Utilizing Exhaust Valve Opening Modulation for Fast Warm-up of Exhaust After-treatment Systems on Highway Diesel Vehicles

Abstract

Current on-road vehicles are generally outfitted with exhaust after-treatment (EAT) systems to meet the stringent emission regulations. At cold start and low-loaded operations, those systems need to be warmed up above a threshold temperature (generally 250oC) for effective performance. High exhaust temperatures and high exhaust flow rates are required to accelerate the EAT warm up which are mostly not available at low-loaded diesel vehicle operations. Therefore, the objective of this work is to improve EAT warm up at low loads through utilizing exhaust valve opening (EVO) modulation which allows both elevated exhaust temperatures and exhaust flow rates. A 1-D engine simulation program is used to model the system which is set to operate at 1200 RPM engine speed and at 2.5 bar brake mean effective pressure (BMEP) engine load. Exhaust temperature can be increased above 250oC via either early or late EVO timings. Reduced expansion work in advanced EVO timings and increased pumping loss in retarded EVO timings require higher fuel consumption (up to 15 % and 20 %, respectively) to keep engine load constant. Those high fuel penalties reduce engine air-to-fuel ratio and rise exhaust temperature more than 55oC. Exhaust mass flow rate is improved up to 9 % in the system as well. The method increases exhaust gas energy up to 40 % and rises heat transfer rate to the EAT system up to 140 % compared to nominal condition. The technique is highly effective at heating up EAT systems, however, it also causes high fuel inefficiency which needs to be considered.

Effects of Intake Valve Lift Form Modulation on Exhaust Temperature and Fuel Economy of a Low-loaded Automotive Diesel Engine

“…The mathematical formulations for the model on Figure 1 can be found on a previous work which uses the same model and attempts to show that EVO timing modulation can considerably improve EAT warm-up at low loads [26]. Reasonable control of EVO timing has a significant potential to accelerate EAT warmup on highway vehicles.…”

“…Unlike Ref. [26], this work uses boot-shaped (BS) LIVC technique and mainly considers the exhaust temperature rise without a need to rise fuel consumption penalty. It also attempts to show that double-valve (DV) BS-LIVC and single valve (SV) BS-LIVC can have technological advantages compared to conventional LIVC technique.…”

“…However, expansion work is shortened in EEVO mode and thus, the system needs additional fuel in order to keep engine load constant [25]. Basaran shows that both EEVO and late exhaust valve opening (LEVO) can elevate exhaust temperature of a diesel engine up to 55 o C at a low-loaded operating condition [26]. It is also shown that high fuel penalty (up to 20 %) is a significant disadvantage which needs to be considered [26].…”

“…Basaran shows that both EEVO and late exhaust valve opening (LEVO) can elevate exhaust temperature of a diesel engine up to 55 o C at a low-loaded operating condition [26]. It is also shown that high fuel penalty (up to 20 %) is a significant disadvantage which needs to be considered [26]. Another energy-inefficient on-engine technique is to apply internal exhaust gas recirculation (IEGR) [27].…”

Control of pre and post transmission parallel hybrid vehicles with fuzzy logic method and comparison with other power systems

“…Dünyada tüketilen toplam enerjinin %27'sini ve atmosfere salınımı yapılan sera gazı emisyonunun %33'ünü karayollarında kullanılan araçlar oluşturmaktadır. Yüksek enerji tüketimi ve yüksek kirletici gaz emisyonlarının salınımına neden olan araçların çoğu sadece İYM (içten yanmalı motor) ile çalışan düşük verimlilik değerlerine sahip geleneksel araçlardır [1][2][3][4][5][6][7]. Fosil yakıtlı geleneksel araçların çevreye yaydığı zararlı gaz değerlerinin azaltılması amacı ile emisyon standartları her geçen gün arttırılmaktadır.…”