Design of Intake Manifold

Energy Conversion and Management 51 (2010) 2239–2244

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Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman

Design of a new SI engine intake manifold with variable length plenum M.A. Ceviz , M. Akın *

Department of Mechanical Engineering, Faculty of Engineering, University of Atatürk, Erzurum 25240, Turkey

a r t i c l e

i n f o

Article history: Received 5 August 2009 Accepted 21 March 2010

Keywords: Intake manifold Intake plenum Engine performance performance

a b s t r a c t

This paper investigates the effects of intake plenum length/volume on the performance characteristics of a spark-ignited engine with electronically controlled fuel injectors. Previous work was carried out mainly on the engine with carburetor producing a mixture desirable for combustion and dispatching the mixture to the intake intake manifold. manifold. The more more stringent stringent emission emission legislatio legislations ns have driven engine engine developme development nt towards concepts based on electronic-controlled fuel injection rather than the use of carburetors. In the engine with multipoint fuel injection system using electronically controlled fuel injectors has an intake manifold in which only the air flows and, the fuel is injected onto the intake valve. Since the intake manifolds transport mainly air, the supercharging effects of the variable length intake plenum will be different from carbureted engine. Engine tests have been carried out with the aim of constituting a base study to design a new variable length intake manifold plenum. Engine performance characteristics such as brake torque, brake power, thermal efficiency and specific fuel consumption were taken into consideration to evaluate the effects of the variation in the length of intake plenum. The results showed that the variation in the plenum length causes an improvement on the engine performance characteristics especially on the fuel consumption at high load and low engine speeds which are put forward the system using for urban roads. According to the test results, plenum length must be extended for low engine speeds and shortened as the engine speed increases. A system taking into account the results of the study was developed to adjust the intake plenum length. Ó 2010 Elsevier Ltd. All rights reserved.

1. Introduction

It is known that the design of engine components, measuring and control methodolo methodology gy of the operating operating parameters parameters are very important to improve the engine performance and emission characteristics. Effectively adjusting the operating parameters such as the relative air–fuel ratio, spark timing, fuel injection timing, valve timing, exhaust gas recirculation ratio and compression ratio in SI and CI engines at different engine operation conditions improves significantly the engine characteristics. The effects of such engine operating operating parameters parameters and their control technologi technologies es have been studied excessively by researchers and the product designers. In engines, configuration of the intake system plays also an important role on the engine performance, and there are many experimental and theoretical studies on the intake system and manifold design [1–6].. [1–6] Intake manifolds consist typically of a plenum, to the inlet of which bolts the throttle-body, with the individual runners feeding branches which lead to each cylinder. Important design criteria

*

Corresponding author. Fax: +90 442 236 09 57. E-mail address: [email protected] (M.A. Ceviz).

0196-8904/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.enconman.2010.03.018 doi:10.1016/j.enconman.2010.03.018

are: low air flow resistance; good distribution of air and fuel between cylinders; runner and branch lengths that take advantage of ram and tuning effects; sufficient (but not excessive) heating to ensure adequate fuel vaporization with carbureted or throttlebody injected engines [7] [7].. The intake system on an engine has one main goal, to get as much air–fuel mixture into the cylinder as possible. The intermittent or pulsating nature of the airflow through the intake manifold into each cylinder may develop resonances in the airflow at certain speeds. These may increase the engine performance characteristics at certain engine speeds, but may reduce at other speeds, depending depending on manifold manifold dimensions dimensions and shape. Conventi Conventional onal intake manifolds manifolds for vehicles vehicles have fixed air flow geometry and static intake manifold. With a static intake manifold, the speed at which intake tuning occurs is fixed. A static intake manifold can only be optimized for one specific rpm, so it is beneficial to develop a method to vary the intake length/volume, since the engine operates over a broad speed range. Variable length intake manifold technology uses the pressure variations generated by the pulsating flow due to the periodic piston and valve motion to produce a charging effect. Various designs for variable intake geometry have met with varying degrees of success. The designs of the variable intake manifolds may be rather

