AN IMPACT OF COMBUSTION CHAMBER GEOMETRY ON CHARARACTERSTICS OF A DIESEL ENGINE FUELLED WITH GARCINIA GUMMI-GUTTA METHYL ESTER (GGGME)
Environmentally sustainable and renewable fuels present clear advantages over conventional petroleum-based fuels, offering improved energy utilization and helping to alleviate environmental and socioeconomic concerns. Their adoption in transport and power production supports cleaner energy transitio...
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Institute of Renewable Energy National Academy of Sciences of Ukraine
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Репозитарії
Vidnovluvana energetika| _version_ | 1871104120714166272 |
|---|---|
| author | Vinothkumar , A. Balu , P. Saravanan , C. Navaneetha , Krishnan P. Sokolovskyi , O. |
| author_facet | Vinothkumar , A. Balu , P. Saravanan , C. Navaneetha , Krishnan P. Sokolovskyi , O. |
| author_institution_txt_mv | [
{
"author": "A. Vinothkumar ",
"institution": "Bharath Institute of Higher Education and Research (BIST), Chennai, Tamil Nadu, India"
},
{
"author": "P. Balu ",
"institution": "Bharath Institute of Higher Education and Research (BIST), Chennai, Tamil Nadu, India"
},
{
"author": "C. Saravanan ",
"institution": "University College Engineering -BIT Campus, Anna University Trichy, India"
},
{
"author": "Krishnan P. Navaneetha ",
"institution": "University College Engineering -BIT Campus, Anna University Trichy, India"
},
{
"author": "O. Sokolovskyi ",
"institution": "Polissia National University, Zhytomyr, Ukraine"
}
] |
| author_sort | Vinothkumar , A. |
| baseUrl_str | https://ve.org.ua/index.php/journal/oai |
| collection | OJS |
| datestamp_date | 2026-07-18T06:32:24Z |
| description | Environmentally sustainable and renewable fuels present clear advantages over conventional petroleum-based fuels, offering improved energy utilization and helping to alleviate environmental and socioeconomic concerns. Their adoption in transport and power production supports cleaner energy transitions and assists in addressing emission-driven climate change challenges. In this investigation, combustion performance and emission characteristics were improved by redesigning the piston bowl geometry to intensify air–fuel interaction and in-cylinder turbulence. Three combustion chamber configurations were examined: a toroidal re-entrant combustion chamber (TRCC), a standard toroidal combustion chamber (TCC), and a shallow re-entrant combustion chamber (SRCC). The results obtained with diesel fuel were compared against those achieved using an optimized best fuel (BF) blend. The TRCC configuration exhibited the most favorable performance. It delivered a 4.85 % increase in brake thermal efficiency (BTE) and achieved significant emission reductions, including 41.6 % lower hydrocarbon (HC) emissions, 52.4 % reduction in carbon monoxide (CO), and 68.9% decrease in smoke opacity compared with diesel operation. These outcomes highlight the effectiveness of combustion chamber modification in enhancing engine efficiency while substantially reducing exhaust pollutants. |
| doi_str_mv | 10.36296/1819-8058.2026.1(84).300-310 |
| first_indexed | 2026-03-31T01:00:10Z |
| format | Article |
| fulltext |
300
Відновлювана енергетика. № 1/2026 | Біоенергетика
https://doi.org/10.36296/1819-8058.2026.1(84).300-310
AN IMPACT OF COMBUSTION CHAMBER GEOMETRY ON CHARARACTERSTICS
OF A DIESEL ENGINE FUELLED WITH GARCINIA GUMMI-GUTTA METHYL ESTER (GGGME)
Received Aug. 05, 2025; accepted Mar. 23, 2026
Available online Mar. 31, 2026
Vinothkumar A.1, Balu P.2, Saravanan C.3,
Navaneetha Krishnan P.4, Sokolovskyi O.5
Author for correspondence: Balu Pandian
e-mail: balumitauto@gmail.com
Abstract. Environmentally sustainable and renewable fuels
present clear advantages over conventional petroleum-
based fuels, offering improved energy utilization and helping
to alleviate environmental and socioeconomic concerns.
Their adoption in transport and power production supports
cleaner energy transitions and assists in addressing emission-
driven climate change challenges. In this investigation, com-
bustion performance and emission characteristics were im-
proved by redesigning the piston bowl geometry to intensify
air–fuel interaction and in-cylinder turbulence. Three com-
bustion chamber configurations were examined: a toroidal
re-entrant combustion chamber (TRCC), a standard toroidal
combustion chamber (TCC), and a shallow re-entrant com-
bustion chamber (SRCC). The results obtained with diesel fuel were compared against those achieved using an
optimized best fuel (BF) blend. The TRCC configuration exhibited the most favorable performance. It delivered a
4.85 % increase in brake thermal efficiency (BTE) and achieved significant emission reductions, including 41.6 %
lower hydrocarbon (HC) emissions, 52.4 % reduction in carbon monoxide (CO), and 68.9% decrease in smoke opac-
ity compared with diesel operation. These outcomes highlight the effectiveness of combustion chamber modifica-
tion in enhancing engine efficiency while substantially reducing exhaust pollutants.
Key words: combustion chamber, geometry, Garcinia Gummi-Gutta methyl ester (GGGME).
ВПЛИВ ГЕОМЕТРІЇ КАМЕРИ ЗГОРЯННЯ НА ХАРАКТЕРИСТИКИ ДИЗЕЛЬНОГО ДВИГУНА, ЩО
ПРАЦЮЄ НА МЕТИЛОВОМУ ЕТЕРІ ГАРЦИНІЇ КАМБОДЖІЙСЬКОЇ (GGGME)
Отримано 05 серп. 2025 р.; рекомендовано до публікації 23 бер. 2026 р.
