University of Southern California Dissertations and Theses

Effects of pressure on heat-recirculating combustors for micropropulsion applications

(USC Thesis Other)

Effects of pressure on heat-recirculating combustors for micropropulsion applications

PDF

Download

Open document

Flip pages

Download a page range

Download transcript

Copy asset link

Request this asset

Transcript (if available)

Content Eects of Pressure on Heat-Recirculating Combustors
for Micropropulsion Applications
by
Joseph A. Lyon
A Thesis Presented to the
Faculty of the USC Viterbi School of Engineering
University of Southern California
In Partial Fulllment of the Requirements for the Degree
Master of Science
(Astronautical Engineering)
May 2021
Copyright 2021 Joseph A. Lyon
Acknowledgements
I would rst like to thank my advisor, Dr. Paul Ronney, for his wealth of knowledge and the
privilege of working under his mentorship. I would like to express my sincere gratitude to
Dr. Dan Erwin and Dr. Keith Goodfellow for serving on my thesis committee. I would also
like to acknowledge the support from my Combustion Physics Lab colleagues, in particular,
Yang Shi, Zhenghong \Harris" Zhou, Fares Maimani and Patharapong \Winry" Bhuripanyo.
Finally, I would like to thank my parents and brother for their unconditional love and
encouragement from so far away.
ii
Table of Contents
Acknowledgements ii
List of Figures v
Abstract vi
Chapter 1: Introduction 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.1 Micropropulsion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.2 Combustion Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.3 Heat-Recirculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.4 Swiss Roll Combustor . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2.5 Swiss Roll Combustor Scaling Parameters . . . . . . . . . . . . . . . 6
1.2.6 Nitromethane Monopropellant . . . . . . . . . . . . . . . . . . . . . . 8
1.2.7 Pressure Eects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Chapter 2: Experimental Methods 11
2.1 Apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.1 Combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1.2 Pressure Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.1.3 Data Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Chapter 3: Results 21
3.1 Eects of Pressure on the Lean Extinction Limits . . . . . . . . . . . . . . . 23
3.2 Temperature at the Lean Extinction Limits . . . . . . . . . . . . . . . . . . 24
Chapter 4: Conclusion 25
4.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
iii
References 27
Appendices 28
iv
List of Figures
1.1 Chemical Rocket Propulsion System. . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Swiss Roll Heat-Recirculating Combustor Schematic Diagram. . . . . . . . . 5
1.3 Computed extinction limits at dierent Swiss roll combustor scales without
constant , Da, and R. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4 Computed extinction limits at dierent Swiss roll combustor scales with con-
stant , Da, and R. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1 Experimental Setup Schematic Diagram. . . . . . . . . . . . . . . . . . . . . 12
2.2 3.5 turn, maraging steel, Swiss roll combustor with 70 mm diameter, 49 mm
wall height, 3 mm channel width and 0.6 mm wall thickness. . . . . . . . . . 13
2.3 CAD Model Section View of the Swiss Roll Combustor. . . . . . . . . . . . . 13
2.4 Insulated Swiss Roll Combustor Test Stand. . . . . . . . . . . . . . . . . . . 14
2.5 Igniter and Thermocouple Ceramic Rods . . . . . . . . . . . . . . . . . . . . 15
2.6 Flashback Arrestor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.7 Aluminum Vacuum Chamber. . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.8 Vacuum Chamber Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.9 Welch 1376 Vacuum Pump. . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.10 Cold Trap Submerged in Ice Bath . . . . . . . . . . . . . . . . . . . . . . . . 18
2.11 Swiss Roll Combustor in Vacuum Chamber . . . . . . . . . . . . . . . . . . . 19
3.1 Comparison of the lean extinction limits at 1 atm . . . . . . . . . . . . . . . 22
3.2 Lean extinction limit map for pressures of 1 atm, 2 atm and 3 atm. . . . . . 23
3.3 Lean extinction limit temperatures for pressures of 1 atm, 2 atm and 3 atm. 24
A.1 LabVIEW Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
v
Abstract
Advancements in the eld of micro-electromechanical system (MEMS) technology are trans-
forming the space industry. Small satellites operating in swarms now replace traditional,
large satellites. However, scaling down the propulsion system, specically the combustor,
is not a feasible method because of the rise in heat losses from the increased surface area
to volume ratio. Heat-recirculation can be employed to overcome these heat losses. This
study investigated the eects of pressure on the Swiss roll heat-recirculating combustor. The
objective was to provide insight into how pressure eects the Swiss roll combustor physical
scaling trends established in literature. Additionally, the feasibility of utilizing the Swiss roll
