Posted tagged ‘electrical energy’

Electrical Power Generation System Using Railway Track

September 29, 2011

The system includes a power source, such as a power generation device or an external powersource. The power co-generation system includes first and second electrical capacitance portions that are electrically coupled to the power source and that are configured to carry positive and negative charges, respectively. The power co-generation system further includes a biasing device that is configured to separate the first and second capacitance portions with respect to one another. Thus, by varying the distance between the capacitance portions in response to a vehicle on the rail, the capacitance portions cooperate to act as a variable capacitor that facilitates the co-generation of power with respect to the system. That is to say, the mechanical energy of the biasing device is converted into electrical energy for the system.


In accordance with another exemplary aspect of the present technique, a method of co-generating power via a vehicle traveling on a rail is provided. The method includes the act of driving first and second capacitor plates with respect to oneanother in response to the vehicle that is traveling on the rail. The method also includes the act of charging the first and second capacitor plates via a power source, such as a power generation device or an external power source. The method  further includes biasing the first and second plates apart from one another, thereby displacing the plates with respect to one another. This displacement changes the electrical capacitance between the first and second plates and, resultantly, increases the electric potential between the first and second plates. In turn, this displacement of the first and second plates facilitates the co-generation of electrical energy from the kinetic and potential energy of the vehicle on the rail.


Mechanical Engineering Interview Questions

September 23, 2011

01-interview-interview tips-mechanical engineering interview-job interview

  • What is Heat rate of a Power plant?

Heat rate is a measure of the turbine efficiency. It is determined from the total energy input supplied to the Turbine divided by the electrical energy output.

  • The highest value of Thermal conductivity is expected for

a.) Solid ice   b.) Melting ice c.) Water d.) Boiling water.

Give the Thermal conductivity value.

Solid Ice – 3.48 W/mK

Melting Ice thermal conductivity value is low because temperature is less.

Water’s Thermal conductivity value is 2.18 W/mK.

  • What is a Hydrostatic system?

Hydrostatics is the study of fluid bodies that are

  • At rest
  • Moving sufficiently slowly so there is no relative motion between adjacent parts of the body

For hydrostatic situations

  • There are no shear stresses
  • There are only pressure forces that act perpendicular to any surface.

It’s a closed loop hydraulic systems. It comprises of motor and pump. Here pump supplies energy to motor and motor gives return energy to pump supply.

  • If you heat a piece of steel with a hole in the center will the diameter of the steel get bigger or smaller?

It gets bigger.

(Example: Always the bearings are heated first for new installation in a shaft.)

  • What is the difference between Blower and Fan?

Fan is an air pushing device. Either Axial or Centrifugal type systems are used to move the air in low pressure. It is rotated by a motor separately.

When the fan is a housing of blades and motor, then it called as Blower. It directs the air in a single path with high pressure.

  • How to find a Ductile-Brittle Transition Temperature in metals?

The point at which the fracture energy passes below a pre-determined point for a standard Impact tests. DBTT is important since, once a material is cooled below the DBTT, it has a much greater tendency to shatter on impact instead of bending or deforming.

  • What is Hydrodynamic Cavitation?

Hydrodynamic cavitation describes the process of vaporization in a constrained channel at a specific velocity.

Bubble generation and Bubble implosion which occurs in a flowing liquid as a result of a decrease and subsequent increase in pressure.


August 23, 2011

An electrochemical reaction occurs between hydrogen and oxygen that converts chemical energy into electrical energy.

01-how fuel cell works-proton exchange membrane-hydrogen fuel cell

Think of them as big batteries, but ones that only operate when fuel—in this case, pure hydrogen—is supplied to them. When it is, an electrochemical reaction takes place between the hydrogen and oxygen that directly converts chemical energy into electrical energy. Various types of fuel cells exist, but the one automakers are primarily focusing on for fuel cell cars is one that relies on a proton-exchange membrane, or PEM. In the generic PEM fuel cell pictured here, the membrane lies sandwiched between a positively charged electrode (the cathode) and a negatively charged electrode (the anode). In the simple reaction that occurs here rests the hope of engineers, policymakers, and ordinary citizens that someday we’ll drive entirely pollution-free cars.

Here’s what happens in the fuel cell: When hydrogen gas pumped from the fuel tanks arrives at the anode, which is made of platinum, the platinum catalyzes a reaction that ionizes the gas. Ionization breaks the hydrogen atom down into its positive ions (hydrogen protons) and negative ions (electrons). Both types of ions are naturally drawn to the cathode situated on the other side of the membrane, but only the protons can pass through the membrane (hence the name “proton-exchange”). The electrons are forced to go around the PEM, and along the way they are shunted through a circuit, generating the electricity that runs the car’s systems.

Using the two different routes, the hydrogen protons and the electrons quickly reach the cathode. While hydrogen is fed to the anode, oxygen is fed to the cathode, where a catalyst creates oxygen ions. The arriving hydrogen protons and electrons bond with these oxygen ions, creating the two “waste products” of the reaction—water vapor and heat. Some of the water vapor gets recycled for use in humidification, and the rest drips out of the tailpipe as “exhaust.” This cycle proceeds continuously as long as the car is powered up and in motion; when it’s idling, output from the fuel cell is shut off to conserve fuel, and the ultra capacitor takes over to power air conditioning and other components.

A single hydrogen fuel cell delivers a low voltage, so manufacturers “stack” fuel cells together in a series, as in a dry-cell battery. The more layers, the higher the voltage. Electrical current, meanwhile, has to do with surface area. The greater the surface area of the electrodes, the greater the current. One of the great challenges automakers face is how to increase electrical output (voltage times current) to the point where consumers get the power and distance they’re accustomed to while also economizing space in the tight confines of an automobile.