Доступно онлайн 31 бер. 2026 р.
Віноткумар А.¹, Балу П.², Сараванан С.³,
Наваніта Крішнан⁴, Соколовський О.⁵
Автор для кореспонденції: Балу Пандіан
e-mail: balumitauto@gmail.com
Анотація. Екологічно сталі та відновлювані види па-
лива мають очевидні переваги порівняно з традицій-
ним викопним паливом, адже дозволяють підвищу-
вати ефективність використання енергії та сприя-
ють зменшенню екологічних і соціально-економічних
проблем. Їх використання у транспортній галузі й еле-
ктроенергетиці забезпечує підтримку в процесі пере-
ходу до чистіших енергетичних систем і допомагає ви-
рішувати проблеми зміни клімату, зумовлені викидами
парникових газів. У цій роботі продемонстровано під-
вищення показників згоряння та зниження обсягів
1 Research Scholar,
Department of Mechanical Engineering
https//orcid.org/0009-0001-5352-7856
2 Associate Professor,
Department of Automobile Engineering
https://orcid.org/0000-0003-3480-1116
3 Assistant Professor (Sr.Gr)
https//orcid.org/0000-0003-1298-4396
4 Assistant Professor (Sr.Gr)
https://orcid.org/0000-0002-7650-282x
5 PhD, Associate Professor, Department of
Electrification, Production Automation and
Engineering Ecology
https://orcid.org/0000-0001-8440-7462
1, 2 Bharath Institute of Higher Education and
Research (BIST), Chennai, Tamil Nadu, India
3,4 University College Engineering -BIT Campus,
Anna University Trichy, India
5 Polissia National University, Zhytomyr, Ukraine
1 аспірант кафедри машинобудування
https//orcid.org/0009-0001-5352-7856
2 доцент кафедри автомобільної інженерії
https://orcid.org/ 0000-0003-3480-1116
3 старший викладач (старша категорія)
https//orcid.org/0000-0003-1298-4396
4 старший викладач (старша категорія)
https://orcid.org/0000-0002-7650-282x
5 канд. техн. наук, доцент кафедри
електрифікації, автоматизації виробництва та
інженерної екології
https://orcid.org/0000-0001-8440-7462
1, 2 Інститут вищої освіти та досліджень
Бхарата (BIST), м. Ченнаї, штат Тамілнад, Індія
3, 4 нженерний коледж університету – кампус
BIT, Університет «Анна», м. Тричі, Індія
5 Поліський національний університет,
м. Житомир, Україна
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Відновлювана енергетика. № 1/2026 | Біоенергетика
викидів завдяки зміні геометрії чаші поршня камери згоряння дизельного двигуна з метою інтенсифіка-
ції взаємодії повітряно-паливної суміші та турбулентності в циліндрі. У ході дослідження було проана-
лізовано три конфігурації камери згоряння: тороїдальну камеру згоряння з рециркуляційним виступом
(TRCC), стандартну тороїдальну камеру згоряння (TCC) та неглибоку камеру згоряння з рециркуляцій-
ним виступом (SRCC). Результати, отримані під час роботи двигуна на дизельному паливі, порівнюва-
лися з результатами, досягнутими при використанні оптимізованої суміші палива (BF). Найкращі пока-
зники продемонструвала конфігурація TRCC. У цьому випадку, ефективний термічний ККД зріс на 4,85 %,
а також було досягнуто суттєвого зменшення викидів: обсяги викидів незгорілих вуглеводнів (HC) зме-
ншилися на 41,6 %, оксиду вуглецю (CO) — на 52,4 %, при цьому також на 68,9% зменшився показник
димності у порівнянні з подібним показником при роботі двигуна на дизельному паливі. Отримані ре-
зультати підтверджують ефективність модифікації камери згоряння, що дозволяє підвищити ефек-
тивність роботи двигуна та істотно зменшити обсяги викидів забруднюючих речовин з відпрацьова-
ними газами.
Ключові слова: камера згоряння, геометрія, метиловий етер олії гарцинії камбоджійської (Garcinia
gummi-gutta) (GGGME).
1. Introduction
Climate change and emission control remain pressing global
challenges. The continuous rise in fuel demand and the wide-
spread operation of internal combustion engines in transpor-
tation, agriculture, and industrial sectors have significantly
intensified atmospheric pollution. Prolonged dependence on
conventional diesel engines not only accelerates environ-
mental degradation but also poses severe health risks to liv-
ing organisms [1]. [2] performed experimental investigations
on a direct injection diesel engine running at 2000 rpm, sup-
ported by CFD simulations. A standard combustion chamber
(SCC) was compared with a modified combustion chamber
(MCC). The modified design enhanced spray distribution
within the piston bowl and improved evaporation character-
istics. Consequently, noticeable reductions in NOx and CO
emissions were achieved. When 7% hydrogen enrichment
was introduced, higher in-cylinder temperature and pressure
were observed. CO emissions decreased by 8.4%, while NOx
showed a 2.5% reduction in diesel mode and nearly 28% var-
iation with hydrogen supplementation. Enhanced flame
speed and higher heat release rate (HRR) were also recorded
with hydrogen blending. [3] optimized operating parameters
in a Homogeneous Charge Compression Ignition (HCCI) en-
gine. To prevent wall wetting, early split injections were
adopted. The compression ratio was lowered from 18.0:1 to
15.5:1, and the spray cone angle was reduced from 150° to
65° to minimize wall impingement. Earlier injection timing
improved brake thermal efficiency and advanced combus-
tion phasing. A higher peak cylinder pressure was observed,
while exhaust gas recirculation (EGR) helped reduce ignition
delay and moderate combustion temperature. These com-
bined modifications reduced NOx emissions and enhanced
combustion stability. [4] studied the influence of re-entrant
combustion chamber geometry on a diesel engine fueled
with Pongamia oil methyl ester (POME). A toroidal re-entrant
combustion chamber (TRCC) and a shallow depth re-entrant
combustion chamber (SDRCC) of identical volume were com-
pared with a baseline hemispherical combustion chamber
(HCC). Experiments were conducted using B20 and neat
POME. The TRCC with B20 demonstrated a 4.2% increase in
BTE and a 3.8% reduction in BSFC. Emissions of PM, UBHC,
and CO were reduced by approximately 22%, 18%, and 20%,
respectively, although NOx emissions increased by 9%.
