Transcript MSD_2012_003_-_Wageningen-van_-_MSc_

DESIGN ANALYSIS
for a
SMALL SCALE ENGINE
by Tim van Wageningen
Contents
-
Motivation
Concepts
Performance Analysis
Conclusions
Questions
±40 min
2 MOTIVATIONS -
CONCEPTS
–
PERFORMANCE I / II / III
-
CONCLUSIONS
Nature
small
large
scale →
Atalanta
project
3 MOTIVATIONS -
Technology
CONCEPTS
–
PERFORMANCE I / II / III
-
CONCLUSIONS
Micro Air Vehicle
MAV
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
- 6 minutes of flight time with
5% efficiency
4 MOTIVATIONS -
CONCEPTS
–
PERFORMANCE I / II / III
-
CONCLUSIONS
MAV in Action
5 MOTIVATIONS -
CONCEPTS
–
PERFORMANCE I / II / III
-
CONCLUSIONS
Hydrogen Peroxide
- Master thesis of Arjan Meskers at the PME
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
Catalytic Reaction in Action
7 MOTIVATIONS -
CONCEPTS
–
PERFORMANCE I / II / III
-
CONCLUSIONS
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
Possibilities
9
MOTIVATIONS
- CONCEPTS -
PERFORMANCE I / II / III
-
CONCLUSIONS
3 different approaches
Turbine
+
Piston Cylinder
+
+
+
10
MOTIVATIONS
- CONCEPTS -
+
PERFORMANCE I / II / III
-
CONCLUSIONS
Concept I: Tesla Turbine Engine
+ Easy implementation
+
+ Theory of Tesla Turbine
predicts good efficiency at
small scale
+
- Conversion from rotation
to linear motion
11
MOTIVATIONS
- CONCEPTS -
PERFORMANCE I / II / III
-
CONCLUSIONS
Concept I: Tesla Turbine Engine
+
+
12
MOTIVATIONS
- CONCEPTS -
PERFORMANCE I / II / III
-
CONCLUSIONS
Concept II: Otto Engine
+ Proven concept on regular
scale
+
- Projects in literature show
bad performance because of
fluid leakage problem
- Implementation difficult
13
MOTIVATIONS
- CONCEPTS -
PERFORMANCE I / II / III
-
CONCLUSIONS
Concept II: Otto engine
+
14
MOTIVATIONS
- CONCEPTS -
PERFORMANCE I / II / III
-
CONCLUSIONS
Concept III: Hot Air Engine
+ Easy implementation
+
+
+ Promising scaling aspects
because heat transfer is more
effective
- Poor performance on regular
scale
15
MOTIVATIONS
- CONCEPTS –
PERFORMANCE I / II / III
-
CONCLUSIONS
Concept III: Hot Air Engine
+
+
16
MOTIVATIONS
- CONCEPTS -
PERFORMANCE I / II / III
-
CONCLUSIONS
Performance
- What influences the performance of
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
Concept I: Tesla Turbine Engine
18
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
Concept I: Tesla Turbine Engine:
model
Assumptions:
Laminar flow
No entrance effects
Incompressible fluid
19
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
Power
Pressure difference
Length of belts
(radius of discs)
Height of gap
(spacing between discs)
20
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
Efficiency
Measurements with small scale Tesla
turbines
Pressure difference:
~20 kPa
Measured Performance
45 mW
18% efficiency
Estimated power density:
2 W/kg
[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.
