Design and Analysis of Screw Shaft Engine

DESIGN AND ANALYSIS OF SCREW SHAFT ENGINE

ABSTRACT

This paper presents the development and design considerations of a helical

screw internal combustion engine.

A rotary internal combustion engine including a rotary screw compressor for

receiving and compressing a mixture of air and fuel, a rotary positive displacement

pump for receiving the compressed air and fuel mixture from the rotary screw

compressor and pumping the mixture of compressed air and fuel there through, the

pump having igniting means for igniting the mixture of compressed air and fuel

inside of the pump, and a rotary screw expander for receiving the ignited mixture

of compressed air and fuel and for expanding the volume of the ignited mixture of

air and fuel there through.

Computational Fluid Dynamics (CFD) has been playing an important role in

evaluating and designing various screw machines. Although immense

improvements are achieved in applying CFD procedures for flow prediction and

analysis of screw machines.

CHAPTER 2

INTRODUCTION

This was done simultaneously by Smith in England, and by Ericsson in the

United States.

Both were men of great ability. Each considered himself to be inventor of

the screw propeller. Each took out patents in England, in 1836, and in the United

States, two or three years afterwards. Each patent differed radically from the other;

neither patent, for the general application of the screw propeller, was sustained,

either here or abroad; and neither Smith nor Ericsson patented additional

improvements on the screw propeller.

Each built small screw vessels, in England, that were successfully tried in

1837; Smith's being of six tons burthen, with a wooden screw, driven by a six

horse-power engine, and Ericsson's, named the "Francis B. Ogden," having about

double the tonnage and power.

Each built larger screw vessels that were successfully tried in England in

1839. Smith's vessel, the "Archimedes," being upwards of 200 tons burthen, and

driven by engines designed by Rennie, of 90 horse-power, circumnavigated the

island of Great Britain in May, 1840. Ericsson's vessel, the "Robert F. Stockton,"

smaller, and with less power, was tried in England under steam, and then, in April,

1839, crossed the Atlantic under sail.

Each introduced the screw propeller on merchant vessels in 1840.

Each introduced the screw propeller on war vessels in 1843. Ericsson, on the

"Princeton," and Smith, on the "Rattler."

Both were materially assisted in the introduction of the screw propeller into

use, by the improvements of those who built screw propeller vessels independently

of the patents of either.

The plan of Ericsson's screw propeller on the "Robert F. Stockton" was in

exact accordance with his patent. Smith's plan on the "Archimedes ' varied

essentially from his patent.

Both finally modified their screw propellers, as patented, into the short

screw propellers now in common use.

By the annexed drawing, traced from that of Smith's patent, his screw is

shown with one long blade modeled after the screw of "Archimedes," a screw for

lifting water that differs radically in its action from the screw propeller. The length

of the blade, measured longitudinally on the hub, is shown on his drawing to be

sixteen times greater, in proportion to the diameter of the screw, than that of the

"Rattler," in 1843.

APPLICATION OF A SCREW ROTOR ENGINE AS EXPANSION

DEVICE – BASICS:

The screw engine is a displacement rotary engine which works based on the

Lysholm principle. The Lysholm principle has been economically used in the

1950s for the first time as a screw compressor. The principle is similar to the

workings of piston engines. Both have a closed working chamber, only the one

based on a Lysholm principle changes cyclically instead of oscillating. The

cyclical change thus leads to an in- or decrease of energy content of the fluid in the

chamber. How this process works is further explained in the working principle as

inlet phase, expansion phase and exhaust phase in the section below.

Inlet phase:

A screw engine gets filled with a fluid, which in this concept is R245fa. The

fluid enters the casing through the intake port into a chamber which is formed

between the radial and axial turn edges.

Expanding phase:

During rotation the intake port gets closed. This happens when all radial turn

edges of the working chamber are separated from the intake port. Meanwhile the

volume of the chamber increases, which will cause expansion of the fluid. This

expansion exerts a force on the radical faces, which in turn produces mechanical

energy at the output shaft. During rotation, expansion continues until the fluid will

exhaust.