Shorter ignition delay and higher peak pressure were ob-
served for the TRCC design.
In a subsequent study [5], ultra-low sulfur diesel (ULSD)
blended with 20% POME was evaluated under varied injec-
tion timings and combustion chamber geometries. The opti-
mized TRCC configuration achieved a 6.15% improvement in
BTE and a 5.2% decrease in BSFC compared to conventional
diesel operation. However, NOx emissions rose by about
13%, highlighting the efficiency–NOx trade-off. [6] experi-
mented with a ternary fuel blend enriched with Al₂O₃ nano-
particles, referred to as high-performance fuel (HPF), in a sin-
gle-cylinder diesel engine. TRCC geometry was tested with
injection timings of 20°, 21°, 22°, and 23° bTDC. The highest
BTE of 34.6% was obtained at 21° bTDC, compared to 32.9%
for diesel in HCC mode. Lower BSEC values were recorded for
HPF-TRCC21. HC and CO emissions decreased by 11.4% and
19.2%, respectively. Peak cylinder pressure reached 78.6 bar,
with a maximum HRR of 88.7 J/deg CA. [7] further assessed
TCC, TRCC, and SDRCC geometries using B20 POME without
altering compression ratio. The toroidal combustion cham-
ber (TCC) exhibited a 3.5% higher BTE than other geometries
and reduced HC and CO emissions by nearly 17% and 15%,
respectively. However, NOx emissions increased by 8%. Im-
proved combustion characteristics were consistently ob-
served under full-load conditions. [8] investigated spray
structure, fuel motion, and emission behavior through com-
bined experimental and numerical analysis. By modifying in-
jection pressure and spray angle in re-entrant piston bowls,
enhanced swirl and turbulence were achieved. Multi-swirl
piston bowl (MSPB) and double-swirl bowl (DSB) configura-
tions resulted in nearly 76% reduction in HC, CO, and soot
emissions collectively. However, NOx increased by around
12% due to elevated combustion temperatures. [9] exam-
ined Calophyllum inophyllum methyl ester (CIME) in a diesel
engine and identified B20 as the optimum blend under hem-
ispherical combustion chamber conditions. A modified hem-
ispherical combustion chamber (MHCC) was later introduced
and analyzed using ANSYS Fluent simulations. The MHCC
configuration improved BTE by 3.9% and reduced emissions
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Відновлювана енергетика. № 1/2026 | Біоенергетика
compared with the conventional HCC. [10] developed a CFD
model and validated it experimentally in a common rail di-
rect injection (CRDI) engine. Various in-cylinder modification
strategies, including optimized injection timing, multiple in-
jection schemes, combustion chamber redesign, and EGR,
were tested individually and in combination. The optimized
combination reduced NOx by 21% and soot by 18%, while
improving overall efficiency. [11] tested a ternary diesel–bi-
odiesel–ethanol blend doped with Al₂O₃ nanoparticles (HPF)
in TRCC, SDRCC, and TCC geometries. The TRCC configuration
achieved a 13.2% increase in BTE and an 8.9% improvement
in fuel economy compared with diesel baseline operation.
CO emissions decreased by 35.8%, HC by 22–38%, and
smoke by 16.5%. Increased HRR and peak pressure were at-
tributed to superior atomization and enhanced air–fuel mix-
ing within the re-entrant chamber. The present study aims to
further enhance combustion performance using an opti-
mized Best Fuel (BF) diesel blend combined with a toroidal
re-entrant piston bowl geometry. Key combustion parame-
ters, including in-cylinder pressure variation with crank an-
gle, maximum rate of pressure rise, ignition delay, and emis-
sion characteristics, are evaluated and compared against die-
sel operation in a conventional hemispherical combustion
chamber. This comparative assessment provides deeper
insight into the impact of combustion chamber optimization
on engine performance and emission reduction.
2. Materials and Methods
2. 1 Garcinia Gummi-Gutta Biodiesel Oil Preparation
The biodiesel derived from Garcinia gummi-gutta is obtained
from the oil extracted from the seeds of Garcinia gummi-
gutta (Malabar tamarind). Ripe fruits are harvested, and the
seeds are separated, washed, and dried in the sun to evapo-
rate the moisture. The dried seeds are crushed, and the oil is
extracted either by expeller or solvent extraction using n-
hexane. The extracted oil is filtered and heated to evaporate
the remaining moisture. The raw oil has high viscosity;
hence, it is converted to biodiesel through a transesterifica-
tion reaction. In this reaction, the raw oil is heated to 55–
60°C and mixed with methanol in the presence of a catalyst
such as sodium hydroxide (NaOH) or potassium hydroxide
(KOH). The mixture is stirred for 60–90 minutes and left to
settle, separating into two distinct layers: biodiesel (top
layer) and glycerol (bottom layer). The biodiesel is separated,
washed with warm distilled water to remove contaminants,
and dried to produce clear FAME, which can be used in diesel
engines or blended with conventional diesel fuel.