21
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
Concept I, Tesla Turbine Engine:
conclusions
- Power density is too low:
pressure difference
must be increased
considerably
- Simple model + measurements
show that TTE is not suitable for the
current size MAV
22
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
Concept II: Otto Engine
23
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
Concept II, Otto Engine:
combining 3 models
Catalytic
Reaction
24
MOTIVATIONS
-
CONCEPTS
+
Exhaust
Flow
- PERFORMANCE I / II / III -
CONCLUSIONS
+
Heat
Loss
Catalytic Reaction: model
Drop on a catalytic
surface
Similar conditions as during
experiments
Energy Balance:
25
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
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
Catalytic Reaction: high fuel
concentrations
27
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
Exhaust Flow: model
Compressible
flow through a
round nozzle
Based on
momentum
equation
28
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
Heat transfer
Heat is transferred via
-conduction
-convection
-radiation
29
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
Concept II, Otto Engine:
combining models
+
+
=
- Dealing with model uncertainties:
30
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
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
Concept II, Otto Engine:
Results
- Model shows performance above
the current requirements of the
MAV (125 W/kg @ 5% efficiency)
32
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
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
33
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
Concept III: Hot Air Engine
34
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
Concept III, Hot Air Engine:
models
Catalytic
Reaction
Heat
Reservoirs
+
35
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
Heat
Loss
+
CONCLUSIONS
Concept III, Hot Air Engine:
Catalytic Reaction
Constant temperature
Mass balance
36
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
Concept III, Hot Air Engine:
Heat Reservoirs
Schematic
Under reversible
conditions
Estimate for heat
transfer rates
- Using definition
Fouriers law
-Optimistic and
pessimistic value
37
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
Model Results
+
+
=
Resulting performance of model
38
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
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
39
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
Conclusions for
Small Scale Hot Air Engine
- Heat transfer is not yet fast enough
on this scale, which results in low
performance
- Concept III is not suited for the MAV
40
MOTIVATIONS
-
CONCEPTS
- PERFORMANCE I / II / III -
CONCLUSIONS
Overall Conclusions
- Of the considered possibilities, the
small scale Otto engine is the best
option for the MAV:
Power density at 5% efficiency:
Concept 1:
Concept 2:
Concept 3:
41
MOTIVATIONS
-
CONCEPTS
-
PERFORMANCE I / II / III
<< 2
W/kg
245 – 440 W/kg
0.5 – 8
W/kg
- CONCLUSIONS
Overall Conclusions
Actual implementation
of concept II requires
more detailed analysis:
- Solving the fluid
leakage problem
- Fuel pump
-Exhaust port
-Condensation
42
MOTIVATIONS
-
CONCEPTS
-
PERFORMANCE I / II / III
- CONCLUSIONS
Thank
You!
43
MOTIVATIONS
-
CONCEPTS
-
PERFORMANCE I / II / III
-
CONCLUSIONS
- END
Detailed
slides
44 DETAILED SLIDES
Scaling?
Scaling factor
Length
Area
Volume
16 PERFORMANCE
Engine 1
S=1
L = 10
A = 10
V = 10
Engine 2
S = 0.5
L=5
A = 2.5
V = 1.25
Approach of others?
6 PREMILAIRY RESEARCH
Possibilities
7 PREMILAIRY REASEARCH
Power
Pressure difference
Length of belts
(radius of disks)
Height of gap
(spacing between disks)
40 PERFORMANCE
Efficiency
Energy flow in concepts
Carnot cycle =
7 CONCEPTS
Carnot Cycle
zero power output!
8 PERFORMANCE
Curzon Ahlborn Cycle
9 PERFORMANCE
Curzon Ahlborn Cycle
10 PERFORMANCE
ND Curzon Ahlborn Cycle
11 PERFORMANCE
Basic thermodynamic engine model
- Two constant temperature
reservoirs:
- Energy flows modeled with
Fouriers law of heat conduction:
-Carnot cycle between the
working fluid temperatures:
17 PERFORMANCE
ND Curzon Ahlborn Cycle
18 PERFORMANCE
Scaling of performance
19 PERFORMANCE
Intermediate Conclusions
- Efficiency of engine is independent of
scale, if the cycle time is adjusted correctly
- Optimal power output can be found by
finding the optimal cycle time
- Assuming an optimal engine configuration:
20 PERFORMANCE
Energy Balance Model
12 PERFORMANCE
Energy Balance Model
13 PERFORMANCE
Energy Balance Model
14 PERFORMANCE
Scaling of optimal cycle time concept 3
pessi
opti
13 PERFORMANCE
Heat transfer
- Heat is transferred via
-conduction
-convection
-radiation
- FEM model in COMSOL
16 DETAILS
Heat transfer: FEM model results
16 DETAILS
Heat transfer: facts for MAV engine
- Low Biot number situations: not much use
for insulation.
- Difficult to maintain a temperature
difference within the system
- Loss term scaling exponent = 1.5
16 DETAILS
Intermediate Conclusions
- The performance of depends on a
potential and the utilization
- Utilization is independent of scale
- How does this apply to the concepts?
15 PERFORMANCE
Catalytic Reaction: fundamentals
- Decomposition rate proportional to the
effective contact area between fuel and
catalyst
- Large Damköhler number: rate
temperature independent
- First order reaction:
16 DETAILS
Exhaust Flow: model
Flow through a
nozzle
Based on
momentum
equation
Neglects friction
32 DETAILS
Exhaust Flow: characteristics
33 DETAILS
Model Results: scaling
Assuming
unrestricted
cycle time!
24 PERFORMANCE
What about scaling?
Catalytic Reaction:
Power:
Fluid Flow:
Power Density:
Power Density at reference scale (S=1):
Power Density when size is 10 times smaller (S=0.1):
41 PERFORMANCE