Exhaust phase:

In this stage the fluid has reached its highest volume and lowest energy

Content. The radial turn edges of the chamber will reach the exhaust port where the

fluid will start to exhaust.

The number of these processes which take place in one rotation depends on

the number of teeth on the male rotor.

CHAPTER 3

CAD/CAE

Computer aided design or CAD has very broad meaning and can be defined

as the use of computers in creation, modification, analysis and optimization of a

design. CAE (Computer Aided Engineering) is referred to computers in

Engineering analysis like stress/strain, heat transfer, flow analysis. CAD/CAE is

said to have more potential to radically increase productivity than any development

since electricity. CAD/CAE builds quality form concept to final product. Instead of

bringing in quality control during the final inspection it helps to develop a process

in which quality is there through the life cycle of the product. CAD/CAE can

eliminate the need for prototypes. But it required prototypes can be used to

confirm rather predict performance and other characteristics. CAD/CAE is

employed in numerous industries like manufacturing, automotive, aerospace,

casting, mold making, plastic, electronics and other general-purpose industries.

CAD/CAE systems can be broadly divided into low end, mid end and high-end

systems.

Low-end systems are those systems which do only 2D modeling and with

only little 3D modeling capabilities. According to industry static’s 70-80% of all

mechanical designers still uses 2D CAD applications. This may be mainly due to

the high cost of high-end systems and a lack of expertise.

Mid-end systems are actually similar high-end systems with all their design

capabilities with the difference that they are offered at much lower prices. 3D sold

modeling on the PC is burgeoning because of many reasons like affordable and

powerful hardware, strong sound software that offers windows case of use

shortened design and production cycles and smooth integration with downstream

application. More and more designers and engineers are shifting to mid end

system

High-end CAD/CAE software’s are for the complete modeling, analysis and

manufacturing of products. High-end systems can be visualized as the brain of

concurrent engineering. The design and development of products, which took years

in the passed to complete, is now made in days with the help of high-end

CAD/CAE systems and concurrent engineering

MODELING:

Model is a Representation of an object, a system, or an idea in some form

other than that of the entity itself. Modeling is the process of producing a model; a

model is a representation of the construction and working of some system of

interest. A model is similar to but simpler than the system it represents. One

purpose of a model is to enable the analyst to predict the effect of changes to the

system. On the one hand, a model should be a close approximation to the real

system and incorporate most of its salient features. On the other hand, it should not

be so complex that it is impossible to understand and experiment with it. A good

model is a judicious tradeoff between realism and simplicity. Simulation

practitioners recommend increasing the complexity of a model iteratively. An

important issue in modeling is model validity. Model validation techniques include

simulating the model under known input conditions and comparing model output

with system output. Generally, a model intended for a simulation study is a

mathematical model developed with the help of simulation software.

Software for modeling:

Solid works

Creo

CATIA

Unigraphics, etc

CREO:

Creo Elements/Pro (formerly Pro/ENGINEER), PTC's parametric, integrated

3D CAD/CAM/CAE solution, is used by discrete manufacturers for mechanical

engineering, design and manufacturing.

Created by Dr. Samuel P. Geisberg in the mid-1980s, Pro/ENGINEER was

the industry's first successful rule-based constraint (sometimes called "parametric"

or "variational") 3D CAD modeling system.The parametric modeling approach

uses parameters, dimensions, features, and relationships to capture intended

product behavior and create a recipe which enables design automation and the

optimization of design and product development processes. This design approach

is used by companies whose product strategy is family-based or platform-driven,

where a prescriptive design strategy is fundamental to the success of the design

process by embedding engineering constraints and relationships to quickly

optimize the design, or where the resulting geometry may be complex or based

upon equations. Creo Elements/Pro provides a complete set of design, analysis and

manufacturing capabilities on one, integral, scalable platform. These required

capabilities include Solid Modeling, Surfacing, Rendering, Data Interoperability,

Routed Systems Design, Simulation, Tolerance Analysis, and NC and Tooling

Design.