Table 1. Physical Properties of Garcinia gummi-gutta Biodiesel
Property Diesel
Garcinia
Biodiesel (Typical)
Effect on Engine
Density (kg/m³) 820–840 870–890 Higher density increases injected fuel mass
Kinematic Viscosity (mm²/s at 40°C) 2–4 4.5–5.8 Higher viscosity affects atomization
Calorific Value (MJ/kg) 42–45 36–39 Slightly lower → higher fuel consumption
Flash Point (°C) 50–70 150–170 Safer storage and handling
Cetane Number 45–50 50–55 Better ignition quality
Cloud Point (°C) −5 to 5 8–15 Poor cold flow properties
Pour Point (°C) −15 to 0 5–10 May cause cold-start issues
2.2 Combustion Chamber Modification
The piston crown is designed with a bowl-shaped cavity to
promote efficient air–fuel blending, intensify in-cylinder
swirl and turbulence, and thereby achieve more complete
combustion. The configuration of this cavity plays a decisive
role in governing spray behavior, flame development, and
overall engine performance. For this investigation, four dis-
tinct combustion chamber geometries were analyzed: the
conventional hemispherical combustion chamber (HCC), the
toroidal re-entrant combustion chamber (TRCC), the toroidal
combustion chamber (TCC), and the shallow depth re-en-
trant combustion chamber (SDRCC). These designs were se-
lected to evaluate their influence on combustion efficiency
and emission characteristics. A visual comparison of the dif-
ferent piston bowl configurations is presented in Fig. 1.
3. Experimental setup
The experimental investigation was carried out using a
single-cylinder, four-stroke, air-cooled, direct injection
stationary research engine. The engine was integrated
with a range of measuring instruments to evaluate fuel
performance, combustion behavior, and emission charac-
teristics. Engine tests were performed under variable
loading conditions using an electrical eddy current dyna-
mometer. The load was applied from no-load (0%) to full-
load (100%) in steps of 25% to ensure systematic perfor-
mance evaluation. To measure in-cylinder pressure and to
determine the heat release rate, a pressure transducer
was mounted on the cylinder head in conjunction with a
MICO fuel injector assembly. Exhaust emissions, including
hydrocarbons (HC), carbon monoxide (CO), and oxides of
nitrogen (NOx), were quantified using a QRO-402 exhaust
gas analyzer. Smoke opacity was measured with an AVL
437C smoke meter.
The complete arrangement of the experimental setup is il-
lustrated in Fig. 2. SAE 100 grade lubricating oil was used to
minimize friction and wear between the engine’s moving
components during operation.
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Відновлювана енергетика. № 1/2026 | Біоенергетика
Fig. 1. Modified combustion chambers
Fig. 2. Layout of experimental setup
4. Results and Discussion
The experimental study was carried out using redesigned
piston bowl configurations, and the corresponding findings
are presented in the following sections. In addition to the
standard hemispherical combustion chamber, three alter-
native geometries were evaluated: the shallow depth re-
entrant combustion chamber (SDRCC), the toroidal re-
entrant combustion chamber (TRCC), and the toroidal com-
bustion chamber (TCC). To ensure a fair comparison, the
compression ratio was maintained identical for all combus-
tion chamber designs. The photographic and schematic
representations of these piston bowl configurations are
provided in Fig. 1. The modified geometries enhance in-cyl-
inder air motion and promote the recirculation of fuel-rich
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Відновлювана енергетика. № 1/2026 | Біоенергетика
mixtures toward the active flame region, thereby support-
ing more efficient combustion. The Best Fuel (BF) blend was
tested in each of these combustion chambers, and the re-
sulting performance, combustion, and emission character-
istics were comparatively analyzed.
4.1 PERFORMANCE CHARACTERISTICS
The variation of brake thermal efficiency (BTE) with engine
load for biodiesel fuel (BF) under different combustion
chamber configurations is illustrated in Fig. 3. It is evident
that combustion chamber geometry significantly influences
engine performance characteristics. In addition to the
standard hemispherical combustion chamber (HCC), three
modified chamber designs demonstrated superior effi-
ciency. The maximum BTE values recorded were 31.3% for
the Shallow Depth Re-entrant Combustion Chamber
(SDRCC), 31.5% for the Toroidal Combustion Chamber
(TCC), and 31.6% for the Truncated Re-entrant Combustion
Chamber (TRCC). The enhanced efficiency observed in the
modified chambers can be attributed to improved in-cylin-
der air motion. The re-entrant configurations intensified
squish flow and generated stronger swirl motion, thereby
increasing turbulence intensity and promoting rapid mixing
between air and fuel droplets. This improved atomization
and vaporization process resulted in more complete com-
bustion and higher thermal efficiency. Among the tested
geometries, TRCC delivered the highest BTE, followed by
TCC and SDRCC. The superior performance of TRCC is pri-
marily associated with its optimized re-entrant profile,
which facilitates greater swirl strength and improved air–
fuel interaction. These findings are consistent with previ-
ously reported studies that highlighted the positive impact
of re-entrant combustion chamber designs on engine effi-
ciency [12].
Fig. 3. BTE vs engine load
Brake specific fuel consumption (BSFC) exhibited a trend
opposite to that of brake thermal efficiency, confirming
their inverse relationship. The variation of BSFC for bio-
diesel fuel (BF) under different combustion chamber
configurations is presented in Fig. 4. Among the tested
geometries, the lowest fuel consumption at full load was
observed with the Truncated Re-entrant Combustion
Chamber (TRCC), followed by the Toroidal Combustion
Chamber (TCC) and the Shallow Depth Re-entrant Com-
bustion Chamber (SDRCC). The reduction in BSFC for the
modified chambers can be attributed to enhanced in-cyl-
inder air motion and improved charge circulation char-
acteristics. The re-entrant design promotes effective
recirculation of the air–fuel mixture toward the central
combustion region, intensifying turbulence and facilitat-
ing superior mixing. This enhanced atomization and
combustion efficiency lead to more complete energy
conversion, thereby lowering the quantity of fuel re-
quired to produce the same power output. Based on fuel
economy considerations, TRCC demonstrates the most
favorable performance among the investigated configu-
rations. The observed pattern aligns with findings re-
ported in earlier experimental investigations, which
highlighted the positive influence of re-entrant combus-
tion chamber geometries on fuel consumption charac-
teristics [13].
