A Fast CFD-Based Methodology for Determining the Cyclic Variability and Its Effects on Performance and Emissions of Spark-Ignition Engines

Abstract

A methodology for determining the cyclic variability in spark-ignition (SI) engines has been developed recently, with the use of an in-house computational fluid dynamics (CFD) code. The simulation of a large number of engine cycles is required for the coefficient of variation (COV) of the indicated mean effective pressure (IMEP) to converge, usually more than 50 cycles. This is valid for any CFD methodology applied for this kind of simulation activity. In order to reduce the total computational time, but without reducing the accuracy of the calculations, the methodology is expanded here by simulating just five representative cycles and calculating their main parameters of concern, such as the IMEP, peak pressure, and NO and CO emissions. A regression analysis then follows for producing fitted correlations for each parameter as a function of the key variable that affects cyclic variability as has been identified by the authors so far, namely, the relative location of the local turbulent eddy with the spark plug. The application of these fitted correlations for a large number of engine cycles then leads to a fast estimation of the key parameters. This methodology is applied here for a methane-fueled SI engine, while future activities will examine cyclic variations in SI engines when fueled with different fuels and their mixtures, such as methane/hydrogen blends, and their associated pollutant emissions.

An experimental investigation of the performance, emission and combustion stability of compression ignition engine powered by diesel and ammonia solution (NH4OH)

“…The stability of an internal combustion engine operation related to the non-repeatability of the subsequent operating cycles and ignition misfiring can be assessed based on variation of IMEP 35 and also on the basis on variation of the maximal combustion pressure -COV pmax . [36][37][38] Figure 6 presents the coefficients of ). The results correspond to the tests carried out in Test 0 and Test 1, described in Table 1.…”

“…The stability of an internal combustion engine operation related to the non-repeatability of the subsequent operating cycles and ignition misfiring can be assessed based on variation of IMEP 35 and also on the basis on variation of the maximal combustion pressure -COV pmax . [36][37][38] Figure 6 presents the coefficients of variation of the maximal combustion pressure determined for the analysed engine loads (35%, 60% and 100%) for the engine fuelled only with diesel (reference fuel) and DF with WAS (Figure 6(a)) and the dispersion of the maximum pressure value in individual engine operating cycles around the mean values of p max , determined for 200 engine operating cycles (Figure 6(b)). The results correspond to the tests carried out in Test 0 and Test 1, described in Table 1.…”

Investigating the Optimization Design of Internal Flow Fields Using a Selective Catalytic Reduction Device and Computational Fluid Dynamics

“…The evaluation of the design results was mainly based on the coefficient of variation, that is, the ratio of the standard deviation to the mean called the coefficient of variation, which is recorded as the coefficient of variance (C V ) [26,27]. The acceptance criteria for the final result of the CFD simulation optimization: Ammonia injection grille (AIG) upstream velocity distribution: the maximum C V was 15%; (2) The upstream temperature field distribution of the first-layer catalyst: the maximum deviation of the flue gas temperature ratio from the average value was within the range of ±10 • ; (3) The upstream of the first-layer catalyst velocity distribution: the maximum C V in the cross section was 15%; (4) The upstream velocity angle of the firstlayer catalyst: the maximum angle deviated from the vertical line was ±10 • ; and (5) The upstream ammonia distribution (NH 3 /NO x ) of the first-layer catalyst: the maximum C V was 5%.…”

Influence of Compression Ratio on Flywheel Dimension for a Naturally Aspirated Spark Ignition Engine: A Numerical Study

“…The essential of IMEP parameters has also been studied by several researchers in some other related topics [18], [20], [21]. These studies show the needs of IMEP assessment in determining engine performance characteristics.…”