Powertrain Warm-Up Optimization Involving Simplified Split Cooling with Integrated Exhaust Heat Recovery and Reuse
The test results published earlier have proven that the previously proposed engine cooling circuit when combined with exhaust heat recovery and reuse could expedite the warm-up process after cold start and has improved the fuel economy by up to 4%. With the evolution of the earlier concept, the study discussed in this paper explores further improvements to the cooling circuit to expedite the warm-up process. In particular, with some changes to the cooling circuit, the heat recovered from the exhaust gas is reusable right away to heat up the heat exchangers for engine oil, CVT oil and cabin heater. Next, the thermostat opening temperature and leakage rate can also be optimized to prolong the heat recirculation and preservation periods. Finally, the coolant flow rate across the heat recovery unit can also be varied as a function of time right after the cold-start. These additional measures although capable of improving the warm-up process come with limitations.