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Відновлювана енергетика. № 1/2026 | Біоенергетика
Fig. 4. BSFC vs engine load
Fig. 5. Pressure vs crank angle
4.2 COMBUSTION CHARACTERISTICS
Fig. 5 illustrates the in-cylinder pressure characteristics of
the test fuel under different combustion chamber geome-
tries across varying engine loads. Among the configurations
evaluated, the Truncated Toroidal Re-entrant Combustion
Chamber (TRCC) recorded the highest peak pressure,
reaching 78.2 bar. The modified chamber designs consist-
ently produced higher maximum cylinder pressures com-
pared with the baseline combustion chamber operating
with biodiesel fuel. The improved pressure development in
the modified geometries can be attributed to enhanced in-
306
Відновлювана енергетика. № 1/2026 | Біоенергетика
cylinder air motion and superior charge preparation. The
re-entrant designs intensified swirl and tumble flows, pro-
moting rapid fuel evaporation and improved spray disper-
sion. This strengthened turbulence level facilitated efficient
atomization and more homogeneous air–fuel mixing, lead-
ing to a faster and more complete combustion process,
thereby increasing peak pressure. In contrast, the compar-
atively lower peak pressure observed in the Toroidal
Combustion Chamber (TCC) and Hemispherical Combus-
tion Chamber (HCC) can be linked to weaker squish inten-
sity within the piston bowl. Reduced squish limits turbu-
lence generation near top dead center, resulting in compar-
atively slower combustion and lower maximum pressure
rise. The overall trend observed in this study corresponds
with previously reported experimental findings in the liter-
ature [14].
Fig. 6. HRR vs crank angle
Fig. 6 presents the heat release rate (HRR) characteristics
of biodiesel fuel (BF) under different combustion chamber
configurations at varying engine loads. Among the tested
geometries, the Truncated Re-entrant Combustion Cham-
ber (TRCC) exhibited the highest peak HRR of 80.25 J/°CA,
followed by the Toroidal Combustion Chamber (TCC) with
79.3 J/°CA and the Shallow Depth Re-entrant Combustion
Chamber (SDRCC) with 77.13 J/°CA. The elevated HRR ob-
served in the modified combustion chambers is primarily
attributed to intensified in-cylinder air motion. The re-en-
trant piston profiles enhanced swirl intensity along the di-
rection of airflow, promoting rapid mixing between fuel
droplets and air. This improved turbulence shortened the
ignition delay period and accelerated the premixed com-
bustion phase, resulting in a sharper and higher peak heat
release. Furthermore, the favorable physicochemical prop-
erties of the biodiesel fuel, including optimized viscosity,
higher cetane number, suitable density, and appreciable
calorific value, contributed to efficient combustion behav-
ior. These properties supported improved spray atomiza-
tion, vaporization, and flame propagation, thereby increas-
ing the rate of energy liberation during combustion. Conse-
quently, the BF–TRCC configuration demonstrated superior
HRR performance compared with the other chamber de-
signs. The trend observed in this investigation aligns with
earlier experimental findings reported in the literature.
4.3 EMISSION CHARACTERISTICS
Fig. 7 illustrates the hydrocarbon (HC) emission characteris-
tics of biodiesel fuel (BF) when operated with different com-
bustion chamber geometries, namely SDRCC, TRCC, TCC, and
the conventional Hemispherical Combustion Chamber
(HCC). The baseline HCC configuration exhibited compara-
tively higher unburned hydrocarbon emissions than the
modified piston bowl designs. In contrast, all re-engineered
combustion chambers demonstrated a noticeable reduction
in HC levels across the operating range. Among the tested
configurations, SDRCC, TCC, and TRCC produced lower hy-
drocarbon emissions not only compared to the conventional
diesel operation but also relative to the B20 blend. The re-
duction in HC emissions can be attributed to two primary fac-
tors. First, the inherent oxygenated nature of the biodiesel
fuel promotes more complete oxidation of hydrocarbons
during combustion. Second, the re-entrant piston geome-
tries, particularly in the TRCC design, intensified swirl and
turbulence inside the cylinder. This enhanced air–fuel inter-
action improved atomization, vaporization, and mixture ho-
mogeneity, thereby minimizing the presence of unburned
fuel fragments in the exhaust. The TRCC configuration, owing
to its stronger swirl generation and improved in-cylinder
charge motion, exhibited the lowest HC emission among the
tested chamber designs. The overall emission behavior ob-
served in this study is consistent with trends reported in ear-
lier experimental investigations.
307
Відновлювана енергетика. № 1/2026 | Біоенергетика
Fig. 7. HC vs engine load
Fig. 8. Carbon monoxide vs engine load
Fig. 8 presents the carbon monoxide (CO) emission charac-
teristics of biodiesel fuel (BF) under various combustion
chamber configurations. The modified piston bowl geome-
tries demonstrated noticeably lower CO emissions com-
pared with the conventional chamber design. Among them,
the Truncated Re-entrant Combustion Chamber (TRCC) rec-
orded the minimum CO levels across the tested operating
conditions. The reduction in CO emissions can be attributed
to improved in-cylinder oxidation processes. Enhanced air–
fuel mixing within the re-entrant chamber promoted more
effective conversion of intermediate CO into carbon diox-
ide (CO₂), thereby limiting incomplete combustion prod-
ucts. In comparison with diesel operation, the SDRCC, TCC,
and TRCC configurations operating with biodiesel showed a
substantial decline in CO output. This improvement is pri-
marily due to two factors: the inherent oxygen content pre-
sent in biodiesel fuel and the intensified swirl and squish
effects generated by the modified chamber geometries.
