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609 results about "Drag coefficient" patented technology

In fluid dynamics, the drag coefficient (commonly denoted as: Cd , Cₓ or Cw ) is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water. It is used in the drag equation in which a lower drag coefficient indicates the object will have less aerodynamic or hydrodynamic drag. The drag coefficient is always associated with a particular surface area.

Method for accumulated damage computation and life prediction of IGBT module used for electric car

The invention relates to a method for accumulated damage computation and life prediction of an IGBT module used for an electric car. The method is characterized by comprising the following steps of setting whole-car parameters, relative parameters of the IGBT module, a road surface rolling friction coefficient and a drag coefficient; fitting a speed-junction temperature mean value relation curve and a speed-junction temperature fluctuation amplitude relation curve; obtaining running speed-time data and road surface gradient data of the electric car in real time; judging a car running speed change condition and a climbing condition and respectively computing the IGBT accumulated damage according to two modes in order to obtain total accumulated damage of the IGBT module; and predicting the lifetime and the life mileage of the IGBT module. According to the method, the direct link is established between the running condition of the electric car and the working condition of the IGBT module, the junction temperature data and the accumulated damage of the IGBT module are directly computed, the method can be used for researching the influence of factors, such as environment temperature, road surface gradient and running acceleration, on the service life of the IGBT module used for the electric car, and the method has wide application value.
Owner:HEBEI UNIV OF TECH

High temperature valve detecting and testing system

The invention discloses a high temperature valve detecting and testing system, comprising an oil feed pump, an oil storage tank, a pressure pump, a buffer tank, a detecting device and a condensing device, wherein an electric heater and a pressure transmitter are installed on the top part of the oil storage tank; the bottom part of the oil storage tank is connected with the buffer tank through a third trunk pipeline; another pressure transmitter and a temperature sensor are installed on the inner side wall of the buffer tank; the buffer tank is connected with an oil inlet of a to-be-detected valve through a fourth trunk pipeline; the detecting device comprises a detecting table and a torque testing device; the valve rod of the to-be-detected valve is connected with the torque testing device; and the oil outlet of the to-be-detected valve is connected with the oil storage tank through a fifth trunk pipeline, the condensing device and a second trunk pipeline in sequence. The high temperature valve detecting and testing system is simple in structure and convenient to operate; and by the adoption of the detecting and testing system, the resistance coefficient and the torque performance of a high temperature valve and the flow characteristic can be tested, and the leakage amount can be detected.
Owner:WUHAN INSTITUTE OF TECHNOLOGY +1

Bump air inlet method for realizing integration of unequal-strength wave system with forebody

The invention provides a bump air inlet method for realizing integration of an unequal-strength wave system with a forebody, relating to the technical field of ultrasonic air inlet. The method comprises the following steps that: 1, an air inlet wave system adopts an external-compression double wave system structure based on an unequal-strength system, and the total pressure recovery coefficient sigma=sigma1*sigma2, wherein the sigma1 and the sigma2 are total pressure recovery coefficients of a conical shock wave and a normal shock wave; 2, a cone with a semi-cone angle delta c formed by the conical shock wave generates a second conical shock wave with second semi-cone angle beta in ultrasonic flow; 3, the bump height of the air inlet is h, the h/delta is 2-2.5 when the local boundary layer thickness is delta, the bump compressive plane generated in the step 2 is scaled to meet the requirement of an actual size; and 4, the lip of the air inlet adopts a conformal and sweepback lip design. The method realizes reduction of throat Mach number of the air inlet, improves the air inlet performance to ensure that the lip sweepback angle of the air inlet, the maximum turning angle of the bump compressive plane and the inlet normal shock wave angle are consistent, can increase the curve of the total pressure recovery coefficient, and reduces resistance coefficient.
Owner:NANJING UNIV OF AERONAUTICS & ASTRONAUTICS

Method for monitoring friction drag and torque of large-displacement well

The invention provides a method for monitoring the friction drag and the torque of a large-displacement well. The method comprises the steps of firstly, building a friction drag and torque mechanical analysis model of the large-displacement well, and compiling an analysis program or analysis software; secondly, carrying out friction drag and torque simulation analysis computing under a track section designing condition; compiling monitoring route maps of drilling tool feed-off hook load, drilling tool lift-up hook load and idling lift-off-well bottom hook load under different friction drag coefficient conditions and route maps of rotary drilling torque along with well depth; recording the drilling tool feed-off hook load, the drilling tool lift-up hook load, the idling lift-off-well bottom hook load and the rotary drilling torque of actual drilling during site operation; finally, describing data under actual drilling record on the route maps, and comparing the data with predicted values under different friction drag coefficients and analyzing. According to the method for monitoring the friction drag and the torque of the large-displacement well, provided by the invention, the reason that causes the friction drag and the torque is deeply analyzed through real-time monitoring on the friction drag and the torque, and meanwhile, response analysis is carried out on the borehole cleanliness degree, the borehole quality, the drilling parameters, a bottom drilling tool combination, the drilling fluid performance change, the use of an anti-friction and torque-reducing tool and the like.
Owner:CHINA PETROCHEMICAL CORP +1

