Component-Level Exergy Insights for Heavy-Duty Diesel Engines: Understanding the Combined Effects of Injection Timing and EGR

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Improving diesel engine efficiency while reducing emissions remains one of the major challenges in modern thermal engineering. Although injection timing and exhaust gas recirculation (EGR) are widely applied to control combustion and emissions, their combined influence on the distribution of thermodynamic losses within individual engine components has received comparatively limited attention. This study presents a component-wise exergy analysis of a heavy-duty diesel engine using a calibrated Diesel-RK simulation framework. Rather than evaluating the engine as a single thermodynamic system, the research investigates how injection timing and EGR redistribute exergy losses among the piston, cylinder head, and cylinder liner. The findings provide valuable insights into combustion irreversibility, thermal loading, and exergy efficiency, offering engineers a more detailed thermodynamic basis for optimizing diesel engine calibration while balancing efficiency, durability, and emissions performance.

Bibliographic Information

Item Information
Article Title Component-wise exergy loss analysis under injection timing and EGR variations in a heavy-duty diesel engine
Author Eihab A. Raouf Mustafa
Affiliation Department of Mechanical Engineering, College of Engineering, Qassim University, Saudi Arabia
Journal Teknomekanik
Volume 9
Issue 2
Publication Year 2026
Pages 177–202
DOI https://doi.org/10.24036/teknomekanik.v9i2.54472
Publisher Universitas Negeri Padang
License Creative Commons Attribution 4.0 International (CC BY 4.0)
e-ISSN 2621-8720
p-ISSN 2621-9980
Keywords combustion irreversibility; diesel engine; exergy analysis; exhaust gas recirculation; injection timing

Research Background

  • Diesel engines remain indispensable for heavy-duty transportation and industrial applications. Their superior thermal efficiency and high torque output make them well suited for commercial vehicles and long-duration operation. However, maximizing efficiency while controlling emissions continues to require increasingly sophisticated combustion management strategies.

  • Injection timing and exhaust gas recirculation (EGR) are two of the most influential engine calibration parameters. Injection timing determines combustion phasing, ignition delay, and heat-release characteristics, whereas EGR modifies oxygen concentration and combustion temperature to reduce nitrogen oxide (NOx) emissions. Their interaction directly influences engine performance and thermodynamic efficiency.

  • Traditional energy analysis cannot fully explain engine efficiency losses. Conventional first-law analyses quantify energy flows but cannot distinguish between useful work potential and irreversible thermodynamic degradation. Exergy analysis overcomes this limitation by evaluating how much of the supplied fuel energy remains available for useful work.

  • Most previous exergy studies evaluate diesel engines as a single thermodynamic control volume. While overall exergy efficiency and total exergy destruction are commonly reported, relatively little attention has been given to how individual combustion chamber components contribute to thermodynamic losses.

  • Component-level thermal loading is particularly important in heavy-duty engines. The piston crown, cylinder head, and cylinder liner are continuously subjected to elevated temperatures and pressure gradients. Understanding how combustion control redistributes exergy losses among these components is essential for improving durability and thermal management.

  • A significant research gap exists regarding the combined influence of injection timing and EGR on localized exergy losses. Previous investigations rarely integrate combustion phasing, dilution effects, and component-wise exergy distribution across representative heavy-duty engine operating conditions.

  • This study addresses that gap through a detailed component-wise exergy assessment. By separating wall-related exergy losses into contributions from the piston, cylinder head, and cylinder liner, the research provides a more physically meaningful understanding of how combustion control strategies influence efficiency, irreversibility, and thermal loading simultaneously.

Research Objective

  • To investigate the combined effects of injection timing and exhaust gas recirculation on the distribution of exergy losses in a heavy-duty diesel engine.

  • To quantify component-wise wall heat exergy losses associated with the piston, cylinder head, and cylinder liner under various operating conditions.

  • To evaluate how injection timing and EGR influence exergy efficiency, brake exergy, exhaust exergy, wall heat exergy, and exergy destruction throughout the engine operating range.

  • To identify operating conditions that simultaneously maximize exergy efficiency while minimizing thermodynamic irreversibility.

  • To provide a thermodynamic foundation for optimizing diesel engine calibration by balancing combustion efficiency, thermal loading, and EGR operability.

Why This Research Matters

  • Provides deeper thermodynamic understanding. Component-wise exergy analysis reveals where useful work potential is lost inside the combustion chamber rather than reporting only overall engine efficiency.

  • Supports advanced diesel engine calibration. The findings demonstrate how injection timing and EGR jointly influence combustion irreversibility, enabling engineers to optimize calibration strategies using second-law thermodynamics.

  • Improves thermal management. Identifying the distribution of wall heat exergy among the piston, cylinder head, and liner provides valuable information for cooling system design and component durability.