308
Відновлювана енергетика. № 1/2026 | Біоенергетика
The re-entrant profile strengthened turbulent air motion
near top dead center, shortened combustion duration, and
facilitated more complete fuel oxidation. Consequently, in-
complete combustion losses were minimized. The emission
behavior observed in this study is consistent with trends
previously reported in experimental investigations by other
researchers.
Fig. 9. Oxides of Nitrogen vs engine load
Fig. 9 illustrates the variation of nitrogen oxides (NOx)
emissions for biodiesel fuel (BF) under different combus-
tion chamber geometries across varying engine loads. The
modified chamber configurations generally produced
higher NOx levels compared to the baseline design, with
the TRCC configuration exhibiting the maximum NOx emis-
sion among the tested geometries. The SDRCC also showed
relatively elevated NOx values, while the TCC demon-
strated comparatively lower NOx formation than the other
modified chambers. The increased NOx observed in the
TRCC configuration can be attributed to intensified swirl
motion and higher turbulence levels within the cylinder.
These enhanced in-cylinder flow characteristics promote
rapid combustion and elevated peak temperatures, which
favor thermal NOx formation. In contrast, the relatively
weaker swirl intensity in the TCC geometry limits peak com-
bustion temperatures and reduces the availability of high-
temperature zones, thereby resulting in comparatively
lower NOx emissions. Furthermore, the physicochemical
properties of biodiesel fuel including its inherent oxygen
content, higher cetane number, and lower viscosity con-
tribute to improved combustion efficiency and elevated in-
cylinder temperatures. While these properties enhance ox-
idation and overall combustion quality, they also create
conditions conducive to increased NOx formation. The
emission trends identified in this investigation are con-
sistent with previously published experimental findings re-
ported in the literature.
Fig. 10 presents the variation of smoke opacity with in-
creasing engine load for the different combustion chamber
configurations. The modified piston bowl geometries ex-
hibited noticeably lower smoke emissions compared with
conventional diesel operation. Among them, the TRCC con-
figuration showed the most significant reduction, followed
by TCC and SDRCC. The decline in smoke formation can be
attributed to improved in-cylinder charge motion and en-
hanced combustion efficiency. The re-entrant chamber
profiles intensified swirl and turbulence, promoting finer
fuel atomization and more uniform air–fuel distribution.
This improved mixture preparation minimized locally rich
zones within the combustion chamber, thereby suppress-
ing soot formation. The TRCC design, owing to its stronger
swirl intensity and efficient combustion characteristics,
achieved the lowest smoke opacity among the tested ge-
ometries. The emission behavior observed in this study is
consistent with findings reported in earlier experimental in-
vestigations, which highlighted the effectiveness of opti-
mized combustion chamber designs in reducing particulate
and smoke emissions.
309
Відновлювана енергетика. № 1/2026 | Біоенергетика
Fig. 10. Smoke vs engine load
Conclusions
Experimental investigations were carried out using three
modified combustion chamber (CC) geometries: SDRCC,
TCC, and TRCC, and their performance was evaluated while
operating with biodiesel fuel (BF). All modified chamber de-
signs demonstrated improved results compared with the
conventional hemispherical combustion chamber.
• Among the tested configurations, the TRCC geometry
delivered the most favorable performance characteris-
tics. A noticeable improvement in brake thermal effi-
ciency (BTE) was accompanied by a corresponding re-
duction in brake specific fuel consumption (BSFC). The
enhanced performance can be primarily attributed to
intensified in-cylinder swirl motion, which promoted su-
perior air–fuel interaction and more efficient combus-
tion.
• In terms of emission characteristics, the TRCC configu-
ration also showed improved exhaust behavior when
fueled with BF. A significant reduction in hydrocarbon
emissions was observed compared with diesel opera-
tion. This improvement is associated with improved
spray development, minimized wall wetting, and re-
duced fuel impingement on the combustion chamber
surfaces, all of which contribute to more complete com-
bustion.
• Based on the overall assessment of performance and
emission parameters, the suitability of the combustion
chamber geometries for biodiesel operation can be
ranked in descending order as:
TRCC > TCC > SDRCC > HCC
This ranking confirms the effectiveness of re-entrant piston
bowl modifications in enhancing biodiesel combustion
characteristics.
Availability of data and materials
No datasets were generated, collected, or subjected to in-
dependent analysis as part of this study. Therefore, data
sharing provisions are not applicable to the present work.
Funding
The author(s) received no financial support for the re-
search.
Conflict of Interest
The authors certify that there is no conflict of interest.
Authors' contributions
Vinothkumar A. – Investigation, Balu P. – Supervision,
Saravanan C., Sokolovskyi O. – Conceptualization,
Navaneetha Krishnan P. – Visualization.
Acknowledgements
We thank the Bharath Institute of Higher Education and Re-
search Management and Pro VC (Academic and Publica-
tions) for their support in completing this research work.
310
Відновлювана енергетика. № 1/2026 | Біоенергетика
REFERENCE
1. Benajes, J., Pastor, J.V., García, A. and Monsalve-Ser-
rano, J., 2015. An experimental investigation on the in-
fluence of piston bowl geometry on RCCI performance
and emissions in a heavy-duty engine. Energy Conver-
sion and Management, 103, pp.1019-1030.
