GUSTAF DE LAVAL ( ) Born May 9 th, 1845 Swedish engineer and inventor Milk cream separator one of his greatest inventions Sped up process of obtaining cream from the milk Introduced the concept of an impulse steam turbine Developed De Laval Nozzle to increase the steam jet to supersonic speed Used in modern rocket nozzles DE LAVAL NOZZLE Conversion/Diversion nozzle Isentropic and reversible process, so entropy is constant Gas speeds up to transonic speeds when entering the throat and exits the nozzle at supersonic speeds BLAISE PASCAL (1623 1662) Born June 19 th, 1623 In Auvergne, France French mathematician, physicist, inventor, writer and philosopher Created a mechanical calculating machine (Pascaline) Pascals Wager Hexagrammum Mysticum Pascals Triangle Important contributions to fluid mechanics PASCALS THEOREM Also known as Hexagrammum Mysticum States that if a hexagon is inscribed in a conic section (ellipse, parabola, or hyperbola), the points of intersection of the hexagons sides lie on a line called Pascals Line PASCALS TRIANGLE Each number is the addition of the two numbers above it These numbers correspond to the coefficients in binomial expansion Used to determine probability in combinations, where n C r = n! / [r!(n r)!] PASCALS LAW Principle transmission of fluid pressure Pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions such that pressure variations remain the same Can be mathematically written as: P = g ( h) SENSORS AND ACTUATORS Joseph Besgen C3 COSMOS 2015 SENSORS Sensor A transducer whose purpose is to detect characteristic of its environment and provide some corresponding output, such as an electrical or optical signal SENSORS Input: stimulus (temperature, pressure, light intensity, etc.) Output: electrical signal (voltage, current, frequency, phase, etc.) Passive Does not need an additional energy source Directly generates an electrical signal in response to an external stimulus Examples: thermocouple, photodiode, piezoelectric sensor Active Needs external power Uses energy source, called an excitation signal, to produce the output signal Examples: Resistive strain gauge, thermistor SENSOR CHARACTERISTICS Transfer function Accuracy Saturation Repeatability Sensitivity Hysteresis TRANSFER FUNCTION Represents the relation between stimulus s and response electrical signal S produced by the sensor Can be written as S = f(s). ACCURACY Measured as a highest deviation of a value represented by the sensor from the ideal or true value of a stimulus at its input SATURATION Every sensor has its limits, and at some levels of input stimuli, the output signal will no longer be responsive When this occurs, it is said that the sensor experiences a span-end nonlinearity or saturation REPEATABILITY Ability of a sensor to represent the same values under presumably identical conditions Possible sources of error include: Thermal noise Build-up charge Material Plasticity SENSITIVITY The minimum input of physical parameter that will create a detectable output change Also described as the ratio between a small change in electrical signal to a small change in physical signal Ex: A thermometer would have high sensitivity if a small temperature change resulted in a large voltage change HYSTERESIS Refers to the characteristic that a transducer has in being unable to repeat faithfully, in the opposite direction of operation, the data that have been recorded in one direction TYPES OF SENSORS Temperature Thermistors, thermocouples, RTDs Pressure Fiber optic, capacitive Level sensors Fuel level sensors, radar, thermal displacement Proximity and displacement LVDTs, photoelectric, ultrasonic Gas and chemical Semiconductor, infrared, electrochemical Acceleration Gyroscope, accelerometer Other density, humidity, mass, force, and viscosity sensors USES OF SENSORS Allow us to monitor our surroundings in ways never imagined In industry: Networked vibration sensors alert if machinery is beginning to fail Temperature and humidity sensors monitor refrigerated items In the environment: Nitrate sensors detect industrial and agricultural runoff in rivers, streams, etc. Seismic monitors provide an early warning system for earthquakes For safety and security: Firefighters scatter numerous sensors throughout a building to monitor flare-ups and map hot spots TSA employs body scanning imaging devices Miniature chemical and biological sensors in public places raise alarm at first signs of terror agents such as small pox or anthrax In education: Students are able to use sensors and powerful software to collect and analyze data ACTUATORS Actuator - type of motor that is responsible for moving or controlling a mechanism or system via an electrical stimulus; converts energy into motion ACTUATORS Operated by a source of energy such as an electric current Input: Electrical Signal (voltage, current) Output: Mechanical (force, pressure, displacement) or display function (dial indication, light, display) Create linear, rotary, and oscillatory motion ACTUATOR CLASSIFICATIONS Electromechanical Pneumatic Linear Hydraulic Newer actuators include: smart material actuators, microactuators, and nanoactuators ELECTROMECHANICAL ACTUATORS A motor that converts electrical energy to mechanical energy DC and AC motors most commonly used AC motors are more popular because they use AC power and are less expensive Induction motors are used widely in household appliances Synchronous motors are used efficiently in industry PNEUMATIC ACTUATOR Uses pressurized air and a compressor to achieve motion Much lighter, simpler, and easier to mount than motors Can be more expensive and more complex than other actuators Examples: Combustion engines Air compressors Nail guns Pneumatic mail tubes Future uses: Incorporation of thermal damping in hydro-pneumatic suspension systems LINEAR ACTUATOR Electromagnetic devices that develop short-travel progressive linear motion Used mainly when precision is need and no maintenance is desired Examples: Machine tool sliding tables (CNC Machines) Compressors Pumps Electromagnetic valve actuators AC and DC linear motors Future uses: Rope-rope less elevators, artificial hearts and electromagnetic valves on thermal engines HYDRAULIC ACTUATOR A cylinder or fluid motor that converts hydraulic power into useful mechanical work Used for its high force capability and good mechanical stiffness Linear, rotary, and oscillatory motion Examples: Utilized in many construction machines for heavy lifting Bending and buckling test machines Hydraulic pumps Throttle or jet control TYPES OF ACTUATORS Mechanical Produce/change motion Motors, engines, pumps Acoustic Produce sound Speakers, headphones Optical Produce light LEDs, lasers Other Produce radiation, fields (electric and magnetic) WORKS CITED