reducing stage STAGE ASSY assy. (1).PPT

NOT APPLICABLE

1. Design of Diffuser(Reducing stage Assy.)
(For Super Heater and Re heater Start up vent silencer in Super Critical
once through Boilers. )
 

2. The main aim of this project is design a reducing
stage assay(we can called a multistage diffuser)
along with study of hydrodynamic parameter like
Beta ratio, Mach number, and numerical
calculation of orifice plate thickness, size of
orifice hole & Bending stress evaluation, reducer
etc.
Abstract:-

3.  When boiler is warming up initially the turbine will be
matched only a specified temperature and pressure.
Till such time the steam produced will be let out to
atmosphere. For this purpose, start up vent is
required. It’s other purpose is for safety valve
floating, that is to check the safety valve set
pressure. This system includes start up line,
regulating and isolating valves, diffuser and silencer,
to abate noise.
Introduction:-

4. The start up steam will be routed through HP turbine
bye pass and LP turbine bye pass valves to
condenser.
Because of not able to ascertain the completion of
erection of HP and LP turbine bye pass lines at the
time start up, startup vents are introduced in OTSC
boilers.
The start-up vent shall be vented to atmosphere.
Usually, the vent will be located at final SH/RH outlet
header or sometimes in M.S. / HRH line. Flow
through the line around 8 to 10% of the total flow
through the MS / HRH line. Based on the parameter
of SH/RH start up vent line shall be designed, the
velocity in start up vent line limited to 100 m/s.
Why start up vent:-

5. In the startup vent line, the
silencer inlet pressure has to be
maintained with in 3 Kg/sq cm.
For the super critical boilers,
the upstream pressure of start
up vent will be at around 81
kg/sq.cm. so for reducing
pressure from 81 kg/cm2 to
3kg/cm2 with constant flow one
diffusers will introduce which
will diffuse the pressure.
Problem identification:-

6. The Beta ratio ( Ratio of orifice hole diameter to
Orifice plate Diameter)is kept around 0.4. The
reference is taken from NASA design for rocket
propulsion applications.
The holes in the orifice plates are bigger when
compared to existing design.
Number of holes in orifice plates will be less.
Better pressure reduction.
Reduced noise generation.
Literature review:-

7. Methodology flow chart
STARSTAR
TT
Literature Review
Abstract
Problem identification
Design criteria
Material details
Experimental details
Design of
reducer ( Beta
ratio)
Design of orifice
plate(thickness
calculation, bending
calculation
Mach number
validation

8.  
Pressure to be drop from 80kg/cm2 to 3 kg/cm2 with
constant steam flow(40t/Hr).
Orifice plate are used for maintain constant flow.
Periodically pressure will drop by reducer(reducing
stage assy.)
The velocity in start up vent line limited to 100 m/s.
Mach number calculated has to be less than 0.4
The Beta ratio ( Ratio of orifice hole diameter to
Orifice plate Diameter)is kept around 0.4.
Design criteria:-

9.  From this design the pressure is achieved from
81kg/cm2 to 3kg/cm2 through 5 reducing stages.
Pressure drop ratio in each stage is 0.5(Assumed)
Each stage has one reducer and orifice plate.
Selection of reducers and orifice plates depends on
requirement and material availability.
Flow parameters are maintained in each stage which
has been showed.
Calculated value of the MACH number comes in
subsonic range in all stages, which means better
noise reduction.
The ratio of orifice plate hole diameter to orifice plate
diameter is kept around 0.4
Design validation:-

10. Diffuse reducing stage assembly:-

11. Reducer:-

12. Orifice plate:-