This paper gives a brief analysis on the performance parameters of a Turbocharger, by fabricating a separate combustion chamber and mocking the working of a jet engine. Parameters such as variation of specific heat, dimensionless flow parameters, variation of turbulence, conductivity, thrust developed etc are studied using simulation of the model, and compared with the actual working of the prototype. It can be conveniently proposed from the experiment that turbocharger can be used effectively for developing vertical take-off assist.
Report
Share
Report
Share
1 of 5
Download to read offline
More Related Content
Analysis of turbocharger performance for jet assisted vertical takeoff and landing
1. International Journal For Research & Development in Technology
Volume: 1, Issue: 2, JUNE 2014 ISSN (Online):- 2349-3585
23 Copyright 2014- IJRDT www.ijrdt.org
Analysis of Turbocharger Performance for Jet
Assisted Vertical Takeoff and Landing
________________________________________________________________________________________________________
Roopesh Kaimal1
,Jason Jacob2
, Deepu Mohan3
,Gokul G.Nair4
, Libin P. Oommen5
12345
Mechanical Department, Saintgits College Of Engineering, Kottayam,
Kerala.
Abstract—This paper gives a brief analysis on the
performance parameters of a Turbocharger, by fabricating a
separate combustion chamber and mocking the working of a
jet engine. Parameters such as variation of specific heat,
dimensionless flow parameters, variation of turbulence,
conductivity, thrust developed etc are studied using
simulation of the model, and compared with the actual
working of the prototype. It can be conveniently proposed
from the experiment that turbocharger can be used
effectively for developing vertical take-off assist.
Keyword—Turbocharger, VTOL, Performance, JATO, Take
off, Jet Engine
I.INTRODUCTION
For the past 2 to 3 decades, enthusiasts and engineers around
the world has been working all over the world for the
invention of a car that can vertically take off into air. Such an
invention would make possible a faster mode of transportation.
The aviation industry has seen a hike in number of passengers
over the last few years. It is expected that the number of
passengers in airline will reach 3.6 billion by the year
2016(Source :IATA). Airline industries have also seen an
increase in private flights around the world. All this show a
future where flights are possible from the backyard of house.
Many scientists has been researching on engines, aerodynamic
effects, safety concerns etc of a possible VTOL aircrafts and
vehicles.
In Advances in Combustion and Propulsion Applications[1],
Mr.Candel and Mr.Durox has discussed on various
combustion techniques like cryogenic combustion, Turbulent
Combustion and the problems associated with the same. Using
numerical simulations, they showed that by using turbulence
as the prime driver of combustion, process of combustion can
be improved to a greater extent.
Survey conducted by Jean P. Renaud for Air and Europe had
presented various advances in technologies of VTOL aircraft
using rotorcraft model. The main disadvantage of such an
aircraft is with the propulsion system, capacity, size, sound
and speed of the resulting aircraft.
In 2007, Researchers from university of Padova took the
initiation to develop a small scale low cost turbojet engine.
The results were published in Design, manufacturing and
operation of a small turbojet-engine for research purposes[3].
The design focused on low cost and high thrust. But the
research didn’t include the comparison of various performance
parameters and the analysis of combustion taking place inside
the turbojet engine.
`In 2013, Analysis was conducted on small scale turbojet
engine to determine the performance parameters[4]. Various
parameters like mass flow rate, pressure, velocity etc were
compared with experimental and numerical data and the
results were compared in the paper.
Though there were many researches in turbojet engines, most
of them concentrated on axial flow engines. But for use in a
VTOL aircraft, centrifugal flow engines are more suitable.
Centrifugal engines can direct flow in a 90degree angle
enabling the jet to be directed to the ground for a vertical
takeoff. Though many military aircrafts use engines were
nozzle can be adjusted to redirect the flow, very few
analyseshave been done on the same.
In this paper, a turbojet engine model is fabricated using a
turbocharger and numerical and experimental analysis are
done on the model to determine the variation in performance
parameters when used to take off a model vertically from the
ground. The ultimate goal of this project is to develop a small
scale economic jet engine that can develop high thrust.
II DESIGN
The specification of the prototype was selected such that an
economic low cost engine can be developed for the
experimental purpose. The following assumptions are made:
• A simple Brayton Joule Cycle was adopted for analysis
of the whole purpose. This relieves the apparatus from
any complication.
• Considering the turbine blade temperature safety limit,
the maximum inlet temperature was fixed at 1000 K.
• Commercially available turbocharger was used for the
portion of centrifugal compressor and turbine.
