Size impact of cerium oxide nanoparticles (CeO₂) on ternary fuel blend using third-generation biodiesel in VCR diesel engine

Abstract

An experiment was conducted to examine the impact of blending third-generation biodiesel waste cooking biodiesel (WCO biodiesel) and Azolla pinnata microalgae biodiesel (APO biodiesel) with cerium oxide nanoparticles (CeO₂ NPs) at 40 ppm concentration, encompassing sizes of 20, 50, and 100 nm. These biodiesels were generated via methanol-KOH trans-esterification. The investigation was carried out on a Kirloskar TV1 single-cylinder four-stroke variable compression ratio (VCR) diesel engine across load variations (0–100%) and compression ratios (i.e., CRs 16, 17, and 18) at a consistent 1500 rpm engine speed. Among various test fuel blends, D80W10A10CNP50 (Diesel 80% + WCO 10% + APO 10% + 40 ppm CeO₂ 50 nm) yielded optimized results across all conditions. Incorporating CeO₂ NPs boosted brake thermal efficiency (BTE) by reducing brake-specific energy consumption (BSEC), and it facilitated efficient combustion as a catalyst, leading to decreased emissions. NP size notably influenced these enhancements. Specifically, employing 50 nm NPs yielded optimal performance parameters and reduced exhaust emissions across all CRs. At CR-17, as compared to additive-free D80W10A10, the fuel formulation, including 50 nm NPs, resulted in an 11.1% BTE increase and a 6.03% BSEC decrease. Also, emission parameters revealed that carbon monoxide (CO), unburnt hydrocarbons (UBHC), nitrogen oxides (NO_X), and smoke opacity decreased by 30.76%, 25.44%, 9.12%, and 13.64%, respectively, while carbon dioxide (CO₂) emissions increased by 10.09%. These results may help elucidate the chemical mechanism of action of NPs and open the way for developing a more effective fuel additive.

Graphical abstract

Appendix

Formulations used

The general equations used for different performance parameters such as BTE, BSFC, and BSEC are given from Eqs. (6)–(11).

Calculations

• (a) Brake power (BP) in kW

  $${\text{BP}} = \frac{{2{\uppi }.{\text{N}}.{\text{T}}}}{60 \times 1000} = \frac{{2{\uppi }.{\text{N}}.{\text{W}}.{\text{g}}.{\text{R}}}}{60 \times 1000}{\text{ kW}}$$

  (6)

  where N: engine speed in RPM, T: torque in Nm, W: load on dynamometer in kg, R: dynamometer arm length = 0.185 m, g: acceleration due to gravity = 9.81 m s⁻².

• (b) Total fuel consumption (TFC, $\dot{m}_{{\text{f}}}$) in kg h⁻¹

  $${\text{TFC}}\left( {\dot{m}_{{\text{f}}} } \right) = \frac{{20 \times \rho_{{{\text{oil}}}} \times 3600}}{{t \times 10^{6} }} = \frac{{0.072 \times \rho_{{{\text{oil}}}} }}{t} \;{\text{kg}}/{\text{h}}$$

  (7)

  where t: time for consumption of 20 cc of fuel, $\rho_{{{\text{oil}}}}$: density of fuel = 830 kg m⁻³ for diesel.

• (c) Brake-specific fuel consumption (BSFC) in kg kW⁻¹ h⁻¹

  $${\text{BSFC}} = \frac{{{\text{Total}}\;{\text{Fuel}}\;{\text{Consumption}}}}{{{\text{Brake}}\;{\text{Power}}}} = \frac{{0.072 \times \rho_{{{\text{oil}}}} }}{{t \times {\text{BP}}}} \;\frac{{{\text{kg}}}}{{{\text{kW}}\;{\text{h}}}}$$

  (8)

• (d) Brake thermal efficiency ($\eta$ _bth)

  $$\eta_{{{\text{bth}}}} \left( \% \right) = \frac{{{\text{Brake}}\;{\text{Power}}\;{\text{in}}\;{\text{kW}}}}{{{\text{Rate}}\;{\text{of}}\;{\text{heat}}\;{\text{input}}}} = \frac{{{\text{Brake}}\;{\text{Power}}}}{{{\text{Fuel}}\;{\text{consumption}}\;{\text{in}}\;{\text{kg }}{\text{s}}^{-1} \times {\text{HV}}}}$$

  (9)
  $$\eta_{{{\text{bth}}}} \left( \% \right) = \frac{{{\text{Brake}}\;{\text{Power}} \times 3600}}{{\dot{m}_{{\text{f}}} \times {\text{HV}}}} \times 100$$

  (10)

  where $\dot{m}_{{\text{f}}}$: total fuel consumption in kg h⁻¹, HV: heating value of fuel in kJ kg⁻¹.

• (e) Brake-specific energy consumption (BSEC)

  $${\text{BSEC}} = \frac{{{\text{Heating}}\;{\text{value}} \times {\text{Total}}\;{\text{Fuel}}\;{\text{Consumption}}}}{{{\text{Brake}}\;{\text{Power}}}}$$

  (11)