Article pubs.acs.org/EF
Methodology for Estimating the Performance of Fuels during Cold Start and Idle with the Adaptation of a Gradation System A. Piperel,*,† H. Perrin,† B. Walter,† G. Crépeau,‡ and L. Starck† †
IFP Energies Nouvelles, 1&4 Avenue du Bois Préau, 92852 Rueil-Malmaison, France PSA Peugeot Citroën, 18 Rue des Fauvelles, 92250 La Garenne Colombes, France
‡
ABSTRACT: The objective of this study is to develop a methodology able to discriminate fuels in their ability to produce good cold start and idle in a recent Euro V, direct injection diesel engine for passenger car. This methodology aims at easily comparing fuels during the starting phase and idle by the use of a grade from 2 to 10. Engine tests, consisting in starting the engine and then let it running in idle, are operated at −7 °C, −18 °C, and −25 °C. This grading system is based on the evaluation of reference fuels among three commercial fuels: an Arctic grade diesel fuel supposed to be the highest level reference fuel, and two fuels, with a low cetane number and intermediate cold properties, supposed to be low level reference fuels. The engine behavior is evaluated with the help of criteria characterizing the starting phase and idle. These reference fuels give the conventional maxima limits on each criteria and are used to develop the methodology able to evaluate the fuel impact. An illustration is given to this grading system using an EU winter commercial fuel with intermediate cold properties.
1. INTRODUCTION The transportation industry is a large contributor to the pollutant emissions, and fossil fuel consumption. However, this industry is trying to find new ways in order to both save fossil fuel and limit pollutant emissions, while ensuring a high level of security, from the production of energy to the passengers in the cabin, while also maintaining excellent driveability and competitive sales prices. Among all types of internal combustion engines, diesel engine is one of the best to reduce CO2 emissions.1 In order to achieve a more significant reduction in terms of pollutant emissions and consumption, it often makes sense to combine a strong downsizing and a volumetric compression ratio (CR) reduction to increase the specific power and torque and a use of alternative fuels.2,3 However, this coupling is not always without indirect consequence on the engine: faster wear of parts, bad starts, more combustion noise, and many other phenomena that could affect customer complaints. Indeed, this decrease in the engine CR (current engine CR are decreasing until 15:1)4,5 affects engine operation at low and extremely low temperatures (i.e., from −5 to −30 °C),6 by leading to longer start delay and higher pollutant emissions. For this reason, a new test is required to demonstrate the propensity of some fuels to induce good or on the contrary bad engine behavior at very low temperature in modern engines. Furthermore, some alternative fuels can have low cold flow properties and sometimes lower cetane number (CN),7−12 which could lead to a bad cold behavior: longer start delay and higher exhaust gas opacity. The use of this kind of fuel could show some difficulties with some configurations of diesel engines. This study aims at developing a methodology to evaluate the influence of fuels during cold start and idle in an objective way taking into account a variety of criteria: start delay, engine stability, and smoke opacity during start and idle. The development of this methodology is based on previous works conducted by the French ″Groupement Scientifique Moteurs″.13 © 2013 American Chemical Society
This study goes further than previous works by using reference fuels and by adapting a gradation system. For that, a partnership is done between a research center (IFPEN), a car manufacturer (PSA), and an equipment manufacturer (R. Bosch). One key aspect is to define the importance of each criterion: the priority is given to the criteria that are representative of the customer complaint. So, the purpose is to objectively evaluate the global performance of fuels during the starting phase and idle and to easily compare fuels between them in a more impartial way. Tests are performed on a PSA DV6D Euro 5 diesel engine using reference fuels: one supposed to be the high level reference and one other supposed to lead to a worse behavior in cold operation. The tested fuels for each criteria lead to values supposed to be extreme limits, that is, good for the high level reference fuel and bad for the low level reference fuel, with a variation of conventional grade from 10 to 2. Engine tests consist of starting the engine and then let it running in idle, they are operated at −7 °C, −18 °C, and −25 °C, but this methodology could be applied at another temperature. The engine behavior is evaluated with the help of criteria characterizing the starting phase and idle. Furthermore, an EU winter commercial fuel is also tested in order to provide an illustration of the methodology application.