Like any software it is continually being developed to include new

functionality. The details below aim to outline the scope of capabilities to give an

overview rather than giving specific details on the individual functionality of the

product.

Creo Elements/Pro is a software application within the CAD/CAM/CAE

category, along with other similar products currently on the market.

Creo Elements/Pro is a parametric, feature-based modeling architecture

incorporated into a single database philosophy with advanced rule-based design

capabilities. It provides in-depth control of complex geometry, as exemplified by

the trajpar parameter. The capabilities of the product can be split into the three

main headings of Engineering Design, Analysis and Manufacturing.

Engineering Design

Creo Elements/Pro offers a range of tools to enable the generation of a

complete digital representation of the product being designed. In addition to the

general geometry tools there is also the ability to generate geometry of other

integrated design disciplines such as industrial and standard pipe work and

complete wiring definitions. Tools are also available to support collaborative

development.

A number of concept design tools that provide up-front Industrial Design

concepts can then be used in the downstream process of engineering the product.

These range from conceptual Industrial design sketches, reverse engineering with

point cloud data and comprehensive free-form surface tools

]

Front Cutaway View

ANSYS:

ANSYS is the usually preferred analysis software package because of its

functionality. In this interface, you can apply forces, pressures, torques, etc on the

models and see how the stresses develop.

The ANSYS Workbench platform is the framework upon which the

industry’s broadest and deepest suite of advanced engineering simulation

technology is built. An innovative project schematic view ties together the entire

simulation process, guiding the user through even complex multi physics analyses

with drag-and-drop simplicity. With bi-directional CAD connectivity, an

automated project level update mechanism, pervasive parameter management and

integrated optimization tools, the ANSYS Workbench Platform delivers

unprecedented productivity, enabling simulation driven product development.

If you are good at FEM, you can implement your own mesh generation

techniques (otherwise, ansys will generate the mesh for you; all u have to do is to

apply to conditions over the geometrical model heat sources, forces, etc...)There

are many modules in workbench... static structural analysis, modal analysis

(vibration analysis), thermal analysis etc... If you are interested in this, it won’t

take too long to learn (unlike ansys multi physics), thanks to the modern, user

friendly interface it depends., usually mechanical, civil, aeronautical engineers use

this package. Whether it is good or not depends on your research/work interests.

But whatever it is always remember: anyone can learn ANSYS workbench and use

it to analyze structures! It’s not at all a big deal always remembered to study the

FEA theory very well before you start to use ansys. the reason is that in many real

case scenarios, the ansys always gives some result or the other (never 100%

accurate) and its generally impossible to find out how correct/incorrect the results

are.... but FEA engineers know how to mesh their models and how to configure the

solver in order to get accurate results most of the time! Hence always understand

the FEM before blindly doing the analysis on ansys, it'll help u better interpret the

results..

FINITE ELEMENT ANALYSIS

Introduction of FEA:

It is not possible to obtain Analytical solution for many engineering

problems. At the engineering solution is a mathematical model or expression that

gives the value of the field variable at any location in the body.

For problems involving complex shapes, material properties and

complicated boundary conditions it is difficult, so for many of the practical

problems, and engineer uses numerical methods to solve the problems and that

provides approximate solutions which is also acceptable one. The three methods

are used.

Functional approximation

Functional difference method

Finite element method

FEA and FEM are two of the very popular engineering applications

offered by existing CAD/CAM systems. This is attributed to the fact that the FEM

is perhaps the most popular numerical technique for solving engineering problems.

The method is general enough to handle any complex shape or geometry, any

material properties, any boundary conditions and any loading conditions. The

generality of the FEA method analysis

Requirements to today’s complex engineering systems and designs were

closed form solutions of governing equilibrium equations are generally not

available. In addition, it is an efficient design tool by designers can parametric

design studies by considering various design cases analyzing them and choosing

the optimum design.

The FEM is numerical technique for obtaining approximate solutions

to engineering problems this method is adopted in the industry as a tool to study

stresses in complex air frame structures. The method has gained popularity aimed

of both researches and practioners.