combustor in a low pressure, nitromethane, monopropellant application was explored.
An apparatus was constructed to analyze the Swiss roll combustor performance inside a
vacuum chamber from 0.3 atm to 3 atm. Previous studies on Swiss roll combustors have only
been performed at atmospheric pressure. Tests were conducted on the Swiss roll combustor
at super-atmospheric pressures from 1 atm to 3 atm across a range of Reynolds number
from 100 to 1000. Results indicated that increased pressure was not benecial to combustor
performance, in terms of the lean extinction limits compared to 1 atm. The Swiss roll
combustor experienced reduced lean extinction limits from 1 atm to 2 atm and expanded
lean extinction limits from 2 atm to 3 atm. Interestingly, the lean extinction limit trend at
3 atm suggests the Swiss roll combustor may experience improved performance beyond this
pressure. Further testing at sub-atmospheric pressures is needed before comparisons can be
made to the Swiss roll combustor physical scaling trends and nitromethane monopropellant
application.
vi
Chapter 1: Introduction
1.1 Motivation
Micro-electromechanical system (MEMS) technology is transforming the space industry.
Small satellites now operate in groups of hundreds, known as swarms, to complete highly
complex tasks traditionally carried out by single, large, costly satellites [1]. These devices
are implemented as robotic, re-congurable, autonomous systems, that overlap in instru-
mentation to allow for distributed functionality [2]. Satellites can work together to assemble
constellations,
y in formation, and execute intricate in-space construction [3]. These satel-
lites are lighter, smaller, and overall less expensive than their predecessors, yet collectively
more functional [4]. They oer platforms for intelligent navigation, communication, devel-
opment and Earth observation not previously aordable [4]. In addition, swarms inherently
oer redundancy, increasing reliability and
exibility in completing mission objectives should
individual satellites fail. The economic benets of utilizing small satellites include the re-
duction in launch and life-cycle costs, and the potential for mass production [1].
The miniaturization of satellites however, introduces unique system constraints on mass,
power and volume. The propulsion system becomes the critical area of design, as small
satellites require minute and accurate thrust generation to ensure precise maneuvering [5].
Depending on the mission requirements, a single satellite may provide a range of thrust
levels on the order of micronewton (N) to newton (N) with a high thrust eciency and low
1
thruster mass (<1 kg) [2]. This is a major obstacle that must be addressed to foster the
wide-scale implementation of small satellites.
1.2 Background
1.2.1 Micropropulsion
The principal theory of rocket propulsion is the ejection of propellant at high velocity [6].
Chemical rockets are characterized by the release of energy through combustion of a fuel-
oxidizer mixture. A typical chemical rocket propulsion system consists of a propellant tank
and feed system, combustion chamber, and exhaust nozzle [7]. The propellant tank and
feed system are responsible for the storage and distribution of propellant to the combustion
chamber. The propellant is heated and burns in the combustion chamber, producing high
temperature gases. These hot gases are expanded through the exhaust nozzle at high speed
to produce thrust.
Figure 1.1: A typical chemical rocket propulsion system.
Micropropulsion, as dened by Micci and Ketsdever [1], is the propulsion system appli-
cable to a microsatellite, any satellite with a mass less than 100 kg. Likewise, combustion
2
at small scales is known as microcombustion. The dening prex for combustor size is gen-
erally related to the physical dimensions of the combustor. The term microscale combustor
is used for a combustor physical length scale of less than 1 mm, mesoscale between 1 mm
and 1 cm and macroscale for greater than 1 cm [8]. However, the term microcombustor, is
widely accepted for any combustor suitable for a microsatellite and is referred to as such in
this study. Utilization of the high energy density of hydrocarbon fuels is the incentive for
microcombustion [9]. The chemical energy harnessed from hydrocarbon fuels can be used to
provide thrust for micropropulsion devices.
1.2.2 Combustion Fundamentals
Combustion is a chemical process involving an exothermic reaction between a fuel and ox-
idizer. The reaction generates exhaust products and heat. A stoichiometric mixture is the
ideal fuel-oxidizer ratio in which the fuel and oxidizer are completely consumed during the
reaction. The chemical equation for stoichiometric propane-air, the combustion mixture used
in this study, is:
C
3
H
8
+ 5 (O
2
+ 3.76 N
2
)! 3 CO
2
+ 4 H
2
O + 18.8 N
2
The equivalence ratio, , is a useful parameter to quantify deviation from a stoichiometric
mixture. is dened as the ratio of the actual fuel-oxidizer ratio to the stoichiometric
fuel-oxidizer ratio.
=

