Split Cycle Waste Heat Method for GCI Engine Combustion
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Solution Overview
Problem
Transitioning from Low Temperature Combustion (LTC) mode to Gasoline Compression Ignition (GCI) mode in multimode GCI engines is challenging due to insufficient exhaust enthalpy providing inadequate boost for GCI combustion, as existing variable compressor turbochargers fail to deliver high boost levels at low flow rates required for mode transitions.
Innovation Solution
The method involves discrete camshaft operation and CVVD mechanisms to transition engine cylinders between Spark Ignition (SI), LTC, and GCI modes, with specific timing and airflow control strategies to build exhaust energy and provide necessary boost for GCI mode initiation, allowing independent operation of cylinder pairs to manage different camshaft timings and overlaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a variable compressor turbocharger is used to extend the compressor map, then the available boost levels are increased with reduced exhaust energy input, but the turbocharger is still incapable of providing very high boost levels at the low flow rates required for LTC to GCI transitions
Solution Approach 1:
The engine cylinders are divided into two separate pairs, with each pair operating in different combustion modes (LTC and GCI). This segmentation allows each cylinder pair to independently contribute to exhaust enthalpy generation, enabling the turbocharger to receive sufficient total exhaust energy even when individual cylinder pairs operate at low flow rates during mode transition
Solution Approach 2:
The LTC cylinder pair operates in advance to build up exhaust enthalpy and turbocharger boost pressure before the GCI mode is initiated in the other cylinder pair. This preliminary action of generating exhaust energy allows the system to reach the necessary conditions for GCI combustion without requiring the GCI cylinders to immediately provide high flow rates
2Productivity
If the LTC mode is used to allow increased speed/load operating points, then the engine can operate beyond spark ignition capability, but the low exhaust temperature/enthalpy in LTC mode provides insufficient energy to the turbocharger to generate the boost required for GCI combustion
Solution Approach 1:
The exhaust energy generation is segmented between two cylinder pairs operating in different modes. The LTC pair maintains low-temperature combustion for efficiency and emissions, while the GCI pair provides high-temperature exhaust to generate sufficient enthalpy for turbocharger boost, resolving the energy deficiency of single-mode LTC operation
Solution Approach 2:
The exhaust streams from two differently modeed cylinder pairs are merged in the turbocharger inlet. This combination of exhaust flows with different temperature and enthalpy characteristics allows the turbocharger to receive adequate total energy to generate the high boost levels needed for GCI combustion while maintaining the efficiency benefits of LTC operation in one pair
3Adaptability or versatility
If multiple turbochargers are used with switching valves to provide proper turbo for different operating conditions, then sufficient boost can be provided for each mode, but the system complexity increases and a method for transitioning between turbos during mode switch is required
Solution Approach 1:
A single turbocharger is designed to handle multiple operating conditions by receiving exhaust from two cylinder pairs that can operate in different modes. The turbocharger becomes a universal component that can process both low-enthalpy LTC exhaust and high-enthalpy GCI exhaust, eliminating the need for multiple specialized turbochargers and switching valves
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 enables smooth and efficient transition from LTC to GCI mode by increasing exhaust energy and providing sufficient boost, allowing stable GCI combustion while maintaining fuel economy and emissions benefits, with independent control of cylinder pairs to manage different operating conditions.
Implementation Method 1
discrete camshaft operation for different pairs of the combustion cylinders
Implementation Method 2
Spark Ignition (SI) mode
Implementation Method 3
Low temperature Combustion (LTC) mode
Implementation Method 4
Gasoline Compression Ignition (GCI) mode
Implementation Method 5
exhaust enthalpy to provide the boost needed to initiate GCI combustion
Data Source
AI summary
Systems and methods for having discrete valve opening and closing timings for different pairs of the combustion cylinders, and transitioning an engine from a Low temperature Combustion (LTC) mode to a Gasoline Compression Ignition (GCI) mode are provided. The method may comprise performing a cold start on an engine, comprising at least two sets of cylinders, in a Spark Ignition (SI) mode. The method may comprise, using a discrete camshaft operation for different pairs of the combustion cylinders to run the at least two sets of cylinders in the LTC mode, and when a load operation point of the engine increases, transitioning a first set of cylinders, of the at least two sets of cylinders, to run in a SI mode, and, after the first set of cylinders is transitioned to run in the SI mode, transitioning the second set of cylinders to run in the GCI mode, and, after the second set of cylinders is transitioned to run in the GCI mode, transitioning the first set of cylinders to run in the GCI mode.