General procedure of the FEA:

The solution of a continuum problem by the finite element

method usually follows an orderly step-by- step processes. The following steps

show in general how the finite element methods.

Discredited the given continuum

Select the solution approximation

Develop element matrices and equations

Assembling the element equations

Solve for the unknown at the nodes

Interpret the results

Modeling Capabilities of Finite Element Software:

There are several such software package available today which

can run on main frame, mini computers as 16 and 32 bit PC, I-DEAS, NASTRAN,

PATRAN, ANSYS, COSMOS, etc.., are some of the well known analysis

packages.

The following list gives the some of the capabilities of finite element

software packages.

TYPES OF ANALYSIS DETERMINATION

Static Stresses and displacement

Dynamic Transient and steady state response

model Natural frequencies, mode shapes

Random Vibration and force vibration problems

Stability Buckling loads on a structure

Heat transferTemperature distribution, heat flow under steady state

transient conditions

fieldFields intensity, flux density of magnetic field, field

problems in a acoustics and fluid mechanics

CouplingDisplacement forces, temperature heat flows, fluid

pressure & velocity

STEPS IN FEA

Definitions of the problem and its domain.

Discretisation of the domain the continuum.

Identification of state variable.

Formulation of the problem.

Establishing coordinate system.

Constructing approximate functions for the elements.

Obtaining element matrix and equation.

Coordinate transformation.

Assembly of element equations.

Introduction of the final set of simultaneous equation.

Interpretations of the results.

BASIC COMPONENTS OF FEA

Pre-processor

Solution

Post processor

General post processor

ADVANTAGES OF FEA

Applicable to any field problem such as heal transfer stress analysis,

magnetic field etc.

There is no matrix restriction.

Approximately it is easily improved by grading the mesh so that more

elements appear where field gradients are high and more resolution is

required.

Compounds that have different behavior and different mathematical

description can be solved.

FEA structure closely resembles closely the actual body or region to be

analyzed.

USES OF FEA

Structural analysis

Heat transfer analysis

Fluid flow analysis

Mass transport

CHAPTER 4

COMPUTATIONAL FLUID DYNAMICS

INTRODUCTION:

A way to have a good working definition of what CFD is to break down the

word. “CFD is the acronym of Computational Fluid Dynamics. Computational

means having to do with mathematics, computation and Fluid Dynamics refers to

the dynamics of things that flow.”

So, CFD is a computational technology that enables you to study things that

flow. CFD not only predicts fluid flow behavior, but also the transfer of heat, mass,

phase change, chemical reaction, mechanical movement and stress or deformation

of related solid structures.

Computational Fluid Dynamics or simply CFD is concerned with obtaining

numerical solution to fluid flow problems by using computers. The advent of high-

speed and large-memory computers has enabled CFD to obtain solutions to many

flow problems including those that are compressible or incompressible, laminar or

turbulent, chemically reacting or non-reacting. Computational Fluid Dynamics

(CFD) is the science of predicting fluid flow, heat transfer, mass transfer, chemical

reactions, and related phenomena by solving the mathematical equations which

govern these processes using computational methods.

CFD is the art of replacing the differential equation governing the Fluid

Flow, with a set of algebraic equations (the process is called discretization), which

in turn can be solved with the aid of a digital computer to get an approximate

solution. The well known discretization methods used in CFD are, Finite Volume

Method (FVM), Finite Element Method (FEM), and Boundary Element Method

(BEM).

THE BENEFITS OF CFD:

            Insight: There are many devices and systems that are very difficult to

prototype. Often, CFD analysis shows parts of the system or phenomena happening

within the system that would not otherwise be visible through any other means.

CFD gives a means of visualizing and an enhanced understanding of the various

designs.

          Foresight: Because CFD is a tool for predicting what will happen

under a given set of circumstances, it can answer many ‘what if?’ questions very

quickly. We give it variables. It gives us outcomes. In a short time, we can predict

how the design will perform, and many variations may be tested until you arrive at

an optimal result. All of this is done before physical prototyping and testing. The

foresight we gain from CFD helps us to design better and faster.

