Engine performance and emissions analysis in a cold, intermediate and hot start diesel engine

Presented in this paper is an in-depth analysis of the impact of engine start during various stages of engine warm up (cold, intermediate, and hot start stages) on the performance and emissions of a heavy-duty diesel engine. The experiments were performed at constant engine speeds of 1500 and 2000 rpm on a custom designed drive cycle. The intermediate start stage was found to be longer than the cold start stage. The oil warm up lagged the coolant warm up by approximately 10 °C. During the cold start stage, as the coolant temperature increased from ~25 to 60 °C, the brake specific fuel consumption (BSFC) decreased by approximately 2% to 10%. In the intermediate start stage, as the coolant temperature reached 70 °C and the injection retarded, the indicated mean effective pressure (IMEP) and the brake mean effective pressure (BMEP) decreased by approximately 2% to 3%, while the friction mean effective pressure (FMEP) decreased by approximately 60%. In this stage, the NOx emissions decreased by approximately 25% to 45%, while the HC emissions increased by approximately 12% to 18%. The normalised FMEP showed that higher energy losses at lower loads were most likely contributing to the heating of the lubricating oil.</p

Combustion Analysis of a Diesel Engine during Warm up at Different Coolant and Lubricating Oil Temperatures

A comprehensive analysis of combustion behaviour during cold, intermediately cold, warm and hot start stages of a diesel engine are presented. Experiments were conducted at 1500 rpm and 2000 rpm, and the discretisation of engine warm up into stages was facilitated by designing a custom drive cycle. Advanced injection timing, observed during the cold start period, led to longer ignition delay, shorter combustion duration, higher peak pressure and a higher peak apparent heat release rate (AHRR). The peak pressure was ~30% and 20% and the AHRR was ~2 to 5% and &plusmn;1% higher at 1500 rpm and 2000 rpm, respectively, during cold start, compared to the intermediate cold start. A retarded injection strategy during the intermediate cold start phase led to shorter ignition delay, longer combustion duration, lower peak pressure and lower peak AHRR. At 2000 rpm, an exceptional combustion behaviour led to a ~27% reduction in the AHRR at 25% load. Longer ignition delays and shorter combustion durations at 25% load were observed during the intermediately cold, warm and hot start segments. The mass fraction burned (MFB) was calculated using a single zone combustion model to analyse combustion parameters such as crank angle (CA) at 50% MFB, AHRR@CA50 and CA duration for 10&ndash;90% MFB

Engine Performance and Emissions Analysis in a Cold, Intermediate and Hot Start Diesel Engine

Presented in this paper is an in-depth analysis of the impact of engine start during various stages of engine warm up (cold, intermediate, and hot start stages) on the performance and emissions of a heavy-duty diesel engine. The experiments were performed at constant engine speeds of 1500 and 2000 rpm on a custom designed drive cycle. The intermediate start stage was found to be longer than the cold start stage. The oil warm up lagged the coolant warm up by approximately 10 &deg;C. During the cold start stage, as the coolant temperature increased from ~25 to 60 &deg;C, the brake specific fuel consumption (BSFC) decreased by approximately 2% to 10%. In the intermediate start stage, as the coolant temperature reached 70 &deg;C and the injection retarded, the indicated mean effective pressure (IMEP) and the brake mean effective pressure (BMEP) decreased by approximately 2% to 3%, while the friction mean effective pressure (FMEP) decreased by approximately 60%. In this stage, the NOx emissions decreased by approximately 25% to 45%, while the HC emissions increased by approximately 12% to 18%. The normalised FMEP showed that higher energy losses at lower loads were most likely contributing to the heating of the lubricating oil

Reducing cold start fuel consumption through improved thermal management

Deposited with permission of the author © 2008 Faisal Samad LodiThe thesis presents research in achieving faster warm-up of an SI engine, thereby affecting the fuel economy penalty. The faster warm-up relates to faster heating of the cylinder head and engine block, targeting reducing viscous friction in the cold oil as the most likely candidate to improve. The strategy applied was to reduce the coolant flow circulation rate to achieve a faster warm-up of the engine. A lumped parameter model for engine heat transfer, coolant flow and heat capacities, in a single cylinder, based on engine operating points like spark advance, engine speed and MAP was built in Modelica. The engine used for experimentation was a Ford in-line, 4 stroke, 6-cylinder engine, with a compression ratio of 10.3:1, in which 56 K-type thermocouples were installed at different locations to measure the temperature. The experiments were performed with varying coolant flow rate from normal down to zero, utilizing an electric water pump, over an approximation to the New European Drive Cycle (NEDC), at a speed of 1161 rev/min and load of 48 Nm. The selected speed and load were the average operating condition for 180 seconds of engine running over the urban part of a simulated NEDC. In addition, the coolant circuit was modified to a split cooling supply and the sets of results analyzed to find the reduction in engine warm-up time and fuel consumption. It is shown from the results that the warm-up time of the engine and the fuel consumption were notably reduced, as the flow was reduced from maximum to minimum in steps. On average over an interval of engine running for 300 seconds from cold start, the cylinder head temperature was increased by about 2°C , the average engine block temperature was increased by about 6.5°C and the average cylinder head coolant temperature was increased by about 4°C . However, the bulk temperature of the oil in the oil sump showed marginal improvement and remained consistent, even at the lowest coolant flow rate. Nonetheless, the improvements in block temperature had significant effects on reducing the friction between the piston and cylinder walls. Analysis of the results show that the coolant flow pattern changed with the use of an electric water pump. The flow is less evenly distributed around the cylinders with the use of an electric water pump, whilst retaining the mechanical water pump body, compared to the mechanical water pump operation. The model was applied to simulate for two engine operating points, i.e., 1161 rev/min, 48 Nm load and 700 rev/min and 0 Nm load. The model was calibrated at 1161 rev/min, 48 Nm load and validated at 700 rev/min, 0 Nm load. The modeling results were in fair agreement with the experimental results. The model can be employed to investigate electric water pump control. The important finding is that around 3% fuel consumption savings are possible over the NEDC by management strategies that lead to faster cylinder block warm up, even though this may result in little or no change in oil temperature as measured in the sump

