a compendium of tech stuff

Aug 5, 2009

On 8:09 PM by Lalith Varun   No comments

A wave of “green” is washing over Ingolstadt: after two years of research, the “Travolution” team has developed a trend-setting concept to improve traffic infrastructure. Investment amounts to a total of about €1.2 million. AUDI AG and its venture partners presented the results recently, with further joint pilot projects to follow. “Travolution paved the way for innovative traffic management and the result is a functioning prototype for the traffic control of the future.”

The drive starts out like any other, just a quick trip across town to pick up some groceries. You drive effortlessly through the first green light and somehow drive past the next intersection as well. To your growing amazement, you easily make the third traffic light, too. Will this streak of traffic luck hold out? Will you arrive at your destination without stopping for a single light? You may have a great feel for the road, but you can't talk to the traffic lights. Or can you? In the German city of Ingolstadt, something peculiar is happening. Certain luxury vehicles have been observed gliding effortlessly through intersections. Even when they're forced to stop, they never seem to have to wait long. Who are these mysterious drivers and what allows their cars to cut though the municipal traffic system? It's no coincidence that the vehicles are all Audis, and that the automotive manufacturer is headquartered in Ingolstadt. The Bavarian city is currently playing host to an experiment in the future of driving called Travolution. With Audi's Travolution system, intelligent traffic lights talk to each other and cars talk to traffic lights, all to the benefit of human drivers.

As more and more vehicles take to the streets, cities face greater traffic congestion -- to the point where simply building larger roads is no longer a valid fix. Instead of adding more lanes, traffic engineers and scientists have worked to create intelligent transportation systems. Instead of simply managing vehicles at a specific intersection or on a particular road, the system would regulate a city's collective traffic flow in all its stops and surges. On the infrastructure side, intelligent traffic lights play a major role in keeping vehicles moving along, and feature prominently in Audi's Travolution system. The Travolution system also features an intelligent vehicle component, and this is where the system really appeals to people. Green means go, red means stop – this is simple. But what exactly does a yellow traffic light mean to the average driver? Most driving instructors will tell you it means to come to a complete stop if you can safely, otherwise, proceed into the intersection cautiously. Traffic engineers call this scenario the dilemma zone. A Travolution-equipped vehicle receives signals from intelligent traffic lights in the area, informing it exactly when the light will change. The vehicle's onboard computer then calculates exactly what speed the driver needs to maintain to continue through the light without stopping the vehicle. The computer then relates this information to the driver, via the Audi multimedia interface (MMI) infotainment system. The driver might need to maintain a slightly higher or lower speed to make the light, but he or she won't have to come to a complete stop. This doesn't just cut down on driver irritation, it cuts down on fuel consumption and exhaust associated with accelerating back up from zero.

Most intersections don't have intelligent traffic lights, and it will require a great deal of time and money to install them. On top of this, there's vehicle compatibility to consider. Plus, even if you fully update every street with the latest technology and sync it up to a network, you still have to worry about human error and good-old fashioned driver stupidity. Obeying Travolution might not be the best idea if the vehicle in front of you just came to an abrupt stop to avoid running over a squirrel. Many futurists think that driving technology such as Travolution will eventually lead to the existence of automated highways, where the opportunity for human error is negated entirely. So let’s hope that this experimental technology gets a nod from the German government and it soon spreads all over the world to reduce the wastage of time and fuel when caught in an unsympathetic traffic snarl.

Aug 2, 2009

On 9:01 AM by Lalith Varun   No comments

Airspeed is a measurement of the plane's speed relative to the air around it. The airspeed indicator is used by the pilot during all phases of flight, from take-off, climb, cruise, descent and landing in order to maintain airspeeds specific to the aircraft type and operating conditions as specified in the Operating Manual. The pitot (pronounced pee-toe) static tube system is an ingenious device used by airplanes and boats for measuring forward speed. The device is a differential pressure gauge which was invented by Henri Pitot in 1732.
Airspeed indicators work by measuring the difference between static pressure, captured through one or more static ports; and stagnation pressure due to "ram air", captured through a pitot tube. This difference in pressure due to ram air is called impact pressure.
Internal mechanism of an airspeed indicator
The static ports are located on the exterior of the aircraft, at a location chosen to detect the prevailing atmospheric pressure as accurately as possible, that is, with minimum disturbance from the presence of the aircraft. The open end of the pitot tube, usually mounted on a wing, faces toward the flow of air or water. The air speed indicator actually measures the difference between a static sensor not in the air stream and a sensor (Pitot tube) in the air stream. When the airplane is standing still, the pressure in each tube is equal and the air speed indicator shows zero. The rush of air in flight causes a pressure differential between the static tube and the pitot tube. The pressure differential makes the pointer on the air speed indicator move. An increase in forward speed raises the pressure at the end of the pitot tube. In turn, the air pressure pushes against a flexible diaphragm that moves a connected mechanical pointer on the face of the indicator. The indicator is calibrated to compensate for winds in the air current.
Airspeed indicators are calibrated for a sea level standard atmosphere. When the pressure/temperature combination yields a density altitude higher than sea level, the airspeed indicator displays a lower airspeed. Conversely, if the density altitude is below sea level (which is not uncommon in the Winter months at lower elevations), the airspeed indicator reads a faster airspeed.This brings you to ICE T.
The speed that you read right off the face of the airspeed indicator is indicated airspeed. That's the I in ICE T.
The C in ICE T stands for calibrated airspeed, which is indicated airspeed corrected for position error, which typically means that the static port is located in a place where its measurements are not accurate in certain flight configurations.
The E in ICE T stands for equivalent airspeed, but it might as well stand for expensive, because it reconciles an error that only becomes significant in airplanes flying faster than 300 knots and/or higher than 25,000 feet. The error is called compressibility error.
Finally, you come to the T, which is true airspeed. True airspeed is equivalent airspeed corrected for non-standard pressures and temperatures (density altitude). It is the actual speed at which the airplane moves through the air, and the only thing standing between it and ground speed is a correction for the effect of the wind.

Thus the AIRSPEED INDICATOR is similar to a speedometer in a car. It shows the speed (in knots) of the airplane traveling through air.

Aug 1, 2009

On 9:38 PM by Lalith Varun   1 comment

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.

Turbochargers allow an engine to burn more fuel and air by packing more into the existing cylinders. The typical boost provided by a turbocharger is 6 to 8 pounds per square inch (psi). Since normal atmospheric pressure is 14.7 psi at sea level, you can see that you are getting about 50 percent more air into the engine. Therefore, you would expect to get 50 percent more power. It's not perfectly efficient, so you might get a 30- to 40-percent improvement instead.

One of the main problems with turbochargers is that they do not provide an immediate power boost when you step on the gas. It takes a second for the turbine to get up to speed before boost is produced. This results in a feeling of lag when you step on the gas, and then the car lunges ahead when the turbo gets moving.One way to decrease turbo lag is to reduce the inertia of the rotating parts, mainly by reducing their weight. This allows the turbine and compressor to accelerate quickly, and start providing boost earlier.

Thus turbochargers are used to significantly boost the engine horsepower of high performance sports cars etc.