In the pursuit to improve thermal and fuel efficiencies of internal combustion engines, various engine designs and configurations have been developed over recent years. Since the progress in this field keeps on increasing continuously, the geometrical aspects of combustion chamber and the engine configurations and their effects on the in-cylinder air/fuel mixing, turbulence and fuel combustion are becoming more relevant than ever. Due to this, there lies an impending need for a critical analysis of current in-cylinder flow analysis techniques available, their application on different engine types and the results acquired from the studies. Several new flow measurement technologies have emerged and for the past ten years, a critical analysis of airflow capturing methods within IC engines has not been done despite its great significance. This review presents a short yet a meaningful understanding to the analysis techniques for engine in-cylinder flows during the intake and compression of air and fuel, while bringing out significant findings from individual works, resulting in pointing out the strengths and accuracies of these techniques. In the reflection of reviewed studies, explicit analytical schemes and formulations bearing least errors compared to experimental results, are suggested.

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Magnetic Resonance Imaging is a widely used medical technique to capture physiological processes in a body through imaging. This phenomenon is also used by engineers to capture flow fields in an enclosed equipment. This is called magnetic resonance velocimetry (MRV). The popularity of this method is huge since this technique does not require an optical access to flowing fluid. Due to which, no seeding particle is introduced into the fluid. Chemiluminescence is another technique rarely used by the researchers to visualize the flow in which a chemical reaction in a flowing fluid emits light (luminescence). This emitted light is captured by high speed cameras and the snapshots are post-processed for flow dynamics study. The hydroxyl group (OH*) and methylidyne radical (CH*) are the most widely used emissions in chemiluminescence.

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Operating Conditions Optimization:The mention of varying operating conditions and parameters within the engine or environmental conditions suggests a holistic approach to achieving optimal engine performance.

In-Cylinder Flow Importance: Emphasizing the impact of in-cylinder flow characteristics on air-fuel mixing and combustion processes underscores the crucial role these factors play in the overall efficiency and environmental impact of spark-ignition engines.

Turbulent Structures and Combustion: Large-scale turbulent structures during intake and compression strokes are noted for their predictive role in flame propagation and thorough combustion, essential for smooth engine operation with minimal environmental and engine damage.

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Advanced Engine Designs: There is a potential market for new and improved internal combustion engine designs that take into account the insights gained from the analysis of combustion chamber geometries and engine configurations.

Flow Measurement Technologies: The emergence of new flow measurement technologies presents a market opportunity for companies specializing in innovative measurement tools for in-cylinder flows. This could include new sensors, imaging techniques, or other measurement devices.

Analytical Schemes and Formulations:Companies that can develop explicit analytical schemes and formulations with the least errors compared to experimental results may find a market for their methodologies. This could be of interest to engine manufacturers and researchers aiming for accurate in-cylinder flow analysis.

Fuel Efficiency Solutions: Given the focus on improving thermal and fuel efficiencies, there is a potential market for technologies or solutions that enhance combustion efficiency, air/fuel mixing, and overall engine performance.

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