Modelling the effect of intake valve closing timing on exhaust thermal management of a turbocharged and intercooled diesel engine

Year 2016, Issue: 206, 3 - 17, 01.12.2016

HASAN ÜSTÜN Başaran

Abstract

Emissions from diesel engines have become recently a significant problem due to their positive effect

on global-warming. There are strict restrictions on emissions and low-emission diesel engines

nowadays are required to be developed. One of the solution for reduced-emission diesel engines is to

utilize exhaust thermal management systems. However; these systems work efficiently mostly at

temperatures above 250 oC and for diesel engines, especially at low speed and low load conditions,

exhaust gas temperatures are not generally higher than 250 oC. That not only leads to inefficient

aftertreatment systems, but also insufficient emission reduction. Variable valve timing (VVT) can be

used to achieve those high exhaust gas temperatures by changing the opening and closing timings of

the intake&exhaust valves at any speed and any load. Therefore, the aim of this study is to try to

increase the turbine exit temperature of a diesel engine above 250 oC at 2.50 bar brake mean effective

pressure (bmep) and 1200 rpm engine speed condition by changing intake valve closing (IVC) timings.

Diesel engine system is simulated by using Lotus Engine Simulation (LES) program. The model is then

validated with experimental results. It is seen that exhaust gas temperatures can be raised higher than

250 oC for the studied particular engine loading case when IVC is advanced or retarded. The method

results in fuel consumption saving in comparison to nominal valve timing by decreasing the required

fuel injection rate for the constant engine loading. However, earlier and later closing of intake valve

also causes exhaust flow rate to drop off.

Keywords

Diesel engines, exhaust thermal management, variable valve timing, turbine exit temperature.

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