Fuel
Oxidizer

actual

Fuel
Oxidizer

stoichiometric
A less than 1 is dened as a fuel-lean mixture. A equal to 1 is dened as a stoichiometric
mixture. A greater than 1 is dened as a fuel-rich mixture.
Boundaries exist, known as the extinction limits, that render a combustion mixture non-

ammable after ample dilution with excess oxidizer or fuel [10]. Lean and rich extinction
3
limits can be empirically determined for a fuel-oxidizer mixture at a given temperature and
pressure. It is vital to understand these extinction limits for the purpose of improving
combustion eciency and emissions.
1.2.3 Heat-Recirculation
Simply scaling down the size of the combustion chamber is not a feasible method for develop-
ing a micropropulsion device. The main challenge to overcome is the rise in heat losses caused
by the increased surface area to volume ratio [11]. As the combustor is scaled down, heat
losses eventually dominate heat generation, thus
ame extinction occurs. Methods that exist
for overcoming
ame extinction limits include catalysis and improving thermal management.
Heat-recirculation uses the energy released from combustion products to preheat reactants
[12]. This was rst proposed by Weinberg [12] and is the specic method implemented in
this study.
Heat-recirculating microcombustors have previously been employed in several micro-
propulsion experiments. Yetter et al. [13] utilized an asymmetrical whirl combustor for
use with a liquid monopropellant microthruster. The combustor geometry allowed liquid
propellant to be tangentially injected into the combustion chamber, while simultaneously
being heated by hot chamber walls and exhaust feedback. Herrault et al. [14] designed
and constructed a self-resonant, MEMS-fabricated, air breathing engine, which utilized its
pulsing exhaust to generate thrust. After an initial spark, high pressure combustion prod-
ucts vacate through both the air inlet and exhaust. As the pressure in the chamber drops
below atmospheric level, suction occurs, allowing fresh air, hot gas and radicals to re-enter
the chamber and re-ignite without a spark, as long as fuel is constantly supplied. Shirsat et
al. [15] developed a mesoscale, Swiss roll heat-recirculating thrust chamber for a methanol
and steam-oxygen mixture. The chamber utilized a spiral countercurrent heat exchanger to
preheat incoming reactants using the exhaust heat.
4
1.2.4 Swiss Roll Combustor
Numerous experiments have demonstrated the Swiss roll combustor to be the most sim-
ple and ecient geometric structure among heat-recirculating combustors. The Swiss roll
combustor is used in this study. The Swiss roll combustor is an appealing device because
it features no moving parts. It consists of a double spiral heat exchanger with a centrally
located combustion volume. Cold reactants are injected through a spiral inlet channel to the
center, where a reaction occurs. Hot combustion products exit through an adjacent spiral
channel, where heat is transferred to the cold reactants via the channel walls. As the tem-
perature of reactants is raised above its adiabatic temperature, the process is labeled \excess
enthalpy" or \super adiabatic" combustion [11]. This allows the Swiss roll combustor to
sustain operating conditions that would otherwise result in
ame quenching.
Figure 1.2: Schematic diagram of the Swiss roll heat-recirculating combustor.
Many studies have been conducted on Swiss roll combustors, largely for the purpose
of micropower generation applications. Ahn et al. [16] built a thermally self-sustaining
5
miniature power generation device, that utilized a solid oxide fuel cell placed inside a Swiss
roll combustor. Cho et al. [17] coupled a Swiss roll combustor with an external combustion
micro-heat engine, using a thermal switch to produce power. Numerical models simulating
combustion in Swiss roll combustors have been developed by Kuo and Ronney [18] and Chen
and Buckmaster [19]. No analysis however, has been conducted on Swiss roll combustors at
pressures other than 1 atm.
1.2.5 Swiss Roll Combustor Scaling Parameters
Understanding the physical scaling eects on a combustor allow for the ideal design and
selection of operating conditions. Chen and Ronney [20] studied the eects of size and
geometry to identify dimensionless parameters capable of quantifying the Swiss roll com-
bustor performance. They determined that the Reynolds number, Re, heat loss coecient,
, Damk ohler number, Da, and radiative transfer number, R, were suitable to predict the
performance of Swiss roll combustors with various physical sizes. By adjusting the material
