Table of Contents
Design and Fabrication of Pulse Jet Engine Report Download
DESCRIPTION OF PULSE COMBUSTION
Pulsating combustion is a combustion process that occurs under oscillatory conditions. That means that the state variables, such as pressure, temperature, velocity of combustion gases, etc., that describe the condition in the combustion zone, vary periodically with time. Pulse combustion is a very old technology. The phenomenon of combustion-driven oscillations was first observed in the year 1777, subsequently
explained by Lord Rayleigh in the year 1878, and used in a variety of applications around the turn of the Century.
PULSE JET ENGINE
A pulse jet engine is a type of jet engine in which combustion occurs in pulses. Pulsejet engines can be made with few or no moving parts, and are capable of running statically. Pulse jet engines are a lightweight form of jet propulsion, but usually have a poor compression ratio, and hence give a low specific impulse. Pulsejet is an unsteady propulsive device with its basic components being the inlet, combustion chamber, valve and valve head assembly and a tailpipe.
TYPES OF PULSE JET ENGINES
There are two types of pulse jet engines: those with valves and those without. The ones with valves allow air to come in through the intake valve and exit through the exhaust valve after combustion takes place. Pulse jet engines without valves, however, use their own design as a valve system and often allow exhaust gases to exit from both the intake and exhaust pipes, although the engine is usually designed so that most of the exhaust gases exit through the exhaust pipe.
A. Valved Pulsejet Engine
Valved engines use a mechanical valve to control the flow of expanding exhaust, forcing the hot gas to go out of the back of the engine through the tailpipe only, and allow fresh air and more fuel to enter through the intake. The valved pulsejet comprises of a intake with a one-way valve arrangement. The valves prevent the explosive gas of the ignited fuel mixture in the combustion chamber from exiting and disrupting the intake airflow, although with all practical valved pulsejets there is some ‘blowback’ while running statically and at low speed as the valves cannot close fast enough to stop all the gas from exiting the intake.
B. Valveless Pulsejet Engine
The valveless pulse jet engine operates on the same principle, but the ‘valve’ is the engine’s geometry. Fuel as a gas or liquid vapor is either mixed with the air in the intake or directly injected into the combustion chamber. Starting the engine usually requires forced air and an ignition method such as a spark plug for the fuel-air mix. With modern manufactured engine designs, almost any design can be made to be ‘self-starting’ by providing the engine with fuel and an ignition spark, starting the engine with no compressed air. Once running, the engine only requires input of fuel to maintain a self sustaining combustion cycle.
APPLICATION OF PULSEJET ENGINE
Pulse jet engines have been used in many functional jets; they can also be used for a variety of other applications such as:
1) Water heating,
2) Biomass fuel conversion,
3) Heat generators and
CONCLUSIONS AND FUTURE STUDY
As we knew that valveless pulsejet engines are easy to build and operate but they produce a lot of noise during its operation, we identified the need to reduce the noise levels.
In order to further improve on the pulsejet research, several things can be done during the testing phase that would enhance the results. A pressure transducer that measures a pressure differential of 30 psi which would be compared with theoretical results to see how close to optimum the pulsejet is performing.
Additionally, further research in the effects of optimum fuel to air ratios and maximizing flow into the inlets could potentially show improvements in thrust and efficiency within the engine. Potentially something such as gasoline or Jet A fuel could be an alternate fuel source to the pulse jet and with acceptable fuel injection, these fuels could allow for greater thrust from the engine and overall lighter setup that could be used on a unmanned air vehicle or RC plane.
In Future they might be used in any of the ground applications efficiently so they are non-pollutant and eco-friendly engines. The fuels which are used for the operation of these engines are also cheap and can be helpful in all the needs. The design of the plenum chambers can also be changed into elliptical shape design in where we can expect to yield good results in reducing the sound.
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