Aircraft Life Support Systems Part 2: Water and Waste System

Previous Blog

INTRODUCTION
In the aircraft industry, several systems are designed to provide safety and comfort for the crew and passengers.

Regarding comfort, the water and waste system is designed to provide water for galleys and lavatories. Fresh water is stored and distributed while a different system deals with wastewater. That system includes a thoughtful engineering method to dispose of the different wastes that could occur during the flight.

OVERVIEW

Water must be supplied to different parts of the plane during flight. This water is kept in a tank in the compartment aft of the bulk cargo compartment. The whole system is made up of a passenger water system that stores, delivers, monitors and controls drinkable (potable) water for the galley units and lavatory sink basins.

In this blog, we are going to focus more specifically on the 737-classic model from Boeing.

Figure 1-Representation of different parts of the water and waste system
Figure 1-Representation of different parts of the water and waste system

The 3 main achievements of the water and waste system are the following:

  • Filling the water tank on land
  • Providing water during the flight
  • Storing toilet waste

­

The water and waste system is made up of:

  • Potable water system aims to deliver fresh water to every needed part in the plane (including every component between the water tank and sinks)
  • Water tank pressurization system focuses on the pressurization of the water tank and air dealing with the tank (including air compressor, pressure regulator filter, pressure relief valve)
  • Wastewater system focuses on water related to lavatory and sinks / galleys wastewater (including drain masts)
  • Toilet system includes components related to flushing and toilet water (including waste tank)

­

The water tank has a capacity of 34 gallons (about 0.15 m3). The water system in the plane needs to be pressurized for altitude just like the cabin, so it gets pressurized by an air inlet (linked to the pneumatic system). Therefore, the water quantity should not exceed 30 gallons (about 0.13 m3). Read More

Aircraft Life Support Systems Part 1: Oxygen System

Next Blog

INTRODUCTION

In the aircraft industry, several systems are designed to provide safety and comfort for crew and passengers while traveling. Oxygen gets rarified with altitude, so life support is a very important system

The cabin is pressurized in order to provide breathable air, but reaching a sea level pressure is not advisable since it would lead to a significant pressure differential between the aircraft exterior and the cabin interior. This difference could damage the aircraft structure.

Additionally, the cabin altitude is different from the flight altitude. In fact, the cabin altitude corresponds to the one reached according to the cabin pressure. Usually a commercial flight cruises at an altitude of 35,000 ft, but thanks to the pressurization system, the cabin altitude is around 6,000-8,000 ft.  Indeed, the oxygen system provides breathable oxygen to the crew and passengers if any problem were to occur during the flight.

AIRCRAFT EMERGENCY OXYGEN SYSTEM:

In a normal situation, a bleed air system is used to provide fresh air throughout the flight duration. The air is hot and must be cooled and pressurized to make it breathable.  In the event of an emergency, the plane is already equipped with oxygen systems which are linked to passengers and cabin crew through masks. In fact, there are two oxygen systems on board. One designed for the crew, and the second for the passengers.

If the cabin pressure drops making cabin altitude about 14,000 ft, the emergency system are be triggered. The emergency system provides oxygen to passengers for 15 to 20 minutes, and for the crew members for around 30 minutes. This is enough time for the aircraft to descend to a lower altitude and being the cabin altitude to a safe breathable level.

Here, the crew oxygen system schematic of the Boeing 737 class is shown in Figure 1.

Figure 1-Crew oxygen system
Figure 1-Crew oxygen system

The main challenges of oxygen equipment are:

  • Fitting the dimensions of the plane
  • Secure (no leakage for example)
  • Responsive (to cabin pressure and cabin altitude)
  • Easy for passengers to use the oxygen system through the deployed masks quickly, before the effects of altitude are felt:
  • At 25,000 ft: a person has 3 minutes of consciousness
  • At 41,000 ft: a person has 30 seconds of consciousness

­

FLIGHT CREW OXYGEN

The flight crew oxygen should be designed and made with a lot of care, because if any trouble occurs during the flight, the crew must be able to handle the situation and take the airplane and its passengers down safely. Read More

The History of Turbochargers, Part 2

Hello! And welcome back for part 2 of our series on “A Brief History of the Turbocharger”. To read part 1, which compares superchargers and turbochargers, and explains the early history of turbochargers and forced induction from the turn of the century through to World War 1, click here. Having covered all of that, let’s pick up from where we left off!

