THIS DOCUMENT IS PROTECTED BY U.S. COPYRIGHT It may not be reproduced, stored in a retrieval system, distributed or transmitted, in whole or in part, in any form or by any means. Downloaded from SAE International by Brunel University, Copyright 2012 SAE International Saturday, January 21, 2012 01:04:43 PM

SAE TECHNICAL PAPER SERIES

2008-01-0892

An Optimization of Dual Continuously Variable Valve Timing for Reducing Intake Orifice Noise of a SI Engine
Teockhyeong Cho, Youngki Kim, Jaeheon Kim and Koo-tae Kang
Hyundai Motor Company

Reprinted From: Noise and Vibration, 2008 (SP-2158)

2008 World Congress Detroit, Michigan April 14-17, 2008
400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-0790 Web: www.sae.org

THIS DOCUMENT IS PROTECTED BY U.S. COPYRIGHT It may not be reproduced, stored in a retrieval system, distributed or transmitted, in whole or in part, in any form or by any means. Downloaded from SAE International by Brunel University, Copyright 2012 SAE International Saturday, January 21, 2012 01:04:43 PM

By mandate of the Engineering Meetings Board, this paper has been approved for SAE publication upon completion of a peer review process by a minimum of three (3) industry experts under the supervision of the session organizer. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. For permission and licensing requests contact: SAE Permissions 400 Commonwealth Drive Warrendale, PA 15096-0001-USA Email: permissions@sae.org Tel: 724-772-4028 Fax: 724-776-3036

For multiple print copies contact: SAE Customer Service Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-0790 Email: CustomerService@sae.org ISSN 0148-7191 Copyright © 2008 SAE International Positions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE. The author is solely responsible for the content of the paper. A process is available by which discussions will be printed with the paper if it is published in SAE Transactions. Persons wishing to submit papers to be considered for presentation or publication by SAE should send the manuscript or a 300 word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE. Printed in USA

THIS DOCUMENT IS PROTECTED BY U.S. COPYRIGHT It may not be reproduced, stored in a retrieval system, distributed or transmitted, in whole or in part, in any form or by any means. Downloaded from SAE International by Brunel University, Copyright 2012 SAE International Saturday, January 21, 2012 01:04:43 PM

2008-01-0892

An Optimization of Dual Continuously Variable Valve Timing for Reducing Intake Orifice Noise of a SI Engine
Teockhyeong Cho, Youngki Kim, Jaeheon Kim and Koo-tae Kang
Hyundai Motor Company
Copyright © 2008 SAE International

ABSTRACT
For optimizing the performance of SI engine such as engine torque, fuel consumption, and emissions, various types of system for variable valve timing were developed by many automotive researchers. In this paper, we investigated the relationship between valve timing and intake orifice noise, and suggested how to improve NVH (Noise, Vibration and Harshness) performance as well as engine torque. Some experiments using the engine dynamometer were carried over about 150 different operating conditions. BEM analysis was also conducted in order to calculate acoustic modes of intake system. The results show that the valve timing and overlap of breathing systems have influence on NVH behavior, especially intake orifice noise over whole range of operating conditions. Valve timing and overlap of intake and exhaust valve were optimized in the view of sound quality as well as overall noise level. It is concluded that the optimal valve timing strategy is necessary to develop the intake orifice noise according to engines with good sound quality.

purpose of improving sound quality. Present Dual CVVT(Continuously Variable Valve Timing) system focuses on controlling intake and exhaust valve timing which can improve engine performance as well as fuel economy and decrease engine emission. Recently, various valve systems including valve timing and lift control have been developed. These new techniques which lessen pumping loss, NOx and BSFC besides improves engine performance of wide open throttle conditions. However, the relationship between intake orifice noise and Dual CVVT which are relevant to sound quality has not been investigated yet. This paper proposes a novel developing process of intake orifice noise through two approaches: the optimization of intake and exhaust valve timing, the application of results from BEM analysis. Experimental data were collected in correspondence with about 150 different operating conditions of the engine.

1. Experimental method 1.1 Intake orifice noise Test Description

INTRODUCTION
In the view of driving comfort, sound quality becomes more and more important characteristics of vehicle besides conventional performance such as power, torque and fuel consumption. In this sense, various approaches related to sound quality are necessary to develop good cars. There are two noises which have an influence on a vehicle’s noise: Structure-borne noise and air-borne noise. The former is radiated from the induction system. Especially, the latter, intake orifice noise, as an airborne-noise is divided into inlet noise and flow noise. Inlet noise which is generated below 500Hz results from valve movement during the piston movement. The intake orifice noise is one of the important factors which contribute to vehicle interior sound. In this work, the improvement of intake orifice noise through controlling intake and exhaust valve timing at whole range of operating conditions is focused for the Table.1 shows the main specification of new developed V6 gasoline engine which was tested in the experiment. Experiments were conducted by changing variables of intake and exhaust valve timing to control ECU. Measured data were sound pressure 10cm distant from Snorkel, sound pressure 1m distant from engine top, torque of engine dynamometer, and air mass flow rate. Calculated data were engine brake torque and fuel mass flow rate. Experimental data were acquired through PAK DAQ system, using front-end MK-II and B&K 4190 microphone. Figure1 shows the layout of the intake system.

