Pumps & Physics Essay

Whats unsea male childed?When I was thinking about which aspect of physics to investigate for my investigation, I knew it was a ingenuous idea to choose something that really interested me. At the era I was becoming more and more fascinated by subatomic p expressions. I like the fact that much of it was new and not understood properly, unlike the classical physics that ein truthone associates the subject with. Unfortunately, highschool muscularity physics does not translate into veracious practical coursework. However, while reading Six Easy Pieces, a book adapted from Richard Feynmans famous textbook The Feynman Lectures on Physics, I noticed that a actually common everyday phenomenon is still not properly understood by physicists. Encouraged by the prospect of discovering something new, I read on.Chaotic ideasFeynman wrote (on paginate 66) There is a physical problem that is common to many battlegrounds, that is very old, and that has not been solvedIt is the analysis of circulating or turbulent fluidsNo-one can die it from first principlesWow something science cant explain I plan.I looked on the internet for further details and I make up a poster from World Maths Year 2000 (http//www.newton.cam.ac.uk/wmy2kposters/march/), launching just the type of unpredic confuse fluid effort that Feynman was writing about. Its a new and exciting branch of maths called chaos theory and it is just embark onning to be understood mathematically. The main idea is that unproblematic systems can show very complicated behaviour that seems to have no repeating pattern. The sums that describe these systems are difficult to thump your head round and appear to be way beyond my abilities as an A-Level maths student.Despite this, I felt something chaotic was an excellent phenomenon to look into for this task its a chance to do some experimental work where there isnt a perfect formula or a flawless explanation in any textbook. I couldnt swan on distorting my result s to fit a bare(a)x law, so my experimentation had to be rigorous.LimitationsIt was important to find a subject that was practical to investigate at school. darn I was watching water swirl down the drain as I filled the kettle at home, I wondered how widely-used machines like ships propellors cope with the unpredictable world of chaos. Propellers have an unusual and distinctive exercise invented to reduce turbulence. I precious to investigate why this particular occasion works so well and if it can tell us anything about turbulent flow. Conveniently, water and propellors are easy-to-use in school labs (or so I thought).Best of all, I thought, if I could model the situation only ignore the inwardness of turbulent water, I could look at the mechanics of the propeller, and thusly examine the theory with what happens in real life. It seemed like a good mix of fresh ideas and traditional physics problems.I talked about my plans to some of my teachers and one of them mentioned t hat his son had done a PhD degree in the formation of bubbles by marine propellers an effect called cavitation. This encouraged me to continue with this project, knowing that it relates to flow rate areas of research and is an important and worthwhile topic.ResearchIt turns out that one of the most interesting applications of pumps is in attempt engines. As fire services are public organisations they make available potentiometer of high-quality, free tuition online. Engineering sites were also useful.* The Physics Behind FirefightingAmerican high-school physics projecthttp//ffden-2.phys.uaf.edu/212_fall2003.web.dir/Matt_Taylor/Matt1.dwt* How Fire Engines orbitGeneral informationhttp//science.howstuffworks.com/fire-engine.htm* Bedfordshire & Luton Fire and hand over ServiceMy local fire brigade, who I actually went to visit to find out morehttp//www.bedsfire.gov.uk/index.htm* American Turbine Pump CalculationsWeb-based program for working out quantities in pumpinghttp//americ anturbine.net/formulacalc/pump.htm* Impeller DesignThe engineering that goes into pumpshttp//homepage.mac.com/mrbach/mixdesign.htm* Firefighting.com affairful data on pumps but uses frames so I cant give a full URLhttp//www.firefighting.com* How Things WorkA simple explanation of propellers and aerofoilsLesley Firth, Kingfisher, 1983 p13* The Physics of FirefightingSome simple principles explainedPhysics Teacher, vol 28, p 599* FirefightingContains a bit of physics but interesting background informationJack Gottschalk, Dorling Kindersley, 2002, ISBN 0789489090, p128* Go with the flowArticle about modelling granular and fluid motionNew Scientist, 2 August 2003, p38-39Preliminary ExperimentsI wanted to find the most efficient propeller design. From research