properties and operating conditions of the Swiss roll combustor in their numerical model,
including the convective heat loss coecient, h, surface emissivity, , and pre-exponential
factor in Arrhenius reaction rate, Z, they were able obtain a constant , Da and R among
Swiss roll combustors of similar geometry, but dierent sizes. The lean extinction limits
and maximum temperatures at the extinction limit were almost identical across these scaled
Swiss roll combustors. Figure 1.3 shows the computed extinction limits of the Swiss roll
combustor without the material properties adjusted to achieve constant, Da and R. Figure
1.4 shows the computed extinction limits of the Swiss roll combustor after the material prop-
erties have been adjusted [20]. Full, refers to the nominal-scale Swiss roll combustor used
that was 5 cm tall with a channel width of 2.5 mm and wall thickness of 0.5 mm. Double,
refers to an identical device with the height raised to 10 cm. Half, refers to an identical
device with the height cut to 2.85 cm. These scaling trends were established for Swiss roll
6
combustor performance at 1 atm, but the eects of pressure on these trends have not been
examined.
Figure 1.3: Computed extinction limits at dierent Swiss roll combustor scales without
constant , Da, and R [20].
Figure 1.4: Computed extinction limits at dierent Swiss roll combustor scales with constant
, Da, and R [20].
7
1.2.6 Nitromethane Monopropellant
Liquid rocket propulsion systems are categorized as either a bipropellant or monopropellant
system. A bipropellant system utilizes a separate fuel and oxidizer to generate propulsion.
A monopropellant system utilizes the chemical decomposition of a single chemical to gener-
ate propulsion. The most commonly used monopropellant is hydrazine (N
2
H
4
), for its high
specic impulse, I
sp
, the common measure of eciency for a rocket engine. However, hy-
drazine is extremely toxic and requires extensive safe handling procedures, therefore \green"
alternatives must be considered.
A desirable alternative to hydrazine is nitromethane (CH
3
NO
2
). Nitromethane oers
improved I
sp
, by approximately 15.7 seconds [21]. In addition, nitromethane is non-toxic
and stable at 1 atm. However, one drawback to using nitromethane is that it does not ignite
readily at room temperature and low pressures, thus requiring a need for heat-recirculation.
Notably, Yetter et al. [13] found that combustion of nitromethane was achievable at high
pressures, beginning at 150 psig (11 atm) with pressures of 350 psig (25 atm) required
for complete combustion. They also found that combustion of nitromethane could be self-
sustained at low pressure by adding a small amount of oxygen. Both these ndings were
attributed to the enhancement of nitromethane kinetic rates of reaction with increased pres-
sure or the addition of oxygen. The vapor pressure of nitromethane is approximately 4.79
kPa (0.05 atm) at the average temperature of a satellite structure, 25°C [22]. This study
aims to utilize nitromethane at its vapor pressure. While nitromethane monopropellant is
of interest for this research, propane-air is used in the experimentation for its simplicity and
comparison to previous Swiss roll combustor experiments.
The use of a monopropellant and low combustion chamber pressure oers several ad-
vantages for a small satellite. There is a reduction in satellite size, complexity, power and
number of components, as conventional thrusters require an additional storage tank and
8
pressurization system, to feed propellant to the combustion chamber. In addition, the low
chamber pressure ensures all of the liquid propellant is utilized through vacuum evaporation.
1.2.7 Pressure Eects
The eects of pressure on macroscale combustion chamber performance have been widely
documented in literature. However, few studies have examined the specic eects of pres-
sure in microcombustion applications. Wan et al. [23] examined the extinction limits of
methane-air
ames in a mesoscale cavity-combustor, at pressures ranging from 1 atm to 3
atm. They found that the reaction intensity in the combustor increased with pressure, which
is advantageous for
ame stability. However, the eect of
ame stretching was augmented
at higher pressures, which was harmful to
ame stability. Their ndings showed that these
phenomena competed with one another, the extinction limits increased from 1 atm to 2 atm,
but decreased from 2 atm to 3 atm. Tsuboi et al. Numerically and experimentally, [24]
