Research on Key Factors of Sealing Performance of Combined Sealing Ring

In this study, the mechanical properties of a combined seal ring under different loads were numerically calculated using ANSYS. The effect of the working pressure and pre-compression ratio of a rubber O-ring on the contact stress of the combined seal ring was studied. The influence of the wear ring’s chamfer, thickness, and width on the contact stress and contact force of the combined seal ring was analyzed. Studies have shown that it is particularly important to select a compression ratio that is suitable for the working conditions. Under the same conditions of working pressure and compression ratio, upon increasing the wear ring chamfer, the contact pressure is decreased due to the decreasing contact bandwidth between the wear ring and the cylinder wall. This has little effect on the contact stress of the combined seal ring as well as the contact force, while the width of the wear ring is proportional to the latter.

Design and Research of Carbon Deposition Device Based on Detecting and Cleaning Gasoline Engine Cylinder

When checking and cleaning whether there is carbon deposit in the cylinder of gasoline engine, it is often time-consuming and laborious, and the process is complicated. Once the disassembly and assembly is not in place, its service life will be affected. When cleaning with carburizing agent and cleaning agent, it is difficult to fully contact with the cylinder wall, so the cleaning effect is poor and it is easy to leave its chemical composition in the engine. In this paper, some common ways of engine cylinder cleaning are studied, and a device for detecting and cleaning carbon deposition in gasoline engine cylinder is designed. The purpose is to provide a new convenient, simple and practical method for detecting and cleaning carbon deposition in automobile engine cylinder in the current market.

Numerical study on conjugate convective thermal transport in an annular porous geometry

Buoyancy-driven convection in an annular space between two upright concentric cylinders having finite thickness of inner/outer cylinder is an essential physical structure exposing several practical applications. The current article reports the coupled conduction-convection transfer in an upright porous annular space and the buoyant convective stream and thermal transfer, associated thermal transport rates has been numerically investigated. In this analysis, the inner cylinder has fixed width and maintained at uniform high temperature, while the outer cylinder wall is preserved at uniform lower temperature. However, the lower & upper boundaries of annular region are presumed to be sealed and insulated. The Brinkman-extended Darcy formulation is implemented for modeling the stream in the porous medium. An implicit finite difference technique based on SLOR & ADI methods is adopted to resolve the governing equations. From the numerical predictions, it has been detected that the conductivity ratio & wall thickness has crucial role in controlling thermal transport through the annular space. The present work will have applications in electronic equipment, electric machinery, solar collectors, and lubrication systems.

AERODYNAMICS AND HEAT EXCHANGE OF SINGLE END TUBE DURING EXTERNAL FLOW

In Ukraine, the safety of modern thermal power plants depends on the reliable operation of the equipment installed on them. Unfortunately, the technical condition of the chimneys is not properly maintained. Of course, the modernization of basic equipment (boilers, switching to another type of fuel) leads to a decrease in the temperature of the exhaust gases. An important aspect to maintain the condition of the chimneys is to maintain the moisture of the exhaust gases. An important feature of the external flow of chimneys are large Reynolds numbers Re = wd/n, which reach 106 and more. In the thermal calculation only the average heat transfer coefficient on the outer surface of the pipe is usually determined, and the features of aerodynamics and local heat transfer due to the conicity of the pipe are not taken into account. The work is devoted to the study of aerodynamics and heat transfer in the air flow of a single conical chimney. The method of computer modeling with numerical integration of equations of motion and energy was used in the research. At the first stage, the single pipe with the uniform flow profile is considered. Further, the influence of the surrounding infrastructure on the aerodynamics and heat transfer of a single conical tube is studied. The single conical vertical pipe with 40 m height, 1.7 m diameter at the base and 0.85 m in the mouth was used for the calculation. The computer model was calculated in the ANSYS2020-R1 program. The model is developed in a homogeneous area with the air environment. In order to obtain reliable results, the study was conducted to obtain the optimal set of the grid parameters for the heat transfer conditions. The grids with parameters that affect the distance of the first node from the cylinder wall (options a, b, c, d) and the rate of increase in the size of the elements as they move away from the area of interest (Growth rate GR) were studied. The type of the cylindrical pipe with constant diameter of 1.7 m has been chosen to analyze the sensitivity and to check the grid. The turbulence model has been choosen as the following: RNG k-ε model which is common for the tasks of this class, the Enhanced Wall Function, the solution algorithm for the connection of the velocity pressure in stable flows Simplex. It is determined that in case if the distance between the first node from the cylinder wall and the area of interest (Growth rate GR) is more than 8 mm, instability and deviation of the obtained data from the values of the average coefficient of more than 20% appears. As a result of the research, the parameter grid area matching to the “2d” option of table 1 has been selected, i.e.: GR = 1.1, h = 8 mm. In the study of aerodynamics and heat transfer, the conical tube is conventionally divided into 22 sections (with 1 m height each). The case of uniform flow velocity in front of the pipe has been considered. As seen, the maximum value of the heat transfer coefficient is in the Zone(21-22). The research shows that oncoming flow velocity of 25 m/s causes the average value of heat transfer coefficient of the conical pipe 62.5 W/m2K, and 61.1 W/m2K according to the known formula . This indicates a small effect of taper on the average heat transfer of the entire pipe. In the calculations, three types of surrounding areas are considered: A - open coasts of seas, lakes and reservoirs, rural areas, including buildings less than 10 m high; B - urban areas, forests and other areas, evenly covered with obstacles higher than 10 m; C - urban areas with dense buildings with buildings higher than 25 m. Thus, the wind speed profiles for different types of terrain are nonlinear. The wind speed profile in front of the pipe (type of terrain) has a significant effect on the heat transfer coefficient. This confirms the need to take into account the type of terrain and the velocity profile in front of the pipe for local heat transfer.

