Diesel Engine Injection Rate-Shape Optimization Using Genetic Algorithms and Multi-Dimensional Modeling for a Range of Operating Modes

A recently developed engine optimization technique using a Genetic Algorithm optimization program with an IC engine combustion and emissions code, KIVA3V, has been applied to four steady state operating modes representing a subset of the EPA’s Federal Transient Test Procedure. Engine control parameters of boost pressure, exhaust gas recirculation (EGR), start of injection and injection rate shape were optimized to reduce emissions below EPA mandates and reduce indicated specific fuel consumption (ISFC) below current levels. The engine modeled was a single cylinder, direct injection, heavy-duty diesel engine, CAT 3401. Results showed that each operating mode, which included high and low speed and high, medium and low load, optimized engine control parameters such that below mandated emissions levels were achieved at reduced ISFC. All modes requested high EGR; most requested high boost pressure and near TDC start of injection. Each injection rate shape varied substantially from one to the other. Although the rate shape varied, resulting heat release rate and pressure curves were strikingly similar. Corresponding author Introduction The genetic algorithm (GA) is an optimization technique based on the process of natural selection. Since the introduction of its use in performance and emissions optimization of internal combustion (IC) engines [4], it has been used, and with good results, in a number of other IC engine related studies [1,5,6,8,9]. Senecal et al. [5] applied the GA to emissions and fuel consumption reduction by varying engine control parameters of boost pressure, EGR, start of fuel injection (SOI), injection pressure, percent of fuel injected in first of two injection pulses and dwell between pulses on the CAT 3401 oil test engine. The GA was able to find a combination of control parameters to simultaneously reduce soot and NOx, while slightly increasing indicated specific fuel consumption (ISFC) within an acceptable range. Subsequent to the modeling, engine experiments were carried out using the parameters found by the GA and excellent agreement was realized. In their next GA application, in addition to the parameters listed above, Senecal et al. [1] added injection rate shape flexibility. Further NOx and ISFC reduction was demonstrated, while soot was unchanged. Shrivastava et al. [6] applied the GA to the International 7.3L engine, varying the same engine control parameters as Ref. [5], plus swirl and tumble. Here again, substantial reductions were seen in emissions and ISFC. Wickman et al. [10] also saw emissions and ISFC benefits on the CAT 3401 and a high-speed, direct-injection, small bore diesel by optimizing bowl geometry, swirl, EGR, SOI, duration of injection, injector hole size and fuel plume orientation. This paper, expands on work by Senecal et al. [1], where boost pressure, exhaust gas recirculation (EGR), SOI and injection rate-shape were manipulated by the GA to reduce soot and NOx+HC (unburned hydrocarbon) to below the 2002-2004 EPA mandates, while keeping ISFC at, or below the CAT 3401 engine’s current baseline for this high speed, medium load operating mode. Senecal’s study was for mode 5 of the EPA’s FTP. This paper includes results for modes 2, 4, 5 and 6. Engine and Operating Modes Modeled The engine used for this study is the CAT 3401 oil test engine, which is a single cylinder version of the CAT 3406 heavy duty, direct injection, diesel engine. Table 1 lists engine specifications.