2. International Journal For Research & Development in Technology
Volume: 1, Issue: 2, JUNE 2014 ISSN (Online):- 2349-3585
24 Copyright 2014- IJRDT www.ijrdt.org
• Following set of parameters are assumed for the design
purpose
- Turbine Efficiency = 70%
- Compressor Efficiency = 70%
- Ambient condition : 290K temperature, 1 Bar
pressure, 75% humidity
- Cycle – Brayton joules Cycle
- Combustion efficiency = 95%
III DESIGN PROCEDURE
Selection of Turbocharger
A KKK type turbocharger manufactured by TELwas
selected for the purpose. The turbocharger had single stage
compressor and turbine with an inlet double stage diffuser that
reduced the velocity of the incoming air.Non waste gate
turbocharger was selected for the purpose so that energy loss
is reduced.
Selection Of Materials
The material for the connecting pipes, combustion chamber
and flame tube were selected on the basis of material cost,
density, availability etc. After comparing Mild Steel, Stainless
Steel, Titanium and Aluminum, MS was chosen as the best
option for the prototype.
Table 1. Comparison of properties of metals
Metal
Cost
(Rs/Kg)
Melting
Point
Density
(g/cm3
)
Thermal
Conductivity
(W/m K)
Mild Steel 65-70
1450-
1550
7.80-
7.90
Stainless
Steel
100-120 ~1500 ~ 8
50.2
Titanium
300-
3000
1650-
1750
~4.5 15-20
Aluminium 100-110 ~650 ~2.7 ~205.0
Gasoline was chosen as the best fuel alternative. This is
because the compressor of the turbocharger was not heavy
enough to provide the required compression ratio for diesel.
Kerosene can lead to coke deposits inside the flow field when
cooled down. These deposits can later give away from the
walls to damage the turbine blades. Aviation Fuel was not
available for commercial use in the market. LPG was harder to
set up and the risk of backfiring was greater in LPG.
Design of Combustion Chamber
The combustion chamber was designed to withstand a safe
stress limit that combined the thermal stresses induced during
the combustion process, in addition to the pressure force
developed inside the chamber during the explosion.
A Dual flow design was opted for the prototype. The outer
chamber consisted of a smaller inner flame tube within which
the combustion takes place. The flame tube was divided into
three stages which include primary zone, secondary zone, and
tertiary zone. Holes were drilled onto each section of the flame
tube so that predetermined air flows through the holes. This is
to ensure efficient and complete combustion of the fuel inside
the combustion chamber.
The primary or the premixing zone consist of 20 equally
distributed zones split into two rows such that about 21% of
total intake air is permitted into flames tube, when the turbine
is running at its rated speed of 60,000 rpm. This zone ensures
a stoichiometric mixing of air and fuel in this zone.
The secondary zone consists of 6 equispaced holes around
the periphery of the flame tube, so that 55% of air is permitted
inside the flame tube to provide excess of air into the flame
tube. This excess air makes the mixture lean ensuring a
complete combustion and a higher thrust.
The tertiary or cooling zone had 5 holes equispaced along
the periphery of the flame tube that ensured 34% of air to enter
the flames tube. This zone acts as a quenching zone that
reduces the flame temperature before it hit the turbine blades.
It also helps in ensuring a stable flame by providing a longer
path for the flame front to travel.
Fig. 1 Flame tube
The air entering the tertiary zone is swirled in between the
combustion chamber and the flames tube. This serves for two
purposes. Part of the circulated air carries away heat from the
walls of combustion chamber. This heats up the air to a
temperature higher than the ambient temperature, which will
contribute to flame stability as it enters the flame tube through
the tertiary zone.
A nozzle is provided at the end of the flame tube to convert the
pressure head developed in the flames tube to Kinetic head
inside the turbine. This reduced the temperature of the mixture,
in addition to reducing the pressure of the mixture while
flowing through the connecting pipes.
Placing Sparkplug and Fuel injector
To ensure a perfect combustion of the air-fuel mixture inside
the flame tube, the sparkplug was positioned in a plane
perpendicular to the fuel injector. The fuel injector was placed
before the primary zone while the spark plug was placed
inside the secondary zone. This ensures a perfect premixing
before the actual combustion taking place.
To reduce the size of the engine, instead of an afterburner, a
second spark plug was placed just at the end of the tertiary
zone. This sparkplug ensures that any unburnt mixture is given
enough energy for combustion. This also ensures that the
flame front travelled until the extreme end of the flame tube.
NUMERICAL ANALYSIS
In order to verify the design, numerical analysis was
conducted on the prototype model using CAD packages. A 3D
model of the prototype was built in the computer and put
through a series of tests.
Static pressure tests, thermal tests were conducted on various
parts of the prototype to ensure that the product met the design
3. International Journal For Research & Development in Technology
Volume: 1, Issue: 2, JUNE 2014 ISSN (Online):- 2349-3585
25 Copyright 2014- IJRDT www.ijrdt.org
specifications. Fluid Flow analysis was done through the parts
of Combustion Chamber to study the flow field parameters.