Efficiency: Better and faster design or analysis leads to shorter design

cycles. Time and money are saved. Products get to market faster. Equipment

improvements are built and installed with minimal downtime. CFD is a tool for

compressing the design and development cycle.

APPLICATIONS OF CFD:

CFD is interdisciplinary cutting across fields of aerospace, mechanical, civil,

chemical, electrical engineering as well as physics and chemistry. CFD has been

widely used in industry in the past decade. It is certainly fun for fluids enthusiasts,

but where exactly can CFD be applied - the following are areas of applications of

CFD to date.

Automobile and Engine

o Aerodynamics, Engines, Turbochargers, Intake/Exhaust

Heating/Cooling Systems, Brakes etc.

Industrial Manufacturing

o Aerospace, Aerodynamics. Gas Turbines, Rockets etc.

Mechanical

o Pumps, Compressors, Heat Exchangers, Furnaces, Nuclear Reactors

etc.

Chemical

o Mixers (multiphase), Chemical Reactors, Separators, Boilers,

Condensers etc.

Environmental Engineering

o Weather prediction, River and Tidal flows, Wind and Water-borne

pollution, Fire and Smoke spread, Wind loading etc.

Physiological

o Cardiovascular flows (Heart, major vessels), Flow in Lungs and

breathing passages etc.

Naval Architecture

o Ship building etc.

METHODOLOGY& VARIOUS STEPS:

In this work, first of all a generic model of the passenger car is prepared in

the SOLIDWORKS software and this generic model is import into the ANSYS

FLUENT to do the simulation of the coefficient of drag and coefficient of lift in

the wind tunnel which is generated in the design module of the ANSYS FLUENT.

After this the meshing is generated on the surface of the passenger car.

Aerodynamic evaluation of air flow over an object can be performed using

analytical method or CFD approach. On one hand, analytical method of solving air

flow over an object can be done only for simple flows over simple geometries like

laminar flow over a flat plate. If air flow gets complex as in flows over a bluff

body, the flow becomes turbulent and it is impossible to solve Navier- Stokes and

continuity equations analytically. On the other hand, obtaining direct numerical

solution of Navier-stoke equation is not yet possible even with modern day

computers. In order to come up with reasonable solution, a time averaged Navier-

Stokes equation is being used (Reynolds Averaged Navier-Stokes Equations –

RANS equations) together with turbulent models to resolve the issue involving

Reynolds Stress resulting from the time averaging process. In present work the k-e

turbulence model with non-equilibrium wall function is selected to analyze the

flow over the generic passenger car model. This k-e turbulence model is very

robust, having reasonable computational turnaround time, and widely used by the

auto industry.

STEPS OF ANALYSIS:

Select the models of vehicle upon which add on devices are to be used.

Formation of Base Line Model: Designing of model in solid works with

proper dimensions & parameters.

Baseline passenger car CFD method and setup: Apply the boundary

conditions.

Generate the wind tunnel for simulation.

Simulation & Testing of base line passenger car for drag coefficient and lift

coefficient.

Simulation & Testing of passenger car with tail plates for drag coefficient &

lift coefficient.

Impact of add on device on fuel economy of Passenger car.

FORMATION OF BASE LINE MODEL:

The base line model of generic passenger car is designed in Solid Works.

Figure 1 show the generic passenger car used in the present CFD simulation. The

full size generic passenger car is 4389mm long, 1350mm wide, 1375mm high.