Following World War 1, and the work of Dr. Sanford Alexander Moss, Alfred Büchi, who had created the first true turbocharger, had continued innovating following the failure of his first design. By 1925, he had a working turbocharger design that consistently and reliably worked (1).

Following this breakthrough, the turbocharger saw its first commercial application on ten-cylinder diesel engines. Since diesel engines are typically built to withstand the high-pressures required by their operating conditions, the pressures generated by using forced induction are easily accommodated. As a result of adding the turbochargers, the engines upped their horsepower ratings from 1750HP, all the way to a whopping 2,500HP. (1)

The Hansestadt Danzig, one of the German ships fitted with the 10 cylinder turbodiesel engine described above
The Hansestadt Danzig, one of the German ships fitted with the 10 cylinder turbodiesel engine described above. (shipspotting.com)

For Büchi, this was a great achievement, as it marked the first commercial application of a machine that he had first begun working with more than 20 years prior. For the turbocharger, however, this was just the beginning. Read More

Anti-Icing Systems in Airplanes: Boeing 737-300/400/500

Through the decades, the aircraft industry always improved their onboard systems to get the best performances, security and comfort. In order to build a lasting travel type, security of the aircraft is one of the main goals for engineers. Due to rough exterior conditions while flying, especially at high altitude, with relative humidity and very low temperatures, the freezing temperature can cause the plane to ice. Ice can have major impacts on the aircraft’s weight and aerodynamical phenomena, – especially the lift – (the lift can decrease to 40% due to ice). Modeling and installing a specific system to prevent ice is a necessity. Therefore, aircraft designers developed an anti-icing system inside the wing to prevent ice.

There are several anti-icing systems on aircraft, mostly depending of the engine’s type. Most of aircrafts use the bleed air system, which consists of using a hot bleed air to warm up the wing leading edge. Another system named de-icing boots system is mostly used on turboprop aircrafts and consists of black rubbers at locations prone to icing which inflate and literally break the ice. Another system is simply an electrical leading edge warm up directly installed in the wing leading edge. Those examples are just an introduction to some anti-icing systems that aircraft industry has develop and are using. Each have pros and cons.

Here, we will focus on the anti-icing system using hot bleed air. This approach is used by the Boeing 737-300/400/500 anti-icing system with hot bleed air warming the leading edges.

Typically, this type of anti-icing system consists of a hot bleed air flow provided by the engine compressor’s stages to warm up the plane’s wing leading edge. The wing anti-icing system is made of two independent pneumatic systems among others, providing hot bleed air from each of the two turbofans separately. The hot bleed air is ducted via the engine bleed valve from the fifth compressor stage. If the pressure isn’t enough, bleed from the ninth compressor stage can additionally be used. Note that the fifth stage bleed air temperature is approximately 340°C and the ninth stage one is approximately 540°C which are too hot to be used in aircraft’s pneumatic systems such as hydraulic pressurization or potable water system pressurization for example. The hot air then runs through a pre-cooler to reduce the temperature to 200°C and this cooled air is distributed via the bleed ducts to consumers like the air conditioning packs for example and the wing anti-icing system. In order to know the moment to use the anti-icing system, the aircraft’s pilots use the visual ice indicator which is situated in the middle beam of the window. Once the probe is icing, the pilots enable the anti-icing system. Hence, hot bleed air is provided to the slates number three, four and five as shown in Figure 1.

Landing Edge Slats
Figure 1 – Leading Edge Slats

Due to the larger diameter and the aerodynamics phenomena, slates number one and two do not need any anti-icing devices. Once the anti-icing system is enabled, the hot bleed air is guided along telescopic pipes then is distributed via piccolo tubes as shown in Figure 2. From there, it exits the piccolo tubes through little holes, warms the wing leading edge and flows out of the wing through exit holes situating on the wing’s lower surface. Read More

A Brief History of the Turbocharger – Part 1

Turbochargers are one of the more common turbomachines out there today! As everyone is making efforts to lower carbon dioxide emissions in automobiles, and the automotive OEMs engage in a “horsepower war”, the turbocharger will likely continue to grow in popularity for both civil and commercial uses.