Deep learning-based reentry prediction correction fault-tolerant guidance method for hypersonic aircraft

The invention discloses a deep learning-based reentry prediction correction fault-tolerant guidance method for a hypersonic aircraft, and belongs to the technical field of aircraft navigation guidanceand control. The method comprises the following steps of firstly, balancing the rudder deflection of an aircraft under a fault condition, selecting an attack angle profile within a feasible attack angle range, and simultaneously obtaining the lift and drag coefficients of the aircraft; then, enabling the attack angle profile to be substituted into a reentry process constraint equation to obtain areentry corridor meeting the requirements, and enabling the reentry corridor to be converted into a roll angle amplitude constraint; estimating the change amount delta CL and delta CD between the lift and drag resistance coefficient of the aircraft relative to the lift and drag coefficients of the normal aircraft, and combining the reentry terminal constraint equation to obtain an inclination angle amplitude; utilizing the inclination angle reversal logic based on the course angle error corridor to obtain an inclination angle symbol; and finally, calculating the inclination angle profile by using the inclination angle amplitude and the inclination angle symbol, and combining the attack angle profile to obtain the guidance command meeting the requirement after the fault. The method is highin guidance precision, good in algorithm instantaneity and capable of meeting the requirement of fault-tolerant guidance.
Owner:BEIHANG UNIV

Heating pipe network hydraulic simulation model identification correction method and system, method of operation

The invention relates to a heating pipe network hydraulic simulation model identification correction method and a system. The heating pipe network hydraulic simulation model identification correction method comprises the steps of S1, selecting multiple groups of actually measured data of a heating system under steady work conditions, S2, calculating theoretical values of the drag coefficient of all pipe section, and S3, establishing a hydraulic simulation model of heating pipe network, using particle swarm optimization method accompanied by multiple groups of actually measured data, identifying and calculating various resistance coefficient correction amount vectors, and through the various resistance coefficient correction amount vectors in the heating pipe network hydraulic simulation model, making the comparison between the flow conditions and the actual measured data under multiple working conditions, identifying the optimal resistance coefficient correction amount. The corrected model can better describe the actual physical system, and increase the calculation precision of the hydraulic calculation of heating pipe network. The application of a parallel computing architecture for the implementation for the identification of the particle swarm algorithm drag coefficient correction with high identification efficiency.
Owner:CHANGZHOU ENGIPOWER TECH

Reynolds number effect correcting method of zero lift-drag force coefficient

The invention discloses a Reynolds number effect correcting method of a zero lift-drag force coefficient. The method comprises the steps of: obtaining a zero lift attack angle [alpha]0 of an aircraft at a Mach number according to wind tunnel experiment data; calculating an actual Reynolds number ReH under each sea level altitude H based on an size and configuration of a product, and calculating a drag force coefficient CxH at the Mach number and at each altitude H when the attack angle [alpha] equals to [alpha]0, by a CFD method; increasing the Reynolds number of a blowing wind tunnel at the Mach number to the Reynolds number Re corresponding to the practical aircraft size according to a model scale, interpolating the Reynolds number Re with ReH values at different altitudes H at the step b to obtain flight altitude H wind tunnel experiment corresponding to the Re wind tunnel experiment, and calculating a drag force coefficient Cx0 of the aircraft when the attack angle [alpha] equals to [alpha]0 in the altitude H wind tunnel experiment; and obtaining a corrected value of the zero lift-drag force at the Mach number and at each flight altitude H. The Reynolds number effect correcting method of the zero lift-drag force coefficient is used for a small aspect ratio aircraft and is applicable to zero lift-drag coefficient correction.
Owner:JIANGXI HONGDU AVIATION IND GRP

A method and device for testing the frictional resistance coefficient of the inner wall of a pipeline

