A study and analysis on hcci engine's inlet valve

INTERNATIONAL JOURNAL OF Issue 3, Sep- Dec (2012) © IAEME 0976 –
International Journal of Mechanical Engineering and Technology (IJMET), ISSN
6340(Print), ISSN 0976 – 6359(Online) Volume 3,
MECHANICAL ENGINEERING
AND TECHNOLOGY (IJMET)

ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online) IJMET
Volume 3, Issue 3, September - December (2012), pp.545-554
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Journal Impact Factor (2012): 3.8071 (Calculated by GISI)
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A STUDY AND ANALYSIS ON HCCI ENGINE'S INLET VALVE

Chitthaarth.M.R (1), Charles DhonyNaveen.I.A (2), Sunil Kumar.G (3),Dr.K.Manivannan(4)
School of mechanical and building science, VIT university, Vellore-632014, TamilNadu,
India.
Chitthaarth.m.r@gmail.com: +919677915050

ABSTRACT

The paper deals with the redesigning of the typical inlet valve in the HCCI**engine ,
which involves innovative designing and new material composition. We have done the
analysis of this redesigned inlet valve using advanced CAD packages and the results proves
the improvement in overall performance of the component, its working life and its capacity
of efficient thermal conductivity.

KEYWORDS: Inlet valve, HCCI engine
**Homogeneous charge compression ignition engine

INTRODUCTION:

At present everyone needs their automotive is to be fuel efficient and exit
lessemission now. This has led to the surface of an old idea as a new one. HCCI
(homogeneous charged compression ignition). Earlier this technology had lot of hindrance
but now with advance sophisticated computer improvement this has been made possible and
the problem solved for the betterment of the world. So HCCI as stated above its acronym
means homogeneous charged compression ignition. It’s the combination of both
conventional spark-ignition and diesel compression ignition technology. The engine has a
high compression ratio than the other two types of engines. As the HCCI engine is concept
engine, we have selected the inlet valve component as our study and analysis. We have views
in the component hopping to develop the existing material composition and some design
factors which could help in increasing the efficiency and the performance of the engine, and
also the component’s life. So through this study, we brought a brief explanation of the
development of the inlet valve, which could be more efficient and have a better life time by
reducing the wear and tear in the valve contacting surface.

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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME

LITERATURE SURVEY:

The Homogeneous Charge Compression Ignition (HCCI) engine has attracted much interest
in recent years because it can simultaneously achieve high efficiency and low emissions. However, it
is difficult to control the ignition timing with this type of engine because it has no physical ignition
mechanism. Varying the amount of fuel supplied changes the operating load and the ignition timing
also changes simultaneously. The HCCI combustion process also has the problem that combustion
proceeds too rapidly. This study examined the possibility of separating ignition timing control and
load control using an HCCI engine that was operated on blended test fuels of dimethyl ether (DME)
and methane, which have vastly different ignition characteristics. The influence of the mixing ratios
of these two test fuels on the rapidity of combustion was also investigated. Moreover, as a basic
research subject, the behaviour of formaldehyde (HCHO), an intermediate that is produced by cool
flame reactions, was observed by spectroscopic techniques. The experimental results revealed that,
within the range of the experimental conditions used in this study, the quantity of DME supplied
substantially influenced the ignition timing, whereas it was little affected by the quantity of methane
supplied. This indicates that the ignition timing can be controlled by the quantity of DME supplied
and that the load can be adjusted by the quantity of methane supplied. Spectroscopic measurements of
the behaviour of a substance corresponding to HCHO also indicated that the quantity of DME
supplied significantly influenced the cool flame. [1]

We propose a model based control strategy to adapt the injection Settings according to the air
path dynamics on a Diesel HCCI Engine. This approach complements existing air path and fuel path
controllers, and aims at accurately controlling the start of combustion. For that purpose, start of
injection is adjusted based on a Knock Integral Model and intake manifold conditions .Experimental
results are presented, which stress the relevance of the approach. [2]

