Pelton wheel experiment lab report

Lab 5: Pelton Turbine ENGR 3471 – Fluid Mechanics Laboratory Introduction The Pelton wheel is an impulse-type water turbine that extracts energy from the impulse of moving water. Many variations of impulse turbines existed prior to Pelton's design, but they were less efficient. Water leaving those wheels typically still had high velocity carrying away much of the kinetic energy. Pelton's paddle geometry was designed so that when the rim ran at half the speed of the water jet, the water left the wheel with very little speed; thus extracted almost all of the water's impulse energy allowing for a very efficient turbine. Objectives Measure the conversion efficiency of a Pelton wheel turbine and compare measured data to theoretical values. Experimental Setup Figure 1: Pelton Turbine Procedure ▪ Fill the hydraulic bench with water. ▪ Connect the outlet hose of the bench with the inlet pipe of the apparatus and secure with a hose clip. ▪ Place the apparatus on top of the hydraulic bench so that the outlet is aligned with the grate on the bench. ▪ Turn on the pump and adjust the water flow rate via the bench valve. ▪ Set the needle valve at the inlet of the turbine at 2.5 turns clockwise from the fully open position. ▪ Make sure the spring scales are at the zero position, thus not applying any tension to the turbine. ▪ Adjust the rotor speed using the bench valve as a controller and the laser tachometer as an indicator so the turbine blades rotate at an approximately 1000 rpm with no load (runaway speed). ▪ SAFETY PRECAUTION: DO NOT STARE AT THE MEASURING BEAM OF THE LASER TACHOMETER! ▪ Using the hydraulic bench, calculate an experimental flowrate for the current valve setting by measuring the time it takes to accumulate 15 L in the basin. Do this 3 times to obtain enough data for averaging. ▪ Load the turbine by applying tension to one or both of the spring scales to reduce its speed from 1000 to 100 rpm in 100 rpm increments recording the spring scale readings at each increment. ▪ Reduce the speed to zero by applying tension and record data when rpm = 0. Calculation ▪ Enter the experimental data in the provided table. ▪ Plot turbine power (hp) versus rotating speed (rpm). ▪ Calculate the tangential wheel speed at maximum power. ▪ Calculate the ratio of wheel speed to jet velocity. ▪ Calculate the turbine head, hturbine ▪ Calculate the efficiency of the turbine at maximum power. ▪ Show a sample calculation for one data point. Discussions ▪ Compare calculated wheel speed to jet velocity ratios to theoretical values at the maximum power. ▪ Discuss the reasons and implications of any possible discrepancies. ▪ List and discuss at least two factors that make turbine efficiency less than 100%. ▪ Briefly explain why actual Pelton turbine blades have exit angles less than 180°. Experimental Records Table 1. Volumetric Flow Rate Run V (L) 1 2 3 I. Constants DPony = 1.75” θBlade = 170 ° AJet = 41.1 mm² @ 2.5 turns from closed t (s) Q (m³/s) 𝑄̂ (m³/s) II. Inlet Power (single pass calculation: calculate at 1000 rpm) Wheel Velocity: Jet Velocity: Bernoulli Equation: 𝑟𝑒𝑣 𝑉𝑊ℎ𝑒𝑒𝑙 = 𝜔 (𝑚𝑖𝑛) ∙ 𝑉𝐽𝑒𝑡 = 𝐴 𝑚3 ) 𝑠 𝑄( 2 𝐽𝑒𝑡 (𝑚𝑚 ) 𝑃𝑖𝑛 𝜌 + 𝑉𝑖𝑛 2 2 ∙ 𝐷𝑃𝑜𝑛𝑦 2 (𝑖𝑛) ∙ 106 𝑚𝑚2 1 𝑚2 + 𝑔𝑧𝑖𝑛 = 𝑃𝑜𝑢𝑡 ∙ 𝑟𝑒𝑣 1 𝑚𝑖𝑛 60 𝑠 𝑉𝑜𝑢𝑡 2 + 𝑔𝑧𝑜𝑢𝑡 + 𝑔ℎ𝑡𝑢𝑟𝑏𝑖𝑛𝑒 Pin = Pout = 1 atm, zin = zout = 0, Vin = VJet, Vout ≈ 0 Substituting: ℎ𝑡𝑢𝑟𝑏𝑖𝑛𝑒 = 1 2𝑔 = 𝑃𝑜𝑤𝑒𝑟 𝜌𝑔𝑄 𝑚3 𝑘𝑔 𝑃𝑜𝑤𝑒𝑟 = 2 𝜌 (𝑚3 ) 𝑄 ( Power: 𝑠 𝑠 2 Given: 𝑉𝐽𝑒𝑡 2 𝑚 1𝑚 ∙ 39.36996 𝑖𝑛 = 𝑚 = + 𝜌 2𝜋 𝑠 2 𝑚2 𝑁∙𝑠2 𝐽 𝑊 ) 𝑉𝐽𝑒𝑡 ( 𝑠2 ) (𝑘𝑔∙𝑚) (𝑁∙𝑚) (𝐽⁄𝑠) = 𝑊 III. Outlet Power (recurring calculation: calculate for each increment → Table 2) 𝐷𝑃𝑜𝑛𝑦 1𝑚 𝐽 (𝑖𝑛) ∙ Torque: 𝑇 = |𝐹1 − 𝐹2 |(𝑁) ∙ ∙ = 𝐽 2 𝑟𝑒𝑣 2𝜋 𝑃𝑜𝑤𝑒𝑟 = 𝑇(𝐽) 𝜔 (𝑚𝑖𝑛) 𝑟𝑒𝑣 ∙ Power: 39.36996 𝑖𝑛 𝑁∙𝑚 1 𝑚𝑖𝑛 𝑊 ∙ = 𝑊 60 𝑠 𝐽⁄𝑠 IV.