investigated the extinction characteristics of premixed methane-air
ames in an externally
heated mesoscale channel at pressures of 0.05 atm to 0.2 atm. Their results showed that at
low pressure conditions, the maximum upper extinction limits were located at the fuel-leaner
side, asymmetric to the stoichiometric ratio. Karagiannidis et al. [25] numerically investi-
gated the start-up performance of methane-fueled catalytic microreactors. They concluded
that increasing the reactor operating pressure from 1 bar to 5 bar (0.99 atm to 4.95 atm),
greatly enhanced the platinum catalyst, resulting in a substantial decrease in ignition and
steady state time. The eects of varying pressure on Swiss roll combustors have not been
previously reported.
1.3 Scope
The objective of this work is to investigate the eects of pressure on the Swiss roll heat-
recirculating combustor. Previous studies on the device [16{20] have been conducted at an
9
ambient pressure of 1 atm. This research aims to reveal conditions that yield the greatest
amount of energy from combustion using the Swiss roll combustor, ideally, without the
need for catalysis or excessive pre-heating. The experiment will provide insight into the
eects of pressure on the Swiss roll combustor scaling trends developed by Chen and Ronney
[20] and determine the feasibility of utilizing the Swiss roll combustor for a low pressure,
nitromethane, monopropellant application.
10
Chapter 2: Experimental Methods
2.1 Apparatus
An apparatus was constructed to analyze the Swiss roll combustor performance inside a
vacuum chamber capable of operating at pressures from 0.3 atm to 3 atm. Propane and air,
supplied by compressed gas cylinders, served as the fuel and oxidizer respectively. The
ow of
the mixture was controlled using Digital 300 Series
ow controllers from Teledyne Hastings,
with an accuracy of 0.2% full scale + 0.5% of the reading. Temperature was measured at
the center of the combustor with a Type K thermocouple from Omega Engineering, capable
of reading from -200° to 1250°C at the greater of 2.2°C or 0.75% of the reading. Pressure
in the vacuum chamber was measured using a PX5500 pressure transducer from Omega
Engineering, capable of reading from 0 psia to 100 psia (0 atm to 6.8 atm) at an accuracy
of 0.1% of the full-scale output. LabVIEW data acquisition software was used to acquire
temperature and pressure data and operate the mass
ow controllers. The laboratory setup
of the experiment is shown in Figure 2.1.
11
Figure 2.1: Schematic diagram of the experimental setup.
12
2.1.1 Combustion
Swiss roll combustor experiments have been performed in the past with congurations of
the device itself including material, number of turns and height. Ronney [11] analyzed these
physical characteristics. For this study, a 3.5 turn, additively manufactured, maraging steel,
Swiss roll combustor with 70 mm total diameter, 49 mm wall height, 3 mm channel width and
0.6 mm wall thickness was used. The device is shown in Figure 2.2 with the corresponding
CAD model section view in Figure 2.3.
Figure 2.2: 3.5 turn, maraging steel, Swiss roll combustor with 70 mm diameter, 49 mm
wall height, 3 mm channel width and 0.6 mm wall thickness.
Figure 2.3: Swiss roll combustor CAD model with the top exposed to display the inner
channels.
13
To mitigate the detrimental eect of heat losses outward from the spiral plane to the
ambient environment, the Swiss roll combustor was insulated with ceramic ber wool from
Morgan Advanced Materials and ceramic ber board from Lynn Manufacturing, Inc. A
thermocouple and igniter housed in separate ceramic rods were inserted through holes in the
top and bottom of the Swiss roll combustor.
Figure 2.4: Insulated Swiss roll combustor test stand.
To seal the thermocouple and igniter openings, Ceramabond™ 552, alumina lled ceramic
adhesive from Aremco Products, Inc was used. A 24-gauge, Nickel Chromium, coiled, resis-
tance wire connected to a variable power supply was used to provide initial
ame ignition.
Ceramic connectors, berglass insulated thermocouple extension wire and enameled copper
wire were used for wiring within the chamber to withstand elevated temperatures. A
ash-
back arrestor from SGD, Inc was employed on the propane-air line near the entrance to the
vacuum chamber to stop a reverse
ame or gas
ow back to the supply.
14
Figure 2.5: Igniter [left] and thermocouple [right] ceramic rods inserted through openings
in the top and bottom of the Swiss roll combustor.
Figure 2.6: Flashback arrestor used on the propane-air line to stop a reverse
ame or gas

