Split Cycle Engine Water Injection for Compression Work Reduction
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Solution Overview
Problem
In split cycle internal combustion engines, the compression process generates significant heat, leading to increased compression work and reduced power output, as the heat generated during compression is not effectively managed, which can limit the engine's efficiency and performance.
Innovation Solution
Introducing a controlled amount of coolant, such as water, into the compression cylinder during the compression stroke to absorb heat via both sensible and latent heat, allowing most of the water to vaporize and reduce the temperature rise, thereby reducing compression work while ensuring the working fluid remains capable of combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If water is delivered into the compression cylinder during compression stroke to absorb heat, then compression work is reduced, but water concentration in compressed working fluid may exceed threshold level
Solution Approach 1:
The controller dynamically adjusts the mass of water delivered to the compression cylinder based on detected engine parameters (temperature, pressure, load conditions). By varying water mass within a range that ensures heat absorption while maintaining water concentration below the combustion threshold, the system optimizes compression work reduction without compromising combustion capability.
Solution Approach 2:
The system incorporates sensors to detect engine parameters such as temperature and pressure, and uses this feedback information to control the water injection amount. The controller continuously monitors water concentration levels and adjusts delivery accordingly to maintain optimal conditions for both heat absorption and combustion sustainability.
2Temperature
If water is delivered into the compression cylinder to absorb heat via latent heat, then temperature rise is limited, but water must be vaporized which requires additional energy
Solution Approach 1:
The system utilizes the phase transition of water from liquid to vapor during compression, where water absorbs latent heat from the compressed air, effectively limiting temperature rise. The controller ensures sufficient water mass is delivered to achieve complete vaporization and maximum heat absorption, transforming the vaporization energy requirement into a beneficial cooling effect.
Solution Approach 2:
The system converts the potentially harmful effect of water addition (increased mass, potential combustion interference) into a beneficial cooling mechanism. By controlling water delivery to achieve complete vaporization, the latent heat absorption effect is harnessed to reduce compression temperature, transforming what could be a disadvantage into a significant thermal management advantage.
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 approach significantly reduces compression work, potentially increasing power output for a given mass of working fluid, while maintaining the ability to sustain combustion without the need to remove the coolant from the compressed fluid, thus enhancing engine efficiency and performance.
Implementation Method 1
the water absorbs the rise in temperature via both sensible heat and latent heat
Implementation Method 2
the water absorbs the rise in temperature via both sensible heat and latent heat
Implementation Method 3
at least some of, and in some examples a majority of (and in some examples substantially all of), the water vaporises into its gaseous phase during the compression stoke
Data Source
AI summary
A split cycle internal combustion engine comprises a combustion cylinder and a compression cylinder arranged to receive air and compress the air to provide a compressed working fluid to the combustion cylinder for combustion. The compression cylinder is coupled to a water reservoir. The engine further comprises a controller arranged to receive an indication of at least one parameter associated with the engine and/or a fluid associated therewith, and control delivery of the mass of water delivered to the compression cylinder based on the indication of the at least one parameter such that the total mass of water in the compressed working fluid at the end of the compression stroke results in a level of water concentration in the compressed working fluid that is less than a threshold water concentration level.