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M.A. Ceviz, M. Akın / Energy Conversion and Management 51 (2010) 2239–2244

complex and expensive to produce. Difficulty in servicing and a limited range of variable tuning may also be disadvantageous design results of variable intake manifolds. Studies on the intake manifold design by regulating the runner length/volume for higher engine performance, optimal fuel consumption and lower emissions have significantly increased in the last years. Some of the studies carried out by researchers and engine manufacturers (i.e. Mazda, BMW, Audi) [8–11] change the intake runner length; however, it is known that intake plenum affects seriously the charging conditions [12–14]. Previous work [12] on the effects of intake plenum on some engine performance characteristics was carried out mainly on the carbureted engine. The carburetor produces the fuel and air mixture needed for the operation of the engine and is coupled to the intake manifold which receives the mixture and distributes it to the cylinders. Design of intake plenum is active on the quality of air–fuel mixture homogeneity in carbureted engine. In the engine with multipoint injection systems using electronically controlled fuel injectors has an intake manifold in which only the air flows. The fuel is injected directly into the intake ports and the system delivers a more evenly distributed mixture of air and fuel to each of the engine’s cylinders, which improves power and performance. Engines with multipoint injection have a separate fuel injector located to each cylinder intake port. Such injection systems are ideal for complying with the demands made on the air and fuel mixture formation system. In this paper, the effects of intake plenum length/volume variation on the engine performance were studied experimentally on a spark-ignited engine with multipoint injection systems using electronically controlled fuel injectors. The results were used for the design studies of variable length/volume intake plenum. A new plenum length control system was produced and explained in detail.

6 7 5 3 4 11 1 10

2

9

8 1- Engine

7- Air flow meter

2- Hydraulic dynamometer

8- Muffler

3- Gravimetric fuel flow meter

9- Exhaust gas analyzer

4- Additional plenums

10- Distributor

5- Air surge tank

11- Fuel Injectors

6- Air flow meter probe (hot wire) Fig. 1. A schematic layout of test setup.

Table 1

Engine specifications.

2. Materials and methods

A schematic layout of the test setup used is indicated in Fig. 1. The engine test bed was explained in the previous studies of the author [12,15,16], which consists of a control panel, a hydraulic dynamometer and measurement instruments. The engine specification is summarized in Table 1. The engine performance characteristics through the various points were calculated as follows: the brake power ( P b) delivered by the engine and absorbed by the dynamometer is,

P b ¼ 2pnT 10À3

ð1Þ

where n is the crankshaft rotational speed (rev s À1) and T is the torque (Nm). The thermal efficiency of the engine is, gth

¼

P b Q

ð2Þ

Q is the total heat supplied by the fuel was calculated from,

_ f Q ¼ CV m

ð3Þ

_ f is the fuel consumption (kg sn À1) and CV is the lower calwhere m orific value of the fuel (kJ kg À1). The specific fuel consumption (sfc ) is the fuel flow rate per unit power output and calculated from,

sfc ¼

_ f m P b

ð4Þ

_ f is the fuel consumption (g h À1) and P b is the brake power where m (kW).

Engine type Number of cylinders Compression ratio Bore (mm) Stroke (mm) Displacement volume (dm3) Maximum power Maximum torque Cooling system

Ford MVH-418, fuel injected 4 10:1 80.6 88 1.796 93 kW at 6250 rpm 157 Nm at 4500 rpm Water-cooled

At the beginning of experiments, the engine was run at a near three-quarter opening position of the throttle valve in order to attain near maximum speed. After the engine reached the steadystate conditions, the first experiment was conducted with original intake manifold. The engine was gradually loaded by the hydraulic dynamometer and test matrix consisted of eight speeds ranging from 1500 to 5000 rpm with 500 rpm steps for each plenum addition operation. The experiments were repeated with separately 16 mm (40 cm3), 32 mm (80 cm3), 48 mm (120 cm3) and 64 mm (160 cm3) plenum addition at the same engine speeds that were attained by loading hydraulic dynamometer. The additional plenums had the geometries suitable for entrance of the original intake manifold, and located among the throttle valve and intake manifold plenum. 3. Results and discussion

Figs. 2–5 show the effect of the plenum length on the engine performance characteristics; thermal efficiency, specific fuel consumption, torque and brake power, respectively. It can be seen from Fig. 2 that the highest engine thermal efficiency is observed

2241


0.31

32 mm plenum addition

) - 0.29 ( y c 0.27 n e i c 0.25 i f f E l a 0.23 m r e h 0.21 T

16 mm plenum addition No addition

0.19 0.17 1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

Engine Speed (rpm) Fig. 2. Variation of thermal efficiency with engine speed for three different intake plenum volumes.