In order to conduct Numerical analysis, following assumptions
were made.
• The turbine and the compressor are running at its
rated speed of 60,000 rpm.
• The flow through turbine and compressors are of not
much important, as knowing the efficiency of the
both, their parameters can be understood.
• Turbine extracts energy from the gas only to power
the compressor to which it is coupled off. Rest of the
energy is given out through the exhaust either as
temperature, or kinetic or potential heads.
• Gasoline-Air mixture after combustion can be
satisfactorily regarded as Ideal air with only 5% error
in the assumption.
• As per the design, the Fuel-Air mixture is static in the
direction of axis of the cylinder in the primary zone.
This assumption is because the fuel and the air enters
in a perpendicular direction and the air is made to
surround the fuel spray from all around the periphery
of flame tube.
• Complete combustion is taking place in the flames
tube. There is no a deposit or unburnt gases escaping
from the chamber.
• The turbine does no other work in the flow other than
extracting some amount of energy from the
combustion gases to power the compressor. Hence
the flow through the turbocharger is of less
importance.
Static analysis
In order to study the deformation of pipes under
pressure and thermal stresses, the combustion chamber and the
connecting pipes were tested for static pressure test and
thermal stress.
Fig. 2 Static Pressure test
Fig. 2 above shows the result of static pressure test. The
deformation of the tubes was within the limits of the safe limit.
The deformation was obtained to be around 1 micrometer.
Fig. 3 Heat conduction in flames tube and adjacent pipes
Heat flow by conduction along the tubes under static condition
was analyzed to determine the thermal stresses that might be
induced in the pipes. Fig. 3 shows the result of temperature
flow under static conditions. It can be concluded that not much
heat is given to adjacent tubes due to the generation of heat
inside the flame tube.
Fluid Flow Analysis
Air under ambient conditions was given into the compressor
and the flame tube and the variation of flow parameters were
analyzed inside the flame tube.
Following assumptions were made for the analysis
Ambient temperature = 288K
Ambient Pressure = 101.25 KPa
Humidity = 40%
• Inlet Conditions to the compressor are ambient
conditions. There is no external work done on the air
by any object other than the diffuser to the
compressor. On a plane immediate to the walls of the
diffuser, the conditions of the air are ambient.
• Gasoline is assumed to have 85% purity. The
impurities in the gasoline though are assumed to have
no effect in the flow field.
From the analysis, it was obtained that the velocity at the exit
was close to sonic. A maximum temperature of 1500K was
obtained in the flames tube while the temperature in the
turbine blades was limited to below 1100 K. The temperature
at the exhaust was limited to under 500 K, reducing the risk of
thermal shocks to objects nearby. The two concentric cylinders
reduced the thermal losses from the cylinder and maximum
efficiency was obtained in combustion. Parameters like
Thermal conductivity, specific heat and other dimensionless
numbers where fluctuating across the nozzle in the flamestube.
This might be because, at the left side of the flames tube there
was a higher temperature and pressure head while towards the
side of turbine, the conditions were lower temperature and a
higher velocity. A maximum force of around 145 Kg was
obtained from the engine from which it can be concluded that
the engine can be used to demonstrate a volant of considerable
weight. The intensity of turbulence was lower than expected.
Hence turbulent energy loss was also lower.
4. International Journal For Research & Development in Technology
Volume: 1, Issue: 2, JUNE 2014 ISSN (Online):- 2349-3585
26 Copyright 2014- IJRDT www.ijrdt.org
Fig. 4 Variation of Pressure along flame tube length
Fig. 5 Variation of Velocity along flame tube length
Fig. 6 Variation of Temperature along flame tube length
Fig. 7 Variation of Force with time
From the results of the numerical analysis, it can be concluded
that the engine can generate suitable amount of thrust.
The pressure variation is shown in Fig. 4. The pressure has an
extreme value of around 42 bar inside the combustion chamber.
But it gradually reduces along the length until it steeply gets to
20 bar as it pass through the nozzle section. This reduces the
temperature from around 1700 K to 1400K as can be inferred
from Fig. 6. This temperature is further reduced when the
effect of the turbine is also considered. Fig. 6 shows the
variation of velocity along the length of flame tube. The
velocity reaches around 1100K at the exit of the nozzle. But
high temperature results in the mach number to be less than 1.
EXPERIMENT
In order to verify the results obtained in numerical analysis,
experiment was conducted using the prototype
built.
Fig. 8 Cad model of prototype
Fig. 7 shows the cad model of the prototype built using 3D
modeling software. As marked, the air enters into the inlet of
the compressor blades. The compressed air is then fed into the
combustion chamber at high pressure. Fuel is sprayed into the
combustion chamber perpendicular to the entry of air, to
ensure proper mixing. The exhaust gases are fed to the turbine
through a nozzle that serves to reduce the pressure and
temperature of the gas hitting the turbine blades. The turbine
after extracting energy to drive the compressor throws out the
gases. These gases expand to atmospheric pressure resulting in
thrust in the opposite direction as shown.
