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DESIGN ANALYSIS for a SMALL SCALE ENGINE by Tim van Wageningen

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Contents - Motivation - Concepts - Performance Analysis - Conclusions - Questions ±40 min 2 MOTIVATIONS - CONCEPTS – PERFORMANCE I / II / III - CONCLUSIONS

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NatureTechnology scale → smalllarge Atalantaproject 3 MOTIVATIONS - CONCEPTS – PERFORMANCE I / II / III - CONCLUSIONS

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Micro Air Vehicle Flapping Wing Mechanism - Designed by Casper Bolsman - 0.6 gram - Performance estimate: - 0.5 W power output - Needed power density of system: 125 W/kg system: 125 W/kg - 6 minutes of flight time with 5% efficiency 5% efficiency MAV 4 MOTIVATIONS - CONCEPTS – PERFORMANCE I / II / III - CONCLUSIONS

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MAV in Action 5 MOTIVATIONS - CONCEPTS – PERFORMANCE I / II / III - CONCLUSIONS

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Hydrogen Peroxide - Master thesis of Arjan Meskers at the PME department, TU Delft department, TU Delft - Chemical energy: high energy density - Monopropellant - Clean products: oxygen and water vapor - Example catalysts: -Manganese oxide -Silver-Platinum 6 MOTIVATIONS - CONCEPTS – PERFORMANCE I / II / III - CONCLUSIONS

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Catalytic Reaction in Action 7 MOTIVATIONS - CONCEPTS – PERFORMANCE I / II / III - CONCLUSIONS

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Thesis Assignment Find an engine concept that: - is suitable for the MAV - 125 W/kg - 5% efficiency - uses hydrogen peroxide as fuel 8 MOTIVATIONS - CONCEPTS – PERFORMANCE I / II / III - CONCLUSIONS

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Possibilities 9 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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3 different approaches Turbine Piston Cylinder + + + + + 10 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Concept I: Tesla Turbine Engine + Easy implementation + Theory of Tesla Turbine predicts good efficiency at predicts good efficiency at small scale small scale - Conversion from rotation to linear motion to linear motion + + 11 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Concept I: Tesla Turbine Engine + + 12 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Concept II: Otto Engine + Proven concept on regular scale scale - Projects in literature show bad performance because of bad performance because of fluid leakage problem fluid leakage problem - Implementation difficult + 13 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Concept II: Otto engine + 14 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Concept III: Hot Air Engine + Easy implementation + Promising scaling aspects because heat transfer is more because heat transfer is more effective effective - Poor performance on regular scale scale + + 15 MOTIVATIONS - CONCEPTS – PERFORMANCE I / II / III - CONCLUSIONS

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Concept III: Hot Air Engine + + 16 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Performance - What influences the performance of these concepts? these concepts? - Concept I - Concept II - Concept III - Are the concepts suited for the MAV? -Power density -Efficiency 17 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Concept I: Tesla Turbine Engine 18 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Concept I: Tesla Turbine Engine: model Assumptions: Laminar flow No entrance effects Incompressible fluid 19 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Power Efficiency Pressure difference Length of belts (radius of discs) Height of gap (spacing between discs) 20 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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[2] V.G. Krishnan et al. A micro Tesla turbine for power generation from low pressure heads and evaporation driven flows. Transducers, 11:1851 – 1854, June 2011. Measurements with small scale Tesla turbines Pressure difference: ~20 kPa Measured Performance 45 mW 18% efficiency Estimated power density: 2 W/kg 21 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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- Power density is too low: pressure difference pressure difference must be increased must be increased considerably considerably - Simple model + measurements show that TTE is not suitable for the show that TTE is not suitable for the current size MAV current size MAV Concept I, Tesla Turbine Engine: conclusions 22 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Concept II: Otto Engine 23 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Concept II, Otto Engine: combining 3 models Catalytic Reaction HeatLoss Exhaust Flow ++ 24 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Catalytic Reaction: model 25 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS Drop on a catalytic surface Similar conditions as during experiments Energy Balance:

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Catalytic Reaction: model [1] A.J.H. Meskers. High energy density micro-actuation based on gas generation by means of catalyst of liquid chemical energy. Masters thesis, TU Delft, 2010. 26 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Catalytic Reaction: high fuel concentrations 27 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Exhaust Flow: model Compressible flow through a round nozzle round nozzle Based on momentum equation 28 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Heat transfer Heat is transferred via -conduction-convection-radiation 29 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Concept II, Otto Engine: combining models + + = - Dealing with model uncertainties: 30 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Otto Engine: observations -Reaction times are fast enough -Trade off for fuel used per cycle -Condensation in cylinder 31 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Concept II, Otto Engine: Results - Model shows performance above the current requirements of the the current requirements of the MAV (125 W/kg @ 5% efficiency) MAV (125 W/kg @ 5% efficiency) 32 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Concept II, Otto Engine: considerations - Model neglects: - fluid leakage through cylinder/piston gap - fluid friction at exhaust - fuel delivery system - Condensation in cylinder problem needs to be addressed needs to be addressed 33 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Concept III: Hot Air Engine 34 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Concept III, Hot Air Engine: models ++ Catalytic Reaction HeatLoss Heat Reservoir s 35 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Concept III, Hot Air Engine: Catalytic Reaction Constant temperature Mass balance 36 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Concept III, Hot Air Engine: Heat Reservoirs Schemati c Under reversible conditions Estimate for heat transfer rates - Using definition Fouriers law Fouriers law -Optimistic and pessimistic value pessimistic value 37 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Model Results Resulting performance of model ++= 38 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Considerations for Small Scale Hot Air Engine - Model neglects losses of - fluid flow between piston cylinder gap - heat leakage of Decomposition Unit to the working fluid the working fluid 39 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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Conclusions for Small Scale Hot Air Engine - Heat transfer is not yet fast enough on this scale, which results in low on this scale, which results in low performance performance 40 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS - Concept III is not suited for the MAV

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Overall Conclusions - Of the considered possibilities, the small scale Otto engine is the best small scale Otto engine is the best option for the MAV: option for the MAV: Power density at 5% efficiency: Concept 1: << 2 W/kg Concept 2: 245 – 440 W/kg Concept 3: 0.5 – 8 W/kg 41 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS

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42 MOTIVATIONS - CONCEPTS - PERFORMANCE I / II / III - CONCLUSIONS Overall Conclusions Actual implementation of concept II requires more detailed analysis: - Solving the fluid leakage problem - Fuel pump -Exhaust port -Condensation

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Thank You!

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44 DETAILED SLIDES Detailed slides

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16 PERFORMANCE Scaling? Engine 1 S = 1 L = 10 A = 10 V = 10 Engine 2 S = 0.5 L = 5 A = 2.5 V = 1.25 Scaling factor LengthAreaVolume

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6 PREMILAIRY RESEARCH Approach of others?

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7 PREMILAIRY REASEARCH Possibilities

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40 PERFORMANCE Power Efficiency Pressure difference Length of belts (radius of disks) Height of gap (spacing between disks)

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7 CONCEPTS Energy flow in concepts Carnot cycle =

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8 PERFORMANCE Carnot Cycle zero power output!

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9 PERFORMANCE Curzon Ahlborn Cycle

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10 PERFORMANCE Curzon Ahlborn Cycle

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11 PERFORMANCE ND Curzon Ahlborn Cycle

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17 PERFORMANCE Basic thermodynamic engine model - Two constant temperature reservoirs: reservoirs: - Energy flows modeled with Fouriers law of heat conduction: Fouriers law of heat conduction: -Carnot cycle between the working fluid temperatures: working fluid temperatures:

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ND Curzon Ahlborn Cycle 18 PERFORMANCE

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19 PERFORMANCE Scaling of performance

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20 PERFORMANCE Intermediate Conclusions - Efficiency of engine is independent of scale, if the cycle time is adjusted correctly scale, if the cycle time is adjusted correctly - Optimal power output can be found by finding the optimal cycle time finding the optimal cycle time - Assuming an optimal engine configuration:

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12 PERFORMANCE Energy Balance Model

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13 PERFORMANCE

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14 PERFORMANCE Energy Balance Model

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13 PERFORMANCE Scaling of optimal cycle time concept 3 opti pessi

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16 DETAILS Heat transfer - Heat is transferred via -conduction-convection-radiation - FEM model in COMSOL

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Heat transfer: FEM model results 16 DETAILS

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Heat transfer: facts for MAV engine - Low Biot number situations: not much use for insulation. for insulation. - Difficult to maintain a temperature difference within the system difference within the system - Loss term scaling exponent = 1.5

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Intermediate Conclusions 15 PERFORMANCE - The performance of depends on a potential and the utilization potential and the utilization - Utilization is independent of scale - How does this apply to the concepts?

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16 DETAILS Catalytic Reaction: fundamentals - Decomposition rate proportional to the effective contact area between fuel and effective contact area between fuel and catalyst catalyst - Large Damköhler number: rate temperature independent temperature independent - First order reaction:

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32 DETAILS Exhaust Flow: model Flow through a nozzle nozzle Based on momentum equation Neglects friction

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Exhaust Flow: characteristics 33 DETAILS

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Model Results: scaling 24 PERFORMANCE Assumingunrestricted cycle time!

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41 PERFORMANCE What about scaling? Catalytic Reaction: Fluid Flow: Power Density at reference scale (S=1): Power: Power Density: Power: Power Density: Power Density when size is 10 times smaller (S=0.1):

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