ow back to the supply.
15
2.1.2 Pressure Control
Experiments were conducted inside an aluminum vacuum chamber with a height of 0.6 m and
diameter of 0.3 m capable of supporting both sub-atmospheric and super-atmospheric testing
conditions. Four lines on the side of the chamber were congured for a wire feedthrough, vent
valve to atmosphere,
uid feedthrough, and vacuum pump and nitrogen gas. The vacuum
pump and nitrogen gas shared the same line. The pressure transducer was connected via a
hole on the lid of the vacuum chamber.
Figure 2.7: Aluminum vacuum chamber.
16
Figure 2.8: Vacuum chamber lines. From top to bottom, wire feedthrough, atmospheric
vent valve,
uid feedthrough, and vacuum pump and nitrogen gas inlet.
Pressure within the chamber was controlled to within 0.01 atm by solenoid valves oper-
ating the vacuum pump and nitrogen gas lines. A belt-driven Welch 1376 vacuum pump was
used to decrease the chamber pressure. Nitrogen gas, supplied by a compressed gas cylinder,
was used to increase the chamber pressure. A cold trap from StonyLab submerged in an
ice water and salt slurry was implemented to condense unwanted exhaust vapors prior to
entering the vacuum pump.
17
Figure 2.9: Welch 1376 Vacuum Pump.
Figure 2.10: Cold trap submerged in an aluminum vessel ice bath.
18
2.1.3 Data Acquisition
LabVIEW data acquisition software was employed to set the target combustion and vacuum
chamber parameters, operate the mass
ow controllers and read temperature and pressure
measurements. A control box was constructed to house hardware, including a National
Instruments USB-6001 device, mass
ow controllers, solenoid valves, 12V DC power supply,
gas cylinder plumbing and control wiring.
Figure 2.11: Swiss roll combustor test stand installed in the vacuum chamber, window view
[left], overhead view [right].
19
2.2 Procedure
The lean extinction limits for the Swiss roll combustor were measured at pressures ranging
from 1 atm to 3 atm. Propane and air were premixed before entering the combustor. The
mixture was ignited using the resistance wire located at the center of the combustor. To
achieve ignition, a stronger mixture ( 1) was used. Once the
ame reached a stable
burning state, the igniter was turned o and the equivalence ratio was slowly reduced until
rapid extinction. The temperature at the center of the device and equivalence ratio just
before rapid extinction were recorded.
To maintain the setpoint pressure in the chamber, a simple \on-o" control loop was
implemented. As the pressure fell below the setpoint, the nitrogen gas line was opened
to compensate. Conversely, when the pressure rose above the setpoint, the vacuum pump
line was opened. The exhaust outlet of the Swiss roll combustor was intentionally directed
near the vacuum pump line to prioritize evacuation of combustion products. In addition,
the chamber was purged and relled with nitrogen gas after several trials to prevent the
unwanted buildup of combustion products.
20
Chapter 3: Results
Data was collected for high pressure conditions from 1 atm to 3 atm over a range of Re from
100 to 1000. The Re was dened based on the input
ow velocity, hydraulic diameter of
the Swiss roll combustor, and viscosity at room temperature and target pressure conditions.
The lean extinction limits were then mapped.
To establish a baseline, the lean extinction limits for a propane-air mixture at 1 atm for
the Swiss roll combustor in the vacuum chamber was compared to a previous study by Ahn
et al. [26] that utilized a similar Swiss roll combustor. The combustor used in Ahn et al. [26]
was square in shape and utilized two Inconel metal tabs rolled into two walls, in contrast
to the circular, maraging steel, 3D printed structure used in this study. The comparison
indicates reasonable agreement with the lean extinction curve shape. The current study also
indicates slightly improved performance in regards to the lean extinction limits.
21
Figure 3.1: Comparison of the lean extinction limits of a propane-air mixture at 1 atm with
similar Swiss roll combustor geometry.
22
3.1 Eects of Pressure on the Lean Extinction Limits
The lean extinction limits for high pressure conditions appeared to be non-monotonic in
nature, with a reduced extinction limit from 1 atm to 2 atm and expanded extinction limit
from 2 atm to 3 atm. The extinction limit trend at 3 atm suggests there may be improved
performance beyond this pressure. Both the 2 atm and 3 atm extinction curves display a
similar shape and Re extinction limits as the 1 atm curve.
Figure 3.2: Lean extinction limit map for pressures of 1 atm, 2 atm and 3 atm.
23
3.2 Temperature at the Lean Extinction Limits
The temperature at the lean extinction limits appears to trend linearly, with the measured
temperature decreasing with increased chamber pressure. The temperature just prior to

