Split-Cycle Engine Layout With Exhaust Heat Recovery

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Solution Overview

Problem

Existing split-cycle internal combustion engines are not compact enough to fit into vehicle engine compartments without significant modifications, and there is a need for a solution that recovers waste heat efficiently while using existing manufacturing technologies.

Innovation Solution

A split-cycle engine system with a heat exchanger positioned above the cylinder head, separating the compression and expansion sections, and using a volumetric compressor to transfer compressed air efficiently, allowing for compact design and heat recovery.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the heat exchanger is arranged inside the cylinder head (as in US5857436A), then the air channelling is integrated, but the engine dimensions become too large to fit in vehicle engine compartments

Engineering Contradiction:
Improveair channelling integrationVSAvoidengine dimensions
Core Design Contradiction:
Device complexityVSVolume of moving object

Solution Approach 1:

The heat exchanger is repositioned from a horizontal arrangement inside the cylinder head to a vertical arrangement above the cylinder head. This dimensional change allows the heat exchanger to be located in the vertical space above the engine block, reducing the horizontal footprint and enabling the engine to fit within vehicle engine compartments while maintaining integrated air channelling.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If the engine is designed to replace existing four-stroke engines, then compatibility with vehicle spaces is achieved, but significant modifications to manufacturing processes and components are required

Engineering Contradiction:
Improvereplacement compatibilityVSAvoidmanufacturing process modifications
Core Design Contradiction:
Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The engine is divided into distinct compression and expansion sections that can be manufactured separately using existing four-stroke engine manufacturing processes. The compression section includes a compression cylinder with piston and valve mechanism, while the expansion section includes expansion cylinders with similar components. This segmentation allows each section to be produced using conventional manufacturing techniques, reducing the need for significant process modifications.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The engine design utilizes universal components and manufacturing processes that can be applied to both compression and expansion sections. The same piston, valve, and cylinder head manufacturing processes used in conventional four-stroke engines can be applied to the split-cycle engine sections, enabling replacement of existing engines with minimal manufacturing process changes.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Volume of moving object

If the heat exchanger is positioned above the cylinder head, then the engine becomes more compact for vehicle installation, but the air channelling structure requires redesign

Engineering Contradiction:
Improveengine compactnessVSAvoidair channelling structure
Core Design Contradiction:
Volume of moving objectVSDevice complexity

Solution Approach 1:

The heat exchanger is repositioned from a horizontal arrangement inside the cylinder head to a vertical arrangement above the cylinder head. This dimensional change allows the heat exchanger to be located in the vertical space above the engine block, reducing the horizontal footprint and enabling the engine to fit within vehicle engine compartments while maintaining integrated air channelling.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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

The system achieves a compact engine layout compatible with vehicle spaces, improves energy recovery, reduces emissions, and maintains compatibility with existing manufacturing processes.

Implementation Method 1

a heat exchanger coupled to said engine in a position such as to transfer heat from said exhaust line to said passage

Methodology Applied
Scientific EffectHeat transfer: Heat Exchanger

Data Source

PatentEP4073361B1Engine system provided with a split-cycle internal combustion engine
Publication Date: 2026.04.01 FPT IND SPA
  • EP4073361B1 patent drawingFigure 1
  • EP4073361B1 patent drawingFigure 2~4
  • EP4073361B1 patent drawingFigure 3

AI summary

An engine system is provided with a split-cycle internal combustion engine having an engine block and an expansion section, having a plurality of expansion cylinders and a rotating drive shaft, which is supported by a first portion of the engine block and is operated by the expansion cylinders; the engine further has a compression section having a volumetric compressor; the engine system is further provided with an exhaust line (4) to discharge exhaust gas from the expansion cylinders (16b), at least one passage (13, 14) to transfer compressed air from the volumetric compressor (12) to the expansion cylinders (16b), and a heat exchanger (55), which is coupled to the engine (2) in a position such as to transfer heat from the exhaust line (4) to such passage (13, 14).