Engine Waste Heat Recovery Using Dynamic Cooling Water Temperature Control
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Solution Overview
Problem
Existing engine-waste-heat utilization devices using Rankine cycles do not effectively manage cooling water temperature, which affects heat recovery efficiency when the cycle is operated or not operated.
Innovation Solution
An engine-waste-heat utilization device with a Rankine cycle that includes a heat exchanger, expander, condenser, refrigerant pump, and a cooling water passage that maintains a higher temperature when the cycle is operated, utilizing an electronically controlled thermostat valve to adjust cooling water flow and temperature based on operational states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cooling water temperature is increased to improve heat recovery efficiency of the expander, then heat recovery efficiency is improved, but engine knocking risk increases
Solution Approach 1:
The cooling water temperature is made dynamically adjustable based on engine operating conditions. The control unit monitors engine parameters and actively regulates cooling water temperature to be higher when the Rankine cycle is operating (improving heat recovery) and lower when it is not operating (preventing knocking), thus dynamically optimizing the trade-off between these conflicting requirements.
Solution Approach 2:
The invention changes the temperature parameter of cooling water based on the operational state of the Rankine cycle. By setting different temperature levels corresponding to different operational modes (cycle operating vs. cycle not operating), the system optimizes heat recovery efficiency while preventing engine knocking through parameter adjustment.
2Reliability
If cooling water temperature is decreased to prevent engine knocking, then knocking is prevented, but heat recovery efficiency of the expander decreases
Solution Approach 1:
The system dynamically adjusts cooling water temperature based on whether the Rankine cycle is operating. When the cycle is not operating, lower temperature prevents knocking and maintains engine reliability. When the cycle is operating, higher temperature maximizes heat recovery efficiency. This dynamic adaptation resolves the contradiction between reliability and productivity.
Solution Approach 2:
The invention implements parameter changes in cooling water temperature according to operational state. By lowering temperature when the Rankine cycle is not operating, the system prevents knocking and protects engine reliability, while accepting reduced heat recovery efficiency only when the cycle is inactive.
3Device complexity
If a mechanical thermostat valve is used to control cooling water flow, then结构简单 (structure is simple), but cooling water temperature cannot be adjusted based on Rankine cycle operation state
Solution Approach 1:
The invention replaces the mechanical thermostat valve with an electronically controlled valve system. This substitution eliminates the limitations of mechanical thermostats by enabling active control of cooling water temperature based on Rankine cycle operation state, thereby achieving both low complexity and high adaptability through electronic control.
Solution Approach 2:
The control unit acts as an intermediary between the Rankine cycle operation state and the cooling water flow control. It receives information about cycle operation and translates it into appropriate cooling water temperature adjustments, enabling the system to adapt to different operational states while maintaining a relatively simple overall structure.
Data Source
Figure 1
Figure 2A
Figure 2B~2C
AI summary
An engine-waste-heat utilization device includes a Rankine cycle which includes a heat exchanger through which cooling water coming out from an engine flows to recover waste-heat of the engine to refrigerant, an expander which generates power using the refrigerant coming out from the heat exchanger, a condenser which condenses the refrigerant coming out from the expander and a refrigerant pump which supplies the refrigerant coming out from the condenser to the heat exchanger, and a cooling water passage in which the cooling water having a higher temperature flows when the Rankine cycle is operated than when the Rankine cycle is not operated.