ame extinction was measured at the center of the Swiss roll combustor and is relative to
the
ame location. As such, these temperatures are not indicative of the actual or peak

ame temperature, as the location of the
ame may be o-center. The extinction limits of
the
ame were observed based on the rapid and sustained decline in temperature reading.
Figure 3.3: Lean extinction limit temperatures for pressures of 1 atm, 2 atm and 3 atm.
24
Chapter 4: Conclusion
4.1 Summary
This study investigated the eects of pressure on heat-recirculating Swiss roll combustors.
Previous published works implementing the Swiss roll combustor have only been performed
at atmospheric pressure. The constructed apparatus was capable of conducting experiments
on the Swiss roll combustor at pressures from 0.3 atm to 3 atm. Tests were conducted at
pressures from 1 atm to 3 atm. The ndings indicated that increased pressure was not ben-
ecial to combustor performance in terms of extending the lean extinction limits. The lean
extinction limits appeared to be non-monotonic in nature, with a reduced extinction limit
from 1 atm to 2 atm and an expanded extinction limit from 2 atm to 3 atm. Interestingly, the
extinction limit trend at 3 atm suggests the Swiss roll combustor may experience improved
performance beyond this pressure. The 2 atm and 3 atm extinction limit curves exhibited
similar shape and Re extinction limits to the 1 atm curve. The combustor temperatures
at the lean extinction limits for all three pressures appeared to behave linearly, with the
temperatures decreasing with increased pressure. Overall, varying pressures on the Swiss
roll combustor revealed notable lean extinction limit results.
25
4.2 Future Work
To provide a comprehensive overview of the eects of pressure on the Swiss roll combustor,
further investigation at both sub-atmospheric and super-atmospheric conditions is suggested.
Additional trials should be conducted with pressure values between 1 atm and 2 atm and
between 2 atm and 3 atm. As the experimental apparatus was constructed to operate at
a range of 0.3 atm to 3 atm, testing can be conducted at sub-atmospheric conditions. By
mapping the lean extinction limits over a range of pressures, the performance trend shift may
be more precisely determined. While the study was performed with a propane-air mixture to
compare with previous works, experimentation using nitromethane will be required. When
additional data is collected, comparisons can then be made to the scaling trends outlined by
Chen and Ronney [20] and insight provided into the feasibility of using heat-recirculation
for a nitromethane monopropellant system. This investigation into pressure eects on Swiss
roll combustors is benecial to future micropropulsion applications.
26
References
1. Ketsdever, A. D. & Micci, M. M. Micropropulsion for Small Spacecraft (American
Institute of Aeronautics and Astronautics, 2000).
2. Osiander, R., Darrin, M. A. G. & Champion, J. L. MEMS and Microstructures in
Aerospace Applications (CRC Press, 2018).
3. Wang, J. X. & Qian, X. M. Application and Development of MEMS in the Field of
Aerospace in Applied Mechanics and Materials 643 (2014), 72{76.
4. Levchenko, I., Bazaka, K., Ding, Y., Raitses, Y., Mazoure, S., Henning, T.,et al. Space
Micropropulsion Systems for Cubesats and Small Satellites: From Proximate Targets
to Furthermost Frontiers. Applied Physics Reviews 5, 011104 (2018).
5. You, Z.SpaceMicrosystemsandMicro/NanoSatellites (Butterworth-Heinemann, 2017).
6. Sutton, G. P. & Biblarz, O. Rocket Propulsion Elements (John Wiley & Sons, 2016).
7. Hill, P. G. & Peterson, C. R. Mechanics and Thermodynamics of Propulsion.aw (1992).
8. Ju, Y. & Maruta, K. Microscale Combustion: Technology Development and Fundamen-
tal Research. Progress in Energy and Combustion Science 37, 669{715 (2011).
9. Vijayan, V. & Gupta, A. Combustion and Heat Transfer at Meso-Scale with Thermal
Recuperation. Applied Energy 87, 2628{2639 (2010).
10. Law, C. K. Combustion Physics (Cambridge University Press, 2010).
11. Ronney, P. D. Heat-Recirculating Combustors.Microscale Combustion and Power Gen-
eration. Momentum Press LLC, New York, 287{320 (2015).
12. Weinberg, F. Combustion Temperatures: The Future? Nature 233, 239{241 (1971).
13. Yetter, R. A., Yang, V., Wu, M. H., Wang, Y., Milius, D., Aksay, I. A.,etal. Combustion
Issues and Approaches for Chemical Microthrusters. International Journal of Energetic
Materials and Chemical Propulsion 6 (2007).
14. Herrault, F., Crittenden, T., Yorish, S., Birdsell, E., Glezer, A. & Allen, M. G. A
Self-Resonant, MEMS-Fabricated, Air-Breathing Engine in Proc. Solid-State Sensors,
Actuators and Microsystems Workshop (2008), 348{51.
15. Shirsat, V. & Gupta, A. Extinction, Discharge, and Thrust Characteristics of Methanol
Fueled Meso-Scale Thrust Chamber. Applied Energy 103, 375{392 (2013).
16. Ahn, J., Ronney, P. D., Shao, Z. & Haile, S. M. A Thermally Self-Sustaining Miniature
Solid Oxide Fuel Cell. Journal of Fuel Cell Science and Technology 6 (2009).
17. Cho, J.-H., Lin, C. S., Richards, C. D., Richards, R. F., Ahn, J. & Ronney, P. D. Demon-
stration of an External Combustion Micro-Heat Engine. Proceedings of the Combustion
Institute 32, 3099{3105 (2009).
18. Kuo, C. & Ronney, P. D. Numerical Modeling of Non-Adiabatic Heat-Recirculating
Combustors. Proceedings of the Combustion Institute 31, 3277{3284 (2007).
27
19. Chen, M. & Buckmaster, J. Modelling of Combustion and Heat Transfer in Swiss Roll
Micro-Scale Combustors. Combustion Theory and Modelling 8, 701{720 (2004).
20. Chen, C.-H. & Ronney, P. D. Scale and Geometry Eects on Heat-Recirculating Com-
bustors. Combustion Theory and Modelling 17, 888{905 (2013).
21. Boyer, J. E. & Kuo, K. K. Combustion Behavior and Flame Structure of Nitromethane.
International Journal of Energetic Materials and Chemical Propulsion 6 (2007).
22. Lide, D. R. CRC Handbook of Chemistry and Physics (CRC Press, 2004).
23. Wan, J., Fan, A., Yao, H. & Liu, W. Eect of Pressure on the Blow-O Limits of Pre-
mixed CH4/Air Flames in a Mesoscale Cavity-Combustor. Energy 91, 102{109 (2015).
24. Tsuboi, Y., Yokomori, T. & Maruta, K. Extinction Characteristics of Premixed Flame
in Heated Microchannel at Reduced Pressures. Combustion Science and Technology
180, 2029{2045 (2008).
25. Karagiannidis, S. & Mantzaras, J. Numerical Investigation on the Start-Up of Methane-
Fueled Catalytic Microreactors. Combustion and Flame 157, 1400{1413 (2010).
26. Ahn, J., Eastwood, C., Sitzki, L. & Ronney, P. D. Gas-Phase and Catalytic Combustion
in Heat-Recirculating Burners. Proceedings of the Combustion Institute 30, 2463{2472
(2005).
28
Appendices
Figure A.1: The LabVIEW Front Panel used to set target Reynolds number, equivalence
ratio and chamber pressure, operate mass
ow controllers and read temperature and pressure
measurements.
29

