Compound Cycle Engine Velocity Turbine Back Pressure Reduction
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Solution Overview
Problem
Existing compound cycle engines with rotary engines have limited available power for turbo compounding and performance, particularly at start-up, due to the use of pressure turbines downstream of the turbocharger turbine, which restricts the pressure ratio and increases back pressure and thermal loads.
Innovation Solution
Incorporating a velocity turbine as the power turbine, configured to rotate using kinetic energy from exhaust pulses, with a pressure ratio smaller than the turbocharger turbine, allowing for increased power availability and reduced back pressure, and eliminating the need for a large volume exhaust collector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a pressure turbine is used downstream of the turbocharger turbine, then the turbine can extract energy from exhaust gases, but the pressure ratio is restricted and back pressure increases
Solution Approach 1:
An exhaust collector is introduced as an intermediary component between the rotary engine exhaust port and the velocity turbine inlet. This collector accumulates exhaust pulses and directs them to the velocity turbine, enabling the turbine to operate at optimal pressure ratios while reducing back pressure on the engine.
Solution Approach 2:
The patent changes the operating parameters of the turbine by selecting a velocity turbine type with a lower pressure ratio compared to traditional pressure turbines. This parameter change allows the turbine to extract kinetic energy efficiently without creating excessive back pressure, thereby improving power availability.
2Power
If a velocity turbine with smaller pressure ratio is used, then power availability increases and back pressure decreases, but the turbine configuration becomes more complex
Solution Approach 1:
The turbine system is segmented into two distinct components: a velocity turbine for power extraction and an exhaust collector for pulse management. This segmentation allows each component to be optimized independently - the velocity turbine for low pressure ratio operation and the collector for pulse accumulation - simplifying the overall design while maintaining performance.
3Device complexity
If exhaust pulses are directed directly to the turbine, then the system is simpler, but thermal loads on the turbine increase
Solution Approach 1:
The exhaust collector acts as a cushioning chamber that receives and temporarily stores hot exhaust pulses before directing them to the velocity turbine. This beforehand cushioning effect reduces peak thermal loads on the turbine by distributing the thermal energy over time, protecting the turbine from excessive temperatures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances power availability for turbo compounding, maximizes volumetric efficiency, minimizes thermal loads, and improves start-up performance without compromising the rotary engine's efficiency, while allowing the power turbine to be located upstream of the compound turbine.
Implementation Method 1
the first turbine is configured as a velocity turbine, the blades of the first turbine being configured to rotate the first turbine rotor in response to kinetic energy imparted by impingement of the exhaust pulses against the blades
Data Source
AI summary
A compound cycle engine having a rotary internal combustion engine, a first turbine, and a second turbine is discussed. The exhaust port of the internal combustion engine is in fluid communication with the flowpath of the first turbine upstream of its rotor. The rotors of the first turbine and of each rotary unit drive a common load. The inlet of the second turbine is in fluid communication with the flowpath of the first turbine downstream of its rotor. The first turbine is configured as a velocity turbine and the first turbine has a pressure ratio smaller than that of the second turbine. A method of compounding a rotary engine is also discussed.