I found out that propellers have different shapes for different tasks, so my first goal was to get a propeller up and working, and then look at what I could change to make it run more efficiently.These are the variables I aimed to evaluate for their effect on index number transfer efficiency in introductory tests* The speed of rotation* The size of the propeller* Since speed of rotation is less era down to collect data for, Ill look at it first. I intend to plot a graph of speed of rotation vs. output flow rate.Considering the shape of a ships propeller, I expected to be looking at these variables later on* The number of blades on the impeller* The shape of the blades* The orientation of the blades (what cant they are in relation to the axis of rotation)The physics principles that are important here are mechanical ones. The efficiency of the propeller depends on how much of its power goes into pushing water outwards and how much is wasted on heating the water up or ca development it to form whirlpools.New Scientists article Go with the flow mentioned the Bernoulli Effect, which is observed on aircraft wings and on propeller blades.Lower dragHigher pressureA blade with a cut plane and a right away plan e forces some air or water on a longer route over the curve, and the rest takes the shorter flat route. The longer journey over the curved plane causes a drop in pressure, which translated to lift in planes, and thrust in propellers.According to all the textbooks, the best number of blades, the blade angle, the speed of rotation and the size of propeller all contribute to the efficiency. It seems like Ive got my work cut out for me. Im going to concentrate on rotation speed and its effect on water flow rate outwards. Lets see what the preliminary tests show. body of water flows inAxlePropellerWatertight casingWater flows outPlanningRisk Assessment1,2Apparatus or procedureHazardPrecautionsAll apparatus incident or fireSupervise the experiment at all times and clear away at the end of the session. Store all equipment safely and securely. boiling water for shaping polypropene propellersRisk of scaldingTake care with boiling water, paying attention at all times. Stand well back from th e saucepan and do not move it while the water is hot. Use a heat-insulating towel to manipulate the hot polypropene.Electric circuit in generalRisk of fire from short circuiting etc.Use insulated wires, keep connections clean and dry, and always supervise the apparatus while current is flowing.Do not leave the set-up unattended without unplugging the mains supply.Use wires of appropriate diameter to prevent overheating resulting in fire.Rapidly rotating propellerPossibility of smirch from contact with rotating blades of propellerLeave move switched off until train to record data. Take care to keep your distance from the propeller, especially fingers.Heavy equipment (power pack, retort stands)Falling equipment could injureEnsure stands etc. are sturdily laid and avoid placing equipment near the very edge of the work bench.Power packOutput 13V 5A DCInput 230V mains ACRisk of electrocution from mains insert(risk of injury from output voltage is minimal)Keep power pack away from th e wet part of the apparatus (to prevent conduction through water). In my experiment, I leave alone keep all the electrics on a shelf above the level of the water-containing apparatus.Ensure all water-containing equipment is as waterproof as possible, and have towels to hand to pick up spills.Do not leave the set-up unattended without unplugging the mains supply.Preliminary findingsIn the research and rationale section, I identified variables I wanted to investigate. I conducted preliminary experiments to found out which variables were the most practical to focus on. The basic aim is to narrow my search down to one or possibly twain variables and then find the most power-efficient value for each variable.Size of propeller was very difficult to control since I found that the propeller will only farm the water unless it tightly fits the container. Small propellers did not displace any water. Only propellers with a diameter 1 or 2mm less than the diameter of the container were effec tive in pumping water. As such, I determined not to consider investigating this variable.Angle of propeller blade plunge is possible to vary, but I found the range of angles possible with the materials I had chosen were too limited. I developed a method of cutting out rectangles of polypropene sheeting, boiling them in water and crimp them to the right shape, but the blades often snapped and it was tricky to get the blades to remain at the chosen angle as they cooled and hardened. I decided to keep blade inclination constant.45 