Abstract
In this project we fabricated a jet engine by modifying aturbocharger. We used the compressor and the turbine assembly and installed a combustion chamber in between these two, resulting in the production of thrust. Due to revolution of more than 1,00,000. We measured the Pressure created by the compressor with pressure gauge. The Turbocharger approached its limits because of the intense temperature of the exhaust gas.
Introduction
The turbojet is the oldest kind of general-purpose air breathing jet engine.Until 1930’s only reciprocating engines were used, but the rpm of those engines could not exceed 10,000 rpm. So, engineers thought to devise another system which could provide higher rpm’s up to 1, 00,000 rpm’s. As a result of which turbo jet engines were produced.
Basically turbo jet engine consists of three parts (i) air compressor (ii) combustor (iii) turbine. We had a turbocharger which fulfills the requirements of both air compressor and turbine. So, we fabricated a combustion chamber to engineer this turbo jet engine. Turbojets consist of an air inlet, an air compressor, a combustion chamber, a gas turbine (that drives the air compressor) and a nozzle. The air is compressed into the chamber, heated and expanded by the fuel combustion and then allowed to expand out through the turbine into the nozzle where it is accelerated to high speed to provide propulsion. A turbojet engine is used primarily to propel aircraft, but has been used for other vehicles, such as cars. Air is drawn into the rotating compressor via the intake and is compressed to a higher pressure before entering the combustion chamber. Fuel is mixed with the compressed air and ignited by a flame in the eddy of a flame holder. This combustion process significantly raises the temperature of the gas. Hot combustion products leaving the combustor expand through the turbine where power is extracted to drive the compressor. Although this expansion process reduces the turbine exit gas temperature and pressure, both parameters are usually still well above ambient conditions. The gas stream exiting the turbine expands to ambient pressure via the propelling nozzle, producing a high velocity jet in the exhaust plume. If the momentum of the exhaust stream exceeds the momentum of the intake stream, the impulse is positive, thus, there is a net forward thrust upon the engine.
Design
The basic design has four major components:
(i) Turbocharger
(ii) Combustion chamber
(iii) Ignition system
(iv) Cooling system
Turbocharger:
2. The center housing/hub rotating assembly
3. The Compressor
Working principle:
Turbochargers are a type of forced induction system. They compress the air flowing into the engine. The advantage of compressing the air is that it lets the engine squeeze more air into a cylinder, and more air means that more fuel can be added. Therefore, you get more power from each explosion in each cylinder. A turbocharged engine produces more power overall than the same engine without the charging. This can significantly improve the power-to-weight ratio for the engine.
In order to achieve this boost, the turbocharger uses the exhaust flow from the engine to spin a turbine, which in turn spins an air pump. The turbine in the turbocharger spins at speeds of up to 150,000 rotations per minute (rpm) -- that's about 30 times faster than most car engines can go. And since it is hooked up to the exhaust, the temperatures in the turbine are also very high.
Turbocharger Design& Working:
The turbocharger is bolted to the exhaust manifold of the engine. The exhaust from the cylinders spins the turbine, which works like a gas turbine engine. The turbine is connected by a shaft to the compressor, which is located between the air filter and the intake manifold. The compressor pressurizes the air going into the pistons.
The exhaust from the cylinders passes through the turbine blades, causing the turbine to spin. The more exhaust that goes through the blades, the faster they spin. On the other end of the shaft that the turbine is attached to, the compressor pumps air into the cylinders. The compressor is a type of centrifugal pump -- it draws air in at the center of its blades and flings it outward as it spins.
Bearings:
In order to handle speeds of up to 150,000 rpm, the turbine shaft has to be supported very carefully. Most bearings would explode at speeds like this, so most turbochargers use a fluid bearing. This type of bearing supports the shaft on a thin layer of oil that is constantly pumped around the shaft.
Bearings serve two purposes
(i) These cools the shaft and some of the other turbocharger parts
(ii)
Specifications
1- This turbocharger belongs to Toyota Hiace 2.3 L.
2- It has an inducer dia of 1.75 inches.
3- It was bought from bilal gang Lahore.
(ii)Combustion chamber:
Combustion chamber has two major parts:
1- Combustion shell
2- Flame tube
Combustion Shell
Combustion shell is the outer shell ofcombustion chamber whichcontains the flame tube. It’s one end is connected to the compressor and other is connected to the turbine.
Spark plug is also mounted on its surface.
Spark plug is also mounted on its surface.
Specifications and construction
1- Combustion shell is made of steel SS(stainless steel) grade 304 and argon welding is used for fabrication.
2- External dia = 3.87 inches.
3- Thickness = 1.8 mm
4- External dia of inlet = 1.51 inches.
5- Thickness of inlet = 2.05 mm.
It is the inner part of combustion chamber, contained within the combustion shell. Fuel reservoir is connected to it. Fuel jet is thrown with the help of a nozzle in the flame tube. It contains holes for mixing of air with fuel after which a spark is produced with the help of spark plug to combust the air fuel mixture which produces hot gases to run the turbine.
There are three types ofholes present on the surface of flame tube.
1- Primary holes
2- Secondary holes
3- Tertiary holes
Specifications and construction
1- Flame tube is made of steel SS grade 304 and argon welding is used during fabrication.
2- Length of flame tube = 10.5 inches.
3- External dia of flame tube= 2.68 inches.
4- Thickness of flame tube = 1.8 mm.
5- Length of fuel jet = 5 inches.
6- There are 22 primary holes having dia 0.25 inches each.
7- 15 secondary holes having dia 0.5 inches each.
8- 5 tertiary holes having dia 0.75 inches each.
(iii)Ignition system
Ignition system is used to initiate the combustion in the turbocharger jet turbine engine. It has three major components:
1- Nozzle used to throw a high velocity fuel jet in the flame tube.it has a length of 2.5 inches.
2- Electronic circuit which provides the voltage of 10kv to the spark plug with an input of 220 volts. This electronic circuit was bought from hall road.
3- Spark plug used to ignite the fuel. This spark plug belongs to a Honda CD 70cc.
(iv)Cooling system
There are basically two cooling systems used in this engine.
1- Water cooling system which consists of a power head water pump having a capacity of 600 L/H normally used in aquarium.
2- Oil cooling system consisting of a viper pump of Honda Civic Reborn.
We used two reservoirs, one for water and one for oil.
(v) Control panel
Control panel consisting of 3 switches, one for ignition, one for oil pump and one for water pump. There is also a push button for ignition and a voltmeter.
There is also a pressure gage for measuring the pressure of compressor up to 1 bar.
First test run
We used a blower as a starter to give turbine the initial rpm. We released the gas and pushed the ignition button but it didn’t work. So we used a lighter in front of exhaust to manually ignite the air fuel mixture. Our engine started gradually making the turbine red hot by the extreme temperature of exhaust gases. The pressure gage was showing 0.8 bar (11 psi) pressure. We were continuously measuring the temperature of the turbine by using an infrared thermometer. Here is the graph showing the relation between temperature and time.
Conclusion
1- Our project was an overall success producing a thrust.
2- The jet engine can be used to power go carts.
3- The engine shaft was rotating at a destructive RPM of more than 80,000 RPM.
4- Oil pressure was not sufficient due to which squeaking noises were generated in the engine.
5- The Fuel consumption of the Turbojet is far more than the convectional reciprocating engine. but the output power limit was much more as compared to it
6- By adding an Afterburner (future plan) we can momentarily increase the output of the engine by sacrificing more fuel.
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