Enjoy-neering!

So I finally managed to get this to work. A user defined function written to define the motion of a piston using the Scotch-Yoke (a perfect sinusoid) motion equation v=rw(sinwt). Ignore the displayed crank angle, still got to work on that.

#include “udf.h”

DEFINE_CG_MOTION(scotch, dt, vel, omega, time, dtime) { real r, w, pi, v;

pi = 3.1415;

/* define motion variables */ r = 0.0323; /* 32.3mm  crank radius in m */ w = 2 * pi * (700/60); /* 700RPM-the rpm of engine */ v = r * w * sin(w*time);

/* define object movement law */ vel[0] = 0; vel[1] = v; vel[2] = 0; }

The Water Eater

by Txchnologist Staff

Visualizing Flow

by Txchnologist Staff

GE is building the next generation of jet engines for the world’s fleet of commercial aircraft. These intelligent machines employ optimized architecture and technologies to produce outstanding fuel efficiency and power output.

Turbojet and Turbofan Jet Engine Overview

Part of a series of Jet Engine Overviews

Turbojet/Turbofan engines are the most common type of jet engines in use today. From commercial airliners to jet fighters, the vast majority of production jet aircraft utilize at least one of these types of engines. These engines are relatively simple air breathing designs which follow the basic layout of a jet engine.

Turbojet Engines

The turbojet engine is considered to be the most basic jet engine design.  It consists of an intake, a compression chamber, a combustion chamber, a turbine and an exhaust nozzle.

Air enters the intake and immediately passes into the compression chamber. In the compression chamber air is compressed by spinning fans as it passes through a narrowing duct into the combustion chamber. Just before the air reaches the combustion chamber, it is mixed with fuel. Inside the combustion chamber, the fuel/air mixture is ignited. The hot, high-pressure air expands out of the combustion chamber where it passes through a set of turbines. The passing air spins these turbines which, in turn, spin the compressive fans at the fore of the engine, sustaining the flow of air. After passing the turbines, the air exits the back of the engine through the exhaust nozzle. In engines with an afterburner, air is reheated between the turbine and the exhaust nozzle. Afterburners are typically about 4 times less efficient than the primary combustion chamber due to the decreased air pressure aft of the turbine.

The following graphs allow an easier visualization of the air temperature, pressure and velocity during the operation of a turbojet engine.

Turbofan Engines The turbofan engine is an augmentation of the turbojet engine. As the name would imply, the turbo fan adds a fan which functions similarly to a prop on a propeller driven plane. The turbofan engine contains a standard turbojet engine at its core but adds a duct around the outside of this engine for some air to pass through.

The flow that passes through the integral turbojet is called core airflow while the air that moves through the outer duct is called bypass flow. In General, there are 2 different types of turbofan engines, they are…

Low Bypass Turbofan Engines In low bypass engines, a relatively large portion of the air that passes through the engine is core airflow. To put it another way, there is a lower amount of bypass flow. The ratio of bypass airflow to core airflow is usually around 2:1 or less, with low bypass engines being optimized for efficient flight at higher Mach numbers. Most modern fighter jets utilize low bypass engines. Fighters like the F-16 and F/A-18 have bypass ratios of around .35:1.

High Bypass Turbofan Engines Conversely, high bypass engines allow lots of air to bypass the integral turbojet. High bypass engines usually have ratios between 5:1 and 10:1. These engines are optimized for efficient subsonic flight, usually around Mach .8. Most modern commercial airliners and some military transports use this type of engine.

Turbojet/Turbofan History

In 1939, the He 178 was the first turbojet aircraft to fly. 

Shortly thereafter, in 1944, the Me 262 became the first operational jet fighter, followed closely by the Gloster Meteor in the same year.

By the 1950s, jet engines were nearly ubiquitous on military aircraft, and some had even been approved for civilian use, such as those mounted on the de Havilland Comet.

By the 1970s, jet engines had become all but ubiquitous in the commercial air industry due to the introduction of the high bypass turbofan.

In 2003, the Concord makes its last flight, marking the end of the turbojet engine in the commercial airline industry.

As of writing, all current production fighter planes use some form of turbofan engine, along with most bombers and most commercial airliners.

Turbojet/Turbofan pros and cons

Turbojet Pros

Smaller engine circumference means more compact engine

Capable of attaining high speeds

Good specific impulse at lower Mach numbers

Turbojet Cons

Misses many improvements in power and efficiency when compared with turbofan

Loud

Turbofan Pros

Excellent specific impulse at useful range of speeds

Quieter than turbojet and many other jet engines

Turbofan Cons

Larger diameter

More complexity

More vulnerable to ice damage

RS-25 rocket engine No. 0525 is positioned onto the A-1 Test Stand at NASA’s Stennis Space Center in Mississippi in preparation for a series of developmental tests.

Image Credit: 

Today, we tested the RS-25 engine at Stennis Space Center in Mississippi, and boy was it hot! Besides the fact that it was a hot day, the 6,000 degree operating temperature of the hot fire test didn’t help things. This engine is one of four that will power the core stage of our Space Launch System (SLS) into deep space and to Mars. Today’s test reached 109% power and burned 150,000 gallons of liquid oxygen and 60,000 gallons of liquid hydrogen. When SLS launches with all 4 of its engines, it will be the most powerful rocket in the world!

This engine was previously used to to fly dozens of successful missions on the space shuttle, so you might be asking, “Why are we spending time testing it again if we already know it’s awesome?” Well, it’s actually really important that we test them specifically for use with SLS for a number of reasons, including the fact that we will be operating at 109% power, vs. the 104% power previously used.

If you missed the 535-second, ground rumbling test today – you’re in luck. We’ve compiled all the cool stuff (fire, steam & loud noises) into a recap video. Check it out here:

Ethereal forms shift and swirl in photographer Thomas Herbich’s series “Smoke”. The cigarette smoke in the images is a buoyant plume. As it rises, the smoke is sheared and shaped by its passage through the ambient air. What begins as a laminar plume is quickly disturbed, rolling up into vortices shaped like the scroll on the end of a violin. The vortices are a precursor to the turbulence that follows, mixing the smoke and ambient air so effectively that the smoke diffuses into invisibility. To see the full series, see Herbich’s website.  (Image credits: T. Herbich; via Colossal; submitted by @jchawner, @__pj, and Larry B)

It’s official: Brownsville, Texas, will host the first commercial rocket launch site in the U.S.