Electric Propulsion Systems
By Ahmad Nugroho
Hybrids are designing to apply electric propulsion systems which demonstrate to be really efficient and as well as environmentally friendly. There perhaps several approaches and techniques in order to carry out movement applying electrical power but the main idea is still the same. These arrangements are already operative and will encourage help produce alternate fuel.
What is Electric Propulsion?
Electric propulsion is the speedup of gases in order to produce propellant thrust through electric and magnetic body forces, electric body forces or electric heating. The electric propulsion system is usually integrated in rocket science wherein it manages energy sufficiency to produce a powerful force. An electric propulsion system is an alternative to atomic propulsion system. The total force is less powerful compared to a atomic rocket but still sufficiency to produce effects.
According to a figure of studies, any engine exploited as a main source of such powerful propulsion must produce beat speeds of around 10 to 20 km/s. There are also storable chemical systems applied in rockets with an exhaust speed of around 5 km/s but overall is less efficient.
Propulsion systems that don’t require energy through chemical reactions are still needed. There are electric propulsion thrusters able to develop exhaust velocities of around 10 to 20 km/s which increases payload and reduces propellant mass. The results however, are less powerful thrusters consuming larger quantities of power.
The 3 Categories of Electric Propulsion
1. Electro thermal propulsion is when the propellant is electrically heated then isentropically expanded through a C/D or convergent/divergent nozzle. The system works as electrical energy heats propellants that produce gases as a result. The gases are sent through the C/D nozzle creating thrust. Catalyzed hydrazine or another neutral gas is used in thrusters like arc jets and resistojets.
Arc jets can also be used to heat the propellants via an electrical arc discharge. The arc in the arc jet is a beam of electrons produced from the cathode tip then gathers at the anode. Since an arc jet has a cathode and an anode, a constrictor is also present which is a narrow pathway between the two charges.
2. Electrostatic thrusters are also called ion thrusters. These use an ionized propellant accelerated through electric fields applied directly like gridded ion thrusters and Hall thrusters. The technique of propulsion is also acknowledged as ion propulsion technique since ions are mainly used in the process. Electrostatic energy is used to produce propulsion.
The electrons from an atom are stripped off then converted to ions. The ions are accelerated by electrical forces to heat without needing thermal energy producing thrust. The atoms after losing electrons become positively charged.
3. Electromagnetic thrusters produce thrust using electric and magnetic force that interact with charged plasmas like ions and electrons. An example of these is the magnetoplasmadynamic thruster or MPD. The system heats the propellant to a plasma state before being accelerated. A large current is passed by electromagnetic forces through gas in order to ionize the propellant. Plasma is the ionized propellant which is then accelerated by Lorentz force, an electromagnetic force producing thrust.
Effect on Fuel
Decoupling engine speed and power output from the propeller will provide the opportunity to improve propeller efficiency. Since electric forces and electromagnetic forces contribute for support, petrol and diesel propulsion systems in vehicles will diminish the chances of wasting a huge part of power and energy.
The chances of engine overload are eliminated resulting to better fuel economy and better fuel consumption rate. Additionally, there is higher efficiency over longer distances and various speeds and loads.
A study conducted to check how much electric propulsion systems can help diesel and gasoline engines showed that at least 10% fuel savings is attained by simply allowing the engine to move along with the load reducing inefficiencies due to low load with high-velocity. Larger propellers can also save as much as 7% of fuel compared to traditional models.
With the total load split between multiple generators, as much as 20% of fuel can be saved plus another 13% by matching the power produced by the engine to the power required by the propeller. A variable-speed generator will help accomplish this. Overall, 30% to 50% can be saved compared to a very efficient diesel-electric or gasoline-electric system.
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