Split-Cycle Piston Engine Using Liquid Nitrogen Compression Cooling
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Solution Overview
Problem
Conventional split cycle reciprocating piston engines used in automotive applications face inefficiencies due to the need for substantial water injection and recycling, which increases complexity and reduces power output, and the heat exchanger's high surface area requirement limits power increase during acceleration.
Innovation Solution
Replacing water with liquefied non-oxidizing, non-combustible gases like nitrogen, which reduces the volume needed for thermal capacity and eliminates the need for water recycling, and using a liquid nitrogen generator to produce excess nitrogen for increased power output and regenerative braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If water is injected into the compression cylinder to maintain isothermal compression, then thermal capacity is improved, but device complexity and water consumption increase due to the need for recycling systems
Solution Approach 1:
The patent extracts the water recycling system from the engine configuration, allowing water to be injected for isothermal compression without requiring complex recovery and recycling infrastructure. The water is simply discharged with the exhaust gases, eliminating condensers, cooling fans, and recovery systems while maintaining the thermal benefit of water injection.
Solution Approach 2:
The patent treats water as a disposable substance that is injected into the compression cylinder for its cooling effect and then discarded with the exhaust. This approach accepts water consumption as a trade-off for eliminating complex recycling systems, using inexpensive water that does not need to be recovered or reused.
2Loss of energy
If a large surface area heat exchanger is used to ensure effective heat transfer, then heat exchange efficiency is improved, but the volume of compressed gas storage increases, reducing power output rate
Solution Approach 1:
The patent removes the large surface area heat exchanger from the system, extracting the heat exchange function from a bulky component. Instead, heat transfer occurs directly in the compression cylinder where water is injected, and the compressed hot gas is rapidly expanded in the expansion cylinder, minimizing the need for large storage volume and enabling faster power response.
Solution Approach 2:
The patent skips the intermediate step of storing large volumes of compressed gas in a heat exchanger by rapidly expanding the compressed gas directly in the expansion cylinder. This rushing through the process reduces the time delay in power delivery while maintaining effective heat transfer through direct water injection and rapid expansion.
3Loss of substance
If water is collected and recycled through a condenser, then water consumption is reduced, but engine efficiency decreases due to the cooling fan and complex system
Solution Approach 1:
The patent uses water as a disposable cooling medium that is injected into the compression cylinder and then discharged with the exhaust gases. This approach prioritizes engine efficiency over water conservation, accepting water consumption as a reasonable trade-off for maintaining high engine performance without energy-wasting recycling systems.
Solution Approach 2:
The patent converts what would normally be considered waste (water discharged with exhaust) into an acceptable outcome by eliminating the energy losses associated with water recycling. The small amount of water consumed is offset by the significant gain in engine efficiency from eliminating cooling fans, condensers, and complex recycling infrastructure.
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 use of liquefied nitrogen decreases water consumption, increases engine power output, and allows for energy storage for regenerative braking, enhancing engine efficiency and power delivery.
Implementation Method 1
a liquefied non-oxidising, non combustible gas... which absorbs the heat that is produced so that the compression is at least quasi-isothermal
Implementation Method 2
the compression cylinder having an outlet port which communicates with a first path of a heat exchanger, the expansion cylinder having an inlet port, which communicates with the first path of the heat exchanger
Data Source
AI summary
A split cycle reciprocating piston engine includes a compression cylinder (2) accommodating a compression piston (4) and an expansion cylinder (12) accommodating an expansion piston (14). The compression cylinder (2) has an inlet port (30) for the admission of air and an outlet port (36) which communicates with a first path of a heat exchanger (5). The expansion cylinder (12) has an inlet port (52), which communicates with the first path of the heat exchanger (5), and an outlet port (56), which communicates with a second path of the heat exchanger (5) in heat exchange relationship with the first path. The method of operating the engine includes injecting a liquefied, non-oxidizing, non-combustible gas, such as nitrogen, into the compression cylinder (2).