  • Clarifies the thermodynamic consequences of EGR. The study shows that increasing EGR primarily increases combustion-related irreversibility rather than substantially increasing wall heat losses, offering new insight into dilution effects.

  • Supports cleaner heavy-duty engines. Understanding the balance between combustion efficiency and emissions control contributes to the development of diesel engines capable of meeting increasingly stringent environmental regulations.

  • Provides practical guidance for engine designers. The identified trade-off region between exergy efficiency and exergy destruction offers a useful engineering reference for selecting injection timing and EGR settings in commercial diesel applications.

  • Advances exergy-based engine research. By integrating component-level wall heat analysis with combustion phasing and dilution effects, the study extends conventional exergy analysis beyond whole-engine performance evaluation.

Research Limitations

  • The investigation is entirely simulation-based. The thermodynamic behavior of the engine was evaluated using a calibrated Diesel-RK numerical model rather than experimental engine testing. Although the model was calibrated and validated against representative heavy-duty diesel engine performance, the reported exergy distributions remain dependent on the assumptions and predictive capability of the simulation framework.
  • The combustion process was represented using a single-zone model. The adopted combustion model assumes spatially uniform thermodynamic properties within the combustion chamber and therefore cannot explicitly resolve localized temperature gradients, flame structure, or species distributions that may influence detailed exergy generation.
  • The analysis was limited to steady-state operating conditions. Dynamic engine behavior during transient acceleration, deceleration, load changes, cold starting, and other real-world operating conditions was not considered. Consequently, the reported exergy trends should be interpreted within the context of steady operating regimes.
  • Wall temperatures were simplified as cycle-averaged values. The component-wise wall heat exergy calculations employed representative mean temperatures for the piston, cylinder head, and cylinder liner. Temporal temperature fluctuations and localized thermal gradients were not explicitly modeled.
  • Radiative heat transfer was not independently evaluated. Wall heat transfer calculations focused on the thermal exchanges represented within the simulation model without separately quantifying radiation heat transfer inside the combustion chamber.
  • Mechanical friction losses were not decomposed. Although overall engine exergy balances considered useful work and thermodynamic losses, the study did not separately quantify friction-related exergy destruction arising from pistons, bearings, valve train components, or other mechanical subsystems.
  • The investigation focused on a single heavy-duty diesel engine configuration. The numerical study was based on one reference engine architecture. Different combustion chamber geometries, injection systems, turbocharging configurations, fuel properties, or engine sizes may exhibit different component-wise exergy distributions.
  • The operating matrix considered only selected injection timing and EGR variations. Other important calibration variables, including injection pressure, multiple injection strategies, boost pressure, variable valve timing, fuel composition, and alternative combustion concepts, were outside the scope of the present investigation.

Future Research Opportunities

  • Conduct experimental validation of the component-wise exergy framework using instrumented heavy-duty diesel engines to verify the simulation-based thermodynamic predictions under practical operating conditions.
  • Develop multi-zone or three-dimensional computational fluid dynamics (CFD) models capable of resolving localized combustion phenomena and spatial exergy generation throughout the combustion chamber.
  • Extend the exergy analysis to transient engine operation, including acceleration, deceleration, load transitions, and real-world driving cycles to better represent commercial vehicle applications.
  • Investigate the influence of alternative fuels such as biodiesel, renewable diesel, ammonia, hydrogen, methanol, or dual-fuel combustion systems on component-wise exergy distribution and thermodynamic irreversibility.
  • Examine advanced combustion strategies involving multiple injection events, variable injection pressure, low-temperature combustion, homogeneous charge compression ignition (HCCI), and reactivity-controlled compression ignition (RCCI) using the same exergy framework.
  • Integrate component-wise exergy analysis with artificial intelligence, machine learning, or optimization algorithms to identify optimal engine calibration strategies across large operating maps.
  • Investigate the relationship between localized exergy destruction, material degradation, thermo-mechanical fatigue, and engine durability to establish stronger links between thermodynamic efficiency and structural reliability.
  • Expand the methodology to hybrid powertrains and future low-carbon propulsion systems where second-law thermodynamic analysis can support integrated energy management and system optimization.

Potential for Public Policy Citation

This research provides evidence that can support public policies aimed at improving heavy-duty engine efficiency while reducing environmental impacts. By demonstrating how injection timing and exhaust gas recirculation influence thermodynamic efficiency and combustion irreversibility, the study contributes technical knowledge relevant to cleaner diesel engine development and sustainable transportation technologies.

Government agencies responsible for transportation, environmental protection, and industrial energy efficiency may find the results valuable when formulating regulations that encourage advanced combustion optimization rather than relying solely on end-of-pipe emission control technologies. The component-wise exergy approach also offers useful engineering evidence for developing standards related to engine thermal management, durability, and energy efficiency.

In academic and industrial research policy, the methodology may serve as a reference for promoting simulation-driven engine development, digital engineering practices, and second-law thermodynamic evaluation as complementary tools for designing next-generation internal combustion engines with improved efficiency and reduced emissions.

