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Research Papers: Internal Combustion Engines

Engine Rapid Shutdown: Experimental Investigation on the Cooling System Transient Response

[+] Author and Article Information
Rocco Piccione

Department of Mechanics, University of Calabria, 87030 Arcavacata di Rende (Cosenza), Italyr.piccione@unical.it

Sergio Bova

Department of Mechanics, University of Calabria, 87030 Arcavacata di Rende (Cosenza), Italys.bova@unical.it

J. Eng. Gas Turbines Power 132(7), 072801 (Apr 08, 2010) (10 pages) doi:10.1115/1.4000262 History: Received October 02, 2008; Revised July 21, 2009; Published April 08, 2010; Online April 08, 2010

Experimental measurements have been taken on a production four-cylinder, multipoint (fuel) injection spark-ignition engine, 1.2dm3 displacement with a four-valve per cylinder aluminum head, and a 60 kW at 5500 rpm rated power. The aim of the investigation was to understand the behavior of the cooling system of a small automotive engine, which was operated for a prolonged period at high speed under full or part load, then brought to idle for a short period and finally shut down. In this study, the effects of different loads, idle operation time, and lengths of the engine-radiator piping were analyzed. In particular, experimental tests were carried out with the engine running at 4000 rpm under different brake mean effective pressure values in the range 496 to 1133 kPa. In all experimental tests the engine was brought to idle in 5 s, and measurements were repeated for different values of the idle operation time ranging from 1 s to 80 s. Test data of coolant conditions and metal temperature at 26 points of the engine head and liner were recorded. The cooling circuit was instrumented with transparent tubes at the radiator inlet and photographs of the vapor phase moving to the radiator were taken during experimental tests. The volume of leaked coolant as a function of time was also measured. Additional tests were carried out to evaluate the effects of different lengths of the engine-radiator piping on the after-boiling phenomenon. Finally, in order to make the results applicable also to nonautomotive engines, measurements were repeated without the standard cabin heater and the associated piping. The investigation results show that as the engine is shut down and coolant flow stops, the head metal may be hot enough to vaporize a fraction of the coolant contained in the cylinder head passages, causing the pressure within the cooling circuit to rise above the threshold value of the radiator cap pressure valve and, consequently, an important quantity of the coolant to be expelled.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the engine test-bed

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Figure 2

Cylinder head and cylinder block thermocouple locations

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Figure 3

Load and engine speed variation during a “rapid shutdown” test at WOT

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Figure 4

(a) Temperature evolution in the cylinder block and (b) in the engine head. (c) Time history of coolant pressure and temperature at engine outlet. Baseline case: time of idle operation 5 s; initial condition at WOT; standard length of cooling circuit.

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Figure 5

Top, sequence of photographs of coolant flow from engine outlet to radiator inlet taken with transparent piping. Bottom, details of the case in Fig. 4 during the most rapidly varying part of the thermal evolution following a rapid shutdown. (a) Coolant pressure and temperature; (b) head and cylinder block temperature at two representative measuring points. Times of the photographs refer to the time abscissa.

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Figure 6

(a) Temperature evolution in the cylinder block and (b) in the engine head. (c) Time history of coolant pressure and temperature at engine outlet. Prolonged time of idle operation: 80 s; initial load at WOT; standard length of cooling circuit.

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Figure 7

Details of the case in Fig. 6 during the most rapidly varying part of the thermal evolution in the case of a prolonged idle operation. (a) Coolant pressure and temperature; (b) head and cylinder block temperature at two representative measuring points.

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Figure 8

(a) Volume of the spilled coolant and (b) start of coolant leakage after engine shutdown as a function of length of idle operation

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Figure 9

(a) Volume of the spilled coolant and (b) start of coolant leakage after engine shutdown as a function of length of idle operation. Cabin heater removed.

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Figure 10

(a) Coolant and (b) metal conditions at two points in the cylinder head and cylinder block during the most rapidly varying part of the thermal evolution. Time of idle operation 5 s; initial load 819 kPa bmep; standard length of cooling circuit.

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Figure 11

(a) Coolant and (b) metal conditions at two points in the cylinder head and cylinder block during the most rapidly varying part of the thermal evolution. Time of idle operation 5 s; initial load 495 kPa bmep; standard length of cooling circuit.

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Figure 12

(a) Volume of the spilled coolant and (b) start of coolant leakage after engine shutdown as a function of brake mean effective pressure

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Figure 13

Coolant and metal conditions at two points in the cylinder head and cylinder block during the most rapidly varying part of the thermal evolution. Time of idle operation 5 s, initial load at WOT. (a) and (b): increased length of cooling circuit of ≈190 cm; (c) and (d): baseline length of cooling circuit of ≈85 cm; (e) and (f): reduced length of cooling circuit of ≈40 cm.

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Figure 14

(a) Volume of the spilled coolant versus leakage and (b) vapor inlet time inside radiator after engine shutdown as a function of engine/radiator piping length

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