Wankel Engine Rotary Expander for Thermal Efficiency
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Solution Overview
Problem
Series hybrid vehicles face limitations in range due to battery weight and energy capacity, requiring a power unit with low weight, low specific fuel consumption, low noise and vibration, low emissions, and high reliability, which existing Wankel engines do not adequately meet.
Innovation Solution
A power unit combining a spark-ignition Wankel engine with a rotary expander unit, achieving a combined expansion ratio of at least 22:1 by connecting the exhaust port of the engine unit to the inlet port of the expander unit, allowing further expansion of exhaust gases and improving thermal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a single rotor Wankel engine is used, then weight and size are reduced, but thermal efficiency and power output are insufficient
Solution Approach 1:
The engine is divided into two separate rotor units: a first rotor (3-cornered) for compression ignition and a second rotor (2-cornered) for expansion. This segmentation allows each rotor to be optimized for its specific function while maintaining the overall lightweight Wankel architecture, resolving the contradiction between low weight and adequate power output.
Solution Approach 2:
The patent combines two rotor units with different configurations into a single integrated engine system. The first rotor handles compression and power generation, while the second rotor handles expansion and waste heat recovery. This merging of functions increases total power output while maintaining the compact, lightweight Wankel design philosophy.
2Use of energy by moving object
If compression ratio is increased to improve thermal efficiency, then thermal efficiency increases, but mechanical friction losses increase
Solution Approach 1:
The compression and expansion processes are separated into two distinct rotor units. The first rotor achieves high compression ratio (15:1-20:1) for thermal efficiency, while the second rotor handles expansion at lower pressure. This segmentation allows high compression without proportionally increasing friction losses, as each rotor operates within optimized parameters.
Solution Approach 2:
The connecting passage (13) acts as an intermediary between the two rotor units, allowing controlled transfer of exhaust gases from the first rotor to the second rotor. This intermediary mechanism enables the expansion process to occur separately from compression, allowing high compression ratio without the full brunt of friction losses affecting both processes simultaneously.
3Power
If a multi-cylinder reciprocating engine is used, then power output and efficiency are improved, but weight and complexity increase
Solution Approach 1:
Instead of using a complex multi-cylinder reciprocating engine, the patent segments the function into two simple rotor units with different geometries. Each rotor is a simplified Wankel design, avoiding the complexity of multiple pistons, valves, and connecting rods while achieving comparable or superior power output through the combined effect of compression and expansion.
Solution Approach 2:
The patent employs dynamic rotor geometries (3-cornered and 2-cornered rotors) that can adapt their compression and expansion ratios during operation. This dynamic capability allows the engine to optimize power output across different operating conditions without the mechanical complexity of traditional multi-cylinder reciprocating engines.
4Device complexity
If exhaust gases are directly discharged, then system complexity is minimized, but noise and emissions increase
Solution Approach 1:
The patent merges the exhaust system with the second rotor unit, using the expansion chamber as an integrated part of the power generation system. Exhaust gases from the first rotor are directed through a connecting passage to the second rotor, where they undergo controlled expansion before discharge. This integration reduces noise and emissions by gradually expanding and cooling the gases rather than direct discharge, while adding minimal system complexity.
Solution Approach 2:
The connecting passage (13) and second rotor unit act as intermediaries between the exhaust source and the environment. This intermediary system allows exhaust gases to be gradually expanded and cooled through the second rotor's expansion chamber, reducing the sudden release of hot, noisy, and polluting exhaust gases, thereby lowering noise and emissions with minimal added complexity.
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
The solution increases power output by 20% and reduces specific fuel consumption and emissions by 20%, while significantly lowering exhaust noise and emissions, making it suitable for series hybrid vehicles.
Implementation Method 1
the exhaust gasses from the engine unit are further expanded in the expander unit
Implementation Method 2
a three flanked rotary piston mounted on an eccentric shaft rotating eccentrically within a cavity within a two lobed epitroochoidal inner peripheral surface
Data Source
AI summary
A power unit (14) which has a spark-ignition engine unit (1) of the Wankel type including a three flanked rotary piston (R) mounted on an eccentric shaft (63) rotating eccentrically within a cavity within a two lobed epitroochoidal inner peripheral surface (14), the cavity including an inlet port (7) through which air at ambient pressure is induced into the working chambers, and an outlet port (45) through which exhaust gasses are exhausted from the working chambers, and the power unit also including a rotary expander unit (4) which has a two flanked rotor (24) mounted on an eccentric shaft (12) rotating eccentrically within a single lobed epitrochoidal chamber (25), both shafts (62, 63) being coupled to rotate together, and the exhaust port (45) of epitrochoidal cavity of the engine unit (1) being connected to an inlet port (26) of the expander unit (4) so that the exhaust gasses from the engine unit (1) are further expanded in the expander unit (4).