2. EXPERIMENTAL SETUP 2.1. Engine and Test Cell. Tests are performed on a PSA DV6D diesel engine whose specifications and dimensions are indicated in Table 1; injection strategies used during the idle phase are given in Table 2. This engine is chosen to be representative of modern European highspeed direct injection diesel engines, able to comply with the requirements of current and future European emission levels. It is representative of Euro V tendencies: combustion chamber design, compression ratio and injection technology available from PSA and R Received: October 9, 2012 Revised: January 11, 2013 Published: January 30, 2013 1625
dx.doi.org/10.1021/ef3016574 | Energy Fuels 2013, 27, 1625−1631
Energy & Fuels
Article
Table 1. Engine Specifications design capacity combustion chamber compression ratio power torque injection system emissions control
Table 3. Fuel Properties
four cylinders in line, overhead camshaft, turbocharged with EGR 1560 cm3 height valves, direct injection
CN CFPP (°C) cloud point (°C) density (kg/m3) IBP (°C) FBP (°C) %C (% mass) %H (% mass) %O (% mass) H/C ratio %S (mg/kg) aromatic content (% mass)
16:1 68 kW at 4000 rpm 230 Nm at 1750 rpm common rail with R Bosch electronically controlled 7-holes injectors conforms with Euro V limit values when combined with exhaust gas after-treatment system (DPF)
Bosch. The ECU (Electronic Control Unit) used for these tests runs with a recent software, secured by R. Bosch. The test cell allows us to operate tests consisting in starting the engine and then an idle or low load running phase, in a large range of temperatures, that is, from −30 °C to +40 °C. The engine can be coupled to a dynamometer in order to absorb engine torque during cleaning phase operated after each cold start phase. The D2T software Morphee 2 is used to manage the test cell, especially the decrease in temperature, the engine tests (e.g., preglowing, cranking, engine start then idle), and to acquire data from test cell and engine all along the tests. In parallel, ECU data are acquired by an ETAS Inca system. 2.2. Fuels. Several fuels are used in order to develop the methodology able to evaluate the fuel impact. Two of them are supposed to become reference fuels. A commercial fuel is tested at the end of the tests in order to validate the methodology and to prove that this methodology is really able to discriminate fuel during cold operations. The fuel properties are given in Table 3. Arctic fuel is supposed to become ″high level″ reference fuel. In order to determine one ″low level″ reference fuel, two fuels are chosen with a low cetane number and with intermediate cold properties. Carcal US and a Carcal 40 correspond to these characteristics. These reference fuels should have good cold flow properties in order to not cause troubles during tests at −25 °C. The fuel used for validation of this methodology is an EU winter commercial fuel. This fuel is added with a CFPP (cold filter plugging point) additive, due to the fact that the original fuel freezes at −25 °C. This fuel is representative of a fuel sales in Western Europe. 2.3. Operating Conditions. The engine runs in a test cell controlled in temperature and humidity. The inside temperature can be decreased to −30 °C, but the tests are run at −7 °C, −18 °C, and −25 °C. These temperatures are chosen in order to be representative of current uses: −7 °C corresponding to cold homologation and −25 °C being used during tests validation in extreme conditions. The −18 °C is, in fact, an intermediate condition. The room is dehumidified in order to avoid ice creation in the room and on the engine. Before the test, the temperature of the cell is decreased, and when all the components: air, engine and fluids (water, oil, fuel) get the targeted temperature (−7 °C, −18 °C, or −25 °C), a period of soaking (one hour
a
arctic (high ref)
Carcal US (low ref for start)
Carcal 40 (low ref for idle)
EU winter commercial fuel (example)
57 −45 −29
47 −25 −25
42 −51 −27
53 −23a −8
829
852
856
839
174 337 86.1 13.7
