25 research outputs found
Effect of rake angle and cutting speed on energy demands of mulcher with vertical axis of rotation
ArticleThe contribution deals with the reduction of agriculture energy demands. For
maintenance and treatment of permanent grassland areas, areas left fallow and put to rest the
mulching in combination with other workflows (mowing, grazing) is advantageous procedure.
As conventional impact grass cutting and chopping is energy demanding procedure, it is proper
to reduce the energy demands of such device. In the paper the effect of shape of cutting tool,
particularly the rake angle, on energy demands of mulcher with vertical axis of rotation is studied.
The effect of cutting speed on energy demands is also verified. The measurement was performed
using mulcher MZ 6000 made by Bednar FMT Ltd. with working width of 6 m and three rotors.
During the measurement the test rides using the cutting tools with different rake angle and cutting
speeds of 105m s-1
, 89 m s-1
and 79 m s-1 were performed. The rake angle of cutting tools were
chosen 0°, 15° and 25°. The test area was pasture with permanent grassland. During the
measurement the torque and power, transferred through PTO to the machine, fuel consumption
and GPS coordinates were measured. From each test ride the samples of grass matter were taken
in order to determine the yield and moisture content. It was found that increase of the rake angle
up to 25° and decrease of the cutting speed resulted in decrease of the power requirement of the
mulcher
The operational parameters and emissions of portable generator after long-term operation on n-butanol
ArticleThe utilization of biofuels in spark ignition and compression ignition engines is the
trend of the recent time. The great expectations are inserted into n
-
butanol as a fuel, especially
for spark ignition engines. The short time use
of n
-
butanol in the SI (spark ignition) combustion
engine does not make a big problem (start of the cold engine, change of the air
-
fuel ratio). The
purpose of this contribution is the effect of long
-
term use of n
-
butanol as a fuel for SI engine. For
this
purpose the small portable generator was used. The harmful emissions, fuel consumption and
power of the generator was measured then the generator was operated for 300 hours on 100%
n
-
butanol with 80% of nominal load and the measurement was repeated. The g
enerator was
loaded with adjustable electrical resistance. As a reference fuel the petrol BA 95 with no bio
-
component was used. During the operation on n
-
butanol no technical problems occurred with the
generator. After 300 hours of operation on n
-
butanol t
he performance parameters slightly
decreased with little impact on production of harmful emissions components
Effect of long-term operation of combustion engine running on n-butanol – rapeseed oil – diesel fuel blend
ArticleThe short time use of biofuels in compression ignition engines is being studied by
many authors. However, in many cases the real long–term operation of the engine on biofuels
may cause problems. The article deals with the operation parameters of the combustion engine,
fuelled by n-butanol – rapeseed oil – diesel fuel blend, during 70 hours operation in total. Two
brand new diesel power generators Kipor KDE 6500 with output power of 4.6 kW were used for
certain testing. The first generator was operated on 100% diesel fuel and it was used as a reference
and the second generator was operated on experimental fuel containing 10% n-butanol – 20%
rapeseed oil – 70% diesel fuel blend. The generators were equipped with single cylinder
compression ignition engine Kipor KM 186 with the rated power of 5.7 kW. For the first 10
operating hours approx. 40% load was applied. Then, the generators worked for another 60
operating hours with approx. 70% load. The harmful emissions, smoke, fuel consumption and the
amount of produced particles were also measured after 10 hours run-in period and then after
another 60 hours of operation. Consequently, the results were compared. Measurements were
carried out at gradually increasing electric power output, approx. 14%, 28%, 42%, 56%, 68%,
82% and 95% (in results can be found in Watts). Emission analyser and opacimeter BrainBee and
Engine Exhaust Particle Sizer TSI were used for the measurements. The results showed increased
production of emission of the engine running on fuel blend after 70 hours of operation. On the
other hand, engine which operated on standard diesel reached lower fuel consumption. After 70
hours the blended fuel tended to produce more particles in comparison with diesel fuel
Influence of shape of cutting tool on pressure conditions in workspace of mulcher with vertical axis of rotation
ArticleNowadays there is laid great insistence on work efficiency improvement. This effort
also affects the construction of mowers such as mulchers. Mulching with a vertical axis of rotation
is very energy demanding work operation mainly, due to high energy losses. These energy losses,
but also the quality of work, are influenced by the airflow and associated conditions of pressure
inside the workspace of mulcher. Airflow in the workspace ensures repetitious contact of the
truncated forage crops with the cutting edge tool and thus ensures crushing of aboveground parts
of plants. The paper deals with the influence of the cutting tool shape on the mulcher’s inside
workspace pressure conditions with the vertical axis of rotation. The influence of the trailing edge
angle and rake angle on the pressure profile in the mulcher’s workspace with dependence on the
rotor speed was examined. Measurements were performed on a laboratory single rotor mulcher
model. It was found that in the mulcher’s workspace the vacuum is formed by virtue of the rotary
movement of the cutting tools wherein the vacuum increases with rotor speed. The maximum
measured vacuum was about 2.4 kPa and from the centre of the rotor towards its circumference
almost linearly decreases. Furthermore, it was found that with decreasing trailing edge angle and
with increasing rake angle the maximum vacuum decreases. When reducing the angle of the
trailing edge from 45° to 25° led to reduction of vacuum of about 0.3 kPa (12.6%)
Comparison of mechanical and electric drive of mulcher
ArticleThe contribution is focused on comparison of mechanical and electric drive of mulcher
with vertical axis of rotation by means of mathematical model. The mulcher has working width
of 6 m and it is usually aggregated with tractor of minimal power of 150 kW. On the test plot the
torque and power transferred trough the tractor PTO, fuel consumption and the production of