Homogenous-charge-compression-ignition (HCCI) engines have the benefit of high
efficiency with low emissions of NO and particulates. These benefits are due to the autoignition
process of the dilute mixture of fuel and air during compression. However, because there is no direct-
ignition trigger, control of ignition is inherently more difficult than in standard internal combustion
engines. This difficulty necessitates that a feedback controller be used to keep the engine at a desired
(efficient) setpoint in the face of disturbances. Because of the nonlinear autoignition process, the
sensitivity of ignition changes with the operating point. Thus, gain scheduling is required to cover the
entire operating range of the engine. Controller tuning can therefore be a time-intensive process. With
the goal of reducing the time to tune the controller, we use extremum seeking (ES) to tune the
parameters of various forms of combustion-timing controllers. In addition, in this paper, we
demonstrate how ES can be used for the determination of an optimal combustion-timing setpoint on
an experimental HCCI engine. The use of ES has the benefit of achieving both optimal setpoint (for
maximizing the engine efficiency) and controller-parameter tuning tasks quickly.[3]

In the limit of homogeneous reactants and adiabatic combustion, ignition timing and pollutant
emissions in homogeneous-charge compression-ignition (HCCI) engines would be governed solely by
chemical kinetics. As one moves away from this idealization, turbulence and turbulence/chemistry
interactions (TCI) play increasingly important roles. Here the influence of TCI on autoignition and
emissions of CO and unburned hydrocarbon (UHC) is examined using a three-dimensional time-
dependent computational fluid dynamics (CFD) model that includes detailed chemical kinetics. TCI is
accounted for using a hybrid probability density function (PDF) method. Variations in global
equivalence ratio, wall temperature, swirl level, degree of mixture inhomogeneity (premixed versus
direct injection, and start of-injection timing for direct-injection cases), and a top-ring-land
crevice (TRLC) are investigated. In addition to providing new insight into HCCI combustion
processes, this work also demonstrates the feasibility of bringing transported PDF methods to
bear in modeling a geometrically complex three dimensional time-dependent turbulent
combustion system. [4]

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ABOUT THE HCCI ENGINE:

HCCI (Homogeneous charge compression ignition engine) engine is a hybrid engine
which works the compression ignition method. The working of the SI engine is that the air
fuel mixture is sent into the engine and the ignition is done using the spark plug. Thus in the
CI engine the air sent in separately and the fuel is been injected during the compression
stroke and the ignition takes place by the compression process. The method used in the HCCI
engine is that the air fuel mixture is sent inside the combustion chamber and during the
compression stroke the mixture reaches the auto ignition point, it is that the combustion takes
place without any ignition system.

HCCI is an alternative engine which works on the high compression process. It gives
high efficiencies as the CI engines, it operates on the principle of the premixed fuel is burnt
with high volumetric compression achieved by the piston. It has the features of the both the
SI and CI engine. The difference in the engine is been shown in the figure. In the fuel mixture
is well mixed in the compression process, which leads to low emission and no throttle loss
which leads to high working efficiency.

Figure 1.Showsthe differenceof the diesel engine, gasoline engine, HCCI engine.

However, it is same like the other engine at present, the combustion occurs for the
complete fuel mixture rather than first in the hot spot. The main advantage is that HCCI is
that combustion takes place at very low temperature which will reduce the emission of the
toxic gases. The HCCI in date has the dual mode of operation, for the initial cold start the SI
type working is been used, then in running it is been shifted to the HCCI mode. This HCCI
mode is used for the ideal running and the mid-load operation, for high load condition it is
again shifted to the normal SI mode this is achieved by using computer control in cars.

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Considering the environmental restriction and the pollution standards for the HCCI
engine, it has very low pollution rates. It is because that the fuel get well mixed and fully
burnt in the power stroke, its operation is similar to the diesel engine working. The pressure is
very high when the stoichiometric or rich mixture is used. The figure shows the pressure
readings of the SI and HCCI engines. The HCCI auto ignition is achieved with the lean fuel
mixture, comparably lesser than the SI engine. There should be an obvious that there is no
explicit timing for the HCCI engine combustion.

CHALLENGES FACED IN HCCI ENGINES:

HCCI operation is achieved by controlling the process temperature and air fuel
mixture composition so that the auto ignition is achieved in TDC . achieving this is very
difficult than using some spark plugs for ignition. This is the only engine which uses the full
electronic engine controls for achieving a good combustion in the HCCI engine. Some of the
technical barriers must be overcome before it is production, The factors mention below.