Then after, this model has been analyzed for drag coefficient and forces under the

ANSYS-14.0 (FULENT) module and values of drag coefficient lift coefficient

CHAPTER 5

PRINCIPLE OF THE SCREW-TYPE ENGINE TECHNOLOGY:

The screw-type engine is a displacement rotary engine. Similar to piston

engines, displacement-type engines are characterized by a closed working

chamber. The volume of the working chamber changes cyclically, which leads to a

decrease of the energy content of the fluid in the chamber. The main parts of a

screw-type engine are the male rotor, the female rotor and a casing, which together

form a V-shaped working chamber whose volume depends solely on the angle of

rotation. The steam enters the casing through the intake port in the passage formed

between the tips of the rotor teeth. During rotation the volume of the chamber

increases. Intake is finished when the rotor faces pass the guiding edges and the

chamber is separated from the intake port. At this stage steam expansion starts and

mechanical power is produced at the output shaft. During expansion the volume of

the chamber continues to increase, whereas the energy content of the fluid

decreases. This process continues until the exhaust process starts and the steam is

extruded. It leaves the machine through the exhaust port. How often this process

takes place during one rotation of the male rotor depends on the number of teeth on

the male rotor.

The screw-type engine is a very compact machine with a long life time and low

maintenance costs.

CHAPTER 6

SCREW SHAFT ENGINE

Assumptions

1. Combustion Temperature =950 K

2. Combustion Pressure = 14 bar

Geometry Model:

Fluent Mesh

Iteration

Result

Pressure:

Outlet Pressure 8130000 pa

Temperature

Outlet Temperature 960 k

Velocity

Outlet Velocity 820 m/s

CONCLUSION

Outlet Pressure =8130000 pa

Outlet Temperature =960 k

Outlet Velocity =820 m/s

Advantages of the screw-type engine process:

Screw-type steam engines for small-scale biomass CHP applications have a

number of advantages compared to conventional steam turbines and steam engines:

Comparatively high electric efficiency for small-scale CHP units (< 1,000

kWel)

The screw-type engine has a very good partial-load efficiency over a wide

range of load conditions

Load fluctuations between 30 and 100 % of nominal electric power

production are no problem

The screw-type engine is insensitive to steam quality fluctuations. Even

water droplets in steam, which can occur in a simple boiler due to

malfunction or changes of fuel quality, do not cause any problems in screw-

type engines

The steam cycle and the oil cycle are completely separated by an air-lock

system

The fully automatic operation and easy handling saves staff costs

The screw-type engine is a very compact machine and causes low

maintenance costs

Control system and safety equipment:

The screw-type steam engine works in grid connected operation. Plant

operation and start up are controlled fully automatically by an electronic control

system and do not require additional staff.

To make sure that the oil in the bearings and the synchronising gear is

separated from the steam in the working chamber, the labyrinth packing of the

screw-type engine is designed in a way that fluids can be drained or supplied

through various components (seals - connections). To separate the oil section from

the water section, air is injected under slight pressure. Some parts of the seal are

connected in order to make sure that no air can enter the working chamber if there

is a vacuum in the condenser.

CHAPTER 7

CONCLUSION

In this paper, CFD analysis has been done to understand flow disturbance

caused by the screw engine in an internal combustion engine.

A full multivariable optimization of screw expander geometry

and operating conditions has been performed to establish the

most efficient expander design for a given duty.

CHAPTER 8

REFERENCE

Vimmr J, Ondrey F, 2006, Numerical Simulation of Leakage Flow Between

Moving Rotor and Housing of Screw Compressor, Proceedings of the Conference

Modelowanyie Inzynierskie, ISNN 1896-771X, 32, s. 461-468, Gliwice 2006.

Taniguchi, H.; Kudo, K.; Giedt, W. H.; Park, I.; Kumazawa, S.Analytical

and Experimental Investigation of Two-Phase Flow Screw Expanders for Power

Generation. J. Eng. Gas Turbines Power 1988,110, 628–635.

Ng, K. C.; Bong, T. Y.; Lim, T. B. A Thermodynamic Model for the

Analysis of Screw Expander Performance. Heat Recov. Sys. CHP 1990,10, 119–

133.

Winterbone DE, Pearson RJ (2000). Theory of engine manifold design -

Wave action methods for I.C. Engines. Professional Engineering Publishing

Limited, London and Buery St Edmunds, U.K.

Calculating the Trajectories of Triboelectrically charged particles using

Discrete Element Modelling (DEM), M Hogue, C Calle, D Curry, P Weitzman,

ESA 2007 Annual Conference.