Thrust-stand for LTLPRE

7/26/2019 Thrust-stand for LTLPRE

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Innovative Thrust-stand

Low-thrust Liquid-Propel

Pulsed Rocket

Engines(LTLPREs)

Zahir Umme

LS15


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This presentation acquaints the thrust stand developed by the Ke

Precision and Nontraditional Machining Technology (Dalian Universit

PeoplesRepublic of China) for measuring the pulsed thrust from LTL

are widely used for orbit maintenance, attitude control, precision ori

insertion, rendezvous, docking, separation, braking and midcourse co

vehicles.

This presentation is wholly based on the journal paper THRUST STHRUST LIQUID PULSED ROCKET ENGINES Qin Xing, Jun Zhang, Min Qian, Zh

yuan Sun,The Review Of Scientific Instruments September 2010 .


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Introduction

designed to possess a high susceptibility towards the transient nat

from the LTLPREs.

based on a novel piezoelectric thrust dynamometer(TD).

Mainly consists of the following :

1. TD

2. base frame

3. connecting frame

4. Data acquisition system


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possesses an integral static calibration system,which used a standa

dynamic calibration is performed using the pendulum-impact techn

following are some of the important specifications:

>sensitivity: 25.832 mV/N

>linearity error: 0.24% FSO

>repeatability error: 0.23% FSO

>natural frequency (): 1245 Hz

>thrust range: 5-20 N @ 50 Hz pulse


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Necessity for LTLPRE-specific thrust

Conventional displacement-type thrust stand cannot accurately det

pulse forces from the LTLPREs.

Conventional thrust stands, in which the displacement of the flexure joints is detectetransduced to the required format, is incapable of detecting the displacements ocfrequencies.

Based on the principles of harmonics, for measuring such forces th

frequency () of the test-stand should be much more than the pu

thrust forces

Most conventional thrust stands have () in the range of 1-5 Hz and therefore such devicproperly measuring the pulse forced


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For resolving the aforementioned issues,the LTLPRE thrust-stand was

conforming to the following conditions:1.) Non-flexural joint for the force sensors- so that the device has a a

to deal with the transient nature of the force

2.) High to deal with the restrictions related to the harmonics of

forces frequency.


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Structure of the LTLPRE Thrust St

-the following is an illustration of the thrust stand


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Thrust dynamometer(TD)

-is the core part of the TD and consists of an integral shell str

piezoelectric quartz sensors.

-the elastic half-ring grooves are a unique feature ,for accommod

sensors.


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-the two piezoelectric quartz sensors are distributed on the two sides o

-Six y-cut quartz plates with shear piezoelectric effect, three signal elec

four ground electrodes are bonded together by adhesive under a press

above shown schematic.


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-the TD takes the form a shell,with an appreciable degree of elasticity a

that a suitable elastic structure can effectively improve the high-freque

stand.

-the unique shell form adopts integral structure which includes two fix

elastic double-half rings and a worktable.

-In each double-elastic-half-ring grooves, the piezoelectric quartz sensa certain amount of interference.

-the interference is necessary to transmit the static friction forced deve

deformation of the half-ring grooves.


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-the following is the FEA illustration of the TD when subjected to a norm

different deformation on the two sides of each groove will cause static

fitting surface, which are transferred to the piezoelectric quartz senso

measurement of the force.


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Connecting frame

-connects the LTLPRE with the TD.

-designed to provide enough space to install the electromagnetic-valveof the engine.

-the main design constraint is the mass of the structure.

= -------------------------------------(1)

Equation 1 relates the structural stiffness and mass to the natural frequ

have higher ,the structure is made as light as possible, this vindicat

structure of the connecting frame.


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Base frame

-is used to hold the rocket engine with its horizontal axis approximatel

the centerline.

-consists of a box frame supported to rigidly on a flat plate, TD is moun

face of the box.

-the static calibration system is installed on the rear face.

DAS

-consists of the following:

1.) a charge amplifier (Type YE5850B, Sinocera Piezotronics Inc., Ch


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2.) 16 bit high speed analog/digital (A/D converter DT9804, Data Tran

USA)

3.) a computer with the data acquisition software DEWESOFT 6.2 (DAustria).

-charge signal from the thrust dynamometer is sent to the charge amp

amplified voltage signal is fed to the ADC. The ADC output is received b

and are displayed real-time by data acquisition software.


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Static Calibration Systems

-accomplished using an in situ calibration technique

-the system consists of the following components:

1.) hydraulic loading device (typeYS-60 piston pressure meter, Xian

Factory,China).

2.) standard force sensor (type MCL-L, Resolution 0.006 N, Beijing Z

Instruments Co., Ltd., China).3.) a hydraulic cylinder, a piston and a wire rope.

-the in situ system renders the particularly low value of repeatability er


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-the static calibration method is briefly explained below:A series of standard loads(5,10,15 N) are applied on the piston using the hydraulic loading device. T

movement of the piston pulls the front end of the connecting frame through the wire rope. This in

the TD and O/P signal are received. These O/P signals are cross-checked with the readings from th

sensor(has one end connected to the piston while the other end to the wire rope),i.e. the standar

calibration reference.


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Dynamic Calibration

-The purpose of the dynamic calibration is to determine the natural fre

thrust stand. A steel ball attached to a string is conveyed to a certain h

circumferential direction and allowed to accelerate toward the center

model. Thrust response signal from the thrust dynamometer is acquire

to a computer. Fast Fourier transformation analysis from the DEWESO

software is used to obtain amplitude and phase information from the t

profile.


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Thank You!

Thrust-stand for LTLPRE

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