Statistical and experimental investigation of the influence of fuel injection strategies on gasoline/diesel RCCI combustion and emission characteristics in a diesel engine

ABSTRACT

The combustion and emission characteristics of CRDI engine fueled with gasoline/diesel blends operated under reactivity-controlled compression ignition (RCCI) model is investigated in this study. Experimental investigations are carried out on a single-cylinder water-cooled research engine at a constant speed of 3000 rpm with variable engine load (16, 20, and 24 Nm) to study the influence of fuel injection timings (7.5, 12.5, and 17.5 SOI) and injection pressure (500, 750 and 1000 bar). In the case of a fuel injection pressure of 1000 bar, the maximum brake specific fuel consumption of 0.42 kg/kWh is registered with a brake mean effective pressure of 3.2 bar. Response surface methodology has been used in this analysis for predicting the optimal input parameters (engine load, fuel injection timing, and fuel injection pressure), which results in an optimal combination of performance (BP, BTHE, and BSFC) and emission (HC, NOx, and Co) parameters. A variety of optimal solutions based on the desirability method is obtained from the model, and optimal input parameters is suggested as load 20 (Nm), injection pressure 750 (Bar), and injection timing (BTDC) 12.5. Additionally, to obtain a ‘regression model’ a statistically significant test (ANOVA) is developed. Results have shown that the suggested ‘Regression Model’ is best fitted to 0.095 standard deviations, 0.972 corrected R², and 18.482 acceptable accuracy.

Graphical Abstract

KEYWORDS:

• Diesel
• gasoline
• injection timings
• injection pressure
• anova
• response Surface Methodology
• performance and Emission

Author contributions

S.K.Gugulothu: Conceptualisation, methodology, writing, review and editing, J. Ramchander: Formal analysis and investigation, writing original draft and preparation G.R.K Sastry: Supervision.

Nomenclature

BTE – Brake Thermal Efficiency (%)

BSEC – Brake Specific Energy Consumption (kJ/kWhr)

BSFC – Brake Specific Fuel Consumption (kg/kWhr)

DI – Direct Injection

CI – Compression Ignition

NOx – Oxides of nitrogen (ppm)

CO – Carbon mono-oxide (% vol)

HC – Hydrocarbon (ppm)

CO₂ - Carbon dioxide (% vol)

NHRR – Net Heat Release Rate (J/deg)

CP – Cylinder Pressure (bar)

dP/dƟ - Rate of Pressure Rise

MFB – Mass Burn Fraction

SOI – Start of Injection

FIP – Fuel Injection pressure

RSM – Response surface methodology

Highlights

• Performance, combustion, and emissions of a CRDI diesel engine were investigated

• HC and NOx have been decreased for lower FIP.

• At SOI of 342.5 CA, lower exhaust gas temperature is observed.

• The response surface methodology helps to find optimum factors

• ‘Regression Model’ is best fit with standard deviation of 0.095, adjusted R2 of 0.972 and adequate precision of 18.482.