But how did these machines get so popular? That’s what we’ll be exploring in this blog miniseries! Today’s blog will introduce the concept of the turbocharger, and the beginnings of its development around the turn of the 20th century.

Turbocharging engines and the idea of forced induction on internal combustion engines are as old as the engines themselves. Their intertwined history can be traced back to the 1880’s, when Gottlieb Daimler was tinkering with the idea of forced induction on a “grandfather clock” engine. Daimler was supposedly the first to apply the principles of supercharging an engine in 1900, when he mounted a roots-style supercharger to a 4-stroke engine.

The birth of the turbocharger, however, would come 5 years later, when Swiss engineer Alfred Büchi received a patent for an axial compressor driven by an axial turbine on a common shaft with the piston of the engine. Although this design wasn’t feasible at the time due to a lack of viable materials, the idea was there.

Turbochargers vs Superchargers

What idea was that, exactly? And how did it differ from supercharging?

I think it’s important to quickly go over the basic differences between turbocharging and supercharging. Both offer “forced induction” for piston engines. A naturally aspirated engine simply will draw in atmospheric air as the intake valve opens, and the piston travels down to bottom dead center. A forced induction engine, pushes more air into the cylinder than what the dropping of the piston would pull in, allowing more air to be combusted, and thus generating more power and efficiency. While turbochargers and superchargers are both forced induction , how superchargers and turbochargers go about compressing that air is different. Superchargers are driven by the engine themselves, typically via a belt or gear. This uses some of the engine’s available horsepower, but doing so provides more horsepower back to the engine. The compressors can be either positive displacement configurations (such as a Roots or Twin-Screw), or a  centrifugal supercharger.

supercharger configurations
A very helpful image of the 3 kinds of superchargers, courtesy of MechanicalBooster.com

Turbochargers, as mentioned before, use the air from the exhaust of the engine to drive a turbine, and the work of the turbine is transmitted on a common shaft to a compressor. The most common configuration is a radial turbine driving a centrifugal compressor similar to the one above in the supercharger diagram. However, there are other configurations ,seen in larger examples, such as an axial turbine driving a centrifugal compressor. Read More

It’s Rocket Science – and it’s Dangerous!

Rockets have always fascinated us and to this day a rocket launch is still a global news event worth watching. The sheer noise, power and sight after you hear that “…3-2-1, Lift off!” leave us in awe. A masterpiece of engineering, the recent historic manned SpaceX Falcon 9 launch was no exception. Or was it?

The beginnings

From the outside, a rocket does not look especially advanced – a mere ‘stick’ with a big flame shooting out at one end. The principal concept is simple, too, but the inner workings of a modern liquid-fuel rocket are highly complex.

The first rockets are believed to have existed in China, around 1200. The invention of gunpowder was crucial to the development of these primitive rockets, which were fireworks initially and then weapons. Multistage so-called ‘fire arrows’ were documented during the early Ming Dynasty (Figure 1). The designs were based on bamboo sticks – still a little way off a Falcon 9.

Figure 1: The oldest known depiction of multistage rocket arrows, from 14th-century China. The top arrow reads ‘fire arrow’, the middle ‘dragon-shaped arrow frame’, and the bottom’complete fire arrow’. Source

With the rise of gunpowder, this crude rocket technology spread throughout the Middle East and Europe.

The next rocketry milestone came in the 1780s, when the Indian military developed Mysorean rockets with iron castings and successfully deployed them against the British East India Company. Read More

Engineering Luke Skywalker’s X-34 Landspeeder

Today, landspeeders we look at!

Introduction

Landspeeders belong to the “repulsorlift” transport class, like the podracers we looked at last year, and travel above a world’s surface (up to 2 meters) without contact (very useful on swampy lands like Dagobah). Landspeeders are the successors to the hanno speeder which was mainly used as a racing vehicle with many Tatooine natives still using them to race in the Boona Eve Classic today.

Luke Skywalkers Soro Suub Corporation X-34 landspeeder
Figure 1:  Luke Skywalker’s Soro Suub Corporation X-34 landspeeder from the 1977 film – Note, the Soro Suub Corporation was your main go-to landspeeder designer and manufacturer before and during the reign of the Galactic Empire even though it specialized mostly in mineral processing. Image source

Landspeeders are found in both civilian and military applications but due to intergalactic ITAR regulations we will only cover the civil aspect here with a focus on the most famous of them all. If you want to know more about our experience working with military, defense and governmental organizations (whether you area part of the Empire, Rebels, Resistance or Separatists) feel free to contact us.