Kinematics of steam film wetting while quenching cylindrical samples in thermal oils

The paper presents the determination of the velocity of the vapor front along the outer wall of a cylindrical specimen in the process of two-dimensional axisymmetric quenching of the samples in thermal oils. One thermal oil is Isorapid 277 HM heated to 40°C and the other thermal oil is Marquench 722 heated to 90°C. The experimental setup of the work consists of heating to a temperature of 850°C, then quenching three dimensionally different cylindrical probes. The dimensions of the probe were: ϕ25x100 ϕ50x150 and ϕ75x225 mm. All quenchings were done in strictly controlled conditions of the flow rate of the quenchant around the cylinder as well as maintaining the temperature of the quenchant within the maximum 40±2.5°C or 90d3°C, during the quenching of the samples. The velocity of movement of the steam front on the outer surface of the cylinder was determined from the time-measured values of temperatures at the marked points of each sample. The analysis of the steam front movement velocity along the cylinder wall starts from the moment the lower base of the probe touches the quenchant. During the process of immersing the test probe in the quenchant, in addition to measuring the temperatures in time, the time of lowering the probe to contact with the quenchant sample was also measured. The approximate average velocity of the vapor front was determined based on the indications of the lower and middle thermocouples located 1.5 mm below the outer surface of the cylinder wall. Based on the distance of one half the height of each probe and time, the velocity of the steam film movement or the kinematics of the steam film wetting was obtained. The obtained results were compared with the results of quenching in water and aqueous solutions of the same probes under the same strictly controlled conditions.

A Fundamental Thermodynamic Investigation of Compression Ratio Effects in Relation to Diesel Engine Size

In this study, a fundamental generalized thermodynamic model of internal combustion engines was applied to evaluate engine compression ratio effects principally in relation to engine size. Performance and efficiency metrics were investigated systematically. Further, cylinder wall temperature was varied across a range of cold start to stabilized operating temperatures. A very broad range of engine bore sizes and bore-to-stroke ratios were evaluated, representing small to large diesel engines in service. In general, it was observed that engine efficiency increases moderately with increasing compression ratio and bore size. Additionally, surface area-to-volume ratio is a critical metric when evaluating various size engines. This leads to greater relative heat transfer in the smaller bore engines with higher compression ratios. The sensitivity to heat losses is also much greater in the smaller engines. Smaller engines with higher compression ratios are expected to be most affected by cold starting conditions. Exhaust enthalpy is highest for larger bore engines with lower compression ratios, an important consideration for engine boosting. Higher convective heat transfer coefficients are also expected in smaller bore engines with higher compression ratios due to the higher operating pressures.

Numerical investigation of lagrangian coherent structures in steady rotation vortex shedding control

In this paper, vortex shedding and suppression are numerically investigated as autonomous and non-autonomous dynamical systems respectively. Lagrangian coherent structures (LCSs) are used as a numerical tool to analyze these systems. These structures are ridges of Finite time Lyapunov exponent (FTLE) which act as material surfaces that are transport barriers within the flow. Initially, the utility of LCSs is explored for revealing the coherent structures of these systems. Finally, an active flow control method, steady rotation is applied to the non-autonomous dynamical system with different speed ratios to mitigate vortex shedding magnitude. This will eventually turn the system into an autonomous system. Fixed saddle points, separation profiles essentially as unstable time variant manifolds attached to cylinder wall and evolution of other unstable manifolds with variant speed ratios are analyzed with reference to LCSs. It is revealed that speed ratio of 2.1 fully suppresses the von Karman vortex street at Reynolds number of 100 and system turns into an autonomous dynamical system with fixed saddle points and time-invariant manifolds.

Pressure Vessel Mechanical Design Case study for 10 kg/cm² Pressure and 179 C Temperature

Pressure vessel is a closed tube that holds pressure, both internal pressure and external pressure. This pressure vessel is designed to function as a reservoir for condensate or condensed water and convert it into steam or hot steam. This article discusses the design of a pressure vessel for a pressure of about 10 kg/cm² and a design temperature of 179oC. In the design of this pressure vessel, it includes determining the material to be used in the design, determining the allowable stress of each material used, determining the cylinder wall thickness, cylinder head or cover wall thickness, nozzle wall thickness, determining the maximum allowable working pressure limit. or maximum allowable working pressure and testing after the pressure vessel is finished, namely the hydrostatic test method. The design has been successfully carried out according to the provisions. Bejana tekan atau pressure vessel adalah suatu tabung tertutup penampung tekanan, baik tekanan dari dalam maupun tekanan dari luar bejana. Bejana tekan yang ini dirancang berfungsi sebagai penampung condensate atau air kondensasi dan mengubahnya menjadi steam atau uap panas. Pada artikel ini dibahas perancangan pressure vessel untuk tekanan sekitar 10 kg/cm² dan suhu rancang 179oC. Dalam perancangan bejana tekan ini meliputi pemilihan material yang akan digunakan dalam perancangan, menentukan tegangan yang diijinkan atau allowable stress dari setiap material yang digunakan, menentuan tebal dinding silinder, tebal dinding head atau penutup silinder, tebal dinding nozzle, menentuan batas tekanan kerja maksimum yang diijinkan atau maximum allowable working pressure dan pengujian setelah bejana tekan jadi yaitu dengan metode hydrostatic test. Dalam artikel ini perancangan secara numeris telah berhasil dilakukan dengan baik sesuai ketentuan.