2. Mamilla, V.R., Mallikarjun, M.V. and Rao, G.L.N., 2013.
Effect of combustion chamber design on a DI diesel en-
gine fuelled with jatropha methyl esters blends with
diesel. Procedia Engineering,
3. Jaichandar, S. and Annamalai, K., 2012. Effects of open
combustion chamber geometries on the performance
of pongamia biodiesel in a DI diesel engine. Fuel, 98,
pp.272-279.
4. Venkateswaran, S.P. and Nagarajan, G., 2010. Effects
of the re-entrant bowl geometry on a DI turbocharged
diesel engine performance and emissions—a CFD ap-
proach. Journal of engineering for gas turbines and
power, 132(12).
5. Lalvani, J.I.J., Parthasarathy, M., Dhinesh, B. and Anna-
malai, K., 2016. Pooled effect of injection pressure and
turbulence inducer piston on performance, combus-
tion, and emission characteristics of a DI diesel engine
powered with biodiesel blend. Ecotoxicology and envi-
ronmental safety, 134, pp.336-343.
6. Jaichandar, S. and Annamalai, K., 2012a. Influences of
re-entrant combustion chamber geometry on the per-
formance of Pongamia biodiesel in a DI diesel en-
gine. Energy, 44(1), pp.633-640.
7. Jaichandar, S. and Annamalai, K., 2013. Combined im-
pact of injection pressure and combustion chamber ge-
ometry on the performance of a biodiesel fueled diesel
engine. Energy, 55, pp.330-339.
8. Dolak, J.G., Shi, Y. and Reitz, R.D., 2010. A computa-
tional investigation of stepped-bowl piston geometry
for a light duty engine operating at low load (No. 2010-
01-1263). SAE Technical Paper.
9. K. Rangasamya, N. Panchacharam. An impact of differ-
ent injection timing operating on chlorellea emersonii
methyl ester (CEME) with best fuel (BF). Journal of Op-
toelectronic and Biomedical Materials Vol. 14, No. 4,
October-December 2022, p. 191-201
10. Appavu, P. and Venu, H., 2019. Quaternary blends of
diesel/biodiesel/vegetable oil/pentanol as a potential
alternative feedstock for existing unmodified diesel en-
gine: Performance, combustion and emission charac-
teristics. Energy, 186, p.115856.
11. Wei, S., Wang, F., Leng, X., Liu, X. and Ji, K., 2013. Nu-
merical analysis on the effect of swirl ratios on swirl
chamber combustion system of DI diesel engines. En-
ergy Conversion and Management, 75, pp.184-190.
12. Bapu, B.R., Saravanakumar, L. and Prasad, B.D., 2017.
Effects of combustion chamber geometry on combus-
tion characteristics of a DI diesel engine fueled with
calophyllum inophyllum methyl ester. Journal of the
Energy institute, 90(1), pp.82-100.
13. Shi, Y. and Reitz, R.D., 2008. Optimization study of the
effects of bowl geometry, spray targeting, and swirl ra-
tio for a heavy-duty diesel engine operated at low and
high load. International Journal of Engine Re-
search, 9(4), pp.325-346.
14. Rangasamy K, Panchacharam N, Pandian B. An experi-
mental evaluation of Chlorella emersonii biodiesel for
compression ignition engines. Journal of Thermal Engi-
neering 2024;10(4):978-985. doi: 10.14744/ther-
mal.0000843.
|
| id | veorgua-article-613 |
| institution | Vidnovluvana energetika |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2026-07-19T01:19:03Z |
| publishDate | 2026 |
| publisher | Institute of Renewable Energy National Academy of Sciences of Ukraine |
| record_format | ojs |
| resource_txt_mv | veorgua/0f/fe29f5b6465a2bc45764a72d4319c30f.pdf |
| spelling | veorgua-article-6132026-07-18T06:32:24Z AN IMPACT OF COMBUSTION CHAMBER GEOMETRY ON CHARARACTERSTICS OF A DIESEL ENGINE FUELLED WITH GARCINIA GUMMI-GUTTA METHYL ESTER (GGGME) ВПЛИВ ГЕОМЕТРІЇ КАМЕРИ ЗГОРЯННЯ НА ХАРАКТЕРИСТИКИ ДИЗЕЛЬНОГО ДВИГУНА, ЩО ПРАЦЮЄ НА МЕТИЛОВОМУ ЕТЕРІ ГАРЦИНІЇ КАМБОДЖІЙСЬКОЇ (GGGME) Vinothkumar , A. Balu , P. Saravanan , C. Navaneetha , Krishnan P. Sokolovskyi , O. combustion chamber, geometry, Garcinia Gummi-Gutta methyl ester (GGGME). камера згоряння, геометрія, метиловий етер олії гарцинії камбоджійської (Garcinia gummi-gutta) (GGGME). Environmentally sustainable and renewable fuels present clear advantages over conventional petroleum-based fuels, offering improved energy utilization and helping to alleviate environmental and socioeconomic concerns. Their adoption in transport and power production supports cleaner energy transitions and assists in addressing emission-driven climate change challenges. In this investigation, combustion performance and emission characteristics were improved by redesigning the piston bowl geometry to intensify air–fuel interaction and in-cylinder turbulence. Three combustion chamber configurations were examined: a toroidal re-entrant combustion chamber (TRCC), a standard toroidal combustion chamber (TCC), and a shallow re-entrant combustion chamber (SRCC). The results obtained with diesel fuel were compared against those achieved using an optimized best fuel (BF) blend. The TRCC configuration exhibited the most favorable performance. It delivered a 4.85 % increase in brake thermal efficiency (BTE) and achieved significant emission reductions, including 41.6 % lower hydrocarbon (HC) emissions, 52.4 % reduction in carbon monoxide (CO), and 68.9% decrease in smoke opacity compared with diesel operation. These outcomes highlight the effectiveness of combustion chamber modification in enhancing engine efficiency while substantially reducing exhaust pollutants. Екологічно сталі та відновлювані види палива мають очевидні переваги порівняно з традиційним викопним паливом, адже дозволяють підвищувати ефективність використання енергії та сприяють зменшенню екологічних і соціально-економічних проблем. Їх використання у транспортній галузі й електроенергетиці забезпечує підтримку в процесі переходу до чистіших енергетичних систем і допомагає вирішувати проблеми зміни клімату, зумовлені викидами парникових газів. У цій роботі продемонстровано підвищення показників згоряння та зниження обсягів викидів завдяки зміні геометрії чаші поршня камери згоряння дизельного двигуна з метою інтенсифікації взаємодії повітряно-паливної суміші та турбулентності в циліндрі. У ході дослідження було проаналізовано три конфігурації камери згоряння: тороїдальну камеру згоряння з рециркуляційним виступом (TRCC), стандартну тороїдальну камеру згоряння (TCC) та неглибоку камеру згоряння з рециркуляційним виступом (SRCC). Результати, отримані під час роботи двигуна на дизельному паливі, порівнювалися з результатами, досягнутими при використанні оптимізованої суміші палива (BF). Найкращі показники продемонструвала конфігурація TRCC. У цьому випадку, ефективний термічний ККД зріс на 4,85 %, а також було досягнуто суттєвого зменшення викидів: обсяги викидів незгорілих вуглеводнів (HC) зменшилися на 41,6 %, оксиду вуглецю (CO) — на 52,4 %, при цьому також на 68,9% зменшився показник димності у порівнянні з подібним показником при роботі двигуна на дизельному паливі. Отримані результати підтверджують ефективність модифікації камери згоряння, що дозволяє підвищити ефективність роботи двигуна та істотно зменшити обсяги викидів забруднюючих речовин з відпрацьованими газами. Institute of Renewable Energy National Academy of Sciences of Ukraine 2026-03-29 Article Article application/pdf https://ve.org.ua/index.php/journal/article/view/613 10.36296/1819-8058.2026.1(84).300-310 Vidnovluvana energetika ; No. 1(84) (2026): Scientific and applied Journal renewable energy ; 300-310 Возобновляемая энергетика; ##issue.no## 1(84) (2026): Scientific and applied Journal renewable energy ; 300-310 Відновлювана енергетика; № 1(84) (2026): Науково-прикладний журнал Відновлювана енергетика; 300-310 2664-8172 1819-8058 10.36296/1819-8058.2026.1(84) en https://ve.org.ua/index.php/journal/article/view/613/524 Copyright (c) 2026 A. Vinothkumar , P. Balu , C. Saravanan , Krishnan P. Navaneetha , O. Sokolovskyi https://creativecommons.org/licenses/by-nc-nd/4.0 |
| spellingShingle | combustion chamber geometry Garcinia Gummi-Gutta methyl ester (GGGME). Vinothkumar , A. Balu , P. Saravanan , C. Navaneetha , Krishnan P. Sokolovskyi , O. AN IMPACT OF COMBUSTION CHAMBER GEOMETRY ON CHARARACTERSTICS OF A DIESEL ENGINE FUELLED WITH GARCINIA GUMMI-GUTTA METHYL ESTER (GGGME) |
| title | AN IMPACT OF COMBUSTION CHAMBER GEOMETRY ON CHARARACTERSTICS OF A DIESEL ENGINE FUELLED WITH GARCINIA GUMMI-GUTTA METHYL ESTER (GGGME) |
| title_alt | ВПЛИВ ГЕОМЕТРІЇ КАМЕРИ ЗГОРЯННЯ НА ХАРАКТЕРИСТИКИ ДИЗЕЛЬНОГО ДВИГУНА, ЩО ПРАЦЮЄ НА МЕТИЛОВОМУ ЕТЕРІ ГАРЦИНІЇ КАМБОДЖІЙСЬКОЇ (GGGME) |
| title_full | AN IMPACT OF COMBUSTION CHAMBER GEOMETRY ON CHARARACTERSTICS OF A DIESEL ENGINE FUELLED WITH GARCINIA GUMMI-GUTTA METHYL ESTER (GGGME) |
| title_fullStr | AN IMPACT OF COMBUSTION CHAMBER GEOMETRY ON CHARARACTERSTICS OF A DIESEL ENGINE FUELLED WITH GARCINIA GUMMI-GUTTA METHYL ESTER (GGGME) |
| title_full_unstemmed | AN IMPACT OF COMBUSTION CHAMBER GEOMETRY ON CHARARACTERSTICS OF A DIESEL ENGINE FUELLED WITH GARCINIA GUMMI-GUTTA METHYL ESTER (GGGME) |
| title_short | AN IMPACT OF COMBUSTION CHAMBER GEOMETRY ON CHARARACTERSTICS OF A DIESEL ENGINE FUELLED WITH GARCINIA GUMMI-GUTTA METHYL ESTER (GGGME) |
| title_sort | impact of combustion chamber geometry on chararacterstics of a diesel engine fuelled with garcinia gummi-gutta methyl ester (gggme) |
| topic | combustion chamber geometry Garcinia Gummi-Gutta methyl ester (GGGME). |
| topic_facet | combustion chamber geometry Garcinia Gummi-Gutta methyl ester (GGGME). камера згоряння геометрія метиловий етер олії гарцинії камбоджійської (Garcinia gummi-gutta) (GGGME). |
| url | https://ve.org.ua/index.php/journal/article/view/613 |
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