1. IGNITION TIMING:
Controlling the speed and load of the HCCI engine in various conditions is the
difficulty faced at present. The combustion or the ignition in the HCCI engine fully depends
on the charge mixture composition, the temperature present and pressure.The out ratio of the
HCCI engine varies according to the input of the fuel mixture ratio. For proper combustion
timing the temperature plays a major role, several methods were proposed to meet the various
load and the speed factors. By using the EGR unit the inlet temperature is been maintained, to
achieve a constant inlet temperature andusing a VCR mechanism to alter TDC temperatures,
to obtain a better compression ratio VVT technology is used.

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2. OPERATING RANGES

We know that the HCCI engines operates at low and medium loads, it is difficult to
make it operate at high load conditions. It leads to more noise and causing more emission
problems, and engine damage. Thus some experiments prove that it can be achieved by
increase the partially stratifying the charge at high load operating conditions. More no of
equipment’s are available for achieving the partially stratifying the charge to be achieved at
high load conditions.

3. COLD-START:

In the cold start the compressed gas will be cooled due to the cold temperature in the
cylinder walls. The compressed gas must having the normal temperature for the firing process
and some ideas must be implemented for maintain the temperature. Considering cold starting
various process have been carried out, the solution is that starting the engine in SI mode and
warming up it and again changing it to HCCI mode. Using the VVT, we can reduce the
warming up cycles and time.

4. ENGINE EMISSIONS:

HCCI engines have low emissions of NOx, but have high emissions of HC
(hydrocarbons) andCO(carbon monoxide). Mostly controlling HC and CO emissions for
HCCI engines will require the exhaust emission control devices. Catalyst technology for HC
and CO removal is the popular device used in automobiles for many years. The low temp
exhaust gas which enters the catalyst will reduce the performance of the device. Considering
the factor the catalyst must be developed for low temperature to meet its purpose.

STUDY ON INLET VALVE:

In present days we are comfortable with high performance and maintenance free
vehicle. This fact lead to usage of more advanced material composition to achieve, a better
advantage than the exiting one and having a best design structure for each and every
component in the engine which leads to best performance. In thisstudy we have study and
analysis of the inlet valve in the HCCI engine. The inlet valve plays a major role in having
the required quantity of mixture for the combustion process. It has arapid cooling during the
suction of the air inside of the combustion chamber, and rapid heating during the power
stroke. This factor is considered as the major problem in the inlet valve for all the engine, so
we considered in having a good and better solution for such factor and observing the present
valve material composition and the design of it, through this we have come across the fact
that we can control the rapid cooling and rapid heating by making some changes in the design
and in the material composition. Through this changes we can achieve the required
conditions.

We absorbed that the nickel chromium alloy and the silicon chromium alloy are
majorly used as the valve material. In our study we have selectedthe titanium alloy as a valve
material and decided to analysis its material composition and analysing the temperature flow
in the material. To improve the material strength and the material conductivity,
wearimplementing the titanium alloy for its lighter weight and more efficient in high
temperatures. Also we have planned to maintain a constant temperature in the valve the

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sodium liquid metal is filled inside for this higher performance valve. It is very efficient in
transferring the heat from one place to another.The titanium alloy has the maximum temp of
1700o c this melting point is 200oc above the steel. Titanium very light weight compared to
steel and other alloys. It has the tensile of 210-1380 mpa, this is the strength which is been
equivalent to the steel alloys. The ductile strength of titanium is 56% greater than steel. It has
low thermal conductivity so it has high dissipation of heat from the component and it has
better life.

DESIGN PARAMAMETERS

Overall length of the valve: 110 mm
Diameter of the stem: 8 mm
Diameter of the head: 300mm
Diameter of the seat: 250mm
Seat angle: 45o
Head diameter: 300 mm
Ground length: 850mm
Height of head rim: 1mm
Stepped stem end length: 20mm
Tip chamfer: 1mm
Height of the seat: 2mm
Overall thickness of the head: 10mm

The material of the present valve is nickel chromium and we have upgraded to titanium alloy,
and the detail analysis is explained below.

Design models

Fig. a: This the prototype model of the valve assembly in the engine head, which consists of the timing gear, cam shaft,
valve guide, springs.

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Fig. b: the actual valve designed in PRO-E

Fig. C: the new designed valve using PRO-E

Fig.d: the new designed valve with the hollow path inside

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Here is the design of the valve the existing design (fig.c) and the change of the design(fig.d),
which has the hollow hole in the centre of the valve in where the sodium liquid metal is filled to
maintain the constant temperature and below is the analysed results fig.