Fig.9 Final Fabricated model before testing
Based on the design and analysis results, a model was
fabricated as shown in Fig. 9. The model was fabricated using
5. International Journal For Research & Development in Technology
Volume: 1, Issue: 2, JUNE 2014 ISSN (Online):- 2349-3585
27 Copyright 2014- IJRDT www.ijrdt.org
Mild Steel tubes. 3 HP 1450 rpm single phase electric motor
was used to drive the pump of the fuel injector. Belt drive was
used to drive the pump at its rated speed of 1750 rpm. K type
thermocouple was used to measure the temperature at the
exhaust as well as on the outside of the combustion chamber.
As the temperature at the exhaust was small, standard pressure
gauge was used to measure the exhaust pressure. The velocity
was measured using a calibrated turbine placed at the exhaust
of the turbocharger. The force was calculated using the thrust
equation.
The experiment was conducted for two different mass flow
rate of fuel at turbine rated speed of 60,000 rpm. The thrust
obtained was 25Kg and 40 Kg respectively at a fuel flow rate
of 2 LPM and 3 LPM. The temperature at exhaust was 350K
and 500 K respectively and at the periphery of combustion
chamber the temperature was 338K and 379 K respectively
CONCLUSION
In order to analyze the variation of parameters during the flow
through a centrifugal jet engine and to determine the thrust
developed from it, a jet engine was designed using an
automotive turbocharger. Numerical and Experimental
investigations are done on the turbocharger and the following
conclusions can be obtained from the results obtained.
• By using limited funds and conventional methods, a
high pressure of up to 45 bar and velocity of
1200m/s was obtained from the engine.
• The thrust developed by the engine during the
experiment was 40Kg. But numerical analysis
showed that the engine can develop up to 145Kg of
thrust. Minor modifications such as including
preheat for fuel, sealed combustion chamber,
efficient turbine and compressor, higher thrust to
weight ratio can be obtained.
• Proper design can reduce thermal and turbulence
losses to a great extent. Hence higher efficiency
can be obtained from the engine.
• The size of the engine can be reduced by using
advanced technologies and non-conventional
methods. This can yield a lower Thrust specific
Fuel consumption.
• The fuel consumed by the engine was 120-180 Litres
per minute when it developed 40 Kg of thrust. This
can be improved satisfactorily.
• The exhaust temperature can be reduced to an extent
that will not harm the objects nearby when the
engine is powered.
• A low cost jet engine can be easily manufactured to
yield a high thrust to weight ratio.
The understanding of subjects like flame stability is limited
in the present scenario. This knowledge is to be widened in
order for a more keen combustion in the engine. A deeper
understanding of various flow parameters are to be done
inorder to improve the engine efficiency and thrust
produced.
FUTURE WORKS
In order to obtain more information on the flow properties,
following researches are planned and suggested:
• Analysis of the engine for varying mass flow
rates of fuel and air.
• Varying the fuel used for combustion. Using
alternate fuels like Diesel, Propane, LPG,
Kerosene, Aviation Fuel, Bio-Diesel and other
alternates and studying their impact on the
variation of properties of the engine.
• Including the analysis of flow in turbine and
compressor.
• Including the effects of fuel impurities, thermal
losses, incomplete combustion, turbulent
energy losses, and vibrational losses.
A better understanding of these properties is necessary for
further improvement in a low cost jet engine that can yield for
a future mode of transport.
REFERENCES
[1]. ChehhatAbdelmadjid, Si-Ameur Mohamed,
BoumeddaneBoussad, CFD Analysis of the
Vloute Geometry Effect on the Turbulent Air
Floq Through the Turbocharger
Compressor,TerraGreen 13 International
Conference 2013 – Advancements in Renewable
Energy and Clean Environment, Elsevier,
Energy Procedia 36 (2013) 746 – 755
[2]. Ernesto Benini, Stefano Giacometti, Design,
Manufacturing and operation of a small turbojet
engine for research purposes, Elsevier, Applied
Energy 84 (207) 1102 – 1116
[3]. M. Badami, P. Nuccio, A Signoretto,
Experimental and Numerical Analysis of a small
scale Turbojet engine, Elsevier, Energy
Conversion and Management 76 (2013) 225-233
[4]. M Deligant, P Podeving, G Descombes,
Experimental identification of Turbocharger
Mechanical Friction losses, Elesevier, Energy 39
(2012) 388 – 394
[5]. David Scott Underwood, MS Thesis, Primary
Zone Modelling of Gas Turbine Combustors,
Massachustts Institute of Technology, June 1999