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<p>This experimental study evaluates the influence of piston bowl geometry on combustion, performance, and emission characteristics in a thermal barrier coated (LHR) diesel engine fueled with a 20% Borassus flabellifer methyl ester (BFME20) blend. Three non-conventional piston bowl designs shallow combustion bowl (SCB), hemispherical combustion bowl (HCB), and toroidal combustion bowl (TCB) were fabricated and tested under full load conditions with the conventional combustion bowl (CCB) used as a baseline. The engine components (piston crown, cylinder head, and valve face) were coated with 0.5&#xa0;mm Partially Stabilized Zirconia (PSZ) using atmospheric plasma spray, enabling reduced thermal losses and enhanced in-cylinder temperatures. Results revealed that TCB geometry delivered the best overall performance, achieving a 9.9% increase in brake thermal efficiency (BTE) compared to BFME20 in CCB and a 5.3% increase relative to uncoated diesel operation. Similarly, BSFC was reduced by 9.2% in TCB compared to neat BFME operation. In terms of combustion characteristics, TCB showed the highest peak heat release rate (71.7&#xa0;J/°CA), a shorter ignition delay (9–10° CA), and a reduced combustion duration (34–36° CA), indicating faster and more complete combustion. Emission analysis confirmed that TCB resulted in a 15.8% increase in NOx due to higher combustion temperatures, while HC and CO emissions decreased by 10% and 14%, respectively, in comparison with the SCB and CCB designs. The study confirms that integrating TCB geometry with a PSZ-coated LHR engine fueled by BFME20 enhances combustion efficiency and performance while lowering partial emissions. However, the rise in NOx emissions indicates the need for effective control strategies to fully harness the potential of biodiesel in LHR engines. The work’s novelty lies in the combined experimental evaluation of piston bowl geometry, thermal barrier coating, and Borassus biodiesel, offering new insights for optimizing biodiesel-fueled engines toward higher efficiency and cleaner operation.</p>

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Effect of combustion chamber geometry on performance and emission behavior of a BFME20 fueled in low heat rejection engine

  • 期刊论文

  • 发表日期：

    2026年3月19日

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  • C. Sakthi Rajan,
  • K. Muralidharan,
  • B. Anbarasan

摘要

This experimental study evaluates the influence of piston bowl geometry on combustion, performance, and emission characteristics in a thermal barrier coated (LHR) diesel engine fueled with a 20% Borassus flabellifer methyl ester (BFME20) blend. Three non-conventional piston bowl designs shallow combustion bowl (SCB), hemispherical combustion bowl (HCB), and toroidal combustion bowl (TCB) were fabricated and tested under full load conditions with the conventional combustion bowl (CCB) used as a baseline. The engine components (piston crown, cylinder head, and valve face) were coated with 0.5 mm Partially Stabilized Zirconia (PSZ) using atmospheric plasma spray, enabling reduced thermal losses and enhanced in-cylinder temperatures. Results revealed that TCB geometry delivered the best overall performance, achieving a 9.9% increase in brake thermal efficiency (BTE) compared to BFME20 in CCB and a 5.3% increase relative to uncoated diesel operation. Similarly, BSFC was reduced by 9.2% in TCB compared to neat BFME operation. In terms of combustion characteristics, TCB showed the highest peak heat release rate (71.7 J/°CA), a shorter ignition delay (9–10° CA), and a reduced combustion duration (34–36° CA), indicating faster and more complete combustion. Emission analysis confirmed that TCB resulted in a 15.8% increase in NOx due to higher combustion temperatures, while HC and CO emissions decreased by 10% and 14%, respectively, in comparison with the SCB and CCB designs. The study confirms that integrating TCB geometry with a PSZ-coated LHR engine fueled by BFME20 enhances combustion efficiency and performance while lowering partial emissions. However, the rise in NOx emissions indicates the need for effective control strategies to fully harness the potential of biodiesel in LHR engines. The work’s novelty lies in the combined experimental evaluation of piston bowl geometry, thermal barrier coating, and Borassus biodiesel, offering new insights for optimizing biodiesel-fueled engines toward higher efficiency and cleaner operation.