might seem to be an appropriate angle of inclination to choose for all the propellers I will compare, but most propellers I found photographs of from my research showed shallower angles of blade inclination. I have decided that all my propellers will be inclined at 30 because it is easier to make the propellers this shape and I live with that this is a more efficient angle than 45 since many propellers are about this angle.Speed of rotation turned out to be very simple to control with the use of the variable voltage power pack. I investigated the effect of power input on rotation speed (or angular fastness of the propeller as I call it from here on in).Using a stroboscope, I determined the linear relationship in the midst of the voltage supplying the motor (V) and the angular velocity (?) of the propeller shaft in air. I adjusted the frequency of the strobe light until the propeller appeared not to rotate.At this frequency, the time between flashes of the strobe and the time for one blade of the propeller to reach the former position of the blade before it is equal. If you find the angle in radians (?) between two adjacent blades and multiply it by the frequency (f) of the stroboscope (the time between flashes), you are left with the angular velocity (?) of the propeller, i.e. the rate of rotation.? = ?fIn the table below, V and f were determined experimentally and ? was calculated by multiplying f by ?. Since the frequency is onl y known to two significant figures, the angular velocity can only be determined to 2 s.f.Angle between blades, ?degrees72Angle between blades, ?radians0.4?VV02.254.256.258.7510.0013.000.25fs-101326365057740.5?rad s-101632456372930.5 erst the propeller is immersed in water the relationship between ? and V changes. The relationship is non-linear and, unlike the graph above, is different for every propeller.In light of the preliminary experiments I will transform this method to vary the power supplied to the drill that drives the propeller. It will not matter that the speed of rotation varies depending on how much the water resists the motion of the propeller. The only data that are needed to calculate the efficiency of the system are power input and useful power output.EfficiencyAt this prove it is important to mention that I am concentrating on the efficiency of the propeller at displacing water. Percentage efficiency = useful power output / power input 100%, or rewritten in symbo ls, ? = Puseful out / Pin. Also, power input is proportional to input voltage since current is constant at 5 A in my equipment.P = VI and I = 5 Power (Watts) = 5 x voltage (Volts).Review of purpose of investigationThe focus of this investigation is to determine the best number of blades for a propeller to have to maximise energy-efficiency. Experiments will compare propellers with 2, 4 and 6 blades. The energy efficiency of the three propellers when displacing water will be determined and compared. Their efficiency may not be independent of the rate of rotation. This too will be investigated and analysed.The analysed results will show which of the three propellers is most energy efficient in at each rate of rotation investigated.Extract from Eric Weissteins World of Physicshttp//scienceworld.wolfram.com/physics/Screw.htmlA screw is a simple machine that is actually a version of the inclined plane. The pitch of the screw corresponds to the inclination of the plane a higher pitch (i. e., more threads per length) representation less inclination, and thus easier turning, but also more turning that needs to be done to travel a given length. As with the other simple machines, the required force is reduced, but the amount of work done is the same.Apparatus13V max. variable voltage power packRetort stands and clamps15 cm rulerSilicone polymer window sealantGarden hosepipeExpanded polystyrene for supportsMultimeter (0.25V, 0.25A tolerance)Polypropene sheet for making propellersPET lemonade bottles (2 Litre capacity)Plastic funnel for fillingstopwatchCollection bottle with 2 litre mark ( 0.002 L)Cordless electric screwdriver/drillSteel axleVolumetric burettePET pudding basins to contain propellerWaterColour-coded wires and crocodile clipsSaucepan, hotplate and tongs for heating and reshaping polypropene into propellersScissors and craft knife for cutting out propeller shapes from polypropene sheetApparatus set-upThese diagrams show how I designed the equipment. The ci rcuit diagram connected to the drill represents the power pack, and its voltage selector is displayed as a variable resistor. The plastic volute is the container that houses the propeller.To begin with, water fills the water tank and the plastic volute. Activating the power pack supplies an