) 500 h . W k / g 450 ( n o i t p 400 m u s n o C 350 l e u F c 300 i f i c e p S 250 1000

32 mm plenum addition 16 mm plenum addition No addition

1500

2000

2500

3000

3500

4000

4500

5000

5500

Engine Speed (rpm) Fig. 3. Variation of specific fuel consumption with engine speed for three different intake plenum volumes.

90 80

) m . 70 N ( e 60 u q r o T 50 e k a r 40 B


30 20 1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

Engine Speed (rpm) Fig. 4. Variation of brake torque with engine speed for three different intake plenum volumes.

at 32 mm plenum addition up to 3000 rpm. Improvement in the engine thermal efficiency was especially at lower engine speeds. At the experiments with the original engine manifold, engine thermal efficiency was 27.4%, whereas it increased to 27.9% and 30.9% for 16 mm and 32 mm plenum addition at 1500 rpm, respectively. There was also an increase in the engine thermal efficiency at the experiments carried out by 16 mm plenum addition up to 3000 rpm.

The highest engine thermal efficiency was attained by using 16 mm plenum addition at about the engine speed range of 3000–4000 rpm. As the engine speed increases, the higher engine thermal efficiency was attained at lower length of intake plenum. It is necessary to shorten of intake manifold length as the engine speed increases because of the increase in the flow frequency as discussed in introduction section. The results of this study agreed well with early studies [8–11,17], which were about the effects

2242


22 20

) W16 k ( r e w18 o P e k a r 14 B


12 10 1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

Engine Speed (rpm) Fig. 5. Variation of brake power with engine speed for three different intake plenum volumes.

of intake runner length. At high engine speeds as 4500–5000 rpm, the original engine intake manifold must be used because of the higher thermal efficiency as seen from Fig. 2. It can be concluded from these figures that it is important to use the variable length intake manifold plenum especially on urban and suburban areas (roads) with the frequent stops and acceleration at starting conditions. Fig. 3 presents the specific fuel consumption characteristics with the engine speeds. It can be seen from this figure that the fuel consumption per engine power output was the lowest for the engine speed range of 1500–3000 rpm by using 32 mm plenum addition, and for 3000–4000 rpm range by using 16 mm plenum addition. The higher engine speeds, it is necessary to use the original engine manifold. Figs. 4 and 5 present the engine brake torque and brake power characteristics with different engine speeds. At original engine plenum experiments, the engine brake torque was 80.7 Nm, whereas it increased to 84.2 Nm for 32 mm additional plenum experiments at 1500 rpm. However, there was no significant variation on the engine torque for higher speeds from 2500 rpm. Engine brake torque and brake power are controlled with the fuel injection strategies of the engine electronic control unit by measuring some operating parameters. In this study, the experiments were carried out at the same engine speeds, but at the different load of hydraulic dynamometer. Increase in the plenum length affected the amount of fresh fuel–air charge, and especially at lower speeds, to produce the same level of engine brake power, the engine control unit consumed less fuel because of the low engine load at the same engine

speeds. Consequently, dominant effect was observed on the parameters about the fuel consumption. Figs. 6 and 7 present thermal efficiency, specific fuel consumption characteristics including the effects of much longer length of intake plenum, as 48 mm and 64 mm (120 cm3 and 160 cm3). While the engine performance characteristics improved by using 32 mm additional plenum especially at lower engine speeds, a reverse effect appeared at the experiments carried out by using 48 mm plenum addition, and this effect increased at 64 mm plenum addition conditions for all engine performance characteristics. The experimental studies showed that the variation in the plenum length was not effective on engine exhaust emissions. However, the decrease in the fuel consumption per engine power output decreases the total production of harmful exhaust emissions. The original intake manifold and its plenum of the engine used in the experimental studies were designed for high power output at high engine speed. Therefore, using the extended plenum was useful for lower engine speeds. However, it can be concluded that the results will be different for a new designed intake manifold, especially with a shorter length of intake plenum. Fig. 8 illustrates a general views of the designed intake manifold assembly which communicates the throttle valve and intake manifold with a movable plenum volume. Design criteria of the produced system were determined by using the results of this study. The throttle valve section moves linearly in response to drive system to define an effective plenum length. Flexible section accommodates the difference in length. The data acquisition card on a personal computer measures continuously the engine speed from

0.31

) - 0.29 ( y c 0.27 n e i c 0.25 i f f E l a 0.23 m r e h 0.21 T

64 mm plenum addition 48 mm plenum addition 32 mm plenum addition 16 mm plenum addition No addition

0.19 0.17 1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

Engine Speed (rpm) Fig. 6. Variation of thermal efficiency with engine speed for five different intake plenum volumes.

