Identifikace teploty v konstrukčních prvcích bezkontaktních těsnění pomocí Trefftz funkcí

Phenomena of the heat transfer in non-contacting face seals was described by partial differential equation of the second order and boundary conditions. In this way, the mathematical model was developed for the sealing rings. The distributions of temperature in the structural elements was obtained by the Trefftz method. It is a simple method of solving direct and inverse problems described by a homogeneous or an inhomogeneous partial differential equation. The main idea of the method is to determine functions satisfying a given differential equation (Trefftz functions) and to fit the linear combination of them to the governing boundary conditions.Jev přenosu tepla v bezkontaktních mechanických těsněních byl popsán parciální diferenciální rovnicí druhého řádu s okrajovými podmínkami. Tímto způsobem, byl vyvinut pro těsnicí kroužky matematický model. Distribuce teploty v konstrukčních prvcích byla získána metodou Trefftz. Jedná se o jednoduchý způsob řešení přímých a inverzních problémů popsaných homogenní nebo nehomogenní parciální diferenciální rovnicí. Hlavní myšlenkou této metody je určit funkce, které by splňoval danou diferenciální rovnici (funkce Trefftz) tak, aby jejich lineární kombinace vyhověli okrajovým podmínkám

Modified face seal for positive film stiffness

The film stiffness of a face seal is improved without increasing the sealing and dam area by using an apparatus which includes a primary seal ring in the form of a nose piece. A spring forces a sealing surface on the seal ring into sealing contact with a seat to form a face seal. A circumferential clearance seal is formed in series with this face seal by a lip on the piece. The width of the surface of the lip is substantially the same as the width of the sealing surface on the face seal and the clearance between the surface on the lip and the shaft is substantially the same as the spacing between the face sealing surfaces on the face seal when the shaft is rotating. The circumferential clearance seal restricts the flow of fluid from a main cavity to an intermediate cavity with a resulting pressure drop. The hydrostatic opening face is strongly dependent on the face seal clearance, and the desired axial stiffness is achieved

Overview of NASA Glenn Seal Project

NASA Glenn hosted the Seals/Secondary Air System Workshop on November 14-15, 2006. At this workshop NASA and our industry and university partners shared their respective seal technology developments. We use these workshops as a technical forum to exchange recent advancements and "lessons-learned" in advancing seal technology and solving problems of common interest. As in the past we are publishing the presentations from this workshop in two volumes. Volume I will be publicly available and individual papers will be made available on-line through the web page address listed at the end of this presentation. Volume II will be restricted as Sensitive But Unclassified (SBU) under International Traffic and Arms Regulations (ITAR)

Effect of random forcing on fluid lubricated bearing

A model for a fluid lubricated bearing is derived for operation under conditions where external forces are subject to random fluctuations that may act to destabilise the bearing. The fluid flow through the bearing is described by a Reynolds equation for incompressible flow and is coupled to the axial displacement of the bearing faces as modelled by spring-mass-damper systems. Representative dynamics of a highly rotating bearing subject to external potentially destabilising random forcing is developed. An external force characterised by a noise term is imposed on the rotor, where both white noise and coloured noise are considered. For industrial applications it is important to evaluate potential bearing failure that can arise when the face clearance becomes sufficiently small. Therefore, a quantity of interest is the average time for the face clearance to reach a prescribed tolerance. A computational technique to evaluate the bearing characteristics is implemented based on a simple random walk for a Dirichlet problem for a linear parabolic partial differential equation combined with a Monte Carlo technique. Results of numerical experiments are presented, to give indicative predictions of possible face contact, which has the potential to result in bearing failure

Radial pressure distributions in an air-riding face seal

International audienceNon-contacting face seals rely on high pressures induced in a thin air-film between stationary and rotating faces. They offer ultra-low leakage and very low wear compared to contacting seals in aircraft engines. Large axial and radial movements and high temperature gradients can cause excessive distortion of the sealing faces which may become amplified at large radii, high differential pressures and rotational speeds. Such distortions alter the geometry of the gap thereby affecting the seal's performance. This paper presents an extensive investigation into the air-film behaviour of a face seal under convergent and divergent engine representative coning distortions = 0.5-2 degrees, gap = 50-300 m, and operating pressure differences =70-350 kPa. The investigation approach is both numerical and experimental. Experimental tests allowed the introduction of a known distortion onto the static face of the seal. Arrays of static pressure tappings in the primary sealing gap were used to measure the radial and circumferential variations. The experimental data are used to validate a 3D CFD model of the primary leakage path. The CFD model was generated using ANSYS ICEM and solved using ANSYS FLUENT. The models were run at the full range of operating pressures and geometries. Results show that converging coning provides the largest air-film pressures and hence the largest opening force while a diverging coning provided the least. At higher pressure ratios divergent gaps exhibited expanding supersonic flow but with unexpected levels of pressure recovery within the diverging duct. The pressure loss at the entrance to the gap was observed to be significant, particularly where entry gaps are larger. This effect was partially captured by CFD. The most significant discrepancies between CFD predictions and experiments were for the converging gap cases where the increased air-film pressure causes the disc to deform under pressure resulting in the CFD model over-predicting the pressure in the gap

