THE UNIVERSITY OF NEW SOUTH WALESSCHOOL OF MECHANICAL AND MANUFACTURING

ENGINEERING

AERO3110 AEROSPACE DESIGN

SYSTEMS ASSIGNMENT

Issued: Wednesday, 11 September 2013 Due: Wednesday, 23 October 2013 4:00

PM

ENVIRONMENTAL CONTROL SYSTEM FOR A REGIONAL TRANSPORT

IntroductionIt is the responsibility of the aircraft designer to provide a satisfactory cabin environment for crew, passengers and freight. For many aircraft this involves the provision of a pressurised cabin in which the pressure, temperature, humidity and air quality is controlled.

The air used to control the cabin environment is compressed air drawn as bleed air from an engine compressor. This air is then conditioned and fed to the cabin. The temperature is controlled through a 'bootstrap' reverse heat engine cycle. Cabin pressure is controlled by releasing air from the cabin through a pressure control valve.

Design RequirementsA system should be designed to control cabin temperature and pressure in straight and level flight at sea level, 16,400 ft (5 km) and 32,800 ft (10 km). The bleed air split into the flows through the 'bootstrap' and choke, where choke can be adjusted to provide the required cabin temperature. Assume adiabatic efficiency is 100%. Take M 0 at sea level and M = 0.8 at both 5 km and 10 km altitudes. Be aware of icing potential of the airflow in the bootstrap cycle. Evaluate the power transfer between the turbine and compressor of the bootstrap.

Aircraft Data

Passengers and crew heat generation 120 W per personSolar Radiation 1.0 kW m-² (windows

only)Conduction through walls 1.4 W m-² K-1

Flow of air requirement 0.4 kg min-1 per personCabin temperature required 20°CMax. aircraft altitude 32,800 ft (10 km)Max. cabin altitude 6,560 ft (2 km)Window effective area (total) 4.0 m²Wall surface area 3 m² per person

Number of passengers and crew 60Electronics and electrical heat generation 6 kW

Ignore pressure drop in system.

For normal cruise condition:Bleed air mass flow rate 0.40 kg s-1 Temperature, pressure of bleed air 455 K, 177 kPa abs

Ignore any altitude effects on bleed air conditions.

Design Notes and Hints

(i) It is usual for pressure to be controlled by release of air from the cabin through a differential valve.

(ii) Assume pressure difference between cabin pressure and external pressure is a linear function with a maximum at 10,000 m (32,800 ft) and zero at sea level.

Standard atmospheric ambient pressure ratio, and temperature ratio, at 0, 2, 5 and 10 km altitude are given by:

Altitude Km 0 2 5 10

ft 0 6,560 16,400 32,800

Ambient 1.0 0.785 0.529 0.260

1.0 0.955 0.887 0.767

(iii) Ignore the effect of climb/descent.

(iv) Take minimum HX outlet temperature as flight stagnation temperature.

Submission Format

Page 1 Standard cover sheet

Page 2 Only final values of pressures, temperatures, mass flows, work rates etc. for all three altitudes

Pages 3 on All calculations, assumptions and comments (if any).

Z. Vulovic10 September 2013