2243


) 500 h . W k / g 450 ( n o i t p 400 m u s n o C 350 l e u F c 300 i f i c e p S 250 1000

64 mm plenum addition 48 mm plenum addition 32 mm plenum addition 16 mm plenum addition No addition

1500

2000

2500

3000

3500

4000

4500

5000

5500

Engine Speed (rpm) Fig. 7. Variation of specific fuel consumption with engine speed for five different intake plenum volumes.

A

Plenum

Throttle valve Drive module Flexible section

driven to extend the flexible section to increase the length between plenum and throttle valve. As the engine speed increases, the throttle valve is driven to shorten the flexible section. The system therefore provides a cost effective variable intake manifold plenum which will operate with different types of engines. 4. Conclusions

From the results of this study, the following conclusions can be deduced:

Engine Runner

B Runner Engine Flexible section Throttle valve Drive module

Plenum

1. The intake manifold plenum length/volume is highly effective on engine performance characteristics especially with the fuel consumption parameters for SI engines with multipoint fuel injection system. The engine performance can be improved by using continuously variable intake plenum length. 2. Favorable effects of the variable length intake manifold plenum appeared at high load and low engine speeds. Therefore, variable length intake manifold plenum is useful especially on urban and suburban areas (roads) with the frequent stops and acceleration at starting conditions. 3. It is necessary to determine the length of additional plenum components for another engine and intake system with sensitive experimental studies. Acknowledgement

Engine Runner

C

Fig. 8. (A) Front, (B) top and (C) solid view of intake manifold assembly.

engine shaft encoder. The drive system actuates the throttle valve section based on the engine speed information from data acquisition card. In operation at low speeds, the throttle valve section is

This work has been supported by The Scientific and Technological Research Council of Turkey (TUBITAK, Project No. 107M018). References [1] Benajes J, Reyes E, Galindo J, Peidro J. Predesign model for intake manifolds in internal combustion engines. SAE Paper No: 970055; 1997. [2] Safari M, Ghamari M, Nasiritosi A. Intake manifold optimization by using 3-D CFD analysis. SAE Paper No: 2003-32-0073; 2003. [3] Sung NW, Choi JS, Jeong YI. A study on the flow in the engine intake system. SAE Paper No: 952067; 1995. [4] Tsukakoshi S, Miya H, Miyake M. Development of a plastic intake manifold. SAE Paper No: 930085; 1993. [5] Jawad BA, Hoste JP, Johnson BE. Intake system design for a formula SAE application. SAE Paper No: 2001-01-2553; 2001. [6] Jawad BA, Dragoiu A, Dyar L, Zellner K, Riedel C. Intake design for maximum performance. SAE Paper No: 2003-01-2277; 2003. [7] Heywood JB. Internal combustion engine fundamentals. McGraw-Hill Inc.; 1988. [8] Krömer G, Pölzl HW, Thude M, Leitner P. The new Audi V6 engine. SAE Paper No: 910678; 1991. [9] Narayanaswamy K. Continuously variable intake manifold with intelligent position control. US Patent No: 6983,727; 2006.

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[10] Verkleeren RL. Split plenum manifold with variable runners. US Patent No: 5762,036; 1998. [11] Moroto K. Variable intake air apparatus. US Patent No: 5740,770; 1998. [12] Ceviz MA. Intake plenum volume and its influence on the engine performance, cyclic variability and emissions. Energy Convers Manage 2007;48:961–6. [13] Brady JM. A simple high-efficiency S.I. engine design. SAE Paper No: 2003-010923; 2003. [14] Kondapalli PS. General guidelines for improving burst pressure strength of welded nylon air intake manifolds. SAE Paper No 2000-01-0040; 2000.

[15] Ceviz MA, Yüksel F. Effects of ethanol-unleaded gasoline blends on cyclic variability and emissions in an SI engine. Appl Therm Eng 2005;25(5– 6):917–25. _ Temperature and air–fuel ratio dependent specific heat [16] Ceviz MA, Kaymaz I. ratio functions for lean burned and unburned mixture. Energy Convers Manage 2005;46:2387–404. [17] Vitek O, Polaesk M. Tuned manifold systems-application of 1-D pipe model. SAE Paper No: 2002-01-0004; 2002.

Design of Intake Manifold

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