09-05-2014, 04:24 PM
Investigation of emission characteristics affected by new cooling system in a diesel engine
Investigation of emission .pdf (Size: 325.39 KB / Downloads: 24)
Abstract
In a typical cooling system of automotive engine, a mechanical water pump is used to control the flow rate of coolant.
However, this traditional cooling system is not suitable for a high efficiency performance in terms of fuel economy and
exhaust emission. Therefore, it is necessary to develop a new technology for engine cooling systems. These days, the
electronic water pump is spotlighted as the new cooling system of an engine. The new cooling system can provide
more flexible control of the coolant flow rate and the engine temperature, which used to be strongly relied on the en-
gine driving conditions such as load and speed. In this study, an engine experiment was carried out on a New European
Drive Cycle (NEDC) with a 2.7L diesel engine. The electric water pump operated by BLDC motor and the electronic
valve were installed in the cooling system to control the coolant flow rate and temperature. This paper explains that the
exhaust emissions were reduced with an increase in the engine temperature and a decrease in the coolant flow. From
this experiment, we found that increasing coolant temperature had a significant effect on reducing the emissions (e.g.
THC and CO). Decreasing coolant flow also affected the reduction of emissions. In contrast, NOx emission was ob-
served to increase in these conditions.
Introduction
A typical automotive engine cooling system has
three major components, namely, a mechanical water
pump, cooling fans, and a wax-type thermostat. [1-5]
These components are not independent of various
engine driving conditions. The pump and fans are
coupled with a crank shaft by belts, thereby being
subject to the engine operating speed. [7-10] Further-
more, the mechanical cooling pump is not able to sup-
ply sufficient flow for cabin heating at idle condition
because of its low efficiency. [11] With respect to the
thermostat, its opening and closing relies only on
thermal expansion of wax. This gives rise to some
shortcoming such as high pressure drop,
Experimental apparatus
The experimental set-up used in this study is shown
in Fig. 1. It consisted of a cooler substituted for a ra-
diator in real vehicles, an electric water pump, an elec-
tronic valve replaced with the wax-type thermostat,
and an emission sampling system (Horiba MEXA-
7100DEGR). The engine for this experiment was the
2.7L HSDI diesel engine. The specifications of the
engine are summarized in Table 1.
CONCLUSION
In this study, an electric water pump and electronic
valves were adapted for a new cooling strategy. The
coolant temperature and flow rate were controlled
using the electric water pump and electronic valves.
The experimental results are summarized as follows:
• At partial load conditions of NEDC drive cycle,
THC and CO were reduced by approximately
10 % and 4%, respectively.
• In the case of decreasing coolant flow, THC and
CO were reduced down to 20% during NEDC
drive cycle.
• The zero-flow warm-up strategy helped the engine
temperature raise faster compared to the tradi-
tional strategy.
• Controlling the flow path also shortened the
warm-up period. Significant reduction of the
warm-up period was achieved by closing valve
between the engine and the oil cooler.