Our following story traces the development of the Trent 700 gas turbine engine to the recently announced Trent 7000 at Rolls Royce.
Gas turbine engines are designed specifically for the aircraft they will ultimately power. The Rolls-Royce Trent 700 high-bypass turbofan was, as a result, designed to power the Airbus A330. As such, Cathay Pacific negotiated to become the first customer for this engine, making their selection in April 1989. The Trent 700 completed its certification tests following this negotiation and was subsequently put into service on March 24, 1995.
Unique features of this engine were that it had a three-shaft architecture. Using three shafts, the engine designers could connect one of the turbines to the fan section, and then the other two shafts connected different turbines to different compressor sections. Three shafts meant the best combination of turbines driving the fan and compressor sections, each spinning independently and optimizing engine performance.
Figure 1 breaks out the fan and compressor parts as well as the technical data for the Trent 700 Gas Turbine engine.
Figure 1: The Trent 700, Fan And Compressor Parts and Technical Data
Figure 2 provides a cut-away vertical view of the three-shaft architecture of the Trent 700, by using colour separation of certain key pieces .
Figure 2 – A Diagram of the 3 Shaft Rolls-Royce Architecture
In Figure 2, the blue spool (horizontal centre of picture) connects the low-pressure (LP) fan and turbine, the green spool connects the intermediate-pressure (IP) compressors and turbine, and the red spool connects the high-pressure (HP) compressors and turbine.
In the 3-shaft gas turbine engines, each compressor is rotated at a speed equivalent to the pressure ratio that it can achieve. This means the low-pressure compressor turns at a lower RPM than the intermediate compressor, and the intermediate rotates at a lower RPM than the high-pressure compressor. This way, the airflow over the compressor blades is efficient, and there is no risk of a compressor stall.
With its 97.4 in (247 cm) fan for a 5:1 bypass ratio, the Trent 700 produced 67,500-71,100 lbf[1] of thrust and reached an overall pressure ratio of 36:1.
Market success for this design was great; by July 1999, the Trent had secured a nearly 40% share of engine orders for the A330. Two subsequent upgrades were also produced for the Trent 700, each improving fuel consumption.
By July 2018, the Trent 700 had flown 50 million hours, and Rolls-Royce claimed an improved 60% share in this market segment. One aviation company could even claim a record for a wide-body engine in this timeline of completing over 50,000 hours without requiring an overhaul.
With time, these gas turbine engine designs continued to be improved. The previous CEO (Current Engine Option) on many aircraft was subsequently upgraded to NEO (New Engine Option). In this case, NEO also came in the form of a new engine which was named the Trent 7000.
So, the Trent 700 was now superseded by the Trent 7000. The Trent 7000 was announced in July 2014 at the Farnborough Airshow and, at that time, became the exclusive engine for the Airbus A330neo.
Figure 3 – Airbus A330 with Trent 7000 Engines Flies at the Farnborough Airshow, 2014
Pandemic Effects On Wide Bodied Aircraft
Despite some predictions of the demise of wide-bodied aircraft[2], the post-pandemic period has forstalled this effect. Principally this has happened because of increased aviation travel demand and the inability of the aviation industry to recover from its pandemic period downsizing.
Wide-bodied aircraft were quickly assigned to support this demand and they responded very capably to these challenges for international and long-distance routes. Crew levels in wide-body aircraft are also relatively smaller as passenger loading is higher. While being expensive in some ways to operate, wide-bodied aircraft can move up to 50% more passengers than single-bodied aircraft, and as a result, the A330 has performed well in this service. The suggestion now is that these aviation conditions will remain for the mid-term future.
Introduction of the Trent 7000
The Trent 700’s 40 million+ hours in service and 60% of the total A330 market share have ensured a smooth service introduction for the Trent 7000 in 2014.
Figure 4: A Video of the Trent 7000
The Trent 7000 has the highest bypass ratio of any Trent engine at >10:1, enabling an overall compression ratio of 50:1. This gas turbine engine, like its predecessor, also appropriately offers 68k-72k lbf of thrust.
Figure 5: Trent 7000 Under Test in Derby, UK
In fuel burn, the Trent 7000 SFC (Specific Fuel Consumption) is 10% better than the Trent 700 and, with other enhancements, enables Airbus with an overall 14% aircraft fuel burn improvement.
Figure 6: Trent 7000 Installation on Airbus A330neo – Prep for First Flight
Today there are over 170 Trent 7000 in service flying A330 aircraft. A further 370 of these gas turbine engines are slated for delivery in the coming years.
[1] Lbf – pounds of force
[2] https://www.forbes.com/sites/benbaldanza/2021/02/26/airlines-will-need-fewer-wide-body-aircraft-post-pandemic/?sh=4c18