Radial pressure distributions in an air-riding face seal

International audienceNon-contacting face seals rely on high pressures induced in a thin air-film between stationary and rotating faces. They offer ultra-low leakage and very low wear compared to contacting seals in aircraft engines. Large axial and radial movements and high temperature gradients can cause excessive distortion of the sealing faces which may become amplified at large radii, high differential pressures and rotational speeds. Such distortions alter the geometry of the gap thereby affecting the seal's performance. This paper presents an extensive investigation into the air-film behaviour of a face seal under convergent and divergent engine representative coning distortions = 0.5-2 degrees, gap = 50-300 m, and operating pressure differences =70-350 kPa. The investigation approach is both numerical and experimental. Experimental tests allowed the introduction of a known distortion onto the static face of the seal. Arrays of static pressure tappings in the primary sealing gap were used to measure the radial and circumferential variations. The experimental data are used to validate a 3D CFD model of the primary leakage path. The CFD model was generated using ANSYS ICEM and solved using ANSYS FLUENT. The models were run at the full range of operating pressures and geometries. Results show that converging coning provides the largest air-film pressures and hence the largest opening force while a diverging coning provided the least. At higher pressure ratios divergent gaps exhibited expanding supersonic flow but with unexpected levels of pressure recovery within the diverging duct. The pressure loss at the entrance to the gap was observed to be significant, particularly where entry gaps are larger. This effect was partially captured by CFD. The most significant discrepancies between CFD predictions and experiments were for the converging gap cases where the increased air-film pressure causes the disc to deform under pressure resulting in the CFD model over-predicting the pressure in the gap

Advances in Fluid Power Systems

The main purpose of this Special Issue of “Advances in Fluid Power Systems” was to present new scientific work in the field of fluid power systems for hydraulic and pneumatic control of machines and devices used in various industries. Advances in fluid power systems are leading to the creation of new smart devices that can replace tried-and-true solutions from the past. The development work of authors from various research centres has been published. This Special Issue focuses on recent advances and smart solutions for fluid power systems in a wide range of topics, including: • Fluid power for IoT and Industry 4.0: smart fluid power technology, wireless 5G connectivity in fluid power, smart components, and sensors.• Fluid power in the renewable energy sector: hydraulic drivetrains for wind power and for wave and marine current power, and hydraulic systems for solar power. • Hybrid fluid power: hybrid transmissions, energy recovery and accumulation, and energy efficiency of hybrid drives.• Industrial and mobile fluid power: industrial fluid power solutions, mobile fluid power solutions, eand nergy efficiency solutions for fluid power systems.• Environmental aspects of fluid power: hydraulic water control technology, noise and vibration of fluid power components, safety, reliability, fault analysis, and diagnosis of fluid power systems.• Fluid power and mechatronic systems: servo-drive control systems, fluid power drives in manipulators and robots, and fluid power in autonomous solutions

Numerical Heat Transfer and Fluid Flow 2021

This reprint focuses on experiments, modellings, and simulations of heat transfer and fluid flow. Flowing media comprise single- or two-phase fluids that can be both compressible and incompressible. The reprint presents unique experiments and solutions to problems of scientific and industrial relevance in the transportation of natural resources, technical devices, industrial processes, etc. In the presented works, the formulated physical and mathematical models together with their boundary and initial conditions and numerical computation methods for constitutive equations lead to solutions for selected examples in engineering

Design and performance analysis of a novel face gas seal

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The scope of this work carried two objectives, each focusing on theoretical model development, performance prediction and experimental evaluation of two concepts, of face type non-contacting gas seals. The theoretical modelling and experimental testing were undertaken across a high duty-operating envelope up to 300 bar, 12000 rpm and 1200 C. For both sets of experiments, specialised test equipment and test rig were designed and built. The first objective was to determine the performance of a slot feed design of non-contacting gas design, by evaluating its performance across the full performance envelope. A set of test seals was made for experimental evaluation. A suitable computer model was developed and validated against experimental data. Results showed good seal performance across the main duty conditions and the model showed good correlation with the experimental test data. Under the second objective, a totally novel design of non-contacting gas seal was proposed, incorporating a unique lift groove geometry (patent pending). A novel and sophisticated computer model was developed to accurately predict the performance of this design. The model was made fully coupled between the fluid and structural domains of the gas seal. The model predictions were verified against the experimental data. The correlation between the two was found to be very close and consistent across the entire performance envelope of the seals. The novel design concept performed extremely well under all the test conditions, both real and artificial. The theoretical model developed as part of this research proved itself to be an effective analysis and performance prediction tool