Abstract (if available)

Abstract Advancements in the field of micro-electromechanical system (MEMS) technology are transforming the space industry. Small satellites operating in swarms now replace traditional, large satellites. However, scaling down the propulsion system, specifically the combustor, is not a feasible method because of the rise in heat losses from the increased surface area to volume ratio. Heat-recirculation can be employed to overcome these heat losses. This study investigated the effects of pressure on the Swiss roll heat-recirculating combustor. The objective was to provide insight into how pressure effects the Swiss roll combustor physical scaling trends established in literature. Additionally, the feasibility of utilizing the Swiss roll combustor in a low pressure, nitromethane, monopropellant application was explored. An apparatus was constructed to analyze the Swiss roll combustor performance inside a vacuum chamber from 0.3 atm to 3 atm. Previous studies on Swiss roll combustors have only been performed at atmospheric pressure. Tests were conducted on the Swiss roll combustor at super-atmospheric pressures from 1 atm to 3 atm across a range of Reynolds number from 100 to 1000. Results indicated that increased pressure was not beneficial to combustor performance, in terms of the lean extinction limits compared to 1 atm. The Swiss roll combustor experienced reduced lean extinction limits from 1 atm to 2 atm and expanded lean extinction limits from 2 atm to 3 atm. Interestingly, the lean extinction limit trend at 3 atm suggests the Swiss roll combustor may experience improved performance beyond this pressure. Further testing at sub-atmospheric pressures is needed before comparisons can be made to the Swiss roll combustor physical scaling trends and nitromethane monopropellant application.

Linked assets

University of Southern California Dissertations and Theses

Conceptually similar

PDF

Experimental and numerical analysis of radiation effects in heat re-circulating combustors

PDF

Studies of Swiss-roll combustors for incineration and reforming applications

PDF

Hydrogen peroxide vapor for small satellite propulsion

PDF

Pressure effects on C₁-C₂ hydrocarbon laminar flames

PDF

Performance analysis and flowfield characterization of secondary injection thrust vector control (SITVC) for a 2DCD nozzle

PDF

High temperature latent heat thermal energy storage to augment solar thermal propulsion for microsatellites

PDF

Cooperative localization of a compact spacecraft group using computer vision

PDF

A study of ignition effects on thruster performance of a multi-electrode capillary discharge using visible emission spectroscopy diagnostics

PDF

Reduction of large set data transmission using algorithmically corrected model-based techniques for bandwidth efficiency

PDF

Impacts of heat mitigation strategies and pollutant transport on climate and air quality from urban to global scales

PDF

An experimental investigation of cathode erosion in high current magnetoplasmadynamic arc discharges

PDF

An analytical and experimental study of evolving 3D deformation fields using vision-based approaches

PDF

Relative-motion trajectory generation and maintenance for multi-spacecraft swarms

PDF

Experimental and kinetic modeling studies of flames of H₂, CO, and C₁-C₄ hydrocarbons

PDF

Development and applications of a body-force propulsor model for high-fidelity CFD

PDF

Techniques for analysis and design of temporary capture and resonant motion in astrodynamics

PDF

Interactions of planetary surfaces with space environments and their effects on volatile formation and transport: atomic scale simulations

Asset Metadata

Creator Lyon, Joseph A. (author)

Core Title Effects of pressure on heat-recirculating combustors for micropropulsion applications

School Viterbi School of Engineering

Degree Master of Science

Degree Program Astronautical Engineering

Publication Date 04/05/2021

Defense Date 03/18/2021

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag extinction limits,heat-recirculating combustors,micropropulsion,OAI-PMH Harvest,pressure effects,Swiss roll combustors, MEMS

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Ronney, Paul (committee chair), Erwin, Dan (committee member), Goodfellow, Keith (committee member)

Creator Email lyonjose@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c89-435896

Unique identifier UC11667815

Identifier etd-LyonJoseph-9398.pdf (filename),usctheses-c89-435896 (legacy record id)

Legacy Identifier etd-LyonJoseph-9398.pdf

Dmrecord 435896

Document Type Thesis

Rights Lyon, Joseph A.

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the a...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus MC 2810, 3434 South Grand Avenue, 2nd Floor, Los Angeles, California 90089-2810, USA