InactiveCN102269690ATest the coefficient of frictional resistanceGuaranteed turbulence intensityMachine part testingUsing mechanical meansEngineeringDrag coefficient
The invention discloses a device for testing a frictional drag coefficient of an inner wall of a pipeline. The device consists of a high speed fan, a frequency converter, a turbulence smoothening section, a pipeline bracket, the pipeline, a multitube pressure gauge, a Pitot tube and a slanting leg manometer, wherein the frequency converter is connected with the high speed fan; the front end of the turbulence smoothening section is connected with the outlet of the high speed fan, and the rear end is connected with the pipeline; the pipeline is arranged on the pipeline bracket with an adjustable mechanism; pressure testing holes are processed at different positions of the pipeline and are connected with the multitube pressure gauge through tee joints and hoses; and at the tail end of the pipeline, the wind speed in the pipeline is tested by the Pitot tube, and the Pitot tube is connected with the slanting leg manometer. A method for testing the frictional drag coefficient of the inner wall of the pipeline comprises the following six steps of: 1, selecting a testing scheme; 2, selecting a testing means; 3, distributing the pressure testing holes; 4, analyzing the experimental accuracy; 5, designing and manufacturing the pipeline bracket; and 6, assembling the testing device, wiring and debugging. The invention has application value in the technical field of pipeline pressure and friction drag testing.
Owner:BEIHANG UNIV

Accurate computing method used for pipeline resistance coefficient and based on numerical computation

The invention discloses an accurate computing method used for a pipeline resistance coefficient and based on numerical computation. According to the method, ANSYS-CFX is adopted to perform numerical simulation on a pipeline, and the temperature set in the numerical simulation and computed fluid energy loss per unit mass are in data comparison with the temperature obtained through experimental measurement and fluid energy loss per unit mass; and through the comparison, the temperature and the dynamic viscosity which are set in the numerical simulation are corrected, an optimal turbulence model is selected finally, and three-dimensional viscidity steady numerical simulation is performed on the pipeline under the conditions of different roughness and different flows. Each overflowing section total pressure obtained through the simulation is taken into a Bernoulli equation, and an on-way resistance coefficient and a local resistance coefficient of the pipeline under different conditions are inversely solved through the energy loss; and the data are guided into TableCurve3D for three-dimensional data curved surface fitting, and finally an optimal expression of the on-way and local resistance coefficients relative to relative roughness and Reynolds number is obtained. According to the accurate computing method, not only can the on-way and local resistance coefficients be accurately computed, but also an energy performance computation model of the pipeline system can be established on that basis, and energy-saving transformation is performed on the conventional pipeline system.
Owner:JIANGSU UNIV

Method for determining optimal combination operation scheme of circulating cooling water system water pump units and adjusting valves of petrochemical enterprise

The invention provides a method for determining an optimal combination operation scheme of circulating cooling water system water pump units and adjusting valves of a petrochemical enterprise. According to the method, maximum critical flow points of different combinations of the system water pump units during operation and required water power resistance coefficients of the water return pipe adjusting valves are determined; according to the minimum demand flow of a system at different water inlet temperatures, a system flow range corresponding to the various operation combinations, with the smallest the energy consumption, of the water pump units is determined, and the operation combinations of the circulating cooling water system water pump units can be optimized; for the determined optimal operation combination, corresponding to a certain minimum demand flow range of the system, of the water pump units, the minimum demand flow of the system is in the flow range but generally smaller than the maximum of the flow range, then by reducing the opening degrees of the adjusting valves, the operation flow of the system is reduced to be equal to the minimum demand flow of the system, the resistance coefficients of the adjusting valves and added values of the coefficients are determined, power of a water pump shaft is further reduced, and therefore the optimal operation combination of the circulating cooling water system water pump units and the adjusting valves can be achieved.
Owner:YANGZHOU UNIV

Golf ball trajectory simulation method

The invention is directed at a golf ball trajectory simulation method which sets up a golf ball model within a virtual airflow space where a grid has been generated, sets a weight for the ball model and applies initial conditions (initial velocity, launch angle, spin rate) to the ball model so as to cause the model to fly within the virtual airflow space, then calculates the lift coefficient and the drag coefficient for the golf ball from the air stream velocity, direction and pressure calculated in each grid cell, and calculates the flight distance and left-to-right dispersion for the golf ball from launch until landing by calculating the change in height, change in lateral direction, change in velocity and change in spin rate for the golf ball during flight. The trajectory simulation method divides the flight path of the golf ball model into two or three regions based on the criteria that Re=250,000 to 170,000 is a high-velocity region, Re=170,000 to 100,000 is a medium-velocity region and Re=100,000 and below is a low-velocity region, and sets up a height for the grid adjacent to the golf ball model surface in the high-velocity region (grid height A), a height for the grid adjacent to the golf ball model surface in the medium-velocity region (grid height B) and a height for the grid adjacent to the golf ball model surface in the low-velocity region (grid height B) such that grid height A<grid height B<grid height C.
Owner:BRIDGESTONE SPORTS
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