Fig.1 this is the designed valve pressure analysis Fig.2 this is the actual valve pressure analysis

Fig.3temperature analysis in designed valve Fig.4 temperature analysis in the actual valve

DESIGN STEPS:
• First we have to develop the model after the design parameters using the cad package,
PRO-E is our working CAD package for using work
• For importing the file to the ANSYS for analysing, we have to change the pro-e format to
PARASOLID.
• Now open the ANSYS and go to files, import, Para.
• The design will appear in the ANSYS window, check model for any data losses.
• Goto preferences and select the structural.
• Goto post processor –element type-add-solid-brick 185
• Goto material- prop-material model-structural-linerar-elastic-isentropic, then enter the values.
• Goto meshing-size cntrl-manual size-global-size,enter the values.
• Goto mesh-mesh-pick all-ok.
• All the areas of the object will be meshed with respect to the entered value
• Goto loads-define loads-apply-structural-areas, and select the areas to be defined.
• Then loads-define loads-apply-pressure-areas, and select the areas in which the pressure acts.
• Goto solutions-solve-current LS-solution done.
• Goto general postprocessor-plot results-condor plot-nodal solution, you will get the deformed
results.
• Goto read results-condor plot-nodal solution, you will get the results for the deformed
solutions.

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DISCUSSION AND RESULTS

Through the analysis and the results we arrived that the new material composition and the
design parameters has more efficiency and high strength, then the exiting one. The results are
shown below.

Theresult for the actual valve pressure analysis
MAXIMUM ABSOLUTE VALUES
NODE 1526 2941 1519 2941
VALUE -0.12585E-04 0.60067E-04 0.13121E-04 0.60071E-04

Through this table, we found that the maximum deflection acting is 0. 60071E-04 at the mid
face of the valve at node 2941 and the minimum value is -0.12585E-04 at the node 1526. It is
absorbed that the pressure is acting at a moderate rate of 0.13121E-04 this leads to worn out
of the material soon.

The result for the designed valve pressure analysis
MAXIMUM ABSOLUTE VALUES
NODE 21 42 23 42
VALUE 0.12470E-04 0.55310E-04-0.12278E-04 0.55394E-0

Through this table, we found that the maximum deflection acting is 0.5539E-04 at the mid
face of the valve at node 42 and the minimum value is 0.12470E-04 at the node 21. It is
absorbed that the pressure acting on the material of the valve is comparatively low than the
pressure acting on the actual valve design.

The result for the (existing) actual valve temperature analysis
MAXIMUM ABSOLUTE
VALUES
NODE 5950
VALUE 1280.0

Through this table, we found that the maximum temp acting on the node 5950 at a temp of
1280, and it has a moderate temperature flow throughout the valve. This leads to a fast
cracking in the material, and elongation.

The result for the designed valve temperature analysis
MAXIMUM ABSOLUTE
VALUES
NODE 1
VALUE 1280.0

Through this table, we found that the maximum temp acting on the node 1 at a temp of 1280,
and it has a less temperature flow throughout the valve compared to the existing valve design.
This result compared to the above temp analysis gives a better material life of the component.

By comparing all the results we can conclude that our new design and the new material
composition gives best result than the exiting one.

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REFERCENCES:

1. [1] Analysis of the Combustion Characteristics of a HCCI Engine Operating on DME and
Methane Yujiro TSUTSUMI, Katsuhiro HOSHINA, Akira IIJIMA, Hideo SHOJI Nihon
University Graduate School, Nihon University
2. [2] Active Combustion Control of Diesel HCCI Engine: CombustionTiming M. Hillion, J.
Chauvin and O. Grondin IFP, France.N. PetitEcole des Mines de Paris, France
3. [3] HCCI Engine Combustion-Timing Control: Optimizing Gains and Fuel Consumption
Via Extremum Seeking Nick J. Killingsworth, Member, IEEE, Salvador M. Aceves, Daniel
L. Flowers, Francisco Espinosa-Loza, and MiroslavKrstic´, Fellow, IEEE
4. [4] A PDF Method for Multidimensional Modeling of HCCI Engine Combustion: Effects
of Turbulence/Chemistry Interactions on Ignition Timing and Emissions Y.Z. Zhang, E.H.
Kung, and D.C. Haworth Department of Mechanical & Nuclear Engineering, The
Pennsylvania State University, University Park, PA, USA
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A study and analysis on hcci engine's inlet valve

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