THIS DOCUMENT IS PROTECTED BY U.S. COPYRIGHT It may not be reproduced, stored in a retrieval system, distributed or transmitted, in whole or in part, in any form or by any means. Downloaded from SAE International by Brunel University, Copyright 2012 SAE International Saturday, January 21, 2012 01:04:43 PM

Engine Type Bore X Stroke Compression Ratio Engine Displacement

Gasoline V6 96 X 87 10.4 3.8 Liter

2. Results of Experiment 2.1 Sound Quality Analysis Figure.2 shows intake orifice noise measured at given conditions at 4000 RPM of Table.2 Analysis of sound quality factors of Loudness, Roughness and Sharpness sound quality are shown in figure 3. Black circle indicates the valve timing before optimized, while pink circle does after optimized. Sound quality is significantly considered when optimizing valve timing.

Table1. Engine Specification

0 Intake Valve Advance

o

15

o

30

o

10

o

5

o

0

o

Exhaust Valve Retard

Figure1. Layout of the Intake system Figure2. Intake orifice noise of 4000rpm

1.2 Experimental Conditions Experimental approaches had been conducted from 2000 to 6300rpm that generated a critical range of intake orifice noise. The overlap between advanced intake valve and retarded exhaust valve timing was increased at the wide open throttle conditions. Experimental data were measured approximately 150 different operating conditions of the engine: RPM and valve timing. Table 2 shows the example of valve timing test conditions of 4000rpm in accordance with advanced intake valve timing 0o ~ 30o, and retarded exhaust valve timing 0o ~ 15o which control ECU valve timing map by 5o intervals.

Loudness

Roughness

Sharpness

Figure3. Sound quality factors of 4000rpm

The experimental results at 4000rpm of Figure 3 reveal that optimal valve timing exists.

2.2 Engine Performance Engine performances such as torque and power are prerequisite for developing vehicles with lower noise level and better sound quality. Engine performances are important because they are directly related to the vehicle’s performance. Therefore, it is the pith of this work to improve sound quality of a vehicle without deteriorating engine power. Figure 4. shows engine torque related to valve timing.

Intake Advance
0
Exhaust Retard o 5

o

10

o

15

o

20

o

25

o

30

o

0 5

o o o

10

◎ ◎ ◎

◎ ◎ ◎

◎ ◎ ◎

◎ ◎ ◎

◎ ◎ ◎

◎ ◎ ◎

◎ ◎ ◎

Table2. Valve overlap test conditions of 4000rpm

Noise Level

THIS DOCUMENT IS PROTECTED BY U.S. COPYRIGHT It may not be reproduced, stored in a retrieval system, distributed or transmitted, in whole or in part, in any form or by any means. Downloaded from SAE International by Brunel University, Copyright 2012 SAE International Saturday, January 21, 2012 01:04:43 PM

0 Intake Valve Advance

o

15

o

30

o

10

o

5

o

0

o

Engine torque

Exhaust Valve Retard

Current Map

Optimized Map

Figure4. Engine Torque of 4000rpm

Figure5. Time frequency analysis of 3000rpm and 4000rpm

2.3 Comparison between Current and Optimized map Even though engine performance increased (show the figure7), sound quality of optimized map was improved compare to that of current map. Especially, sound pressure level from 300 to 1000 Hz decreased.

The modification of intake and exhaust valve timing in ECU could find the optimal map each rpm. Table3 reveals differences between current and optimized map of 3000rpm and 4000rpm.