Statistical Analysis of the Results Obtained by Thermodynamic Methods for the Determination of TDC Offset in an Internal Combustion Engine

Presented is a comprehensive evaluation of thermodynamic techniques used for the determination of top dead centre (TDC) in an internal combustion engine (ICE). This work thoroughly explores the assumptions made in thermodynamic calibration and assesses the impact these have through a rigorous sensitivity analysis, not previously attempted in any other study. The results of this work are presented as kernel density estimates (KDEs), an estimate of the probability density function (pdf), in order to offer both qualitative and quantitative assessments of the loss angle and the influence of the assumptions underpinning the loss angles determination. Thermodynamic loss angles ranging between-0.5CA and-0.6CA have been found for the engine under investigation.</p

Gaseous and particulate emissions analysis using microalgae based dioctyl phthalate biofuel during cold, warm and hot engine operation

Presented in this study is an analysis of gaseous and particulate emissions for three selected fuels during cold, warm and hot engine operation; low sulphur neat diesel (D100), and 10 and 20% (% v/v) of dioctyl phthalate (DOP) blended with diesel. Experiments were conducted on a turbocharged common rail heavy-duty diesel engine over a custom-designed drive cycle. The impact of engine temperature and fuel properties during warm-up on emissions has been analysed. The presence of oxygen molecules in DOP was found to have a major influence on emissions. NOx emissions were higher by ∼ 10%, while the HC emissions were lower by ∼ 150% with DOP blended fuels, compared to D100, during cold engine operation. Total particle number (PN) concentration and total particle mass (PM) followed the same trend and decreased as the engine warmed up. Compared to both DOP blended fuels, total PN with D100 was higher during cold engine operation and reduced significantly as the engine warmed up. The particle count median diameter (CMD) was found to have an opposite trend with D100 (increasing with engine warm-up) compared to both DOP blended fuels (decreasing with engine warm-up).</p

Cold idle vs hot idle: Gaseous and particulate emissions using a third-generation oxygenated biofuel

Engine idling is a significant contributor to vehicle emissions, however, it is often unaccounted for. Presented in this study is a comprehensive analysis of gaseous and particulate emissions during cold idle compared to hot idle operations. Fuels used in this study were B20 (20 %) and B10 (10 %) (%v/v) blends of di-octyl phthalate (a third-generation microalgae-based biofuel) and ultra-low sulphur diesel (B00), used as a reference fuel. Compared to cold idle operation, hydrocarbon (HC) emissions during hot idle showed marginal variation (±10 %) using blended fuels, and a significant increase (+55 %) using B00. Compared to cold idle operation, hot idle showed increased oxides of nitrogen (NOx) emissions, using all fuels (with a more significant increase shown using B00). During cold idle, particle concentrations (PNT) were 50–65 % higher using the blended fuels, compared to B00; however, during hot idle, the (PNT) using the blended fuels were one order of magnitude lower than B00. During cold idle operation, the average particle count mean diameter (CMD) in the Lower Aitken and Aitken modes was 5–10 % and 20–30 % higher using blended fuels, compared to B00, respectively. Higher CMD with the blended fuels during the cold idle operation caused a higher percentage increase in the particle mass (PMT), compared to B00. Sub-23 particles (<23 nm) were observed during cold and hot idle operations, using all fuels.</p

Experimental and numerical analysis of engine gas exchange, combustion and heat transfer during warm-up

This paper presents experimental and computational results obtained on an in line, six cylinder, naturally aspirated, gasoline engine. Steady state measurements were first collected for a wide range of cam and spark timings versus throttle position and engine speed at part and full load. Simulations were performed by using an engine thermo-fluid model. The model was validated with measured steady state air and fuel flow rates and indicated and brake mean effective pressures. The model provides satisfactory accuracy and demonstrates the ability of the approach to produce fairly accurate steady state maps of BMEP and BSFC. However, results show that three major areas still need development especially at low loads, namely combustion, heat transfer and friction modeling, impacting respectively on IMEP and FMEP computations. Satisfactory measurement of small IMEP and derivation of FMEP at low loads is also a major issue. Measurements of fuel consumption were then collected during warm up for different configurations of the cooling system, with a standard mechanical water pump (MWP) and an electrical water pump (EWP), at a constant BMEP and engine speed. Simulations were performed by using the previous model to compute IMEP and FMEP. Modeling friction during warm-up, when temperatures of head metal, block metal, coolant and oil are well below hot steady values and decoupled to some extent (split or no flow coolant tests) proves to be challenging. Computational results complement the experimental data, demonstrating the utility of the integrated approach in improving the design of the cooling system for faster warm-up