The study deals with the cooling of a high-speed electric machine through an air gap with numerical and experimental methods.The rotation speed of the test machine is between 5000-4000 r/rain and the machine is cooled...The study deals with the cooling of a high-speed electric machine through an air gap with numerical and experimental methods.The rotation speed of the test machine is between 5000-4000 r/rain and the machine is cooled by a forced gas flow through the air gap.In the previous part of the research the friction coefficient was measured for smooth and grooved stator cases with a smooth rotor.The heat transfer coefficient was recently calculated by a numerical method and measured for a smooth stator-rotor combination.In this report the cases with axial groove slots at the stator and/or rotor surfaces are studied.Numerical flow simulations and measurements have been done for the test machine dimensions at a large velocity range.At constant mass flow rate the heat transfer coefficients by the numerical method attain bigger values with groove slots on the stator or rotor surfaces.The results by the numerical method have been confirmed with measurements.The RdF-sensor was glued to the stator and rotor surfaces to measure the heat flux through the surface,as well as the temperature.展开更多
A centrifugal compressor with a vaneless diffuser was studied experimentally and numerically. The main target of the study was to analyze the volute flow. Two different volute geometries was studied. The numerical sol...A centrifugal compressor with a vaneless diffuser was studied experimentally and numerically. The main target of the study was to analyze the volute flow. Two different volute geometries was studied. The numerical solution was done by using a steady-state RANS code at both design and off-design conditions. Both calculated and measured pressure and velocity distributions are presented.展开更多
The volute of a centrifugal compressor causes a non-uniform pressure distribution which leads to a radial force on the impeller. This force was measured using magnetic bearings. In addition, the radial force was estim...The volute of a centrifugal compressor causes a non-uniform pressure distribution which leads to a radial force on the impeller. This force was measured using magnetic bearings. In addition, the radial force was estimated using the static pressure distribution measured at the impeller outlet. The impeller force was found to be the highest at choke, the lowest at the design flow and moderate at stall. The radial force determined from the pressure measurements was only slightly different from the force obtained from the bearing measurements. The rotational speed was seen to affect the force to some extent.展开更多
文摘The study deals with the cooling of a high-speed electric machine through an air gap with numerical and experimental methods.The rotation speed of the test machine is between 5000-4000 r/rain and the machine is cooled by a forced gas flow through the air gap.In the previous part of the research the friction coefficient was measured for smooth and grooved stator cases with a smooth rotor.The heat transfer coefficient was recently calculated by a numerical method and measured for a smooth stator-rotor combination.In this report the cases with axial groove slots at the stator and/or rotor surfaces are studied.Numerical flow simulations and measurements have been done for the test machine dimensions at a large velocity range.At constant mass flow rate the heat transfer coefficients by the numerical method attain bigger values with groove slots on the stator or rotor surfaces.The results by the numerical method have been confirmed with measurements.The RdF-sensor was glued to the stator and rotor surfaces to measure the heat flux through the surface,as well as the temperature.
文摘A centrifugal compressor with a vaneless diffuser was studied experimentally and numerically. The main target of the study was to analyze the volute flow. Two different volute geometries was studied. The numerical solution was done by using a steady-state RANS code at both design and off-design conditions. Both calculated and measured pressure and velocity distributions are presented.
文摘The volute of a centrifugal compressor causes a non-uniform pressure distribution which leads to a radial force on the impeller. This force was measured using magnetic bearings. In addition, the radial force was estimated using the static pressure distribution measured at the impeller outlet. The impeller force was found to be the highest at choke, the lowest at the design flow and moderate at stall. The radial force determined from the pressure measurements was only slightly different from the force obtained from the bearing measurements. The rotational speed was seen to affect the force to some extent.