The Famous X-34

Luke Skywalker’s X-34, with its 6 selectable hover heights, features an engine consisting of 3 air-cooled thrust gas turbines able to reach a top speed of about 155 mph. The side engines are also used for steering although it is not obvious whether this steering is achieved by varying their thrust to be asymmetric or through vectoring of their exhaust. With the X-34 total length being 3.4 meters it helps us estimate the overall dimensions of its engines which are, each, roughly 80 cm long by 30 cm wide. Read More

An Introduction to Shock Waves

When you think of shock waves, I would wager that you picture a supersonic jet zooming past overhead. Or maybe you have experienced the famous (or infamous) “sonic boom” that accompanies shock waves attached to airplane engines. The engineering challenges associated with the often-troublesome behavior of shock waves is present in all scales, from carefully designing the bodywork of the aforementioned fighter jets, to the equally intricate details of flow passages and blade design in turbomachinery. The first step in taking into account the effect of shock waves is to understand what they are. In this post we will be reviewing a short introduction into what shock waves are and a few applications where they might be relevant.

Figure 1: Schlieren image showing the shock waves of a supersonic jet
Figure 1: Schlieren image showing the shock waves of a supersonic jet. Source

What are shock waves?

Shockwaves are non-isentropic pressure perturbations of finite amplitude and from the second law of thermodynamics we can say that shockwaves only form when the Mach number of the flow is larger than 1. We can distinguish between normal shocks and oblique shocks. In normal shocks, total temperature is constant across the shock, total pressure decreases and static temperature and pressure both increase. Across oblique shocks, flow direction changes in addition to pressure rise and velocity decrease. Read More

Micro Gas Turbines in the Aerospace Industry

Previous Blog  Next Blog

Hello and welcome to the next entry in our series on micro gas turbines! If you’re new to this series, be sure to check out our earlier blog where we: introduce the concept of the micro gas turbine; look into the history of it; and discuss some advantages and disadvantages that come with this technology.

This time, we’ll be looking at micro gas turbines in the Aviation industry (if you couldn’t guess by the title). Believe it or not, the concept and configuration of a micro gas turbine has been present in this industry for decades. We’ll get into that in a minute.

Gas turbines are certainly no stranger to the aviation industry. As a matter of fact, when many of us hear the term “gas turbine” we immediately jump to the image of a jet engine powering a massive airliner carrying us to our next adventure.

Engine of airplane
The Mighty Turbofan Engine; Brought about with thanks to Sir Frank Whittle!

Yes, these mighty turbines are indeed a staple in the aerospace industry.  But did you know that micro gas turbines are also making a rise in this industry?

Although micro gas turbines first made an appearance as an alternative to traditional piston engines in the automotive industry, they have actually been present in the aviation industry for some time.

Read More

The Life of Frank Whittle and His Massive Contribution to Turbomachinery

While we at SoftInWay are known for helpful articles about designing various machines and answering questions about the pros and cons of retrofitting your turbomachinery and powerplants, we believe it is important to also examine the lives of some of the men and women behind these great machines that do so much for the world.

Frank Whittle - Image Courtesy of The Telegraph
Frank Whittle – Image Courtesy of The Telegraph

The jet engine is one of the greatest inventions of the last 100 years. It has made transcontinental travel considerably shorter. A trip that might take days on a piston driven aircraft was cut down to hours thanks to the inception of the jet engine. To this day, millions of people rely on jet engines daily for everything from themselves for vacation travel to their packages for shipping goods overnight. These engines also give the U.S. military the ability to deploy to any part of the world within 18 hours.

But who invented the jet engine? This credit changes depending on who you ask.  Some might answer it was Hans von Ohain.  To others, this credit belongs to Sir Frank Whittle, OM, KBE, CB, FRS, FRAeS, RAF.

Why the discrepancy? von Ohain is known for creating the world’s first operational jet engine, and Whittle is credited with developing the turbojet earlier. While von Ohain’s first engine was the first to fly operationally in 1939, Sir Frank Whittle had been working on his design since the 1920’s. Today, we’d like to look at the life of Sir Frank Whittle, and how he created this world-changing machine. Read More