isotropic material is shown graphically.

Cooling Temperature and Heat Transfer Coefficients in Cylindrical Heat Exchangers

The parameters behavior that characterize the process was carried out through an experimental investigation to obtain the cooling temperature, heat transfer coefficients and the heat flow in mineral coolers. The values of water temperature, water flow and mineral temperature were recorded at the inlet and outlet of the cylindrical cooler. Experiments were carried out with five values of the mass flow, keeping the cylinder revolutions constant. The calculation procedure for the system was obtained, in the mineral coolers the heat transfer by conduction, convection and evaporation predominates as a function of the cooling zone. A reduction in temperature is shown with increasing length, the lowest temperature values were obtained for a mass flow of 8 kg/s. The mineral outlet temperature should not exceed 200 oC, therefore it is recommended to work with the mass flow less than 10 kg/s that guarantees the cooling process.

Magnetic Method for Rapid Detection of Carburization Degree of Fe-Cr-Ni Series High-Temperature Heat-Resistant Alloy

In view of the carburization of Fe-Cr-Ni high-temperature heat-resistant alloys in the ethylene cracking furnace and the hydrogen conversion furnace, this paper implemented the GMRI-I carburizing detector to test the degree of carburization of 25Cr35NiNb+ microalloy inlet pipe and 35Cr45NiNb+ microalloy outlet pipe of the ethylene cracking furnace after service as well as the reinforced joint made of Incoloy 800H from the hydrogen-making reformer. In conjunction with the results of the low-power acid corrosion test, a rapid detection method for the degree of carburization was proposed. Based on the experimental results of the carburizing detector and the laboratory test data, the carburization degree test curve of the above three alloys based on the magnetic field strength has been established. The detection accuracy was circa. 5% and the error was ±10%, which is convenient for guiding the use and replacement of Fe-Cr-Ni high-temperature heat-resistant alloy materials for ethylene cracking furnace and hydrogen conversion furnace, thereby ensuring the safe and stable operation of the device.

Atomic layer deposition for rutile structure TiO2 thin films using a SnO2 seed layer and low temperature heat treatment

We study the rutile-TiO2 film deposition with a high-k value using a SnO2 seed layer and a low temperature heat treatment. Generally, heat treatment over 600 ℃ is required to obtain the rutile-TiO2 film. However, By using a SnO2 seed layer, we obtained rutile-TiO2 films with heat treatments as low as 400 ℃. The XPS analysis confirms that the SnO2 and TiO2 film were deposited. The XRD analysis showed that a heat treatment at 400 ℃ after depositing the SnO2 and TiO2 films was effective in obtaining the rutile-TiO2 film when the SnO2 film was thicker than 10nm. The TEM / EDX analysis show that no diffusion in the thin film between TiO2 and SnO2. The dielectric constant of the TiO2 film deposited on the SnO2 film (20 nm) was 68, which was more than twice as high as anatase TiO2 dielectric constant. The current density was 10-4A/cm2 at 0.7 V and this value confirmed that the leakage current was not affected by the SnO2 seed layer.

Waste Heat Recovery of Biomass Based Industrial Boilers by Using Stirling Engine

Industrial boilers by using biomass for electricity generation have received significant attention recent years. However, during the process, a significant fraction of thermal energy is often lost to the environment as flue gas. The exhaust flue gas heat loss which ranges from 150-180°C (423.15-453.15K) has led to discovery of importance of recovering the waste heat of the flue gas to overcome the reliance on fossil fuel. Stirling engine as an external combustion engine with high efficiencies and able to use any types of heat source is the best candidate to recover waste heat of the exhausted gas by converting it into power. Thus, in this study Stirling engine was introduced in order to evaluate the possibility of recovering waste heat from industrial boilers to produce power. For this reason, Computational Fluid Dynamic (CFD) simulation test was performed to design an initial computational model of Stirling engine for low temperature heat waste recovery. The CFD model was validated with the experiment model and shows 4.3% of deviation. The validated model then connected to a lower temperature. It shows that when the heat source is 400K, the work done by the engine is 8.4J compared to when heat source 773K the work done is 17.0 J. The computational model can be used to evaluate the performance of Stirling engine as waste heat recovery of biomass-based industrial boilers for low-grade temperature heat source.