Internal Combustion Engine Heat Recovery for Part-Load Efficiency
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Solution Overview
Problem
Internal combustion engines face limitations in achieving high efficiency due to energy losses and high exhaust temperatures, particularly under low or moderate load conditions, where current technologies either compromise on fuel consumption or increase emissions.
Innovation Solution
The engine employs a heat transfer mechanism that pre-compresses and heats the working gas before combustion, using a heat exchanger to increase the gas temperature and reduce exhaust temperature, thereby enhancing the thermodynamic cycle efficiency without significant increases in weight, space, or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the expansion of the working gas is extended beyond the volume corresponding to the beginning of compression, then the energy losses are reduced, but the maximum size of the working chamber must be considerably increased
Solution Approach 1:
The expansion process is divided into two distinct stages: first, expansion within the working chamber of the internal combustion engine, and second, continued expansion in an external expansion chamber. This segmentation allows the gas to expand beyond the original chamber volume without requiring a single oversized chamber, thereby reducing energy losses while maintaining compact overall dimensions.
Solution Approach 2:
The expansion process transitions from a confined three-dimensional space (working chamber) to an additional spatial dimension (external expansion chamber). This dimensional extension enables the gas to perform additional work during expansion without increasing the footprint of the original engine components, effectively capturing more energy from the same fuel input.
2Power
If supercharging is used to reduce displacement, then power and torque are increased, but additional loss occurs due to greater pressure differential
Solution Approach 1:
The high-pressure differential generated by supercharging, which normally represents energy loss, is converted into a beneficial resource. The expanded gas from the external expansion chamber, now at lower pressure, is recirculated through the supercharger inlet. This allows the supercharger to compress already-expanded gas rather than fresh atmospheric air, reducing the work required and converting the pressure differential from a loss into a mechanism for improving overall cycle efficiency.
Solution Approach 2:
Instead of discarding the exhaust gases after they leave the working chamber, the system recovers their remaining expansion energy in the external expansion chamber. The partially expanded gas is then recirculated back through the supercharger, recovering additional work potential that would otherwise be lost in conventional systems.
3Quantity of substance
If intercooler is used to cool pre-compressed gas, then gas mass processed is increased, but temperature of gas entering working chamber is decreased
Solution Approach 1:
The external expansion chamber performs preliminary expansion of the exhaust gases before they are recirculated to the supercharger inlet. This preliminary action reduces the pressure and temperature of the recirculated gas, allowing the supercharger to process larger masses of gas without excessive temperature rise, thereby increasing the effective gas mass processed while maintaining optimal combustion 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 approach significantly improves the engine's yield by increasing the combustion temperature and reducing exhaust gas temperature, leading to better fuel efficiency and reduced emissions, especially under part-load conditions, while maintaining stress levels within conventional limits.
Implementation Method 1
heat transfer means which, during warm engine operation, withdraws heat from the discharged working gas travelling downstream of the positive displacement mechanism at a second pressure lower than the first pressure, and yielding the heat to the pre-compressed working gas
Implementation Method 2
means for pre-compression and volume reduction or compressor system for effecting pre-compression and volume reduction of a working gas, thereby to obtain a pre-compressed working gas at a first pressure
Implementation Method 3
heating by combustion near a top dead center of the movable member or piston
Implementation Method 4
The gas exiting from its initial expansion step undergoes a complementary expansion in the turbine of the supercharger
Data Source
AI summary
In an internal combustion engine, for the operation at part-load, a heat exchanger collects heat from the exhaust gas and re-injects the collected heat into the intake gas being at an intermediate stage (p3c) of the compression. The exhaust gases are cooled down from point Q81c to point Q61c. The intake gases are heated up from point Q33c to point Q43c. The average combustion temperature is higher while the exhaust gas temperature is lowered, wherefore the yield is definitely increased.