Who Should Read This Paper?

  • Researchers working in internal combustion engines, thermodynamics, energy conversion, combustion science, and exergy analysis.
  • Mechanical engineers involved in diesel engine design, combustion optimization, calibration, and thermal management.
  • Automotive engineers developing heavy-duty commercial vehicle powertrains and emission reduction technologies.
  • Engine calibration specialists responsible for optimizing injection timing, EGR strategies, fuel efficiency, and engine durability.
  • Graduate students studying advanced thermodynamics, combustion engineering, sustainable transportation, and mechanical engineering.
  • Researchers developing digital engine simulation, virtual calibration, and computational combustion models.
  • Industrial engineers seeking deeper understanding of localized thermodynamic losses for improving cooling system design and combustion chamber durability.
  • Policy makers and transportation agencies interested in technologies that improve fuel efficiency while supporting lower-emission heavy-duty transportation systems.

Final Thoughts

This study advances diesel engine thermodynamic analysis by moving beyond conventional whole-engine exergy evaluation toward a component-wise interpretation of combustion chamber losses. Through systematic numerical simulations covering multiple engine speeds, loads, injection timings, and EGR levels, the research demonstrates how combustion control strategies influence not only overall engine efficiency but also the spatial redistribution of thermodynamic losses among the piston, cylinder head, and cylinder liner.

One of the most important findings is that increasing EGR substantially increases combustion-related irreversibility while producing relatively modest changes in wall heat exergy. This distinction provides a clearer physical explanation of why excessive dilution reduces thermodynamic efficiency. Equally important, advancing injection timing redistributes thermal loading toward the piston and cylinder head, illustrating the balance that engine designers must achieve between improved combustion efficiency and component durability.

The study also identifies a practical operating region where favorable exergy efficiency can be achieved without excessive thermodynamic destruction, while highlighting that overly advanced injection timing may compromise the physical operation of the EGR system. This engineering trade-off reinforces the need for integrated engine calibration rather than optimization of individual parameters in isolation.

Overall, the research provides a meaningful contribution to diesel engine thermodynamics by combining combustion analysis, component-level wall heat evaluation, and second-law efficiency assessment within a unified analytical framework. The proposed methodology offers a valuable foundation for future investigations into advanced combustion strategies, alternative fuels, digital engine development, and sustainable heavy-duty propulsion systems.

Suggested Citations

Teknomekanik (UNP) Style

Mustafa, E. A. R. (2026). Component-wise exergy loss analysis under injection timing and EGR variations in a heavy-duty diesel engine. Teknomekanik, 9(2), 177–202. https://doi.org/10.24036/teknomekanik.v9i2.54472

APA (7th Edition)

Mustafa, E. A. R. (2026). Component-wise exergy loss analysis under injection timing and EGR variations in a heavy-duty diesel engine. Teknomekanik, 9(2), 177–202. https://doi.org/10.24036/teknomekanik.v9i2.54472

IEEE Style

E. A. R. Mustafa, "Component-wise exergy loss analysis under injection timing and EGR variations in a heavy-duty diesel engine," Teknomekanik, vol. 9, no. 2, pp. 177–202, 2026, doi:10.24036/teknomekanik.v9i2.54472.

Harvard Style

Mustafa, E.A.R., 2026. Component-wise exergy loss analysis under injection timing and EGR variations in a heavy-duty diesel engine. Teknomekanik, 9(2), pp.177–202. Available at: https://doi.org/10.24036/teknomekanik.v9i2.54472.

Vancouver Style

Mustafa EAR. Component-wise exergy loss analysis under injection timing and EGR variations in a heavy-duty diesel engine. Teknomekanik. 2026;9(2):177–202. doi:10.24036/teknomekanik.v9i2.54472.

Chicago (Author–Date)

Mustafa, Eihab A. Raouf. 2026. "Component-wise Exergy Loss Analysis under Injection Timing and EGR Variations in a Heavy-Duty Diesel Engine." Teknomekanik 9 (2): 177–202. https://doi.org/10.24036/teknomekanik.v9i2.54472.

MLA (9th Edition)

Mustafa, Eihab A. Raouf. "Component-wise Exergy Loss Analysis under Injection Timing and EGR Variations in a Heavy-Duty Diesel Engine." Teknomekanik, vol. 9, no. 2, 2026, pp. 177–202. Crossref, https://doi.org/10.24036/teknomekanik.v9i2.54472.

Editorial Note

This review is an independent scholarly interpretation prepared for Engineering Research Insights. The scientific discussion is derived exclusively from the published research article, while the bibliographic information has been verified against the official journal publication. The review summarizes the study's objectives, methodology, findings, contributions, and practical implications without modifying the original scientific conclusions. Readers are encouraged to consult the original article for complete experimental details, mathematical formulations, simulation parameters, figures, and appendices.

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