Gasoline engine performance simulation of water injection and low-pressure exhaust gas recirculation using tabulated chemistry

Abstract

<jats:p> This work presents the assessment of direct water injection in spark-ignition engines using single cylinder experiments and tabulated chemistry-based simulations. In addition, direct water injection is compared with cooled low-pressure exhaust gas recirculation at full load operation. The analysis of the two knock suppressing and exhaust gas cooling methods is performed using the quasi-dimensional stochastic reactor model with a novel dual fuel tabulated chemistry model. To evaluate the characteristics of the autoignition in the end gas, the detonation diagram developed by Bradley and co-workers is applied. The single cylinder experiments with direct water injection outline the decreasing carbon monoxide emissions with increasing water content, while the nitrogen oxide emissions indicate only a minor decrease. The simulation results show that the engine can be operated at λ = 1 at full load using water–fuel ratios of up to 60% or cooled low-pressure exhaust gas recirculation rates of up to 30%. Both technologies enable the reduction of the knock probability and the decrease in the catalyst inlet temperature to protect the aftertreatment system components. The strongest exhaust temperature reduction is found with cooled low-pressure exhaust gas recirculation. With stoichiometric air–fuel ratio and water injection, the indicated efficiency is improved to 40% and the carbon monoxide emissions are reduced. The nitrogen oxide concentrations are increased compared to the fuel-rich base operating conditions and the nitrogen oxide emissions decrease with higher water content. With stoichiometric air–fuel ratio and exhaust gas recirculation, the indicated efficiency is improved to 43% and the carbon monoxide emissions are decreased. Increasing the exhaust gas recirculation rate to 30% drops the nitrogen oxide emissions below the concentrations of the fuel-rich base operating conditions. </jats:p>

Development of a Computationally Efficient Tabulated Chemistry Solver for Internal Combustion Engine Optimization Using Stochastic Reactor Models

“…For Diesel combustion, the approach initially proposed by Kožuch [45] was adopted and validated by Franken et al [46] across a large set of operating points. For gasoline engine conditions, the K-k model proposed by Dulbecco et al [47] was implemented and validated in the SRM framework for different gasoline fuel surrogate mixtures in [48,49]. Examples of the mixing time histories that are computed with the mentioned turbulence models are shown in Figure 2 as function of crank angle degrees (CAD) assuming 0 as firing top dead center (TDCf).…”

“…The experimental data were measured on a single cylinder research engine at the TU Berlin [48]. Cylinder bore and stroke are 82.0 and 71.9 mm, respectively, while the compression ratio is 10.75:1.…”

A comparative study into the effects of pre and post catalyst exhaust gas recirculation on the onset of knock

“…There are a number of alternative strategies for controlling knock without the need for overfuelling and EGR is particularly prominent in this area. 1,2 The dilution effect of EGR can mitigate the risk of knocking combustion at high loads 3 whilst also providing fuel economy benefits at low load by reducing throttling losses. 4 Anticipated CO restrictions in the Euro 7 emissions regulations, alongside the real driving emissions (RDE) test protocols, have added to the pressure on OEMs to realise lambda one operation across the entire operating range of their engines.…”

“…There are a number of alternative strategies for controlling knock without the need for overfuelling and EGR is particularly prominent in this area. 1,2 The dilution effect of EGR can mitigate the risk of knocking combustion at high loads 3 whilst also providing fuel economy benefits at low load by reducing throttling losses. 4…”

Special issue: Symposium for combustion control 2019

“…Another very important aspect of control development is always the process simulation. In the contribution of Franken et al, 16 a performance simulation of water injection in gasoline engines with low-pressure EGR was presented using single-cylinder experiments and simulations based on tabulated chemistry. In addition to the improvement of fuel consumption, the potential for reducing emissions was also impressively demonstrated.…”