gaseous emissions components were monitored. This field measurement served as a basis for
modelling as well as measured complete characteristics of the combustion engine of the tractor
John Deere 7930. As a main base for the modelling the record of real operation of the tractor with
mulcher was used. Then, in the software product MathCad the operation of the tractor with
mechanical and electrical drive of the mulcher was modelled. In the case of the electrical drive
of the mulcher the tractor with internal combustion engine, connected to generator was taken into
consideration. Due to overall lower efficiency of the electrical drive with generator, worse values
of the fuel consumption and emissions production in comparison with mechanical drive were
reached in case of electric drive. At hypothetical use of batteries (100% electro-powered tractor)
and when the energy mix at Czech Republic is taken into consideration, it is possible to reach the
quarter values of emissions production in comparison with combustion engine
Combustion characteristics of compression ignition engine operating on rapeseed oil-diesel fuel blends
ArticleThe effect of biofuels on the operational parameters of the combustion engines, such
as performance parameters or emission production, are monitored often. These changes are,
however, based on the effect of biofuels on the course of combustion pressure inside the
combustion chamber. The contribution deals with the effect of rapeseed oil-diesel fuel blends on
the combustion characteristics of turbocharged compression ignition engine. The course of
cylinder pressure was monitored and analysed and heat release rate was calculated. The brake
specific fuel consumption, indicated and brake thermal efficiency were calculated and evaluated,
in-cylinder temperature and ignition delay were also evaluated. As a test fuels a 5% and 20%
concentrations of rapeseed oil in diesel fuel were selected while 100% diesel fuel was used as a
reference. Turbocharged CI engine Zetor 1204 located in the tractor Zetor Forterra 8642 was used
for measurement. During measurement the rotation speed of the engine was kept constant at
approx. 1950 min-1
and the load of the engine was selected at approx. 20, 60, 80 and 100%. The
results showed decreased cylinder peak pressure, decreased intensity of heat release rate and
earlier end of combustion in all tested loads for both tested fuel blends in comparison with diesel
fuel, while the lowest peak cylinder pressure was reached using fuel with 5% rapeseed oil. Fuel
with 5% rapeseed oil also showed highest indicated efficiency. Ignition delay was found shorter
with both of the blended fuels in comparison with diesel fuel
Effect of sunflower and rapeseed oil on production of solid particles and performance of diesel engine
ArticleThe development of biofuels for compression ignition engines is heading primarily to
utilization of vegetable oils.
Combusting of 100% vegetable oil in unmodified CI engine is
usually not possible due to higher viscosity of the vegetable oil. In order to use 100% vegetable
oil in CI engine the oil needs to be preheated, esterified or hydrotreated. Alternatively, in orde
r
to use raw vegetable oil in CI engine without preheating it is possible to use vegetable oil
–
diesel
fuel blends or vegetable oil
–
butanol
–
diesel fuel blends in order to lower the viscosity of the
fuel. The contribution focuses on comparison of the e
ffect of sunflower and rapeseed vegetable
oils on operational parameters of the turbocharged compression ignition engine, especially on
production of solid particles.
The measurement was carried out according to standardized NRSC
test cycle. 5% and 20% con
centration of vegetable oils in diesel fuel were used as a test fuels for
the measurement while the diesel fuel was used as a reference. The count and size of solid
particles were measured by means of EEPS particle analyser. Based on the measured values it
can be stated that the slight increase of performance parameters occurred with strong effect on
emissions production, especially on production of solid particles
Air flow conditions in workspace of mulcher
ArticleCurrently, there has been a great effort on increasing the efficiency of agricultural
machinery. The energy demands of mulching with the
vertical
axis of rotation
depends
on the
amount
of pr
ocessed material per unit of time, its properties and efficiency of material processing.
Another
important
factor that is affecting the overall energy demands is the energy losses, which
can be even higher than energy, required
for
the processing of materi
al.
The efficiency
of the
material processing and the energy losses
are influenced
to a large extent by the air flow inside
the mulcher workspace, which
is created
by the movement of working tools. The air flow ensures
the repeated contact of the processed
material with the working tools, affects the energy losses
and the quality of work. The contribution deals with the air flow conditions inside the workspace
of mulcher with the
vertical
axis of rotation. The velocity of the
air flow
was measured
my
means
of LDA (Laser Doppler Anemometry) method in three planes above the surface (180, 100 and
20
mm
) and
in
two directions (peripheral and radial). The laboratory model of one mulcher rotor
from mulcher MZ 6000 made by BEDNAR Ltd. company
was used
for the measu
rement. From
the
results
it is evident that the maximum values of peripheral velocity of the air flow reach
approx. 50% of the velocity of the tools. In the radial
plane
an air vortex is created between 20
and 100
mm
planes above the surface around the tip
of the blade
Features of adenosine metabolism of mouse heart
Adenosine metabolism and transport were evaluated in the isolated perfused mouse heart and compared with the well-established model of isolated perfused guinea pig heart. Coronary venous release of adenosine under well-oxygenated conditions in the mouse exceeds that in the guinea pig threefold when related to tissue mass. Total myocardial adenosine production rate under this condition was approximately 2 nmol/min per gramme and similar in both species. Coronary resistance vessels of mice are highly sensitive to exogenous adenosine, and the threshold for adenosine-induced vasodilation is approximately 30 nmol/l. Adenosine membrane transport was largely insensitive to nitrobenzyl-thioinosine (NBTI) in mouse heart, which is in contrast to guinea pig and several other species. This indicates the dominance of NBTI-insensitive transporters in mouse heart. For future studies, the assessment of cytosolic and extracellular adenosine metabolism and its relationship with coronary flow will require the use of more effective membrane transport blockers