electric current to the drill, which rotates the propeller.Variables to controlVariableHow I will control itviscosity of waterConstant at constant temperature and pressurePower and speed of rotation of propellerUse a power pack instead of a battery to supply the cordless drill. Use the same power pack, axle and drill throughout the experiment. Rotation speed does not vary linearly with power but carefully designing the experiment can avoid problems.Room temperature and pressureConstant at 20C due to central heating. Atmospheric pressure changes are insignificant to this experiment.Plan for laboratory sessionsSession and durationTargetsBefore lab work beginsBuild the waterproof sections of the app aratus and seal them with silicone polymer. defile a cordless drill.First two hoursSet up all apparatus, construct the propellers and test the experiment to ensure it works as planned snatch two hoursMeasure the time taken to raise 2 Litres of water through 50cm vertically by each of the three propellers, with 65W power input ternion two hoursRepeat the previous sessions experiment, but with the power set at 35W.Fourth two hoursBy considering the results collected before this session, decide which range of power input to investigate in detailFifth two hoursContinue gathering results for chosen range of power inputsRemaining timeInvestigate turning points and anomalies as necessaryIn between lab sessionsComplete results tables, draws graphs as appropriate and start to analyse findings. Use analysis to modify strategy and to make decisions on how to progress.While I was designing which equipment to use and how to use it, I thought carefully about accuracy and sensitivity. The major difficultness with this experiment is the unpredictable nature of the propellers unlike many other things physics, it is not easy to find a good estimate of what will happen in textbooks or online.One way of ensuring good results is to billhook the variables to a reasonable number of significant figures. The multimeter I chose to use is quick to respond to changes in current or potential difference and has fine graduations on its scale, providing high sensitivity. It also has very tight tolerances as it is designed for use in high act electronics, which contributes to the accuracy of the results I will gather.The multimeter is significantly more accurate and sensitive some of the digital alternatives at school. It responds to changes much quicker too.I have had to design and build quite a large amount of equipment just to make this project possible. To measure the volume of water pumped out by the system, I will calibrate the water collection bottle with graduations. To make sure they are very sensitive and accurate, I will use the high quality, high accuracy laboratory glassware available at school for use in chemistry and biology. The percentage error on the volume graduations on these pieces of equipment is very small (around 0.0003%).References for planning section1. Cambridge University Department of PhysicsPhysics risk assessment formhttp//www.phy.cam.ac.uk/cavendish/hands/forms/RAform.pdf2. CLEAPSS Secondary Schools websitehttp//www.cleapss.org.uk/secfr.htmImplementingModifications to planProblemSolutionHow to water-seal the full(a) systemCareful application of silicone sealant and gaffer tape at all junctions. Apparatus tested underwater by pressurising with air using a bike pump. Leaks located by bubbles escaping where seals were incomplete.How to get water to flow from the water reservoir into the propeller cavity, without providing any extra pressure that would reduce the workload of the propellerHeight of water reservoir bottle adjusted until w ater just reaches the top of the propeller cavity, without spilling out the output holeHow to accurately measure the volumes of water used in each experimentVolumetric glassware borrowed from chemistry departmentCalculation of power efficiency of pumping system?E = mg?hP = Et-1Useful power output = power spent on raising water against the force of the Earths gravitational fieldUseful power output = (mass of water raised (mwater) strength of gravity at sea level (g) height through which the water is raised (?h)) / time taken (t)Pout = mwaterg?ht-1The mass of water is proportional to its volume at constant temperature and atmospheric pressure. In these experiments, the temperature and pressure have been constant at 293K (20C) and cv Pa respectively. Under these conditions, water has a density of 998.2 kgm-3 (according to the Nuffield Advanced Science Data Book, Nuffield-Chelsea Curriculum Trust, Longman, 1984). Therefore, the time taken to raise the water and the number of blades on each propeller are the only variables in my experiment.