2.4 Experimental Results of Sweep Test 3000rpm
Current Map EVO[ ] IVO[ ] Overlap[ ] o o o

4000rpm
Current Map BBDC X’ BTDC Y’ Z’ Optimized Map BBDC X’-5 BTDC Y’ Z’+5

Optimized Map BBDC X-10 BTDC Y Z+10

The change of valve timing at the 3000rpm and 4000rpm had a positive effect on the intake orifice noise. Therefore, Experimental sweep had fulfilled the optimization of valve timing from 2000 to 6300 rpm. The figure6 shows intake orifice noise of the current and optimized map.
Current Map Optimized Map

BBDC X BTDC Y Z

Table3. Differences between current and optimal map

Figure 5 shows the results of time frequency (wavelet) analysis between current and optimized map,.
3.5dB

2dB

Figure6. Intake orifice noise at the engine run-up

After applying of the optimized map, the intake orifice noise was reduced by the maximum 3.5dB.
Current Map Optimized Map

The precondition of reduction of the intake orifice noise has not to decrease the engine performance. The figure7 shows the engine performance which follows

THIS DOCUMENT IS PROTECTED BY U.S. COPYRIGHT It may not be reproduced, stored in a retrieval system, distributed or transmitted, in whole or in part, in any form or by any means. Downloaded from SAE International by Brunel University, Copyright 2012 SAE International Saturday, January 21, 2012 01:04:43 PM

ECU mapping at the wide throttle open sweeping conditions.
37.5 37 36.5 36 35.5 35 34.5 34 33.5 33

It is the third resonance mode that amplified intake orifice noise from 3000 to 3500rpm. Helmholtz resonator was attached at the place of ③ where sound pressure level was the highest.

Current Map Optimized Map

5. An optimization experiment of intake orifice noise It accomplished the experiment which simultaneously considered valve timing and BEM analysis in order to fulfill the linearity of intake orifice noise.

2000

3000

4000 5000 Engine RPM

6000

Current Map Optimized Map Optimized Map + resonator

Figure7. Diagram of Engine Torque

Analyzing the result of figure7, the engine from conditions under whole acceleration from 2000 to 6300rpm, engine torque between current and optimized valve timing were almost not changed. Consequently, it will be able to improve the sound quality of the intake orifice noise without engine torque decrease. 4. BEM analysis of the Intake orifice noise It obtained the result that Dual CVVT valve timing control is useful in sound quality improvement of the intake orifice noise. Otherwise, Figure 6 reveals that valve timing control was not complete according to linearity of the intake orifice noise. The reason is that intake orifice noise increased by the acoustic resonance in relation to intake orifice noise of from 3000 to 3500rpm. To improve intake orifice noise analysis meshed BEM from intake port to snorkel. Sysnoise was used as an analysis solver. Calculated acoustic transfer function from microphone locations which were identical with an experimental measurement in addition to calculating acoustic modes is shown in Figure 8..
A position of resonator

Current Map

Optimized Map

Optimized Map + resonator

① ② ① ②

③ ④

③

Current Map

Optimized Map

Optimized Map + resonator

④

Figure9. Optimized noise of Intake orifice

Figure8. BEM Analysis of Intake system

THIS DOCUMENT IS PROTECTED BY U.S. COPYRIGHT It may not be reproduced, stored in a retrieval system, distributed or transmitted, in whole or in part, in any form or by any means. Downloaded from SAE International by Brunel University, Copyright 2012 SAE International Saturday, January 21, 2012 01:04:43 PM

Figure 9 reveals that the optimization of valve timing which had a positive effect of sound quality, prominence ratio analysis plays an important role according to the intake orifice noise, and an application of resonator are necessary to improve the sound quality of vehicle and to fulfill the linearity of intake orifice noise.

CONCLUSION
This paper proposed the effective control method of intake orifice noise in addition to sound quality. 1. Valve timing modification led to the reduction of the intake orifice noise, without the decrease of engine performance. 2. The valve timing control method for the purpose of improving sound quality was presented instead of reducing intake orifice noise level. 3. An optimization of valve timing and an application of Helmholtz resonator simultaneously were considered to improve intake orifice noise.

REFERENCES
1. Cho, T. H., Kim, J., and Kang, K. T., “Inlet noise analysis on the automotive intake system of a new gasoline engine”, Acoustical society of Korea Conference, 2003. 2. F.Bozza, A.Gimelli and A.Senator, ‘”A Theoretical Comparison of Various VVA Systems for Performance and Emission Improvements of SI-Engines”, SAE paper 2001-01-0670, 2001. 3. Paulo Zavala, “Experimental Method to Determine the Best NVH Fine Tuning for Air Induction System” , SAE paper 2006-01-2852, 2006. 4. Kim, J., Kang, K.T., and Yeo, S.D., “A Study on Mechanism of Intake Rumble Noise and Optimization of Intake Manifold”, IN01-361, Internoise2001, 2001. 5. Munjal, M. L., Acoustics of Ducts and Mufflers, John Willey & Sons. 1987. 6. Kinsler, L. E., Frey, A.R., Coppense, A.B. and Sanders, J. V., Fundamentals of Acoustics 4th edition, John Willey & Sons, 2000.